my own worst enemy-half shaft bolts
- Thread starter jvandyke
- Start date
Black-Tooth
Tony Natoli
Yes indeed... as Hussein pointed out as well from...
his Volvo supplier, they come in several shaft lengths.
Here is a McMaster-Carr link where you can find some examples:
http://www.mcmaster.com/#socket-head-cap-screws/=vv9btj
I see they have warehouses across the US if you are in need... but shipping to you folks is always a pain.
When I said I found different shaft lengths, I didn't necessarily mean I had much of a choice... some were just different. The last time I did this kinda stuff was back in 2006... so I am having difficulty remembering.
his Volvo supplier, they come in several shaft lengths.
Here is a McMaster-Carr link where you can find some examples:
http://www.mcmaster.com/#socket-head-cap-screws/=vv9btj
I see they have warehouses across the US if you are in need... but shipping to you folks is always a pain.
When I said I found different shaft lengths, I didn't necessarily mean I had much of a choice... some were just different. The last time I did this kinda stuff was back in 2006... so I am having difficulty remembering.
jvandyke
True Classic
Got a few 12.8 grade bolts at Home Depot, length was very close (tad shorter) the shoulder was a little shorter too but four of the "old' bolts cleaned up and looked okay, so I cleaned the parts thoroughly, repacked the grease, put some loctite on, torqued 'em up. Checked the other side, those were all loose too. I'm going to check them again after a few runs and when it warms up and plan on redoing all 12 this spring. Car is going to sit again for a few weeks as uber cold returns. It's one thing to get stranded when it's 20-30 degrees and sit and wait for help, it's quite another when it's -10 with a -50 windchill, that's risking death, cell phone or not, I'm crazy but even I have my limits.:eyepop::eyepop:
mid79
Youth Revisited
Had the same thing happen on my '92 Jetta
I built the engine, had the transaxle refreshed, and detailed the engine compartment. Put the whole thing back together (including new CV bolts) and enjoyed driving it for a while.
One day, while heading over to pick up the school carpool, those new CV bolts came out. Left me stranded until son #1 brought the spares and tool kit. It happens.
When the temp is that cold, don't you just put the roof on and turn up the heat?
I built the engine, had the transaxle refreshed, and detailed the engine compartment. Put the whole thing back together (including new CV bolts) and enjoyed driving it for a while.
One day, while heading over to pick up the school carpool, those new CV bolts came out. Left me stranded until son #1 brought the spares and tool kit. It happens.
When the temp is that cold, don't you just put the roof on and turn up the heat?
Sandgroper
True Classic
Seems I swim against the tide
I won't re use CV bolts [ didn't Bernice write something not so long ago on the topic? ]
Perhaps it has something to do with the amount of HP put through the shafts but I have had the LH short shaft completely let go once and come loose a few times with the standard advice. The gouges in my transmission case are a reminder to me every time I do a visual inspection on all the bolts.
Now I just throw the old ones in a bin when changing the grease and O'hauling the CV's.
Being a clean freak helps me get them to stay put and as a similar German system uses 35 pounds for theirs that's my preferred torque number.
McKenzies VW performance list their CVs
45 pounds for cast flanges
55 pounds for billet
However, you are safe with 35 pounds on the X
I may be way wrong but my understanding was that the drive isn't from shear on the bolts themselves. The drive is from the friction between the face of the CV to the mating face of the flange. The friction is created by the tension in the bolts clamping the two parts together, that's 1/2 the reason for the half-moon 2 hole plate washers - to spread the clamping force. You loose that tension and the bolts just shear off. Hopefully Bernice will chime in here and describe it better.
When refitting I start by using can of brake cleaner with its straw to clean out the threads in the hubs & on the transmission for the bolts, also flush the bolt bore on the CVs of the bolts pick up crud when I refit them. It's really important to keep all grease out of the bolt holes and threads or the threadlocker will be useless. I use a threadlocker equivalent to the 'Blue Locktite' with a temp range of -59° to 148°C Break Away Torque Up To 16 NM. I purposely avoided the common Red threadlocker, I think it's described as'Permanent' with a Break Away Torque of about 28 NM from my feeble memory. I put a blob of paint as an indicator on my bolts to CV to see at a glance if they are backing out. For some reason for me the short shaft was the problem child.
If you are going to re-use the cap head bolts [I can't see why as they are so damn inexpensive, but hey you pays your money and you takes your chances]
Using the same solvent, clean all grease residue from the bolts, it may help to soak them in fuel beforehand to remove the bulk of the grease. Apply threadlocker to the threads, and use them to attach your freshly-serviced CV-joints. Use a torque wrench, and secure the bolts. Check your manual for the exact torque, but it should be about 35 Ft-lbs. Be sure to use the torque wrench! If you don't, you run the risk of the bolts working loose and eventually shearing off. If that happens, you will end up "Pushing a rope" (getting towed) back home. I use a Warren & Brown deflecting beam as the torque is so low a click type I can't trust the accuracy.
Be sure to use that brake cleaner and a pick to clean out the cap head screws before trying to remove them. They are prone to stripping the Allen head if the tool used doesn't get seated correctly. My gut feeling as to why they have such a bad reputation in comparison to the ones I prefer
Tripplesquare of otherwise known as XZN
https://en.wikipedia.org/wiki/List_of_screw_drives#Triple_square
To go WWWwwaaay OT
From 1st hand experience I agree about the Type2 bus cv bolts being a problem, the type 4 engine anyway. I ended up using the Stuttgart 914 solution and put in M8 Schnorr washers over the half moon [two hole washer] plates on the bus. The M8 Schnorr (serrated Belleville) washers used in my Kraut driveline you could probably get from McMaster-Carr. But if you have issues finding them the Porsche part number is 999-523-102-02. If I hadn't solved the loosening CV bolt issue on the Fiat I was going down that route with the X but it settled down so never did it.
Franken, these bolts are nothing special and are not related only to Fiat, Metric Grade 12.9 is roughly equivalent to US Grade 9, if you have issue finding a decent bolt shop then
http://shop.x19spares.co.uk/driveshaft-bolts-pkt-6-642-p.asp
These 55mm long bolts have the longer 30mm shank, though strangely the Germans in the 911/914/Kombi have little if any shank at all on their CV bolts.
Oh and not sure if it is myth or not but clean the mating surface between the CV Boot cup and the CV joint, If it is covered in crud the talk was that this contributes to the movement between these two parts. I cleaned mine and put a small smear of Hylomar blue on there to successfully cure a CV grease leak, I have no idea if this helped with curing the loosening CV bolt problem I was having.
If you want to waste a good two hours and read this thread on Pelican Parts [and where it leads] you will come away with a better understanding of the CV Bolt problem from a car with a much higher power output. Our treasured little door stop puts out little by comparison and why I feel we don't have such an issue with the X 1/9.
http://forums.pelicanparts.com/porsche-911-technical-forum/817999-broken-axle-bolts.html
leads here
http://forums.pelicanparts.com/pors...constructing-constant-velocity-cv-joints.html
if you found that interesting at one stage I was so $%^&* frustrated I considered
this
http://stage8.com/importscvjoint.html
bolts are available in 5mm increments, with the D type retainers and snap rings I'd be confident on a race track.
http://store.stage8.com/p/8325-cv-joint-8mm?pp=96&sort_selection=recommended
I won't re use CV bolts [ didn't Bernice write something not so long ago on the topic? ]
Perhaps it has something to do with the amount of HP put through the shafts but I have had the LH short shaft completely let go once and come loose a few times with the standard advice. The gouges in my transmission case are a reminder to me every time I do a visual inspection on all the bolts.
Now I just throw the old ones in a bin when changing the grease and O'hauling the CV's.
Being a clean freak helps me get them to stay put and as a similar German system uses 35 pounds for theirs that's my preferred torque number.
McKenzies VW performance list their CVs
45 pounds for cast flanges
55 pounds for billet
However, you are safe with 35 pounds on the X
I may be way wrong but my understanding was that the drive isn't from shear on the bolts themselves. The drive is from the friction between the face of the CV to the mating face of the flange. The friction is created by the tension in the bolts clamping the two parts together, that's 1/2 the reason for the half-moon 2 hole plate washers - to spread the clamping force. You loose that tension and the bolts just shear off. Hopefully Bernice will chime in here and describe it better.
When refitting I start by using can of brake cleaner with its straw to clean out the threads in the hubs & on the transmission for the bolts, also flush the bolt bore on the CVs of the bolts pick up crud when I refit them. It's really important to keep all grease out of the bolt holes and threads or the threadlocker will be useless. I use a threadlocker equivalent to the 'Blue Locktite' with a temp range of -59° to 148°C Break Away Torque Up To 16 NM. I purposely avoided the common Red threadlocker, I think it's described as'Permanent' with a Break Away Torque of about 28 NM from my feeble memory. I put a blob of paint as an indicator on my bolts to CV to see at a glance if they are backing out. For some reason for me the short shaft was the problem child.
If you are going to re-use the cap head bolts [I can't see why as they are so damn inexpensive, but hey you pays your money and you takes your chances]
Using the same solvent, clean all grease residue from the bolts, it may help to soak them in fuel beforehand to remove the bulk of the grease. Apply threadlocker to the threads, and use them to attach your freshly-serviced CV-joints. Use a torque wrench, and secure the bolts. Check your manual for the exact torque, but it should be about 35 Ft-lbs. Be sure to use the torque wrench! If you don't, you run the risk of the bolts working loose and eventually shearing off. If that happens, you will end up "Pushing a rope" (getting towed) back home. I use a Warren & Brown deflecting beam as the torque is so low a click type I can't trust the accuracy.
Be sure to use that brake cleaner and a pick to clean out the cap head screws before trying to remove them. They are prone to stripping the Allen head if the tool used doesn't get seated correctly. My gut feeling as to why they have such a bad reputation in comparison to the ones I prefer
Tripplesquare of otherwise known as XZN
https://en.wikipedia.org/wiki/List_of_screw_drives#Triple_square
To go WWWwwaaay OT
From 1st hand experience I agree about the Type2 bus cv bolts being a problem, the type 4 engine anyway. I ended up using the Stuttgart 914 solution and put in M8 Schnorr washers over the half moon [two hole washer] plates on the bus. The M8 Schnorr (serrated Belleville) washers used in my Kraut driveline you could probably get from McMaster-Carr. But if you have issues finding them the Porsche part number is 999-523-102-02. If I hadn't solved the loosening CV bolt issue on the Fiat I was going down that route with the X but it settled down so never did it.
Franken, these bolts are nothing special and are not related only to Fiat, Metric Grade 12.9 is roughly equivalent to US Grade 9, if you have issue finding a decent bolt shop then
http://shop.x19spares.co.uk/driveshaft-bolts-pkt-6-642-p.asp
These 55mm long bolts have the longer 30mm shank, though strangely the Germans in the 911/914/Kombi have little if any shank at all on their CV bolts.
Oh and not sure if it is myth or not but clean the mating surface between the CV Boot cup and the CV joint, If it is covered in crud the talk was that this contributes to the movement between these two parts. I cleaned mine and put a small smear of Hylomar blue on there to successfully cure a CV grease leak, I have no idea if this helped with curing the loosening CV bolt problem I was having.
If you want to waste a good two hours and read this thread on Pelican Parts [and where it leads] you will come away with a better understanding of the CV Bolt problem from a car with a much higher power output. Our treasured little door stop puts out little by comparison and why I feel we don't have such an issue with the X 1/9.
http://forums.pelicanparts.com/porsche-911-technical-forum/817999-broken-axle-bolts.html
leads here
http://forums.pelicanparts.com/pors...constructing-constant-velocity-cv-joints.html
if you found that interesting at one stage I was so $%^&* frustrated I considered
this
http://stage8.com/importscvjoint.html
bolts are available in 5mm increments, with the D type retainers and snap rings I'd be confident on a race track.
http://store.stage8.com/p/8325-cv-joint-8mm?pp=96&sort_selection=recommended
jvandyke
True Classic
ouch, my axle seemed to rest on the A arm and there's only a very light line on it where it rubbed. I didn't see anything on the case and I did clean it up so I think I would have. Car only went a couple hundred feet this way, down a minor grade (thank the Lord) into parking lot. Lucky it was not a busy time of day. It's one of the busiest streets in the city and I had to push it around the corner and down the "hill" and jump in and pray it had enough steam to reach the lot. At night. In the winter.
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Sandgroper
True Classic
Yes Jeff you can consider yourself fortunate it let go when moving off the line from a traffic light. The very nature of the open differential saved your bacon. When the loose drive shaft flange spins freely the connected side just remains stopped. It probably only had a few bolts in there and flicked the case once when you went to get moving again, rather than flailing around like a crazy snake.
I was also lucky as I was in the outer lane of a 4 lane freeway doing 100 km/h [60]. I knew it wasn't a rod as soon as I depressed the clutch and winced at the racket it made as I nudged [ barged] my way across traffic to the curb and a stop in the emergency lane. I don't know whether to be grateful that it was the short side as the suspension A arm indeed held the shaft up when it let go of the flange at the tranny. Gouged my trans axle case but nowhere near as bad as the images kindly posted by Mathew above. [ nice weld penetration BTW ]
For me the result of catastrophic failure far outweighs the cost of some inexpensive bolts. The 5 speed is not plentiful Downunder.
I re read your OP and if these CV bolts have come loose before you may have over stretched them. Toss them out.
From my little black book on fixing hardware the M8 bolts at that hardness go to 31/32 pounds before they get past their recommended torque. If you have done what some in the VW community had done and just tightened the heck out of them with a bar you can easily get to ~ 50 pounds where they are reaching the point where they are past their stretch to yield point. = they're toast.
I was considering going to M10 as that small 2mm difference is actually double the standard Fiat fitting at a recommended bolt torque at ~60 pounds.
Pay particular attention to the CV mounting to flange & cup faces and ensure they are clean. Those half moon washers actually do more than two things they also resist spinning as they hold onto two CV bolts and this helps the bolt/washer stay put. The hardness of the washers resist the deformation that are a given with the relatively soft cups holding the boots on. Without them all that force under where the bolt seats probably just squishes under the bolt contact face of the cup and there goes the bolt tension. A little dab of bright paint with a modelers fine brush works well to indicate if they are backing out.
Sandy
I was also lucky as I was in the outer lane of a 4 lane freeway doing 100 km/h [60]. I knew it wasn't a rod as soon as I depressed the clutch and winced at the racket it made as I nudged [ barged] my way across traffic to the curb and a stop in the emergency lane. I don't know whether to be grateful that it was the short side as the suspension A arm indeed held the shaft up when it let go of the flange at the tranny. Gouged my trans axle case but nowhere near as bad as the images kindly posted by Mathew above. [ nice weld penetration BTW ]
For me the result of catastrophic failure far outweighs the cost of some inexpensive bolts. The 5 speed is not plentiful Downunder.
I re read your OP and if these CV bolts have come loose before you may have over stretched them. Toss them out.
From my little black book on fixing hardware the M8 bolts at that hardness go to 31/32 pounds before they get past their recommended torque. If you have done what some in the VW community had done and just tightened the heck out of them with a bar you can easily get to ~ 50 pounds where they are reaching the point where they are past their stretch to yield point. = they're toast.
I was considering going to M10 as that small 2mm difference is actually double the standard Fiat fitting at a recommended bolt torque at ~60 pounds.
Pay particular attention to the CV mounting to flange & cup faces and ensure they are clean. Those half moon washers actually do more than two things they also resist spinning as they hold onto two CV bolts and this helps the bolt/washer stay put. The hardness of the washers resist the deformation that are a given with the relatively soft cups holding the boots on. Without them all that force under where the bolt seats probably just squishes under the bolt contact face of the cup and there goes the bolt tension. A little dab of bright paint with a modelers fine brush works well to indicate if they are backing out.
Sandy
lookforjoe
True Classic
6K holeshots at the drag strip (not a good move on my part, not knowing how to launch properly) exploded my angle drive AND snapped my left axle in two. Did not damage the 6 cv bolts that I reused several times ...
Only around 350AWHP back then, 50/50 torque split
Only around 350AWHP back then, 50/50 torque split
jvandyke
True Classic
I think in my case it was a very slow process, they loosened up one by one and it may be I was driving around at the last point with one barely holding and one doing all the work, the other 4 having back out, one last clutch release (which was very gentle, as I pulled up to the light after the guy ahead of me turned right on a red, which I was about to do, it was as I nudged up in line that it went, probably the second to last bolt gave it up and the last one snapped. Pretty gentle failure. I almost tried to fix it in the lot but not knowing the extent of the damage, the condition of the bolts or having a means of jacking up the car and cleaning everything up and then a white knuckle 20 mile drive in the winter night and knowing I have 10 miles free towing, just had to pay the difference, that's a no brainer! I called the calvary.
I will get a new set of bolts and redo them all this spring.
I will get a new set of bolts and redo them all this spring.
Rupunzell
Bernice Loui
I've harped and crowed and written a LOT over the years about CV joint screws. ALL cv joint to drive flange connections that are done with threaded drive flanged WILL loosen. This has been observed in everything from Fiat to various race cars that use threaded cv joint flanges REGARDLESS of brand and fastener type.
In the LeMons racer, the cv screws are checked after the end of each race day and the cv screws at lease one ALWAYS loose. This has been true when it the car was being raced with the stock engine to this day when it is using a Porsche 901 gear box (which has been worst for loose cv joint screws than the stock Fiat gear box). The Porsche 901 transaxle used in the Porsche 914 uses two large dowel pins to locate the CV joint on to the drive flange, four M8x1.25 socket head screw for tension and a cork/rubber gasket to reduce grease leakage. The idea was those two dowel pin would locate and prevent any movement of the CV joint under load with the four screws providing tension to hold it all together... In reality the tolerances involve and the fact metal acts more like rubber than a solid results in loose screws.
The outer drive flanges are Lancia Scorpion/MonteCarlo with MS21250 bolts, countersink washers and 12 point prevailing torque nuts. These have NEVER worked loose in all the years and LeMons racing since they were installed. The joint is torqued to 25-27 ft/lb as specified for MS21250 bolts per the Mil Spec drawing.
For M8 grade 12.9 cap screws torqued to 25-30 ft/lb, the resulting clamp load is about 5,000 to 7,000 pounds for each fastener. six of these results in a total clamp load about 30,000 to 42,000 pounds per cv joint which appear to be plenty... except lubricant migrates between the joint reducing fiction (grip between surfaces), then adding shock loads and load reversals which deform the metals involved causing the joint to move. Once the joint has moved, it is pretty much game over for joint pre-load and it is well on it's way to loose fasteners and joint failure.
This fact and reality hold true for ALL threaded drive flange to cv joint connections.
Exceeding 31 ft/lbs on a M8 grade 12.9 cap screw will cause it to stretch and fail. Going up one thread diameter does help except there is not quite enough material on the drive flanges to do this.
"Split lock washers" will do squat to aid this problem. Hardened tooth conical washers help a tiny bit, loctite is out of the question due to lubricant contamination and this does not address the joint flexure problem. The straps that locate two screws are designed to provide a buffer between the soft metal cv boot flange and grade 12.9 cap screw which will seriously dig into the boot flange if not used causing a threaded joint failure.
The proper solution is use a bolt/nut/washer joint system with tight tolerances or do what the industry has already done in most current cv joint vehicles, go to a splined drive connection with snap rings to hold them in place. The reason why the industry went to this system is to rid the problem of loose cv joint threaded fasteners and lower cost with much greater joint reliability.
My never ending gripe about these cap screws and threaded hardware in general, these M8x1.25-45mm, grade 12.9 socket head cap screws are very, very common and cost about $0.25 each and less for over 100pc. Yet, the resistance to replacing them and using new ones each time the cv joints are serviced is extreme. Given the serious problems and damage a flying axle can cause, why is all this resistance and insistence on re-using these cap screws so very deeply ingrained?
On the LeMons racer, we cycle these cv joint cap screws like fuel as the slightest risk of a axle joint failure is simply NOT acceptable.
Oh, just because launching the vehicle causing the final drive gears to fail and no re-used cv joint screws to fail means little. That gear set could have easily had a crack or stress riser that resulted in that failure. It is also worth noting that a forward launch of the vehicle produces directional stress on the drive line. It is very different for a vehicle that is road course races were load reversals happen at nearly every moment the vehicle is on track. This essentially rocks the drive line forward-backwards causing a very different type of stress on the entire driver line than just going forward.
Bernice
In the LeMons racer, the cv screws are checked after the end of each race day and the cv screws at lease one ALWAYS loose. This has been true when it the car was being raced with the stock engine to this day when it is using a Porsche 901 gear box (which has been worst for loose cv joint screws than the stock Fiat gear box). The Porsche 901 transaxle used in the Porsche 914 uses two large dowel pins to locate the CV joint on to the drive flange, four M8x1.25 socket head screw for tension and a cork/rubber gasket to reduce grease leakage. The idea was those two dowel pin would locate and prevent any movement of the CV joint under load with the four screws providing tension to hold it all together... In reality the tolerances involve and the fact metal acts more like rubber than a solid results in loose screws.
The outer drive flanges are Lancia Scorpion/MonteCarlo with MS21250 bolts, countersink washers and 12 point prevailing torque nuts. These have NEVER worked loose in all the years and LeMons racing since they were installed. The joint is torqued to 25-27 ft/lb as specified for MS21250 bolts per the Mil Spec drawing.
For M8 grade 12.9 cap screws torqued to 25-30 ft/lb, the resulting clamp load is about 5,000 to 7,000 pounds for each fastener. six of these results in a total clamp load about 30,000 to 42,000 pounds per cv joint which appear to be plenty... except lubricant migrates between the joint reducing fiction (grip between surfaces), then adding shock loads and load reversals which deform the metals involved causing the joint to move. Once the joint has moved, it is pretty much game over for joint pre-load and it is well on it's way to loose fasteners and joint failure.
This fact and reality hold true for ALL threaded drive flange to cv joint connections.
Exceeding 31 ft/lbs on a M8 grade 12.9 cap screw will cause it to stretch and fail. Going up one thread diameter does help except there is not quite enough material on the drive flanges to do this.
"Split lock washers" will do squat to aid this problem. Hardened tooth conical washers help a tiny bit, loctite is out of the question due to lubricant contamination and this does not address the joint flexure problem. The straps that locate two screws are designed to provide a buffer between the soft metal cv boot flange and grade 12.9 cap screw which will seriously dig into the boot flange if not used causing a threaded joint failure.
The proper solution is use a bolt/nut/washer joint system with tight tolerances or do what the industry has already done in most current cv joint vehicles, go to a splined drive connection with snap rings to hold them in place. The reason why the industry went to this system is to rid the problem of loose cv joint threaded fasteners and lower cost with much greater joint reliability.
My never ending gripe about these cap screws and threaded hardware in general, these M8x1.25-45mm, grade 12.9 socket head cap screws are very, very common and cost about $0.25 each and less for over 100pc. Yet, the resistance to replacing them and using new ones each time the cv joints are serviced is extreme. Given the serious problems and damage a flying axle can cause, why is all this resistance and insistence on re-using these cap screws so very deeply ingrained?
On the LeMons racer, we cycle these cv joint cap screws like fuel as the slightest risk of a axle joint failure is simply NOT acceptable.
Oh, just because launching the vehicle causing the final drive gears to fail and no re-used cv joint screws to fail means little. That gear set could have easily had a crack or stress riser that resulted in that failure. It is also worth noting that a forward launch of the vehicle produces directional stress on the drive line. It is very different for a vehicle that is road course races were load reversals happen at nearly every moment the vehicle is on track. This essentially rocks the drive line forward-backwards causing a very different type of stress on the entire driver line than just going forward.
Bernice
Sandgroper
True Classic
Many thanks for that Bernice. I really should trawl though the old posts and re read what you wrote.
That figure clashes with some of the literature out of Stuttgart for their own applications so I looked around and 31 listed by Fiat seemed on the low side. Not unusual for automotive books to rate different figures for the same fitting.:confuse2:
I understood that grade 12.9 went to 47Mn / 35 lb-ft before load is reaching 100% proof. If I'm over torquing these - my bad [ but it seems to work]
http://gluclowcara.blog.com/2014/10/08/metric-bolt-torque-chart/
Could you please point me to some material that discusses lubricant ingress on a threadlocked fitting. If I am wasting my time with that step I would like to understand the mechanics of why it fails.
Finally, any thoughts on that Stage8 locking system?
Looks interesting but damn expensive for what it is, if I can cure the loosening CV bolt issue I'd be a happy camper as the lumps of metal that comes with a turbo charger makes access to damn bolts from anywhere except underneath a PITA . I see teardrop shaped indicator tabs on heavy haulage wheel nuts all the time that indicate at a glance a nut backing off, I always wondered if there was a reason they didn't try and lock them in like the Stage8 method. Like a novice I just guessed that there was a preference to a backed off nut versus a snapped wheel stud and why the stage8 offering was not very common. That coupled with seeing these in stainless [ which can in no way be 12.9 ] on many chrome hot rod rocker covers etc I thought they may be more hype [ gimmick ] than a serious solution.
Cheers Sandy
That figure clashes with some of the literature out of Stuttgart for their own applications so I looked around and 31 listed by Fiat seemed on the low side. Not unusual for automotive books to rate different figures for the same fitting.:confuse2:
I understood that grade 12.9 went to 47Mn / 35 lb-ft before load is reaching 100% proof. If I'm over torquing these - my bad [ but it seems to work]
http://gluclowcara.blog.com/2014/10/08/metric-bolt-torque-chart/
Could you please point me to some material that discusses lubricant ingress on a threadlocked fitting. If I am wasting my time with that step I would like to understand the mechanics of why it fails.
Finally, any thoughts on that Stage8 locking system?
Looks interesting but damn expensive for what it is, if I can cure the loosening CV bolt issue I'd be a happy camper as the lumps of metal that comes with a turbo charger makes access to damn bolts from anywhere except underneath a PITA . I see teardrop shaped indicator tabs on heavy haulage wheel nuts all the time that indicate at a glance a nut backing off, I always wondered if there was a reason they didn't try and lock them in like the Stage8 method. Like a novice I just guessed that there was a preference to a backed off nut versus a snapped wheel stud and why the stage8 offering was not very common. That coupled with seeing these in stainless [ which can in no way be 12.9 ] on many chrome hot rod rocker covers etc I thought they may be more hype [ gimmick ] than a serious solution.
Cheers Sandy
Dallarax19
Builder -Dallara Replica
Jeff you know I am to the point
http://www.harborfreight.com/9-inch-safety-wire-twisting-pliers-45341.html
The only solution to this problem I know of is safety wiring. It it a bit tedious but they will never come loose. Simple remove, drill hole in side of head, replace, torque, wire up and done. Never a problem on the track or street since I did the change to mine. BTW I use the original bolts that came with the car in 1979. No issues.
http://www.harborfreight.com/9-inch-safety-wire-twisting-pliers-45341.html
The only solution to this problem I know of is safety wiring. It it a bit tedious but they will never come loose. Simple remove, drill hole in side of head, replace, torque, wire up and done. Never a problem on the track or street since I did the change to mine. BTW I use the original bolts that came with the car in 1979. No issues.
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Rupunzell
Bernice Loui
There are a HUGE number of variables that significantly affect actual pre-load applied to any threaded fastener. Friction is one of the main variables. Different lubricants, different platings, different surface finishes and much more all affect actual residual tension loaded on any threaded fastener. For a M8, grade 12.9 socket head cap screw the spec torque can be anywhere from 25 to 31 ft/lbs depending on those previously mentioned factors. Ideally, the threaded fasteners is loaded to near the yield point of the material. In theory, this produced the highest acceptable load on the material before it becomes permanently deformed to a different shape-size and... If the yield point is exceeded, the material will develop micro-cracks which propagate and result in a sudden failure. This is why high strength threaded fasteners must be used with extreme care specific to it's application.
Know commercial/industrial threaded fasteners gain strength by heat treatment, not speciality alloys alone. Grade 12.9 and US 1960 series socket head cap screws are heat treated to have a hard shell with a softer core. This imparts strength while keeping some degree of elasticity to aid with impact and fatigue resistance.
Aerospace specification threaded fasteners play by a different set of rules. Where tensile / shear strength is gained by using specific alloys and very specific heat treatment and tempering. This is done to gain as much fatigue strength as possible and with the threaded fastener bending and flexing a lot before failure. The common garden variety AN bolt has far better fatigue endurance over SAE grade 5 or ISO-DIN grade 8.8 and their cost is nearly identical.
The Stage 8 locking system was originally developed to stop truck lug nuts from falling off. It works, and works very well. They are common on a lot of large commercial trucks and busses here. See them all the time.
If one looks at the hub axle nuts on a Swift DB-1, one finds a design similar to this using a series of offset drilled holes for a socket head cap screw that sits on the axle nut flat once that axle nut has been torqued to spec. One of the drilled & tapped holes will line up to keep that axle nut from coming off, this does not prevent the axle nuts from loosening. It is the actual pre-load that keeps it all together.
It is similar to safety wire on aircraft. This is a FAA requirement for specific locations. Safety wire does not prevent the threaded fasteners from getting loose, it does go a long ways to preventing the threaded fastener from falling out which can end in big drippy tears for all involve. Any thing that has a high liability for threaded fastener failure due to ejection, safety wire should be seriously considered. If bolts or screws are to be safety wired, get them with the holes already drilled as drilling safety wire holes is not much fun at all... and use soft annealed 302 or 304 stainless steel wire specifically designed to be used as safety wire. Most common diameters are 0.020" and 0.032".
http://www.eng-tips.com/faqs.cfm?fid=1549
Bernice
Know commercial/industrial threaded fasteners gain strength by heat treatment, not speciality alloys alone. Grade 12.9 and US 1960 series socket head cap screws are heat treated to have a hard shell with a softer core. This imparts strength while keeping some degree of elasticity to aid with impact and fatigue resistance.
Aerospace specification threaded fasteners play by a different set of rules. Where tensile / shear strength is gained by using specific alloys and very specific heat treatment and tempering. This is done to gain as much fatigue strength as possible and with the threaded fastener bending and flexing a lot before failure. The common garden variety AN bolt has far better fatigue endurance over SAE grade 5 or ISO-DIN grade 8.8 and their cost is nearly identical.
The Stage 8 locking system was originally developed to stop truck lug nuts from falling off. It works, and works very well. They are common on a lot of large commercial trucks and busses here. See them all the time.
If one looks at the hub axle nuts on a Swift DB-1, one finds a design similar to this using a series of offset drilled holes for a socket head cap screw that sits on the axle nut flat once that axle nut has been torqued to spec. One of the drilled & tapped holes will line up to keep that axle nut from coming off, this does not prevent the axle nuts from loosening. It is the actual pre-load that keeps it all together.
It is similar to safety wire on aircraft. This is a FAA requirement for specific locations. Safety wire does not prevent the threaded fasteners from getting loose, it does go a long ways to preventing the threaded fastener from falling out which can end in big drippy tears for all involve. Any thing that has a high liability for threaded fastener failure due to ejection, safety wire should be seriously considered. If bolts or screws are to be safety wired, get them with the holes already drilled as drilling safety wire holes is not much fun at all... and use soft annealed 302 or 304 stainless steel wire specifically designed to be used as safety wire. Most common diameters are 0.020" and 0.032".
http://www.eng-tips.com/faqs.cfm?fid=1549
Bernice
Last edited:
Rupunzell
Bernice Loui
Tab washers are a really, really bad idea.
Consider for a moment, if the tab washer is soft enough be bent without cracking, this material will compress and deform from the clamp load applied by the threaded fastener. This limits the actual clamp load possible for a joint with a tab washer.
The effect is similar to why those hardened strap washers that connect two socket head cap screws on the Fiat and numerous other bolted cv joints found in the moto industry. This is done to spread the clamp load on the soft metal cv boot flange. If those special strap washers are not used or a similar hardened washers is used under the head of the socket head cap screws, the cv boot flange metal will compress and deform once the the cap screws are torqued to spec... they might never reach torque spec due to compression of the metal.
This is the same reason why there is a hardened steel washer between the aluminum cylinder head and cylinder head screw or stud nut. If the hardened washer was not present, the significantly harder threaded fastener will do a LOT of digging into the aluminum resulting a a very poor threaded fastener joint.
Tab washers were very common in british industrial items from years ago. Some of that design ideology transferred to the US, but their problem have resulted in limited applications today and has been replaced with far more reliable retention methods today.
Relic from another era. Best to relegate tab washers to industrial history or be used in very specific applications where the design very specifically needs it. BTW, tabbed washers are used on the Mazda rotary oil pump along with split lock washers and all that mechanical design ideology from that era. Tabbed washers are also used in the Triumph engine connecting rods and main bearing bolts and nuts. They get away with it due to the way over sized thread diameters and low torque values for these given thread diameters.
Bernice
Consider for a moment, if the tab washer is soft enough be bent without cracking, this material will compress and deform from the clamp load applied by the threaded fastener. This limits the actual clamp load possible for a joint with a tab washer.
The effect is similar to why those hardened strap washers that connect two socket head cap screws on the Fiat and numerous other bolted cv joints found in the moto industry. This is done to spread the clamp load on the soft metal cv boot flange. If those special strap washers are not used or a similar hardened washers is used under the head of the socket head cap screws, the cv boot flange metal will compress and deform once the the cap screws are torqued to spec... they might never reach torque spec due to compression of the metal.
This is the same reason why there is a hardened steel washer between the aluminum cylinder head and cylinder head screw or stud nut. If the hardened washer was not present, the significantly harder threaded fastener will do a LOT of digging into the aluminum resulting a a very poor threaded fastener joint.
Tab washers were very common in british industrial items from years ago. Some of that design ideology transferred to the US, but their problem have resulted in limited applications today and has been replaced with far more reliable retention methods today.
Relic from another era. Best to relegate tab washers to industrial history or be used in very specific applications where the design very specifically needs it. BTW, tabbed washers are used on the Mazda rotary oil pump along with split lock washers and all that mechanical design ideology from that era. Tabbed washers are also used in the Triumph engine connecting rods and main bearing bolts and nuts. They get away with it due to the way over sized thread diameters and low torque values for these given thread diameters.
Bernice
What about fabb'n up something like these? Switch to hex heads.?
