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Head studs - A7novice - 01-02-2022
I have had a head stud strip (nut/outside end of stud)
On removing the offending stud from the block, I discovered a previous owner had tapped block to 3/8 bsW not bsF and fitted a stepped stud with 3/8 bsW thread.
I can only find bsf stepped studs for sale. Any suggestions as to the way forward would be very helpful.
RE: Head studs - Stuart Giles - 01-02-2022
Making a stepped stud is a simple job on a lathe. Start with a 3/8" BSW HT bolt. turn the shank down to 5/16" and thread the end 5/16" BSF. If you don't have access to a lathe, a jobbing engineer should be able to do this for you.
The alternative is to Helicoil the block to 3/8" BSF and use a 'off the peg' stepped stud, this would only be my favoured solution if the stud is one in a position with plenty of metal around it.
RE: Head studs - A7novice - 01-02-2022
Unfortunately I don't have access to a lathe, but I agree ,a good solution. Cheers
RE: Head studs - Hedd_Jones - 01-02-2022
To helicoil, you will keed to go bigger than the existing , 3/8 BSW to get back to 3/8 BSF. Which is getting awful big IMO. And youve still got a stepped stud in the block.
A stepped stud can be made on a pillar drill with a file, a saw and a die if you have the patience.
RE: Head studs - A7novice - 02-02-2022
Never thought of use of pillar drill.......Good idea...I will give it a try. Thanks.
RE: Head studs - Hedd_Jones - 02-02-2022
just some tips from someone who does this sort of thing regularly.
Find a long bolt with the necessary thread and a suitable length plain portion.
Bolt grade is probably a touchy subject, particularly if your mad keen for 590lbft (or whatever) on your torque wrench. Or you do the nuts up with the ugga dugga. I'd say you need a decent one rather than one made in 'chinesium'. To be honest a Whit bolt is likely to be decent material in anycase.
I'd lop the head off and put that end in the chuck.
Protect the threads you want to use, I put 2 nuts on locked together. I use these also as a stop for the file. This means you will be able to file all way to the threads without damaging them, and will not end up with any plain bit sitting above the block deck, nor need to slightly east the upper part of the hole.
You need obviously need to file the plain portion to 5/16, I use a shitty old U/S digital caliper as a gauge. Use an existing head stud to set the size. But use what you like.
Filing between the nuts and the chuck may lead to damage to your chuck. I usually leave the bolt over length and use tape to identify the limit you need to file to at the non threaded end.
Use a good sharp file. A flap disk in the grinder is excellent tool for roughing out. Its also quite exciting. Use at your peril. Bear in mind the drill will have a fair bit of slop doing this, and be carefull not to put too much pressure as you don't want to bend the prospective stud. But this is far easier than it sounds. I found a moderate speed best.
And a nice sharp split die with loads of lube to cut the threads. Have it pretty 'open' to cut a nice tight thread. Basically use the head nut as a gauge.
Cut to length at both ends. The flap wheel in the grinder is also excellent at putting a nice pro style chamfer or dome on the top end to match your others. Don't do it in the vice, roll the stud between your fingers against the flap wheel.
Fitting a stepper stud in the block, unless your super anal with your thread lengths on the big end, you will find to set depth you will need to glue it in, rather than do it up till its tight. The proviso of course is you have sufficient thread engagement.
RE: Head studs - Bob Culver - 02-02-2022
With ingenuity much can be done with a drill press and angle grinder but I did not dare suggest....
Most find it difficult to cut threads square but by hand rotating a drill press whilst very gently feeding can cut dead square.
Similarly in a lathe, where even an unbacked hand held die will cut reasonably square.
Unfortunately most commercial bolts have rolled threads with a taper termination and an immediate reduced dia. Ideally both threads should be cut so the larger one can end abruptly. An old stud out of some other car fine for the material. Not everyone has a BSF die. UNF or M8 not approved, but the cyl head will not know the difference.
RE: Head studs - A7novice - 02-02-2022
Wow that's excellent...very detailed explanation thanks very much. I am tied up until Friday but I will give your method a shot then. Thanks to all folks who offered suggestions, much appreciated.
RE: Head studs - Hedd_Jones - 02-02-2022
Bob, a commerical bolt with a rolled thread will be perfect. Less material to file off!
RE: Head studs - Jeff Taylor - 03-02-2022
If you need the services of a jobbing engineer, I'm sure this guy could help you out - he's in West Worthing PH16. I've never had need to use him, but I have been impressed with the work shown on his Facebook page - link below. He's the guy who manufactures A7 hub spanners.
https://www.facebook.com/Vintagengineer-988426467840657/