bolt stripping issue

[curtis rosche]

my lathe doesnt have the fancy cam locks like most of your lathes do to hold down the tailstock or toolrest. mine has a bolt and nut andyou have to tighten it with a wrench. well, so far i have gone through about 5 bolts. stripped them. 2 on the toolrest and 3 on the tailstock. the last time i bought bolts i got the stainless steel ones figuring that they would be harder to strip. well, the one on the toolrest has lasted, but the one on the tailstock just stripped. the stainless steel bolt just made it even harder to cut off. i try not to over tighten the bolts, but over time they just slowly strip. is there a special bolt out there somewhere that wont strip? or like a nut that pops off before it strips? i was in the middle of drilling out a weed pot and i was moving my tailstoke closer and suddenly it just wouldnt turn.:mad::mad::mad:

[Nate Carey]

Curtis, try this...

http://www.boltscience.com/pages/faq.htm

[curtis rosche]

so from what that site says, i should spray some wd40 on my bolts everyonce in a while? are stainless steal bolts that much stronger than regular bolts? i am using a 3/8x3'' bolt

[Nate Carey]

...stainless isn't particularly strong...its purpose is to be "stainless"...
...try fine thread bolts, maybe these won't be so prone to backing off...

[Dale Miner]

Curtis,

Stainless fasteners are generally not recommended for applications that require repeated tightening. Stainless has a tendency to gall and actually is not as hard as a quality steel fastener.

I suggest that you use a 'grade 8' bolt and nut, or better yet, a 'grade 8' bolt, and a brass nut. It is probably a good idea to use a box end wrench for the nut, especially if using a brass nut. A good automotive supply house should have 'grade 8' fasteners. The head of a 'grade 8' bolt will have 6 marks.

Also, a bit of an anti-sieze compound on the threads will greatly help the longevity of the assembly. Anti-sieze is a silver or coppery looking paste. It contains small particles of various materials suspended in a petroleum base. It will gather some dust, but if used sparingly, buildup of dust should not become an issue. In the absence of anti-sieze, an occasional drop of oil on the threads is suggested.

Later,
Dale M

[Steve Mawson]

Agree with Dale on the grade 8 bolts. In agricultural equipment that I used to sell we used very hard bolts in some applications. I would think that the hard bolt will last a long time. Not sure where you are at but try a farm equipment dealer if you cant find them any place else.

[Scott Hackler]

I agree, get a grade 8 bolt and nut(s). You will not be able to break or strip them, even if you used an 8' cheater bar to tighten them down!

Available in most hardware stores and usually they are identified by a slight yellow hue.

[Scott Conners]

I'm not sure of the mechanics of your lathe, but something to think about is that there will always be a failure point in any mechanical system. Right now it's the bolt's threads. If you upgrade to higher grade bolts, will you risk stripping tapped threads on your equipment? If it's just threading into an easily replaced nut, then by all means upgrade them both and enjoy the longevity.

[Ryan Baker]

I'm with Scott on this one. You don't really say where these bolts go. If it is a through bolt application going into a nut (which is what I think you mean), then yes you could use grade 5 or grade 8 hardened bolt and nut. But if it is going into a threaded part of your lathe, banjo, etc., absolutely do not use hardened bolts. That is your point of failure, and it is much better to strip the bolt than to destroy the casting.

What is actually stripping? Is it the threads of the bolt? The head of the bolt? Stainless is not that hard, but should be plenty hard enough for this job. Sounds like you are applying way too much force. Are the bolts corroding or galling, and that's what's holding things up? You could try some anti-sieze on the threads. Use a box end wrench.

Or maybe adapt your lathe with cam locks...

[curtis rosche]

the bolts go through holes and into a nut. the bolt an nut are completley seperate from the lathe. i use a box end wrench right now to tighten the nuts. the bolt goes through a plate under the bed and then comes up through either the tailstock or the toolrest, then you put the nut on it and tighten.
so a grade 8 bolt cant be stripped? because if i can be stripped, it might happen eventually and then getting it off would be an issue.

[Ryan Baker]

It would take a huge amount of force to strip a grade 8 bolt. It would probably break before stripping. (Grade 8 is almost too far out on the hardness/brittle scale.) But yes, a hardened bolt should work. The regular bolts from the hardware are actually pretty soft metal ... so that may have something to do with your trouble with them. Is it the bolt or the nut that is stripping? Note that the nuts come graded like the bolts -- get a matching grade nut or that will be the weak link.

As I hinted at earlier, your setup is largely the same as the cam lock setups except for the cam bolt itself. It might be worth checking out the replacement parts site for Powermatic or someone. You might be able to find the parts you need to rig up cam locks. Then again, maybe you are happy with it as is ...

[ROY DICK]

Grade 8 nuts and bolts or grade 9.

Roy

[Mike Lipke]

Fastenall will have what you need.

[curtis rosche]

Ryan. it is the threads that strip.

[Rob Cunningham]

Curtis,
If you are constantly stripping the bolts/nuts, then I would say that you are over-tightening them. If you need to tighten them to the point of stripping, perhaps there is something not seating properly or something is twisted. Look at the locking plate and make sure it isn't bent. Just a thought.

[Paul Atkins]

I have to crank the bolt down on my PM 90 to keep the tail stock from moving and it has a 'tall' nut on it so there are lots of threads engaged. If there is room for a long nut, it might be the easiest fix. Also I don't think grade 8 is needed, grade 5 should be plenty tough. Stainless is not going to help either. Lightly sand the shine off the tailstock base to get a bit more grip.

[curtis rosche]

it has the grip, i have never had it slip. the bottom of the ways on my lathe are now machined, they are cast, and they vary by 1/32-1/64 just enough that you can slid the tailstock then all the sudden it wont move and you have to loosen the bolt.

i just have a bad habit of liking things to be very tight. the last time i didnt make the tailstock very tight was at school, that was back when i had that 20 lbs peice of maple come off the lathe, because the tailstock came loose and i was spindle turning the peice.

thanks for the input. i got a harder bolt (which before it was said here, i thought that all bolts were equal unless you paid a bunch of money and ordered it special) and i got a finer thread (which is the opposite of what i thought i needed before i read that cool bolt site) once again thanks for your help everyone.

[Ryan Baker]

The cast bottom of the ways may be part of your problem. When you are trying to tighten down against an uneven surface, you often have to tighten it down a lot more than you otherwise would in order to keep it from slipping. You might consider a little work with a file or grinder to smooth things off a bit.