I have an old Brunswick pool table that I'm restoring. The table is about a hundred years old. The pocket irons are rather strange, in that the threads are something I have never heard of - 5/16-16
No, not 5/16-18 but SIXTEEN.
I got out my handydandy Starrett thread gage and checked and sho nuf,
16 TPI.
I've looked and cannot find any 5/16-16 bolts and am wondering if this is an old standard thread.
Anyway, do any of you have a hint at where I can find something like this ? I need a dozen of them.
The shank that the bolt goes into is .650 diameter and I have thought about drilling and threading to 3/8-24 but the pocket irons are exactly that - iron and I want to maintain as much strength as possible.
IIRC bolts did not become standardized until less than 100 years ago (I read an article about an early 1900's delivery truck, wherein the author had to machine all his own hardware because it wasn't built to any standards).
My suggestion would be to either heli-coil the holes (with all the strength troubles you mentioned), or find a retired or amateur machinist to make some bolts for you. Thread cutting is so easy that given a good lathe even I can do it, so there should be plenty of folk out there who can help you out.
It is certainly possible to machine these but it would cost about what your table is worth in shop time, sadly. That makes it worth your while to really reconsider reusing your old ones. After all, they don't show. You could use a 16 tpi thread file to clean up the external threads, and you could build up a malformed head (carefully) with epoxy or something and file it back to the proper shape, or maybe build it up with brazing material. I don't know what's wrong with them, but it sounds to me like you're going to have to either borrow some time on a lathe and mill (or just a lathe if you can get appropriate hex stock to start with, or you could even use square stock) and turn them yourself. It isn't difficult, but it would be time consuming. Maybe a pro machinist could do it quicker but I bet those dozen bolts would take me 3 full days.
Unfortunately, installing inserts of any kind won't lend to strength, but further weaken what he considers an already marginal piece. It will be only as strong as the larger internal diameter, no different from going to a
3/8" bolt, and perhaps worse.
If the bolts are missing, the only solution may be to make them. If not, re-using the old ones may be necessary. That point was never mentioned, only that he desires replacement bolts.. If they are present, but not attractive, they could easily be improved by carefully deburring them then bead blasting them to improve surface condition. I've often done that when restoring items.
It is not uncommon for industry to use bastard threads for components, although in this case I assume it was based on no standards having been established yet---not so the customer would be held captive when requiring replacement parts.
You may recall that Ted Edwards was quite proud of the bastard ¼" tap he made (and rightly so) to make a missing component for an antique table, as I recall. Same problem. The missing component was not available.
The key here is to start with partially threaded existing
5/16 bolts. Cut off the old threads and thread the remaining shank. This eliminates turning down the hex stock which is pretty time consuming.
Given that it's a pretty coarse (deep) thread form it would take a bit do each one - but unless there is inches of thread on each one, I think I could do all the threading for them in an hour or two, even on my southbend at home. I think a center would be a good idea in the end of them.
Any of the numerous shops with a CNC lathe could turn these out in a few minutes, especially if hex stock is available. Probably cost you a set-up charge and an hour's worth of time.
Many years ago the size of machine screw thread screws used to go all the way to size number 30 if you have access to a really old machinery handbook or equivalent you can get the dimension or if you get stuck e-mail me and i'll look it up for you paul
This is an ideal application for heli-coils. Especially going into iron. Restoration, though is a funny thing. If your objective is to get a properly functioning pool table, then use the heli-coils. However, if this is apt to be some kind of collector item -- i.e., this is to be treated as an antique, then using heli-coils and/or changing the thread pitch would be a no-no for the judges or appraisers.
Right -- the only advantage over the bolt would be that he could stick with a 5/16" fastener.
Good point.
I would like to know when things were standardized, and how quickly it picked up. Since the common ones are SAE sizes I assume that it was after cars got popular, but it would be interesting to know how the standardization diffused.
I don't, but I've been off the list since June waiting for Election Madness to pass off.
Normally if I needed one or two 1/4" threaded holes I'd do it on my lathe -- but my lathe isn't big enough to handle a dinner table either.
I think that depends on what the old ones looked like, and how accurate a job you wanted done. If you want the new ones to look _exactly_ like the old ones (particularly if they had square heads) then you'd just have to bite the bullet and do some real work.
But otherwise it's a good idea -- and you can always turn off the grade markings on the head (or just start with a hardware grade bolt).
All Thanks for all the encouragement. I only have 4 bolts left from the original table. Fortunately these bolts are all hdden from view and there are still so many of these tables left over and around that tho it could be considered an antique, it's not worth the mint. I'm using it for my own enjoyment.
I did some more thinking about the shank and thread and decided to simply open the hole to 5/16 and run a 3/8-16 tap into the hole. As Ted said, it will follow the original threads and should not appreciably weaken the shank. It's not as if it is holding UP the entire table so I think the risk will be minimal tho it is cast iron. I do like the lifetime waranty idea but when I checked, their website was down so I'm leery of any of THEIR lifetime warranties....
I do have a lathe and have cut threads before so this could have been a route for me to go but I simply decided to open and rethread. As I was running the drill bit in, the amount of material coming out asminute. So having drilled one hole and tapped it, I decided to try tap one hole without drilling it.
I ran the tap in and the chips (actually it was more like dust. No, I didn't use any oil) were small so I think the holes may have been a bit oversize for the 5/16 bolts. I tapped all the rest of them without drilling. All went well and I'll be able to put the table back together.
Thanks again for all the advice. I lurk a whole lot more than I post and learna bunch that way.
On another note, wasn't it neat the way kerry got 85% of the popular vote but the programmers who hacked all the computer voting machines made many of those votes show up as for Dubya ! And they fixed it so it was close enough to give some of the kerry people hope of a recount.
And the great thing about it is that there is no way that any of the audtors will _EVER_ be able to figure out how it was done. Fantastic.
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