Lathe Machining Question

[dgsaz]

Hello all,

This is not a VW question, but the vehicle is air cooled.

I am trying to make a tool to aid in the assembly of the front forks of my 1967 Triumph Tiger Cub.

The Haynes manual recommends "carefully threading a broom hand into the to of the fork leg and guide it up".

This doesn't sit well with me. There is a better way.

I have a large, slightly domed nut. 1 5/16, a spare cap nut that hold the forks to the top of the triple tree.

What I want to do is remove all of the bolts "shoulders" so it can pass into the hole weld to a rod/handle and thread into the fork leg to guide/pull up into the triple tree.

Actually, rather than weld the handle, drill and tap the center for a screw in removable handle.

I can cut a flat spot on the dome for the rod/handle and I suppose I could cut off the "shoulders" with a band saw or cut off wheel and grind it to fit.

But, I have access to a mini lathe and I'm sure the end result would be much cleaner.

How do I approach this?

Bolt in chuck
Center up
Facing tool to cut the flat on the doom.
How do I cut of the shoulders? There's the question

Thanks folks.
dgsaz

[goober]

You didn't say what size bolt/dimensions or mini-lathe you had or it's attachments.

I'd chuck the bolt by the threads into a 3-jaw head-stock chuck. Center it. I'd turn the head and shoulder diameter down to under the minimum thread diameter.

I'd face off the end. With a center drill in a chuck mounted in the tail-stock I'd drill a center. I'd then put an 1/8" drill bit in the tail-stock chuck and drill through or down an 1-1/4" or so into shank. I'd clear the chips frequently from the drill bit.

Depending on what size bolt/threaded rod I was using for the handle I'd work my way up to it's tap drill size. With the lathe OFF and a tap in the tail-stock chuck, by HAND using the chuck I'd slowly rock/bring the part and tap together until I cut my thread to depth frequently clearing chips.

I'd thread in my handle/bolt with nut into the shank and lock it down.

Whenever necessary I'd use a heavy oil as a lubricant. Not sure but I think this is what you're wanting to do.

[dgsaz]

Wow, thanks for that information extravazada. I understand everything except:

I'd turn the head and shoulder diameter down to under the minimum thread
diameter.

The nut is perhaps Imperial threads. I count 27 TPI. I used an SAE 1 5/16" socket to remove the bolt. The threaded shaft is 1 1/16 in diameter.

How does the tool approach the bolt head? The head obviously isn't round so until all the corners are knocked off.

Do I approach from the side and have a click click click engagement until it's round? Is that intermittent striking OK? Small slow passes until it's round?

Thanks again and let me know about the approach. The side approach makes sense but it makes me nervous.

Don Scott

[finster]

seems like a lot of faff to me. I assume the broom handle is an interference fit in the fork leg tube but not so wedged in that you cannot remove it. so I'm wondering if a rubber bung, on the end of a smaller diameter tube, compressed by a long bolt (and washer) running through it so that it grips inside the leg tube would work...

other than that I can't imagine the turning tool liking the shoulders so you would have to cut and file them off first
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[goober]

"Do I approach from the side and have a click click click engagement until it's round? Is that intermittent striking OK? Small slow passes until it's round?"

Yes, but I'd go straight in on the hex. I have an old 6" Sears/Atlas lathe. I'd start by taking very light straight-in cuts until it's turning round. I'd take the head/shoulder diameter to and below the thread diameter. This way I could screw the whole thing through a nut. I think this is what you want.

But only you know how sturdy/rugged your lathe is and how much it can take. If you're taking too much off at a time you'll know it. Feed it across slowly by hand. I've never had a mini-lathe. I'd have no problem turning this with mine.

But if you feel you're being too abusive to your lathe, grind the corners off the head on a grinder. Grind the head as true and round as possible then return to the lathe.

[mark tucker]

take the forks off and stick it in. Ive never had any tripple tree issues other than tight forks being a booger to get out and not wanting to eff any thing up.I always try to do small assemblys rather than a big one, less shit to flop over on my foot. with that said Ive never effed with a triumph. witch remindes me I do have a new set of forks for my 79 yz 250 sitting in the shop waiting for me to work on it...in my spar time...fenders too...new pipe also...new 12 years ago..made rong...DG shit.dont fit&missing the gasket seat,fucking morons.

[dgsaz]

Hey Mark,

You know the answer to this. How do I machine this part?

I followed your advice (to the degree it can be) on my ratio rocker geometry and my valve train sounds better than my 912.

Cough up the wisdom.

dgsaz

[mark tucker]

put the nut in the lathe and cut off the flats, then drill a hile then tasp the hole..there yer done. if your woried sbout effing up the threads clamping it in the lathe, make a nut for it...or... use a peice of pvc pipe that it will slide into snugly slive the pvc on r sides and clamp the pve witch clamps the threads protecting them. machine some off the flats then retighten the chuck if needed. this shoud be a simple job. even thin wall steel pipe could do the job but I would use the pvc method. it's easyer to cut and will form into the threads.. theres my wizdumb...beware of the hairballs.

[dgsaz]

That's the stuff I was looking for.

I was at the shop yesterday and took a shot of the nut and of the nut sitting in the chuck. The first thing I thought is "I don't like the looks of that''. I need to find some nylon inserts like what I use on my vise to protect soft metals.

The PVC idea is brilliant. I can see it.

Back to the nut/lathe. Chuck it up in the PVC and just start shaving the corners?

I saw a guy on U-tube who put a 3/4" bolt in the chuck and just shave off material until it was round. Slow passes at a slow speed.

Here are some pictures of the set up.

Thanks for the help. dgsaz

[chrisflstf]

Where did you get the rear wheel fixture to secure the bike? Very nice

[dgsaz]

[busdaddy]

Having done things like that in the past and having something bind up or slip and take a big bite out of the threads I'd go at it from the other end. Stuff like that only happens on hard to fins oddball stuff, easy to find hardware store threads always chuck perfectly and never screw up.

I'd chuck it by the hex and bore a hole through it to press fit a good sized rod/bar as the handle, then chuck it by the handle and remove the hex.

If you want the handle removeable you can saw it off close to the nut and sleeve it, or thread it for an extension.
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[dgsaz]

[modok]

You could drill it and START the tap with it in the lathe, then finish tapping in a vice, then cut the head off by other means.
Why does the head need to be cut off perfectly square?

But if you want to do it ALL in the lathe just to experience it, that's fine too.
I would, but I know what I'm doing and I can sharpen my own carbide and my lathe is a lot stronger than that thing.

Brass shimstock or at least two wraps of aluminum beer can shim.
I don't imagine plastic tube is going to have enough stability.

[goober]

After seeing your lathe pic, allowing for your concerns, to make things easier (and if you still want to hear about it)...

I'd grind the head round. I'd chuck the steel part in the head-stock chuck so the head, shoulder and part of the thread is just past the face of the chuck so I could get to it with my lathe tool. I wouldn't worry about clamping directly on the steel threads. As long as I took light cuts and didn't lock-up and spin the part in the chuck there shouldn't be any significant damage to the steel threads.

I'd turn the head, shoulder and part of the thread all below the minimum thread diameter then proceed as above to drill the handle tap hole. I'd drill it slightly larger than tap drill size. It would make tapping easier and since it's only holding a handle my thread wouldn't need to be pretty.

To make tapping easier I'd remove the part and clamp it firmly between two pieces of wood in a vice as modok suggests.

Or...you could drill the hole first, put it on a bolt as others have suggested and turn it that way. What ever way you think is easier. It doesn't have to be pretty.

[mark tucker]

Ive taped lots of stuff in my lathes. easyer that way. you could also chuck the head and frill the shank through and tap it then add bolt/stud & flip it around to machine the head off but most heads are not concentric with the threads but they shuldent matter to you for this. I would do the pvc method or soft aluminum to "make soft jaws" . Ive removed lots of bolt heads or cut them back some. not that hard to do as long as you know your speed and feed and where & how your cutting it.I cant tell you that, you have to figure out what works for you and your lathe.thus check to be sure the part is tight in the chuck often. and don't beat the lathe to death..

[dgsaz]

Thanks everyone.

I'm off to Phoenix to watch some Barrett Jackson.

I'll report on my progress upon return.

dgsaz

[nsracing]

What is so hard about assembling a triple tree?

[dgsaz]

[dgsaz]

Going back to the fork assembly.

Here are the directions from the Haynes manual. Note #4, of the Front Forks reassembly. I'm sure this will work. But I like my approach better.

dgsaz