Making Threaded Studs

.

What is the best way to do it.?

If the stud is nice and long I don't see a problem as there is a good length to be able to grip. But what about smaller length ones.

e.g. Say I needed to make a stud a total length of 1/2" with 1/4" in the centre not threaded but a thread on each end of 1/8" - How would this be best done.

Also when threading my split dies leave a taper towards the end of the thread. I can see why the dies are made as such as it gives them a gradual engagement start upon the bar being threaded.

Is there a different kind of die that has the full thread form all the way to the die face that can be used after the original tapered one. Sort of a die version of a 'bottoming tap' (which I always grind the point off anyway)

Cheers, Nick

Nick,

Use a die nut after the normal split die. This will give a parallel thread.

Eric

If you reverse the die it cuts further. I've use it the correct way then remove, clean and use it reversed to cut a bit further. Or buy a die nut as already said.

Ian

Hi Nick,
You could try using the die the wrong way round. (After first cutting the thread with it the correct way.) This idea relies on the being no clearance on the way the thread is ground on the die. I think I have done this in the past and it worked. You could thread the first end then screw it into a fixture that was threaded and with a short plain part for extra support. put a screw with locking nut into the back of the fixture to prevent the stud from screwing futher into the fixture.

Les.

Nick as far the dies are concerned Coventry dies have minimal lead however if you look carefully at your split die the opposite wide will have minimal taper so you start with the "right" side then turn the die around to finish .

My guess is that it is a very small diameter thread ? Holding may be a problem best to use collets, if they are morse taper type or similar then they will probably grip OK, if you are using ER or similar then use a small packing piece in the back of the collet turned to the same dia as your work. I have done this and held it in place with blue tac, this stops the collet collapsing at the rear. For your application you probably will not be running under power but I have used this method when making very small parts many times.

If you don't have collets there is a way of doing this in your chuck but a sketch would be easier to explain, let me know if you need this but it is a bush made like a collet and gripped in the chuck

John

.

The BA split dies I have seem to have the same taper front and back so perhaps a die nut is the answer.

John, Yes I think perhaps your idea of using a collet with a same diameter dowel in the back may be a good idea. Also if it could be fixed in a temp way it would act as a length gauge so that they would all be the same length if a few of them had to be made the same.

Nick

I make the studs I need on a repetition lathe, using a Coventry diehead for the threads. For cutting the second thread I use a jig as described:

The stud is 1/4" BSF and the plain portion, including the partially cut threads, needs to be no more than 3/16". I use a brass stop in the jig to prevent damage to the end of the stud. The thread that will be hidden is cut second. The threading process tightens the stud into the jig. I use a mole wrench to remove it, which leaves faint marks on the thread. These can just be seen, as a line of 'dots', in the stud that is in the jig. However, when the stud is installed these will not be seen, so I don't care!

The standard throat angle on Coventry dies is 20º, similar to a split die. To make a thread with no 'taper' at the bottom you would need to screwcut or thread mill it.

To avoid trouble with armchair 'experts' and tyre kickers the visible end of the stud should be rounded as shown above.

Andrew

I should have suggested using two locknuts then the stop could be slackened first so the finished stud could be removed easily. Although is would be slower having to remove the jig from the chuck / collet each time.

Les.

For what it's worth I'd make a load of spacers with female threads each end. Now buy long grub screws and run them into the tapped thread. Side steps the taper at the heel of the thread problem, and is a whole lot quicker. You cam also be fussy about what grade of grub screw you use and control the stress point at the change of section.

There was an earlier thread about tapping in the lathe which is relevant.

Rgds. Simon

I take a bit of bar (hex or round) about as long as the threaded bit of the stud, and drill and tap it, then slit it length wise, Screw the half threaded stud in the fixture and clamp in the 3 jaw lathe chuck. If the stud doesn't undo easily, put a screw driver in the slit to open it. Good for as many studs as I make.

Ian S C

This is quite an interesting question as you say the bottom of your threads are always tapered as a result of the "front" face of the die not being able to finish its cut by clearing it. I have presto dies which have a lead on both sides although i have seen ones that have it only on one side, presumably so you can reverse it if you wish.

Like people who have recommended before me, either find a way of buying or making a "bottoming die" or screw cut the remainder.

Michael W

If you know someone with a surface grinder get them to skim the lead off the back of your dies so they butt right upto a shoulder.

You can bodge this yourself with a dremel and just grind away the middle leaving the OD untouche dso the die still sits flat in your diestocks.

What wrong with having a portion of tapered thread on a stud,assuming the stud is for making models and full size studs have a taper where the thread finishes,so why not make the model studs the same. Where a thread is required right up to a shoulder ,in my day usual practice was surface grind the back face of the die to get rid of any taper, I find that for gripping studs,ER collets are best, also when making old style Whit nuts as I have been this morning for a no 1 Gardner engine ,ER collets and a morse taper shank collet holder in the tailstock really grip the taps without slipping.

I was wondering that too.............

Andrew

whatever is desired wont fully fasten supposedly? A thread to a shoulder would leave an undesirable gap but i suppose i see your point about the stud. 

Michael W

Edited By Michael Walters on 13/02/2016 15:20:00

The end of a thread die is tapered to aid cutting and to reduce the stress point caused by a sharp edge at the front end of the cut thread.

Normal engineering practice, if you want a full length thread to a shoulder, is to add an undercut with a radius tool at the end of the thread to a little below the root diameter of the thread.

You get a full length thread and then a radius to the full diameter with a minimal stress raising transition.

To hold a short thread make a flanged threaded bush, with a single split, to fit a 3 jaw chuck or small collet

The devices into which a threaded component is screwed, and locked with a screw, are known as stud boxes in my world. They are easily made from hexagon bar, and the locking screw can be of any type that suits, (hex head, Capscrew or grubscrew. The lockscrew ensures that there is enough friction to stop the workpiece rotating whilst the thread is being cut on the other end.

If made of hexagon bar, rather than round, they can be used to set, or to extract studs. To set a stud, drive using the setscrew. To remove a stud, rotate using the spanner on the hexagon bar, but keep the locking setscrew tight with a second spanner. Once finished just slacken the locking setscrew, and the studbox should unscrew by hand.

If using a hexagon head setscrew it is preferable to use hexagon bar of a different size from that of the setscrew head; unless you have lots of spanners of each size.

Howard