How to chuck a bolt head

Go with NDIY, 'cut a centre and support with a tailstock centre' or hold the thread in a bush or collet and cut plain diameter.

Tony

Which bit should read 15cm, the overall bolt length or the turned down section?
What thread is it; looks to be M10 or M12.

On the Myford, I'd probably hold the head in the 3 jaw and use tailstock support, as we're not bothered about perfect concentricity for this one (use the 4 jaw if you are).
If you have a fixed steady, maybe turn down a plain nut to a round threaded tube, then using a second nut, lock it onto the thread.
The round nut you've just turned down will run in the fixed steady and allow accurate centre drilling.
If you really do need a 6" (15cm=150mm) turned down section, leave the steady there and use it as well as the running centre in the tailstock.

Bill
Bill

NDIY -

That's worded a bit unkindly. Philip has asked under "Beginners' Questions", what to many of us might be a simple problem, but perhaps in consequence has not realised we need better information to help him.

Including that matter of the 40 cm??

Philip -

I think what you are asking is basically simple but the differing replies suggest we've not all grasped what you are making, because I am afraid you've not given sufficient information.

It's best with a question like this to give a dimensioned sketch. It does not need be a proper engineering drawing to ISO-umptyone for something like this. Just a photo of a simple sketch on plain paper.

In particular here: if I am right about your intention, which is to turn the end of an ordinary bolt down to form a long spigot. You need verify the units (I don't believe 40 centimetres as that would call for a fabrication not a modified bolt), the diameter and length of the stock bolt, and the diameter and length of the turned section.

In which case your question should read something this, and I'm assuming you are working in metric:

'

I need turn the end of a standard [insert designation] hexagon-headed, high-tensile bolt down to x mm for y mm length, to form a spigot that fits a hole down the end of a shaft; as part of a special puller.

How do I grip the bolt in the chuck and support the outer end?

.

That alone ought suffice, even without a sketch; and I and no doubt others would have replied, as I have above:

Put the bolt as far back in the chuck as possible, gripped by a split-collet or lock-nuts; centre-drill the tip; draw the bolt out sufficiently far but still gripped for as much length as possible, and support it with a tailstock centre.

You may need use a half-centre for tool access, and even then, as an ML7 owner myself, I'd say you'd probably also need swing the top-slide back at an angle to clear the tailstock, and then use the rack feed. Or lead-screw if your lathe has a graduated lead-screw handle.

My lathe does have a lead-screw dial, but I don't use it very often. If the spigot length is not critical I usually move the tool along with the lathe switched off, to rule measurement, switch the machine on and make a light cut there as a marker. The finished length is usually easy enough to bring within tolerance.

Thank you Nigel, I was a bit concerned my question was worded incorrectly which attracted comments.

I have a high tensile bolt that is 15cm long and need to reduce the bolt down in size for 4cm from the end to enable it to fit through a hole in a clutch assembly.

I added a link to the thread which shows the puller.

I will take a photo of the bolt placed next to the one I am trying to replace and paste it here

For anyone who wants to see this part here is the short version of the link **LINK**

Looking at the picture online I think it looks like the reduced section of the bolt has been made with a grinder. It only has to go down a hole so minimum required for cheapest cost is probably a bench grinder and an unskilled worker.

Martin C

How do I attach the pics?

I know I could grind down the bolt but as I have the lathe I'd like to do the job properly

Had it been a bolt then my fixed steady suggestion would have been ideal as you would have had the fingerts running on the plain shank of the bolt, your image shows a screw so as Nigel said best not to run on the threaded surface

Will he hex head fit down your lathe's spindle? If so drill and tap say a 20mm length of scrap, put a length ways saw cut in it then screw onto the hex head screw so 45mm sticks out. Now hold by the split bush you just made and turn to end down to dia

I'd just grip on the thread with a 3-jaw chuck and turn down the end. As long as the workshop gorilla doesn't tighten the chuck the thread will be fine.

Andrew

My immidiate reaction to the problem would be to make a split collet either plain or threaded. Take a piece of brass or steel with a diameter just greater than the corner to corner distance of the head, face both ends to just shy of the length of remaining thread on the finished item in the 3 way chuck and either drill to a bare clearence or thread to the same as the bolt. Before removing from the chuck add a centre pop adjacent to chuck jaw 1 so you can rechuck in the same position. Remove and slit one side lengthways with a saw so that the chuck jaws can clamp between the saw cut (s). It may pay at this stage to add a couple of additional saw cut part thickness at 120° and 240° just to make it a little more flaxible. Clean up and insert the embryo part into the collet and replace in the 3 jaw with the dot next to jaw 1. Tighten the chuck and the bolt will be firmly held and on centre. You can now do whatever maching you like. (It takes longer to write than it does to make one)

regards Martin

Ah just seen that you have 4 inches free thread in which case it will fit in the 3 jaw as Andrew says with the head behind the jaws . Remember my method for much shorter thread length.

Edited By Martin Kyte on 23/09/2022 13:25:00

Zero precision required on the de-threaded part. Quit faffing around on the computer and have at it with the angle grinder.

edit - make sure you put a nut on the threaded part first, then after trimming the thread undo the nut to clean up the end of the thread.

Edited By Bazyle on 23/09/2022 13:23:07

Thanks guys, really appreciate all your suggestions and advice. Off to have a go on the Myford later today.

Cheers,

Phil.

Hi Philip, this is not having a go at you, just as a matter of curiosity. You are presumably something of a model engineer as you have a lathe so why do you use cm rather than mm.

Model engineers frequently talk in imperial units but that's because most drawings, being of pre decimal age are in imperial, however most of us will be very used to the metric system, cm are not an SI preferred unit. (multiples of 1000)

I'm always having a go at my daughter in law for using cm, she is a teacher and she can't explain why they use cm in preference to mm in schools, i am sure I haver never seen an engineering drawing using cm.

Bill D

Hi Bill, I'm afraid I'm not a model engineer more of a mechanical engineer where I build, repair and service small engines mostly on garden machinery.

I was lucky enough to buy my lathe when a work colleague, (when I was working, now retired), offered it for sale as his grandfather had died and he needed to clear out his work shop for a giveaway price which included many and I mean tools and accesories for it.

I joined the forum to enable me to ask what most on here would consider beginners questions and have been lucky to receive really excellent information.

I realised I should have used mm not cm, but I formed the question late one night and was obviously not fully awake.

For the proportions shown in the picture, I'd think that the screw could be held with the 3-jaw chuck gripping on the threaded secction and the hexagon head beyond the back of the jaws somewhere in the morse taper of the lathe spindle Leave enough sticking out of the chuck for turning down the diameter.

I suspect the head won't go down the spindle of an ml7. I wouldn't have started from here, a length of all thread with either a nut welded on afterwards or 2 nuts locked together would make life easier

Another way: get a 20 cm bolt, chuck up 4cm thread, turn down end near chuck, part off. All sorts of things would work as it looks like accuracy isn't required. I might just spin it in a drill against a grinder to take the thread off.

I don't know the 'right way' to do it

Or centre punch the end, put a centre drill in your cordless drill and drill a centre hole in the end of the bolt. Mow hold by the hex in your 3-jaw with support at the other end by a tailstock centre and your job will be well supported

That.

All of it. Although using a bench grinder would be quicker and easier