Another newbie question (mini lathe 4 jaw chuck mounting)

HI all.

I got a 100mm 4 jaw independant chuck from Arc, and it comes with 4 allen head mounting bolts, which are useless for mounting the chuck. You can't get them into the spindle flange past the headstock casting. My 3 jaw has 3 studs that wind into the chuck and then easily pass though the spindle flange and then 3 nuts go onto them to fasten it all up. I would swap them into the 4 jaw but there are only 3 of them. What does everyone else do? Cut the heads off the supplied bolts and use them as studs?

P.S

Please excuse my terminology, I'm still learning.

SP.

Read the notes on their website where the two red ** says suitable when used with 100mm backplate. Though you don't say what lathe you actually have so their backplate may not fit so use a suitable backplate for your machine

Screws are sized for mounting the chuck to the backplate

Edited By JasonB on 18/12/2019 18:31:12

Jason beat me to it! I have a Mini Lathe and you normally need a separate back plate, this is fastened to the lathe spindle flange by using three M6 studs. This back plate is then machined to suit the back of the four jaw chuck. you will then need to mount the chuck onto the back plate using studs or bolts. Now you have a chuck which you can mount or dismount just like a normal three jaw. The back plate can be left on the four jaw permanently.

I'll try to post up some photos of my four jaw chuck mounting if I get chance.

Ian

My apologies.

My lathe is an Axminster C2. It (contrary to most articles and advertising) has a spindle flange with a 72mm register, and came with a 100mm 3 jaw chuck.

The 100mm 4 jaw fits perfectly up against the flange, and the holes line up, but the supplied bolts won't go past the headstock into the holes in the flange and thence into the chuck. They are too long.

I disregarded the info on ARC's site with the two red ** because everyone seems to assume the C2 has an 80mm chuck and the smaller spindle flange. The dimensions highlighted with the two red** show a 55mm register, which I don''t have, I have 72mm, so Arcs info isn't correct for every C2 lathe. It seems to assume they all come with the smaller 80mm chucks with a 55 mm register, for which you'd then need their adaptor.

Apologies if I'm not making sense? It's been a long day!

SP.

You might have a problem mating 4 holes to 3 holes, you need to select the flange size and pcd of mounting holes appropriate to your lathe flange, they are out there but you need to know what your looking for.
Dave W

Here you go! here are a couple of photos of my 4 jaw mounted onto a backing flange to suit the Mini Lathe..

It's a Pratt Burnerd 4 jaw with front mounting holes, but the method will be the same for rear mounting holes, although it might be a bit trickier marking out the hole positions, and you might need to counterbore the holes to suit the bolt heads.

Hope this helps

Ian

How many holes in your lathes flange?  do they line up with the ones in the 4-jaw chuck?

If so they you can buy or make 4 additional studs as I don't think the supplied cap heads screws will be long enough if you cut them down. Then just use the nuts from your 3-jaw to secure the chuck

Edited By JasonB on 18/12/2019 19:07:20

Hi SP, yes you need to get a backplate, attach the backplate to your new chuck and then fit three or four studs in the back that will fit onto your lathe.

This one I made myself for also fitting to a rotary table, hence the bigger diameter with the four outside holes.

Regards Nick.

Edited By Nicholas Farr on 18/12/2019 19:09:37

My spindle (with the 72mm flange register) has enough holes to enable both the 3 jaw or 4 jaw to be fitted. The three jaw has 3 mounting holes, and the 4 jaw has 4.

It doesn't matter if I offer up the 3 jaw or the 4 jaw, there are holes in the flange to match the ones in the chucks I have. It looks like I'll just have to find some studs the same size as the ones that came with my 3 jaw.

Seems there are quite a lot of variations in spec on the mini lathes. Perhaps even variations in a given quantity of the same machine from the same supplier!

'Caveat Emptor' when it comes to buying accessories. Nothing that can't solved though.

SP.

Edited By asimpleparson on 18/12/2019 19:13:19

So sounds like 6 holes in the flange, in that case do as I suggested and make or buy studs, I think they are M8 so something like this but check the length by measuring one from the 3-jaw, you will also need an extra washer and nut. ideally get a set of 4 nuts and washers then they can be kept loose on the ends of the studs when the chuck is not in use to protect the threads from damage.

SP, you dont need a backing plate, you have the spindle flange with the register and the holes for mounting both the 100mm 3 or 100mm 4 jaw and like Jason suggests you just need 4 studs with nuts and washers.

It was the same on my mini lathe, I fitted the 4 jaw with four studs so they protruded through the spindle flange to the same length as the 3 jaw and then fixed with the 4 nuts and washers, simple.

Edited By Ron Laden on 18/12/2019 19:38:51

As Ron says, you just need 4 studs, washers and nuts.

It's a pity that your chuck didn't come with these - the one I bought with my lathe from Amadeal came with studs.

Yes, it's a shame it didn't come with the studs, but making/modifying them should be straightforward.

My lathe and it's originally supplied 3 jaw didnt come with washers, just the nuts. Would you suggest adding plain washers or some other type? I think spring or shakeproof may be a bit harsh.

I think the important thing that this thread highlights is that buying a mini lathe from an established supplier is easy, but adding the things that make it do the various jobs that we need it to do is not quite as straightforward as it may seem, and a real beginner may need a bit of assistance in order to avoid purchasing the wrong things.

I'm lucky in that I think I have just enough nous to make what I need to fit the chuck. Instead of buying what is needed, I will be finding some bolts of the right type, winding on a nut, cutting off the head with a hacksaw, facing the end with my lathe, winding off the nut past the modified portion to restore the thread, and then using the result. Yes, I'm that raw.

Penny for your thoughts?

SP.

I don't know if this is the norm, but mine came with spring washers.

Photo of the ones that came with the 4 jaw:

3 jaw chuck fixing:

I use M6 washer faced nuts, they have never come loose, and is one less fiddly thing to drop into the swarf. Easier to be found too!

If studs work on your current chucks - and could work on your new chuck - why not simply obtain, or make, four new studs suitable for the job?

Cutting the heads off the bolts may not help, particularly - unless they are actually set screws! It may even be necessary to turn off the heads - rather than simply cutting them off - then threading that end of the bolt to attain a suitable length.

YMMV and I expect there are simple alternatives. Back plates are normally required for two reasons 1) the chuck will not fit directly to the spindle nose, and 2) to ensure concentric running.

SP, yes your method of producing the studs will be fine, I actually used 4 x M8 grub screws which I got in the correct length from a local supplier which just made it easy. One thing I found worth doing was to threadlock the studs into the chuck to stop the studs moving in or out when fitting or removing the nuts, that can become a pain. If you used studs as Jason linked then you could tighten the stud against the plain shoulder which would secure the studs in the chuck.

Hi, unless I was in a hurry I wouldn't bother faffing about looking for suitable bolts to saw a bit of thread off, (you may just need them bolts for something else) better just to get a threaded rod pack e.g. threaded rod and then you would have virtually no waste and you would have some stock for future jobs and as been said, you can stud lock them into the chuck if you wish. My mini lathe only has plain flat washers and standard nuts and have never come loose.

Regards Nick.

P.S. link shows M6, but other sizes are also available.

Edited By Nicholas Farr on 19/12/2019 10:46:12

Just be careful of the grade. Some may not be a particularly good product.

Using different threads on either end of a stud has often been used to attain a suitable clamping force for the same tightening force.

I used short pieces of M6 studding in my 4 Jaw chuck, and plain nuts.

Because of the space, or lack of it, between the back of the flange and the Headstock, I made up Danny M2Z's "widget" to hold the nuts as they are fitted or removed. A few minutes with some thin sheet steel (18 SWG? ) or steel strapping in my case, makes a gadget that saves time, temper and frustration.

Could have used washer faced nut, but then Danny M2Zs widget would probably not fitted.

It featured in M E W some time ago.

Howard