ER Colletts - will they hold my plug?

I am thinking of getting an ER collet for my mini lathe. I am new to lathes so please bear with me.

I have a 20mm stainless plug and the head is 25mm.

I want to grip the 25mm head and machine the screw part

Problem with the 3 jaw chuck is it is hard to center the plug.

Would the ER collet help!!! Any advice please

Hi Jim,

If you want to grip a 25mm diameter rod you will need an ER-40 collet system, may be something like this, from ARC. You could of course use a 4-jaw independent chuck.

I made an ER-32 chuck for my smaller lathe and I am satisfied, but ER-32 collets only go up to 20mm.

Thor

Edited By Thor on 01/09/2016 17:27:16

I think it unlikely that anything short of an ER40 size collet would do - ER32 has a maximum diameter of 20mm. If your 25mm head is very short, then an ER collet would not be a good plan as it would distort badly and not grip well - unless you fitted a short 25mm disc in the far end as well.

I don't think ER40 collet chucks are readily available for mini lathes. (ER collets really are for cutting tools only, not material, despite what people - including me - actually use them for.)

In your case, I would fit a piece of material in the 3-jaw chuck and BORE it out to 25mm. I'd mark it against jaw No. 1 and remove it, cut through one side of it to make a split collet and then use that to hold your parts.

You would be better making the whole thing from scratch, but it's obviously your decision.

Tony

Soft jaws machined to suit is an option, I use soft jaws when I want to hold a part true and have some strange jaws from holding loco wheels etc.

Edited By Bob Brown 1 on 01/09/2016 17:45:38

As Bob says soft jaws or the 4-jaw unless you have masses of them to make.

If you want to go the collet route then 5C will do you nicely

There are ER40 collet chucks available with certain recess sizes. Not sure of the size of the reces on a mini lathe

**LINK**

I would have thought that a 4 jaw which may have come with the lathe and a purchase of a decent DTI would be a better investment for one offs.

John

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I made a backplate to fit an ER 32 collet chuck to my 10K South Bend. I already had the collets for my mill. I am very satisfied with this setup. One shortcoming of the ER or other collets primarily designed to hold tools: they do not work well when the part or tool does not extend through the full length of the collet. To hold extremely short work you can make a plug the same size of the work to fit the back end of the collet.

What I want to do is put a spring recess 10mm wide by 1mm deep in the plug that screws down on the spring.

I have the 2 flute end mill to do the job. Just looking for a quick way to center the plug in the chuck or whatever.

Have a good few to do!!!

I'm wondering why your 3 jaw is not good enough for this.

Is it that the 25mm head is quiet short so the end of the thread can wobble if the work is not being held perfectly true across the head.

Are the plugs turned or forged in which case the thread may not be true to the head anyway.

Also what length is the threaded part in relation to the head, if ther is not much length to grip and/or the thread is long there is a risk of the work moving as the cutter makes contact.

All three of these could be solved by Frances' method

Edited By Frances IoM on 02/09/2016 08:35:18

Split collet, Turn and bore a piece of material with the O.D.just larger than the head. Mark where No1 jaw is positioned on the job and part off to length. Hacksaw through the new collet along it's length midway between where two of the jaws will come. Clean up the saw cut on the inside. Put your plug into the collet place it back in the 3 jaw with the head on the inside of the chuck making sure you line up No1 jaw and your previously made mark. job done. While this is not deadly accurate it is simple and effective and works on keeping the screw concentric.

Edited By Dusty on 02/09/2016 09:45:56

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Jim ^^^ is the method described by Frances

Hi Jim,

Is this what you are trying to produce? If so, how deep in mm is the head that needs to be gripped?

Ta,

Dave

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Why would I do that, Frances ?

The question was specific, so I answered it.

MichaelG.