Er32 chuck for Fortis lathe

Been a while since I've had time for my wee workshop ,so today I decided I would make the er32 chuck I've wanted for a while now ,so I used a chunk of stainless I had ,probably not ideal but it's what I had . It's not perfect but it's accurate where it matters . I put a tenths indicator on the inside of the collet taper and it barely moved which kinda surprised me a bit 😁 but I'll take it . The only negative is the cheapo collet set I bought have 0.002 run out ,I tested using three different sized carbide End mills in the collects. .

ER chucks were developed for holding tooling and for most cases the runout you have would be fine. Home workshop users have started to use them for workholding and this may then give unacceptable results. If you have a 4 jaw independent chuck you can get the runout required for what you are doing if it needs to be lower and as a compromise, if you want to also use your ER collets, you can mount a collet holder in a 4 jaw chuck. A square ER32 collet chuck may be your next piece of tooling to make or buy. They are also useful for holding round parts in a vice for milling so not limited to one infrequent use.

Martin C

Hi Sean

Have you modified the collet closing nut in some way as all of my ER collet nuts wrap around the front face of the collet which hinders working close to the collet face.

Does the nut still engage the slot in the collet to assist removal ?

Thanks, Emgee

Well-spotted, Emgee

Whatever that modification might be, it could be useful !!

MichaelG.

Or more likely the nut has just been tightened down a bit on the empty collet which makes it stick out.

Same 12mm collet one with a cutter the other tightened down a bit by hand with nothing in it

Edited By JasonB on 11/11/2018 11:04:59

sean logie:

For 'tis a jolly good lathe!

Here is my shop-made version showing also a GHT-inspired dividing attachment for use with milling and drilling spindle:

Not obvious in the photo but I have made the chuck body long enough to be able to work up close despite the gap.

Tony Griffiths gives them a good write-up as you are no doubt aware.

Don't necessarily put the run-out down to your "cheapo" collets. I made a similar ER25 chuck and at first had a few thou. run-out, similar for all my collets despite the taper running true. I thought that this might be due to making the screw-thread a wee bit too tight, so took off a shaving. Sure enough, the run-out reduced to less than a thou. at which I'm quite happy.

Clive

Edited By Clive Brown 1 on 11/11/2018 14:33:07

I was thinking the same Clive. The nut should centre itself on the front of the collet, not on the thread.

Russell

Interesting point; my Quick Step Mill with ER20 spindle came with a rather loose collet nut. The designer/manufacturer may have had the same idea in mind.

After checking further all Emco made ER25 collet chucks I use have the front of the nut extended to always be about 2mm in front of the collet face .
The other makes including Schaublin (RH front in pic) do allow almost flush facing if in the lathe.

Emgee