modifying Schaublin collets

[Ken WeeksParticipant @kenweeks58536]

I have a Pultra 1590 lathe that I am getting back into use, it is designed to use 20mm collets.

The likelihood of finding genuine collets is very unlikely.

Schaublin w20 collets have the same thread and dimensions but the locating key way slot is about 3mm to short.

Would it be possible to extend the slot?

Ken

[Ken WeeksParticipant @kenweeks58536]

[Matt HarringtonParticipant @mattharrington87221]

You will probably have to grind the keyway as they are hardnened. A pencil air grinder with a suitable wheel is chaeap and effective for this.

Matt

[Ady1Participant @ady1]

Find a duplicate collet and practice on it to see what works best.

Collets can be extremely hard and they are also flexible which makes working on them quite difficult

As mentioned, grinding is probbly the way to go

[jason udallParticipant @jasonudall57142]

Just a thought…wouldn’t modifying the key be better…only one to do rather than a set…

Of course this might be one very difficult mod versus 10-20 simple mod s…
And of course the is the possible effect on the “value” of the lathe…

[Ady1Participant @ady1]

Just a thought…wouldn't modifying the key be better…only one to do rather than a set…

It's in pretty deep but could be coaxed out and ground down…

Ken. Are you sure that these collets have the same profile?

The angle at the thick end for example?

[Ken WeeksParticipant @kenweeks58536]

Thanks for the replies.

Removing the key entails stripping down the headstock, not to sure I want to do that again.

I think if possible my chosen option of modifying the collets is the safest way to go.

Ady I take your point about the draw angle, the idea was to modify one and test.

I have the feeling that I read somewhere about modifying collets with a carbide cutter.

Ken

[John HaineParticipant @johnhaine32865]

At one point I inherited an Aciera F1 and found that this company:

http://www.floydautomatic.co.uk/products.asp

actually make collets, in fact they make Schaublin ones, so maybe they could make some with a longer keyway? They are based in Baldock, Herts. I seem to remember that their W20 ones seemed quite reasonably priced, so may not be prohibitive to get specials especially since it's a small variation. Could even be a niche product for them as there are enough Pultras around, I bet they have been asked before.

John.

[Ady1Participant @ady1]

The collets I wondered would fit are those Alexander/Deckel FP1 collets but I never bought one to try it out

[Ady1Participant @ady1]

dubble post

Edited By Ady1 on 08/09/2014 21:40:19

[Emma WatleyParticipant @emmawatley24025]

hi im new and just started an engineering course in college, just on here to look for help and advice, emma x

[Ken WeeksParticipant @kenweeks58536]

The 1590 is a rare lathe I have only seen one other for sale in the last year.

It is about three times the size of the 17xx series, I have posted a few pictures in Kens album.

Thanks for the link to http://www.floydautomatic.co.uk/products.asp, I have found a supplier in Germany as well.

The Alexander/Deckel FP1 collets appear to have a different thread.

Hi Emma good luck with your Engineering course the start of a great career.

There is a beginners questions section on this forum, have a read through post in this and other sections to give you an idea of what the forum is all about.

Harold Hall http://www.homews.co.uk/ has an interesting site, and I have found Home Model Engine Machinist http://www.homemodelenginemachinist.com/ interesting.

A general internet search for model engineering should bring up a selection to look at and find something of particular interest to you.

Ken

[Ian S CParticipant @iansc]

Emma, another web site worth looking in on is Model Engine Maker. Good luck with your engineering course, and career in engineering. Ian S C

[Bob StevensonParticipant @bobstevenson13909]

I think you will find that collets for the Smart & Brown lathes,…the models L and A, will also fit the 'big' Pultra as both are 20mm and made by the same company(Pultra now defunct)

[Ken WeeksParticipant @kenweeks58536]

Hi Bob

Had a look into this Lathes.co.uk website and the Yahoo Smart and Brown group give the spindle bore as 63/64" or 25mm unfortunately..

Thanks for posting and giving me your thoughts.

Ken

[Oompa LumpaParticipant @oompalumpa34302]

Posted by Emma Watley on 08/09/2014 21:42:27:

hi im new and just started an engineering course in college, just on here to look for help and advice, emma x

You are the daughter of Godzilla and I claim my five pounds!

graham.

[Emma WatleyParticipant @emmawatley24025]

Graham I think your nuts lol what do you mean daughter of Godzilla?? x

[MuzzerParticipant @muzzer]

I have the feeling that I read somewhere about modifying collets with a carbide cutter.

I don't know if you were thinking of my recent use of a carbide indexable tool for cutting a hardened steel ballscrew housing but some of the common grades are indeed rated for working hardened steel. You have to run the piece at the specified surface speed and take proper (but light) cuts but if you don't mind setting fire to yourself and your workshop, it may be worth trying. The limitation may be getting your machine to deliver enough power at a high enough speed for the tool to cut properly. The advantage is that you don't need to anneal the work or use a grinder and it's reasonably quick.

My experience was with the flange of a hardened ballscrew of around 2" diameter that needed to be turned down to about 1.2" on the Bantam which has something like a 1.5HP motor. I think I was using in the region of 1800-2000 rpm (ie slightly overspeed) and power feed with carriage stop. The final result was clean and accurate and cost me almost 2 inserts (3 edges out of 4). The sparks were mighty.

My main concern would be the workholding, given the spring of the collet jaws. I have no idea if that is a problem.

There are a couple of photos of the process in one of my albums near the bottom.

Murray

[Ken WeeksParticipant @kenweeks58536]

Hi Murray

Thanks for the post.

Still thinking about how to do this having taken all comments on board.

The key way slot needs to be extended by 4mm x 1mm deep.

Ken

[Matt HarringtonParticipant @mattharrington87221]

Have a look here:

I bought one from a famous auction site for £15 and have found it useful for the sort of job you want to do on hardened steel.

Matt

[Ken WeeksParticipant @kenweeks58536]

Hi Matt

You are the second person to suggest a pencil air grinder, the link to the video was great as I could see what you were talking about.

A picture is worth more than a thousand words to me, and yes very cheap on the well known site.

This seems to be the way to go, just have to work out how to hold it all.

Ken

[vic neweyParticipant @vicnewey60017]

I just resurrected this thread to see if anyone did manage to lengthen the keyway slot on a collet.

I have the same problem as the OP, my collet is a 15mm shank Boley, one of a number of Crawford & Boley collets that came with my lathe and the one I want to use won’t draw in as it’s keyway slot is 5mm shorter than the others for some unknown reason.

I guess grinding is the only option here, the original OP doesn’t seem to have visited the forum lately so might not hear from him.

[Michael GilliganParticipant @michaelgilligan61133]

Vic

I regret that I remain in no position to do any ‘workshop’ activities … but I would like to add a comment if I may.

A common way of producing these slots was with a horizontal milling cutter [as evidenced by the run-out slope], and it would seem very appropriate to do the extension by the same method.

Note: I have no idea what the price of a suitable Tungsten Carbide cutter might be.

MichaelG.

[bernard towersParticipant @bernardtowers37738]

Yes or the more common T slot / woodruff cutter in carbide. you dont mention the width but the typical 4mm wide cutters are about £4 on your favourite site

[Roderick JenkinsParticipant @roderickjenkins93242]

Tubal Cain in “Simple Workshop Devices” describes a fixture for modifying a selection of collets from various manufacturers to a standard key way size.  Hardness of the collets is described as being variable from manufacturer to manufacturer with very few being “dead hard”.  He used a Woodruffe cutter, presumably in High Speed Steel in his day, slowly and with plenty of cutting oil.

Rod

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