Emco Compact 5 collet holder

Hello. I've been using unimat/compact lathes for years but am self-taught and seriously unqualified!. I've been lucky enough to acquire a Compact 5, and would like your opinions on a collet holder for it, in the absence of the official Emco version.

I've had bad luck with collets in the past, including on an original spindle Cowells, and a Proxxon. My Unimat 3 style holder works well, and the direct spindle insertion on my Minilor also works; I'm therefore rather nervous of the bolt-on types. One German trader on Ebay sells some simple types for various MT bores that go straight into the spindle with no holder or locking device, and another one sells what seems to be a direct Emco-style substitute (bolt-on).

Any comments from yourselves gratefully received, with thanks.

Geoff

Sadly Geoff, the "Emco" name has become NEARLY as statusified as "Myford", inflated prices for the privaledge of owning a stamped original. My V10 is quite happy using "Standard" non Emco items. A decent set of far eastern collets and the spindle adaptor won't compromise the "compact".

Through spindle collets usually need a draw bar, - - - and a clout to release, poor bearings.

Regards Ian.

Edited By Circlip on 21/07/2021 11:13:39

Probably your best option is to purchase one of the er collet chucks as sold by arc, chronos, rdg etc and a separate back plate. You then machine the register while fitted on the lathe ensuring minimal runout. 🙂

Thanks to you both for your replies. I'll investigate. I hear what you say about prices!

Geoff

Geoff

You can buy an Emco bolt direct to spindle ER25 collet chuck for the same cost or cheaper as messing with a new backplate to fit on the Emco 5 spindle and a Backplate mounting ER type collet chuck.

Collets are going to cost extra whichever way you go but remember some very low cost collets have excess TIR.

Emgee

Edit to add picture

Edited By Emgee on 21/07/2021 14:35:38

Having owned and used the Emco collet holder for the Compact 5. I was not happy with the amount of overhang that the factory original had. Nor was I taken by the wasting needed to get the bolts into place.

I therefore set about designing something which has less overhang, is more rigid due to the cut-outs for the capscrews and uses a smaller collet closing nut. The result is one more compact unit which uses the same ESX 25 collets.

Regards

Gray,

Gray

Looks to me your collet chuck has more overhang to the collet face than the Emco part, but yes the hex sets are fiddly to get in/out.

Emgee

One of the best reasons for having in-spindle collets is the minimal overhang. Parting off is much easier than when the same part is in a chuck and the parting operation is well away from the headstock.

Martin C

Hi Emgee,

The original Emco collet attachment that I had, gave me the dimension that I had to beat as regards overhang. From memory my attachment is something like 8mm shorter. This may not seem a lot but it does make a difference.

Regards

Gray,

Gray. Another ingenious and beautifully executed production! Please put me (us?) out of my (our) misery. How are the relief pockets for the cap head screws machined? I can think of one solution, without making the flange as a separate item, but I'd expect yours to be better...

Once again, thanks to all of you for your contributions to my query.

Geoff

Direktspannzangen, 7-teilig With MK2 New Collet Set | eBay

Any comments on these?

Geoff

The pockets were milled using a Boring Head and a tool similar to a parting tool, slow and steady wins the day. A large Tee-slot cutter could be used but this depends on the milling facilities and it is not for the faint hearted.

Regards

Gray,

Hi Geoff,

I use these Draw-in No 2 Morse collets as well as my ESX 25. Whereas the ESX, and ER collets have a working range of 0.5 or 1.0 mm, depending on the nominal size of the collet. The Draw-in collets are a little more fussy and need to grip on a nominal diameter or very near.

When I worked on a Hardinge HLV lathe, the Draw-in collets of this machine, (5C) had a gripping tolerance of Nominal to minus 0.025mm or 0.001" set by the manufacturer of the collets. Deviating from this will not only ruin the collet but will seriously effect the collets original concentricity guarantee. These collets would never be used to hold barstock, only turned diameters.

The draw in collet does have an advantage over the ESX, ER collet in that it can hold a shorter length of diameter, especially if this diameter abuts a shoulder. However the gripping capacity of the No 2 Morse collet is inferior to the 5C in these circumstances.

Hope this helps

Regards

Gray,

Edited By Graham Meek on 22/07/2021 11:44:05

Yep, as expected, a better idea than mine! Thanks.

All of the Emco 5 cnc lathes I have or had needed the small end of the MT2 arbor reducing in diameter to fully enter the spindle, seems they were built to accept a shorter length taper.

Emgee

Hi Emgee,

It is funny you should say that, as I spent ages getting a set of No 2 Morse Collets that did not disappear into the spindle. Those I have of Eastern origin, which I use on my 2/3 rds Quorn, all go in too far. While a set I bought made in the USA, and are years old, do not.

I must therefore urge Geoff on the side of caution if going down this route. The problem could be overcome by using a sub-plate screwed to the spindle nose and bored through No 2 Morse. This would ensure maximum concentricity and it would not need to be the entire length of the Morse taper. Just sufficiently long enough for the working portion of the collet.

This approach could be extended to suit other collets, provided the collet draw tube will enter the Compact 5 Spindle.

Regards

Gray,

This is the sort of thing I had in mind, which would allow any No 2 Morse collets to be used.

Regards

Gray,

Again, many thanks for all the information, gentlemen.

Geoff

Just found this Collet chuck on an Emco page, can't figure out how the screwhead recess was machined into the pocket unless the tool was located in the circular recess and then fitted to the spindle, any ideas ?

Emgee