Emco Unimat 2B Arbor Size

Hi folks.

I have what seems to be a very, very old Emco Unimat 2B. I purchased a dividing head from a friend, with 40 and 48 tooth wheels, but the arbor/spindle and the corresponding bore for the 3 jaw from the Unimat mics out to 16.5mm and the dividing head mics out to 17mm. In short, my 3 jaw will not mount to my dividing head, though the 3 set screw holes do line up and are the same thread. Can anyone tell me the arbor diameter on a Unimat chuck known to be made by Emco? I am wondering if this chuck and arbor / spindle cap / whatever it's called are aftermarket, or something? My 3 jaw is not marked, though the 3/8 chuck in my tailstock is clearly stamped "Emco."

I hate to buy an extra 3 jaw just to permanently mount to my dividing head, but if I must, c'est la vie.

Amanda

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Hi Bill,

Here's the critter in question; mine is identical.

http://www.lathes.co.uk/unimat/page10.html

Bill

I have alwaus thought the Unimat DB and SL models had M12x1 spindle and tailstock nose thread, also I have what I believe you refer to as dividing head an indexer that takes different count gears to use in the same head, mine has a M12x1 thread and is bored through 12mm.

Emgee

Hi Bill.

The thread is 12x1. However, the chuck mounts to the... spindle cap? Arbor? Idk the name of the piece - that screws onto that 12x1 thread. It is held in place by 3 machine screws.

The chuck is intended to mount to the indexer in the same fashion, except it cannot. The bore in the chuck and the arbor are 16.5mm in diameter. The arbor on the indexer gear is 17mm in diameter.

https://i.imgur.com/P4esRBf.jpg

https://i.imgur.com/JEK0Slx.jpg

Edited By Manda on 03/03/2022 15:00:21

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Thread size is not the issue. The size of the bore in the back of the chuck is. The chuck does not thread directly onto the spindle. The chuck is screwed onto a spindle cap which is what is threaded 12x1.

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Oh, no! I didn't mean anything you said was wrong. I just figured I was unclear. I am not certain of all the terminology involved here, which is certainly not helpful.

Hi Manda,

May be that what you call a spindle cap is a backplate? As far as my old eyes can see from your imgur photos, there is no thread on on the indexer? Is something missing from the indexer? Would it be possible to machine an adapter that fits the indexer and has a M12x1 thread for the chuck? Or is the indexer just about 0.5mm too large?

Thor

Edited By Thor 🇳🇴 on 03/03/2022 16:55:04

Hi Thor,

It could be called a backplate. The Unimat manual I have doesn't name this part in the diagram of the chuck, sadly. The indexer is, as near as I can tell, complete. The chuck is mounted to the piece that threads onto the spindle with 3 countersunk machine screws. the bore in the center of the chuck rides on the "arbor" of that piece that threads onto the spinde's 12x1 thread.

The chuck mounts to the indexer the same way; the bore in the chuck fits over the nose of the indexer gear, and then is held with 3 machine screws. The nose of the indexer gear is .5mm larger than the piece that threads onto the spindle, so the chuck does not fit it. I just wondered if someone who had a Unimat SL or DB could measure that bore on their chuck, is all. I am trying to determine if somewhere between my lathe's build date sometime in the early 50s and the Unimat SL coming to market in the mid 60s, if that bore changed sizes, or if I have an oddball aftermarket chuck. I do not mind buying another Unimat SL 3 jaw, but if it won't fit my indexer, it's not going to help me.

Amanda

PS. I have no idea how to post pictures direct to the site. This forum works very differently from others, it seems!

Hi Amanda,

Posting photos is a bit tricky, see here. Unfortunately my SL is now in use on my toolgrinder and the rest packed away.
The Unimat SL manual can be downloaded here. So it seems that the arbor of the indexer is 0.5mm larger than the hole in the chuck. One option is to bore out the chuck so it fits the indexer (you would then have to make a new backplate/flange or turn a new register on the backplate). Another option is to make an adapter that fits the indexer on one side and the chuck on the other, you might loose some headroom.

Thor

I've used this site for years but never noticed any FAQ's. I've just tried to find 'all thread' too and failed.

Putting FAQ into the search box does not produce any results either.

Ian P

(re Frances IOM post above)

Edited By Ian P on 03/03/2022 17:35:42

Ian, if you click " View All Topics " under Latest Posts you will find Website FAQ's.

Thor

'View all Topics' does not appear on my screen from 'Latest Posts'. OK I'm being picky but the mention of FAQ piqued my interest.

By default I set my view of the forum to 'Latest posts' and have never yet looked for post by the individual forum titles. I'd never come across the FAQ's and I suppose if the this website's own built in search does not know of their existence its unlikely they would contain anything very useful

Ian P

That is strange Ian, it shows up on my Firefox screen:

One of the peculiarities of the Forum software?

Thor

Hi all!

Thor, the manual was a godsend. It says that the piece that threads onto the 12x1 spindle thread is a "flange" and that the "turning diameter" of the flange (the arbor onto which the 3 jaw fits) should be .669 inches in diameter... exactly 17mm. As my chuck has a *smaller* bore than this I am going to guess that the size changed at some point between when mine was made and when the SL was made. I will seek out an SL 3 jaw chuck, I suppose. THANK YOU!

Amanda

Hi Amanda,

Glad to help.

Thor