Which collet

[John MillisParticipant @johnmillis57685]

I am considering purchasing a MT3 collet chuck for my CJ18 mini lathe but am unsure which to get

I already have an MT2 ER25 that I use on the mill.

I don’t want to use a MT 2 to MT3 adapter

am I limited to the size of work I will be able to hold depending on which version of collet I choose

[ChrisLHParticipant @chrislh]

For lathe work a collet chuck that fits on the spindle nose is usual so that work can pass through the lathe spindle. Whether such is commercially available though depends on your lathe design. As you will know ER collets are good because they do not require a drawbar, they steplessly cover any size within their range and they grip really well. Have a look at the Arc Euro Trade site and look for “ER lathe collet chucks” to get an idea of what is available.

[peak4Participant @peak4]

As above, though it depends on your budget.
Personally I would go for a collet system that is a chuck replacement, rather than an MT spindle fitting, as it allows for longer workpieces.
From what I can see, your lathe has a 20mm through bore; ER25 only goes up to 16mm(ish)

If finances allow, I’d look for a backplate mounting ER chuck; ER25 to use your existing collets, or if finances allow, ER32 or 40 plus a set of collets, though that would obviously be far more expensive.

I have ER25 setups on MT2 & Myford nose thread.
The latter chuck now lives on the Dore Westbury mill most of the time since I picked up a 5C setup for the larger GH1330 from Bogstandard’s workshop sale.
The MT2-ER25 is used for plain cutter (solid carbide) holding on the Centec, almost never on a lathe.
I subsequently found a second 5C chuck going cheap, which is now fitted to a Myford backplate, so I have the best of both worlds.

Bill

[bernard towersParticipant @bernardtowers37738]

If ER25 collet chuck is only one available you can go up to 20 mm with it, I have a set of 17/18/19/20mm collets for mine and very handy they have been sometimes.

[MikeKParticipant @mikek40713]

I’ve been suffering with MT3 collets in the spindle, but I plan to make or buy a collet chuck for ER32 collets like this guy:

https://gadgetbuilder.com/ER32Chuck.html

We have a vendor here in the States that carries manufactured chucks, so I assume you have them in the UK as well.

https://littlemachineshop.com/products/product_view.php?ProductID=2532

[SillyOldDufferModerator @sillyoldduffer]

Pictures pinched from ArcEuro!

First I’d stick with ER25, rather than ER32 or a different system, because you already have ER25 collets for your mill – save money!

ER25 collets cover a reasonable range, 1 to 16mm, probably my choice for a mini-lathe.   If bigger is needed look to ER32 (2-20mm) or ER40 (3-26mm).

One way of mounting ER collets is a collet chuck connected to an MT taper that plugs into the spindle:

 

 

Main disadvantage is this type is threaded for a drawbar so long stock can’t be passed through the spindle.  You can’t shove a rod through the headstock, grip it with a collet, work on it, part-off and repeat, which is handy for repetitive work.   Without a drawbar there is some risk this type might come loose in the headstock.   They can be plugged straight into the lathe and should be accurate without further adjustment.   Not all lathe spindles will take a full-length MT male, in which case saw it off!

The alternative is a lathe collet chuck:

 

These attach to the baseplate and probably have to be zeroed.  Mine is zeroed with a DTI by tapping it with a mallet, but once done collets can be swapped without affecting accuracy.  No need for a drawbar and long stock can be passed through the spindle.

Which is best depends on the type of work you do.    For me the advantages of the lathe collet chuck type out-weigh the quick change possibilities of the MT holder.

If serious about collets 5C is a good choice.  The ER system only holds round stock, and the whole grip length of the collet should be used.   5C collets can be £bought to hold square stock, and I believe they don’t need as much grip length.  A major disadvantage in my cheapskate workshop is that 5C is price, and because their grip diameters are small limited, a lot more expensive collets are needed compared with ER.    I think ER is a better bet unless you already know why you need 5C!

Dave

 

[old martParticipant @oldmart]

The Atlas 12 x 24 has an MT3 taper inside its spindle and I got an er25/ MT3 for it and when a brand new 1/2″ Jacobs chuck made in the USA was given to the museum, I got a MT3 arbor to fit it to. The chuck was drilled through the body and the arbor was drilled and tapped for a securing SHCS. Both share a shop made drawbar made from 12mm studding. We also have one of the plates for the er25 which can be fitted to backplates for both lathes, and can be zeroed as they don’t have registers, one being 1 3/4 x 8W and the other 1 1/2 x 8 UN.

I saw a plate for er50 for sale on ebay the other day, I didn’t know they went that big.

[John MillisParticipant @johnmillis57685]

Many thanks for your great advice it has opened my eyes to what is available

[Author]

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