Collet chuck

Hi,

I need an ER40 collet chuck for my Myford Super 7.

I have found two types, one with the collet chuck on an MT2 taper (quick and simple) and the other the collet chuck is on a back plate.

This would then need mounting on a backplate with the 1 1/8" thread to screw onto the spindle nose. This set up works out more expenivse plus I would have mounting to do.

Are there any pros and cons as to which one to choose ?

Thanks

I have an MT4 spindle but I found that the morse taper collet chuck has concentricity problems either through manufacture or imperfect seating of the taper, maybe the drawbar isn't tight enough, In any case I found it couldn't give a satisfactory run out for what you would expect from a collet. Was hovering around 0.07-0.14mm runout 5mm or so from the chuck, checked against a silver steel bar for all that's worth, I can get better out of my 3 jaw. 

Michael W

Edited By Michael-w on 08/02/2018 20:49:29

Andy,

As you rightly say, the morse taper version will be qick to mount and use. Its major downside is that you can't pass material through it like you can with the backplate-mounted type, so you're restricted to short lengths of material. An additional benefit to the latter is that once you've put the stock in the chuck, you can "bump" it to centre the workpiece by slackening the mounting bolts a little. If you only get one and can afford the extra cash, I'd advise you to get the backplate mounted one.

John

Go with the back plate variety, you machine the back plate in-situ to accept it giving good concentricity and you will then also have through capacity.

Backplate for definite! Slightly harder to fit and maybe more expensive but you can fit long material through and overhand is less.

And regarding the MT version, if you can't use a drawbar with it, that's another negative mark against it.

Well its looking like its going to be the back plate type from all these replies I have read.

Which then leads to one more question!

What would be the reason to get a 125mm diameter back plate type instead of the 100mm one? At the moment I can't think of a valid one but I am sure I will soon find out!

I appreciate your help

And if one option is chinese, beware that not all 2MTs are 2MT! One particular supplier is very risky, IMO. Even with a drawbar you may damage the spindle socket.

Have you considered making the body and buying the collet nut?

HH's excellent description here **LINK** would be easy to adapt. All ER collets use the same taper angle and the thread for the nut of ER40 is M50x1.5 and so a short piece of 2" or 2.25" bar stock would be all you need.

HTH

Jon

Depending on if you have made/may make a ball turning attachment the 100mm is the way to go for better access.

My ball turning attachment is from the Steve Bedair style and the cross slide mounting of the attachment could foul on a bigger backplate.

Picking up Jon's suggestion I had a look at HH's page and it looks a good approach. When I have made ER collet sockets using the top slide to make the taper I've set the slide by chucking a bit of bar, turning to a precise mm size so it runs true, then sliding on a collet of the corresponding size. You can then use a finger type dti on the topslide on the side of the collet between the slits to set the taper. Worked fine for me. (Though now I just set the taper angle in a Mach 3 wizard.)

Would that be an organic chick?


Doug

Does it have to be an ER40? There seem to be more fixtures and fittings that take ER32.

Collets up to 30mm are available for ER40, that can be very handy and Stevenson's Collet Blocks are available in ER40

Vic, the bar I am holdng is 25mm so I have to go up to ER40, which is a pity as I have a set of ER 32 collets

That’s interesting. Only trouble is I only have a 20mm bore on my lathe. Might come in handy for something though, I’ll have to remember it, thanks.