ER40 Collet Chuck

[cfellows]

I decided to make this for my Logan 11" lathe over a year ago and bought a 3" diameter piece of 12L14 stock at that time.  I had planned to make the whole chuck out of this piece of steel.  However, I wound up using part of it for something else and suffered more than a little trepidation at the idea of boring and turning a 2.25" x 8 TPI internal thread.  However, since I had already bought an ER40 collet set, I decided I needed to move ahead with the project. 

I had 2.25" x 8 TPI thread protector collar that I bought years ago and really never used it, so I decided to weld the remainder of the 3" 12L14 piece onto the collar and proceed from there.  Not particularly pretty, but I think it will work very well.



The picture shows the weldment mounted on my lathe and I have turned the outside to the proper diameter for the metric threads needed.  I've also bored out the inside to 1.24" and will turn the internal taper next. 

[Brian Rupnow]

Chuck--I might be making this up---but---I think I read somewhere that 12L14 steel should not be welded. You should check that out. I wouldn't want something to fly apart and conk you on the head!!!---Brian

[b.lindsey]

Here is  some info I found on the web: http://www.practicalmachinist.com/vb/general/welding-12l14-187149/

So apparently it can be welded but with some  caveats.  It can be solver soldered though.

Bill

[cfellows]

Chuck--I might be making this up---but---I think I read somewhere that 12L14 steel should not be welded. You should check that out. I wouldn't want something to fly apart and conk you on the head!!!---Brian

Thanks for the heads up, Brian.  I'll have to keep an eye on it.

I finished up the chuck this evening...



I mounted another ER40 chuck I had in my lathe chuck and used a dial indicator to match the angle on the compound to the angle in the chuck.  Then I turned the taper in my new chuck using the compound.



The threads were an interesting experiment.  The pitch on the ER40 chuck is 1.5mm, which translates to about 16.95 TPI.  However, my 1952 Logan doesn't do Metric.  So, I did some calculations and determined that if I replaced the 48 tooth gear on the lead screw with a 51 tooth gear and set the gear box on 16 TPI I would get 17 TPI which seemed close enough.



Turns out I was right.  The commercial ER40 Nut from my set fit the new chuck perfectly.

Here's the ER40 collet set I bought on EBay.  It came with an ER40 chuck with an R8 shank which fits in my mill.



Testing the chuck with a 1/2" collet and a hardened 1/2" test bar run-out is measuring about .001", probably as good as I can expect with the chinese collet set that I paid about $125 for.

Chuck

[DICKEYBIRD]

Yup, I can't tell you how many 1.5mm ER chuck threads I've screwed up trying to get Mach3 Turn to cut & ended up having to straighten up using me ol' reliable manual lathe @ 17 TPI.

Also, keep your eyes open for an ER-40 ball bearing collet nut.  Those big 40 size collets take some big torque but a ball bearing nut will ease the pain.

[ColH]

Dicky beat me to it, the ball bearing collet nuts help heaps.
Here is a link to where you can get them from across the pond.

http://www.arceurotrade.co.uk/Catalogue/Collets/ER-Collet-Nuts-Wrenches-and-Spanners

Col

[ShopShoe]

Chuck,

Thanks for posting that. I need to make a flange type ER32 chuck for my minilathe so I am reminded to move that project higher up on my list of projects to do (If I can get past the life events that are keeping me out of the shop.)

I always enjoy your posts: Keep 'em coming.

--ShopShoe

[Roger B]

ShopShoe, Flange type ER 32 chucks for Minilathes are available commercially. As ever it's a balance between shop time and money. I made a ER 25 chuck for my Hobbymat as I couldn't find one to buy.

[cfellows]

Thanks for the comments, folks.  Shopshoe, the priority on this was bumped up for me by the fact that my old, 3-jaw chuck had so much runout it was mostly unusable.  So, rather than buy a new chuck, this seemed like a less expensive alternative.

Chuck