Collet closer

[threesixesinarow]

This is a lever operated collet closer I made for my 7x10 mini lathe. I copied from pictures of different models but made it smaller and for 3C collets. It can open and close with the lathe running and works great with my bar feeder.

Like many older designs it pulls the collet into the spindle to tighten it, with the lever mechanism at the far end of the headstock. The collet seats in a MT3-to-3C spindle adapter from Little Machine Shop, and the drawtube screws onto the collet and passes through the spindle, supported by a bushed adapter screwed onto the rear spindle threads, replacing the bearing jam nut.

The lever shifts a cam to spread three lever fingers that press against the end of the spindle and pull the collet into the spindle nose. I think like old Royals, and the Rovi shown below, the cone-shaped working surface is on the outside of the cam, and it has flats at both ends of the cone to limit the motion of the fingers and prevent it from releasing itself. Clamping force is pre-set by screwing the drawtube into the the collet and then locking it with a dog point set screw in one of the slots in the rear spindle adapter.

It has been reliable so far - I haven’t made very many parts with it but hopefully it will be durable enough for my purposes. The drawtube is a piece of 1/8” wall 1/2” mild steel DOM tube but many of the rest of the parts are harder steel and bronze.



main view with guards removed; closed and open



shell guard tapped for the indexing screw and the slots that goes in; rear spindle adapter with closer removed



most of the parts before it was completed; some unused and undrilled fingers





Here is a very short video showing the collet in use, with it opening to let work feed up to a stop.

[old_toolmaker]

threesixesinarow,

That is very, very nice workmanship on the collet closer. I am impressed! The lever style collet closer is indispensable for repetitive work. I had a 5C lever collet closer similar to this a few years back and loved it.
Thank you for sharing with us.

[threesixesinarow]

Thanks, Dick,

It’s very useful and fast for specific tasks - for me, anyways - I tried to make more than a handful of multiples using a 3-jaw chuck, once! But it’s limited and slow for more general stuff, so I pieced together a second mini lathe so I don’t have to remove it to use regular chucks.

The hardest part was making the lever fingers and the hub for them. I think some closers have two of those instead of the three I used (I think Schaublin, and even the the little Petermann automatic screw machine shown at lathes.co.uk)which might simplify things a lot.

I see Sherline sells a 3C lever closer now. https://www.sherline.com/product/302...r/#description I’m not sure but it looks like it works like the old South Bend one using modified ball thrust bearings instead of fingers for leverage from the cam.

- Clark

[old_toolmaker]

threesixesinarow,

I just found the plans you sent me over a year ago. I knew I had seen them before. Thanks!

[old_toolmaker]

threesixesinarow,

Clark,
Do you happen to know who makes the lever collet closer that uses the ball thrust bearing method?
I know my Logan used the three fingers.

[Toolmaker51]

Of all methods to operate collets, a lever is best. Against pneumatic, handwheels, or pinion gears, only the draw tube and lever can detects oversize/ undersize parts.

[marksbug]

ive been meaning to make a 5c one of these or modify one to fit my 9x20 , I do have a collet chick thats supposed to be stationary and had a handle that I could remove and add smaller lever that would work or just a wrench,the same unit Ive seen for mounting on lathes so I know it will do it. or I could shell out $140 for a new 5c chuck....but not in a big hurry I wish there was some octagon 5c collet blocks like the er collett blocks and had a nut on the end pushing agnist the collett instead of the 5c type with the closer on the end or the round nut on the rong end pulling the collet. but thats me Im kinda different.

[threesixesinarow]

threesixesinarow,

Clark,
Do you happen to know who makes the lever collet closer that uses the ball thrust bearing method?
I know my Logan used the three fingers.

I’ve only seen the oblique parts list drawings for the ball ones. I think this South Bend works that way.



I wonder if along with modified thrust washers you could use a tapered roller bearing cup for the cam.


Here are some of the two-finger designs I remembered - Brown & Sharpe, Gorton/Petermann, and Schaublin.

[threesixesinarow]

ive been meaning to make a 5c one of these or modify one to fit my 9x20 , I do have a collet chick thats supposed to be stationary and had a handle that I could remove and add smaller lever that would work or just a wrench,the same unit Ive seen for mounting on lathes so I know it will do it. or I could shell out $140 for a new 5c chuck....but not in a big hurry I wish there was some octagon 5c collet blocks like the er collett blocks and had a nut on the end pushing agnist the collett instead of the 5c type with the closer on the end or the round nut on the rong end pulling the collet. but thats me Im kinda different.

I looked up 5c collet blocks a while ago, hoping they might be more practical solution than making something from scratch. I didn’t find ones that were suitable for working with long bars - the affordable ones seemed to use nuts threaded onto the collet that then clamped it with a lever cam that blocked to bore - but didn’t really know what to search for.

I did see a video where someone fitted one of those key operated, nose mounted 5c collet chucks to a mini lathe - it looked like it stuck out about 5” from the end of the spindle!

I would rather install an ER chuck than that, I use those on my smaller lathe. You could make a lever closer for them, too - but something with a big hand tightener like a Rubberflex chuck might be a lot more useful.


This video about Kiyoshi Kato’s workshop that produces “Space man” pens has one of my favorite collet closer designs, first shown in operation about a minute in.

[old_toolmaker]

threesixesinarow,

Clark,
Thanks for the schematic drawings. That will sure help me while I search and think things through.