Thread: ER32 Collet chuck - where to buy

The principal is the same.
Through holes are not a problem.
Threading to a shoulder present more of a challenge.
Tracking the Thread can be a bit more difficult.

Welder, internal threads are indeed a little more demanding, for several reasons:

- you do not directly see what the tool tip is doing, because it is hidden inside a bore.
- that makes threading to a shoulder twice as difficult
- chips remain inside the bore and may get tangled by the tool
- the threading bar is longer and much more fragile and flexible than an outside threading tool. It will flex, and you may have to take several spring cuts to compensate
- a round shaft threading bar needs not only to be set to center height, you also have to rotate the bar in its holder to the correct position
- if an outside threading tool binds, the depth of cut automatically reduces and the problems eases itself. But iIf an inside threading tool binds, it is pushed ever deeper into the workpiece causing chatter and potentially tool breakage or damage to the workpiece

To ease threading to a shoulder, one can run the spindle in reverse and use the tool upside down. That works exceedingly well on a lathe with camlock chuck mount. But Hercus uses an old threaded chuck mount, and such chuck can come loose when run and loaded in reverse.
Threading bars made of solid carbide flex much less than threading bars made of HSS or steel with a carbide insert. Chris

Here is one I made for the very uncommon 1 5/16" x 10TPI spindle nose on my Brackenbury and Austin lathe. I bought the nut.

I drilled the blank through 3/4" first, then bored the spindle nose end to the correct size and cut the register section and the runout groove for the threading tool, then cut the internal thread for the spindle nose. I left it in the chuck and unscrewed the chuck to test the new thread for fit on the spindle nose a couple of times when the thread was getting close to finished size. I used a long travel dial indicator against the saddle to show when the threading tool had entered the runout groove at the end of the thread so the half nuts could be disengaged.

The chuck blank was then screwed onto the spindle and the outside turned true, then the M40x1.5 thread was cut for the collet nut.

The compound was then set to 8 degrees (to give the 16 degree included angle for the collets) and the taper bored. When a reasonable length of taper had been bored it was checked for accuracy using a blued ER32 collet with a piece of steel the nominal size of the collet's capacity inserted for support in case any adjustment to the taper angle was needed. This showed the angle of the taper to be correct, and it was checked again several times as the taper approached finished size.

The two spanner flats 44 mm apart were then cut on the mill to match the flats on the mill's ER32 chuck so the same spanner could be used.

The finished chuck consistently shows no movement of the needle of a 0.001 inch dial indicator reading taken in the chuck's bore.

Frank.

Nice work there Frank . I hope mine turns out something like that, but there will probably be a few attempts before I get it "right "

If you have the time, could you maybe draw up a basic drawing showing the dimensions of your design ?

I have seen the nuts for sale on Epay . I guess you bought one ?

Mike

Franco,
Nice. You have inspired me to make one.
Graeme

Mike,

I bought my collet nut from Minitech because his price was a bit better than H & F, but most of the machinery merchants carry them, and, as you say, they are available on e-bay, often considerably cheaper. If you don't already have one you will also need a suitable collet nut spanner.

The dimensions of mine won't necessarily suit your lathe, because mine has a much smaller headstock spindle thread diameter, so a sketch of it probably wouldn't be much help. My spindle nose is 1 5/16" diameter and one inch long. Your chuck dimensions will be governed by your spindle nose length and diameter, and the depth of the recess for the ER32 collets.

The dimensions of mine are:
Outside diameter 50 mm
Overall length 60 mm
Depth of collet recess taper 30 mm
Length of nut thread 20 mm including the runout groove
Diameter of the large end of the collet recess taper is 32 mm

The standard ER32 nut thread is M40x1.5.

The minimum overall length of yours would be spindle nose length plus 32 mm for the collet depth plus a bit of working room for the headstock spindle thread runout groove etc, say another 8 or 10 mm. In mine the distance from the end of the H/S spindle thread to the bottom of the collet rececss is only about 3 mm because that was governed by the length of the piece of material I had. Another 3 or 4 mm of working room would have been nice when machining it, but the overall length is best kept as short as possible.

Since your headstock spindle thread is nearly 45 mm in diameter you might want to go to a bit bigger outside diameter than 50 mm for extra strength.

Good luck with making it. There is nothing really difficult about it - it just takes time, and a bit of care cutting the two threads.

Frank.

I made an ER32 collet chuck for my Hercus based on a Harold Hall design and modified to work on the Hercus. I bought the nut because the price was cheap and there was a lot of work in making one. Here's the drawing I used to make mine. Hope that helps.

Originally Posted by wannabe

I made an ER32 collet chuck for my Hercus based on a Harold Hall design and modified to work on the Hercus. I bought the nut because the price was cheap and there was a lot of work in making one. Here's the drawing I used to make mine. Hope that helps.

Well drawn out and just what we needed . You must have done some mech. drawing at high school ? I did it for 3 years 1968 to 71 . Comes in handy all these years later .

Mike

Originally Posted by morrisman

You must have done some mech. drawing at high school ? I did it for 3 years 1968 to 71 . Comes in handy all these years later

Thanks. I did tech drawing at school. After that, in a past life I was a carpenter so there was a fair bit of drawing involed with the trade course and also later in the Clerk of Works course.
What's not shown in that drawing is that I also knurled the larger diameter.