Make Your Own ER11 Spindle

[bergerud]

We are talking about the $15 collet extension chucks on eBay. They seem to have a concentricity problem (axis of taper and of axis shank not parallel). I was told by a supplier " The shank is ground centreless and the taper is ground spinning the chuck held by the shank so it is nearly impossible not to make it concentric". Well, I guess the machine chuck which holds the collet chuck shank is not so true!

The beauty of this conversion process is that these problems can get fixed if you turn both bearing journals. The taper is the "face side" that you start with. Using a high quality collet, you hold the cheap collet chuck by the bit and turn it to be concentric. If done carefully, the cheap collet chuck can become as accurate as the high quality ones.

Somewhere, I saw collet nuts which had a bearing in them. The idea was that the bearing eliminated the torque on the collet due to friction when tightening. I suppose one would like an even shorter wrench for these.

[bergerud]

I am pretty sure they are all hollow. I brazed plugs in the ends. I did not care about the effect of heat because I later turned the shanks down.

[mister_zed]

I am pretty sure they are all hollow. I brazed plugs in the ends. I did not care about the effect of heat because I later turned the shanks down.

OK, "brazed" implies quite a lot of heat, which will require machining. How did you make the square opening?

[bergerud]

How did you make the square opening?

By hand with a small square file.

[mister_zed]

By hand with a small square file.

Ouch! Making it perfectly centered must be areal pain the a.., isn't it?

Anyway, I might give it a try now that I have disassmbled my second Z-truck. Thanks for your advice!