Friday, 4 August 2023

Checking out the speeder - was it worth it?

Hold on, Fatty. There's more space between the spindle nose and the end of the quill than you'd thought. So the speeder will still leave plenty of room for the reaction arm without any need for butchery.

Phew. But - what's the runout like? The whole point of this thing is to enable the use of small cutters at speeds above 6000rpm and those cutters are even more intolerant of runout than "normal" sized cutters. So, to prevent breakages, I need to be seeing runouts in the 10-20um max range.

Ooof - that's basically 0.25mm runout, which is too crap even for drilling. WTF??

What about the Autolock chuck itself? Hmm, that's about 10um or so which I could just about tolerate.

But no matter how carefully I set up the ER11 collet, I can't improve on 200-250um runout.

Here's a nice quality 16mm drill. It should be a good fit with the Autolock collet. TBH it's rather loose.

It's actually not far undersize compared to the free movement, so the slop is mostly in the collet itself:

And the ER11 adaptor is even closer to nominal at only 17um undersize. The Autolock collet is clearly a fair bit oversize. It's marked as a metric collet, so clearly the correct size for a 16mm shank. The way it works is that the thread is always 20tpi, with a metric diameter that's the same as the cutter shank. Thus my ER11 adaptor should have a thread of 20tpi x 16mm.

I don't have any simple means of checking how much runout there is between the adaptor outer diameter and the internal ER11 taper of the collet. However, the Autolock chuck is in good condition and is surely capable of much better runout than 200-250um. I have to conclude that the adaptor is most likely responsible for most of that.

The answer as always lies in the internet, ideally in a web store. In this case, a straight shank collet chuck with 16mm diameter shank. I may as well go for an ER16 size, as I have more collets in that size and it would give me a greater choice of usable cutter diameters.

The plan will be to cut the shank down to length, then either thread it directly 20tpi x 16mm or turn it down to a small enough diameter to allow me to bond a 20tpi x 16mm threaded body on the end (if the shank is too hard to single point thread). At least this way, I should be reasonably confident that the collet and shank will have fairly low runout.

The speeder saga has some distance to run yet....

No comments:

Post a Comment

Rust eater?

What? I've had to do some derusting on a variety of components recently and it seems to be an expensive and/or hazardous and/or labour i...