Didn't expect to see this

[WobblyHand]

This morning, I hesitated in drilling the chuck body. I had wanted to put in a few holes for a tommy bar. In a turn of fate, I couldn't fit the both the backplate and chuck in my 5" dividing head chuck. So I decided to install everything on the spindle to do some preliminary runout measurements. And then I discovered the plowed field in the taper. Good thing I didn't drill the chuck, might have made a return a little tougher.

 

[jaek]

Glad there's a happy ending here. I'm still curious what the actual runout of something held in the chuck is going to be...

 

[macardoso]

I got some import ER20 collect chucks for my TTS system that looked like that. After some careful inspection, I realized the entire holders were hard turned, likely with a PCBN insert on a lathe. Nothing wrong with that IMO as long as it is done well. Seems like on 2/10 of my chucks, the insert chipped partway through the cut and the finish got real bad - like the image above. Go them replaced with good units.

 

[WobblyHand]

Got a replacement set tru ER40 chuck from discount_machine (Shars). It's much better. No grooves in the taper.

Dialed in the ER40 long taper runout to 0.0001". Good enough for me. Undoubtedly better than the collets I bought. I measured 0.0005" TIR on a ground 20mm rod. Not sure if the rod is contributing, but will measure it for grins. The collets themselves are guaranteed to be less than or equal to 0.0005". If I can regularly have these kinds of low runouts, I'll be happy.

@jaek I'll never know what the other chuck's runout is. I boxed up the reject chuck and will return it to discount_machine today. They provided a free shipping label and I am reusing the shipping box. I'm glad to get that chuck out of my house.

 

[macardoso]

Techniks makes the best ER collets IMO and while expensive, their reliable TIR is absolutely worth it. Sometimes you can shop around for better deals on them

 

[WobblyHand]

Techniks makes the best ER collets IMO and while expensive, their reliable TIR is absolutely worth it. Sometimes you can shop around for better deals on them

I bought the metric full set to have complete coverage. Most imperial sets have gaps. Plan to fill in "popular" imperial sizes, especially sizes that have too much collapse, probably with Techniks. If I need a very good imperial fit, or I find I am using that size a lot, I will buy that imperial collet.

 

[macardoso]

I bought the metric full set to have complete coverage. Most imperial sets have gaps. Plan to fill in "popular" imperial sizes, especially sizes that have too much collapse, probably with Techniks. If I need a very good imperial fit, or I find I am using that size a lot, I will buy that imperial collet.

If you really need good TIR with ER collet systems, They make “zero size” collets which are only supposed to contract 0.0005”. They’re great for tool shanks and stuff like that. Normal ER collets guarantee 0.0004” while the high precision “zero size” ones give 0:0001”. Bit more expensive but not too bad.

 

[WobblyHand]

If you really need good TIR with ER collet systems, They make “zero size” collets which are only supposed to contract 0.0005”. They’re great for tool shanks and stuff like that. Normal ER collets guarantee 0.0004” while the high precision “zero size” ones give 0:0001”. Bit more expensive but not too bad.

Good to know.

Just rotated the collet by 180 degrees relative to the chuck, but maintained the position of the rod to the collet. Measured 0.0002" TIR. Might be the collet, or I dislodged a tiny piece of crud. Not complaining, these collets should be fine for 99% of what I need to do. The last 1%?, don't know if I will ever be that good of a machinist, but it's good there's a fallback if required.

 

[WobblyHand]

DTI centered on top of rod, measuring TIR. Measurements written on backplate is the approximate amount of radius reduction needed to match the chuck. I'll take off 0.010" and remeasure.

Pretty happy with this backplate. Machined it from a solid disc of cast iron. First backplate I have ever made. If you told me two years ago I'd be making my own backplates, I would have laughed out loud at how impossible that would be for me. Not any more!

 

[Toolmaker51]

I have heard from Shars. They will send me a replacement with a pre-paid return label. They apologized for the issue, and the inside finish. They said, "We have never seen an er40 collet chuck with a finish like that." Me either. Hope to get the new one soon.

Sure, could be a fluke, but I've never heard they conduct 100% receiving inspection from suppliers...and there likely are buyers who haven't a clue what to expect in a hardened and ground surface.
Why 'we' keep a genuine copper penny in the toolbox. Drag it over a surface, if it marks, that isn't a 32 or better. I'd guess most spindles and collet seats are 16 or less.

If you told me two years ago I'd be making my own backplates, I would have laughed out loud at how impossible that would be for me. Not any more!

I participate elsewhere; one of the forum asked another "is there anything you HAVEN'T done?" The answer, "Yes heart surgeon, multi engine pilot, politician...". But what he HAD done, was simply stepping up and giving it a go.