# ER32 collet chuck lathe backplate



## Badabinski (Apr 2, 2021)

I've had an ER32 collet chuck hanging around, waiting for a backplate. I need to make a backplate for my Bison 6 jaw I bought, so I thought this would be good practice.

I bought some 3.5" ductile cast iron off of Mcmaster. Sliced off a bit, drilled it, bored it, and then single-pointed the 1-3/4" 8 thread that my lathe uses for its spindle nose. Machined everything, made the bolt circle, and put it together.




The runout is... Not great! With my 3/8" collet and an edge finder, I was getting 2.5-3 thou of runout. I haven't had time to figure out where the runout is coming from, but hopefully I can get that down a bit.

Pictured is my second attempt. The first time I tried this, I really screwed up the threads and scrapped the part.


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## markba633csi (Apr 3, 2021)

Don't be too quick to blame your machining- the chuck may be the guilty party
-Mark


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## DavidR8 (Apr 3, 2021)

Looks good!
I recently added a 5C collet chuck to my lathe. Came with a threaded back plate that I had to finish. 
It took several tries to get the backplate running true. 


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## Badabinski (Apr 3, 2021)

@markba633csi 
I also wonder if the runout is coming from my bargain basement collet set. I need to work on the backplate for my set-tru 6 jaw, but I'll investigate further once I've finished turning this stupidly large chunk of cast iron.



@DavidR8 
I had considered one of those! The main thing that stopped me was the sheer number of collets necessary. I should probably bite the bullet at some point though. I'll likely save up the spondulix for a Hardinge chuck and some nice collets, so I imagine that'll only take 10 years or so.

Threaded spindle noses are a real pain, aren't they? That's my second biggest issue with this lathe right now. Next lathe is going to have a D1 spindle nose so I can just buy a stinking backplate.


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## DavidR8 (Apr 3, 2021)

@Badabinski I hear you on the collet issue.
I use ER32 on my mill and I’m discovering that I need to fill in the size gaps so that I can use them for drilling too.
I went 5C on the lathe because I wanted to keep the ER32 strictly for tool holding.
One thing that is nice about 5C is that it grips at the front of the collet so short pieces of stock can be held. ER collets collapse along the length of the collet so gripping stock that’s not as long as the collet isn’t ideal.


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## markba633csi (Apr 3, 2021)

I would buy one good, name brand collet I trust for chuck fitting work like that.  A Rego-Fix or Technics, so you can eliminate the collet error from the equation
Yes they are expensive but it gives you a good reference point
-Mark


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## martik777 (Apr 3, 2021)

It's likely the cheapo collets. Turn the collet a few degrees and re measure the runout until it diminishes  - mine went from 3-4 to < 1 thou


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## mikey (Apr 3, 2021)

Badabinski said:


> The runout is... Not great! With my 3/8" collet and an edge finder, I was getting 2.5-3 thou of runout. I haven't had time to figure out where the runout is coming from, but hopefully I can get that down a bit.



Nice job!

You have a lot of interfaces that can affect your run out - the spindle, the spindle register, the accuracy of the back plate, the accuracy of the back plates male register, the chuck's female register, the chuck mounting holes, the chuck's internal taper, the collet and collet nut and the accuracy of the thing you stick in the collet. Any of these things can be the primary or a contributing culprit. Before spending any more money, my suggestion is to document precisely which one or more than one of these things is causing the run out and fix that/those things. 

It may be that a simple tap on the chuck before locking the chuck to the back plate will do it but you have to evaluate everything in this chain to be sure. 

Hobby machining is fun, isn't it?


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## brino (Apr 3, 2021)

mikey said:


> It may be that a simple tap on the chuck before locking the chuck to the back plate will do it but you have to evaluate everything in this chain to be sure.
> 
> Hobby machining is fun, isn't it?



........but it's knowing exactly how big of tap on what side of the collet chuck that's worth the big money!
-brino


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## Shotgun (Apr 6, 2021)

martik777 said:


> It's likely the cheapo collets. Turn the collet a few degrees and re measure the runout until it diminishes  - mine went from 3-4 to < 1 thou


Before you do that, hold them up to a light so that it shines through the slits.  Mine had pieces of swarf about an inch long in several slots.  I don't know that it caused them to be off, but I'm sure it could not have helped.  I cleaned them all out with a feeler guage.


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