Matting an ER40 Collet Fixture to a Back Plate

[ddickey]

I bought one of these https://www.tormach.com/store/index.php?app=ecom&ns=prodshow&ref=33286&portrelay=1
and a back plate. http://www.grizzly.com/products/6-1...397?utm_campaign=zPage&utm_source=grizzly.com
I see a problem in that the recess on the ER fixture 100mm. When I make my register on the back plate I will be going directly over the Camlocks. Would it be okay to turn down each camlock so it will not interfere with the mating of the two parts?
Is there a better back plate I should've bought?

 

[darkzero]

I also used a 6" back plate from Grizzly but mine is D1-4. However, the ER40 plates I have are 130mm. Seen here in post #37 . If you had the larger one you may have avoided your issue. Or use a thicker backplate which Grizzly also sells. But that's a lot more machining.

You could probably get away with shortening the threads on the camlocks as long as you have enough threads for them to still be adjusted & sufficient thread engagement. You would have to determine that as we can't tell from your pics.

 

[ddickey]

The project is complete and run-out is not acceptable, .0025" on the spindle taper. I broke a small drill bit off in the backplate when drilling pilot holes and that really screwed up the project. The recess I made fit very well but after I measured the runout I took a little off of the OD of the register on the backplate hoping to know the collet into round. It worked a little but what a pain. I reordered a backplate. Hopefully this one will be a little thicker where the camlocks are. I really struggled getting the holes aligned properly. Any tricks to this? Other methods? What about bolt hole circle calculations using teh mill and the DRO?

 

[darkzero]

Only the register from back plate to adapter is important, the bolt holes don't have to be perfect. Quickest & easiest way is to just mark them with a transfer punch & drill. Or use transfer screws if you have them or calculate bolt circle is fine.

Your project may not be lost. Is it radial or axial runout or both? Check the ER plate for runout first, axial & radial. If the ER plate is running out then making a new adapter won't solve anything.

You can fix axial runout on the ER plate by skimming the mounting face. Assuming you machined the register on your adapter while on the lathe it should be fine.

To fix radial runout on the ER plate you need to skim the register. By doing so your adapter will no longer fit snug & you would have to make an adapter. But not necessarily. I actually made mine so that the register is a slight loose fit, this allows you to use it as a "TAP-TRU". As long as there is acceptable axial runout, you just snug up the mounting bolts, tap the ER plate to run tru radially, then tighten the bolts.

 

[ddickey]

I'll have to do some more testing to check axial and radial.
Taking a skim cut on the ER plate sounds like a good idea.
If I have a chance in the morning after work I'll check it out.

 

[ddickey]

Run-out in both directions.
When you say "skim the register" do you mean reduce the diameter of it? Because the top of the register would make no difference as it is not supposed to make contact with the chuck. Is that correct?

 

[darkzero]

Correct, OD of the ER plate has no effect. Skim the back face of the ER plate for axial play. But in order to do so, you must use an accurate collet in the largest diameter possible with an accurate piece of stock mounted in the collet with the other end of the stock mounted in a chuck that you trust with minimal axial play. Hope that didn't sound too confusing?

Chances are the back face might be good as it should be ground. Mine was but of course anything is possible with China tooling. I used a 1" collet & a 1" piece of Thomson linear shafting. I can take a pic of what I mean if you'd like. And if you can setup this way, check runout first (before deciding to skim) a few times resetting each time to verify if you do actually have runout on the back face. You must be accurate as possible with this set up as there will be errors introduced by the collet, rod stock, & your chuck.

For radial play you would skim the ID of the register on the ER plate. But again doing so will cause a loose fit on the adapter you just made and again that is fine if you want to go with the tap-tru method I mentioned.

 

[darkzero]

You must be accurate as possible with this set up as there will be errors introduced by the collet, rod stock, & your chuck.

Better yet, chuck up a piece of 1" stock with enough stock for the ER collet to grip, skim the OD with the best finish that you can as possible. Don't remove the stock from your chuck after doing so. This will ensure the stock is true to your spindle & eliminate the error of any runout from your chuck.

 

[ddickey]

I should make or buy an MT3 or 5 with a longish blank arbor

 

[kd4gij]

How did you hold the back plate to machine it?