Er32 Collet Chuck

[WMello]

Just got a ER32 collet chuck adapter for the Mini Lathe from HHIP (code 3901-5032)
Got via eBay for $52.08 + $6.45 shipping. It's about half the price of the one sold by LMS


It looks beautiful.
Installed on the lathe yesterday without any care; it fits perfectly on the spindle flange.

Than shot this video:

Lathe Spindle Taper: 0.0006 TIR
Collet Chuck Taper: 0.0013 TIR
Collet Nut Taper: 0.0025 TIR

The last measurement is useless. The important one shroud be taken with a collet and round bar installed; measured over the bar. But I don't have any collet yet and the budget for this month is gone.

Normally I do this tests rotating the spindle manually. Did under power for the video just for show.

Did I do the measurements right ? What do you think of the results ?

Wagner

 

[RJSakowski]

Lathe Spindle Taper: 0.0006 TIR
Collet Chuck Taper: 0.0013 TIR
Collet Nut Taper: 0.0025 TIR


Did I do the measurements right ? What do you think of the results ?

Wagner

If it were me, I would measure the spindle taper a little further in. The collet chuck taper looks about right. The final word is what is the runout on a test bar close to the collet chuck and two or three inches from the collet. This will tell you about radial runout and angular runout. Keep in mind that this is a combination of runout from the backing plate, the collet chuck, the collet, and the test bar though. If it comes out with in your expected tolerances,fine; if not, you would need to diagnose the various contributors.

You didn't say anything about machining a back plate to fit. Did you use a preexisting backplate? If so did you check the face for runout and the registration boss for radial runout? If they are running true, then your .0013" measurement is out of line with the advertised runout of .0002". Tormach had a problem with their ER20 tool holders when I got my machine. They asked us to check the runout of the tool holder collet using pretty much the same measurement that you have made except we rotated the tool holder in a vee block. Anything over .0004" was replaced.

As I recall, collets that I have purchased generally have specified runouts of .0002" , as measured on a test bar near the collet chuck, and generally .0003 to .0004" at 10 cm from the chuck.

Bob

 

[kd4gij]

Check the register on the spindle and the mounting surface. That is where the chuck mounts. How tight does the collet chuck fit over the register? You may beable to losen the bolts a tad and indicate the chuck in. Goon luck.

 

[mksj]

Looked at this ER-32 chuck previously, it is very nice for the price and the through hole in the back should allow smaller stock to pass through (assume this is something like less than 3/4", I use 5C collets on the lathe only because it can holder larger stock, but 5C collets have a worse TIR). Your measured ER-32 collet chuck taper TIR is actually quite decent, although the nut (TIR) should not have an effect on the run out of the collet TIR. Agree with kd4gif, the TIR should be measured at the registration step on your machine (not sure of the mount between the lathe and the chuck), but this is about as good as it gets without a set-tru type chuck. Collets should have a TIR 0.0002-0.0004" depending on the quality. It is important that the ER collets are snapped into the ER-32 nut first, then the nut/collet threaded on the chuck and the rod/mill mounted before tightening.

If you are going to be using the ER-32 for odd size stock, you may consider getting a metric set of ER-32 collets, the collapsible range when using 1 mm steps overlaps better than a 1/16" increment sets.
Example ER32 19 PCS SPRING COLLETS SET 2-20mm ER32 Collet : http://www.ebay.com/itm/ER32-19-PCS...740?pt=LH_DefaultDomain_0&hash=item20e2afc9c4

 

[WMello]

Thank you all for the responses.

I did not machine a back plate. The collet chuck is made with 80 mm external diameter and a 55 mm recess in the back that fits the registration step on the lathe spindle plate (flange ?). It goes in place of the original 3" chuck and is secured with three M6 bolts.
I will measure again further in on the spindle taper and on the register of the mounting plate.

The chuck fit over the register pretty tight. I didn't recall any movement.

The hole on the chuck plate allow for a 3/4" bar to go through the lathe spindle bore.

Thank you for the suggestion about the metric collet set. I will go with that.

Wagner

 

[kd4gij]

Also check the collet chuck for burrs around the threaded holes and inside and outside of the mating surface. And the when indicating a tapper it will look worse than it is. If it is out the indicator will also be riding up and down the taper.

 

[RJSakowski]

Thank you all for the responses.

I did not machine a back plate. The collet chuck is made with 80 mm external diameter and a 55 mm recess in the back that fits the registration step on the lathe spindle plate (flange ?). It goes in place of the original 3" chuck and is secured with three M6 bolts.
I will measure again further in on the spindle taper and on the register of the mounting plate.

The chuck fit over the register pretty tight. I didn't recall any movement.

Wagner

Wagner,

I would check the runout of o.d. of the flange on your spindle as well as the face of that flange if you haven't done so already. If they are running true, you may have a bad collet chuck.

Bob

 

[WMello]

Update.

Got a set of metric collets (2 to 20 mm). But I'm a little disappointed.
Installed a 0.500 drill rod and the TIR was ok, better than on the 3 jaw chuck but not exceptional.

Than used it for real turning a piece of 3/4" brass. And the problems started.
It needs a humongous amount of torque for a good holding. And one needs three hands for the job; one to hold the stock, the second to tighten the collet nut and a third to lock the spindle (my lathe has no spindle lock). I will have to drill some holes on the collet adapter for a tommy bar.

The other problem, this one major, is on the metric collet set. ER collets are supposed to work on a range of dimensions, but on my experience (I may be talking nonsense), good grip is achieved only on the final portion of the range. The 3/4" test coincidentally was on the worst case; I've used the 20 mm collet, range 19 to 20 mm or 0.748 to 0.787"; so a 3/4" round bar is at the very beginning of the range and a lot of torque is needed to squeeze the collet; with this, TIR suffers.

Please see this table:



Also, holding a short piece of stock on the front edge of the collet didn't go well at all.

So, buying a metric set and relying on the "grip range" was a mistake.
Now, buy a fractional set, get a set of 3MT collets or go back to old trusty 3 jaw chuck.

Wagner

 

[mksj]

A good ER collet is suppose to compress along the whole collet, and not just the end, so its holding ability is not a percentage of the range. I have a used Iscar Er-32 set and have not had any problems. So may be the quality of the collets. 3MT collets? or 5C are worse as too their clamping range. I do alot of fractional materials and metric rod material, the ER system has worked well for me on the mill. I use a 5C on the lathe, but probably have 70+ collets to cover everything I need, and the cost was significant. You may not be getting the proper compression of the collet, there are ER32 nuts with a bearing in it, and makes it easier to tighten/compress the colle. If the collet does not meet spec, I would return them.

 

[Doubleeboy]

I have had Iscar ER-32 collet set with chuck for a decade or longer, they are great close tolerance but in my opinion a pain in the arse with the three hands needed to operate them. I much prefer my 5C collet closer or a set tru 5C chuck. I know well the weaknesses of 5C, but damn they work and you don't need to have and extra hand.

michael