ER32 collet chuck for lathe...

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Harold_V
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Re: ER32 collet chuck for lathe...

Post by Harold_V » Sun Oct 30, 2011 3:21 pm

John Hill wrote:I will test the perpendicularity when I find, or make, a suitable bar but until then I will continue to fret and chew my finger nails! :lol:
I hope you are accepting my comments in the spirit they are offered. Having worked as a toolmaker for years, I'm well aware of the tiny things that control the outcome of tool modifications. Once you move to dimensions measured in tenths, it becomes rather difficult to keep control, in particular when you're trying to generate surfaces that really beg to be ground. Your results are impressive, and I concur----well done.

If you make the decision to make a test bar. make it between centers. Because you're looking for miniscule differences, it must be quite precise. Turning by chucking, with the use of a center, isn't in keeping with good practice and can yield a less than straight and round bar. A ground bar would be preferred, but don't trust any *ground* stock, which often has been ground in a centerless sander and may or may not be round and straight (drill rod comes to mind).

The bar you make can have slight taper ( a few tenths, max), for what you're looking for is just differences in readings (TIR). If you can duplicate the .0003" reading a distance away from the collet, perpendicularity was not lost, and you have a simple concentricity issue. It is then a judgment call, if you feel it is close enough for your use, or not. Less would be desirable, but it is certainly functional as is.

If the reading is different, before concluding that perpendicularity was lost, remove and replace the bar to see if the readings are duplicated. If they repeat, you can trust the results. If not, explore to see why they do not. Remember, what you're looking for is quite small---so don't discount the slightest thing.

Harold
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John Hill
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Re: ER32 collet chuck for lathe...

Post by John Hill » Sun Oct 30, 2011 4:07 pm

Harold_V wrote: I hope you are accepting my comments in the spirit they are offered. Having worked as a toolmaker for years, I'm well aware of the tiny things that control the outcome of tool modifications. Once you move to dimensions measured in tenths, it becomes rather difficult to keep control, in particular when you're trying to generate that really beg to be ground. Your results are impressive, and I concur----well done.
Harold, thanks for your comments and assistance, it is for the very reason of taking advantage of the skills and experiences of others that I come to these sites, plus of course just a little modest bragging when things go well for me! :lol:

I am a bit of a worry wort when something is not completed and I could not sit by the TV last night without getting and going out to the shop (fortunately it is only one door way!) to address the concentricity which was way off, so now I need to check and if needs be address the perpendicularity.

spro
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Re: ER32 collet chuck for lathe...

Post by spro » Sun Oct 30, 2011 9:20 pm

The torque spec for a ER32 nut is 100 ft lbs. That is for tool holding and may be for proper grip, but it may also need considerable torque for proper seating of the collet for concentricity.
don't thinkso. Collet wrenches are generally under 1' . It takes a 2' lug wrench to apply 85 ft lb to a lug nut on my truck.

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GlennW
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Re: ER32 collet chuck for lathe...

Post by GlennW » Sun Oct 30, 2011 10:00 pm

spro wrote:don't thinkso. Collet wrenches are generally under 1' . It takes a 2' lug wrench to apply 85 ft lb to a lug nut on my truck.
http://www.techniksusa.com/metal/torque_chart.htm
Glenn

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John Hill
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Re: ER32 collet chuck for lathe...

Post by John Hill » Sun Oct 30, 2011 11:19 pm

I turned a test bar from stainless shafting, it is 22mm diameter with a section at the end turned down to 20mm to fit my largest collet. There is about 180mm sticking out when it is in the collet. I turned it between centres having first turned a new centre on a piece of scrap in the chuck.

Measuring run out at 150mm from the chuck I get 0.01mm to 0.06mm depending on where the bar is positioned in the collet.

Assuming the test bar is more accurate than the collet chuck and considering that the difference between best and worst position is 0.05mm I think the error in the test bar is about 0.025mm and the error in the collet is about 0.035mm.

Obviously neither the collet chuck nor the test bar are perfect so maybe thats as far as I can go unless I can get or make a better test bar. :roll:

spro
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Re: ER32 collet chuck for lathe...

Post by spro » Sun Oct 30, 2011 11:28 pm

I actually came back to remove my post and send you a PM. I see the chart i just don't believe it. Look at the CAT 50's and see the torque on collet there. Inch lbs maybe on the smaller ER's.

Harold_V
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Re: ER32 collet chuck for lathe...

Post by Harold_V » Mon Oct 31, 2011 1:04 am

John Hill wrote:I turned a test bar from stainless shafting, it is 22mm diameter with a section at the end turned down to 20mm to fit my largest collet. There is about 180mm sticking out when it is in the collet. I turned it between centres having first turned a new centre on a piece of scrap in the chuck.

Measuring run out at 150mm from the chuck I get 0.01mm to 0.06mm depending on where the bar is positioned in the collet.

Assuming the test bar is more accurate than the collet chuck and considering that the difference between best and worst position is 0.05mm I think the error in the test bar is about 0.025mm and the error in the collet is about 0.035mm.

Obviously neither the collet chuck nor the test bar are perfect so maybe thats as far as I can go unless I can get or make a better test bar. :roll:
Interesting. Your results, more or less, duplicate my Hardinge-Sjogren collet head. I'm not happy with that amount of run-out, but it is functional. When I require a higher degree of precision, I turn to soft jaws.

Part of the problem with a lack of repeatability can be the collet, or the item you made. It may have a miniscule high spot that permits the bar to grip in various positions. That's why a ground surface can be superior.

You may wish to try twisting the bar as you snug the collet, to ensure it isn't leaning. That's a pretty good method when you have doubts. It will also reveal a high spot, should one exist.

Having considered the results, it may be safe to say you have altered registration ever so slightly. Hard to say with certainty. In any case, once you know where you are, it's pretty easy to make a correction, assuming that's desirable. A little math gets involved, but you can determine which portion of the flange must be reduced, then dial in the flange with that portion high by the amount you wish to remove. A grinder would make it much easier, but it can be done on a lathe, with care. Or, you may wish to use it as is. :wink: It isn't horrible, not by a long shot.

Harold
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John Hill
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Re: ER32 collet chuck for lathe...

Post by John Hill » Mon Oct 31, 2011 2:10 am

I have a tool post grinder, that I made myself......
Image
two spindles by aardvark_akubra, on Flickr

Maybe I can give the base a lick with that.... :?

Harold_V
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Re: ER32 collet chuck for lathe...

Post by Harold_V » Mon Oct 31, 2011 3:28 am

John Hill wrote:I have a tool post grinder, that I made myself......
Maybe I can give the base a lick with that.... :?
Certainly worth a try! (Nice looking grinder, by the way!)
From your comments, I gathered that the piece is heat treated, which is what I'd expect. An aluminum oxide wheel would be the best choice, for sure. Were it soft, I'd suggest a rather hard wheel M or even an N, but make it somewhat softer---in the range of J or K. While finish is a requirement, you'll likely grind dry, so make your choice a little on the coarse side, say a 46 grit wheel. It won't cut quite as hot as a fine wheel, yet will yield a very acceptable finish, one that will register properly. I would not use a wheel finer than 60 grit in any case, not without coolant. Also, it may pay to remove the bulk of the error by machining, leaving just a couple tenths for grinding, which will minimize heating.

Once you've figured out the setup, dress the wheel with a diamond, and make sure it is ON CENTER. Any deviation from center will manifest itself in a slight taper dressed on the wheel, which will leave feed marks that aren't desirable. That would not be true if the centerline of the wheel is at a right angle to the spindle, and is dead horizontal. Make sure you mask the machine well, so you keep the swarf away from critical surfaces. I'm not a fan of grinding on lathes or mills, although I have done so myself. One does what is necessary, along with taking the correct precautions to limit damage.

I'd suggest this operation only after you have assured yourself that the perpendicularity is, indeed, off. It may not be, so eliminate any other possible reasons for the uneven and unreliable reading you're getting now. As I said previously, now that you're looking for a few tenths, it can be difficult to isolate the real cause. I witnessed two circumstances where, even with prolonged study, the cause of misalignment was never discovered. One of them, on a Excello four headed boring machine, was exasperating. Everything checked out perfectly, yet it turned out work that was eccentric (just a couple tenths, which was all the tolerance at our disposal). We never solved the problem.

Harold
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spro
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Re: ER32 collet chuck for lathe...

Post by spro » Mon Oct 31, 2011 3:55 am

Neat TP grinder!..No question about that. I need to clear something up about the torque recommended. This to where neither GW nor I are excactly wrong about this. I neglected to notice that for each collet nose there is a recommended "TORQUE ADAPTER". That is not to say that anything close to 100 lbs torque is applied. Depending upon the increase of length of this adapter the measured torque at the wrench goes differently. now back to science like the previous post. :)

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GlennW
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Re: ER32 collet chuck for lathe...

Post by GlennW » Mon Oct 31, 2011 7:08 am

Trying not to highjack the thread...
spro wrote:I see the chart i just don't believe it. Look at the CAT 50's and see the torque on collet there. Inch lbs maybe on the smaller ER's.
What you see there is the recommended torque for the set screw that locks the end mill in place on side lock end mill holders when using Weldon style end mills.
spro wrote:I need to clear something up about the torque recommended. This to where neither GW nor I are excactly wrong about this. I neglected to notice that for each collet nose there is a recommended "TORQUE ADAPTER". That is not to say that anything close to 100 lbs torque is applied. Depending upon the increase of length of this adapter the measured torque at the wrench goes differently.
It makes no difference what the length of the adapter is. The torque on the nut is what is specified, not the wrench setting. You would do the calculation for the adapter to achieve the proper torque on the nut.
Glenn

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ARM
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Re: ER32 collet chuck for lathe...

Post by ARM » Fri Nov 11, 2011 5:01 pm

JOHN HILL Esq
At the outset permit us to say Hello as newbie to the Forum.
We think we have found an most appropriate place to air our thoughts comfortably, without being condescended to.
May we please ask U and the the other kind Gents here for a few pointers on the ER 32 Collets which U would have now used.
We note from Your pic that the Chuck U have is the one from OPTIMUM.
Co-incidentally we are thinking of getting one of their machines, specifically the Model D 240 x 500 DC Vario and we were wanting to install a 5C Collet Chuck. However, we don't think we would be able to procure a compatible Chuck from the USA, or elsewhere as we had initially hoped. Their spindle mounting holes are metric designated and our Supplier needs a specific ADAPTOR made up to cope with their dimensions. As rookies we won't venture that far. We are now left with either the ER 25 and ER 32 Collet Chucks which they supply for this Model machine. The big question worrying us is whether we would be able to work up close to the face of these ER Collet Chucks. We will be turning tiny articles and would need get up real close working in the 2-3mm ranges. From what we have seen and liked of the 5C Collets is their convex shape which would permit one to get up real close to the Collet face for the kind of work we are contemplating.
We have not seriously looked at Europe for suitable 5C Collet Chucks and don't know if they are available there.
Do U have any suggestions for Suppliers ???
The other question would be does anyone have knowledge and or first hand experience with these OPTIMUM Machines ???
Are U totally satisfied with Your ER 32 Collets, barring Your accuracy installation setbacks ???
We would immensely appreciate some info on the above and thank You kindly in anticipation
kindest regards
ARM

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