Newbie Collet Question

mikey said:
Jon, how does an ER collet get sprung? Serious question. If used properly within the 0.40" clamping range I've never heard one can spring/sprung a collet.
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Over tightening and/or over torquing during use (too much feed and/or speed). Granted that may be "out of proper use" but in a shop full of people, the only person that ever made a mistake was "Not Me".
 
planeflyer21 said:
Over tightening and/or over torquing during use (too much feed and/or speed). Granted that may be "out of proper use" but in a shop full of people, the only person that ever made a mistake was "Not Me".
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Hmmm, I suppose you can crank down hard enough with the chuck in a fixture to overtighten it like that. I've been using ER collets for about 20 years and never heard you can spring one - learn something new every day.

I do know that an ER collet is most accurate at or near the larger end of its range. When you crank down on a smaller diameter, even within the claimed range of the collet, you lose accuracy. I figured this out while cutting a Woodruff key slot where being a tenth or two off is the difference between an interference fit and a slip fit. For that kind of cutter I now buy a metric collet if the tool shank is closer to the metric size than an imperial. It makes all the difference.
 
My iscar er40 collets are metric I believe, but list the standard dimension as well, like the 3/4 collet says 3/4 as well as 19-20 or whatever.
And over torquing? I suppose thats quite possible on the little guys (er16-25) but you'd be hard pressed to torque a 40 at max torque with the wrench that's supplied with the chuck.... especially if you change collets and tools while it's in the spindle
 
Yeah, I agree. Generating 135# of torque with a collet wrench on a spindle mounted chuck isn't easy to do, much less over-torquing it.
 
Hi.

The collet types mentioned are quite small - the ER25 go to only 16mm.

I would (and I have) go for a nice second hand set of Pratt-Burnerd multisize collets.

I have the EC type that go from 1/16" to 1½". The set consists only 12 collets as each collet has a wider range than others.

Pratt-Burnerd has larger collets, but these are the most numerous on the second hand market.

Cheers
Erik
 
Bill Gruby said:
With all due respect David V. The 5C collet is better in IMHO because of its thru the spindle capability. ER Collet systems can't do that, at least not that I am aware of. With that said I believe the 5C is the better choice.

"Billy G"
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The tool chucks have a blocked off end, the lathe chucks have a throug hole.

Stuart
 
Have you thought of making some jaw covers. these are very low tech lol. I bent up with some aluminum scrap from a door kick plate they've worked pretty good I pop them on and off very easily just a thought 20160402_233620.jpg
 
umahunter said:
Have you thought of making some jaw covers. these are very low tech lol. I bent up with some aluminum scrap from a door kick plate they've worked pretty good I pop them on and off very easily just a thought View attachment 126238
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I forgot a good point about using 5c collets. You can get soft 5c id collets from Hardinge or Rovi that will hold on the id of a part all the way up to 6 inch dia. Rovi is much cheaper. When I did production work I used them about 25 percent of the time. You can face and bore a part and then hold on the bore and reload many times to do other operations holding dead length and keeping parts concentric. You can also load parts with spindle turning if you have a lever collet closer.

jimsehr
 
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