5C Collet runout

Beckerkumm

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My Smart Brown 1024 has a 5C spindle and drawbar. Measuring the runout with new Lyndex collets which should be decent and a gage pin of .25" I get .001-.002 runout depending on whether i measure within 1/2" or 1". That seems like too much but I have no reference for what it should be. While it is nice to have the 5C spindle, the area near the headstock has the least wear so although when using a chuck I can maintain less than .001 variation over a respectable distance ( .0005 over 6" ) and less if using a live center, there is .001 variation when using the collet of .001+ over the 2" nearest the spindle.

The 1024 has a D1-4 camlock which has three screws between the cams but they don't seem to affect the runout so I don't see anyway to adjust the accuracy. Any suggestions or advice is welcomed. Thanks, Dave
 
Given that I have no idea what a Smart Brown 1024 is, that seems like around the limit of what could be tolerated. For example lately I have been curious about runout on the KWIK-SWITCH quick change mill tooling I acquired, so stuck a dowel pin in a (whatever they call it, Acu-flex or such) and was pretty amazed to measure 0.0001 TIR right where the dowel and collet meet. This is no doubt a fluke, perhaps cancelling errors? We’ll see if this holds up with other tool changes.
 
Check your setup. Remove everything from the spindle and check the runout on it (check inside the mouth). Then add in the collet closer and check that. A burr, or swarf can give you results like this.

A good collet should have a runout of <0.0003".
 
Bore is clean, collets are new and I used several for comparison. the mouth of the bore shows runout as well so I'm quite sure my numbers are real. I received info from a couple of Smart Brown owners ( you can look up the lathe on www.lathes.co.uk ) and they both had collet runout of a few tenths. Dave
 
well, like slk001 said, check everything first. just go over the basics.

do you have other collets? are they within spec?

clean those threads out on the draw bar with a wire brush.
get a round stone and run it gently in the bore, both down the tube and on the chamfer by the mouth... gently.. you are looking for that slight raised section.

soak those new collets in paint thinner... get all the crap off of them. A stiff small brass brush to clean them out.

try other size pins.. did you try other .25 pins?

I don't doubt that the 5c has problems, but do ALL, if all do, I still would concentrate on the spindle and draw bar until I was sure ...

do you have a test indicator with a long probe.. if you do, it should show less than 3 or 4 tenths over it's bore as you are rotating.
if you show anything more, inspect that area... I have a mit test indicator it only does .001 but it shows less than easily because of the spacing... it has a long stylus....

edit: sorry, you show runnout on the mouth of the bore? how much... that's critical
 
...the mouth of the bore shows runout as well so I'm quite sure my numbers are real...
If you say that the bore (bore of what??) shows RO as well, then perhaps you have a spindle bearing issue.
 
Can you perform a DTI runout on the spindle itself ?
The collet can only make the spindle runout worse (98% of the time).
 
When I say I tested the bore I meant using a test indicator. I don't have a long needle so the test was just inside the opening. I'll test again tonight with my Interapid as it reads in imperial and I don't need to convert in my head like my Metric one. I will also check the collet when lightly tightened and again when the drawbar is fully tightened to see if that increases the problem. The nut on the end of the bar can cause problems if not perfectly flat so it pulls the bar slightly cocked. Parts of the drawbar have been remade but I do believe the test indicator showed the same issue but I'll quantify it. Dave
 
I spent more time and brought the good interapid test dial with long needle and tested spindle. Turns out I couldn't find any area of the bore off more than .0002, most of the time I couldn't see enough movement to even get .0001. Other indicator is cheap and jumpy but the real problem was me being stupid and forgetting a decimal when converting .01mm- .0004, not .004. There still is runout with collets but my my readings vary. I found that pin gages are not a very good way to measure. The diameter might be correct but they must not be made as straight. I went to endmills because that is what I have. The runout varied from .0015 @ 1/2" from collet to .0002 depending on endmill with the larger diameter having less runout.

The pin for the collet is broken off inside the spindle and i did find some grit jammed in the hole that I removed and did run a little diamond file over the pin hole to make sure it wasn't rough. I also still need to check the drawbar as the part that seats to tighten the collet is not original. I will check it to make sure the pressure is even. That could be why the small diameter seem to deflect more than the large. At least I feel good that the spindle is not the problem. Easier to deal with the other stuff than remove the spindle on this machine. Dave
 
The runout varied from .0015 @ 1/2" from collet to .0002 depending on endmill with the larger diameter having less runout.

Is this what you meant to say? ".0015 to .0002", or "00015 to .0002"?
 
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