Re: [SherlineCNC] Re: What kind of run out should I expect to see
If you are getting a true 0.01 ~0,02 mm run out at the work piece , then I would be inclined to leave it alone and call it quits, quite happily. This class of machinery is not designed to be a tool room lathe or mill with a tolerance of 0.005 mm and the operator should learn to work around these limitations. I have spent enough time chasing after the unattainable 0.01mm run out, so please don't waste your time doing so.
If I make a simple comparison, I used to have a small photographic business in my younger days. I could not tell you how much time and money I wasted chasing after the last ounce of resolution that an emulsion and developer combination could provide, even more so in these digital age, and all quite irrelevant to the end result.
Many people claim to have 0.01 mm run out with the stock Sherline 3 or 4 jaws chucks, a very tall order if you consider that the Sherline spindle has about 0.01 mm of run out itself before you get into the errors of the mounting flange and the chuck. perhaps their machines are manufactured different to mine.
Sent: Tuesday, May 01, 2012 12:21 AM
Subject: [SherlineCNC] Re: What kind of runout should I expect to see
I get 0.01-0.02mm runout measuring outside the spindle. I think they are rated for 0.01mm runout for the low RPM spindles. Their higher RPM spindle have higher runout. Then again, the spindle OD might only be fabricated to 0.01mm precision even if it is concentric to the shaft.
I think the fact his end mill had lower runout is because it is threaded on, whereas the intenal taper of the spindle holds collets, and that can have a different runout than the threaded part of the spindle for end mill holders.
Entirely based on geometry, the actual runout can be much worse than these values measured close to the spindle assembly, especially if the tool extends a certain length.
The best way is probably to increase preloading of your spindle, then lathing a holder in place inside the spindle, so that it remains axially aligned. Its the same technique people use to machine olders using soft jaws for holding parts.
--- In SherlineCNC@yahoogroups.com, "Eric" <buckeyevs@...> wrote:
> Drill chucks should not be expected to have low run out. They should also not be used in milling operations because of this, and they don't hold as rigid against side forces.
> If a cutter in a collet held in the spindle is < 0.0005 then that sound pretty good. Try this instead of an endmill holder. Your "on the spindle" reading is bad, but contradicts the measured run out of the holder held tool, which is the important thing.
> As for the ER collet chuck, there is a lot that could be going on here to result in that much run out. Dirt/chips/damage between the collet and chuck can cause all kinds of degree of run out. Dirt between the spindle and collet chuck is another possibility. Then there is quality. I don't have one and can't speak on that or give comparison values.
> Measuring inside the spindle gives you an idea of it's condition. However, measuring a tool shank in the holding condition and measuring at the collet and a distance away from the collet (while marking high indicated point in each spot) will give you a good picture of the error. If in line and of equal value then it is simple run out likely in the spindle. If not then it is possible that a poor quality collet is the cause, or damage/debris causing the run out.
> --- In SherlineCNC@yahoogroups.com, "James" <sdrc92126@> wrote:
> > I've just gotten to the point where I'm starting to care about this stuff (after ignoring it for years). I broke a small endmill and upon close examination noticed that my jacob's chuck had a very noticable wobble.
> > I put a TDI on the spindle and get a reading of ~0.001"-2" on the inside. A mill in the endmill holder gets less the 0.0005" on the shank. I also just got an ER16 (micromark) holder and see maybe 0.003"-4" right at the end of the collett.
> > I guess my questions are, is the acceptable (or should I say expected. If not, is there anything I can do about it, eg, replacing the headstock, replacing the spindle, filling down the collet, etc. I should also mention that I dropped the collet holder with a bit in it and accept that I could have ruined it and will probably get another.
> > I'm not a machinist, but I've been playing with this on and off for a few years and have been trying to learn as much as I can lately. I'm not really sure where measurements are taken (inside the spindle, outside, on the threads, on the chucked part, 1" below the chucked part, etc.). The ER16 sticks out a couple of inches below the spindle, so I'm sure this is adding substantial error.
> > Thanks for any information.
> > j
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