Acceptable run-out on mill?

Just measured the mill run-out at 0.04mm on the cheap chinese MT2 arbour measured just above the collet

Would this be considered an acceptable figure?

Or should I replace the arbour?

Many things can cause runout.

Does that figure remain constant when you rotate the arbour 180 degrees ? Have you checked runout directly on the bore of the quill ?

I would have thought that was a reasonable expectation on a "cheap Chinese" arbour. Or the arbour could be perfect and the runout is in the quill.

regards

Andy, better to check the internal taper at both ends for run out, should give you a better indication of truth.

If excessive runout ensure all tapers are clean.

Emgee

Measured there it's probably spindle runout rather then the arbour - try measuring the spindle bore.

As emgee says it may well be dirt.

Schlesinger limit for the spindle taper is 0.01mm TIR just inside the taper.

Neil

Thanks to all - I'll clean and recheck accordingly

If the Schlesinger limit is 0.01 mm what does that say for a runout of 0.04 mm? Is this excessive, acceptable or quite good? And how much would it matter in the real world? Just curious. ...

All fair questions.

You can argue the real world performance of a tool is more important than these tests. A flimsy lathe might meet very Schlesinger test, but be hopeless when used, while good operator may be able to compensate for a worn machine and turn out accurate work.

Neil

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This brief extract from Schlesinger's Introduction might help:

You pays your money and you takes your choice !!

MichaelG.

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P.S. 0.04 exceeds 0.01 by 300%

Edited By Michael Gilligan on 05/01/2018 22:04:49

What actually matters is the runout at the cutting edge of the tool, not just at the body of the chuck. If your cutter is 2 flute and the feed is 0.025mm / rev, then 0.05mm runout may result in one tooth taking all of the cut. That's more serious than the slight increase in effective radius.

As noted by Richard Gordon in a short MEW article a couple of years ago, in some cases you can finesse the runout but gently tapping the tool during the tightening. However, in this case you would be better to get a chuck with sensible runout limits to begin with.

I measured one of my ER32 chucks mounted in the spindle yesterday and found the runout on the tapered bore was around 6-7um. But with an "experimental" purchase of Xmas Cracker collets from Aliexpress (£24 for 9!!), the runout at the cutter was closer to 50um (0.05mm). That's only good for holding blacksmiths drills but I can't pretend I was surprised or particularly disappointed. With a "proper" collet or end mill holder, I seem to be able to get runout typically below 10um at the cutter (0.01mm) which is pretty reasonable.

Murray

I also got 0.007mm runout measuring my collet chucks taper and the actual tool about 0.012mm

You say you measured above the collet, if that was on the body of the chuck than I would not go by that measurement as it is the taper in the chuck that matters and that in turn will be governed by the taper in the mills spindle.

Thank you all for your insight and wisdom - much appreciated and in time I hope I can contribute to others in similar manner

I will recheck later

Just a beginner observation but skill allows the operator to overcome many shortcomings found in cheap and worn equipment.

A machine in good order saves time because the operator doesn't need to understand and compensate for errors. Employers can use cheaper and more easily trained semi-skilled staff rather than expensive hard to replace master-craftsmen. Operators can share machines without having to worry about differences. The downside is that precision machines are expensive to buy and keep in good order.

Having a precision machine in a home workshop will save the owner time. Also there's much pleasure to be had from owning a fine tool, not to mention the bragging rights!

But many hobbyists do precision work without precision equipment. They learn how to make the best of what they have and apply skill to compensate for any shortcomings in their equipment. For me the hobby is more about learning practical skills and stretching my brain within a budget than making things. The time factor doesn't matter very much to my kind of hobby-bodger and I enjoy from getting results with limited equipment. It's not an approach that works for everyone!

There is a particular beginner mistake I feel. You get interested in metalwork without knowing much about it. You ask around and read books. It's quite easy to get the 'not wrong' impression that buying the best of everything will solve all problems. You quite often see posts on the forum looking for brand-name reassurance and asking 'which is the best quality wot-sit...' Good questions, but the answers can be discouraging and taking the advice unaffordable, when much more ordinary stuff would do the job. I'd suggest that many - not all - would do better to lower their sights, buy something, and get on with it. For many the easiest and lowest risk way to make a start is to buy new Far Eastern from a Local Vendor, not direct from China! Many others have ready access to good second-hand kit. Either way can be made to work. Come on in, the water's lovely!

Dave

Wise words Dave

I have dipped my toe in the water and am learning fast, the biggest issues are time, confidence, and sound knowledge of how to use my equipment safely. The lack of a local club may be rectified as I intend to move soon, watching YouTube is inspiring but only takes me so far, the acid test is getting off my butt

I have no ambition to produce award winning models, simply to competently "make stuff" of interest to me, the list grows as I gain skills

I don't have the "latest and greatest" kit, simply what I could afford - and what I can get past my wife - with a few luxury items thrown in. I have a couple of contacts whom I source 2nd hand kit off which helps keep the cost down, but it is also true I have bought a few duff items such as a vice whose jaws lift quite badly

And in time I may be able to impart a few wise words to others, just not this week!

I measured a few this morning and found the end mill cutters themselves (when fitted in a collet chuck or end mill holder) were typically coming in with around 10-15 um total runout. The basic collet chucks or end mill holders, measured on the internal taper or bore were generally under the 8-10 um level and on one measurement there was barely any discernible runaout at all ie of the order of 1um or so. Of course, if I'd been setting to actually machine something, I'm sure I wouldn't be able to reproduce that....

The keyless chucks are worse not surprisingly and I was seeing figures around the 50-80 um level. That's OK for drilling my sort of holes. The Xmas cracker chinesium ER32 collets (£24 for 9) I got for a laugh showed a seasonally generous >50 um runout, so not much better than a drill chuck!

Murray

I *think* I have found the root cause of the issue

The drawbolt was tight but running eccentric when looking at the top nut

I removed the draw bolt which was a very sloppy fit at the quill top, I suspect the drawbolt was not centred therefore pulling the arbor unevenly

Dose this seem reasonable? and if so, any recommendations on what steel to use and whether to harden to make another drawbolt please - I managed to strip the first couple of threads on the existing drawbolt which does not extend very far into the arbor, I suspect the drawbolt was the wrong one...

Mine are all a sloppy fit at the top, does not seem to affect anything.

Does not need to be anything special if you make a new one.

Have you measured the actual spindle taper for run out yet?

Run out on the neck of the end mill was 0.09mm which is when I noticed the top if the drawbolt running eccentric. I removed the drawbolt and damaged the very end of the thread extracting the arbor - lesson learnt, I'll remember to use a drift next time. I can't refit the arbour until I've made another drawbolt, the drawbolt only engaged the arbour by ~5mm which can't be enough for security and I probably weakened the thread during original installation

A job for next weekend as I am out of time today

I managed to get half an hour in the workshop - I used a piece of M10 threaded bar with a couple of nuts to secure the arbor and measured the runout a less than 0.001mm to the inside of the collet as per the second test in the YouTube clip - so I am happy the arbor is not the cause of the issue

Fitting an 11mm end mill tightened just enough to hold the mill and measuring at the neck, ~0.007mm, tightened further, 0.010mm, fully tight 0.015mm so it looks like everything is ok and comparable to Jason and Muzzer's observations

Thanks to all for your help, much appreciated

Wonder if you were caught by a metric imperial gotcha? 3/8" BSF and 10mm are similar enough to catch the unwary.

I tested the drawbolt thread by screwing into the arbor before installing into the mill and am comfortable the threads match as I was able to screw in an inch or so, but you make a good point Dave