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Acceptable runout

This topic has 18 replies, 10 voices, and was last updated 29 March 2011 at 00:01 by Terryd.

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26 March 2011 at 15:13 #66081
Raymond Anderson
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@raymondanderson34407
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26 March 2011 at 15:13 #38040
Raymond Anderson
Participant
@raymondanderson34407
26 March 2011 at 15:32 #66082
Raymond Anderson
Participant
@raymondanderson34407
Hi all,

I have just finished making an ER40 collet chuck, The chuck was made from EN24 mounted on a camlok backplate. When I use my most accurate indicator [a Mitutoyo that reads to .003mm] The needle does not move when in contact with the backplate, it does not move when loaded against the collet chuck nose [internal]. When I tested the fit of the collet into the finished bore I used an Eddings Permanent marker and have total contact over the whole bore, so far so good me thinks but, when I put a 25mm dia length of silver steel in the collet at about 100mm from the chuck the needle just starts to flicker not a whole division [round about a half] at 150mm it is almost but not quite a whole division.What I would like to know is what would be an “acceptable” amount of runout?

could I get the figures better or no? Incidentally if I remove the bar and replace it the readings are the same so at least I have repearability.

Regards,

Raymond.
26 March 2011 at 15:58 #66083
NJH
Participant
@njh
Hi Raymond

Are you saying that the movement is .0015mm ( 0.000059 thou) at 100mm (4in) from the chuck ? (and this is repeatable) Good grief – what are you proposing to make that requires greater precision ? Is the silver steel an accurate 25mm within these limits?

Sorry not to be able to answer your query directly but I can only dream of this level of accuracy.

I await the answers of the experts with interest!

Regards

Norman
26 March 2011 at 15:59 #66084
blowlamp
Participant
@blowlamp
I think most people would class ~ 0.0015 mm, or 60 millionths of an inch radial deviation from centre as a success.

Merely leaning on the cross slide while checking for runout will show far greater movement than this.

Martin.
26 March 2011 at 18:33 #66089
Raymond Anderson
Participant
@raymondanderson34407
Hi Guy’s I have just been fed and watered so I decided to check my figures again, this time I used a magnifying glass the check the Mitutoyo and I have the same readings as originally. So what you’r saying is, it is acceptable, well that’s good enough for me.

Norman, No I don’t intent to build anything to those figures it is just after spending a tidy sum on the Rohm collets I wanted to get the best I could out of them and I was not sure what would be deemed “pass” so to speak. I machined it on the lathe that it will be used on so that helped a lot.

Graham, Yes I get your explanation about the steel being lobed. thanks.

Martin, I guess I will have to stop leaning on the the lathe when I have a ciggie.

Whilst I am here, would it be worth getting the chuck hardened? I don’t envisage it being used for heavy cuts or should I leave well alone?

Regards,

Raymond.
26 March 2011 at 18:49 #66091
blowlamp
Participant
@blowlamp
NOOOOOOOO!!!!

Quit while you’re ahead – it’ll just distort all the hard work you’ve put in for very little practical benefit.

And you shouldn’t be smoking cigarettes at your lathe – a cigar would be much more the order of celebration for a job well done.

Martin.
26 March 2011 at 19:44 #66100
Raymond Anderson
Participant
@raymondanderson34407
Thanks guy’s I will leave well alone.

As soon as I can Beg/Borrow a digital camera I will stick in a photo.

Ps it’s maybe true what they say ” An engineer works to thousandth’s, but a Bricklayer gets it right.”

Cheers lads,

Raymond.
27 March 2011 at 12:58 #66140
alan frost
Participant
@alanfrost17805
This site is full of amateurs-it makes me sthick, sthick, sthick.An engineer works to Smidgeons (as do brain surgeons) , a bricklayer works to Tads.How do you amateurs ever make anything accurate????

Edited By alan frost on 27/03/2011 13:02:29
27 March 2011 at 15:55 #66148
NJH
Participant
@njh
Hi Alan

How will you ever understand the workings of the amateur if you don’t know the units? Any amateur will tell you that, whilst the “Smidgen” of the Brain Surgeon and the “Tad” of the Bricklayer may be OK for those imprecise trades ( and indeed ,as Graham says,may be acceptable when used in conjunction, in an emerency) the universal unit for the precise Model Engineer is the Gnats .

Norman
27 March 2011 at 16:14 #66152
Anonymous
And for the toolmaker it’s a specific part of a gnats anatomy. If all goes according to plan and the part is to a gnats anatomical part then it is promoted to the dogs tackle. If however if it should not go according to plan then it becomes part of a pig.

Andrew
27 March 2011 at 16:29 #66153
Terryd
Participant
@terryd72465
Hi Norman and Andrew,

I’m so disappointed that you are promoting those old fashioned Imperials gnats still. Why don’t you get up to date, we’ve been using the more modern Standard Midge for several years, ever since the ISO standardised on that system. Honestly!

Regards

Terry
27 March 2011 at 21:00 #66172
Peter G. Shaw
Participant
@peterg-shaw75338
Stop it! Please, please STOP IT before I collapse or get carted off for laughing insanely!

Regards & thanks. Best thing that’s happened all day.

Peter G. Shaw
27 March 2011 at 22:35 #66180
Terryd
Participant
@terryd72465
Hi All,

We may be amateurs but we have shown that we can enjoy the fact,

Many regards,

Terry
28 March 2011 at 01:57 #66184
chris stephens
Participant
@chrisstephens63393
Don’t mention the “A” word, look what happened last time.

You lot make work to tads and smidgeons or the metric equivalent, but we work to milli-gnats!

“that’s all folks, back to the asylum”

chriStephens
28 March 2011 at 02:38 #66185
ady
Participant
@ady
I found that once you apply some pressure for a cut at 100mm, or even some finger pressure on a workpiece which was in a collet chuck(at 100mm), but not secured at the tailstock end via a centre, you can get a quite amazing amount of flex.

To test for flex ‘runout’ put the dial indicator on it around 100/150mm, and give it a little push with your finger.

I’ve found that a workpiece doesn’t need to be very long on a hobby lathe before tailstock centre support makes a far greater difference to the accuracy of a job than the initial runout.
28 March 2011 at 07:51 #66186
John Olsen
Participant
@johnolsen79199
I have an ML7, which of course has plain bearings in the spindle. So when you start pushing on jobs with a sensitive indicator, some of the movement you see is actually the oil moving in the bearing clearance. This does not seem to matter, you can turn to acceptably close tolerances, and in fact even when they needed adjusting a few months back, it did not seem to affect normal turning, although it made a difference to parting off.

regards

John
28 March 2011 at 23:11 #66243
Anonymous
Terry,

Tut-tut, as both the gnat and midge are members of the smaller Nematocera family they are essentially the same, just the units are different. For all practical purposes we can say that a gnats cock is gnat-urally within a s-midge-n of a midges bull. Hence we can see that the whole thing is a load of imperial cock and bull. Translating to metric that’s hen and cow.

When using the gnats anatomical measurement system I alway design using double elephant, but usual reduce it to elephant for workshop use, as the workshop is too full to get a double elephant in.

Regards,

Andrew
29 March 2011 at 00:01 #66246
Terryd
Participant
@terryd72465
Hi Andrew,

How are you? I’m very tempted to get into an etymological and entomological debate which I think would be quite fun but I might get my fingers rapped for being off thread. Perhaps later,

Best regards

Terry
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