Parallelism.

This topic has 8 replies, 6 voices, and was last updated 9 May 2011 at 00:31 by chris stephens.

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8 May 2011 at 17:56 #68159
Raymond Anderson
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@raymondanderson34407
Decided to make a test bar for the lathe and check the results.I used a length of my favourite stuff [EN24T] Ø40mm I reduced the main length to Ø35 and machined 2 collars at 220mm apart. The result when held only by the Rohm 4 jaw chuck is, collar1 furthest from the chuck Ø38.741mm collar 2 nearest chuckØ 38.737mm would it be worth adjusting the alignment of the Headstock [it can be pivoted on the axis] bearing in mind this lathe is about 11 years old .

I might add that I boobed when making the test bar as I should have made 1 to fit my 0-25mm mic so now I have a new 25-50 Mitutoyo it would certainly have been cheaper to make a new test bar but I suppose the bigger Øwill have less flex [that’s how I convinced myself to get the larger mic].

Raymond.
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8 May 2011 at 17:56 #5508
Raymond Anderson
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@raymondanderson34407
8 May 2011 at 19:05 #68164
Stephen Leacock
Participant
@stephenleacock91334
I`d leave well enough alone at that setting 4 microns is precise enough for all but the toughest of tolerances even a modern cnc would find that tough to beat

Edited By Stephen Leacock on 08/05/2011 19:07:45
8 May 2011 at 19:07 #68165
JasonB
Moderator
@jasonb
0.004 of a mm, if you stood your mug of tea on the headstock you would likely get more deflection than that, I would leave well alone as maybe a little of that was deflection or slightly different pressure on the mic.

J

Edited By JasonB on 08/05/2011 19:09:20
8 May 2011 at 19:27 #68166
Dusty
Participant
@dusty
Raymond

Quit while you are ahead, if your lathe as it appears, is turning parallel to within 0.002mm over 220mm. What you do not say is how you machined it, was the bar just hung out of the chuck or was it supported by the tailstock. If the bar was just hung out of the chuck I would have expected a greater variation between the two dia’s as you would get some deflection even with perfectly adjusted bearings in the headstock. Before even thinking about moving the headstock you must ensure that the shears are not twisted, that the tailstock is in line with the headstock by turning a test piece between centres. Then and only then could you contemplate moving the headstock. If you were to move the headstock it could result in a lot of blood sweat and tears and of course bad language, the end result could be worse than you have at present.
8 May 2011 at 19:29 #68167
NJH
Participant
@njh
Raymond

That’s the weakest excuse I’ve heard for buying a new bit of kit — that is since the excuse I made for my last purchase!

As far as accuracy goes Jason’s tea mug would do it I think and maybe even your breathing on it in a rush of excitement!

Rejoice in the accuracy and admire your new micrometer!

Regards

Norman
8 May 2011 at 19:38 #68168
Raymond Anderson
Participant
@raymondanderson34407
Thanks guys I guess I will not interfere with it.

Dusty, The bar was held only by the chuck, the inserts used were Walter WPP01 and the finish cut was 0.02mm with the slowest feedrate then I measured the resulting collars.

Raymond.
8 May 2011 at 20:35 #68171
JasonB
Moderator
@jasonb
I should of course point out that you should never stand your tea on the lathe, or any other machine for that matter. ….

The metal will make it go cold too quickly

J
9 May 2011 at 00:31 #68176
chris stephens
Participant
@chrisstephens63393
Hi Raymond,

As others have said leave well alone, I fail to see how you could improve the situation without the patience of a gaggle of Jobs.

Hi Jason,

Buy yourself a Bantam they have a rubber coaster on top of the headstock for mugs as standard.

chriStephens
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