Sorting out accuracy on my Mill/Lathe

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djh82uk:
Hi Guys

Inspired by posts on here (most notably fixing darrens lathe) I have decided to check and service my machines. Some of you may have seen from my other posts that I am in the market for a larger mill & lathe, so I converted my Taig mill from CNC back to manual. When I got the mill, I immediatley converted it to cnc (after playing with the handwheels for a while whilst going oooooh), so in short I have never manually milled, and thought that I should so that I had a better odea of what I want in a new mill.

Well I got it back to manual and found quite a bit of backlash on the Y axis (moves the table to/from the column?), I measured it as 3 thou. I measured it by putting my dti up against the table, and moved the wheel to 0 one way, and then turned the handle very slowly until the needle budgedm hand wheel registered a movement of 3 thou before the needle moved. This was the only way I could think to measure it as the machine is imperial and my DTi in metric.

Now I have a confession to make, I have not stripped this machine back down since it was first converted to cnc, the gibs were out, I had backlash and there was oily gunk everywhere. So i thought I would stip it down.

It is currently in pieces being cleaned up.

Now as for my lathe, after reading bogs log of fixing darrens lathe I though "oh cr*p" as I have always struggled to get a decent finish, nothing a bit of W&D doesn't fix, and sometimes I do get a nice finish, normally it has ridges in it (I always thought that I just did not have a fine enough feed), so I want to set the lathe up as if I just bought it 2nd hand., so what do I check, and how do I check it?

Starting with the carriage bed, the only way I could think of was to mount the dti stand on the cross slide, the dti arm on the bed, and move the carriage back and for, I get a max offset of 0.03mm, is that 1 thou or 11 thou?.

Obviously I need to also check the chuck & tailstock, tailstock I am fairly sure is out but I don;t know how to check it not having a test bar or co-axial dial indicator.

I have some very straight looking steel rods out of a desktop scanner, but doubt they were made to the correct tolerances. And they are obviously an unknown.

Any advice?

I uploaded a bunch of pics here until I can find a better batch image resizer for linux:

http://pomme-bleu.co.uk/wedding/categories.php?cat_id=3&page=1

djh82uk:
Hmm, apparently the backlash from the factory is normally 0.0015 to 0.003 inch, still seems a fair bit to me tho, and I don't like being at the higher end of the scale

DJH

tumutbound:

--- Quote from: djh82uk on November 28, 2009, 09:00:31 PM ---
I uploaded a bunch of pics here until I can find a better batch image resizer for linux:

--- End quote ---

For Linux, install ImageMagick and use the mogrify command.

djh82uk:
Yeh I have imagemagick on the machine but it makes all the images blocky, eve after fiddling with settings. I have GDimage on my webserver and that works fine for now but am using that php page until i sort it out in my own machine, re-compiling imagemagick throws up a GCC error so I must have a conflict somewhere

djh82uk:
Ok, just tried testing my lathe chuck, with the dti on the outer body of the chuck I get a movement of 0.03mm or 1.1 thou, is that within normal expected tolerance for a mini-lathe?

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