Sorting out accuracy on my Mill/Lathe

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Russel:
Sherline suggests that with their equipment .003" to .005" is normal for manual operation [edit: for leadscrew backlash. I just noticed you were talking about the chuck.] CNC usually requires .003" or less if I understand the recommendations correctly. I've kept my equipment between 3 and 5 thousandths with good results. Of course, I always approach a setting turning the hand wheels the same direction to account for backlash.

Fixing Darrens lathe made a big impression on me as well. Since then, I've gone over my machine tools with a fine tool comb. I also ripped apart the bench I use them on and built it up solid and square, as well as using a composite quartz counter top remnant under the machine tools as a good flat surface. I've also made it a habit to always carefully clean and oil the ways when I am done for the day.

jim:
i just put some 1" bar in the chuck on the C3 i've just bought, turned about 6" length and checked for taper, much to my horror it was about 6 thou. soon got it down to a much more acceptable 1 thou over 6" :thumbup:

bogstandard:
Gents, it is very difficult trying to suggest 'fixes' for individual machines, because they are all different in some way.

So really it is a matter of you looking at how the adjustments are made, and spending time tweaking until they are spot on or within your acceptable limits.

I have noticed that a few of you are getting confused by the metric/imperial way of thinking, and of course if you are used to working in just one, it can be difficult working in the other.

I am lucky that I can interchange between the two automatically and can also think in both, but for small figures the decimal point in either can be confusing. So here are a few easy conversions, that if you can remember them, will help when working with the 'other one'.

0.01mm roughly equals 0.0005" (half a thou)

0.025mm is 0.001" (1 thou)

0.05mm is 0.002" (2 thou)

0.1mm is 0.004" (4 thou)

So coming from the other way

0.040" (40 thou) is 1.0mm

0.010" (10 thou) is 0.25mm

0.005" (5 thou) is 0.125mm

These are close enough guesstimates in what you are working with.
I know it is difficult sometimes being able to afford measuring intruments, but if at all possible, try to use instruments that are in the same standard as the machine you are working on.

And don't forget, the correct lube for the job. It does make a big difference to how a machine runs and operates. That is why there are so many on the market, they all have a different job to do.

Have you started to notice that the machine isn't cutting the way it normally does, then ask yourself, when was the last time I gave it a drink?

Bogs

djh82uk:
Thanks guys

Im trying to decide wether to leave it or try and improve it a smidge for the mill. Need to find a type of oil to use aswell,

The lathe however, I am still looking for ways to measure things, and wether 1 thou runout on the chuck is ok.

I did just notice however that the 0.03m deflection on th ebed was caused by the carriage being able to be lifted up at the back by about 20thou.

So thats gotta be sorted first, im presuming at this moment that the gib screws have loosened

DJH

websterz:

--- Quote from: djh82uk on November 29, 2009, 09:12:07 AM ---...I did just notice however that the 0.03m deflection on th ebed was caused by the carriage being able to be lifted up at the back by about 20thou.

So thats gotta be sorted first, im presuming at this moment that the gib screws have loosened

DJH

--- End quote ---

That is definitely the place to start! Adding a carriage lock will help as well. On facing cuts you can lock it down solid, on turning ops you can just snug it up a bit to help hold things down. Tapered gibs are of course the ultimate solution. :proj:

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