DRO on lathe cross slide accuracy/resolution

I am looking at a DRO for my lathe. The DRO vendor is offering 5um resolution scales with an accuracy of +/- 0.005mm which is +/-2 tenths on radius or +/-4 tenths on diameter, on the cross slide. This doesn't sound that great? I am currently waiting a quote and accuracy spec on 1um scales.

What is everyone else using?

Thanks in advance for your response

Stuart

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I suppose it depends on what accuracy you feel you need to work at. I would say for 99% of what I make then 5/10ths would be fine and for anything better than that I'll get out the mic with 10ths on it.

I mostly use the mitutoyo callipers to measure on the lathe and they only read to 0.0005" and all my engines seem to run OK and develope good compression.

What sort of things do you usually tend to make?

J

In the real world do you think using a 1um scale will be practical? This is a lathe not a cylindrical grinder you are talking about.

Just trying to save you money.

Tony

I know I am mixing units here, but I can visualise old school better.
The comment on radius was that the DRO is going to read absolute position of the cross slide, so if I am understanding correctly any error will be doubled on diameter. 4 tenths is getting close to half a thou, which to me sounds significant. I suppose if I have to get a mic out for the finer work then so be it?

Tony, that is why I am asking In reality I guess I am concerned about accuracy rather than absolute resolution

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What lathe are you using.?

Basically the question I am asking is can the lathe you are intending fitting it to achieve and maintain that level of accuracy.?

Nick

1963 Chipmaster, which is much better than I am.

Mostly making stationary engine models

Edited By Stuart Bridger on 30/03/2015 18:49:55

So lets assume there is a bit of wear in the lathe, you put a bit of 1" bar in the chuck and take a 0.050" cut, take another 0.005" cut to form a slightly smaller spigot on the end

Do you trust the DRO that it has given you two dia of 0.900" and 0.890" as the DRO cannot allow for the possible tool deflection caused by a cut 10 times deeper than the second?

On a hobby type lathe I think turning to tenths of a thou will be affected by other factors like machine rigidity, tool edge, work temperature, workpiece flex and tool lube. Lapping parts is often the process used to achieve tight tolerances and high surface finish in the home workshop.

Mike

Good point Jason, on that basis are you saying that there is little point installing a DRO on a lathe?

Do you have the option of getting a higher resolution scale for just the cross slide?

Martin.

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No problem with that Stuart

I do wonder, however, [just out of curiosity] what the original spec was, for the Chipmaster cross-slide feedscrew.

MichaelG.

5 micron on the cross slide is more than sufficient. My Super 7 and M300 are so fitted. I do have a special with 5 micron fittted to a Super 7 topslide, but that is another story

All, excellent feedback, I am thinking that 5um will suffice. Experience will tell once installed with regular checking with the mic. how much spring and deflection I am getting.

Thanks

Stuart

To top it off there is temperature.

There was a program on the TV with Guy Martin fitting fitted bolts on a Spitfire which although they had been machined to the correct size Guy holding one meant it did not fit as he had warmed it up.

I doubt if that sort of precision is required for stationary engine, which have been made successfully before all these electronic aides.

Bob

No but putting one on won't make your work 10 times more accurate overnight though I can see where they do have their advantages.

.

I have DRO's and very pleased with them I am.

However I do have an 'old school' pro machinist friend. (who of course uses DRO's) But he is totally adamant that I should not have fitted DRO's until I was totally proficient without them.!

With that in mind would I ever be tempted to switch mine off.? ................... No chance.

Nick

> There was a program on the TV with Guy Martin fitting fitted bolts on a Spitfire which although they had been machined to the correct size Guy holding one meant it did not fit as he had warmed it up.

Which bolts? I can't believe they would have turned out many like that in war production!

I remember reading that they made couple of spits with flat-head rivets (much less drag) They then stuck split peas on the rivets to find out which ones made the biggest difference, so they could make production planes with as few flat head rivets as possible.

Neil

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The ones that hold the wings on

MichaelG.