I can't read a Cross Slide Feed Handle?

[The_Apprentice]

Alright, I'm quite confused at my Chinese mini-lathe. And being no expert certainly does not help.

My feed handle has 40 graduations, backed up by a 0.025mm or 0.001" indicator.

So one rotation should be only 1mm or 0.040"

Here is the problem, it is advancing my tools into the work much deeper than this. And by that, I am not talking about making the common mistake of measuring the diameter of my turned product when I meant the radius and confused why we are off by a factor of 2.

Is there something I am missing about these Chinese lathes? Or my math is just wonky?

Just going by eyesight, a 1 mm cut is looking like 4 or so to me.

 

[DAT510]

Have you put a Dial indicator on it and compared the measured distance travelled to what's indicated on the Handle?

That would go a long way in helping you determine what's off. I have heard of Metric Screws being mixed with Inch Dials and visa versa.

 

[T Bredehoft]

Just a suggestion, Touch the work with the tool, set zero. Take a cut. Measure with a mike. Write it down. move the dial to 10, take a cut, measure with a mike, write it down, and tell us the two numbers.

 

[The_Apprentice]

Tomorrow I was planning to do some tests and put up some accurate measurements, assuming I don't get too carried away with my other POLISHING test plans... Will report then with more data on this mystery...

 

[rwm]

On my Chinese lathe the leadscrew was metric and the Imperial markings were slightly off. It was off about 0.004" per revolution. Took me a year to figure it out. Sounds like your error is much greater?
Robert

 

[Wreck™Wreck]

Never used a metric manual lathe however there should be a symbol on the crossfeed dial that looks like this >I number I<, the number is the graduation from line to line, many inch lathes are are divided into 200 graduations , .100 per revolution, .0005 per line or .001 on the diameter.

Like so >I .001" I<, I would imagine a metric lathe would be graduated in multiples of 10 the metric system being what it is. Could be well wrong however.

 

[Ray C]

Some lathes indicate tool movement and some indicate diameter reduction. For example, moving the tool 10 thou into the piece will reduce diameter by 20 thou.

 

[Wreck™Wreck]

On my Chinese lathe the leadscrew was metric and the Imperial markings were slightly off. It was off about 0.004" per revolution. Took me a year to figure it out. Sounds like your error is much greater?
Robert

You mean that it is .004" per .graduation I suspect, if .004 per revolution it would take 125 revolutions per inch of diameter, surface grinders do not have lead screws this fine.

 

[Ken from ontario]

Have a look at Frank Hoose videos on LMS 5100 ,-#6, it all about what you're asking:

 

[The_Apprentice]

Hey Ken, I already did that JUST before you posted it. Did the same thing, decided to just measure the travel, no need to check the cut. Well, so far, it lines up perfectly. .001" = .001" on the guage.

I am thinking now part of why things look so off on the very narrow ridges I cut yesterday must be due to my inexperience of observing narrow ridges. I think it may be partially an optical illusion due to the curves perhaps. Also, the material I cut into still has the original rough surface to it, which only adds more to the optical illusion maybe.

Though I think I did cut a little deeper than I realize... as when I brought the tool up to the workpiece and then dialed in, I'm sure I dug the tool into the rough surface a bit more than I thought each time before dialing in a whole 1mm.

For now, I am going to blame inexperience of the operator, and my failing eyes. But I will keep a close eye on what happens after working with a finished surface later on today...