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View Full Version : Gota question for ya'll about a lathe



airsmith282
10-21-2008, 07:56 PM
what kinda lathe has a 120 graduation dial on the cross slide and why????

Carld
10-21-2008, 08:01 PM
Because the crossfeed screw has a pitch that has .120" per revelution. Several brands have 120 divisions on the dial. Why they chose that I don't know.

Frank Ford
10-21-2008, 08:01 PM
I bought my first Taiwanese lathe from a friend. The cross slide and compound had regular graduations, but I noticed that the carriage handwheel was graduated a bit unusually, and engraved on it was a notice that each division = .006"


I asked my friend why that was, and he replied, "because they hate us, of course."

Doc Nickel
10-21-2008, 08:02 PM
120 is simply the highest number on the dial. The other five marks back to zero makes for 125, or 0.125"- an eighth-inch per turn.

That's a pretty fine thread, but nothing particularly unusual.

Doc.

[edit] Or I might be wrong on that one. :D

airsmith282
10-21-2008, 08:15 PM
so for each mark on the dial how many thou does it take off the dimeter of the bar then,,,

Fasttrack
10-21-2008, 08:20 PM
depends on whether it is a radius or diameter dial. I'm guessing its radius, but I don't know.

Either way, the best way to figure this out is to try it. Take a cut with a depth of say 5 graduations and measure the change in diameter of the part. Divide that change by five and you have your answer.

J Tiers
10-21-2008, 09:38 PM
Apparently some older machines were graduated that way, but with a small difference.......

They were marked with US graduations, but actually moved a different distance, in even mm. You might want to be certain that you know the actual movement distance.

airsmith282
10-21-2008, 10:39 PM
this one is on a standard moderen 9x20 lathe

Bob Ford
10-21-2008, 11:19 PM
Attach a dial indicator to the tool post. Put the other end against work held in the chuck crank the cross slide and you can see what the graduations do.

Bob

oldtiffie
10-22-2008, 01:32 AM
3.0mm/25.4in = 0.1181" ~ 0.120"

or ((0.120 - 0.118)/0.120) = (0.002/0.120) = (0.0167 x 100 = 1.67%).

My guess is that it is a 3.00mm pitch thread which has a lead of 3.00mm ~ 0.118" and the dial is divided in 120 parts. The error is 1.67% which may be negligible if you are only moving in say 0.010" ("ten thou") x 0.0167 ~ 0.0002" ("two tenths").

If the cross-slide is a metric pitch then so might the top-slice and the main lead-screw be.

ammcoman2
10-22-2008, 09:44 AM
I have the Standard Modern 1120 lathe. It has a cross feed dial with 125 graduations on it, as it has an 8tpi thread. Moving the dial by one division takes 0.002" off the diameter of a part.

I guess they figured that a 10 tpi thread (therefore 100 graduations of 0.001" on the dial) would be too fragile but I am surprised that the 920 has the coarser thread.

Geoff

JCHannum
10-22-2008, 10:00 AM
Doc probably has it, the graduations probably are for 125 counts. The lead screw is either 8 or 16 TPI depending on the setup of the lathe.

The simplest solution is to take a clean up cut and then take a light cut, say 5 divisions and measure the amount the workpiece has been reduced.

Standard Modern is a Canadian manufacturer, and the lathe is probably Imperial. Some of the low end Chicom imports use a mix of Imperial and metric lead screws and handwheel graduations that have little or no relation to any real world measurement, but I doubt SM is guilty of that.

darryl
10-23-2008, 10:18 PM
Seen that mixup of imperial and metric on a machine a couple weeks ago. What pile of crap that is. I'm surprised more people haven't piped up about this, actually.