Funny Snafu With My Pm-1340gt

joshua43214 said:
This is the carriage feed, they are usually something odd in terms of distance per revolution.
It actually moves 0.600" per revolution, not 0.58". So 2.424" would just be 4 turns + 6 ticks.
The pic does not show that the minor ticks are 0.004", and 0.020" per major tick.
I admit it is odd, but if you are smarter than the machine it is not difficult.

It is really impressive how smooth and precise the carriage wheel it on this lathe
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It looks like the handwheel should have been marked .48, .52, .56, and then there is a half distance interval that would be .58. If it is truly supposed to be .60 then the entire graduation is wrong.

It is not about whether you are smarter than the machine, it is about how many parts end up in your scrap bin due to confusion resulting from poor design. This is not a metric conversion issue, the rack is pretty obviously imperial. For less than one revolution it works OK. I can go three turns of .55, 1.10, 1.65 on MY 13x40 import lathe, and then add seven .005 graduations to reach .200, but it is quite easy to screw that process up. It is just poor design. On my mill I crank the X handle around one full turn for .200, five full turns for an inch. Stick a fork in me, I'm done...
 
I have to agree with Bob K on the dial issue, it is 0.580" per evolution on this machine, which seems quite odd. Trying to keep track at 0.004" per mark is pretty tough over distance, I could have something to do with the feed gearing/travel when it is engaged? After a couple revolutions of a dial these days, I loose track if it was 3 or 4 turns, let alone counting the marks (if I could see them). On my mill they have metric pitch leadscrews with imperial dials, couldn't figure why the dials where off until I found that they didn't have imperial leadscrews. The mill manufacturer (Optimum) never corrected the problem and still sells the same machine these days. Thank god for DROs. I still would request a replacement dial to make the machine correct.
 
mksj said:
After a couple revolutions of a dial these days, I loose track if it was 3 or 4 turns, let alone counting the marks (if I could see them).
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That's me to a tee! It's the biggest thing I struggle with machining without a DRO. My Enco 12x36 lathe has graduations that are about a 1/4" apart. I've never looked at them when running the lathe I either mark the part for length or use a mag backed dial indicator. Can't wait to have a DRO on the lathe too.
 
The Grizzly machines have metric lead screw with SAE approximations. The G0602 lathe has dials marked with .001" divisions but they are actually .025mm or .000984". Not a problem when you're only moving a few thousandths but a .006" error over an inch. AS I recall, the G4000 lathe and the G0755 mill have the same setup.

It isn't too bad to deal with because if you interpret the dial literally, you will end up slightly short. After a quick measurement, it leaves material for a final pass. However, the manuals don't state that this is an approximation which could lead a neophyte to believe that they were doing something wrong. If fact, the manual states that the compound travel is .o40"/revolution or 1.02mm/revolution when if fact, the travel is 1.00mm/revolution. Similarly for the crossfeed dial, it states a travel of 1.52mm/ revolution when is actually moves 1.50mm.
 
mksj said:
I have to agree with Bob K on the dial issue, it is 0.580" per evolution on this machine, which seems quite odd. Trying to keep track at 0.004" per mark is pretty tough over distance, I could have something to do with the feed gearing/travel when it is engaged? After a couple revolutions of a dial these days, I loose track if it was 3 or 4 turns, let alone counting the marks (if I could see them). On my mill they have metric pitch leadscrews with imperial dials, couldn't figure why the dials where off until I found that they didn't have imperial leadscrews. The mill manufacturer (Optimum) never corrected the problem and still sells the same machine these days. Thank god for DROs. I still would request a replacement dial to make the machine correct.
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Doh! You are correct. I never actually use this wheel for measuring distance any way, I just use a dial indicator if I need more precision that cutting to a scribed line.
The OP's lathe just has an extra 0.48 stamped on it. Other than that the dial is correctly made

I was actually wishing for a DRO on the lathe the other day. I want one so seldomly that it has been pretty low priority though.
 
I mounted a DRO on my lathe before I ever used it, so didn't notice the graduations on the carriage handwheel. I did notice the .002 graduations on the cross slide and would not have been happy if I had to use that dial either. There have been some other issues with my lathe as well, but overall I am happy with it.
 
On my 1127VF-LB, the hand wheel has an odd number of graduations as well. I believe one full revolution is 1.190" IIRC. It really threw me off when I first got it and didn't notice it. I was using the hand dials for roughing something to length and keep coming out way off, even for roughing. I believe this is due to them using an Imperial conversion handwheel on a metric set of gears in the apron. There was also a metal "sticker" on top of the handwheel bracket that said II = .020" indication that it was .020" between marks, which checks out pretty close against a dial indicator. Then after that "sticker" got some oil on it and came off, I saw that the actual handwheel bracket was engraved with II = .05 MM. If you do the math, .05mm = .0019685" or .020" if you round up. I still use the handwheel graduations for roughing and just reset it to zero each time I reach the supposed 1.000" mark. Then for actual measurements, I use a magnetic backed dial indicator since I don't have a DRO.
 
Something has been bothering me about the OP's picture.

The dial on the crank is supposedly reading in inches but it appears to have .58" inches per revolution. That is one coarse lead screw: less than 2 tpi. Additionally, .58" does not work out to a nice simple number of mm pitches as all common metric threads are. If it were actually reading mm, the pitch looks better but is till not a nice simple mm spacing.

I took a look at some pictures of the PM1340gt lathe on the machine tools online website and the cross feed and compound feed dials have both inch and mm graduations. However, there is also a dial on the carriage crank and it appears to have a single scale on it.

Now it makes sense. A single turn of the carriage crank on my G060602 produces .95" of travel. The exact distance being determined by the pitch on the bed rack and gear train used to connect to the crank. Like many lathes that I have seen, it has no dial so I never concerned myself with the amount of travel per revolution.

Bob
 
What would be cool is if the carriage handwheel had a push or pull feature to change from a coarse feed to a fine. Probably doable, but not sure I'd tackle it.
 
Are you remarking on the 0.580"/revolution as weird, or the fact that you have two 0.480" positions? The latter sounds like a late Friday night blooper, but the former (as others have stated) is fairly normal.

My G0709 is exactly the same way (and the exact same weird number). It doesn't equate cleanly to a metric number either as far as I can tell (0.580 = 14.73 mm). It would be understandable if it was 0.590" per revolution (almost exactly 15 mm).
 
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