Wrong Rpm Motor On My Wards Version Logan 200

bama7

bama7

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After reading several articles and manuals for the Model 200, I need some help. Apparently the PO changed motors on my lathe. The manual calls for a 1/2 hp with 1725 rp m. The motor installed is a 3/4 hp with 3450 rpm. It is an old Craftsman motor and it runs good. Can you still cut threads correctly with the listed gears using the 3450 rpm motor or do I need to change to a 1725 rpm motor?

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The motor does not affect the thread pitch, so the listed gears will still be correct.

However, the spindle speed will be twice what you would get with the 1725 rpm motor. That may be an issue, since most people cut threads at a pretty low spindle speed.
 
cds4yu said:
The motor does not affect the thread pitch, so the listed gears will still be correct.

However, the spindle speed will be twice what you would get with the 1725 rpm motor. That may be an issue, since most people cut threads at a pretty low spindle speed.
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THAT MAKES ME HAPPY!!! I was more concerned the speed may cause a problem with the travel when cutting threads. It sounds more like developing an ability to start and stop more quickly. Thanks for the information.
 
I'm no expert, but it seems like you'll be spending a lot of time in back gears unless you do something about RPMs being doubled. I'd consider either acquiring a slower motor, adding an additional drive stage/countershaft with 2:1 pulley/gearing reduction from the motor shaft, or replacing existing pulleys on the motor-spindle/countershaft (in order of increasing difficulty). A second stage countershaft (gear or pulley driven) might be a fun little project.

As others have said, threading doesn't depend on motor speed. The carriage advances as the spindle rotates, each rotation moves it a fixed amount (no matter how quickly each rotation occurs). The gearing ratios (configured with change gears) determine the "fixed amount." You'll have limited time to disengage the carriage feed and retract the cutter after each pass, though, which usually means adjusting belts for pretty slow speeds. I've always been able to avoid back gears for threading (I've never threaded anything with a very large diameter) but with a 2x speed motor you may be forced to.
--
Rex
 
Just have to be fast on the half nuts at the higher RPM's...Threading.
 
Ed ke6bnl said:
can you reduce the size of the pulley on the motor
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I just got a set of original two step pulleys yesterday in the mail. I did not measure the pulleys that were on the lathe because they were single step. My main goal for this lathe is to have it working correctly without spending too much more money. As far as using the backgears to slow the rpms down to thread I don't think that would create a problem, would it? This is more of a project that is almost complete. I have a Logan 1825 for my next project. It has the QCGB and is the one I expect to take me to the rapture.
 
Personally, I like threading in back gear. I'm not sure why others want to stay away from back gear.
 
I'm not familiar with the speed range on the Logan nor do I have a great confidence in my single-pointing abilities, but if you are running a motor that gives you twice the design speed not only will you experience faster low-end but your top end rpm's may be dangerously fast. I'd look at that as well, not just your low range, to decide if you want to continue to run that 3450.

-frank
 
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