12x36 hp issues..... need advice or recommendations

I think you may want to slow it down a bit I agree the material is probably getting tough on you with the build up of heat. On the other side of things I have had a 21/2 horse DC motor on my lathe for some time now with no problems at all no over heating and the only gears that have gone out are the ones with many years of wear. Since the DC motor has a higher top RPM I just leave my belt setup geared to the slowest spindle speed the PWM speed control gives me any speed I need for turning or polishing something. Ray
 
Yeah I didn't have any problems with the cutting until I let it sit over night and cool after taking several .050 cuts. The motor I would use is a Baldor Industrial use for class I div I hazardous atmospheres. It was a take out motor that ran nonstop but was upgraded to 2hp. It's in good shape. 3ph. I would continue to use the belts on the machine to control speed for the most part. That way I'm keeping the motor in its rated rpm. What's the most spindle rpm you guys would feel comfortable with? I'm not at my lathe now but what's the stock configuration worth? Almost 2000 rpm right?
 
I run a 1/2HP 90 volt dc motor on my bench 12x24 lathe. I don't normally take very deep cuts but i can take a .030 cut in steel. the belt will start slipping before the motor stalls out. that i think is the benefit of having a dc motor. you can hear the controller just giving more amperage to the motor to keep the rpm constant.

stephan
 
Chevy,

The published Atlas spindle speed chart hasn't changed any since 1937. It gives a speed range of 28 to 2072 RPM. But it never has specified a motor RPM. 1725 RPM has been the most common spec on single phase 60 cps motors for the past 50 years. Which would presumably be the full load RPM. At no load it would be running very close to 1800 RPM (synchronous speed). But in the 1930's and 1940's, stated ratings of 1750 and 1740 were common. I also don't know whether the original chart was calculated or measured. I've never put a tachometer on my spindle.

In any case, around 2000 is the maximum with the original setups.

Robert D.
 
It currently has the 1725 motor on it. The 3ph motor is a 1740
 
You got something going on cause my little 9x20 can just pull off .05 with some cheap inserts and even then it aint slowing the motor but you can hear the on set of chatter. I just pushed it this weekend to see using 4140

If you did work harden it, I would think the first .05 would have took a case harden off let alone the passes after that. Unless you hardened the whole thing.

Maybe you got some bad bearings and that cold weather helped them stay cool? Or made something flex or bend that allowed a decent cut.
 
Yeah it seems to be cutting ok now. Around 600 rpm .05 been taking two or 3 passes the. Letting it cool before cutting again. I already have the motor so I'm gonna prolly just swap it out. I need 2 pulleys. One for the new motor it has a bigger shaft than stock. Also one of the 4 step pulleys on the side is sprung so I can't go above the 600rpm setting.i had to remove the 4 jaw and put on my 3 jaw for another project....when I put the 4 jaw back on I was happy to see that it indicated at zero with no adjustments.
 
Ulma Doctor said:
how solid is the lathe? is it worn or does the carriage have excessive slop?
1/2 hp is way too light in my opinion and may be a source of your problems
Click to expand...

I was thinking the same thing. My 10" lathe came with a 3/4 HP motor, and a 12" lathe would require more power than that (I would think). I put a new (single phase) 1 HP Baldor on mine, and it seems to work great. The previous owner that put the 1/2 HP motor on it probably just used whatever he had laying around. A 1 1/2 HP sounds reasonable for a 12" machine, and maybe even 2 HP.

GG
 
I would have loved to have a 2hp but all we had laying around the salvage pile at work was some 1 hp and a couple of these 1.5hp. On another note I mentioned above about a sprung pulley...I turned an alum pulley for the 800rpm. Started with 4 in round that was about 4 in long. When I turned the hub it would have been nice to have the extra power. That turned into a 2 day project haha one for the hub diameter and the other for the v groove and shaft hole. Reaming and broaching.
 
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