Craftsman 101.21400 lathe motor setup

[benven2]

A generous friend recently gave me his 6 inch Craftsman 101.21400 lathe. It is mostly complete but is missing the countershaft assembly and ac motor. Instead, it has a 1/2 horse 1750 rpm DC motor with a variable speed controller. He had the motor rigged up so that it sat under the table, and supplied power directly to the spindle pulley by a single belt through the bottom of the headstock. Using that setup, and two pulley combinations, I can get spindle speeds ranging from about 150 rpm to 2500 rpm, though there isn't much torque at the lowest speeds.

My question is will this setup work for threading and other uses? Would I be better off finding a countershaft assembly and setting up the lathe as it was originally supplied with it's lower low end speed (50rpm)? I'm completely new to this and don't want to complicate the learning curve. Thanks for your help.

 

[wa5cab]

My gut feeling is that 150 RPM is already too fast for cutting coarser pitch threads, even without the torque limitations. I take it that the two spindle pulley steps being used are already 1the slowest two. And therefore, The other two are even faster. So your two choices are a gear head motor or find the original parts.

Note that even with the original parts, you can still mount the motor and countershaft under the bench and you can still use a variable speed DC motor.

 

[benven2]

Yes, I tried 6 pully combinations and 150 rpm is the slowest speed I could get without being able to engage the back gears.

Thanks for your help!

 

[wa5cab]

Why did you not engage the back gears? That is one of the reasons that they are there. And that would probably put the motor back up to being able to supply enough torque to be useful. The back-gear reduction is about 6 to 1.

 

[benven2]

Why did you not engage the back gears? That is one of the reasons that they are there. And that would probably put the motor back up to being able to supply enough torque to be useful. The back-gear reduction is about 6 to 1.

Why did you not engage the back gears? That is one of the reasons that they are there. And that would probably put the motor back up to being able to supply enough torque to be useful. The back-gear reduction is about 6 to 1.

For some reason when I engage the back gears the spindle locks up and wont spin. When the back gear assembly is not engaged the back gears spin freely. The attached picture is of the engaged back gears. Does that look right?

 

[wa5cab]

There are two steps to putting most 20th Century small lathes into Back Gear and two steps required to get out of Back Gear and back into direct drive. Sounds as though you are only doing Step 2. Step 1 on any Atlas built lathe and on just about any other badge with a selectable ratio belt driven spindle is to pull out the Direct Drive pin which you will find the head of sticking out of the right face of the large spindle gear or Bull Gear. That pin locks the spindle cone pulley to the bull gear which locks it to the spindle. Before pulling the pin out the first time, take a black ink marker and mark the pulley in line with the pin. With the pin pulled out, but with the back gears still not engaged, if you start the motor the spindle cone pulley with spin but the spindle will not. If you then engage the back gears and start the motor, the spindle pulley will spin, the back gears will turn and the spindle will turn at about 1/6th as fast as the pulley.

To put the machine back into direct drive, first disengage the back gears. Then turn the spindle until the direct drive pin is at 11:00 to 12:00 o'clock. Rotate the spindle pulley until the hidden hole in it is aligned with the direct drive pin and push the pin all of the way back in. At this time, you might also take the opportunity to rotate the pulley 180 degrees, and find and mark the location of the second hole (if there is one). It normally does not matter which hole you use.

I don't know why the factory never marks the visible edge of the pulley but they don't.

Also, as it probably hasn't been oiled in decades, note that on the lubrication chart, you are supposed to oil the spindle pulley and small gear bushings about every week plus before every usage of back gears other than if they are only being used to temporarily lock the spindle. So perform that step before engaging the back gears.

 

[benven2]

There are two steps to putting most 20th Century small lathes into Back Gear and two steps required to get out of Back Gear and back into ...

Problem solved ! I pulled the locking pin - the back gears meshed properly and everything runs properly now. Thank you very much.

You are right on about the old lubrication. When I got the lathe the tumbler gears and lead screw gears were completely seized up with sticky, 20 year old oil.