Sherline Gear-Driven Power Feed

Great detail, Russ. How does it work?
 
mikey said:
Pretty cool set up in the video.

The Sherline power feed was just a single speed, non-reversible rotisserie motor that was way overpriced. It came with an adapter to fit the motor to the end of the lead screw and it ran really hot. In my opinion, it was a POS.

A much better option is to hook up a reversible DC variable speed gear motor to the lead screw; direct drive via an adapter between the output shaft of the motor to the end of the lead screw works fine. This gives you variable speed and feed to precisely dial in a cut on the fly and it works extremely well. Gearing is fine but why bother tying the feed to the speed for turning? A VS motor is far, far better and is easily disconnected for threading.
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I’ve been thinking about doing something like that on my PM1127. The lathe is so much quieter when the change gears are disengaged.
 
MSD0 said:
I’ve been thinking about doing something like that on my PM1127. The lathe is so much quieter when the change gears are disengaged.
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It might be worth a try. Your lathe has a saddle drive shaft that can be hooked up if you pull the drive gear off that shaft and hook up a DC gear motor to it. Speeds and feeds greatly affect the cut, both roughing and finishing, and my experience with being able to adjust both on the fly on my Sherline lathe has convinced me that it is a significant advantage.

My favorite materials to do this with are 12L14 and 6061 - mirror finishes on both - but it works for almost anything I turn on that lathe. I especially like turning O-1 at high speed for a finish cut but with a very slow feed; the finish is just fantastic under these conditions and you just cannot get that when the feed is tied to the speed through gearing.

Something to think about ...
 
I've had a chance to play around with the power feed I built, and for me at least, it looks like a winner. As I've stated previously, I tend to take cuts of only .010 deep, but to see what the drive could do, I made cuts up to .030 deep in mild steel and the drive didn't seem to hesitate at all. Not very scientific, but with everything cleaned up, lubricated and adjusted, it worked fine. The test cuts were made with the 200 rpm motor installed. I'm thinking about changing that motor out for one that is rated at 100 rpm for better control of feed when turning a diameter. The down side of that would be giving up how fast the feed unit can get the saddle to move out of the way when I want to get a measurement or something. At 100 rpm on the lead screw, that's still about five times faster than the Sherline unit I had. My original reason for building this thing was to get away from having to turn the feed dial by hand when I needed to move long distances. The ability to independently adjust speed and change direction is great. It's all about give and take as far as speed and torque are concerned. I may find that the 100 rpm motor is an even happier compromise. If the 100 rpm motor works out as I hope, I've got a pretty wild idea brewing that I want to work on next.
 
My motor is just under 100 rpm and it works great. Lots of torque, speed is adequate, control is very good. I suspect you might be happiest with the 100 rpm motor, Russ.
 
You're probably right Mike. I got too caught up worrying about speed. At least I don't have too much money tied up in these things. The average price of a motor so far is around $15, so it's possible to experiment without spending a lot. It seems like I spend more time and effort designing and building things for the Sherline than anything else.

Russ
 
mikey said:
Pretty cool set up in the video.

The Sherline power feed was just a single speed, non-reversible rotisserie motor that was way overpriced. It came with an adapter to fit the motor to the end of the lead screw and it ran really hot. In my opinion, it was a POS.

A much better option is to hook up a reversible DC variable speed gear motor to the lead screw; direct drive via an adapter between the output shaft of the motor to the end of the lead screw works fine. This gives you variable speed and feed to precisely dial in a cut on the fly and it works extremely well. Gearing is fine but why bother tying the feed to the speed for turning? A VS motor is far, far better and is easily disconnected for threading.
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Interesting you say this as today I bought a electric motor to control the feed instead of a gear set. I think my Sherline is even older then this ( though it looks the same ).

The motor is a sewing machine motor, currently mine has no speed control but I will build that.
 
The Sherline power feed turns the lead screw at approximately 21 rpm to get the 1" per minute feed listed in the description of the now discontinued device. I have one and find that the feed works "OK" but I wish for more variability such as that achieved by Mikey with the variable speed gear motor.

The lead screw on my Sherline is 20 threads per inch. That moves the carriage 0.05 inches per revolution of the hand wheel. Desirable feed rates would require lead screw RPMs to be adjustable in the 10-60rpm range, IMHO. The sewing machine type motors that I am familiar with would not produce the required torque in that RPM range, if they even could be made to run that slow. The speed would have to be "geared down" using a gear box or belt system, I think.
 
Initially I was thinking the electric motor would drive the lead screw for cutting.

Yes I have the sewing machine motor and there is no way I can get that to go slow and produce torque. The Sherline DC motor is expensive to get shipped to Australia as-well as being in USD, I am thinking I will investigate a brushless DC motor on ebay and make up some pulleys to run that motor.
 
If you want to go that slow, a stepper is probably a better option and you will have finer control. If all you want is variable speed, it would be a super simple microcontroller program or even just a 555 timer with a pot to control the speed.
 
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