What do you all think of this machine mod?

[Inferno]

I have a mid sized mill/lathe combo.
I added a DRO.
My biggest complaint, now, is having to switch gears every time I want to change the crossfeed screw and that the X-axis feed works at a much faster rate than the Y-axis. So to get the Y-axis to feed at the same rate, I'd have to swap gears. No fun.
I also am not excited about the junk transmission the crossfeed has. To pop out of position (for/rev) takes significant effort but to bypass the neutral indent is super easy so it can go from left to right accidentally. I also don't like that I have to run the lathe in order to have an automatic feed when I'm milling.
Nuff said about what I don't like.

On the right end of the crossfeed screw is a handwheel that's supposed to be for setting position. With the DRO I haven't used the indicator even once.
It hangs far enough off the end of the machine that there's room to put a gear there.
I have a plate I added to that end to support the right end of the DRO rail.
I'm thinking of removing the indicator wheel and replacing with a timing gear. Then attaching a stepper to the plate for the DRO and running a belt to the crossfeed screw.
I can add the feed wheel back on in case I ever need it but the crossfeed would be powered by the stepper, unless I'm threading. It would be able to have speed control and reversible. Only downside that I can see is that if I use the feed wheel it will put "work" into the stepper which would feed power back into the controller. I don't know that this is an issue though.

What do you think?

(Belt placed just to show perspective)

 

[markba633csi]

I've seen others add a motor to their lathe's leadscrew- not uncommon.
You might want to figure out a mechanical disconnect for the drive- some type of sliding coupler. Not that spinning the stepper manually will damage anything but the cogging forces/stiction of the stepper rotor might be annoying when you go to turn the crank
-Mark

 

[DavidR8]

That looks like the lead screw element of an ELS installation. Just sayin'

 

[Inferno]

That looks like the lead screw element of an ELS installation. Just sayin'

ELS?

 

[DavidR8]

ELS?

ELS stands for Electronic lead screw which is a sytem to eliminate the need to deal with change gears (if that's what your machine has) or a quick change gearbox.
In its simplest form an electronic lead screw is an electronic system that coordinates the rotation of the chuck to the rotation of the lead screw.
In a change gear or gearbox lathe that's all done with mechanical gearing.
On an ELS-equipped machine this is accomplished with an encoder on the spindle that reads rpm which inputs data into some electronic wizardry that tells a stepper or servo motor how fast to turn the lead screw based on user input of the desired feed rate or thread pitch.

 

[Inferno]

Ah, I see. What I'm trying to accomplish for now is a dumb ELS then.
I don't need it to talk to the chuck at this point in time.
Eventually I'd like to get there but there are only so many days on this planet and it's not the highest on the list.
I do have a fundamental encoder on my lathe head. It's just for the DRO though and only has six data points. Far from what would be needed for threading. If I get serious about it, I have a 32 segment wheel I could put on it. But then programming comes into play and, well, there's that time left thing.
BTW, I'm not "old" or in imminent danger of mortality. I've just had a few scares so I want to get the bucket list chipped away a bit.

 

[Huub Buis]

Only downside that I can see is that if I use the feed wheel it will put "work" into the stepper which would feed power back into the controller. I don't know that this is an issue though.

I have steppers on my lathes and can turn cnc or by hand. When turning by hand, the driver is still powered but not enabled. I have this setup for about 10 years and manual turning did not harm the drivers.
The stepper has about 200 positions (full step). If you turn the hand wheel manual the stepper will try to get back to one of it's 200 positions. You don't see it on the dial and it doesn't happen every move, only so now and than. If it does, you are slightly off position (1/400 stepper turn max).
For the lathe it means I can't manually turn tight dimension diameter (0..01 mm). That is not a big deal for me, I do this anyway only CNC.

the cogging forces/stiction of the stepper rotor might be annoying when you go to turn the crank

This depends on the size of the stepper, compared to the size of the hand wheel. On my bigger lathe, the hand wheel diameter is twice the size of the stepper and it is hardly noticeable. On my mini lathe, the hand wheel is about the size of the Nema17 stepper and after upgrading to Nema23 it became annoying. I moved back to the Nema17 stepper and will make a larger hand wheel before placing the Nema23 stepper.

 

[pontiac428]

What people fail to realize is that the cross feed and long feed are 1:1 linked.

When I turn 1" on the long travel handwheel, my part gets 1" shorter.

When I turn 1/2" on the cross infeed, my part gets 1" smaller in diameter.

The feed is 1:2, but the change in diameter (part size) matches the long feed and the feed rate chart at a 1:1, as long as you remember d=2r.

The user is responsible for relating cross slide infeed to diametric feed, but it is indeed a 1:1 system in these terms.