Cross-Slide Leadscrew & Nut

[PeterT]

Take lots of pics. I thought for some reason you were just making the nut.

Just for reference, I had this supplier link tucked away. I have not ordered from them but I thought someone on the forum did.

3/4 - 5 Right Hand Acme Lead Screws & Nuts for Power Transmission - Roton Products, Inc.

Shop 3/4 - 5 Right Hand Acme from Roton Products, Inc. View all of our products and shop online for your power transmission needs.

www.roton.com

 

[thestelster]

According to the bible, I've calculated the dimensions for a 3/4"-5 ACME-4C thread. I have calculator apps for most of this stuff but they only do acme general class tolerances, not centralizing. And 3/4"-5 is not a standard combination that I can find specs on.

If someone can double check my numbers, I'd greatly appreciate it. They look good, but better safe than sorry.

 

[thestelster]

My main concern is not in making the screw and nut. That's just general machining practice.

Centralizing acme threads have tighter tolerances than General class threads. The pitch diameter tolerances between the screw and nut are tighter, but also the major diameters of of them as well. If you look at my numbers, if we have the OD of the screw at 0.750", and machine the nut to minimum major diameter, the difference is 0.0009" in diameter. Thats a pretty close slip fit! The problem is going to be securing the nut onto the cross-slide in a way that it doesn't twist or cant. Otherwise it will just bind.

Any suggestions? Painstaking scraping? Floating?

 

[Mcgyver]

The problem is going to be securing the nut onto the cross-slide in a way that it doesn't twist or cant. Otherwise it will just bind.

This is a frequent issue when reconditioning as the relative position of the bearing holding the cross feed screw is now in a different position than the nut.

sorry for inundating with all the photos...... maybe too many but its easy to tell the story that way

A busted nut (careful, this is a family show) on a DSG compound




Made a new block




In this case, I machined the existing nut into a cylinder, but it works the same with a new purchased nut




Assembled everything



Used a gauge pin to pick up the bore, can't remember why I didn't indicate directly




bored the block





loctite the nut in (taking care to align oil holes)







Done with perfect alignment!








Slight variation on the theme ..... a Maximat (made a new screw for this one as well). First picked up the bore. Threaded section visible, but I indicated more deeply past the thread





Mount the crossfeed bracket/mount/whatever you call it, bore and sleeve. With boring head and a longer cross slide you can run out of daylight - just mount it so its hanging over the mill's tabl






gratuitous shot of screw I made. The ending was done by eye, just carefully and at very slow speed




'
Last example.....that I could find (mercy they cried!) Another slide variation in approach. A new Z axis I made for my BCA jig borer. Its a T slot platform with precision spindle I made that replace a head with next to impossible to find collets.


Old nut mounted to the slide. There is nothing to pick up but the ID of the nut, so used a tight fitting gauge pin. Seeming like a good idea, but not accurate enough plus I decided I wanted to put a pair of AC's on the axis.

Used the old mount to transfer mounting pin and bolt locations to a piece of steel








Made a new nut holder





assembled the Z and indicated in the mounting plate, then drill and reamed the nut holder. I think I turned the nut down or may have bought a new one, same idea though

 

[140mower]

(mercy they cried!)

Never!!!!!! No mercy.
You just keep right on torturing us with pictures..... We're sadists, what can we say.

 

[PeterT]

My Roton link just reminded me of where I saw the axial threaded ABL nut & flange assembly. At least I think that is the principle being employed - if the flange/nut are rotated relative to one another on the finer thread, it takes up backlash on the main thread.

Anti-Backlash Flange Nuts - Roton Products, Inc.

Along with these Acme Anti-Backlash Flange Nuts, Roton offers a large variety of screws and nuts. Find your size and put your order in today.

www.roton.com

 

[PeterT]

Pretty good video showing some of the typical leadscrew & nut components encountered on a hobby lathe.

 

[thestelster]

This is a frequent issue when reconditioning as the relative position of the bearing holding the cross feed screw is now in a different position than the nut.

sorry for inundating with all the photos...... maybe too many but its easy to tell the story that way

A busted nut (careful, this is a family show) on a DSG compound


View attachment 44518

Made a new block


View attachment 44519

In this case, I machined the existing nut into a cylinder, but it works the same with a new purchased nut


View attachment 44520

Assembled everything

View attachment 44521

Used a gauge pin to pick up the bore, can't remember why I didn't indicate directly


View attachment 44522

bored the block



View attachment 44523

loctite the nut in (taking care to align oil holes)


View attachment 44524




Done with perfect alignment!




View attachment 44525



Slight variation on the theme ..... a Maximat (made a new screw for this one as well). First picked up the bore. Threaded section visible, but I indicated more deeply past the thread


View attachment 44526


Mount the crossfeed bracket/mount/whatever you call it, bore and sleeve. With boring head and a longer cross slide you can run out of daylight - just mount it so its hanging over the mill's tabl


View attachment 44527



gratuitous shot of screw I made. The ending was done by eye, just carefully and at very slow speed


View attachment 44528

'
Last example.....that I could find (mercy they cried!) Another slide variation in approach. A new Z axis I made for my BCA jig borer. Its a T slot platform with precision spindle I made that replace a head with next to impossible to find collets.


Old nut mounted to the slide. There is nothing to pick up but the ID of the nut, so used a tight fitting gauge pin. Seeming like a good idea, but not accurate enough plus I decided I wanted to put a pair of AC's on the axis.

Used the old mount to transfer mounting pin and bolt locations to a piece of steel





View attachment 44533


Made a new nut holder


View attachment 44534


assembled the Z and indicated in the mounting plate, then drill and reamed the nut holder. I think I turned the nut down or may have bought a new one, same idea though



View attachment 44535



View attachment 44532
View attachment 44531

Wow!! Thank you. When I made a new nut for my compound I did it in situ and worked perfect.

But, for the crossfeed, having the saddle and cross-slide together might be too tall for my Ex-Cell-O. Plus, taking the saddle off means removing the apron, lead screw, DRO read head (I have the scales on the front side), and, I don't know what else has to come apart. Unless I can prop the apron up on jack stands.

 

[PeterT]

Another ABL method with the 2 threaded segments sliding along a key & being tensioned by a lateral cone set screw ~ 26:00

 

[Darren]

I saw the RR video a long time ago. That is a neat solution, but that pin and the bushings where it meets is taking all the beating in a very small area. Something with a wedge would probably last longer.

 

[Mcgyver]

But, for the crossfeed, having the saddle and cross-slide together might be too tall for my Ex-Cell-O. Plus, taking the saddle off means removing the apron, lead screw, DRO read head (I have the scales on the front side), and, I don't know what else has to come apart. Unless I can prop the apron up on jack stands.

Yeah, thats a challenge. Time for a horizontal mill? Not even sure that would fit. I've hung them off the side of the table before on a vertical. If its too big, I'd consider getting it all set up and outsource to someone with a HBM. No shame in that when there's no other way. That or devise some sort of mobile machining approach. To ensure alignment, not sure how else to do it ...... you need to pick up the hole from Part A with A & B assembled, then machine Part B.

 

[thestelster]

Yeah, thats a challenge. Time for a horizontal mill? Not even sure that would fit. I've hung them off the side of the table before on a vertical. If its too big, I'd consider getting it all set up and outsource to someone with a HBM. No shame in that when there's no other way. That or devise some sort of mobile machining approach. To ensure alignment, not sure how else to do it ...... you need to pick up the hole from Part A with A & B assembled, then machine Part B.

I was contemplating using my right angle attachment for the milling machine. I was also thinking of doing a line boring set up, but my lathe doesn't have an end bearing for the crossfeed screw so there's no spot to position the other end of the line boring shaft.

 

[thestelster]

Ok, I just removed the cross-feed screw to take measurements so that I can make a new one. Well, it just so happens that the screw is in really good condition and within Centralizing 4C specs, (except for 2 spots near the center, for pitch diameter, and not by much.)

The bronze feed nut is pretty loose and some of the threads inside are damaged.

So, I'm thinking not to make a new screw, and just make a new nut.

I was kinda hoping it was in bad enough shape so I can make a new one, but that would take up so much time for little gain.

But a new bronze nut is a definite go.

Does that sound reasonable?

 

[thestelster]

But know I'm second guessing myself. Yes, it might be within spec, but the pitch diameter is different from one end to the other. So if I make a close fitting nut, it might be too tight in some spots.

What to do, what to do?

 

[Darren]

Didn't you already grind a nice tool for this job?

Here's how i did one:

Darren's active projects

Had a bit of time today: Nice trick to dial in the 4 jaw! Never saw that before! Way better than using the tailstock alone.

canadianhobbymetalworkers.com

 

[thestelster]

I was contemplating doing it that way, but the screw is still good, so I was thinking of keeping it as a spare.

I think I will make myself a dimensional print of the screw and nut, reassemble everything, and decide what to do over the weekend. (By the time I finish humming and hawing, the thing could have been finished!!)

 

[Darren]

When i made my nut, i tapped it. Being 9/16" and around 1.25" deep it would have been a pain to single point. I then made the screw to fit the nut. I didn't measure it with wires. Just snuck up on the proper fit. My screw was way worse than yours though. You could make a nut and just see how it fits along the length of the old screw, and if its not acceptable, make a new screw section.

 

[thestelster]

When i made my nut, i tapped it. Being 9/16" and around 1.25" deep it would have been a pain to single point. I then made the screw to fit the nut. I didn't measure it with wires. Just snuck up on the proper fit. My screw was way worse than yours though. You could make a nut and just see how it fits along the length of the old screw, and if its not acceptable, make a new screw section.

Yeah, that's what I'm thinking too. Right now I'm measuring the whole screw.

 

[Susquatch]

Does that sound reasonable?

Yes, no way I would make a new screw. Especially if it's really only out in one place. Like that. I would be aware of the placw that it is out and carry on.

But yes, you need a new nut.

 

[thestelster]

I put the crossfeed screw between centers, and using a cutter, located all the edges and using the DRO was able to get all the required distances from the end. Now that I have a "blueprint", I can go ahead and reinstall it back onto the lathe. And determine my next move.