ID this part!

[Beerhippie]

You all know how frustrating it is trying to find a part when you don't know its exact name?



Drive nut? Whatever it is, it sure looks like I need a new one--and soon.

I'm not sure if the drive screw is single- or double-lead, so not real sure on thread pitch (or, for that matter, type):



Calipers are set to 1 inch. Major dia of the screw is 0.495--I'd call that 1/2". Everything on this machine is SAE, so I doubt that the one part would be metrical. Mounting holes for the lead screw (?) are 1 1/2" OC

Any help appreciated! The company that made the machine sure ain't helping any....

 

[Beerhippie]

Closest I've come so far: https://www.mcmaster.com/products/nuts/lead-screws-and-nuts~/nut-type~platform/thread-size~1-2-10/

But no mounting holes....

 

[no704]

Anti backlash feed nut. Need more machine info.
Pretty steep helix, probably a multiple start. Easier to tell at the ends. Acme, maybe hard to see with all the shmoots on it.

 

[PCustoms]

It's likely proprietary to the lead screw, and I've always changed them as an assembly as they done wear in.

 

[Beerhippie]

Anti backlash feed nut. Need more machine info.
Pretty steep helix, probably a multiple start. Easier to tell at the ends. Acme, maybe hard to see with all the shmoots on it.

Here's the machine it's part of:



Can-I-Bus can depalletizer by Ska Fab. It's old--pretty much one of the first they built, which is why they aren't able to just provide a spare of a part#.

Here's where the screw and nut go:



The screw runs the pusher plate that pushes a tier of aluminum beer cans off the top of the pallet and onto the conveyor at the right. Not much pressure on it as the cans are empty.

The tech I spoke to today at Ska believes that the screw may be a five-lead Acme. I need to take one of the ends off to be sure, but the Allen-heads of the tiny screws that retain the collars on the ends of the screw are stripped out. I hate Allen heads for just this reason. I'll get up there tomorrow with drill and left-hand drills and see if I can get them out to find out how many leads the screw has.

 

[no704]

Good luck with the screw removal. Might want to put a little heat on that collar.

 

[Beerhippie]

Good luck with the screw removal. Might want to put a little heat on that collar.

Yeah. The powers-that-be in the office bought this piece of equipment used. I first saw it when it arrived here. It looks like it's lived most of its life near the coast--all bare metal is pretty rusty. Fortunately, things like that lead screw have been kept lubed. It was while cleaning and re-lubing the screw yesterday that I noticed that the nut was falling apart and has lots of play.

Considering that this is not a precision application, is there any reason to use the anti-backlash nut?

 

[CapriMikeC]

Check with Thomson, they have lots of screws like that. https://www.thomsonlinear.com/en/products/lead-screws

 

[alfadan]

I guess I don't see any provision for adjusting backlash.

 

[Beerhippie]

Check with Thomson, they have lots of screws like that. https://www.thomsonlinear.com/en/products/lead-screws

Thanks!

I'll take the nut off of the machine tomorrow and figure out just what I need to replace. It seems that the actual nut is pressed or screwed into the mount--I'd thought it was a single unit.

 

[Beerhippie]

I got the part removed from the depal and cleaned up some.



That's as far as I'm able to tear it down without risking further damage. It's rough, but still working--and I'll need it working again no later than Thursday afternoon.

I'm trying to find a nut that will fit that mount, which, of course, would be easier if I had the old, plastic nut out of the mount. There's a tiny Allen set-screw on top of the mount, but removing it doesn't seem to do anything.

The existing nut is polymer and pretty torn up. Best I can determine, those exposed external threads are 3/4"-16. The nut recommended by the manufacturer is 15/16"-16. I'm pretty sure mine is 3/4" dia. Internal threads are, indeed, five-lead, 1/2"-10 Acme.

Here's the one that was recommended:

https://www.mcmaster.com/95072A145/

I know there's not a chance in hell of finding a 15/16"-16 tap around here, so want to be more sure before I order.

 

[Waterlooboy2hp]

I got the part removed from the depal and cleaned up some.



That's as far as I'm able to tear it down without risking further damage. It's rough, but still working--and I'll need it working again no later than Thursday afternoon.

I'm trying to find a nut that will fit that mount, which, of course, would be easier if I had the old, plastic nut out of the mount. There's a tiny Allen set-screw on top of the mount, but removing it doesn't seem to do anything.

The existing nut is polymer and pretty torn up. Best I can determine, those exposed external threads are 3/4"-16. The nut recommended by the manufacturer is 15/16"-16. I'm pretty sure mine is 3/4" dia. Internal threads are, indeed, five-lead, 1/2"-10 Acme.

Here's the one that was recommended:

https://www.mcmaster.com/95072A145/

I know there's not a chance in hell of finding a 15/16"-16 tap around here, so want to be more sure before I order.

========================================================================================
https://www.ebay.com/sch/i.html?_nkw=15/16"-16+tap+&LH_TitleDesc=1 ------- John

 

[PCustoms]

I got the part removed from the depal and cleaned up some.



That's as far as I'm able to tear it down without risking further damage. It's rough, but still working--and I'll need it working again no later than Thursday afternoon.

I'm trying to find a nut that will fit that mount, which, of course, would be easier if I had the old, plastic nut out of the mount. There's a tiny Allen set-screw on top of the mount, but removing it doesn't seem to do anything.

The existing nut is polymer and pretty torn up. Best I can determine, those exposed external threads are 3/4"-16. The nut recommended by the manufacturer is 15/16"-16. I'm pretty sure mine is 3/4" dia. Internal threads are, indeed, five-lead, 1/2"-10 Acme.

Here's the one that was recommended:

https://www.mcmaster.com/95072A145/

I know there's not a chance in hell of finding a 15/16"-16 tap around here, so want to be more sure before I order.

That sure looks like the old Hayden Kerk ball screws unused to play with. The nut on the right should adjust the "guts" to take up backlash in combo with the spring. I'd have to see better shots of the left side to remember how that bushing and spring are supposed to fit.

 

[Beerhippie]

========================================================================================
https://www.ebay.com/sch/i.html?_nkw=15/16"-16+tap+&LH_TitleDesc=1 ------- John

Ooh! Free shipping from China... reckon it'd be here by next Thursday?

That sure looks like the old Hayden Kerk ball screws unused to play with. The nut on the right should adjust the "guts" to take up backlash in combo with the spring. I'd have to see better shots of the left side to remember how that bushing and spring are supposed to fit.

The spring and keeper are supposed to snap over the fingers on the end of the nut. The fingers are too worn to retain them. I don't see how they'd take up backlash in this application.

 

[545_days]

To figure out single vs. double, triple, etc. leads, wrap a piece of string in the valley of one lead down the screw. In a single lead the string will be in the next valley after one revolution, double will skip one valley, triple will skip two, and so on.

 

[Beerhippie]

To figure out single vs. double, triple, etc. leads, wrap a piece of string in the valley of one lead down the screw. In a single lead the string will be in the next valley after one revolution, double will skip one valley, triple will skip two, and so on.

I was able to simply count the leads once I had the nut off the screw--but that would be a handy trick. I'll remember it.

I honestly didn't know drive screws came in so many different number of thread leads. None of the equipment we've had before this depal used a drive screw. The same function was done with a pneumatic cylinder or a belt. Nothing about this machine really justifies the use of a high-precision drive with a stepper motor, as everything is controlled by feedback. But that's just what this one has.

[rant] As an old guy, I find the modern desire to throw computers (PLCs and touchscreens) into everything unnecessary and irritating. I could build a depalletizer with a handful of relays, microswitches and a couple of relay-output optical sensors. It ain't rocket surgery. I've built several control systems around the brewery using relays and analog integrated circuits, and these confuse the hell out of the young folks. [/rant]

Now, back to searching for the right drive nut....

 

[Beerhippie]

That sure looks like the old Hayden Kerk ball screws unused to play with. The nut on the right should adjust the "guts" to take up backlash in combo with the spring. I'd have to see better shots of the left side to remember how that bushing and spring are supposed to fit.

Thinking it over, I now see how the anti-backlash is supposed to work. The spring and "bushing" work against the swell of the "fingers", which are threaded, to maintain the threads in full contact with the screw.

But, once again, it's way overkill for this application. A bicycle chain with a reversible gear motor would be just as good, and much cheaper.

 

[Beerhippie]

I couldn't find anything ready-made to suit my needs, so I guess I'll just have to cobble something together. I've spoken to a tech at the company that made the machine, but they're basically worthless and very poor at communicating--I think they're in the 4:20 time zone.

I ordered one of these:



one of these:



and a 15/16"-16 tap. I'll make a stand-off from UHMW or aluminum to match the 1 5/8" height-to-center I need and bore some new mounting holes to match the new mounting block. I sometimes wish my plant maintenance machine shop was composed of more than some cutting tools and a drill press.

In the meanwhile, I put the old nut back on the machine and I'm keeping my finger crossed that the two or three threads left intact will hold up 'til I get the new set-up made.

 

[Farmerjonathan]

Could you take the old nut to a competent machine shop and have them make you a couple?

 

[Beerhippie]

Could you take the old nut to a competent machine shop and have them make you a couple?

For about three times what I paid for the parts to do it myself, yes.

 

[no704]

Look at Nook kinda looks like something they would have.

 

[Beerhippie]

What a PITA this is turning out to be!

The nut I show above arrived yesterday. I figured I'd best check it to be sure, so I climbed up to the top of the depal--8'--and freed up one end of the screw. The nut threads on... about 1/8 turn and stops--like the thread pitch is wrong. Problem is, that seems to be the only thread pitch in 1/2", 5-lead. Maybe metric?

Anyhow, easiest solution is to throw more money at it--I ordered a new drive screw.

 

[paranoid56]

sooooo, that part is no longer made. i have them on my cnc router and stopped being able to find them last year. is yours totally dead? i might have some old used ones laying around. i assume its a .5 5 start acme thread.

 

[Beerhippie]

sooooo, that part is no longer made. i have them on my cnc router and stopped being able to find them last year. is yours totally dead? i might have some old used ones laying around. i assume its a .5 5 start acme thread.

From my measurements and count, it's 1/2" 10 tpi, 5 lead. But the Acme nut I bought from McM-C in that size doesn't fit!

So I simply bought the corresponding screw to go with it. The nut threads perfectly onto that screw. As soon as my 15/16" - 16 tpi tap gets made and shipped here from overseas, I'll mate the nut to the pillow block I also bought and get it together. Just hoping the scrap of old resin nut it currently runs with holds together that long!

I do have a back-up plan just in case. It might involve me, standing on a ladder with a big stick feeding cans off the depal for eight hours....

 

[paranoid56]

it should be this one https://www.mcmaster.com/catalog/130/1391/95072A145
however its not anti backlash, so you will have some backlash. its hard to tell if thats ok or not for thta machine, but, for my application it wasnt. I have some that have a bit of ware, and a few new ones that i need for my machine as i go though them about 2 a year. I did end up replacing one axis with a ball screw as it was cheaper lol. those leadnuts were originally sold by avid cnc but they no longer carry them

 

[paranoid56]

also, by the pic i dont see anything wrong, but what issue are you having with the leadnut?

 

[Beerhippie]

That's the part I bought, thinking the same thing--should be it. It just doesn't fit. Maybe the old screw is screwed?

A little backlash on this machine is no problem at all. My next idea was to just replace the entire drive system with a bicycle chain and some sprockets. It would be fine. Replacing the drive nut and screw should get the machine through the rest of my lifetime, so I won't get to do that.

If you look at my pictures above, the old nut is essentially falling apart. It's no longer one piece or one assembly. It looks like there are about two threads on the nut still engaging the screw.

 

[paranoid56]

yea it should have screwed on. as yea maybe the end of the lead screw is messed up some.
here is a new one to give you an idea

 

[paranoid56]

i have a used one that has full threads but is "used" for my application, IE i cant have any backlash lol. this one has a few thou. happy to send it your way.

 

[Beerhippie]

Thanks, Paranoid.

Two weeks and two hundred dollars ago, I'd have jumped on that. With the new bronze nut, I see this repair outlasting me.

I guess it would still make good sense to have a spare of the nut on hand. Never know, do we?

Nice to know that the nut does unscrew from the pillow block. I'd removed the set-screw, but reasonable force didn't get the old nut to move and I need it to keep liming along until I can replace it.

When I pull the old screw off, I'll see if the threads are just a little munged at the end. If so, I can return the new, hundred-dollar screw I bought. Maybe. I've never tried a return to McM-C before.

The reason the nut on our machine got so screwed up was that no one had noticed that the entire drive train---mostly the motor and the nut itself--were barely retained as the bolts had mostly fallen off. The crew that runs this machine are up there a couple of times a day and didn't notice the motor hanging by one bolt?

 

[Beerhippie]

The final part--a 15/16" 16 tpi tap--showed up today and the new nut is ready to install!



Spacer is aluminum and UHMW poly. It brings the center height up to the desired 1 5/8"

I'll get it installed this weekend.

 

[Beerhippie]

BTW: If anyone has need of a cheap, MIC 15/16-16 tap--only used once on aluminum, let me know. I'll be glad to pass it on. I'm sure I'll never use it again.

 

[Beerhippie]

Here's the new nut installed:





I need to get back up there tomorrow and give that plate a goodly cleaning. I also need to fine-tune the limit switches, but the new nut runs smooth as butter.

This new nut isn't a zero-backlash nut, but if the location is within a 1/4" or so it's fine--and all the location is from feedback, not CNC.