table Nuts

[befunovo]

Has anyone made improvements to or replaced the x-Y nuts? My backlash is getting excessive I feel (0.020" to 0.030") and was wondering if there are higher quality replacement ones out there or do I have to make my own? I tried adjusting them, but they are pretty loose.

Thanks.

Brian

[Randall]

tre is an adjustment I believe on the nut. Have you tried that?
Randy

[befunovo]

Yes, I tried to adjust them. Was looking at making the same thing, just trying to get higher quality threads in them. The lead screws seemed fine.

Brian

[BillTodd]

Not IH but perhaps similar:

How about this simple mod:

I sawed it across the split, faced both sides, the screwed the pair onto the lead screw. I used the original Allen bolt with a spacer and washer to lock the adjuster nut (see pic); It works far far better than the bendy original




X nut mod

My roller nut replacement design and build
http://www.cnczone.com/forums/showth...=13593&page=36

[LUCKY13]

That mod would work great, it allows you to keep the threads in the ajustment part flat ( the little extra part with threads in it) and it could be bolted solid with the use of shims to get the backlash eliminated. I believe it would wear better than the bendy setup, and if the proper preload is applied with the shimming it should last very good with regulor lubing. It also should allow the screw to turn much easier than using the bendy method, less force to rotated it then.


Thanks for posting this, I have a little X1 mill with bendy type nuts I will do this mod to pronto.


The original posters nuts may have the threads warn out, sometimes the little ajustement part gets bent out of wack also. It may help to take the nut off, rebend this part back out, then when reinstalling be carefull that you dont take the ajustment to far. It just needs to litely place pressure against the thread so that it pushes the screw in a direction that removes the slack. Once it reaches that point in the ajustment thats all it needs. I don't know if you have looked at them real close, you might have just ajusted them without removal. But check to make sure the mounting for the nuts is not loose, mine did this once and I would try to ajust with no help. After taking the table loose it was easy to see what was going on. Also the slack can come from other erea's of the mounting, .020 to .030 is a lot and may be in the end bearing assy.


I dont know why someone doesn't make a two part nut that has sliding pins between them with screws to set the preload. The right design could let it wear on either side of the threads with a outward or inward preload. Much like a double ball nut except with pins to keep the second nut from turning.



Jess

[BobWarfield]

Depending on your budget, it'd be nice to swap over to ballscrews.

You'd need 48" for the X axis and 28" for the Y-axis. To go with 0.75" diameter / 0.2" lead (same as the IH CNC kit), with preloaded ballnut assembly, this would cost:

X-axis ballscrew: $125 (includes cut to length and annealed one end to machine)
Y-axis ballscrew: $85 (includes cut to length + annealed on one end)
2 ballnuts @ $125 each = $250.

So you're looking at circa $460 for Rockford ballscrews from Automation4Less. There may be other cheaper suppliers.

I tell you from experience those ballscrews are silky smooth compared to the old leadscrews. Crank in a little preload and I don't think they'll backdrive much nor will they have backlash to worry about. Friction inside the screw is low enough they should last a long time, and you'd be set to CNC at a later point. The brackets are very easy to make too.

Cheers,

BW

[BillTodd]

and it could be bolted solid with the use of shims to get the backlash eliminated

You don't need shims, the adustable part simply screws towards the fixed part to remove backlash.

If you have some scrap brass and aluminium , a few days and about £30 to spend on bearings etc. try making your own rollers nuts. You will be amazed.

[EvanVH]

Originally Posted by befunovo Has anyone made improvements to or replaced the x-Y nuts? My backlash is getting excessive I feel (0.020" to 0.030") and was wondering if there are higher quality replacement ones out there or do I have to make my own? I tried adjusting them, but they are pretty loose. Thanks. Brian

I have an old (1963) knee mill. It has about .070" backlash. I always approch
the edge in the same direction as I did with my edge finder. If the handle was turning clock wise when I was finding the edge or my zero point then I would always approuch each feature that related to that zero by turning my handle clock wise. To get good accurace out of any mill the geometry that the mill was in when you zeroed the axis must be repeated when you mill/drill any feature in that axis.


All of my work is done in Conventional milling. The only time that I climb mill is for a finish cut off .005 - .010.

So................................my .02 cents worth


Evan

[EvanVH]

Originally Posted by BillTodd You don't need shims, the adustable part simply screws towards the fixed part to remove backlash. If you have some scrap brass and aluminium , a few days and about £30 to spend on bearings etc. try making your own rollers nuts. You will be amazed.

I just read the thread on no backlash nuts. Great read and an even greater idea.

Thanks bill




Evan

[befunovo]

Lots of good points all. I really like this idea. Instead of cutting it and facing them flat, I will make a new "pinch" nut. I already have a tap for the acme thread, make it about an inch long and it should wear well.

About the old pinch design, I think you are right about the angle. As you tighten it is, you are cocking it at an angle. It was tight for awhile, but quickly wore away. A wide "jam nut" design would work well. I will try that.

Still need to read the other screw thread linked.

Brian

Originally Posted by BillTodd Not IH but perhaps similar: How about this simple mod: I sawed it across the split, faced both sides, the screwed the pair onto the lead screw. I used the original Allen bolt with a spacer and washer to lock the adjuster nut (see pic); It works far far better than the bendy original X nut mod My roller nut replacement design and build http://www.cnczone.com/forums/showth...=13593&page=36