[Fiero Addiction]

I didn't realize it until I started looking at part numbers, these screws are left hand. The Thomson part number for the nut is 8106-448-026, and the matching screw is 190-9099 sold per foot. Wiper kits are not available for this nut. A zero lash preloaded nut part # 8106-448-019 is available and it takes wiper kit 8106-101-002. This should be a direct fit without modification, it is a longer nut but I think there is plenty of clearance for it. The new Patriot machines without gearbox may use right hand threads as there's no reason to use left hand on a CNC only machine.

[BlackICE1]

Has anyone done any mods on the current version to reduce the backlash?

[MichaelHenry]

Your mob on the other side of the pond will be more familiar with that model.

Will it be worth rebuilding?

A bridge mill.....I take it that means a fixed gantry and moving table........Linear ways?....you could be in for more surprises in that department.
Ian.

It's commonly referred to as a 3-in-1 design, I think: drill press, lathe, and milling machine in one unit and on the low end of the hobby budget spectrum. Check the Shopmaster web site for more details.

Mike

[smallblock]

Another thing I found was that NOOK wanted a really high price for the wiper kit- almost as much as the ball nut itself. I never had any problems with chips in mine because the Shoptask had full shields over all the screws- as long as you didn't use compressed air to blow stuff around they always stayed clean. If you decide to replace them, I would look at the Chinese C-7 type that Shopmaster uses now. The ball nut is the same diameter as the original acme screw nuts and will slip right into the original bracket. The screws are a lot bigger- about 7/8" and you can buy them on E-Bay pretty cheap. Some of the Chinese sellers will even machine the ends to your specs for a low price. You won't find any left hand ones though- with CNC, LH screws are becoming a thing of the past.

[Fiero Addiction]

On the Tri-Power the ball nut has external threads for mounting, it screws into an adapter that fits into the mounting block. I think you could take a second nut and screw it in from the opposite side, then turn the second nut in or out on the mounting threads to cause just enough pitch variation to preload the nuts. Aside from a small set screw to lock it in place there would be no modification required. The pictures should show what I'm trying to describe.

Attachment 263554
Attachment 263556
Attachment 263558

[victorofga]

just my 2 cent..
if ebay selling 3 ballscrew for 100, about 35 each, then it just doesn't wort to fixing at all..
balls are hardened while screw is not.. I mean rolled screws are not hardened..
when it is worn all help could be regrinding what is way more cost..


3 Lead Screws ballscrews Ball Screws 1610 350 800 1350mm C7 for CNC Router | eBay

while these screws are new they have use to be 0.02mm backlash.. (0.001 in)

================================================== ====

@ handlewanker.. the welding is ensure the absolute backlash free state :-)

[Fiero Addiction]

just my 2 cent..
if ebay selling 3 ballscrew for 100, about 35 each, then it just doesn't wort to fixing at all..

They are $45-55 each after shipping, and you also need to consider the extra work to fit them. Those are plain screws with no end machining. That's a whole lot more work than replacing balls. My screws are worn beyond repair and I am considering the Chinese screws as replacement, but I think in most cases it would be far more economical to re-ball than to replace. And with a little effort I bet you'd have a better screw than one that cost $35.

The .631/.20 Thomson screw is $20/foot and $30/nut so not a huge difference in price to stick with inch threads and still be able to use the dials and geared threading capability. I have no idea how the low end Thomson screws compare to the Chinese screws, but the price isn't too far off.

balls are hardened while screw is not.. I mean rolled screws are not hardened..

I don't believe that is true. The rolled Thomson and Nook screws are hardened and I'm sure most others are too.

I still think adding a second ball nut for $30 is a good idea to eliminate backlash on a screw that's new or in decent shape.The same could be done with a flange mounted nut but it would require a little more work.

[uberlinuxgeek]

Update. Took my screws apart and mic the balls at .124 to .125. I have new .125 stainless ones on order to be here tomorrow. My machine is new and there are no significant wear. Some stated about wear, that is not the issue. The issue is the ball screw balls not being uniform causing the issue I am seeing. Across the entire axis movements there is the same issue, play inside the ball nut due to poor qa with balls. I will post update once all balls have been replaced with quality ones. Fastenal caries .125 balls of many grades. If I choose to oversize the balls I found a couple good sources too on the net.

[countryguy]

Cool! Good to hear. HAve a PN# or a Fastenal URL? I poked their search engine w/ balls and stainless and tossed in bearing too. I cannot get anything good up? ;-)
Thanks T. JJ

[uberlinuxgeek]

Hello Jeff,
Url for their .125 is http://www.fastenal.com/web/products/_/Navigation?term=&termca=&termpx=&sortby=webrank&so rtdir=descending&searchmode=productSearch&filterBy VendingMachine=&r=~|categoryl1:"600930%20Raw%20Mat erials"|~%20~|categoryl2:"611735%20Ball%20Stock"|~ %20~|categoryl3:"600931%20Balls"|~%20~|attrdiamete r:150|~
I am just starting with 302 stainless grade 100 to start was only 6$ for 300 seemed cheap start if they do not pass mic I am not out much and will find a better source or move up grades.

[Fiero Addiction]

Toolsupply on Ebay has them in .0001" increments.
ToolSupply ballscrew balls

[uberlinuxgeek]

Thanks for the eBay info. Ordered up 3 different sizes. Turns that these balls caused some binding. So put back the old for now and ordered a few sizes so that I can tune these right for each axis.

[BlackICE1]

How uniform are the screw dimensions? If they vary a lot then only smaller balls will prevent binding at the cost of more backlash.

[handlewanker]

Hi, If you do get binding and at different places, then the screw is probably worn in places and won't get better.

If you have the room you could try fitting two ball nuts to the screw(s) with the flanges back to back and a hard rubber spacer between them with longer screws to pull them together to make a double ball nut that can be adjusted to cater for the loose and tight parts.

This will allow you to fit slightly loose balls to the nuts and take up the backlash by adjusting one ball nut against the other to give you total zero backlash forever (virtually).

If you try to jam oversize balls into the nut you'll damage the tracks by ball denting them and that's a total throw away situation.
Ian.

[gio666]

They are $45-55 each after shipping, and you also need to consider the extra work to fit them. Those are plain screws with no end machining. That's a whole lot more work than replacing balls. My screws are worn beyond repair and I am considering the Chinese screws as replacement, but I think in most cases it would be far more economical to re-ball than to replace. And with a little effort I bet you'd have a better screw than one that cost $35.

The .631/.20 Thomson screw is $20/foot and $30/nut so not a huge difference in price to stick with inch threads and still be able to use the dials and geared threading capability. I have no idea how the low end Thomson screws compare to the Chinese screws, but the price isn't too far off.



I don't believe that is true. The rolled Thomson and Nook screws are hardened and I'm sure most others are too.

I still think adding a second ball nut for $30 is a good idea to eliminate backlash on a screw that's new or in decent shape.The same could be done with a flange mounted nut but it would require a little more work.

Where are you finding Thomson ballscrew for 20 a foot and $30 for ballnut?

[gio666]

just my 2 cent..
if ebay selling 3 ballscrew for 100, about 35 each, then it just doesn't wort to fixing at all..
balls are hardened while screw is not.. I mean rolled screws are not hardened..
when it is worn all help could be regrinding what is way more cost..


3 Lead Screws ballscrews Ball Screws 1610 350 800 1350mm C7 for CNC Router | eBay

while these screws are new they have use to be 0.02mm backlash.. (0.001 in)

================================================== ====

@ handlewanker.. the welding is ensure the absolute backlash free state :-)

You can tell that from looking at picture they are 0.001 ?

[gio666]

Thanks for the eBay info. Ordered up 3 different sizes. Turns that these balls caused some binding. So put back the old for now and ordered a few sizes so that I can tune these right for each axis.

Chance are you will lock up ballnut with wrong size bearing, they are make to fit the ones they came with , It is more the quality of the ballnut,. IF you got 10 pitch and has plastic lane changes , it more to do with ballscrew and ballnut it self
Have you even check runout on machining, check straightness on table? Any ballnut with plastic lane changer , are a waste of money

[gio666]

Hi, If you do get binding and at different places, then the screw is probably worn in places and won't get better.

If you have the room you could try fitting two ball nuts to the screw(s) with the flanges back to back and a hard rubber spacer between them with longer screws to pull them together to make a double ball nut that can be adjusted to cater for the loose and tight parts.

This will allow you to fit slightly loose balls to the nuts and take up the backlash by adjusting one ball nut against the other to give you total zero backlash forever (virtually).

If you try to jam oversize balls into the nut you'll damage the tracks by ball denting them and that's a total throw away situation.
Ian.

If you have to use 2 ballnut , it means more you bought garbage, you should have no bachlash with good quality single ballnut . You will not damage ballnut or ballscrew,with wrong bearings , the bearing if to tight will exploded and shatter

[Fiero Addiction]

Where are you finding Thomson ballscrew for 20 a foot and $30 for ballnut?

McMaster Carr
5966K25 $19.47
5966K16 $31.23

I haven't purchased these and McMaster doesn't list manufacturers, but I found several posts on this forum and others saying they are Thomson. They are the cheap rolled screws and non preloaded nuts.

I am certainly no expert on ball screws, but according to my research there are three common methods that manufacturers use to create a preloaded ball screw/nut assembly with zero backlash.
1. Selective fitting of precision balls.
2. A single nut with slight pitch variation.
3. A double nut.

I don't think anyone here expects to create a $1000 ballscrew from a $30 nut and a rolled screw, but it is possible to reduce backlash using method one or three. This isn't something new, it's been done many times.

[smallblock]

If you have to use 2 ballnut , it means more you bought garbage, you should have no bachlash with good quality single ballnut . You will not damage ballnut or ballscrew,with wrong bearings , the bearing if to tight will exploded and shatter

X Zero,
If you are hoping to get people to look at your product, just buy some advertising space. Your negative comments combined with atrocious spelling and grammar are doing you no justice.