I managed to lose some of the balls on my CNCFusion X2 ballscrew. I was going to order a pack of replacement balls from the local bearing supply house, but when I miked them they were an odd size. I expected .1250, but I keep getting .1238.

This is with a 0-1 micrometer, using the friction drive on the thimble. I know that the balls make a point contact on the anvils and are a bit springy, so they're probably bigger than .1238... but what size balls *should* have been in the ballnut to start with? Do standard 1/8 inch balls ordinarily measure .1250? I've only heard about oversize balls, and a couple of sites I've hit list oversizes, but not undersizes.

i lost mine, found them and put them back in, and i couldn't get it to work quite right. i just send mine back to cncfusion for a small charge they fixed it up for me and now all is good. Im sure they would be more then happy to just send you the balls or something

I asked CNCFusion as well; he said the balls should be .1250. I'm confident my micrometer is correct; I set it with gage blocks and I used to do a lot of measuring to tenths.

That leads me to believe the missing .0012" is due to the distortion of the ball by the micrometer.

So, (and the reason I brought this up over here instead of just asking CNCFusion) how *do* you measure teeny balls like that?

I asked CNCFusion as well; he said the balls should be .1250. I'm confident my micrometer is correct; I set it with gage blocks and I used to do a lot of measuring to tenths.

That leads me to believe the missing .0012" is due to the distortion of the ball by the micrometer.

So, (and the reason I brought this up over here instead of just asking CNCFusion) how *do* you measure teeny balls like that?

Perhaps you wound up with Chinese balls?:)

I wish NC CAMS was still around. He would definitely know.:(

Yes he would, and you can't wind anyone else up by telling someone a generic .0005 press fit is the correct fit for any bearing.

First question is about your micrometer. Does it have lapped carbide faces? Did you clean off the faces with a sheet of paper before setting with jo blocks? How is the friction thimble set? I never much liked the ratchet or friction thimbles and used to use a sense of feel. Now that the hands don't work so well, I have to use them.

With a micrometer that has no carbide faces, there is a possibility that you are reading the mic wrong due to surface pressure. A Jo Block is a surface contact across the entire face of the anvil. Balls are point contact. Carbide faces don't deform so they give a truer reading. The same thimble pressure for a surface contact measurement will be magnified in a point contact and give a poor reading when using non carbide faced micrometers. Even then you need a light touch.

Just a thought...could you get a ball of the correct size .1250 (no idea what that is btw...is it 3.1mm?) and measure it with your mic? if you then measure that one @ .1238 then you know to throw the mic in the trash (see what I did there...spoke a foreign language) On a side note....sorry to hear you lost your balls! Mine have dropped and I've struggled to find them a few times.....I'm quite proficient at reassembling ballscrews after having used them for some time. :cheers: I measure mine with a vernier.

Yup he will be missed Toby!

Just a thought...could you get a ball of the correct size .1250 (no idea what that is btw...is it 3.1mm?) and measure it with your mic? if you then measure that one @ .1238 then you know to throw the mic in the trash (see what I did there...spoke a foreign language) On a side note....sorry to hear you lost your balls! Mine have dropped and I've struggled to find them a few times.....I'm quite proficient at reassembling ballscrews after having used them for some time. :cheers: I measure mine with a vernier.

Yup he will be missed Toby!

I haven't worked with any machine that has dropped its' balls, but who knows what will happen in the future.

I suggest recalibrating that mic before trashing it. You should check the anvils with a .125 Gage Ball in various places after recalibrating. If it reads like crap still, slam dunk it in the nearest trash receptacle.;)

I mic'd the balls in my roton ballnuts a while back and they were the same size you have come up with. I wanted to go oversize to eliminate some backlash so I ordered some .125 balls from enco. Unfortunately I get the same amount of backlash but I measured the enco balls at exactly .125 so I believe your mic is correct.

Rick

From your post it sounds like the balls you were actually measuring were those at the store, not some of the ones that fell out of your machine. An accurate 1" mike should measure a dead on 0.1250 on the correct ball.

I lost some balls a while back and bought new ones on Ebay. They had standard .125 plus over and under sizes available. I ordered .1250 balls and just got out the 3 dozen that were left over and they measure a dead on 0.1250 with my Fowler Helios mike.

If you can't find the correct size PM me and I'll ship you the 3 dozen if that's all you need.:cheers: