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sbmathias
04-22-2009, 10:13 PM
I have an old Mitutoyo dial indicator that is apparently somewhat rare. I've never seen another one like it. It has a 360 swivel nose, and the point can also be swing about 110 degrees. Quite useful! At any rate, I was using it the other day, and the whole nose fell out! I soon discovered that it uses 9 small balls that act as bearings for supporting the center rod, and some of these had spilled all over the milling machine table. Fortunately, the table was clean, so I gathered up as many as I could find.

Here it is, in pieces:
http://i219.photobucket.com/albums/cc300/sbmathias/100_1700.jpg
It is approximately in exploded view. You can see some of the small balls in the bottom center black container, and the brass sleeve has holes in it to act as a ball cage. There is a larger ball hidden in the top left bowl, which operates the 90 detents.

I now need to reassemble it. However, I count only 8 balls, not the 9 that I should have. I need to find out several things:
1. Where might I get one or two replacement balls? I measure them at 1mm (0.0394 inches) in diameter.
2. What kind of lubrication should I use when reassembling it? My first guess is good light machine oil, but would welcome a recommendation.
3. I'm somewhat confused as to why it came apart. It doesn't look like there is anything holding it together when the nose is rotated between detents. Maybe I've just been lucky. Or, am I missing something?
4. Does anyone have any suggestions on how to assemble it? In particular, how do you put all the balls in the holes (3-around) and get them inserted without dropping them? A dab of light grease?

Frank Ford
04-22-2009, 10:19 PM
McMaster-Carr has 1mm bearing balls as their stock number 9292K29 for about 6 bucks a hundred.

sbmathias
04-28-2009, 05:16 PM
Frank:
Thanks for the lead. I now have a very small packet of 100 very small balls. Tonight I try to get it all back together.

Edit: All I need to do is drop no more than 99 of them!

rkepler
04-28-2009, 10:30 PM
I brought a 513-302 in from the shop and it seems that you can pull the part holding the contact point out with a medium pull, so I suspect that it'll go back in with a medium push.

I'd try reassembling with a light instrument oil (I tend to using Starrett Instrument Oil) and if you can't keep the balls in place move to a very light synthetic grease. Try standing the brass dingus mounted on the arm straight up, put a ball in a hole and then touch the hole with a small drop of oil on the end of a wire. Move to the next hole, repeat. When done lower the dial assembly onto the point assembly. Maybe try that last move a couple of times for practice first, making sure that you can pull the point and brass back out if needed.

I've got a couple of those and have never managed to pull the stem out like that. But I suspect that I don't use it near as much as you do, I keep it back for the *really* odd setups (that and the Starrett 811s - I'm a sucker for cool gadgets).

sbmathias
04-29-2009, 01:10 AM
Well, I was able to get it all back together, but only with the help of some small tweezers and some light grease. Couldn't just shove it back into place, as the balls are loose, and have to be put back in one at a time, 3-around, so they keep falling out of the "cage" holes. Those 1mm balls are really hard to do anything with. But, it seems good as new now.

I contemplated machining a shallow groove around the stem where the detent ball rides, to help keep the stem in if the detent ball wasn't in one of its detents. Couldn't figure out a way to hang on to it to do that, though. I'll just be careful in the future.

rkepler
04-29-2009, 10:44 AM
Well, I was able to get it all back together, but only with the help of some small tweezers and some light grease. Couldn't just shove it back into place, as the balls are loose, and have to be put back in one at a time, 3-around, so they keep falling out of the "cage" holes. Those 1mm balls are really hard to do anything with. But, it seems good as new now.

I contemplated machining a shallow groove around the stem where the detent ball rides, to help keep the stem in if the detent ball wasn't in one of its detents. Couldn't figure out a way to hang on to it to do that, though. I'll just be careful in the future.


I was thinking about the "missing" groove, and thought I'd pull the stem on mine out a bit to see if there was one. Managed to pull the stem out far enough that it wouldn't go back in. I had to pull it all the way out to put the balls back. I pulled it into a plastic bowl from the kitchen, saw that everything was there so I cleaned and put everything back together.

Those little balls are real fun to chase around in a plastic bowl after they pick up a little static charge. I finally cornered them in a little drop of oil after chasing them around a while with them avoiding the points of the tweezers.

Circlip
04-29-2009, 11:55 AM
Just needs a little "Concentric" thinking. All you need is a tube whose bore is the same size as the outside diameter of the brass sleeve with the balls fitted, long enough to cover all three bearing "Stacks". Place the pin shaft in the end of the brass tube and slide the brass tube into the end holder keeping everything vertical so the balls can't escape sideways.

You should be able to reassemble this without any nasty sticky oil or grease.

Regards Ian.

rkepler
04-29-2009, 08:56 PM
Just needs a little "Concentric" thinking. All you need is a tube whose bore is the same size as the outside diameter of the brass sleeve with the balls fitted, long enough to cover all three bearing "Stacks". Place the pin shaft in the end of the brass tube and slide the brass tube into the end holder keeping everything vertical so the balls can't escape sideways.

It you refer to the image above you'll see the brass tube that fits over the pin into which the balls fit. This tube fits into the indicator body with the flange on the brass on the bottom, so there's no way to hold the balls in place on the brass tube with a second, outer tube while inserting the assembly into the body. I'm sure that Mitutoyo has some tricky method, but a dab of lube did OK for me.

J Tiers
04-29-2009, 11:30 PM
I brought a 513-302 in from the shop and it seems that you can pull the part holding the contact point out with a medium pull, so I suspect that it'll go back in with a medium push.


Not quite.

I've had mine apart, because it jammed up (not the fault of the plunger setup, as I found out).

The detent ball prevents you from sliding back the "head" unless you slack it off quite a bit from where it seems is best for not coming apart.

BTW, mine has been missing one of the balls for quite a while. Does not seem to bother it any, it shows no signs of dragging or other issues.

The jam-up was actually from the dial shifting.... the entire dial assy had shifted so as to jam the dial drive. I had to pull the needle and dial face, then loosen and shift the dial assy over and re-tighten in a position that allowed it free movement.

I was NOT particularly impressed. Mitutoyo quality seems to include a cheezy casting for a body, with lots of fins and flashing on it. While that doesn't actually affect accuracy, it does lower the brand in my estimation. probably silly, but you know..... if the tray table isn't clean, you tend to think the engines are also not well maintained.

Circlip
04-30-2009, 10:11 AM
So does the flanged end fit into the noze piece (The bit with the shaft) first?? As it's seen in the photo?? If so, -- so??

J Tiers
04-30-2009, 10:20 AM
So does the flanged end fit into the noze piece (The bit with the shaft) first?? As it's seen in the photo?? If so, -- so??

Top right photo.

Cylindrical object fits over the visible pin. balls in bottom photo fit in the small holes you can almost see.

Assembly "gozinta" the recess visible in top left photo. The hole nearest the end is where teh screw, spring, and detent ball fit which both hold and index the nose.

Nothing much holds the nose in place, actually, other than the detent ball.

Circlip
04-30-2009, 10:26 AM
Yep JT, thought thats the way it fit, so my tube will still work.

Regards Ian.

rkepler
04-30-2009, 11:08 AM
Yep JT, thought thats the way it fit, so my tube will still work.

How? As I understand it you're suggesting using a tube over the brass and balls as a temporary retainer, but that tube has to be completely removed and clear before the brass and balls are inserted into the indicator body. After removing your tube and before the insertion of the nose piece the balls are not constrained in any way and will simply fall off.

Perhaps I'm missing something, maybe you could explain it so I could understand what you're suggesting.

ligito
04-30-2009, 12:17 PM
Nobody want their balls to fall off.
Does the tube go inside the brass tube?

Circlip
04-30-2009, 03:16 PM
From the photo, the brass sleeve looks to have dimples to locate the balls?

So if you can retain them on the sleeve, this can be pushed into the main body housing first?

The nose piece with the pointer can then slide back into the body?

Have I now got it right??

Regards Ian

Barrington
04-30-2009, 03:50 PM
From the photo, the brass sleeve looks to have dimples to locate the balls?

I think this may be the source of confusion. As I understand it, the 'dimples' are through holes and the brass sleeve is acting as a ball cage, with the balls acting between the main body and the moving pin.


Cheers

rkepler
04-30-2009, 07:06 PM
From the photo, the brass sleeve looks to have dimples to locate the balls?

Nope, they're through holes. The brass sleeve is stationary in the indicator body and serves as a cage for the balls. The pin sticking out of the indicator nose (this is the part the tip drives in & out) rides on the balls.


Have I now got it right??

Nope. There's really no magic to it. The pin goes through the brass with the flange down. Balls go into the holes up against the pin. Pin, brass and balls all go into the indicator body - note that the flange on the brass has to be at the bottom, so there's no way to support the balls with a tube that you pull as the brass and balls enter the indicator.

You might build something with 3 pads to hold in the balls, retracting it as the balls and sleeve enter the body, but since it worked OK this way with very little effort there's no point.

J Tiers
05-01-2009, 12:40 AM
The balls stay in with a little lube..... although that is possibly more than you should use.

I lost one simply because I wasn't prepared for it coming apart like that..... I needed to clean it, and thought the plunger stuff would stay with the main body...... Wrong!

It's a somewhat goofy assembly, but it works.