Thread: Hmm. Haven't taken anything apart lately...

On Thursday a dial indicator was dropped at work so that the stem would not spring back. Consensus was that it was probably bent. It was only a cheapish one (Vertex) so after a few choice words about a lack of knowledge on how some people got through an apprenticeship, a new one was bought and I was given the old one as I'm known for 'tinkering'
I started to take it apart and thought I should have photographed this. I then managed to fix the fault so though I'd better photograph it on the way back together. As taking apart is the reverse of putting together, this is no great problem.
To start with, the bit that I did not touch. Photo on the left shows the 2 gears, hair spring and pinion for the stem rack. Photo on the right just allows you to see the pinion that drives the main needle. So - stem drives pinion which turns gear. Gear drives needle pinion and the needle pinion also drives the accumulator dial (the one that counts the complete revs). This is the one that has the hair spring on it.
P1020396 (Medium).JPG P1020397a (Medium).JPG

The body of the indicator is a hollow cylinder. The mechanism shown above is held on with some screws in circular slots (bottom right in photo below). The pieces that hold the crystal housing on are 3 spring pieces (in the photo held between my fingers)

P1020399a (Medium).JPG
Once the crystal housing is on, no more is done on the front until later. The stem slides in and then a post is attached to prevent rotation (first photo) and a spring hook for the spring return (second photo). Remember those slotted holes? They allow the pinion to be engaged or disengaged. I set the zero on the accumulator by pushing the stem up until it read just under zero, held it there with finger pressure, disengaged the stem so it could return to it's most relaxed state, re-engaged the pinion and then tightened the screws in the circular slots. Note that if you engage the rack too aggressively, it binds.

P1020400 (Medium).JPG P1020401 (Medium).JPG
Now that the accumulator dial is set, the front is finished off. Clockwise from the bottom, the dial face is put in the crystal housing then the white plastic spacer. Put the needle in now. I tried to align it so that it was pointing at zero (with zero vertical) when the accumulator dial was. Then put in the crystal followed by the spring clip to hold it all in

P1020402 (Medium).JPG

Return to the back to screw the lugged cover on.
No photos of the finished object because you all know what one looks like. The problem turned out to be that the rack jumped some teeth when it was dropped so the hair spring was over wound. By disengaging the stem from the pinion it reset itself. I also had to knock a dent out of the crystal housing.

Looks like work gets their indicator back.

Michael

Thanks for that info Michael, I now know what is inside one. Why not tell work it was beyond repair, One can never have enough indicators.
Kryn

I had the same same problem today, ran the carriage into the DI and the DI jammed. Thought it was a bent stem first, but as the stem wouldn't move at all, discarded that idea. Turned out the large gear jumped a tooth and jammed. Remarkably robust these DIs

How much will you charge them tho?

I have a very old 0-1/2" mity that is tight in the stem. I have had it apart several times to no avail.

Dean

Well done Michael. You really are as honest as the day is long, handing it back to them after fixing. Many wouldn't, good on you!

Simon

Michael I may have mis-read your post, but even at minimum needle position (typically around the 11 o'clock position) I believe there should still be a little spring pressure there. I'm never 100% certain how much to set it, and normally settle on 'bout right, based on the two travel extremes.

Unfortunately I've had to repair too many dial indicators, DTIs and micrometers as a result of bulk buy auction "bargains" that really weren't. Indeed I STILL have another 4 DTIs sitting on my desk awaiting new points. Incidentally I can recommend anyone who hasn't seen how a DTI reverses to whip the side plate off one, a very cunning piece of engineering! I'll now know where to send the next batch for processing

Originally Posted by Pete F

Even at minimum needle position (typically around the 11 o'clock position) I believe there should still be a little spring pressure there. I'm never 100% certain how much to set it, and normally settle on 'bout right, based on the two travel extremes.

There is a little pressure there but not much. The DI is listed as 10mm travel and has around 11mm. I've tried to get it reasonably in the middle but we'll see how it holds up.

Michael

Originally Posted by Michael G

There is a little pressure there but not much. The DI is listed as 10mm travel and has around 11mm. I've tried to get it reasonably in the middle but we'll see how it holds up.

Michael

Yeah that sounds similar to what I do, no idea if it's technically correct, but seems to work ok.

The first time I repaired a DI, it took ages to set the small clock needle on zero - PITA. I found if the spring wasn't set with enough load the plunger wouldn't return to zero on a repeatable basis.

I picked up this indicator on ebay for a good price as the plunger would not return. I took it apart this evening. The two issues were that firstly it was gummed up with oil but mainly it had been dropped. These are really solid - heavier than my Mitutoyos. The bezel ring had been deformed and the pinion pushed into the rack so that the spring to return was not strong enough. The three screws visible on the back allow enough movement to adjust the engagement, so after "re-rounding" the bezel ring and cleaning the oil out I now have a Tesa indicator. I could not find one on the Long Island website so I've either got something rare or something fake. I hope that in the next few days they will tell me which.



Michael

As mentioned in another thread, I have been going through my dial indicators and have also spent the evening inside a DTI, in this case a Mitutoyo no.2412-08 0.001"-0.400". The problem with this one is the plunger is stuck fast.
It looks clean and tidy inside but I suspect it has got wet at some point and corrosion has bound the plunger to the sleeve.
It is stuck in the extended position and no amount of hand pressure force will move it.
Any good suggestions on how I should go about trying to restore this dial indicator or is it destined for the spare parts box?

I also have a Mitutoyo No.513-404 0.01mm dial test indicator where the stylus has been broken off leaving the thread in the hole
It is in good condition otherwise and has a fully functioning sister DTI that I am using at present so may just sit there as a donor unit.

The next DTI needing attention is a Parvus P3GA 0.0001" Compac. Here the arm from the stylus pivot (with the small rack on the end) has the two small fingers that grip the pivot broken off. (please excuse the lack of correct terminology for the DTI parts) I also have a Parvus P2GA for parts which has the same arm but also with the same problem. Must be a common fault so no joy with this one.

Please note, before reporting me for DTI abuse, none of them have been damaged by me. All have been obtained in job lots at auction.

One of my saved searches on eBay is Tesa and occasionally dial indicators appear. The solid brass construction is akin to that of Compac's. You need a hefty stand for adequate support.

How did you remove the hand? ( or maybe you didn't? )

Bob.

Originally Posted by Anorak Bob

How did you remove the hand? ( or maybe you didn't? )

The hand holding the indicator is still attached Bob. I always try to keep my hands behind the cutting edge or at least not directly in line with it.

If you were taking about the hand/ pointer on the indicator, I did take that off. I used a pair of fine screw drivers either side of the central boss to pop it off. One day I should really make a proper puller but it is one of those tools where you spend a hour or so making something to use it for a few seconds and every brand would need a different tool.

I did get a response from Rene at Long Island - he says Tesa DIs do exist and mine is likely to be from the 50's as a new model came out in the early 60's. One thing that did surprise me was the use of plastic on it as I would have thought that it was too old for that but it works.

Andrew, if you do decide to take your DTI's apart to fix them, please post the process as it is interesting to see. Although some people think I'm mad taking these things apart, I take the view that there is nothing to be gained by having them sit there not working, but if they can be repaired then you gain in the process.

Michael

Originally Posted by Belair_boy

I have been going through my dial indicators and have also spent the evening inside a DTI, in this case a Mitutoyo no.2412-08 0.001"-0.400". The problem with this one is the plunger is stuck fast.
It looks clean and tidy inside but I suspect it has got wet at some point and corrosion has bound the plunger to the sleeve.
It is stuck in the extended position and no amount of hand pressure force will move it.
Any good suggestions on how I should go about trying to restore this dial indicator?

I have one of those. I'll have a look on how to get into it for you. The thing that seems to solve a lot of issues with a Dial Indicator (DI) is disengaging the rack from the pinion - I should point out it causes other issues - but it seems that if DIs are dropped one of the things they quite often do is jump teeth on the rack which then jams them up.

Michael

Originally Posted by Michael G

On Thursday a dial indicator was dropped at work so that the stem would not spring back. Consensus was that it was probably bent. It was only a cheapish one (Vertex) so after a few choice words about a lack of knowledge on how some people got through an apprenticeship, a new one was bought and I was given the old one as I'm known for 'tinkering'
I started to take it apart and thought I should have photographed this. I then managed to fix the fault so though I'd better photograph it on the way back together. As taking apart is the reverse of putting together, this is no great problem.
To start with, the bit that I did not touch. Photo on the left shows the 2 gears, hair spring and pinion for the stem rack. Photo on the right just allows you to see the pinion that drives the main needle. So - stem drives pinion which turns gear. Gear drives needle pinion and the needle pinion also drives the accumulator dial (the one that counts the complete revs). This is the one that has the hair spring on it.


The body of the indicator is a hollow cylinder. The mechanism shown above is held on with some screws in circular slots (bottom right in photo below). The pieces that hold the crystal housing on are 3 spring pieces (in the photo held between my fingers)


Once the crystal housing is on, no more is done on the front until later. The stem slides in and then a post is attached to prevent rotation (first photo) and a spring hook for the spring return (second photo). Remember those slotted holes? They allow the pinion to be engaged or disengaged. I set the zero on the accumulator by pushing the stem up until it read just under zero, held it there with finger pressure, disengaged the stem so it could return to it's most relaxed state, re-engaged the pinion and then tightened the screws in the circular slots. Note that if you engage the rack too aggressively, it binds.


Now that the accumulator dial is set, the front is finished off. Clockwise from the bottom, the dial face is put in the crystal housing then the white plastic spacer. Put the needle in now. I tried to align it so that it was pointing at zero (with zero vertical) when the accumulator dial was. Then put in the crystal followed by the spring clip to hold it all in



Return to the back to screw the lugged cover on.
No photos of the finished object because you all know what one looks like. The problem turned out to be that the rack jumped some teeth when it was dropped so the hair spring was over wound. By disengaging the stem from the pinion it reset itself. I also had to knock a dent out of the crystal housing.

Looks like work gets their indicator back.

Michael

we adelaidians are glad your in adelaide Micheal should we ever drop a DTI, Dial Indicator ..or what ever...lol

If I had ever dropped one I reckon I would have just gone and bought a new one...

now what was your address ....for the others