Repair a Mitutoyo DTI?

[raynerd]

Hi Guys
I have a lovely metric mututoyo DTI which I use very often in my shop as "best". I picked it up to use it last night and it was broke, there was some play in the finger without registering on the dial and with an obvious push on the finger, it gave some random jumping movement on the face.

I opened up the 6 screws on the side which removed a plate on the body of the guage and there are seemingly only a few parts.

At the top is the gear which seems to move the scale on the gauge. Attached to that is a piece of metal with a rack of teeth at the top which engages the gear and at the bottom interacts with the finger and then at the bottom, there is a piece attached to the finger which impacts the middle section. There is also a spring on the inside of the side plate.

I just can`t seem to get it loaded, there is always play in the finger which gives no response to the dial. Any help appreciated. Pictures attached later tonight if no one can chip in before hand.

Chris 

[joshagrady]

Long Island Indicators (Link) has all sorts of information to help you on your way.  If you have the patience and the dexterity o make a clock, the indicator should be the sort of challenge you'll appreciate. 

[krv3000]

HI Chris dont no if this will hellp but will have a go   the stiles scruws in to the stilis holder and on the side of the stiles holder ther is a fricshon jont to the lever of the mecanisem is this still a snug fit and not to slack is the prelode spring in good order  and is the dile nedel stil a tite fit on its shaft  is the stiles holder siting  nice in its two pivet pointes a part from that and  with out looking at it i wood say its gowing to end up in the bin

[John Swift]

Hi Chris

it must be 15 to 20 years ago but from what I remember

two small gears are driven by the rack

one drives a large gear that in turn drives another small gear connected to the  pointer

the second gear train is the same ratio but the larg gear is connected to the spindle with a hair spring

this provides the tension to take up the backlash  


I guess an alternative arrangement could use concentric spindles

John


edit   oops wrong indicator  but you still need to look for missing teeth , broken springs and pivots

[krv3000]

HI is it ded has it ended up in the bin

[75Plus]

It sounds like you have a broken pivot on one on the arbors. This allows the gear to move randomly. You might have a watch repairman look at it since the mechanism is watch like.

Joe

[raynerd]

I was going to post pictures but I`m currently out on work...I did manage to repair it and nothing was broken. With some observations I found out that the little hair spring wasn`t applying any pressure onto the little ratchet like piece that it meant to push to take up the backlash. Equally, I couldn`t figure for quite a while how the spring could possibly positioned to engage it. It was simply a case of pushing the ratchet piece (I don`t know its real name, but the piece with the rack teeth that apply move the gears) and finger to one extreme side, the slipping the cover on then moving it back a fraction to engage the spring in every position from that extreme point. I have a feeling that when working on my lathe, I knocked it and the finger hit the bench which I can only presume caused the hair spring to come out of position. It just needed putting back again.

I didn`t think I could possibly have fixed it that easily (once I`d realised what to do) but I`ve really given it a good test and used it a few times and it seems to be working perfectly. Maybe I was lucky, but it certainly is fixed!

[krv3000]

Hi glad you have put it right