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Dti Stylus

Discussion in 'METROLOGY - MEASURE, SETUP & FIT' started by Pmma-Granville, Jan 10, 2017.

  1. Pmma-Granville

    Pmma-Granville United Kingdom Active Member Active Member

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    Hello!
    Iv salvaged a DTI from work, only problem is some idiot broke the stylus and just put it back in the box for someone else to find!
    Can't seem to find a replacement for sale so I'm going to make one. The only part of the stylus left is it's mount to the actual guage, I can just measure and copy that. But what about the rest in particular the tip? What do I need to take into consideration for the length and shape of the tip? Was going to do it in silver steel, should I heat treat it after?
    Thanks!
     
  2. Bob Korves

    Bob Korves H-M Supporter - Premium Content H-M Supporter-Premium

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    Call or email Mark Ratkowski at M. R. tool repair and ask him if he can remove the old stylus remnant for you, or replace the pivot with a new one. For most indicators where there are still parts available, that should not be too expensive of a repair.

    815-307-3302 (cell)
    mrtool2010@hotmail.com

    I am sending Mark two DTI's with that problem today as part of a group mailing, so I guess we will find out, too...
     
  3. Tony Wells

    Tony Wells United States Vice President Staff Member Administrator

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    The length is critical only if you need it to accurately reflect the movement. If you are going to use it as most of us do, to indicate small parts, sweep tables and vises and so on where you are only trying to get a zero deflection, then it's not so critical. The longer you make it, the less movement you will read on the dial per actual part movement. IOW, if you make it 10x as long as intended, a 0.010 movement on the part will read only 0.001 on the dial. So if you need to really see a small movement accurately, then it needs to be the correct length. For the same reason, if you make it short, it acts as an amplifier. So it works both ways. I know a guy who made one deliberately short to get his 0.001 resolution to "see" 0.0001 on a 0.001 dial. I'm sure the internal structure of a truly designed tenths indicator are better than a coarser reading mechanism, but it was an improvement in sensitivity.

    What make is the indicator? I may well have parts for it. One shop I worked at I tended to be the last stop for all the wrecked indicators from all the CNC operators who crashed theirs, so accumulated a few parts. When I left there I decided I didn't need to keep the 5 gallon bucked of "dead" indicators, so tossed it. Wish I hadn't, but I did end up with some stuff in my tool boxes. I'd be happy to send you one if I have what you need. Is Bob correct in assuming the threaded portion is still in the pivot? I didn't see that stated in your post, but it's certainly not uncommon when a DTI gets mangled.

    MR is here stateside, so it may not be convenient to have him repair it, but from what I hear of his reputation, he is very good at his craft.
     
  4. Pmma-Granville

    Pmma-Granville United Kingdom Active Member Active Member

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    Thanks for the replies!
    Yea noticed he was in America, never mind!
    The make is verdict and the model appears to be "metrinch". The first and probably most important job for it is to get my lathe's spindle properly aligned. After that it will just be used for the usual work as you said.
    Sounds like that was an alright job, always good getting handed free equipment! Iv had a bench grinder, hones, tool blanks, all given to me by my employer!
    There is a piece of stylus left behind, if it is threaded it will be a pain to get out, its broken below the surface of the hole so can't grip it!
     
  5. Bob Korves

    Bob Korves H-M Supporter - Premium Content H-M Supporter-Premium

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    The broken off thread might not be so hard to get out. The stylus usually has a shoulder that bottoms on the pivot, so when that breaks off, the threads should not be bottomed in the hole. Gently give it a try, but do not damage the pivot, which may not be available as a spare part, may be difficult to make, and may require more disassembly of the DTI to remove it. The deeper we go as first time precision instrument repairmen, the more likely we are to damage the tool beyond economical repair. "First cause no harm."
     
  6. Pmma-Granville

    Pmma-Granville United Kingdom Active Member Active Member

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    It's a bit hard to see in the pic but its broken off about .5mm into the hole in the swivel. No shoulder left if it did have one! Is it nackered?

    IMG_0659.JPG
     
  7. Bob Korves

    Bob Korves H-M Supporter - Premium Content H-M Supporter-Premium

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    The shoulder went away when the part broke, if there was a shoulder. Is there a flat or recessed seat on the pivot for a shoulder? I can't see the photo well enough to tell. If there is no shoulder, then it is likely that the threads are bottomed tightly in the hole. In that case you have a real problem. If there was a shoulder, then it would be likely that the threads are relatively loose in the threads, unless there is rust, dried coolant, thread sealant, or something else holding things tight. I would try turning it with something as simple as a toothpick to see if it comes out, not something that is going to bugger it up. I would try it dry first with whatever gentle tools you might think of, and if that does not work, then I would put a small drop of penetrating oil in the hole and let it sit for a day or so before trying again after cleaning it and drying it. Take your time, think it out thoroughly before trying anything.

    Sorry I missed your location... 8^)
     
  8. seasicksteve

    seasicksteve United States Active Member Active Member

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    Sorry N/M
     
  9. Pmma-Granville

    Pmma-Granville United Kingdom Active Member Active Member

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    Thanks bob! Had a go at removing the stub but it wasn't going anywhere! Put a couple drops of oil on and will try later. No flat or recess in the pivot. Looks like I'll have to wait and see if the penetrating oil will do any good!
     
  10. Bob Korves

    Bob Korves H-M Supporter - Premium Content H-M Supporter-Premium

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    Without a flat on the pivot, you probably are looking at a difficult job, but give it a try anyway!
     

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