DTI assembly diagram/tips/pics?

[TroyO]

So, I dropped my DTI... it was a SPI .0001 0-15-0 that I got at a local auction with a pile of stuff for like $30, so no great loss. (It was a great auction win for a newb, 2 DTI's, 4 decent mics up to 6", Mic stand $30 plus a couple bucks in fees.)

Anyway... it was jamming and acting funky after the drop, would only read .0005 in one drection and was "herky jerky", so I figured I'd take it apart and take a look.... and now I can't get it back together! LOL. Anyone pulled one of these apart by chance? It seems to me you'd have to center the gear train and the dial needle, hold them in place some how and get everything meshed at the center point, or pretty close thereabouts?

I figured pulling it apart was a "hail mary" anyway... figured I couldn't make it worse than unusable and it was fun seeing how it works. But, since I can't seem to find anything binding or bent I figure if I can get it back together it may just work fine.

Any tips or suggestions? Parts diagrams or anything that may help me figure out the correct proceedure for getting it back in there?

Next question.... I usually use the .0005 DTI. As a newb machinist how much use is there for a.0001 one? Worth buying another to replace it? (At retail?)

I'll shoot some pics tonight.... maybe others will be curious to see what goes on in there?

 

[cidrontmg]

Note: I didn´t write this, I copied it from
http://longislandindicator.com/p37.html (you might consult them, although they tend to put things quite bluntly...)
_________________
SPI (China) manufactured for SPI. These are generally the same Chinese indicators you can buy under any number of other "brand" names. The cheap price gives them away. SPI stands for Swiss Precision Instruments. Don't let this fool you. These are not Swiss and their precision is short lived. (SPI used to offer genuine Swiss indicators with the SPI name. They were made by Compac and you can still get them. See Compac above.)

Repairs: not possible
Sales: any SPI distributor including Long Island Indicator (but we won't sell you any of these on purpose)
Parts: not available. Never have been, never will be.
Information: you read it here
____________________
ehrm... sorry...

"As a newb machinist how much use is there for a.0001 one?"
Depends on what you (are planning to) do, of course. For me, they´re absolutely unnecessary. With my machinery and skills, I can never keep the needle even gently wobbling, it just goes in wild >90º arcs. Even when a .001 clock will show next to nothing. But of course there are machines and needs that demand far more precision than I´m capable of. For putting together small steam and IC engines, you never need .0001" accuracy.

 

[Tin Falcon]

If you hold your nose right and say a couple of prayers you may be able to get it back together . Some of the parts could be bent.

Tenth indicators are nice for precision work like a sterling piston or setting up a pre machined shaft for a second operation. When I worked in the precision grinding shop operating a grinder used them ALL the time every part was indicated in to a couple of tenths.
In the home shop have a couple that sit in the drawer of the Kennedy most of the time.
With a decent chuck it does not take a whole lot longer to indicate to tenths than thousands with a bit of practice. But if you can get your part running in between two lines on your .001 or .0005 indicators that should be plenty good for hobby work.
I was always taught that if you can practice more precision and to a higher quality than needed. then when you need high precision you have the practice. This was in an Air Force shop and we usually had the extra time to be precise.
In a for hire job shop time is money and precision is expensive and not always a good value.
In your home shop you have to decide the priorities of how much precision , time money bling etc you put in each part.
Tin

 

[90LX_Notch]

If you get some pics up I may be able to help you.

Bob

 

[TroyO]

I figure pics would be cool anyway, if only for the same curiosity's sake that led me to take it apart in the first place, LOL.

The dial says "Japan" does that make it better or worse than the "China" not-so-Swiss Precision Insturuments one? ;D

The big question is my guess is you can't just throw it in there, it has to be in some set position before goes together?

 

[Deanofid]

Hi Troy;

The "Japan" on it surly makes it better than Chinese stuff. I see it says "jeweled" on the dial face, and
it actually has jewels for the pivots! I have a Chinese one that says "jeweled" and there is not a single
one in it. They simply lie.

You want to have a look at the pivots, (the little shafts) to see if any are obviously bent. Without a
proper way to check them, like a watchmakers turn, you can still make a good judgment about them
by putting two razor blades into a piece of balsa. Push them in using a flat plate under your mill spindle
to get them into the wood nice and level, and spaced apart just under the length of the pivots. Put each
pivot on the two blade edges and use a toothpick to roll it. Watching with a loupe or magnifying glass,
you will be able to see if they're bent. The slightest bend will mean this piece of equipment is done.

The other thing to scrutinize is the gear teeth. Everyone must be as straight as it's neighbor.
If one is bent, that will make it stop at a certain point. You may be able to straighten them, though
it's pretty hard without equipment made for the task.

I wouldn't worry about what Long Island says about this brand. They are honest in their opinion, but
usually have little good to say about something they don't work on anyway.

For a home shop, when you go to replace this DTI, or just to buy another one, think about what we
make. Almost nothing needs measurements in increments less than .0005". Most machines in a
home shop will not have the inherent accuracy to make sense of it. I mean, when you dial in your four
jaw chuck to zero on a tenth's scale, and your spindle runs out at .0004", you may be chasing your tail.

That's not to say you shouldn't get one. Like Tin says, learning to use it will come in handy IF you
actually DO need it, but don't let the numbers below .0005", or usually those under .001", drive you
nuts. You can end up using shop time doing something that makes no difference to your project.
Also, you can split the lines on a .0005" instrument pretty easily. As long as you don't get one that
has too large of a measuring range, getting to within .0003" on a half thou dial is pretty easy.

I don't know where all these pieces need to be in relation to each other without having seen it come
apart. If the parts aren't damaged, I'll bet you will find the matching-up points with a little trial and
error.

Thanks for the pics!

Dean

 

[90LX_Notch]

Troy,

The state it's in now is a little involved to try and walk you through it over the internet without having one apart here to use for illustratration purposes.

If you are willing to pay shipping both ways, I'll put it back together for you.

Bob

 

[TroyO]

Notch, thanks for the offer, but as it happens I think I got it! :big: :big:

It's reading in both directions nice and smooth, and it always snaps back to "0". (Well, almost always.. sometimes it rides the side of the line.) Not to say it couldn't be improved... what kind of lube will do the trick.. anything I may be able to get at an auto supply store? It's much better now than it ever was since I got it at that auction.

The last little trick is getting the "limit" screws set.... they are touchy little buggers! Plus I am using a jewelers screwdriver even though they are allen heads... but my tiniest allen is still way too big, LOL.

What should the limit be... maybe one turn each way? It reads 0-5-0 so it's only good for .005 anyway, but for relative measurement (Like for centering stuff) would it hurt to give it a full spin either way for .010 reading?

 

[TroyO]

'Doh! I just realized the folly of how I was trying to set it... LOL, I forgot the dial turns so you need more than just the read limit swing on the dial.

So, I'm guessing I just want to set it to make sure that the set screws are what is stopping it and NOT the internal mechanism.

Thanks all for the insight! It's been an adventure, and I certainly learned something! Which is kind of the whole point... ohh, and I now have an indicator with limited usefullness.... but will be indespensible on the rare occasions when I need it! LOL. :big:

 

[Twmaster]

Troy, if all else fails you can pick up a Starrett 'Last Word' on FeeBay for $20 or less shipped if you are patient. (Long Island Indicator does not like the Starrett either... I like mine!

Kinda fun though to try and put the egg back together though.

 

[mklotz]

I wouldn't attempt to lubricate it. It's highly unlikely you have anything to hand that won't eventually turn to gum in there.

If, after using it for a while, you decide it really, really needs lubrication consider doing what my father used to do to lubricate his treasured pocket watch. He would open the back and put the tiniest drop of kerosene on the inside of the watch back. The heat from his body would gradually evaporate the kero and allow a miniscule film of oily vapor to deposit on the works. I still have his watch and it still runs.

 

[TroyO]

It didn't have any apparent lubrication when I took it apart, so it makes sense. Plus, the parts that spin have the jeweled bearings, which I seem to recall shouldn't be lubricated?

That would mean the only thing that would benifit from lube would be the gear faces... and now that's working pretty smoothly anyway.

I'll leave it alone and just use it, LOL.

 

[mklotz]

I'll leave it alone and just use it, LOL.

Good choice. I've never had much success fixing things that weren't broken.

 

[TroyO]

Hahah, true.

I do wish I had found something I could point to and say "Ahhaaaaa! THAT is why it wasn't working before."

I do have a theory as to what happened, though.....

If you look at Pic #1, that long arm with the geared section at the end is my first suspect... it's length and relative weight of the geared section would make it the most likely part to be affected by a high G load (Like a drop) and I suspect it flexed out of line with the small hub gear on the crowned gear that drives the needle. (You can't really see on the pic but that gear ends just about where the side plate obscures it.) That allowed it to jam adjacent to the small hub instead of in line with it. Luckily it seems that it flexed that way instead of bending permenantly.

When I took it apart, before I could see what was happening on the inside I bet the small spring on the arm was able to slip it past the hub gear once it no longer had to fight the dial tension as well. Once the arm travelled past the hub gear it was no longer being held in flex and was able to return to being in line with the hub gear, and the arm and hub gear were able to then mesh correctly.

Anyway... that's my story and I'm sticking to it!

 

[Lew Hartswick]

If, after using it for a while, you decide it really, really needs lubrication consider doing what my father used to do to lubricate his treasured pocket watch. He would open the back and put the tiniest drop of kerosene on the inside of the watch back. The heat from his body would gradually evaporate the kero and allow a miniscule film of oily vapor to deposit on the works. I still have his watch and it still runs.

My father said the same thing about the old weight driven pendulum clocks. He said
a small cap form a bottle with a bit of kerosene set in the bottom was all the lub.
they needed. The vapors did the trick.
...lew...