Thread: Wickman OPG Optical Grinder.

Here you go BT.
I first tried with just the Navara rear wheel bearing shell for the dia and a 1" ball bearing for the punch. It was to easy to put a ding in the crystal, though its amazing just how much of the ding goes away over a couple of days. Next I used my ball turner to make a 1"dia face with a 2"radius curve on it. Why is the rest so large? so it can line the dia up, I havent made anything as yet to hold the dia in place. Yet another half finished project lol

Stuart

Stu,

You've glazed over the crystal's removal. With your installation tools are you installing new crystals or simply replacing the old?

Long Island sell replacement crystals but with Richard "Eskimo" 's quoted 25ish bucks for postage for something the size of half a toothpick, maybe you'd look elsewhere.

233 : Crystal Insertion for indicators and calipers

BT

Hi BT,
Not much to tell. Put the crystal in, bounce on bottom of stroke while you try to turn the bezel with one hand and lower the stroke with the other. Its very easy with my set up to go to far but after a couple of practice runs on my worst Federal the Mercer's were no trouble.

Just replacing the old after a polish. I'm tempted to have a lash at making some crystals. Cant be that hard surely I have a plastic place down the road with a min order of $60, that should get me enough 1ish mm polycarbonate(does anyone know if it is ploy?) to last me awhile.

Better yet from the comfort of my own home.
1220 X 2440 X 1mm Polycarbonate Clear Sheet Bayer Special Postage Limited Time | eBay
800 to many?

Polyguard UV2 Polycarbonate A3 Size 420 X 297 X 1mm Clear UV Resist Pack OF ONE | eBay

Havent actually measured it as yet 1mm is a guess

Stuart

Bob & Stuart
I have a Starrett 711 Dial indicator .0005" purchased off E Bay USA about 12 mths ago.
All works well however the indicator pointer catches on the crystal (plastic domed piece).
So I have been using the indicator without the plastic cover (crystal)
Would like to fit a new one. Have either of you done this successfully ?
If its a big deal, I can continue to use it carefully without the crystal.
regards
Bruce

It helps having a cousin in Switzerland hos a watchmaker and does it for you

Hi Bruce,

We thanks to BT I have a last order to practice on.
Are you sure the bezel hasnt been pushed on to far?
Maybe its missing the ring?(if its an old crystal)
I havent replace any crystals with "new" as yet.

Stuart

How about a thread as a repository of instrument repair knowledge?

Originally Posted by Bryan

How about a thread as a repository of instrument repair knowledge?

That might be good. I have often shied away from cheap indicators because of broken crystals, even if they seem to work ok.

I take it the curve of the crystal is only there because the disk of poly is too big for where it is going?

Ew

Originally Posted by Ueee

That might be good. I have often shied away from cheap indicators because of broken crystals, even if they seem to work ok.

I take it the curve of the crystal is only there because the disk of poly is too big for where it is going?

Ew

Yes Ew, though some manufacturers do use preformed crystals.

One issue I can see with home mode crystals is that they require a bevel on their edge. Maybe a disc is placed between a pair of rubber faced bar ends, which are head and tailstock mounted and the appropriate bevel turned. I have a copy of Mike Yamamoto's "Repair of Mechanical Dial Indicators and Calipers" *. It contains a wealth of useful information BUT is copyrighted. I'm not really trying to create work for myself but I could reword some of the advice he provides.

* a bit more about the late Mike's book here - Dial Indicator Repair Book

BT

Originally Posted by Stustoys

Hi Bruce,

We thanks to BT I have a last order to practice on.
Are you sure the bezel hasnt been pushed on to far?
Maybe its missing the ring?(if its an old crystal)
I havent replace any crystals with "new" as yet.

Stuart

Thanks, your photo of the Starrett 711 indicator looks identical to mine.The 711 purchased on E Bay was nice except for the domed Crystal being a bit loose.
I have just spent the last hour fiddling & checking it out under a magnifier.
The problem in essence is the domed plastic (Crystal) has reduced slightly in diameter over the years & is now not a click or press fit into the bezel.
I tried heating the plastic (Crystal) in hot water & then holding it on a flat plate under finger pressure to try & expand it slightly, before refitting. This may have helped, but its still not a tight fit.
I might warm it a bit more, & try again, being thermoplastic, it should not take much to enlarge it a little.
Probably easier to get a new Crystal from the USA.
Thanks again to both you & Bob for the assistance on this problem.
regards
Bruce

Hi Bryan,

Not a lot of knowledge on my end yet lol working on it.

Hi BT,

I have some ideas in mind for the bevel. Poly comes with a pretty tough paper/plastic coating.(or at least it used to lol)

Had a quick look for a copy, doesnt seem to be one about and even if there were sounds like it goes upwards of $100.

Hi Bruce,
Is the metal ring there? as I'm looking at it even if the crystal is loose, if the ring is there you should be right..... but then I wouldnt know lol. My crystal wont stay in by itself, the ring holds it in.

I think the other indicator in the grinder may have to come to pieces. As I cant do as good a cleaning job on it as I could on the last one as the clearance it just a little different. So next job is a needle puller. One thing that has me umming about replacing the cystals is that one of the needles is a little rusty(beyound my skill to fix just yet) and the yellow cystal hides it pretty well.


Stuart

Stuart
Yes, the ring is there it has a split (like a piston ring) so it looks like it springs out, to the internal dia of the bezel.
The ring is located in the bezel.
I guessed the plastic crystal fits in the groove in the bezel above the ring ?
Maybe I have been wrong. Does it fit below the ring?
If so how do I get the bezel ring assembly off to fit the crystal?
Photo attached of the problem.
regards
Bruce

Originally Posted by Abratool

If so how do I get the bezel ring assembly off to fit the crystal?

Hi Bruce,
With a suitable "lever"*. For a long time I thought the crystal on these must go in from the front as I thought the moveing parts of the bezel were one piece, you can see in the picture the knurl isnt parrallel to the base, thats because the knurl and above are one piece press fitted onto the base. Of course this is all based on a sample of one, yours maybe different.

Hi Bob,
Does your book say much about how much tension to put on the hairspring?
I got it apart further without need of a puller. Working well now.

Stuart

*butter fnike worked well for me. There must be something better out there

Hi Bruce,
Just found a problem with heating your crystal. Dont get it to hot. Assuming its polycarbonate, assuming it wasnt preformed and assuming all polycarbonates react pretty much the same way. Seems it can shrink up to 6% on heating above 145C(granted not a problem with hot water)

Stuart