Dial caliper maintenance

[chasw]

I bought a nice Mitutoyo 6" dial caliper off eBay for a bargain price. Its a used Made-in-Japan model 505-637-50. From looks of the plastic case, I'm guessing its maybe 1980s vintage. Everything seems to work fine, definitely a step up in precision from my trusty yellow plastic Lyman job. The only drawback with the Mitutoyo is, at zero the needle points to the 3 o'clock position.

There is a little slot under the dial near the 12 o'clock position. I understand the calipers originally came with a simple little tool the user inserted into that slot thereby allowing the jaws to close a little while skipping backwards a few notches.

Some questions for my fellow reloaders:

• Do I need the special tool, or will a paper clip do the job? Where would I find such a tool? What is the technique?
• What is the normal cleaning method for stainless steel dial calipers? Is it wise to try and disassemble the slide from the frame?
• Should I apply any lube? What kind?

Thanks - CW

[jcwit]

Don't use a paper clip. I wish I knew how to post a pic. but will try to explain. They came with a small piece of brass about .005 thick, approx 1 inch long with a round shape on one end to serve as a handle. It narrowed down right after the round shape to 1/16, the width of the rack gear. Overall shape of this tool, think of the letter P with a longer leg.

In use the leg of the tool goes into the rack and lifts the gear that rides on the rack letting the needle skip to the right spot.

This is probably as clear as mud, but dern I tried.

Second thought is a old fashioned hair pin might work also if you grind one thinner.

Hope this helps.

BTW I don't think it would be a good idea to remove the slide from the frame.

[Calamity Jake]

What jc said for the adjusting tool, open the calipes about half way then insert the tool from the front of the dial and on top of the rack gear now close the calipers a little until you feel the tool contact the dial gear, close a little more to lift the gear up a little, now remove the tool and check for zero, it's a trial and error thing you just have to keep at it until you get it right, be gental, do not lube, do not disassemble, use an old tooth brush to clean the rack gear, cracks and crevises then low pressure compressed air to blow loose stuff off then a wipe down with alcohol.
Use a medium to hard flat stone to remove any burrs on the ID points and the faces of
the measuring jaws.
On the top behind the dial are two small screws one on each end of the gibb, with a small screw driver turn in until just snug then back off 1/8 turn, this should remove slack in the gibb/way assembly, if there stiff to open then back off the screws a little more.
Now you need to check them for accuarcy, you can do this with known diameter ball bearings
for the OD jaws and one of your lyman/rcbs boolit sizing dies for the ID jaws.
Keep them clean and be gental with them they'll last you your life time and then some.

[220swiftfn]

Ok, here goes..... the adjuster is .040 thick, and .060 wide. A hair pin should work fine. Starting with the jaws closed, open them enough to get the dial at 12 o'clock. Insert the adjuster, push down gently, and close the jaws. Done. The adjuster works in quarter rotation, so it'll fix the 3,6,9 orientation. After that, the thumbscrew at the bottom of the dial is friction for the bezel (loosen it a little, and you can rotate the bezel to set zero.)

Dan

[220swiftfn]

Sorry, forgot...... no lube. Wipe off the top and bottom of the slide with a dry patch. If it still feels funky after that, I'll walk you thru disassembly.

Dan

[jcwit]

Calamity Jake said to use Low pressure air, for sure right. Years ago with one of my first dials I used high pressure to blow out the rack from dirt/dust/chips ect. Blew the plastic crystal right off. Back then our fellow that did the sharpening of tooling would P/U the precision stuff and had someone to repair them. Doubt they do that today.

[casterofboolits]

Gee! You guys got the new stuff. My Mitutoyo 4" was bought in 1969 and still works like a charm. The dial is held with a clamp and screw. Loosen the screw and turn the dial to adjust 0.0. Still have a .2500 carbide pin gage to calibrate it.

[jcwit]

Gee! You guys got the new stuff. My Mitutoyo 4" was bought in 1969 and still works like a charm. The dial is held with a clamp and screw. Loosen the screw and turn the dial to adjust 0.0. Still have a .2500 carbide pin gage to calibrate it.

Right, mine have the same screw with clamp. Alot of folks like the needle to point straight up tho.

[gnoahhh]

My job is building scientific apparatus for use in the labs here at the college. (A one man operation- essentially they pay me to tinker.) Metal working shop on one side and woodworking on the other, divided by a window wall and doorway. Try as I might, wood dust gets into all the nooks and crannies in the metal shop, including the mics, verniers, dial calipers, dial indicators, etc. I routinely strip them down for cleaning- it's no big deal. I lube with a light instrument oil from Zeiss Optics, very, very sparingly (wipe on, wipe off). Double check accuracy with a set of Jo blocks when I'm done. Like everything else, dis- and re- assembly of precision tools is a matter of patience, steady hands, good light, and a clean sheet of white paper under your work. My "rough-and-ready" dial calipers is a 40 year old 6" made by Helios. I must have had them apart a hundred times now and they're still as accurate as when new.

A thought re:compressed air. I like to turn the pressure way low before blowing out a precision instrument. Too much chance of sending small screws and such from off the bench into never-never land. Also, put a dryer someplace in line before the nozzle. Water in the compressed air, forced into the innards of the instruments, will do them no good.

[pcmacd]

Don't use a paper clip. I wish I knew how to post a pic. but will try to explain. They came with a small piece of brass about .005 thick, approx 1 inch long with a round shape on one end to serve as a handle. It narrowed down right after the round shape to 1/16, the width of the rack gear. Overall shape of this tool, think of the letter P with a longer leg.

In use the leg of the tool goes into the rack and lifts the gear that rides on the rack letting the needle skip to the right spot.

This is probably as clear as mud, but dern I tried.

Second thought is a old fashioned hair pin might work also if you grind one thinner.

Hope this helps.

BTW I don't think it would be a good idea to remove the slide from the frame.

I got some walnut media inside the gears and tracks on my similar caliper. I HAD to take it apart, and it was a Serious PITA to get it back together. It is burping again coming off zero (it's been 20 years since the walnut media incident) and I am afraid to use it until I figure out what's wrong.) I have not read this thread yet so I am not asking for help!

Also, somewhere along the line my crystal cracked, and the little plastic job that holds the dial steady broke. This was at least 25 years ago; I purchsed TWO crystals and THREE of the dial lock goodies. Back then you could order diretly from Mitutoyo. Nowadays? I spent SIX FREAKING HOURS LAST WEEK finding a place to buy parts. PM me if you want more info.

I've started collecting measuring tools, so am learning where to find parts. Starrett you can get direct. They have some interesting 3D tools to show you their stuff and parts, but it only works on Internet Explorer. It is still awesome.

PM me for more data if you need it. I don't hang here much so be patient, dudes.

[smokeywolf]

pcmacd, jcwit is no longer with us. He passed on a few weeks ago.

One of the places you might try for measuring tool parts is, Long Island Indicator Service (longislandindicator.com).