Mitutoyo 505-626 caliper dial divided into two 0-100 arcs within one 360° sweep

[jbeech]

Picked up a set of used Mitutoyo 505-626 calipers calipers off eBay. Yes, I know, seems stupid to pony up $40 when decent new calipers are about $100 but I couldn't help myself as they're a curious item. So the points are in fine nick, the motion is smooth (indicating the rack is clean), and they return to 0 every time, and when I measure a gauge pin, I get the same results as with other calipers, so they're accurate enough. So bottom line? I'm not unhappy with the purchase.

So why did I buy them? It's because as the title explains, the dial's sweep is split into two 180° arcs with 0-100 from 12 o'clock to 6 o'clock, and 0-100 again from 6 o-clock back to 12 o'clock. These are Mitutoyo 505-626 dial caliper of late 70s, early 80s vintage. They're pretty much like new so opening the box was like stepping out of a time machine to when someone first opened the box on their new purchase maybe 40-50 years ago. Hardly vintage for this crowd, but anyway . . .

• One pal's theory is this is an el cheapo version (0.1" per sweep is more pricey to make than 0.2" per sweep)
• Another savvy friend's theory is it's for inspection work (but they're not +/- off center - two consecutive sweeps
• A third theory is it merely makes life easier when reading at odd angles

Me? I have no clue, which is why I'm asking the brain trust of antique machinery.

 

[AJ H]

Mitutoyo still makes them like this, and they cost less than the .1 per rev version.

 

[RC Mech]

My first pair of calipers were the same model. The graduations on the dial were perpendicular to the beam until they got bumped and had to have the dial at an odd angle like yours to zero out.

Then I tried to take them apart to clean them and that was the end of those cals.

 

[Jim Christie]

My father had a Mitutoyo dial caliper and a couple of others of unknown brands in the early 1970s .
I thought I remembered one of them that had a small flat spring tool that you could slide a long the rack to reset the needle back to the 12:00 position if it got displaced when the gear would skip over a small piece of grit or cutting on the rack like a grain of cast iron or cast bronze.
I can't find the caliper at the moment but it was well worn out .
The adjustment tool came with the caliper in a small plastic pouch and there was an instruction sheet that came with the caliper showing its use.
I tried a search and don't see the one I was thinking of but this video shows something that accomplishes the same goal but may not apply to your caliper .
Resetting zero on a Mitutoyo dial caliper using the "special " tool. - YouTube
Maybe some of the other links in the search I tried will turn up something or some other member will know more.
dial caliper adjustment tool - Google Search
I did see a caliper for sale in one of the links that came in a small pouch with a tool like the one shown in the video .
I forgot to save the link and can't seem to see it again.
I also looked at this link that may be useful to someone .
Caliper Repair Guide
Jim
P.S. this is more like the one I remember
https://www.hobby-machinist.com/data/attachments/293/293299-ebde2180a3b58bb6359c1bd53759e751.jpg
From this thread
Anyone have a Mitutoyo dial caliper adjuster shim or dimensions of same? | The Hobby-Machinist

 

[Larry Dickman]

I think those might have been mine.

Hard enough to read when I was 18

 

[L Vanice]

I think my first dial caliper was a Mitutoyo 4" capacity bought around 1970 from a jewelry supply company. I think it was a very new product at the time. I think it had the .2"/rev. dial and did not have the "Quadri" or whatever their term was for the four different measuring features that included the step measurement at the left end.

I recall that a few years later I upgraded to a new model Mitutoyo 6" with .1"/rev. dial and Quadri and sold the 4" to someone.

I also had the little tools that could reset the zero position that came with the calipers. I probably still have several dial calipers stuck in drawers, unused since going digital.

Larry

 

[TomBoctou]

My first pair of calipers were the same model. The graduations on the dial were perpendicular to the beam until they got bumped and had to have the dial at an odd angle like yours to zero out.

Can the hand be pulled off and reinstalled like a watch hand to reset zero to where you want it?

 

[neanderthal mach]

The needle or hand doesn't need to be removed or touched at all with any model of Mitutoyo dial calipers I know of. Jim Cristie's very first video link shows how to re-zero the needle in any position you'd like including straight up there factory adjusted to. As the video shows, open the calipers a bit with the dial face 0 point straight up, the built in slot on the back side of the tool guides the simple re-zeroing tool into position, you then add a bit of pressure to disengage the spring loaded rack gear from the rack and close the calipers. Sometimes you'll still be a tooth off so it might take a couple of try's at it before you get it exact. The documentation the Mit. dial calipers come with also detail how to do this, but many don't read it or it gets thrown away. Not mentioned in that video is if the needle has moved the zero point it's a sure indicator there's dirt or contamination in that rack. Detail cleaning it should be the first step before doing any adjustments.

 

[Walter A]

I have to admit my first thought was why is this in the Antique forum. Then I remembered how many years ago I used similar.
Mine were always a tooth or two off. It didn't matter. Calipers were for getting it close anyway. Anyway, off center or not,, they were better than those old Starrett vernier with 25 division scale. Lord I hated to use those verniers.

 

[rivett608]

My first pair were that way in the 70s, I think they were all made that way back then. Now as I get older and don't see as well I hate those.

 

[JonnyZ]

Hi all. I just received an old pair of 505-626 calipers from Ebay. They looked pretty beat but I got them for next to nothing so I figured I'd give it a go. I need to get a new crystal for it as the one that was on it was old and broken. Any crystals I find for 505-626 are bigger than my caliper dial face. I believe they are 36.2mm? Mine are around 33mm inside edge of the bezel. I am having a HECK of a time finding anything that will work! Anyone have any ideas on where to look for one? I guess I have to have a plastic one so it will be concave? I can't use a glass one? I appreciate any advice anyone can offer.

Jon

 

[L Vanice]

Hi all. I just received an old pair of 505-626 calipers from Ebay. They looked pretty beat but I got them for next to nothing so I figured I'd give it a go. I need to get a new crystal for it as the one that was on it was old and broken. Any crystals I find for 505-626 are bigger than my caliper dial face. I believe they are 36.2mm? Mine are around 33mm inside edge of the bezel. I am having a HECK of a time finding anything that will work! Anyone have any ideas on where to look for one? I guess I have to have a plastic one so it will be concave? I can't use a glass one? I appreciate any advice anyone can offer.

Jon

These people are local to me and do repair work on Mitutoyo tools. >> Services

If you are near a large city, look for a local instrument repair service.

Otherwise, a jewelry shop with a watch repair facility that has been in business for decades may be able to install a plastic crystal meant for a pocket watch. The thing is, removing the bezel from a caliper is not at all done like removing the bezel from a pocket watch, so a watch guy might not want to try to figure it out.

Larry