Problem with a Sinclair Concentricity Gauge

[T-shooter]

I noticed I was getting inconstant readings from this gauge from time to time. Found the problem. The horizontal arm that holds the dial indicator can slightly pivot on the shaft even though the screw is tight. The screw is a pivot point. I could push back or pull forward on the dial indicator just a little and it would change the reading at least +/- .010" and stay in that position. This was so little it couldn't be felt. I checked the vertical shaft and dial indicator mounting and they are solid and allowed no movement. I put a 3/8" drill stop on the shaft that was a snug fit, then epoxied the arm to the top of the stop. Also the set screw on the stop is in the rear and doesn't allow it to pivot like it would on the side. This seems to have fixed it.

 

[Straightshooter1]

Mine does the same thing and I might try remove that movement likewise. However, mine doesn't move unless I get somewhat physical with the arm or the meter and it stays in place when I spin my cartridges. And a long as it's doesn't move when in use, then I'm not too motivated to take action, though I've thought about putting a shim in the arm.

 

[T-shooter]

Mine does the same thing and I might try remove that movement likewise. However, mine doesn't move unless I get somewhat physical with the arm or the meter and it stays in place when I spin my cartridges. And a long as it's doesn't move when in use, then I'm not too motivated to take action, though I've thought about putting a shim in the arm.

If you have the means, drill and tap a hole for a set screw in the rear right above the screw on the drill stop in the picture. That would lock it from 2 directions. I'll do that if I have any more problems with mine. Also if you have the dial indicator lower where there is more spring pressure, it may walk around easier. I put mine as high as I can get it, less than 1 revolution from where the gauge bottoms out.

 

[Straightshooter1]

If you have the means, drill and tap a hole for a set screw in the rear right above the screw on the drill stop in the picture. That would lock it from 2 directions. I'll do that if I have any more problems with mine. Also if you have the dial indicator lower where there is more spring pressure, it may walk around easier. I put mine as high as I can get it, less than 1 revolution from where the gauge bottoms out.

That's a good thought, but . . . I don't have the tools myself. So, since I had nothing better to do just now, I shimmed mine up with a couple layers of aluminum foil from my kitchen. It has firmed it up nicely with almost -0- movement when I get a little physical with it. Guess I'll see how long this little mod will work.

See here:

 

[jackson1]

Thanks guys another thing to check. Glad its cold dark winter and I need something occupy my time. Never understood the need for a for a 0 to1" dial indicator sold with these gauge, when a test indicator would far better suited to the task. Oh 21st Century got it right. As a retired tool and die maker, I modified my Sinclair tool.

 

[T-shooter]

Shars makes an affordable .0005" and .0001" dial indicator. I use the .0005" which is much easier to read than the .001" that came with it.

 

[T-shooter]

Thanks guys another thing to check. Glad its cold dark winter and I need something occupy my time. Never understood the need for a for a 0 to1" dial indicator sold with these gauge, when a test indicator would far better suited to the task. Oh 21st Century got it right. As a retired tool and die maker, I modified my Sinclair tool.

How did you modify it? Have any pictures?

 

[LC Tikka]

Don't have one of these, screw clamping a round shaft in a round hole is not good practice, only two points of contact. Plenty of ways to mod it or better still make it properly first up.
LC

 

[Shooter13]

If you purchased it from Brownells they will take it back no questions ask.

 

[Lone Hunter]

That's a good thought, but . . . I don't have the tools myself. So, since I had nothing better to do just now, I shimmed mine up with a couple layers of aluminum foil from my kitchen. It has firmed it up nicely with almost -0- movement when I get a little physical with it. Guess I'll see how long this little mod will work.

See here:

View attachment 1151899

Wonder if you could tap it at the 3 and 6 o'clock position and use some set screws or would that be too much? Haven't used mine in a while and would think 3 set screws might prevent movement .

 

[Straightshooter1]

Wonder if you could tap it at the 3 and 6 o'clock position and use some set screws or would that be too much? Haven't used mine in a while and would think 3 set screws might prevent movement .

Three would certainly work, but two at 90° from each other would be enough.

It's not like there any heavy pressure on the arm and there's a point of diminishing return for the amount of runout error when looking at less than .002. huh???

 

[Gappmast]

Shars makes an affordable .0005" and .0001" dial indicator. I use the .0005" which is much easier to read than the .001" that came with it.

I agree a .001" indicator doesn't show much and a .0001" will drive you nuts. The .0005" is a good compromise

 

[T-shooter]

The modification I made fixed it for now. With both screws locked, it moves about .0005" each way when rocked back and forth (.0005" dial indicator) and instantly returns to the center when there is no force on it.

 

[snakepit]

Mine does the same thing and I might try remove that movement likewise. However, mine doesn't move unless I get somewhat physical with the arm or the meter and it stays in place when I spin my cartridges.

Mine also does the same thing and like you it doesn't move unless I use a lot of abnormal force that is not required in it's normal operation and then it only moves .001. I don't plan on doing anything to mine because like I said I can't ever see myself using that much force in making the measurements.