Tell me about measuring tools (2 reasons)

[ChevyEFI]

I broke the thumbroller part of my 6" slide caliper. It's an inches dial-style. I got my money out of it; the jaws are worn a bit and it's time to upgrade. So there's that.

But I wouldn't mind knowing about what makes a brake mic. (to measure drum i.d. "special." I haven't owned or pondered a mic.; just calipers. Can you dumb down a description of the contact point differences vs. the jaws on a regular caliper for me? Is it that they protrude at a point externally versus a flat / sharp jaw edge?

I'm probably well-served just getting a longer caliper for the drums (don't need ultra precision) and replacing the 6" as well. I haven't looked at the future replacement 6" yet. Don't care to go digital, but it's probably the right thing to do.

Thanks.

 

[iajonesy]

a micrometer for brake calipers is usually very deep to be able to measure from the hub area out to the edge of the caliper. You can use a standard mic to measure your calipers in most cases because most wear is on the outer half of the calipers. The advantage to a brake mic is that it can be used to measure anything a normal mic can.

Mike (no pun intended)

 

[iajonesy]

Whoops. I didn't see that you were talking about drum brakes.

Mike

 

[ChevyEFI]

That's good added information. No whoops to it.

 

[CWP1616L]

They got separate calipers for measuring drums and separate calipers for measuring rotors. The drum calipers are made for measuring an inside dimension and the rotor calipers are made for measuring an outside dimension.

Inside Calipers
Drum<------>Drum

Outside Calipers
----->Rotor<-----

 

[helterskelter]

I don't know much about measuring rotors or drums (never done it). But I'd stick with dials if you're going to use them for ID measurements (where you're trying to find the largest ID). With dials you can watch the dial swing to find the high spot, that's the biggest advantage of dials in my opinion. They're also always ready when you need them. I have both dials and digital and use them differently, dials for finding highs and lows, digital when I just need a number.

 

[ChevyEFI]

I borrowed a digital today from a next-door shop. Not unlike the below. And I think I screwed up by zeroing and not taking into account the starting dimension of the jaws. Is it possible some of them begin at 60mm?

 

[helterskelter]

I borrowed a digital today from a next-door shop. Not unlike the below. And I think I screwed up by zeroing and not taking into account the starting dimension of the jaws. Is it possible some of them begin at 60mm?

Not sure I understand your question. Usually the stand-offs are a round dimension (IE 60mm). But they should be zero'd while they are touching. Sometimes you'll see stand-offs in a vernier set and those need to be taken into account but a digital should be set to zero with the points closed.

 

[ChevyEFI]

(I sent you a PM BTW)

I zeroed it while it was fully slid together. The jaws had pointed tips installed to measure an i.d. Similar to the above picture I posted, but with the tips pointing away from the outer faces of the jaws vs. the inner.

The reason I believe I did it incorrectly is the two drums were in the 181mm range. And the cast-in max dimension is 243.** mm.

 

[helterskelter]

If the tips were points away then you need to take into account the thickness of the standoffs. Measure them with an OD mic and that is your zero. Or you can zero the calipers without the standoffs, then install the standoffs and measure again. This is your offset.

I responded to your PM. I'll send you another on Monday after lunch.

 

[TwoInch]

helter, you have any reject dial calipers you might wanna sell for a reasonable price? i wouldnt mind having one for non-critical measures like brakes and such. i have a couple mics and a vernier, but no dials.

also been looking for an indicator. if you have any laying around.