School Me on Surface Gauges

[mmcmdl]

Its a precision ground slot . No side to side movement . Even if there was , an indicator or scribe pressure couldn't move it . Pair of Starretts will be up for grabs .

 

[benmychree]

Side to side is simply a snug fit, no springs.

 

[ChazzC]

Pinned gages are called toolmaker's gages . Unpinned are surface gages . No difference other than the pins allow for parallel scribing or measuring .

well, maybe:



Now, Penn Tool has a compromise:


Identical SPI Item # available (as a "Surface Gage") from MSC for $30 less.


Whatever they are, these are mine:

At the top, what appears to be an old Starrett 257A (base is lightly color-case hardened and measures close to a 257 than 57 – 2-13/16" x 2-1/4"); spindle is roll-stamped Starrett, but the base has Starrett written in black:

Looks like India Ink, but solvents don't touch it.

The bottom two are Starrett 56's: both bases (2-1/8" x 1-5/8") are stamped Starrett, but not the spindles, which are only Ø0.215". The one on the right is a 56B (but I only have the 4" spindle, making it a 56A), nicely color-casehardened and includes the guide clamp (also casehardened) that was an accessory before they added the pins to the 56 for alignment with the edge of the plate, plus the original box:


And as you can see, whenever the 56B was sold, it too was a "Toolmaker's Universal Surface Gage."

 

[mmcmdl]

well, maybe:

I speak from a journeyman's language . There is a huge difference between the two . It could be true that they can run across the edge of a surface plate , but they can run across any surface when building machines . For a hobbyist not building machine tools , it wouldn't make a difference , but the the pins are handy if you need them .

 

[ChazzC]

I speak from a journeyman's language . There is a huge difference between the two . It could be true that they can run across the edge of a surface plate , but they can run across any surface when building machines . For a hobbyist not building machine tools , it wouldn't make a difference , but the the pins are handy if you need them .

Definitely agree: that’s why I snapped up the 56B with the guide.

 

[ChazzC]

Its a precision ground slot . No side to side movement . Even if there was , an indicator or scribe pressure couldn't move it . Pair of Starretts will be up for grabs .

Side to side is simply a snug fit, no springs.

It is a snug fit, but as shown on the 56A exploded diagram (but not on the 57 for some reason - there is the same screw on my 57) there is a tapered screw (#220) that engages on the large hole in the Rocker (#190) which IIRC from when I had these apart for cleaning is a mating tapered hole to push the Rocker against the side of the slot. Screw #230 locks #220 in place:

There are also little circular "springs" (#250) that keep the pins from falling out.

 

[GT-6 Racer]

I love the look of the case hardened ones.

 

[rwm]

When you say "tapered screw" what is tapered, the threads? The shoulder?

 

[ChazzC]

When you say "tapered screw" what is tapered, the threads? The shoulder?

Shoulder

 

[rwm]

I see not. Cool. I'm sure that helps stabilize the arm. I was toying with the idea of making one of these but without a surface grinder I cannot get super close tolerances. I could hand lap the bottom of the base.