School Me on Surface Gauges

[rwm]

I don't know much about these tools. I see Starrett, Brown & Sharp and the other usual suspects. Some of these have pins at the corners that pass vertically through the base. Some have 4, some have 2, some have none? Some of these on eBay are missing pins with holes! What is the function of these pins? Are they removable and why?
Which of these brands do you like and what do you typically use it for?



I'm not sure I need one but I want to know anyway!

 

[DavidR8]

I've understood those pins are used to run along the edge of the surface plate.
I am totally open to being corrected!

 

[ChazzC]

I've understood those pins are used to run along the edge of the surface plate.
I am totally open to being corrected!

Nope, you are correct:

 

[rwm]

So the pins move up and down? They are not pressed in place?

EDIT: Yes I see the pins are movable. Towards the end of the video he uses these.

 

[GT-6 Racer]

I have amassed a small collection of surface gages. From a tiny 1x2” base B&S to a very large Starrett and a selection of sizes between, including a couple of shop made ones. They are quite handy on a surface plate. I use them for scribing and transfer measurements with a DTI. You can use them like a repeat-o-meter to do a surface plate check. Very handy with a DTI for checking flatness when scraping or grinding. Lots of uses for a simple tool.

 

[Ulma Doctor]

I have a 10 of them, different sizes and mast heights. They are very handy for layout and indicating

 

[ChazzC]

So the pins move up and down? They are not pressed in place?

EDIT: Yes I see the pins are movable. Towards the end of the video he uses these.

Sorry: if you play the video within my post it starts at the applicable part; if you click to watch on YT it starts at the beginning.

 

[mmcmdl]

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

 

[mmcmdl]

I'm not sure I need one but I want to know anyway!

You know you need 1 .............................or 3 !

 

[rwm]

I have a question about how these are constructed. They typically have a pivot arm that sits in a slot in the base. A screw on the far end allows for fine adjustment of the angle of the mast. I was thinking that any slop in this pivot arm would be a big problem. How is the arm fit into the slot? What prevents it from moving or tilting sideways slightly? Its it just a tight ground fit, or is there a spring mechanism or something keeping it aligned? I know there is a spring in the front that pushes against the adjustment screw but what about side to side?