How Do You Measure Groove Depth When Depth>width

You can always grind a flat on anything round to make it fit the groove.
 
If I am going to measure a lot of grooves I make a simple set of go/no go gages. Just like snap gages.

"Billy G"
 
Tom, you can turn a diameter test piece with the groove tool and note on the cross dial the size needed using a regular mike. Then put the piston in your chuck and make your grooves turning the dial down to that referenced mark you just made on the cross feed. You can check the width with pins…Good Luck, Dave.
 
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tomw said:
Dear All,

I am cutting some piston grooves on a steam engine model. The are to be 0.054 +0 -.005 in depth, and 0.050 +/-.002 in width.

So, I cannot use my usual trick of measuring across something round of known size that sits in the groove (the groove is deeper than it is wide).

How would you go about confirming the depth of these grooves?

Thanks,

Tom
Click to expand...

Lap a 1/16" T-type parting tool to .050. Then locate the first groove and when the tool starts to cut , set the dial to zero.
Cut .050 deep. If you will use a viton seal ,have it on hand to check the fit.
mike
 
Why not just use the height gauge you already have? Find the high spot on the OD cylinder and set zero then put the tip in the groove and measure down to the high spot of the groove diameter. Most indicator tips (assuming you keep an indicator on your height gauge of course) are less than .03" around.
 
With the tools you have, if the tips of the calipers won't fit into the grove. The back of your calipers is a depth gauge.
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I like the idea of grinding flats on a drill bit shank, like a 1/16 bit to just fir the grooves and measure across.
 
Wow, there are a lot ideas to digest. I am going to be machining a new piston for the first PMR model I made, and I will definitely try many of these options. I love measuring things both accurately and precisely. It's a sickness.

Thank you all for your help.

Tom
 
Nope, it's not a sickness of any type, it is the way of life for a machinist.

"Billy G"
 
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