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Why point depth mic rod?

Glorifire

Aluminum
Joined
Jan 25, 2016
Location
Miami
So Ive seen a few depth mics where the rod has its end ground to a cone, can someone help me understand the benefit of this
 
Usually getting into a recess or groove feature who’s width is less than the mics rod diameter, occasionally into a corner if the drawing is mad enough to give edge to internal corner reference dimension ( really curvy extrusions sometimes do, b4 CMM by the way)
Mark
 
Depth of drilled hole is taken at the centre, anything other than a point would measure short.

Maybe different over there, but here I always (almost anyways) see them called out to full diameter, which is easy to check with a gage pin and simple maths. I have seen the occasional print that calls out the drill point angle and overall. Worst one I saw was a drill point angle, something like +/-1 deg, and "no tool marks" that was fun. :willy_nilly:
 
Oh so for more shallow recesses and corners near radii? I can see that. Ive always seen it done to the 0-1 rod, so for grooves it makes sense because I would expect the grooves to be rather shallow. Do you also point longer rods than 0-1?
 
Ya at work the drilled depths have always been called out to the corner that ends the full diameter, but it may just be our prints, I dont have that many years under the belt so not sure
 
Oh so for more shallow recesses and corners near radii? I can see that. Ive always seen it done to the 0-1 rod, so for grooves it makes sense because I would expect the grooves to be rather shallow. Do you also point longer rods than 0-1?

Bottom line, they are most likely custom made for a job, so it might be the 0-1 or the 3-4" whatever. For the record, I have the Starret set with the 5/32" diameter rods, my 0-1 has a .062x.22 long 'stub' I spun down for some reason... If I needed to check something at a 2-3-4" depth with a groove or watnot, I would do the same if nothing better was handy or available.
 
I made a depth rod for checking full radius groove depth; piece of drill rod pointed on one end and threaded on the other for a button like the original. It has come in handy every so often.
 








 
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