accurate indication between operations

[MrBlair]

Hello everyone, I'm currently working on a thank you gift to a few coworkers + a tour gift to groups, a Lego piece. Currently finished the first operation, faces and contours the top and sides, cutting .02 lower than necessary to give extra breathing room for 2nd operation. (mostly happy with that, except for a weird abrasion mark on the finishing pass of the sides, using a 12111810 M.A. FORD 2 flute 3mm carbide and only removing .005).



The second operation has me a bit worried, chamfer around is .01 on the outer edge, and .005 on the inner cylinders, I'm worried that if I'm off by even a small amount it'll be rather noticeable. To help with indicating I plan to put a hole through one of the inner cylinders on the bottom, to help indicate from there. Am I overthinking it, would simply removing the excess stock, and then edge finding before removing the last .02 be all I need to do? Or would using an indicator holder and finding the center of the hole be the best solution, or what would you guys do?

 

[Dan Dubeau]

Cool project. Personally I like to use the center of stock for my pickup for almost everything, especially parts done this way, as it's the best chance to blend into what's there IMO. I would just flip it over, pickup the center of stock, and deck it down to thickness, then pickup the center of the actual cut surfaces , and then run op2. I made a top hat style edge finder years ago for doing stuff like this and reaching under the uncut ledge, but don't think it would reach in this case, as there's not a lot of real estate left after holding the block.

There are times when a center block pickup isn't the best depending on the print (if there is one) or critical features that need to reference a datum/feature, but for blending in op2, to op1 on parts like this, it's the best way IMO.

 

[RobinHood]

A fixturing jig to hold the brick upside down in the vise with two planes as a reference (ie one corner of the Lego is then your datum).