06-11-2017, 02:18 PM
John
its very hard to communicate this problem using this posting method so forgive me if i have not the correct understanding of it..
going back to the diagram once you have faced off the top of the piston you have a Zero point to work from, placing the flat surface of the piston on the mill table allows you establish a center line of it where you can bore a small lip into the now bottom of the piston thats looking straight up, this bored lip acts as a reference for center of the piston also a register for your fixture.
In the same sitting on the mill you now can mill off the gudgeon pin faces ( B & C ) now you have established a square using the known center of the register lip ring. You also have established a zero point or zero degrees in reference to bosses (B & C) mark this point on the fixture.
now to bore the hole for the pin: the fixture seats into the milled boss surface's now if you put the fixture on a chuck or V-Block it can be bolted to a angle plate on the mill or even better a spin indexer, now you can find three important things.. center of the piston from the fixture, distance from the top of the piston to the center of the gudgeon pin, plus You know where you are in space in angle of degrees....
By doing all this work you have established a center in X Y Z... by knowing all three you can achieve anything you need to do to it... hope this makes sense.
you will spend more time in making the fixture than machining the parts this is always the case but you gain repeatably by getting two equally machined parts and the luxury of knowing where you are in space at anytime.
This is just my view of machining this there are many ways to achieve this some maybe even more simple than mine as they say there are ten ways to skin a cat...
Anthony..
its very hard to communicate this problem using this posting method so forgive me if i have not the correct understanding of it..
going back to the diagram once you have faced off the top of the piston you have a Zero point to work from, placing the flat surface of the piston on the mill table allows you establish a center line of it where you can bore a small lip into the now bottom of the piston thats looking straight up, this bored lip acts as a reference for center of the piston also a register for your fixture.
In the same sitting on the mill you now can mill off the gudgeon pin faces ( B & C ) now you have established a square using the known center of the register lip ring. You also have established a zero point or zero degrees in reference to bosses (B & C) mark this point on the fixture.
now to bore the hole for the pin: the fixture seats into the milled boss surface's now if you put the fixture on a chuck or V-Block it can be bolted to a angle plate on the mill or even better a spin indexer, now you can find three important things.. center of the piston from the fixture, distance from the top of the piston to the center of the gudgeon pin, plus You know where you are in space in angle of degrees....
By doing all this work you have established a center in X Y Z... by knowing all three you can achieve anything you need to do to it... hope this makes sense.
you will spend more time in making the fixture than machining the parts this is always the case but you gain repeatably by getting two equally machined parts and the luxury of knowing where you are in space at anytime.
This is just my view of machining this there are many ways to achieve this some maybe even more simple than mine as they say there are ten ways to skin a cat...
Anthony..
ieezitin, proud to be a member of MetalworkingFun Forum since Jan 2013.