06-11-2017, 03:37 PM
Thanks ieezitin, that’s helpful reply. However I think I must be a bit dim though because I am still missing a stage.
I get all of the stages in your explanation and most of it was along the lines of what I had in my mind before I posted this question.
However I still dont follow one stage of your post. Before milling B & C you need to make sure that the face of B & C is at 90 degrees to the centre line of the bosses. You skip over that bit and that is the bit that is the whole point of my question.
If you look at my "No Thanks" sketch then if you machine B & C at 90 degrees to the red lines then you will end up boring the holes so that they are not coaxial to the bosses.
In effect I am trying to avoid this.
![[Image: Piston.jpg]](http://i375.photobucket.com/albums/oo198/jpwbrookes/Harley%20F/Piston.jpg)
Which is what the previous person (NOT me) did to my first set of castings.
Getting the bore to go through the diameter of the piston is simple but it needs to go through the centre of and coaxial to the boss on each side of the piston.
I totally get that setting parts up to machine and making fixtures is quite often the biggest part by far and the actual machining bit is a small bit at the end.
I am still pondering a mandrel with a vee on one end. Or holding the piston at the crown end in a spin indexer and getting the bosses parallel to the table and then turning through 90 degrees.
When the new castings arrive I will see see what i can do.
John
I get all of the stages in your explanation and most of it was along the lines of what I had in my mind before I posted this question.
However I still dont follow one stage of your post. Before milling B & C you need to make sure that the face of B & C is at 90 degrees to the centre line of the bosses. You skip over that bit and that is the bit that is the whole point of my question.
If you look at my "No Thanks" sketch then if you machine B & C at 90 degrees to the red lines then you will end up boring the holes so that they are not coaxial to the bosses.
In effect I am trying to avoid this.
Which is what the previous person (NOT me) did to my first set of castings.
Getting the bore to go through the diameter of the piston is simple but it needs to go through the centre of and coaxial to the boss on each side of the piston.
I totally get that setting parts up to machine and making fixtures is quite often the biggest part by far and the actual machining bit is a small bit at the end.
I am still pondering a mandrel with a vee on one end. Or holding the piston at the crown end in a spin indexer and getting the bosses parallel to the table and then turning through 90 degrees.
When the new castings arrive I will see see what i can do.
John