06-11-2017, 11:32 AM
Thanks for the reply ieezitin, I understand what you are saying (I think) but I cant exactly understand how it will help me.
I understand that the rough casting needs to be machined in the first instance to get a datum to reference from. Once the crown and skirt have been cleaned up in the lathe then they will provide a reference to get the depth of the bosses from the bottom face of the skirt.
Also I can see that a jig will help to hold the piston without deforming it but will a mandrel locate the bosses to avoid the situation in the below picture when transferring from lathe to mill? Also, the pistons are approx 3 1/2" in diameter, what would you make the mandrel out of bearing in mind I only need to do 2 pistons? Do I need to buy some 4" stock?
The gudgeon pin will need boring on, I assume, a milling machine.
What I want to avoid is illustrated by this sketch.
![[Image: Piston%20Hole.jpg]](http://i375.photobucket.com/albums/oo198/jpwbrookes/Harley%20F/Piston%20Hole.jpg)
The question is, when transferring to the milling machine what is the best way to index the bosses. I should mention that a friend of mine has said I can use his Bridgeport (but it doesn’t have a DRO).
I did think about holding the crown in a rotary table held vertically on a surface plate and then getting the top of both bosses at the same height. The issue with this is I don’t have a surface plate (yet). Is there another way that I am not seeing that doesn’t need a surface plate? (I am planning to get one eventually but its not at the top of my list yet.
Thanks,
John
I understand that the rough casting needs to be machined in the first instance to get a datum to reference from. Once the crown and skirt have been cleaned up in the lathe then they will provide a reference to get the depth of the bosses from the bottom face of the skirt.
Also I can see that a jig will help to hold the piston without deforming it but will a mandrel locate the bosses to avoid the situation in the below picture when transferring from lathe to mill? Also, the pistons are approx 3 1/2" in diameter, what would you make the mandrel out of bearing in mind I only need to do 2 pistons? Do I need to buy some 4" stock?
The gudgeon pin will need boring on, I assume, a milling machine.
What I want to avoid is illustrated by this sketch.
The question is, when transferring to the milling machine what is the best way to index the bosses. I should mention that a friend of mine has said I can use his Bridgeport (but it doesn’t have a DRO).
I did think about holding the crown in a rotary table held vertically on a surface plate and then getting the top of both bosses at the same height. The issue with this is I don’t have a surface plate (yet). Is there another way that I am not seeing that doesn’t need a surface plate? (I am planning to get one eventually but its not at the top of my list yet.
Thanks,
John