I started with a "practise" crosshead
The casting was mounted in a collet to be faced and drilled 4,1mm:
From the tailstock I could then tap for the piston rod knowing this would mean the cross head would also be correct:
Compare with the sketch I had made At this point I missed the obvious
I had put two measurements on the cross head and of course I chose the wrong one
but there is no point worrying about doing things wrong as it is all good practise (I keep telling myself) Mounted on the piston rod screwed into that thread:
I could turn the other side:
Then off to the mill to mill the four sides of the cross head square and to dimension:
The cross head can now be mounted square in the vice, the centre found:
Then using a nice sharp undersized cutter a slot for the slide bars cut along the centre line to depth (yes I took the wrong depth from the drawing
)
The having repeated with a milling cutter the correct size the slot was checked with a piece of bar stock the same width as the guide bars:
And as you can see it is too tight, so moving the Y axis over a Tad:
The slot was again cut on both sides taking off a total of an additional 0.1mm. I also drilled and reamed for the small end pivot:
Before turning it over to mill the slot for the connecting rod itself. However
putting it on the engine I did not like it
This was going in the sin bin... So the other casting was retrieved... Mounted up in a collet for turning:
Again in the Square 5C holder to have the sides squared off:
However this time I have made the connecting rod slot 8mm wide and 9mm deep. To make that work I also moved the hole for the pin back .75mm nearer the back of the cross head.
I also reduced the slots for the slide bars to 4.76mm deep. This time I was happier with the finished cross head shape and bearing surface areas.
To correctly space the slide bars up from the sole plate I slide a slip gauge under the crosshead with it mounted on the piston rod and measured the required thickness. You could also use any piece of steel and a set of feeler gauges to do the same
So the good one and the rejected one:
Time to make another piece
Jo