Cheers Dave
Made a start on the cross head guide bar, I'm using a bit of 32mm dia free cutting mild steel, but aluminium could be used if you wish.
This is the type of job you have to think through to get the correct machining sequence, the important features are the 16mm bore that the cross head works in and its concentricity to the 24mm counter bore that the front cylinder cover fits on, this will keep the cross head centre line on the same centre line as the cylinder bore.
First op centre drill and turn down the 24mm diameter,
As the wall thickness at this end will only be 2mm I wanted to drill the 20mm as the last op, so I put down a 3/8" pilot drill followed by 1/2" roughing drill. For these drilling operation I had to support the front of the bar with a fixed steady.
Flip the bar round, and face to length and turn 28mm dia.
I was strugling to get enough reach on the tail stop over the top of the saddle, so I though if a take the sadle off I'll get closer, then I though, no if I take the tail stop of and put it in front of the sadle that would be a lot easyer.
Drilled with a searise of drill finished drilled the 20mm dia, then put a 15.5 mm drill through, and finshed of the cross head dia with a 5/8" reamer, I was real lucky that I hade thease sizes amongs my limited selection of larger drills and reamers. I was planning on boring this dia out but I hadn't got a boring bar that long, and if I had it would be a dificult job, being on the long side to get a good result, if you havn't got a reamer a drill with corner slightly radiused would do the job, the size is not that critical you can make the cross head to fit.
Bored the 24mm counterbore a nice push fit on the front cover.
As these two critical feature were finished at the same setting they should be nice and concentric.
Swap it round the other way and finish the other end off with a 20mm drill to depth.
Her it is on the cylinder.
Tomorrow I'll mill it to its final shape.
Stew
