Gerhard/Reflection
Thanks for your intersts and positive comments.
Shop time over the last couple of days has been a bit restricted by other commitments. Any way managed to get a few hours in and complete the port flange. By way of a off topic but related bit of kit I took delivery of an coax indicator, I got it from amadeal on ebay
www.amadeal.co.uk at £44 + post it was the best price I could find in the UK.
Its quite a long bit of kit and I was strugling with head room what with my rotary table and collet chuck adding to the height, then I remembered a tip from a friend that I could use M3 collets this would give me an additional 3" of room to play with. The coax has a 10mm shank but my collet set is imperial so i made a split collar to use with a 1/2" collet (note to self get a metric set of M3 collets).
So her we are
And this is how you use it.
With a stylus in the bore (or OD) and the outrigger stopped with a magnetic stand, this is to stop it whizzing round and to keep the dial facing you. Run the mill at about 200 rpm, adjust one direction to a point where you get the least dial movement, do the same in the other direction, repeat again, repeat again, after three interation you should end up with zero movement, and thats it you're on centre line, a lot easyer and quicker than having to crane your neck with a dti.
Back to the port flange, for my first attemp I used a bit of scrap yard alluminium phospher bronze, but this material was up to its usual tricks and was a bitch to machine, I don't know now why I tried it. Made onother from a nice bit of free cutting brass, this is a straight forward turning job so no pics.
Now for another bit of off topic but related. The ports are 2mm wide and I don't have a 2mm diameter cutter, cutters this size cost an arm and a leg, and I can't see me using this size very much, but I remember reading that in the "good old days" people would use a D bits to cut the steam ports for model loco, so I set too and made some 2mm dia D bits.
Truning the dia
Sectioning to 1.1 mm:- 0.1 above centre
I blacked the cutter up so I could see what I was doing then with a fine file and under a magnifying glass I backed the cutter off.
Heated them up to cherry red and quenched in water, then gave them a rub on a stone to sharpen the edges up, and her we are done.
To machine out the ports I decided to use the PCD function on the DRO combined with the movement of the rotary table.
Centre the job up using the Coax indicator.
Set Rotary table on zero deg
Set PCD function to drill 8 BA clearance for the clamp screws and drill.
Then set PCD function for port position, drill 1.8 mm hole in each port position using DRO.
Rotate RT +13.5 deg use DRO to drill 1.8 mm at each port position
Return RT to zero then back -13.5 deg use DRO the drill 1.8mm at each port position.
Her we are with all the holes drilled
Then using the little D bit join the holes up by rotating RT 27 deg.
Thats it job done, her it is in position. The D bits worked great them milled a nice accurate 2mm wide slot.
I've completed the assembly drawing for the engine so I've attached it to this thread.
Have fun
Stew
