I received my new cylinder today from PM Research.
Wow, that is good customer service.
I've ordered various things from them over quite a number of years, and they have always been truly excellent for me!
Made some progress.
I ordered and received a new cylinder to replace the one I screwed up.
The new method of centering the cylinder body in the four jaw worked beautifully.
I have two identical cylinders within .002”.
They are concentric and true to the bore.
Working with brass is a real pleasure.
Before I go further I need to clean up the castings to get ready for the drilling and tapping operations.
A most excellent result .... well done!
Thank you,
Looking through the instructions, both cylinders need to be faced at the inlet ports, drilled at 90 degrees and tapped, then a 20 degree set up so the steam/air can be delivered to the cylinders to drive the piston.
This will be a careful set up.
I don’t think I have ever tapped 4-40 or drilled down to a set point.
Looking forward to it.
Not wishing to assume what you may or may not already know, but just a friendly comment.
With small taps like 4-40, they are rather weak and very brittle, so easily prone to breakage, and there is no need to ask how I know this. Once you start feeling any real resistance to turning forward, go backwards at least 1/4 turn or until you feel the "chip" break away, before going forward again. The smaller the tap, the more gently I progress, but typically find that a 1/2 turn, or a little more forward, and a 1/4 turn back gets me there without the grief of a broken off tap.
Stoker, I took the liberty of buying quality spiral flute taps. They seem to require less effort and the chips clear.
Done for today. I need a 3/16-40 model tap and die per the instructions.
I had not seen that in my many overviews of the plans.
I am very happy with today’s results.
9-26-20
I drilled and counter bored the 3/32 holes at 20 degrees as directed. Once again the casting is a bit tricky to set up for machining.
I don’t know what you guys use but I used an 1/8” end mill to cut a flat then used a center drill to guide the drill bit.
It is very satisfying to have good results, as a mistake at this point would be very frustrating.
A wonderful build thread you have here.
Looking forward to following your progress.
Charlie
Well i have had a read and it appears you know what you are doing and making great progress.
If i keep up i may learn something .
Cheers
Dennis
I believe his name is Tinker John on You tube. He is pretty good with these models.
My next step is to start on the connecting rod castings, the heads and the crank casting.
These are small parts. This will be new to me.
Watching different builders on You tube, learning Turning, Keith Appleton of course and compare their approach to Joe Piezinski of Austin TX.
Joe uses trigonometry, special made one time holding devices and his digital read outs. The fixturing and holding art to this is all new to me.
No super glue.
They all get there in the end.
I hope to be back on the PM #7 in the next few weeks.
I had to make up my own machining sequences/postions for the engine I built.
Machining castings can be a bit of a trick, but I do prefer castings.
Sometimes the biggest challenge is figuring out where to grip the part.
Looks like a nice build you have going here.