My checker says its a 32
Is this a Rorschach test? :-)
32 micro finish?
The view from my front window during Sandy?
And here I thought I was looking at the MTFCA forum, And to think all this time I'v been wrong
Same new part modified to an 8
The only part of original I have to go by. Fellow from down under said the pin is as smooth as a wrist pin. He has a NOS pin.
Picture is a Ford wrist pin taken in the center under the rod small end. it appears to be an 8 or less.
Congratulations it's a boy.
Graph George sent me notice the finish you can expect from machining methods. An 8 with reaming and 32 with boring. as most of us would do. Then spin a triple gear with a 32 finish on a pin with a 32 finish and see if you can lock it up with a reasonable clearance!
"Do not attempt to adjust you television". "We have taken complete control".
I packaged and shipped a painting like that once. Stupid thing was worth thousands.(But not to me.)
Check this out! engineer is way sharper then I am!
My first look, I was right! But my joke answer was going to be "F" scale tornado, However I like Charlie B, tim m, Mike S, answers a lot better! (Great minds think alike?)
The point I am trying to make is the reason triple gears lock up with clearance under 4 thou is the finish on new pins and the finish from boring the bushing with a lathe.
I don't know what the clearance could be if both had good finish but Herm's vintage reamers cut an exact 3 1/2 thou hole. As I recall the numbers on the reamers were under 3 thou.
This story is my opinion but when you can see and put a number on new pin finish along with seeing what a lathe bored bushing finish looks like with about 200 power the issue becomes clear.
Tim, I got one of those pictures you jokingly mentioned. Then. Junior called with the good news. Grandpa..Bugger me. I didn't know what the heck I was looking at!
Good detective work Paul.
The recurring problem with ‘tight’ rebuilds built to the Ford claimed ‘factory clearance’ is one due to more than actual ‘clearance’. Many other factors contribute, and you have focused on what I believe to be the leading cause far and above other areas of ‘good practice’.
A bronze bearing needs to ‘self-lap’ to the ‘system’ it ‘sees’ and during this period the chance for that ‘stick’ illustrated is extremely high. Others have reported that it does not take much ‘stick’ to find the bronze bush spinning in the gear, or the pin to become loose in the flywheel.
Tearing an entire transmission down a 2nd time is a huge task. This is why those ‘in the know’ with much rebuild experience always suggest that the target clearance be modified to 0.0035” – 0.0045”, with all else being good machining practice as to position and run-out. By adding this extra ‘thou’ or so becomes a cushion of safety factor to help mitigate any effects of the initial ‘stick’ by allowing more oil to flow and be held in the space while this final ‘self-lapping’ takes place. Of course Ford recommended a re-build at 0.005” so there is a bit of a paradox that ‘life’ of the rebuild would be less, all other things being equal. In the past those who have targeted the Ford claimed 0.002” clearance and used best machining tolerances and control, still find themselves more often than not in the ‘what happened, I did it right’ club. The 0.0035-0.0045” followers have just learned that ‘it works’. Yet each year we have one or two who believe they are good enough, and have tools that are good enough, that they can shoot for the 0.002” factory claimed clearance only to find I believe that most of the time they wind up ‘swallowing’ something anyway.
I do believe you are on to something here and anxiously await what the power of a 200x ‘scope might reveal followed with your own field experience on your test rebuild when you get to that point. I can confirm that the actual Ford drawings for the parts involved only call for ‘a finish’ and do not specify what that finish needs to be. Ah, if only the BFM archives and ascensions would disgorge the manufacturing run cards (what was conventional wisdom in manufacturing documentation at the time and in the industrial era) then so many other issues relating to our stewardship would be answered almost once and for all!
Thanks George, Herm,
Without help from some sharper folk then I am this information would not be possible.
Think I have then pin finish down, now to finish a bushing to a reasonable finish without a reamer.
Time saver yellow 300 grit will be used running the pin in the lathe sliding the triple gear over it.
What did Herm say?
Herm has given me information asked for with PM like checking the exact ream his vintage reamers give on a bushing. His tools are much better then mine and mine are much better then the average.
Tricks like turning a starting edge on a bushing were explained to keep the bushing from distorting while pushing in.
After seeing 200 power pictures folks seldom see he agrees there is a big differance.
Drag a razor blade down a 32 finish its easy to hear and feel do the same with an 8 finish and its not. One easy check for the average T guy.
As a general rule, the following finishes can be expected from the following operations;
Rough milled finish: 250 - 125
Finish milled or turned finish: 32 - 63
Typical ground finish: 8 - 16
Lapped finish: 8 or less
Lapped mirror finish: 4 or less
When testing micro finish, it makes a huge difference whether you're testing parallel to the "grain" or "lay" of the finish or, perpendicular to it. You would typically take your measurement in the direction that the mating part will take when in operation.
You being an engineer Jerry with better test knowledge then I have and probably a better tester I wish you were a neighbor.
I could post the 32 finish on the finish checker I checked with but it does show up with 200 power you can even feel it with your finger nail on the new pin. Buy some pins and check with your equipment, if you have a good Ford wrist pin check the center under the rod small end. The more help with good opinions the better.