David C":qdiwe2fa said:
Matthew,
I warned for many years, that excessive torque on the frog fixing screws might distort a Bailey style body casting, just behind the throat. The machining was very poor in the 80s and 90s and the cast metal was very soft. I was sure this happened.
Recently I was restoring some old Stanleys, no5 & 5 1/2 from about WW2, and decided to see if I could detect any deflection, with a test dial indicator and magnetic stand. (After "seating" the frog). I could not.
I then tried varying lever cap tension, as I had seen it suggested that this might have some effect, but could detect no change, as I expected.
Accurately machined Bedrock frog fixing has no effect on the sole. I am quite certain of that.
So was it only new Bailey planes, in the second half of the last century, which exhibited deflection of the sole, and who might have done work to demonstrate this?
Best wishes,
David
David,
To get any conclusive data on sole deflection, you may have to resort to an inspection grade or calibration grade surface plate and a tenths clock. You may have to devise a jig to hold the plane under test, as well. I doubt that a DTI with 0.001" resolution would be sensitive enough to detect deflections of even a try plane, and a workshop grade surface plate (especially the budget ones) may be more 'out of flat' than the plane.
All castings as thin as plane bodies (and in casting terms, plane bodies are very thin castings) will distort under their own weight, and the added loads of frog screws, lever caps and even handle fixings will produce distortions. How much? Enough for some to be significant, others less so; but if the plane sole is finished with those loads applied, it will be true enough, and certainly within the British Standard allowance for out-of-flatness. About a century and a half of experience also suggests that once the plane has been 'set up', whatever deflections there may be are not noticable enough to affect adequate performance.
In practical terms, to avoid any deflection problems, lap the plane sole with the frog in place and the frog screws at working tightness, the blade in place (but retracted) and the lever cap at normal tension. Also pay close attention to the flatness of the lapping surface - the plane flatness can only reflect the flatness of what it was lapped on. Most of us find that a piece of float glass on a clean, flat bench is plenty good enough to give good working planes. If you need anything flatter than that, you may have to resort to surface grinding or similar techniques. (Personally, I don't think it's worth the bother.) Checking HOW flat it is afterwards will need some very fancy metrology kit.
In general, if a plane will take shavings thin enough to be transparent, it's flat. Another test may be to make three straight edges. When all three will mate against each other without showing any light, they are straight, so your plane sole is plenty straight enough.