I’ve seen these questions raised on several threads, and for many years didn’t know the answer to these myself. I just stumbled upon the “answers” which reminded me of the questions, so I figured I’d post it here for anyone that might be able to use it. I stumbled upon these on Lee-Valley website which is a golden fountain of knowledge if you know how to find it (some of their articles and tips are not visible, nor easy to come upon unless you stumble upon it by chance , or really searching hard for it).
Cap Iron (for Bevel Down planes)
So, how much should the blade protrude from the end of the cap iron for planing applications?
for smoothing and working with figured wood – the blade should protrude about 1/64” from the end of the cap iron, to give a very fine, and light shave before the shavings contact the cap iron and curl upwards.
for rougher cuts, and faster material removal, the blade should be set 1/32” – 1/16” from the end of the cap iron – the more it protrudes, the rougher and faster the material removal will be, softer wood can take a rouger cut, while hardwoods might cause the plane to choke, so a little trial and error is required to get a feel for it.
How tight should the Lever Cap be set? and this also relates to the question: can blade adjustments be made when the lever cap is locked? or do I need to unlock the lever cap to make those modifications?
The Lever Cap screw should be tightened down 1/4 of a turn after it makes contact with the cap/blade. This creates enough pressure for the Lever Cap to hold the blade securely in place, while still allowing enough freedom for the adjustment screws to push the blade in/out and lateral movements. In this case – it is not necessary to unlock the lever cap in order to make changes to the blade positioning (in/out, left/right). the adjustment screws and lateral adjustor should move freely, as should the blade (although pressed firmly against the plane’s frog/body).
if the adjustment mechanisms are hard to use when the blade is locked in place – then either the lever cap is locked too tightly, or the adjustment mechanisms aren’t clean. be careful as putting too much force on those might break them off.
Special Thanks to Lee Valley for putting out this info out there for anyone to use.
Edit: here is an illustration (from Lee Valley which has excellent guides and information) of the handplane which shows the Lever Cap (which holds the blade to the plane) and the Cap Iron, which on Bevel down bench planes curls the shavings and controls the penetration of the blade in the wood:
-- ㊍ When in doubt - There is no doubt - Go the safer route.