The lever cap, along with other elements of the metal-bodied hand plane was patented by Leonard Bailey in 1858. They have been minor revisions, but it has remained almost unchanged for the last 160 years.
I’ll touch on the screw cap. Another method of securing the cap is with a knurled screw. This screw applies a locking pressure thus securing the cap. The lever screw does the same thing as the lever cap.
what does the Lever cap do?
It holds the blade assembly tight to the bed of the Frog this replaces the wedge from traditional wooden hand plane. There is no longer any need to use a hammer to adjust the plane iron or blade.
The Liver cap exerts even Force across the edge of the chip breaker and plane iron this is necessary because metal planes have a thin blade that can flex and vibrate during use which is called shatter.
Shatter on the blade can result in an uneven wood surface and caused the blade to loosen over time.
by pressing the lever down evenly across the cap iron, plane iron and the Lever cap makes these three pieces act like one solid wedge.
So how does the Liver cap work?
A cam lock applies tension between the cap screw and the Frog.
The cam lock
There’s a flat spring attached to the Liver cap that Snaps it to one of those two positions. The fulcrum of the lever has a square shape with one longer side when that side is against the spring it puts tension on the blade Assembly and holds it Tight To The Frog.
So how do you use the leather cap correctly?
You can achieve a perfect fit by changing how far the cap screw is protruding from the Frog. The perfect fit is something you learn with experience, but basically, it’s when it’s tight enough so the blade doesn’t move while you are using the plane. The screw has to be loose enough to be adjusted by the depth adjustment not and the lateral adjustment lever.
The History of the Handplane
These old hand planes are not just nostalgic but very capable tools. I use mine every day and the history behind the Bailey patents are actually very interesting.
You needed to hone your Lever Cap
You’ll also need to hone the Lever cap. Hone the edge of the lever cap by passing over a wet stone in a vertical fashion. Keep about 1/4 inch from the end where will come into contact with the chip breaker this will ensure that the Lever cap places even pressure on the blade assembly. This will also reduce shatter.
Lubricate to protect your tool
Make sure that protect the raw metal with some sort of rust inhibitor this can be paste wax or oil. I use a mix of turpentine and engine oil but you can use any tool lube on the market.