I don't know what you mean by parallel.
I did it by putting the indicator bearing over the knife and rotating the
As each knife passed it would raise the indicator bearing. What is wrong
It doesn't have to be at TDC, but then you don't know if they are even with
the outfeed table; just that they are even to each other.
The 'parallel' he is talking about is a machinists set up tool. It's a
rectangular bar of steel with precisely parallel edges and faces.
Normally it is also ground very smooth.
Laying the indicator tip against that smooth face is easier than trying
to get it to hit the knife edge. That's all.
You are right, TDC is irrelevant. What IS relevant is that the
relationship (angle and distance) between the cutters and the indicator
tip not change between measurements.
The parallel is a machinist's parallel. Usually sold in pairs, typical
size might be 6" long, 1" wide, 1/2" thick. Precision ground parallel
and flat on all faces, hardened steel.
Most dial indicators have a convex contact. If you want to accurately
set the jointer knife, you have to make sure that when it is exactly at
TDC it is hitting exactly the lowest point of the contact. Pretty
tough to do unless, as with Ed's jig, you fix the knife at TDC and run
the contact over it.
If you put a parallel in between, you don't even have to make sure that
the indicator is on a wide, flat stable base. You can use it on a
magnetic base. It may not read the same when you set it up on the
other end of the knife, but that doesn't matter. The only thing that
matters is how much the knife lifts the parallel when it rotates.
When I saw the wear pattern on the old set I realized
Could be as simple as having the grinds at somewhat different angles. Makes
the one blade more vulnerable to chipping on a fragile edge than the one
ground properly. Never had the courage to lay a stone on the outfeed and
make that secondary bevel like some books recommend, but that is even less
subject to wear in theory.
Also gets them nuts on with the level of the outfeed without fiddling....
HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.