Using a dial gauge to set planer knife height

[RogerS]

Still don;t buy that. If you set the knives level with the outfeed table then it will still cut.

 

[Steve Maskery]

Yes it will, but it will plane hollow, not flat.
The front end will be lifted up onto the outfeed table (that is a tad, but only a tad, too high. The workpiece will no longer be sitting properly flat on the infeed table. When the balance moves from the infeed to the outfeed table, the workpiece sits properly flat on the outfeed table, but it is no longer coplanar with the first half of the cut. Therefore the surface is not flat, rather it is slightly concave.

S

 

[Modernist]

Roger, 5mm travel on a 60mm block gives a drop of 2 thou" to the outfeed table which is a reasonable working clearance. If the OF table lifts the work at all you will get a convex surface. I don't think the scallops have much to do with it using a normal feed rate.

EDIT
Thinking a bit more if the feed rate is 6m/min and the block speed 3000rpm with two knives then you get 1000 scallops/m i.e 1mm. In broad terms if the original travel was 5mm then 2.5mm gives us the 2 thou drop then the scallops only protrude about 0.0008" from the wood surface.

Some people strugggle to achieve that with a No 4

 

[Steve Maskery]

Brian, I think you are right, convex, not concave, I wasn't certain when I wrote it and now I think you are right.

Not flat, anyway!
S

 

[RogerS]

Fascinating when you start thinking a bit more about what is an everyday task!

Point of info..the Sedgwick has three blades.

 

[Modernist]

Fascinating when you start thinking a bit more about what is an everyday task!

Point of info..the Sedgwick has three blades.

Let's guess at 0.0005" then. Sounds pretty flat to me.

 

[custard]

You said it yourself earlier. Snipe when surface planing is when the knives are too high WRT the outfeed table. The workpiece drops off the infeed table and into the cutter head. The solution is to raise the OF table so that it supports the workpiece in line with the fresh cut surface (or lower the knives to effect same).
S

Agree that's the most common reason for snipe, but there are other possibilities. I'd guess the second biggest reason is that many IF/OF tables aren't sufficiently co-planar.