Snipe (wood machining)

Snipe, in woodworking, is a noticeably deeper cut on the leading and/or trailing end of a board after having passed through a thickness planer or jointer.

The term has its origin in forestry where it is applied to a sloping surface or bevel cut on the fore end of a log to ease dragging.

(OED) The cause of snipe in a jointer, is an out-feed table which is set too low relative to the cutter head.

This holds it steady as it passes under the cutter head and creates the friction which allows the rollers to move it through the planer.

This can flex by several thousandths of an inch (hundredths of a millimeter) due to a pressure of some tens of pounds force per roller.

The length of the leading edge affected by snipe will be approximately the horizontal separation of the cutter head and the outfeed roller (the truth of this observation is evidence of the correctness of this explanation).

The table remains at full downward deflection until the trailing end of the workpiece disengages from the infeed roller.

This brings the workpiece closer to the roller / cutter head assembly and increases the depth of cut, again causing snipe.

The length of the trailing edge affected by snipe will be approximately the horizontal separation of the infeed roller and the cutter head.

Some planers have a fixed table at the bottom of the frame and the roller / cutter head assembly moves up and down to set the thickness.

The cause of snipe is essentially the same except that the table is likely to be stiffer and it is easier to think of the cutter moving upwards due to the roller pressure.

With a small, moderately priced combination jointer/planer the change in depth of cut can be in the range 0.003 to 0.005 inches (0.08 to 0.13 mm).

In oral discussion, professional woodworkers at a premiere art show reported essentially zero snipe with large, floor-standing planers.

[2] Some planers feature a lock[3][4] which, when engaged, supports the table or cutter head assembly more firmly than the mechanism that raises and lowers it.

If the sled is sturdy and as wide as the bed it may reduce movement in response to roller pressure and produce less snipe.

If the planer is wide enough, they can be fed side-by-side and overlapping, but the result should be checked for other problems due to the pieces not being on center.

[11] The work should enter and leave the planer without being pushed down, up or to the side to any degree that affects the function of the feed rollers.

Also, a straight edge can be placed on the unaffected surface of the workpiece and the drop to the sniped area measured with a feeler gauge.

Knowing the feed rate (a little under 4.4 inches per second), the distance traveled by the workpiece can also be read from the graph (refer to the bottom X axis).

At C (about one-and-a-half inches beyond B), the workpiece has moved past the cutter head far enough that it meets and passes under the outfeed roller.

It might be conjectured that the cutterhead applies an upward force to the workpiece to remove material and that this distributes differently according to its position.

A commercially milled canarywood board showing snipe of 0.013 inches (0.33 mm) for the first 1 + 7 ⁄ 8 inches (48 mm).
A white cedar board showing snipe of 0.005 inches (0.13 mm) for 1 + 1 ⁄ 2 inches (38 mm) after passing through a thickness planer.
A charcuterie board prepared for thicknessing with leading and trailing snipe blocks.
A charcuterie board prepared for thicknessing with side rails to avoid snipe.
A dial indicator recording vertical table movement in a thickness planer.
Planer table depression recorded by a dial indicator and video camera.