Metal Shapers

by Kay Fisher

Shaper Tool Bits

Part 3 of 3

The Shearing Bit

This part of the shaper bits column is another contribution by Pete Schaeffer. Shearing tools (finish tools) are documented in many old machinists books, which all have sections devoted to shapers and planners. The following is from Pete’s old web site, which is currently not available. To see the whole article and all the pictures in higher resolution, look at the rec.crafts.metalworking drop box archive:

The pictures are files shaper01.jpg shaper02.jpg shaper05.jpg shaper06.jpg shaper07.jpg shaper11.jpg and the accompanying text is file shaper00.txt

Finish Tool End                                  Photo by Pete Schaeffer

“This is a finishing bit, pretty much as described in Moltrecht V. II, p. 14. This is the cutter shown at C in the drawing on that page. If you look it up, note that the end-on drawing in the figure is wrong: it shows the angle going backwards. In this photograph, the side of the cutter that's on top is actually the front. The edge is curved, and gets pushed through the work at an angle of 25 degrees, as specified by Moltrecht.

Finish Tool Left Front                        Photo by Pete Schaeffer

This shot gives a better view of the curved edge and the angle at which it meets the work. The cutter is mounted vertically, with little or no angle. We are standing in front of the shaper, a little to the left, looking at the left hand side of the bit, which will feed from right to left.

Finish Tool Right Front                     Photo by Pete Schaeffer

This is the same setup, but now we've moved to the right. You can see the curved edge and the angle at which it shears through the work. (This photo makes it look as if I don't have enough front clearance on the blade. Turns out that that was the case. After a regrind, things went much better. It's a little hard to judge the angles when the cutting face is 25 degrees away from usual.)

Finish Tool Front                               Photo by Pete Schaeffer

Same setup again, looking directly from the front. Notice that only a small part of the edge actually touches the work. This cutter is for light work: Moltrecht recommends 0.001" to 0.003" depth of cut.

Finish Tool 0.004 Depth                    Photo by Pete Schaeffer

Chips from the finishing cutter, about 0.004" depth of cut and 0.004" feed per stroke.

Finish Tool 0.002 Depth                    Photo by Pete Schaeffer

More chips from the finishing bit, this time with about 0.002" depth of cut and 0.002" feed per stroke. These are fine chips: a pile of them look like a Brillo steel wool pad. Be careful, they’re sharp!

Finish Tool 0.002 Depth2                  Photo by Pete Schaeffer

Chips, same depth of cut, 0.006" feed per stroke.

Finish Tool Cutting                            Photo by Pete Schaeffer

This is a chip coming off the work. I think that this picture gives the best idea of how the finishing bit cuts. It's not at all hard to take 0.001" off the work with this bit.”

Thanks Pete for that great contribution. Keep sending me email with questions and interesting shaper stories.

My email address is