Grinding custom shaper knives

Does it make sense to grind your own shaper knives? June 6, 2001

I am looking for information on custom grinding shaper knives. I gather that corrugated back steel is not suitable for freehand grinding and I'm not quite ready to step up and buy a Weinig profile grinder.

We are running a 3 HP Delta HD shaper with 1/2" and 3/4" spindles and an old Beach 5 HP with a 1" spindle.

I'm aware that you can have custom profile knives ground, but I would like to develop the in-house capability for short runs of odd-shaped stuff. Whether or not this will make financial sense remains to be seen.

Forum Responses
It is very difficult to hand-grind corrugated backed knives (as you mentioned). One of the main reasons is that you will not be able to adjust the projection (the knives must fit the corrugations on the head).

I use lock edge shaper collars with beveled steel knives. These can be adjusted to the projection needed. In the old days, we used smooth beveled steel knives, which were a safety problem if not set up properly (the knife could fly out of the collar).

This is not a problem with the lock edge "system." Unfortunately, I believe that there is only one company still making/marketing lock edge collars (Schmidt).

Tyler Machinery in Elkart, Ind. has an article on how to grind knives freehand using a template and grinding to the template. It is several pages long.

I thought about trying to grind, but I figured with the time I would spend making the knives, I could get more work done and just buy the knife made professionally. A $35 template fee and $20/inch/knife didn't sound that bad to me.

For short runs, it is not entirely impossible to hand-grind corrugated knives. If you get a very good grind on just one knife, generally it will cut pretty nice. Just back cut the second knife a little so that it is not making actual contact with the piece being machined. This second knife is acting only as a balance knife, in this case. I find for short and one-time runs, this works quite well and is a timesaver.

You make a very good point. No two hand-ground knives are ever exactly the same. So, in reality, one cuts the final finish (or one of the pair cuts the final finish for part of the shape). We have also, as you suggested, used a single profile knife with the second for balance. Usually need to take lighter cuts and use a slower feed.