We have a fellow in our shop who insists on honing the backs of what are essentially new shaper knives. I am told by our tooling fabricator this is not ever needed and can, in fact, be dangerous.
Any feedback is welcome.

To my knowledge its always been a common practice only if you need to squeeze a little more life out of a set of knives and is no substitute for having them reground. Its kinda like a get out of a bind situation if youve had a custom profile ground and your at the end of the run and the knives are getting tired but you need just bit more footage. And Im talking a fairly light honing if the knives are not heavily worn or damaged. If they were honed hard, your changing the profile but that would be at the level of grinding not honing.

As far as dangerous I have no idea how that would be the case as long as your in the honing world and not the grinding world. The amount of material removed with honing on some fine abrasive is ridiculously small which again, any decent knicks or wear on the knife your simply never going to hone it out.

Just my $0.02

There is absolutely nothing wrong with lapping a corrugated shaper knife. They are ground with a 60/80 grit wheel and technically not very sharp.

The idea that you will change the profile is absurd. You would have to lap the knife as if you were trying to flatten a chisel.

I've been using MoldingKnives.com for about 15 years. They cut knives with a hot wire epdm machine. They are not ground, there is no template, no regrinding. They come razor sharp. I typically lap them on a 600 grit diamond stone after I run a decent amount of material.

Back in the day I lost a few templates. I took the knives to my local machinist and he surface ground the backs.

You don't say what type of shaper knives are involved. I can't see any reason not to hone the back of corrugated knives. The gibs will still hold the knives in place just as solidly. There are other styles of knives though that I might not want to hone. Most of those are old, out of date knife systems though that you really shouldn't use anymore anyway.

BH Davis

Adam,
Its a fine point of contention but I have numerous times tweaked the fit of a mating set of knives (say a cope/stick or similar) by lapping (way more aggressive than lapping) a set of carbide knives to tighten/loosen the fit.

Changing the profile is likely not an issue running Colonial casing or some other casing profile. But the simple fact is you _are_ changing the profile when you lap the backs. Its just basic math. Whether its enough to cause you an issue is up to you.

None of my knives are cut on an EDM and shipped. They are all ground off a supplied template. Im sure Im likely not pulling enough volume to be dealing with an EDM supplier like you.

Mark B,
We are small volume. If we were large volume. I would probably do in house.

I looked at moulding.knives.com, because they were faster, better and the knives are outstanding. Fully digital cad/cam. The kerf of the cutter is a 1/32. The amount of theoretical change as you lap would be barely measurable. When you sight the knives on a crown you can’t see the shape change top to bottom.

They are better knives when they arrive. They are better knives after they are lapped.

Its like sharpening a chisel with a bench grinder vs a stone.

Give them a go. Excellent customer service

moulding.knives.com