Profile Knife Grinders for Replicating Mouldings
A discussion of knife grinding equipment and techniques for a woodworker who wants to reproduce historic mouldings for custom work. January 28, 2013
Question
I’m a small shop looking for advice regarding purchasing a small profile grinding machine. I’m looking for a good used machine to grind custom knives for my shaper. We perform a lot of historic preservation work, and would like to start grinding our own knives. Is there a machine that will do both, sharpen straight blades and cut custom profiles?
Forum Responses
(Architectural Woodworking Forum)
From contributor M:
The only small footprint grinder I have seen is the Veil. Beyond that I would go to the online dealers and check out the different brands because there are lots of them. I own an SCMI made by Foley United and a Wadkins.
From contributor M:
A lot of guys will make knives by hand using a bench grinder. You cut two knifes as close as possible then use one as the cutter and the other as a balance. It works on shapers, but a real moulder will need proper knives. Having a custom knife made is not very expensive. You likely have a saw shop in your area that can do it.
From contributor L:
Before I had a molder I hand ground lock-edge shaper steel using soft white wheels on an 8" bench grinder. I made a lot of reproduction moldings that way. If you have a heavy shaper it will tolerate some out of balance but you will need to turn the RPM's down a bit.
My first profile grinder was a Weinig 925, I don't recommend it. We currently have a Weinig 950 that is a good small shop grinder. They come up on the used market fairly often. It will grind profile or straight knives up to 9". You should get a balance so your knife blanks start out balanced. A profile grinder has adjustments for the hook angle, left and right back bevel, and can use quickly produced plastic templates that are true shape. The grinder automatically compensates for knife protrusion keeping the back bevel uniform. It also can be set to do both the primary and secondary bevels, not easily done by hand. Knives don't need any additional honing either. The grinders come with a coolant tank, filter system, and pump to flood the knife and abrasive wheel. They also have a wheel profiling device that matches the wheel to the template tracing pin. Get an arbor that matches your head's bore. You can bush down with a little loss of precision but can't go the other way. Our molder has 1 1/2" shafts so we bush the heads to 1 1/4" for the shaper and use the same heads for either. You can get heads with two different angles so you can run as either hardwood (birch/maple) or softer woods, (gum/poplar.) Get blanks for the two unused slots.
From contributor K:
We use a Rondamat 934 for our grinding. We mostly buy our knives with a template and use the Rondamat for re-sharpening. It takes a while to grind from scratch, make a template, etc. unless you do it all the time.
From contributor H:
I think most shops that have the Viel grinders use them more for emergency sharpening than profile grinding but it's worth taking a look.
From contributor R:
I used to own a Viel knife grinder. I used it at first to create custom knives for my Woodmaster. Later I used it to make shaper knives for my employer. I too did a lot of historic reproductions with it. I had great success cutting steel with it, and yes, it can sharpen knives too. There are limits to the width and depth of the knife you can grind, but for the price, there is nothing comparable. I was able to get the router bit attachment for it as well, and that made it possible to create bits that matched the molder and shaper knives. It’s very helpful for curved doors and such.
From contributor J:
Personally, I am old school. I just use a bench grinder and that's good enough for me. I really take my time and I am never in a rush to finish my jobs.
