Tage Frig's Jointer Knife Sharpening Method Using a Router ... Anyone Try It?

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Forum topic by Lovegasoline posted 05-18-2018 04:58 PM 646 views 0 times favorited 2 replies Add to Favorites Watch
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171 posts in 918 days

05-18-2018 04:58 PM

In the book ‘Tage Frig Teaches Woodworking, Book 1: Joinery’ he elucidates his method of sharpening jointer knives without removing them. It doesn’t seem to be a method in common use so I’m really curious if anyone has tried it. I’ve had that book for a quarter century – after raiding the libraries (haven’t been to one of those in over a decade??!!) – it was the first woodworking book I ever bought and it’s been some years since I’ve dipped back into it. Tage Frig seems like such a no nonsense guy, he doesn’t obsess over minutia but seizes the heart of the matter of how to effectively and efficiently get stuff done.

It involves using a router with a simple auxiliary plywood base with a medium grit grindstone in the collet (plywood base is about a foot long and it’s mounted offset so the router’s spindle/collet hangs off the end of it…allowing the router to be cantilevered over top the cutterhead and knives).
Another simple jig is used to position the knives so they are equally ground. It’s made out of a thin stiff strip of steel or aluminum approx. 7” long and it’s mounted by drilling two holes in the jointer’s infeed table (one hole is tapped to accept a screw which secures the strip tightly to the table & gives it a repeatable position, the other hole accepts a pin – he uses a nail set – that keeps the metal strip oriented but allows it to rotate on the screw and swing out of the way … to quickly reposition it for sharpening the subsequent knives). The cutterhead is pushed up against the end of the metal strip (which acts as a positioning stop) and the infeed table is lowered until the bevel of the knives are parallel to the outfeed table. He uses wooden wedges at both outside ends of the cutterhead to hold it in place.
He then sets the router with plywood base on the outfield table and lowers the router until the gritstone just touches the knife and runs it back and forth until it stops cutting. The metal jig is swung out of the way, the cutterhead is rotated, metal jig is swung back into position oriented by the pin, cutterhead re-secured with wood blocks, and the 2nd knife is sharpened, then the 3rd, etc. When a bur is formed on the back of the knives they’re done. He makes a point of stating he doesn’t bother to remove the bur and he doesn’t further hone the knives afterwards, but he says the latter is optional – one can run a stone across the knives if one wants to hone the edges. He gets about 5 sharpenings before having to raise the knives position.

-- “It is the beginning of wisdom to recognize that most men are fools and knaves, but it is the end of wisdom to embrace that vision.” -Arthur Kleps

2 replies so far

View davezedlee's profile


60 posts in 1704 days

#1 posted 05-19-2018 02:24 PM

check this link for a Foster Knife Grinder, which is probably what he based his idea off of

seems like it would work fine, and save some shop time between proper, full, regrindings

View Lovegasoline's profile


171 posts in 918 days

#2 posted 05-19-2018 07:15 PM

Very interesting tool and you’re right, they operate on the same concept (in your link I like the use of the old ruler as a jig).
What’s intriquing about Tage Frig’s solution is that it appears simple to implement as well as being dirt cheap.

-- “It is the beginning of wisdom to recognize that most men are fools and knaves, but it is the end of wisdom to embrace that vision.” -Arthur Kleps

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