Jointing of Carbide Knives

Tips on the best technique for jointing carbide cutters. January 14, 2008 UPLOADED_FILE>

Question
I am curious what techniques are used to joint carbide knives, bak pack knives. What speeds have you found work the best, what type of stones, etc.? I am milling cellular PVC, which is a granular material. I am trying to get it as smooth as possible, and would like to experiment with some other techniques.

Forum Responses
(Solid Wood Machining Forum)
From contributor R:
In general terms, the higher the number of grit on the stone, the finer it is, and the softer as well. You will get the best finish from the higher grit stones. It won't last as long as the lower grit stones. You will need a stone made for carbide profiling. I bevel both ends of the stone's profile area so only about 1/8" of stone is touching the stone. Ten degree side clearance on your knives will help you also. It allows the knives to breathe more when the stone is jointing.

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From the original questioner:
Where do I get the highest grit stone available?

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From contributor R:
I would use a 600 grit stone for carbide, available from anybody that sells quality tooling, many who have ads on this site.

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From Dave Rankin, forum technical advisor:
Carbide can be jointed with several different jointing stones. I use either a 150 grit aluminum oxide or a 600 grit silicon carbide stone. The 150 grit is a hard stone and must be prepared to match the profile exact. The 600 grit is a non-sparking stone that can be chipped in using the knives. I have used diamond stones in the past, but no longer do because of the cost.

The secrets include: Extreme accuracy in the grind. It is recommended to grind the carbide in-house in the head that will be used. Hydro-locking tooling. Joint lightly and if needed, joint a couple of extra times over HSS. Grind angle of 18 degrees or slightly higher. This allows the joint to come in easier and quicker.