HSS vs. carbide jointer knives

Pros and cons of both types of blades. October 24, 2001

Q.
I have always used HSS knives in my 8" jointer I'm curious if carbide knives are worth the investment.

Forum Responses
It would depend on your usage. I feel HSS gives a good finish on solid wood and holds up better than carbide in many senses. Now if you start comparing tooling systems and head changes, you might be ahead with an indexable double side carbide like the tersa, which provides quick knife changes, but it depends on how much wood and what type you run. The carbides will take a hit if you are running, say, hard maple and you have any defects. It is simply too brittle and won't hold up. Way more expensive as well.

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HSS has a sharper cutting edge than carbide. However, carbide normally lasts 8-10 times longer than HSS. It really depends on your finish requirements and the type of material you run. If you are running hardwoods and laminated materials, then I would run carbide. If you are running softwoods, then HSS would work better. If you are running all of the above, then you have to make the call between HSS and carbide. It then depends on how often you change your knives and how much time it takes you to change those knives. The carbide knives from Terminus will take the abuse from defects in hard maple and other species.

Terminus and Tersa both offer a double edge knife system. However, you do have to change your cutterhead to use either system. Terminus offers, in stock, an 8" cutterhead to fit the Powermatic jointer for $395. This cutterhead will fit other 8" jointers. The Terminus HSS and carbide knives have been found to last 4-5 times longer than the Tersa knives. They are also sharpenable. You can contact either company to get more information.

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When it comes to determining which type of tool to use, the finish quality must be considered first. If the finish quality is critical, HSS is normally better. If the finish quality is not so important, carbide is a good choice. It should be noted that carbide is more brittle than HSS and will break when HSS may only nick.

The cost is another consideration. Carbide is more expensive up front but may be less expensive in the long run. The use of a replaceable insert cutter is a great idea. The Terminus can use both HSS and carbide inserts where as most other designs only use carbide. The grade of carbide available from the different manufacturers of heads varies a lot as well.

Dave Rankin, forum technical advisor