Sharpness of carbide planer knives

[Dan Friedrichs]

I finally bought a set of the Titan-brand carbide planer knives (from Holbren) for my DW735.

I realize that carbide doesn't sharpen to as fine of an edge as HSS, but I was really surprised by how "dull" these seemed. That's not a complaint (as I realize they will last much longer), but when my HSS knives got to this level of dull-ness, I was throwing them away! I probably should have been using the HSS knives for much longer than I had been.

Just an observation :)

[John TenEyck]

I think you'll only know when you install and run the carbide knives. If you get more tear out on difficult wood than you did with HSS knives then perhaps you were right to change those knives when you did. The carbide knives may be just as good as your HSS ones, but I've read they don't perform as well in difficult woods. Good luck.

John

[Mel Fulks]

As stated before HSS without a grade designation means nothing since most of what is sold as HSS is only SEMI HS and is terrible about tear out even when newly sharpened. I once got an employer to stop using two new sets of that junk by betting my own money that M2 would tear out a lot less and proving it.

[Dan Friedrichs]

Oh, sorry, I wasn't clear that I did install the knives and ran some stock through them. My impression of their sharpness was based on the quality of the finished piece, how "loud" the motor whined, etc. I do need to find some figured wood to try, though.

I guess this is just a caution to people (like me) who don't have a great metric for what a "dull" HSS knife is (relative to a "sharp" carbide knife). With these carbide knives, the planer motor seems to "groan" at about the same level that, previously, would have made me think it contained a set of HSS knives that needed changing.

[Mel Fulks]

Well, since semi high speed can tear out big chunks on first use many blame the wood . Yes,I'm serious. Seen places that routinely planed 1/16 over finished thickness then wide belted off 1/6 to get good surface.

[Kevin Jenness]

I used to run carbide knives in my Makita 2040, if I recall they were Makita brand. They weren't quite as keen when fresh as the HSS ones, but did a very good job nonetheless and for far longer, and didn't add any significant power draw. They certainly were much better when newly sharpened than what I considered "time for a change" HSS. I wonder if the knives you got were properly sharpened or not a good grade or batch of material? (Whether carbide or steel, a sharp cutter should catch on your fingernail when dragged across the edge.) Have you asked Holbren about this?

[Larry Frank]

First thing with a problem like this would be to call Holbren and discuss it with them. They should still feel sharp.

[Dan Friedrichs]

I don't think there's a problem - they are certainly not "dull". But most of my learning about woodworking comes over the internet, and it's very hard to get a "feel" for when a blade should be changed via this medium :) So when people say "carbide knives don't sharpen to as fine of an edge as HSS", I didn't really have a good understanding of the difference. Now I do.

[David Kumm]

If you see much difference in finish there is a problem with the carbide. Spiral heads are generally carbide, as are most shaper cutters. There should only be a slight difference in finish quality. Dave

[Andrew Hughes]

Hi Dan,I had a set of carbide tipped knives for my Dewalt planer.They were from Infinity cutting tools.The grind on mine was 45 so if your are too this is how I sharpened them.45degree table saw cut on some scrap to hold them.They should get wicked sharp.

[Martin Wasner]

Well, since semi high speed can tear out big chunks on first use many blame the wood . Yes,I'm serious. Seen places that routinely planed 1/16 over finished thickness then wide belted off 1/6 to get good surface.

That's standard operating procedure everywhere I've ever worked.

[Mel Fulks]

Been googling this. HSS description is being way over used. Dewalt calls the knives "heat treated". I can't find anything put out by them calling the stock knives "high speed" ,but many dealers and users are calling them "high speed" and even M2. But calling them M2 is not going to make them M2. The higher grade that Dewalt sells is called D2 and they call it "high speed steel"...but D2 is not on any lists of high speed steels that I can find. I also found reviews complaining about the "low grade M2 steel " that is stock in the 735. yes ,I've posted on this subject many times. But not nearly as often as complaints about knives and wood surface quality comes up. I'm no expert on steel but I know that M2 and T1 leave a much better finish and don't tear out nearly as bad as all the soup can stuff being sold as "high speed". I think a class action law suit would succeed. Martin, thanks for verifying what I said about planing 1/16th over. The practice is a big time waster and was not done years ago.

[Martin Wasner]

The practice is a big time waster and was not done years ago.

You need a better widebelt if you feel that way.

[michael langman]

When working in the metalworking industry carbide was designed to be used on bigger lathes and mills and higher speeds and feeds to help in the cutting performance of the carbide tool.
If carbide was ground to a keen edge vibration would chip it. 1/32 RADIUS was standard on most tools. Negative Rake on cutters meant for very heavy use.
M2 High Speed steel is more suited to wood working, and you probably could have run your cutter longer then you did.
I bought 2 sets of M2 for my 4" delta Homecraft jointer from an American Industrial Cutter Mfg. Company for under 20.00 a set and they were well made and cut very well.

[Peter Quinn]

My experience....carbide tipped will never feel as sharp as HSS freshly sharpened, nor will it feel as sharp as insert solid carbide. The explanation I was given, you have to braise the carbide to the steel knife body, if you use a very fine grained carbide the braise will not have sufficient tooth to hold the carbide, so a coarser grade of carbide is used. Sharpen it all you want, it's not going to be one a razor. By it shouldn't feel dull. I've used terminus knives in a planer head and jointer that I believe we're solid carbide, fair step up in cost from those Titan knives, but the solid carbide inserts are extremely sharp. With shaper heads the finish from insert carbide blows away braise 3 wing every time. Andrew's honing jig above looks like a good way to possibly improve the manufacturing tolerances for better surface performance.

mel, we are running high quality knife stock from Wisconsin Knife works in our 4Z 20" planer, straight out of the package with best grain orientation I leave my parts 1/32" over, add a week or two use to the knives....I go 1/16" over and grind it out on the wide belt. Average kitchen, adds maybe 2 hours total, saves me and the finisher countless hours on pant grade maple, owner doesn't have to pay for 80" of knife sharpening every 12 days. Plus out wide belt has closer tolerances edge to edge then the old beat planer, so copes fit better. Just the way it is.

[Mel Fulks]

Big difference between sanding off 1/32 and 1/16 when you don't have a wide belt. With a wide belt any sanding before further machining dulls the tooling. In all shops one of the best ways to save time is to plan to minimize sanding. Some fast dulling might ,at times ,be wise in a commercial shop. Wide belt is best used as sander not abrasive planer. But the main thing is few home shops have a wide belt and the owners will not learn what planing option works best as long as products are mislabeled or fraudulently labeled.

[Martin Wasner]

I send doors, paneled ends, drawer fronts, and face frames through the widebelt once on each face. It's impossible for me to make less passes. lol
Same story with drawer parts. Plane to 11/16" from 13/16" hit the first face at .658", flip and sand the second face to .625". Everything is coming out of the widebelt on 180g with the platen at 21.3 ft/min.

It's all in picking the right machine. I use the planer as much as sensible, but mine is about whipped as well, sharp knives don't stay sharp very long either.

[Peter Quinn]

I have a spiral head at home, its set up dead on left to right, has a digital height gauge that is set up dead on, I don't own a wide belt and don't need one. I can orbital sand my worst door in less time than I can sand out cross grain scratches from the wide belt. Thats in the perfect world that I share with no one, that I set up. At work I show up on a given monday to find some idiot has used the planer as a paint stripper over the weekend, or planned down 500LF of knotty hickory flooring to make door stops, or who knows what. and when that doesn't happen, there's still a pile of guys doing a heck of a lot of work every week, so knives get dull quick, we don't have a maintenance man.....they call it a time saver for a reason. I don't think taking .050" off in three passes is considered abrasive planning. Mel is right on about using good steel, the cheap stuff is no bargain. Don't buy the cheap low bid stuff, find a reputable grinder and and get real knives, its a relationship that will serve you well.

[Scott Brandstetter]

Andrew
This is a great tip that i have never seen before. Makes so much sense, seems so simple, so effective, yet my simple mind would not have come up with it. Also seems it could be used for sharpening other items as well. Thanks for sharing this. Sorry to the OP, not tryimg to change the subject


Hi Dan,I had a set of carbide tipped knives for my Dewalt planer.They were from Infinity cutting tools.The grind on mine was 45 so if your are too this is how I sharpened them.45degree table saw cut on some scrap to hold them.They should get wicked sharp.

[Dan Friedrichs]

Sorry to the OP, not tryimg to change the subject
Not at all - I have seen pics of Andrew's jig before, and I just love the elegant simplicity. And now you've all got me questioning if these new carbide knives are sharp enough, or not, so now I'm going to build Andrew's jig and buy a diamond stone :)