Tersa Carbide Knives

[Patrick Kane]

Whelp, second edge of my HSS knives in my jointer are certainly passed their prime. Its to the point where i get burns on the wood if i pause for a second to readjust my grip. From the last year or so of reading threads about M+ versus Chrome versus Carbide, it seems like the carbide owners are very pleased with their investment. These knives are going in a generic italian 500mm jointer with a 4 knife head, and i almost exclusively process rough lumber. Unless the material was sawn skinny, i almost always plane both faces, so im not particularly concerned about the highest and best cut quality off the jointer. I just want my buck to go the farthest on my knives. I care more about the ease of feeding material and the ROI on my money for the next couple years than i do about glassy perfection off the jointer. That brings us to the cost comparison. M+ is about $16 per 500mm knife compared to freaking $123 per carbide knife. In other words, i can have about 16 fresh M+ edges compared to 2 carbide edges for the same price. Im sure carbide will outlast those M+ edges, but it might be 5-6 years before i reach the break point. I process maybe 2500-3500 bdft a year, and most likely see that number going down and down as the years go by(family time). My final question is, can i go down to two knives in a 4 knife tersa head? No matter what knife material i go with, i think i want to go down to two knives instead of four. for carbide, this is especially important because its $250 versus $500. I believe ive read people reducing knives in the cutterhead or running 'dummy' knives. One,can you simply remove the knife and run the head without the gibs flying out of the head? 2 knives is less feeding pressure than 4, correct? Not sure why they went with 4, i think the martin 54 had two knives for awhile.

[Brian Holcombe]

M+ are lousy in my experience, I disliked them greatly. Carbide are great, I have two sets one for the majority of my work and one super sharp set that I use for finish passes on tearout prone material. Once they degrade slightly they will become my everyday set and a new set will replace the role of the super sharp set.

I went through a TON of M+ knives before finally deciding to just go carbide.

I was advised against having them sharpened by Tersa Knives.com but not sure I will heed their advice.

I run 4 carbide knives.

[David Zaret]

i run carbides in both of my tersa machines - 4 knives in the planer, and 2 knives with two blanks in the jointer. yes, they are very expensive - the planer set was $600+. that said, i won't go back - i keep HSS on hand for nasty, dirty stuff, but otherwise i run the carbides. with the jointer, looking back, i regret running 2 knives vs. 4. the 4 just gives a far superior edge - the 2 works, and practically it's probably just fine, because i don't go to the finishing room from the jointer, but still, i think next time i'll put all 4 on. again - for flattening and straightening, two knives works - but the cut quality just isn't as good.

for sharpening, the guys at Unimerco (Kyocera) in Saline, MI do an excellent job with carbide tersa knives. i've toured the facility, and seen the grinder they use... it's massive. i think they poured a separate footing for just that machine - it's pretty impressive. every time they sharpen my carbides, they come back noticeably better than new.

good luck,

-- dz

[Jim Becker]

I haven't used the carbide Tersa knives yet, but am seriously considering it as I'm on my last set of HHS.

David, it's interesting that you've been able to get them sharpened...hmmm...

[Erik Loza]

Ditto: Had no idea they (or any alloy) could be sharpened. Out of curiosity, anyone tried the Kanefusa coated knives? They were supposed to be the magic bullet. I no longer use Tersa on the regular.

Erik

[Mel Fulks]

I find 4 knife to be tediously slow,I like the two knife for those heads. I would use the dummy knives for less distortion
of the head. Always been happy with M2 or T1. Orders for M2 are often filled with "semi high speed steel". When you ask
vendor about that they say they are "same hardness". Lousy stuff.
I've eaten biscuits that were hard as bricks...but at least they were real biscuits! I hope you will try T-1 before going with
carbide ,they don't dare substitute that with junk.

[Patrick Kane]

Help me out, Mel, what is T1? Im seeing HSS, Chrome, M42/M+, and finally Carbide.

$500 for four knives is probably no can do for me. Not to say they arent worth it, i just dont know if i will reap the benefits long enough. Heck, I dont even know if i will have this machine 5 years from now, let alone planning for using the knives for a decade. Unlike insert heads, these are 2 carbide edges instead of 4, which makes the value comparison a lot thinner.

[peter gagliardi]

If finish quality over the long term is less important than knife life, you should definitely be running 2 knives instead of 4. Every single person I know running the Tersa M steel says they are terrible. I run Terminus, and they are ok, but I would like longer life between changes as well. I can get aftermarket in T1 usually. I also use a diamond coated steel to hone them a couple times between changes.
It can be hard to justify the carbide...

[Mel Fulks]

T1 has more tungsten, and is a true high speed steel . Leaves a nice finish, the low quality stuff has a lot or striations
almost right after first use.

[Joe Calhoon]

I’ve had good luck with carbide Tersa. I run 2 knives in all the heads- planer, jointer and 4 side moulder. You need to get the dummy knives if running 2 in a 4 knife head. It will be out of balance if you don’t. I am considering running 4 knives in the jointer at some point since it is hand feed just to see if less back pressure.

Quality planing and surfacing cost money no mater how you go about it. In my case running various materials, hardwoods and and knotty material carbide is the most cost effective. I believe the M42 and HSS would be OK if just running clear softwood.

I have tried Kanafusa coated in the jointer and planer. They are good, do not nick easy and for some strange reason seem to cut better after a little use. Since they cannot be resharpened I think the carbide is more cost effective. The carbide in the S4S is on its 3rd resharpening from Unimerico and they said no more possible with those.

[David Zaret]

agreed with Joe - i also tried the kanefusas, and though they were fine, given the price, and the fact that they can't be sharpened, it doesn't pencil out. i've had carbide tersas sharpened three times - and again, they come back **sharp**. for me, it's worth every penny.

to be clear - unimerco will not sharpen HSS or M+ knives. only carbides.

[Robert LaPlaca]

David, what does Unimerco charge per inch (well I guess actually centimeter) to sharpen a carbide Tersa knife?

[David Kumm]

For those who run 2 knives, do you need to order dummy knives or can you use dull old HSS tersa in two slots? Is the profile of the edge the same so you can run two types together? Dave

[David Zaret]

dave, i couldn't use HSS - the diameters didn't work out. i bought some blanks from unimerco, they were cheap.

if i recall, i paid ~$125 to sharpen four 530mm knives. i'll look at my email to find the old invoice and correct this post if i'm way off.

EDIT - the 530mm blind knives were $51 for two. sharpening the carbides was ~$42 per knife, 530mm, $167 for the set of 4.

[Joe Calhoon]

Dave,
the dummy’s are rounded but the same weight. Martin said not a good idea to run the dull knives with sharp. Don’t know why but I think some people do that.

[David Zaret]

given the price of the blanks, i don't think it's worth the risk. the carbides definitely have a different geometry than the M+, and obviously change when sharpened. i do have to adjust the outfeed table when i install new, or sharpened, carbides.

[David Kumm]

Good to know. I get about 500-700 hardwood board ft through each side of my M42 Tersa and in my world that runs a couple of years. Dave

[Robert LaPlaca]

dave, i couldn't use HSS - the diameters didn't work out. i bought some blanks from unimerco, they were cheap.

if i recall, i paid ~$125 to sharpen four 530mm knives. i'll look at my email to find the old invoice and correct this post if i'm way off.

EDIT - the 530mm blind knives were $51 for two. sharpening the carbides was ~$42 per knife, 530mm, $167 for the set of 4.

Dave, thanks..

[peter gagliardi]

Joe, 2 knives should give less feed pressure.
Since I run Terminus, I have made my own blanks for the 2 opposing slots in my 4 knife heads by just taking a dull set of the steel knives and kissing back the cutting edge on the edge sander. That may not be possible with the smaller Tersa style knife.
I have also found a good use for the old Terminus knife stock. I groove out some hardwood and glue it around the blade and make various shaped marking knives and flat chisels for hand work.

[Joe Calhoon]

Peter, I seem to remember when I first got the jointer it had 4 and was easier. Maybe I’m just getting old and weak...

Here is a picture of a carbide Tersa and a dummy. The dummy knives are inexpensive.
and a Rali scraper that takes Tersa knives. A while back I saw a Utube of a woodworker sharpening his HSS Tersa knives. I’ve kept all the old ones and may try that sometime just for kicks.

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[Larry Edgerton]

For those who run 2 knives, do you need to order dummy knives or can you use dull old HSS tersa in two slots? Is the profile of the edge the same so you can run two types together? Dave


Thats what I did Dave until I had dull carbides. I usually only change out one knife at a time, but I don't wait until they are horrible. As far as different heights, no they are not. Carbide or HSS, a piece of wood comes out the exact same thickness with either knife new, so there can be no difference. I have about 10 sets of carbide I need to send in.