We have gone to using Dispoz-a-blade disposable blades.They come in HSS or cobalt.They are double edged.Cost is no more per edge than sending them out to be ground.The real savings is that they take only 10 or 15 minutes to install.We don't have nearly the time tied up in using these blades.You have to bite the bullet to buy the knife holders,a few hundred dollars,but it's smooth sailing after that.The blades just snap in place.
Here's the fixture I made to grind mine. All of my machines have 45deg edges and as such it fits well in a mag vee block. This closely emulates how they were made and how knives are held in cutter heads (wedges) so I felt it best to duplicate the holding method. The wheel is cupped as normal for sidewheeling and the guys above have covered wheel selection. This is what was in the post that stephen thomas linked above.....I didn't think anybody would drag it out of the abyss so I had broken the pic link. Here it is again round 2! [img]smile.gif[/img]
Make sure to block the output end.
cmiller231, that would work on a surface grinder safely and I have done some things that way. You are traping the work between stop blocks and the whole mass is held to the table. I would not do that on a Blanchard because of the rotational load effects on the blades. If it worked for you that is fine. On the other hand I never had anything break through the side shields on the Blanchard even though many things flew off for various reasons. Mostly my fault.
bluechip, those laminated V blocks are what I was talking about. We had laminated V blocks and parallels. They are very handy to have.
Picking up on what Carl said, those laminated parallels are cheap enough these days to just get a few, mill them, and match grind them against the chuck rail to the same angle, with a ledge for the bottom of the blade(s) to register. I have a few parallels that I have milled to various angles for different tools that repeat. Sometimes the import parallels are quite cheap and you don't feel any guilt in cutting them up to suit a job.
No Good Guys...He said no coolant.
The image shown works OK with coolant, but sitting up there like it is does not suck off the heat. You need to support the blade as close to the sharp edge as possible to get the heat load down.
I would use 32A46-J8VBE and lots of coolant. Could use 60 grit also but more chance of burning.
2: 46H-60H (hard metal, soft wheel, soft metal, hard wheel)
3: Fixture the workpeice at the proper angle, keep the wheel dressed square.
Don't worry too much, HSS can take a good bit of heat and not loose it's temper. Just be careful such a large workpeice does not deform under heat. A good supply of compressed air to keep the workpeice cool will go a long way. Take your time, coolant for this type of work is ideal but not required if you can substitute patience for water [img]smile.gif[/img]
bluechip, are you using a cup wheel or dressing a standard wheel for side grinding? You can also flip that fixture the other way 'round and grind it with the face of the wheel too, of course. Might actually be a better option as far as workpeice heating since you can step into it rather than take a full profile cut every pass.
Years ago, I remember spending hours & days grinding granulator blades, on a big Norton Grinder. Dress, make 2 .002 passes, dress again... & to top it off, the blades had to be match ground.. Much cheaper to send them out to a shop with a knife grinder.. They charge something like a dollar per inch..
Davis, please don't remind me of those days, please!!!!
Can't we just do the proper thing and send the ungrandulated scrap to China and let them deal with it??? (tounge in cheek, of corse).
Endless, doldrums hours of time spent babysitting a Blanchard grinder watching cutter blanks spin around, and around, and around, and around, and around. Then there was the always exciting hand dressing of the blanchard wheel with a bing ass stone. Yeah, now THAT was scary!!!
I was going to jump in on this a couple days ago. THOUGHT someone would say you NEVER grind wood planer blades lengthwise.
Planer blades are ground hollow, that means if you have a 12 inch blade you have to have a 12 or more inch crossfeed, or you have to have another feed system.
IF you grind the length of the blade, you create microfractrures in the cutting edge. The sharpest part will just crack off.
My own Rockwell Delta,18 inch, I have an on the machine grinder. Not cheap. Mine was 800 bucks. STONES are still ridiculous.
Only way to guarantee flat and parallel. Grind in situ. And THEN, only if you have done the alignmaent properly. Set up the machine,set up the grinder. If all is well, grind the blades. They will all be the same circunference. That is how you get a surface planer to make a smooth board.
nothing wrong with your way. I, too prefer slightly hollow ground, but not for the reason you state. My preference is because hollow grind makes it easy to hand hone them. A knife grinder uses a cup wheel, and the wheel can be slightly inclined in the direction fo travel. So the knives can be ground dead flat, or, or the head twisted and they can be gorund to various amounts of hollow grind.
As far as which direction to sharpen, it is irrelevent to most commercial woodwork. Either the knife will be hand honed prior or during installation; or they will be jointed. Either way takes of the edge score that bothers you from parallel grinding.
As someone else posted, the strongest knives tend to have 2 bevels, and the primary is not hollow. As you noted, the ideal is if the microscopic score marks from the grinder are perpendicular, rather than parallel, to the edge.
But again, on well ground knives that are honed or jointed, it doesn't matter a whit after installation.
The biggest factor is using whatever equipment is used, in a method that yields good straight knives.
Well, this is not answer to the question, but I'll throw it in anyway. I use a Makita wet horizontal wheel grinder to sharpen planer blades. I've never seen any commercially sharpened blades come out as nicely sharpened as I can do on the Makita. It give what I would describe as a fast waterstone finish.
I was thinking about using an old 16 x 40 inch lathe I have as a planer and jointer knife sharpener.
The easiest way would be to mount a grinding wheel on a length of all-thread and mount it between two centers on the lathe, and turn it with a lathe dog. Then, I could build a fixture to attach to the compound rest to hold the blades. It would be a hollow grind, but I could use a relatively large diameter wheel and spin it slowly using a mist coolant. I've been disappointed with local sharpening services, and I'm determined to start sharpening my own. Are there any major problems with this setup ?
Is your planer a Powematic, or other than accepts a grinder and bar?
If it is,(and you use it alot) I would highly recommend getting a grinder and bar for it. I agree w/ George about grinding them in the head. It is MUCH faster, MUCH more accurate, and your a lot less apt to slice your hands on the fresh knives while tighening the gib screws. WE have 2 powermatics- 1 with and 1 without the grinder. Guess which one stays sharp? The others, and jointer knives, are ground on a ancient but super nice Yates American straight knife grinder which does a fantastic job. The trouble is in setting the knives, and, of course, having to remove them in the first place.
I bought a jointer stone for the 24" powermatic, but used it only 1 time. I hit the knives w/ a diamond hone after grinding in the head.
william462 Sounds like a lot of work to make it work properly. might be easier to find an old surface grinder or check into that makita grinder that was mentioned earlier.when i do it on surface grinder i only take .0002 -.0004 max per pass. of course i don,t have coolant so i put a coating of spindle oil on them after every pass.i use a 32a46-gvbep norton. i grind it fast like grinding a mag in. my .o2 cents chris
Born 2l8 I have a PM 100 that has a grinder attach.Machine has been used very little. have never used it because i don't like the down feed screw it looks like it has a lot of lash.Do you know what grit and hardness wheel is on grinder? then the grinding wheel will not traverse all the way off the end of the cutter head.thismach has the quiet head with all the pita blades chris
there are a lot of posts on this thread, and I didnt read any of them, except the first one
I have been sharpening woodworking tools for over a decade
YOU CANNOT SHARPEN PLANER KNIVES WITHOUT USING COOLANT
you will fry your blades.
If you fixture them properly, you can certainly do them on your surface grinder, but you MUST use coolant.
I'm sorry to disagree with you my friend. I have been regrinding planer/jointer knives 24 years and never once used any coolant, misting method or lubricant.
YOU CANNOT SHARPEN PLANER KNIVES WITHOUT USING COOLANT
On an average setup for one of our(son &I)new home projects (1 or 2 a year)running between 15k to 35k board feet per home the planer/jointer knives get a regrind after about 1.5k feet. What this means is a lot of grinding and 20/30 blade grinds in a few weeks. That's about 50/60 knives in both high carbon and HSS. We could run them longer before new grinds but this is what I allow for knife/grind TOS.
Perhaps to some people coolant may seem an absolute necessity for a regrind but I have had excellent results with my methods that do not use any. Our smallest knives start at 4"Lx1/8" with the largest ones at 20"Lx3/8"
I hope what I said didn't come on to strong as it's not meant to.
Never say never.....
I've been using the rig I pictured above and dry sidewheel grinding those HSS knives for 12" planer and 4" jointer for quite a few years....they ain't exactly fell apart, failed, lost their edge excessively fast. Now I don't run fence posts with barbwire thru my planer either, so no big nicks, I get them out of there before I have to put them on the grinder and plow 1/8" off the knife. Perhaps ignorance is bliss.....