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Ian B
06-28-2011, 10:22 AM
I use my Boxford Union tool & cutter grinder to resharpen the blades from my 10" wood planer - the t&c grinder has *just* enough table travel.

I've made a jig that bolts to the table to hold the blade at the correct angle for sharpening. I can arrange the setup to grind onto the edge, using a cup wheel, or along the edge using the periphery of a wheel.

Onto the edge, or along it - pros & cons, does it make any difference?

Thanks,

Ian

aboard_epsilon
06-28-2011, 11:59 AM
Well Ive used my grinder along the edge .got rid of the burrs ..touched them up with an oil stone...i could slice phone books with them and shave myself ..plonked them in the planer ..10 mins later there are little cresents missing from the edge...no nails in the wood.

so i say do the opposite and and grind at 90 degrees to the edge ..and see what happens.

cause my way isn't working

all the best.markj

Swarf&Sparks
06-28-2011, 12:22 PM
my experience FWIW

always grind "towards" the blade/knife

this applies to my little tormek wet grinder or the beast I used at a mate's business which used to do printers' guillotine knives and metal shears up to 12' long (12', no typo)

in the case of the tormek, I'm manually traversing the tool across the wet stone, giving a hollow grind, but always "der scratches goes in line with der cutting" whether for timber or metal

the abovementioned monster grinder traversed a bloody great 3PH induction motor grinder head along the ways, shaving whatever was held in the bed, adjusted to the correct angle, of course

the main thing is, the grinder head held segment stones and could be tilt adjusted to provide a very slight hollow grind on the edge of paper guillotines or a nearly square edge if you wanna crop 2" steel plate

I think what I'm trying to say here is, use the cup stone and cut towards the "body" of the blade with a very slight hollow if your TCG will accomodate that

hope I have understood your question

slainte, Lin

macona
06-28-2011, 01:20 PM
There are companies locally that do this professionally and often the cost to sharpen a set of planer blades is so cheap its not worth risking messing them up.

Forrest Addy
06-28-2011, 03:04 PM
I have several sets of wood planer knives. When a few get dull I take them oul to Kukenbaker Sharpening service on Half Mile Road. Cost me about $30 to get two sets ground and in that time get to BS with a few local woodbutchers, look at his kid's rabbits, pet the cats, and eat a cookie. Hell of a deal.

The knives come out straight and sharp equal weight and while I'm there order a new set (he can still get the good M2 knives) to replace a set I notice are getting narrow. Nice way to spend a couple of hours..

I'd do about anything to avoid sharpening planer and jointer knives especially if it's pleasant at the place of avoidance.

Evan
06-28-2011, 03:52 PM
Make sure you balance the blades in pairs to within half a gram or better. My wife does that in her shop for all the blades she sells and it makes a big difference to the finish and life of the blades.

Duffy
06-28-2011, 06:06 PM
I have a 12" planer with a two-blade head. I made a "jig" from a length of 2x4 and use a 6"x80" belt sander. Obviously, the blades are ground parallel to the length. I finish on a hard Arkansas to remove any wire edge. In my (limited,)experience, I find that I have to grind each blade about the same amount to remove any oops left by stray staples or fine nails, so they maintain (reasonably) equal weight.
I also learned that the "off-shore" blades are laminated, with a very thin HSS insert on the edge. They work as well as solid HSS blades, so I guess it is an "oriental economy" thing, rather than a safety issue. (Think how exciting it would be when one of those blades shattered!)
If the blades are not giving decent service, it MIGHT be too-shallow a bevel angle.

Black_Moons
06-28-2011, 07:01 PM
yea if they are chiping, id suspect bevel angle is too shallow.

I made a machette and after my friend sharpened it, it was getting huge nicks in the blade. I sharpened it again with a really steep bevel angle, just about 1~2mm deep on the tip of the blade, And now it seems just as sharp, but hardly gets a scratch from hiting rocks.

(Got the idea from the "Micro bevel" stuff they talk about in my lee vally catalog. Put a 2nd bevel on the blade, a few degrees steeper, and its MUCH easyer to sharpen/hone and much stronger if the new bevel is a few degrees blunter, Without losing much chip clearance on the blade or having to greatly alter its profile to try it out.

DATo
06-28-2011, 07:27 PM
I made a planer blade grinding fixture some years ago for our small planer at work. You use the fixture to sharpen the blades on a surface grinder. I'll bring the camera in tomorrow and take a few picts of it and post them tomorrow night.

EDIT: JoeLee beat me to it. *LOL* Beautiful job Joe. Mine sharpens all three at the same time but is not nearly as elegant as yours. I was going to post mine but I can't find the dang thing though. We do so little wood work that the blades get sharpened about once every ten years. *LOL*

darryl
06-28-2011, 09:38 PM
I had our planer apart a couple months ago. Didn't even think twice about sharpening them myself- just wrapped them up and sent them out. Putting the blades back in properly was challenge enough.

Today I had our dovetail machine apart for some TLC and alignment of the guides. The machine has an issue with one of the air cylinders sticking. At one point it kind of got out of cycle and let the cutter drag past a metal tang. I don't even want to know how much it will cost to replace the diamond-faced cutter-

Lew Hartswick
06-28-2011, 10:03 PM
Here is a fixture I made about 10 or more years ago to use on a surface grinder. I do the edges the long way.

http://home.earthlink.net/~lhartswick/planer-jig.jpg

...lew...

john hobdeclipe
06-28-2011, 10:38 PM
I don't think it really makes any difference. All of the knives I've seen sharpened by a specialty sharpening shop have been flat ground using a cup wheel. And all of the straight knife sharpeners that I'm aware of use cup wheels. But most industrial size planers that are equipped with knife grinders to sharpen the blades in situ grind on the periphery of the wheel (hollow grind.)


Well Ive used my grinder along the edge .got rid of the burrs ..touched them up with an oil stone...i could slice phone books with them and shave myself ..plonked them in the planer ..10 mins later there are little cresents missing from the edge...no nails in the wood.

You're getting the knives TOO sharp...you don't want them to be like razor blades. You want as much steel backing up the edge as possible without the knife healing or burning as dirt and pitch accumulate behind the edge . Grind them so that when they are in the cutterhead and contacting the wood you only have about 15 to 20 degrees of clearance.

Remember that power woodworking knives scrape more so than cut.

JoeLee
06-28-2011, 11:05 PM
Here are a couple pics of the planer and jointer sharpening fixtures I made. I never tried sharpening into the edge with a cup wheel. I always did them linear. The flash that ends up on the cutting edge is very minimal, I would compare it to gold leaf. A light touch up on the oli stone is all thats needed after grinding.

JL................

http://i911.photobucket.com/albums/ac317/JoeLee09/Planer%20and%20Jointer%20Jigs/Image006.jpg
http://i911.photobucket.com/albums/ac317/JoeLee09/Planer%20and%20Jointer%20Jigs/Image007.jpg
http://i911.photobucket.com/albums/ac317/JoeLee09/Planer%20and%20Jointer%20Jigs/Image004.jpg
http://i911.photobucket.com/albums/ac317/JoeLee09/Planer%20and%20Jointer%20Jigs/Image005.jpg

Ian B
06-29-2011, 02:15 AM
Thanks for the repies so far. There seem to be 4 camps here:

1. Grind onto the edge. This should give the least burrs.
2. Grind off the edge - looks like it'll create burrs, but this is how most T&C grinders would work, when sharpening the edges of (say) endmills with the tooth resting on a finger.
3. Grind along the blade, as you have to do with long blades being sharpened on a surface grinder.
4. Hand the blades to someone else, let them do the sharpening.

Leaving the last method aside (this is a hobby to me, and I don't mind sharpening my own blades), back to the original question, which I suppose will apply to producing a sharp edge on anything - is there an optimum direction of grinding?

I know about grinding a centrepunch - lengthwise, not around & around, or the point will drop off - or so I'm lead to believe. Does the same not happen when grinding along the length, as with Joe Lee's beautiful jigs?

I've been grinding the planer blades at 45 degrees - not sure how much clearance this gives, as I haven't measured the rake. I just followed what the manufacturer had done. Blade life seems ok - nails permitting. I've also been grinding onto the edge, as this is how my jig's set up.

Ian

Davo J
06-29-2011, 02:37 AM
Hi Ian,
I have a small blade grinder for my 3inch electric wood work planers that I bought years ago. It is a type that you clamp the planer in and uses the planer belt to run the wheel which is a small cup wheel that grinds towards the blade.
I have also used this to sharpen my 500mm thicknesser blades and it seems to have worked fine from the results I am getting.

Dave

Ian B
06-29-2011, 03:14 AM
Dave,

Sounds like this sharpens the blades when they're still mounted in the planer knife block - this sounds like a very attractive idea, as there's then presumably no need to mess around with height gauges to reset the blades.

I saw an 18" Wadkin thicknesser for sale, that mentioned it came with it's own built-in blade sharpener - maybe this was the same idea?

Ian

form_change
06-29-2011, 06:51 AM
Many years ago when I was interested in ornamental rope work, I went to see a sail training ship being rigged. Speaking to the head rigger (old guy, out of retirement for "one last ship") he told me that for that sort of work, sharpening a knife blade with a coarse stone or linisher (sandpaper) would effectively put micro serrations on the blade, which would help cut fiberous things like rope.
Based on that I'm wondering whether it is therefore better to grind planer blades and similar across (that is, perpendicular to length) the blade. Grinding along the blade would effectively put microscopic score marks along the blade and weaken the cutting edge.

Maybe...
Michael

Davo J
06-29-2011, 06:51 AM
Hi Ian,
This one I have you take the blades out and put them onto a block and slide it back and forth in a V grove set at the right angle. The machine clamps onto the base and just powers the grinding spindle by belt drive.

I just did a bit of a search and found one like mine.
http://www.justtools.com.au/prod1697.htm

It is not the right tool for my larger 15 inch blades, but I thought I would try, and being careful it worked. I have only done the blades once and they had never been sharpened before, but they seem to be working fine.

I would be interested in seeing the sharpener that you don't have to remove the blades, because as you say it's a pain setting them all back up again.
My machine came with a blade gauge for setting them up, it is just 2 arches with a flat in the centre of the arch for blade height and a round bar joining them together.
A picture of it is in the manual below (1.4mb)
http://cdn0.grizzly.com/manuals/g0453p_m.pdf

I didn't mind doing this time because it was a new ex demo model that needed completely setting up properly. I even had to move the the chain along a tooth on one of the raising and lowering sprockets because it was going up on an angle.


Dave

JoeLee
06-29-2011, 08:30 AM
Another thought would be to set the fixture diagonally across the magnetic chuck and that would give you somewhat of a grind into the cutting edge.

JL.....................

Ian B
06-29-2011, 08:45 AM
Dave,

I'm not sure if the Wadkin thicknesser with the built-in grinder necessitated removing the blades - but you'd think some kind of 'grind in place' setup would be both possible and desirable. Some kind of indexing on the cutter block, and a bolt-on track for a grinding head to slide across. If used on a planer / thicknesser, adjust depth of cut with the table height fine adjuster.

Michael,

A more extreme version of what you're saying is a serrated knife, like a steak knife. The explanation that I heard (and liked) for having the serrations was that when the knife edge rubs on the plate, the points go blunt, but the edge between serrations stays sharp - it only contacts meat, not porcelain.

It may be the same for knives sharpened with a coarse stone.

Joe,

Yes, it sounds as if a diagonal grind would reduce the fine bur that a parallel grind gives - and even allow you to grind a 19" blade on an 18x6 grinder.

Ian

bborr01
06-29-2011, 10:30 AM
One day I was out cutting the grass and thinking about making a fixture to sharpen the knives for a Dewalt planer that I had just purchased used with dull knives.

Then it hit me. Why not check with a local sharpening shop and see if it is worth my time. It wasn't. They charged me about $11.00 US to sharpen a pair of 12.5 inch knives. They quoted me a price of .45 cents per inch.

I told them that one of the knives had a slight bend near one end and they told me the magnet that they hold it down with would probably pull it flat.

Ding... A LIGHT WENT OFF INSIDE MY BRAIN AND I ASKED MYSELF WHY WOULD I WANT TO MAKE A FIXTURE WHEN I COULD JUST DRESS THE ANGLE ON THE WHEEL.

They went on to tell me that they do indeed use a magnetic chuck to hold the knives but use a cup wheel to grind them. They said you don't want to have the grinding wheel running parallel too the knives. The cup wheel cut perpendicular to the knives.

The did a fine job of sharpening both sets and it was cheap compared to the time I would spend getting a lesser quality sharpening.

My 2 cents worth.

Brian

mike os
06-29-2011, 11:16 AM
sharpening direction should not make that big a difference other than to ultimate sharpness, which is not really an issue for teh application.

the important thing is that the angle is correct, and that the blades are balanced.

Some woods are hard/abrasive enough to take the edge off /chip anyway;)

Ian B
06-29-2011, 03:53 PM
Blade grinding in-situ - have a look at http://cgi.ebay.co.uk/Wadkin-BT500-Thicknesser-planer-blade-grinder-/150624867259?pt=UK_BOI_Building_Materials_Supplies _Carpentry_Woodwork_ET&hash=item2311f113bb

Scroll down the pics, is that thing with the small blue motor and 2 guide rods there to grind the blades without removing them? Doesn't look beyond the average HSM'ers ability to copy such a design...

Ian

Duffy
06-29-2011, 07:38 PM
You know, we just LOVE to solve problems, especially the ones that dont exist! Take a moment and analyse the problem. A commercial planer surfacing wood straight from the log, at speeds that would make you blink, gets AT LEAST one shift between blade changeout. I run anything, (salvaged, painted, weathered,) through mine and I dont suppose that I change blades twice a year. As far as sharpening my own, here it costs about $1.00/inch, AND a 50 km round trip TWICE, (delivery and pickup,) so with lots of spare time, I sharpen my own. I cant really see spending the time and effort to build an in situ sharpener. After all, EVENYTUALLY, the blades have to come out. It might be better to build/modify your grinder to handle EVERYTHING that you own with a cutting edge.
By the way, Some people consider Wadkin the Rolls Royce of woodworking machinery. Here in the Colonies we find that the only drawback is that there is a Union Jack stamped on the machine somewhere, and that means that parts are either unavailable and/or use "funny fasteners" if and when you get them.:D