Getting Jointer Blades Ground Straight

[Hans Braul]

I live in a small town and have gone to two different people who were recommended for sharpening. In both cases, my jointer blades came back seriously out of true. There is at least 20 thou curvature from middle to end of the blade. I assume the problem is that these guys are using equipment that is just not up to the job. What equipment is typically used to do this properly? Have others had the same experience?

Hans

[Keith July]

Hans,
My knife grinder runs on rails that are set parallel to the knife which is clamped in a fixed position. With this set up I think it would be difficult to leave it high in the center. If the knives were not set parallel to the grinding head (in my machine) it would grind a taper. I would see a problem right away because the grinder would only grind on the high end of the knives.
My grinder will hold 3 knives in line so I can grind all three knives at the same time. Removing the same amount from each knife.
It sounds like the first guy ground your knives wrong and the second person just copied the first.
Is there a local machine shop that could help?
How many jointer knives?
Are they all ground the same way?
Hope this helps
Keith

[Rick Lizek]

My first question is did you ask the people who sharpened the blades why this is happening? A long time ago we had this problem and the guys in the shop would just complain among themselves about this. I had no problem setting the knives with a little extra work flexing a .020" bow out. The answer was steel is like wood and after so many sharpens it can release tension and bow. Once I asked my sharpening guys to make sure the knives are straight all bowing stopped. What they do is straighten the back edge and regrind the knife edge. Apparently no one was complaining so they didn't check them for straightness and do the extra step. Now all jointer and planer blades have a note on the blade case to check for straightness. Problem solved!!!
So I supsect you may have the same situation happening. It's really difficult to frind a crown on a blade. There's more than one system of knife grinders out there. My grinding shop does all three at once in a row. The machine can actually do 10' paper knives. The knives are held in place with a powerful magnet. It would do you well to ask for the nickel tour of their facilty and ask questions. You will learn things and they might inprove their customer service at the same time.

[Dave Richards]

I haven't done this but my brother has his jointer knives sharpened while in the head. He removes the head knives and all and takes the entire assembly in to someone who can sharpen then in situ. He has no problem with knives being ground at an angle and the knives are all ground to the same height. He uses the time while the head is out--a day or two for him--to give the jointer a good cleaning. When he gets the head back, it just drops in. He resets the tables and he's off and running.

[Cliff Rohrabacher]

Unless they have a water cooled surface grinder or machine designed just for the task you are going to the wrong people.

The .020" is it a crescent shape? The middle of the blade the thinnest? That could be from heat buildup causing the metal to swell.

A dry surface grinder can do the job but the machinist has to know not to take a pass greater than half a thousandth at a time.

Professional smurfessional give me a real tradesman any day.

[Hans Braul]

Here is picture, best I could take, of the blade resting against the back of another blade, which is flat. The amount of crown is considerable, and all three are about the same. I also had my 10" planer blades done, and they are also crowned. I actually talked to the guy about how the first guy didn't grind them straight, and he said he'd take care of it. I just think he's probably using the wrong equipment. They are hollow ground, so I'm not sure what kind of jig he's got, but it clearly isn't stable. The blades are perfectly flat. This is only the second time they've been sharpened since I bought the jointer.

Any comments welcome.

Hans

[Sam Chambers]

Hans, I'd take them back to the guy, show him the problem, and ask him to either sharpen them correctly or refund your money.

[Phil Thien]

Hans, I'd take them back to the guy, show him the problem, and ask him to either sharpen them correctly or refund your money.

I'd go one further and take the blades back and demand a refund after showing him the problem. I wouldn't let this guy near your blades again! He is just wasting HSS.

BTW, I do not suggest hollow grinding for jointer/planer blades.

I don't know what you paid this guy, but you can get a water-cooled sharpening system from Woodcraft for $100, plus another $30 for a long-knife jig. And then you can do it yourself and always get them as perfect as you want 'em. After several sharpenings it will pay for itself. And you might find you sharpen more often if it is available to you.

Gosh those are bad.

[Bruce Wrenn]

Another option is Dynamic saw in Buffalo NY. Check out their web site www.Dynamicsaw.com . We have been very happy with their work. Forrest will also gring them for you ( probably using same type machines) for THREE times as much. But then you could say that Forrest did your sharpening.

[Eddie Darby]

Have you considered doing the job yourself?

I have a machinists granite surface plate Grade "B" that is +/- 0.0001" from flat, and I have this jig that Lee Valley Tools sells.

http://www.leevalley.com/wood/page.aspx?c=2&p=33002&cat=1,43072,43078

I use wet/dry silicon carbide paper for the rough stages, 120x to 600x and then I use the micro-abrasive sheets from Lee Valley in the 15 micron, 5 micron, and 0.5 micron sizes for the refining and honing stages. I just use water to hold the sheets in place on the granite surface plate. I can do the backside of the blade as well, which is very important if you want a real sharp edge! This is far sharper than any sharpening service will do. I own 2 sets of knives, so that I don't have to sharpen the blades right away.
I like to try and keep all my knives the same so I count the number of strokes I do on each grit, and dupilcate that for the other 2 blades. If I do have any complaints, I don't have far to go to lodge them! :-)

[Byron Trantham]

I own the Tormek system. It's expensive - period. I took a big gulp when I bought this machine about two years ago. I used the planer/jointer jig for the first time last week. I sharpened DeWalt 12" planer blades for my brother-in-law. The deal was $20 if I was successful and $0 if I wasn't. The jig worked as advertised. They are sharp and straight; no convex or concave edges. I personally have 13" DeWalt planer blades and 6" jointer blades. Each set costs about $50. As you can see, not many sharpening begin to make the investment worth it. BTW I sharpen knives and scissors for other people and to date I have recouped about 65% of the TOTAL investment.