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Thread: Sharpening Shear Blades
12-27-2004, 08:48 PM #1
I have a 3 foot Pexto stomp shear that is in need of sharper blades. I called Roper-Whitney, which owns Pexto, and the price is about $180 plus shipping to sharpen. Anyone know of an effective way to sharpen blades in the shop? I tried sharpening by hand, but it didn't seem to make enough of a difference. I may not be sharpening them correctly or maybe they simply need to be done by machine because of wear. Any help would be appreciated.
12-27-2004, 09:10 PM #2
For that kind of sharpening I send blades out to a shop with a large wet grinder. The same people that sharpen blades for wood planers, etc.
If you can't find a local shop call a printing company and ask where they send their paper knives.
12-27-2004, 09:12 PM #3
Do you have a surface grinder available? Look in your yellow pages. Industrial knife sharpening places that do chipper knives, clipper knives, and such can often do blades like yours. I can do a set of ten foot blades if I had to, but I'm too far away to be good for you.
12-27-2004, 11:23 PM #4
Yes, good advice from the others that have posted.
Machine (Grinder) sharpened is the way to go.
Check around at other shops such as a Tool&Die shop. Since your blades are only 3 feet, it should be in the range of some surface grinders (like a 12X36) some T&D shops have machines in this range. Not like a 10 footer that would require the use of a Gockel or similar long bed (knife) grinder.
By the way Richard, what kind of kinfe grinding setup do you have? Big surface?Gockel?Hanchett?
Hope this helps.
12-27-2004, 11:38 PM #5
At one shop I worked in, we successfully sharpened a 3' shear blade in a vertical mill, using a cup wheel and a light flood coolant. As long as you duplicate the original angle on the blade, it should work fine. We held it in two angle vises to get the angle.
12-28-2004, 01:09 AM #6jfsmith Guest
I would suggest using a Bed Knife Edge Grinder, but mine is in storage for the moment.
The suggestion of calling your local printer is the best one, because every now and then these folks call me to sharpen their blades. Try CopyMax, they are willing to give out info on their contractors.
12-28-2004, 11:52 AM #7
Thanks everyone for the reply's.
Unfortunately, I don't have a surface grinder yet. It's next on the list, but I haven't found the right one for the right price. That's actually a topic for another post.
I actually have a friend in the printing business who should give me a name and number of someone to sharpen them. That should work for the time being.
I appreciate all the help.
12-28-2004, 12:51 PM #8
If you have a machine shop sharpen them on a surface grinder, just make it clear WHERE they need to be ground. Might sound as if that's just stating the obvious, but a guy near me who does sheet metal work had a local shop grind his, and they ground them on the faces instead of the edges. He then had to shim them when they were re-mounted to get the proper clearance. Have you checked to see if they're reversible? On a lot of shears you can reverse them, and then later turn them over, and finally reverse them again, giving a total of 4 cutting edges.
12-28-2004, 02:19 PM #9
I've only sharpened about 300 sets of shear knives; from those fitting hobby shop shears to 16 ft plate shears. You have to shim and tweak to acheive the clearance regardless. Shear knives wear considerably on the face, particularly when shearing scaly material. You get better life out of your knives if the sharpening shop first grinds the faces to clean up then the edges.
12-28-2004, 03:25 PM #10If you have a machine shop sharpen them on a surface grinder, just make it clear WHERE they need to be ground. Might sound as if that's just stating the obvious, but a guy near me who does sheet metal work had a local shop grind his, and they ground them on the faces instead of the edges
12-28-2004, 03:52 PM #11
I agree you'd grind the faces if they're scored, but these weren't. He does only light gage stuff in CR, Al, and SS sheet. I had made some parts for him, and he mentioned when I was at his shop that the shear was leaving a burr on the edge of the CR and SS. The blades had the rounded off corner typical of a dull blade but were not scored whatsoever. The shop that ground them did 100% of the grinding on the faces until the corner was restored, and never touched the edges. I'm reasonably sure I know where the responsibility lays for this screw-up, or I'd never have mentioned it in the first place.
Added: The shop that did this grinding is well known in the area for letting guys who don't know much of anything about anything learn on other people's stuff. I figured it was worth mentioning since there's shops like that to be found most anywhere you go.
12-28-2004, 04:44 PM #12
i understand what ya mean now that you say they only ground that face, had they ground both then that would be considered proper, but as you say yes they screwed up big time!