Originally Posted by wanna be
It sounds like trooper is a sharpening guru.That is a skill that is usefull both in and out of the kitchen.Thanks for the info I will give it a try.Do you have any tips on sharpening lawnmower blades?
LOL, thanks - For the cost of having a mower blade professionaly done (I think they charge seven dollars at the knife shop here) - My time is not worth dealing with built-up grass, grime and grit to deal with it... But I have done it. (How else would I know it sucks that bad?!)
If you have a vice, it is your best friend. Remove the blade, clean it up and secure it in the vice. You will have three challenges:
1. Is the blade warped? If so: Buy new blade.
2. Does the blade have chips, dings and bent cutting-edges? Yes, it does.
3. Has some other idiot tried to sharpen this before? I hope not.
Given the first challenge is not a problem, you're in good shape.
Given the third challenge is not a problem, you're in GREAT shape!
Chips, dings, dents and rolled cutting surface... That is the first thing you have to tackle, and you WANT to fix this stuff while the blade is still "dull".
You have three options to remove big gouges and nicks:
1. Grinder/Grinding wheel - More likely overkill and may detemper your blade.
2. Belt sander - if you're really good and it has a low speed... but overkill.
3. Dremel tool and a Bastard File (dremel optional) - Best option.
If you use a dremel, just be very, very ginger, and only take out the bigger nicks and burls... in short passes, not sustained grinding. The dremel surface area will limit detempering risk, but it is still a risk. You also have to be careful not to remove too much metal - just less than what you need - finish the rest with a file.
Next, take the back of an axe or some other heavy steel tool, and basicly "steel" the blades, following the same method you would use for a knife, but using a little more force. This will really make a big difference in the next step...
Use your file, and as gentle as baby's breath, lead-into the cutting edge, following the origional angle as closely as you possibly can... and do both sides of the blade.
Next, just as gentle, use your file on the non-ground side of the blade, and file out-ward and away on an extreme (almost flat with the back side of the blade surface) angle. This will push-out the stragglers you didn't get when you did the steeling, and any metal edge rolled-back from the initial cutting-edge filing.
You will find that there are spots that may need a little more work than others along the blade... this means more work, not more force... just more passes.
After this is done, steel the blades again and you're ready for testing...
Testing the redneck way: Take a loose pipe, wrench handle or something else round and pipe-like, maybe a broom handle - and put it in your vice.
Put your "propeller" on that and spin it *normal safety disclaimer*
It won't be perfect, but you will be able to tell if it is really out of balance, or just a sloppy mower blade spinning around a stick. If it seems close enough, remount it. If it is really out-of-whack - You can file some metal off the "heavier side", but don't get too anal over it... File metal of the outer, trailing edge of the blade... for obvious reasons.
Retest and then mount back when you are comfortable with the work.
Tips: Your blade cut fine the first, second and tenth time it hit that rock, sprinkler head, driveway, dog toy... some nicks and gouges are fine - they happen. Don't take a set of channel-locks to the blade and try bending back a 3/4" roll... all you'll do is warp the approach angle of the blade... making further effort meaningless.
What you are looking for in the finished edge is a nice, even, consistant "shiny edge" across the cutting surface, that says "I did an nice, even, minimalist but clean job of following the factory angle and cleaning up the leading edge." Finesse, not brute force filing/grinding.
If you wanted to geek-out on it and use finer files, or a stone, or 0.3 micron grit and a dremel buffer... think about how much that's really going to mater the first 11 seconds that mower comes back to life. Just clean up the edge, smooth, straight, aligned, even, honed back to serviceable condition. Overkill sharpening will just make the blade dull faster, and give you less resharpen cycles before it's just plain spent.
I hope that ad-hoc how-to helps!