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View Full Version : Putting Temper Back Into Your Blades


Canadian GreenScape
06-24-2004, 08:08 PM
I was just sharpening the blades on my gear and mentioned to my Dad (whos a welder) about not being able to keep the blades from turning blue (and taking the temper out of them as I read on here awhile ago) He said its true that heating them up to the blueish color will take the temper out but he told me how to put it back in :p He said you have to heat them up to a dark cherry color and then immediatly dip them in oil. Im thinking you'd need a torch or somthing to heat them up that much and I doubt Ill try it... but I thought it was pretty cool :D

Avery
06-24-2004, 08:15 PM
Our blades do not last long enough to go through all that trouble. We only get one sharpening out of them. By the time they are dull again the sail is worn off from all the sand here.

dvmcmrhp52
06-24-2004, 08:54 PM
If you heat too much of the blade or heat it too hot you will make the blade brittle.Unless you are experienced or have access to a heat treat oven don't do it.Grind your blades a little slower with less pressure to avoid the blueing to begin with.

Canadian GreenScape
06-24-2004, 09:22 PM
Yeah thats what Dad said too... have to take it easy with the grinder I guess.. haha

Sooners
06-24-2004, 09:49 PM
...52' is correct.

I have a degree in Metallurgy (the heat treatment of steel) and wouldn't dare consider torch heat treating a mower blade.

Everything depends on the steel the blade is made from. If you've heated it to a cherry red, it will be soft unless you quench it in oil or salt water. The rapid quench transforms the steel into a harder and more brittle structure. The steel then needs to be tempered properly to relieve the stresses induced by the quench.

I just grind a little farther back to remove the blue area if possible. I just wouldn't want a blade to crack and hurt something.

Albemarle Lawn
06-24-2004, 11:24 PM
Go easy when grinding, and sharpen more often so you don't have to try to remove as much metal in one sharpening session.

Woody82986
06-25-2004, 12:08 AM
I was just wondering if anyone sharpens their blades by hand with a file? I swap blades on my mower at the end of every day and spend about 20 minutes with a file sharpening the ones I just took off the mower and they seem to stay sharper and provide a better cut than when I use the grinder to sharpen them.

skmodmsl
06-25-2004, 12:32 AM
I have been concerned with blade temper myself. It seems that after sharpening the blades go away quickly. I have been sharpening my blades by hand with a file. It takes a long time. But it keeps the heat down.

Heating a blade to "cherry red" and cooling will restore temper. There are way to many variables to consider. I've given up on worrying. Keep the blades as sharp as possible. Let the customer be your guide.

Craig T
06-25-2004, 01:13 AM
By hand with a file? You guys must have plenty of time to mess with blades. As far as heating them up, try a belt sander. I use a 36 grit and if I want a extra nice finish I will slap a 120 on just to make them shine. I can also take 3 or 4 passes with the 36 grit and still hold the blades with my hand. Unlike the grinding wheel. If you can hand grind try one you will see what I mean.

BSDeality
06-25-2004, 01:16 AM
i sharpen my blades with a belt sander. it doesn't heat them up like the wheel grinder does, nor take off nearly as much steel.

Sooners
06-25-2004, 02:53 AM
I prefer an air powered hand sander. But hand filing every day with the damage I get from hidden rocks, forget about it.

Rather Be Fishing
06-25-2004, 04:43 AM
Originally posted by Sooners
I prefer an air powered hand sander. But hand filing every day with the damage I get from hidden rocks, forget about it.

Agreed. I'd rather "lose my temper" than hand file commercial mower blades.

19-22" push mower blades are easliy hand filed and can be done in the field in minutes rather than replacing the blade and seem to last longer/ stay sharper than blades sharpened on a grinder in my experience. A litle off-topic but I had a client give me his Black&Decker "hedgehog" electric shears after trimming his yews thinking down the road I'd be working faster. I had to explain how fast I could put a razor sharp edge on the plain ol' scissor shears in seconds that wouldn't burn his shrubs like a dull electric shear. (and yes, I've dremel sharpened the 'hedgehog' so he'll believe he did me a favor next month....):blob4:

Steppenwolf
06-25-2004, 08:07 PM
Originally posted by Albemarle Lawn
Go easy when grinding, and sharpen more often so you don't have to try to remove as much metal in one sharpening session. I use a bench grinder and about fortyish blades per week, easy, smooth passes are the key and sharpen more often as Albemarle said.I change blades every nite, sharpen my blades in about twenty minutes at the end of the week. If you are stll having problems get a bucket of water and dip the blade in if you have to. I also try to keep the same three new blades ( each unit uses three) together so they all wear at the same rate and will be replaced at the same time. Nothing worse than leaving a trail on one blade while the other two are doing great.

Kelly's Landscaping
06-25-2004, 10:42 PM
I am wondering how many people here besides myself have heat-treated steel before. I took tool and die making in school and even tried it for a while out of school before I realized how much I hate being inside all day. The temp if I recall was 2000 degrees and that gave you a real nice glowing red you then used tongs and quickly and evenly put the part in to either water or oil depending on the type of steel. This case hardens them the middle still has the original properties but the out side becomes very brittle. While this would give you an awesome edge it could shatter on a rock so I won't be trying it.

If anyone wonders how hot 2000 degrees is and what it feels like I can tell you since my idiot teacher managed to drop a glowing red parallel bar on to my hand. The bar had 3/4-inch holes drilled though it ever inch and had slightly wilder rails on the top and bottom. The steel at that temp melts skin on contact and for about 4 months I had the imprint of that part in the palm of my hand just like that guy in raiders of the lost ark. One good thing about this is you can in the heat of the moment say things to the teacher that would normaly get you expelled.

Sam-Ohio
06-26-2004, 04:56 AM
The biggest problem that I see with grinding blades is caused by grinding them out to a razor sharp edge. If you do this the blade is so thin and delicate that even a small stick can put a deep ding in the sharp edge. Also, if there is little supporting metal behind the leading edge, the edge will just "roll" right off.

A straight razor, with its hollow ground blade profile is the perfect example of what NOT to do to a mower blade. If you use a grinding wheel so that it hollows out the mower blade like a razor, the edge will be so thin, and poorly supported that the edge will quickly be knocked off and all dinged up.

This is why hand filed blades seem to stay sharper longer. There is no way to file the blade out hollow with a file ! Its the thicker profile to the blade edge that supports and strengthens the edge.

Using a belt sander also is a good way to avoid getting a hollow grind in your blades. This is the reason they seem to be more durable - because they are profiled better !

Look at a brand new factory sharpened mower blade. They are always ground with flat, straight edge angles, never hollow ground. This is why they seem to hold up better, and if you sharpen them out hollow and thin edged with a wheel grinder, they never do stay sharp for a whole day again.

I don't believe that the heat produced by grinding your blades [even if you get a bit of surface blueing] has that much affect on the tempering and toughness of the blade steel - especially the deep underlying steel, but grinding away too much of the steel and getting a thin razor like edge sure will weaken the whole edge structure.

Steppenwolf
06-26-2004, 06:56 PM
Sam, I agree with you, I don't put a razor sharp edge on my blades, I only sharpen fron the top down and use a hand file to clean up any nicks on the bottom of the blade that way I do not lose the sharp edge. Know what you are saying and agree completely.

Greg Allbritton
06-29-2014, 12:05 PM
I used a grinder one time to sharpen my blades .I was a woodworker for thirty + years and sharpened my own blades and other tools myself to save money and had a machine that did the job very well, but when it came to lawnmower blades I found that the machine was just to much for the blades. I now sharpen my blades the old fashion way ,with a large file. A 14" file feels pretty good in your hands and is easy to handle and control. If you have a friend or now someone who does laminate work ask them for a Plastic cut file or at a hard ware store,they are not cheap but worth the money. The very first thing you need to do is clean as much of the old grass and goop of the blade. Then secure the blade with the back side of the blade up,then flat file the backside of the cutting edge of the blade, if you don't do this you are not getting a good sharp edge. After the blade is clean and the backside of the blade is smooth turn the blade over ,secure it and follow the factory bevel of the edge,take your time use nice easy strokes .One thing I have learned over the years is if your blade is sharp you get a cleaner look on your lawn but mostly you are doing your mower a big favor a good sharp blade will be easier on your machine because a sharp blade takes less RPM to cut and we all want our machines to keep running as long as we can.

sjessen
06-29-2014, 12:12 PM
Our blades do not last long enough to go through all that trouble. We only get one sharpening out of them. By the time they are dull again the sail is worn off from all the sand here.

Sand for you. Stumps and rocks do it for me.

windflower
06-29-2014, 02:52 PM
I was just sharpening the blades on my gear and mentioned to my Dad (whos a welder) about not being able to keep the blades from turning blue (and taking the temper out of them as I read on here awhile ago) He said its true that heating them up to the blueish color will take the temper out but he told me how to put it back in :p He said you have to heat them up to a dark cherry color and then immediatly dip them in oil. Im thinking you'd need a torch or somthing to heat them up that much and I doubt Ill try it... but I thought it was pretty cool :D

Change to a different kind of stone. Ruby stones cut faster and cooler than typical grey stones that come with the grinder. You really have to work at it to over heat the blades with the ruby stones.

Patriot Services
06-29-2014, 03:07 PM
If I had a nickle for every time this topic comes up over the years. Usually by now somebody swears on a stack of bibles that if you don't have Magnamatico Super Sharper machine with matching balancer then you are ruining blades and grass and spindles.
Posted via Mobile Device

windflower
06-29-2014, 08:41 PM
If I had a nickle for every time this topic comes up over the years. Usually by now somebody swears on a stack of bibles that if you don't have Magnamatico Super Sharper machine with matching balancer then you are ruining blades and grass and spindles.
Posted via Mobile Device

They are nice machines, but I'm too cheap to buy one. I get by with a 8" delta grinder.

DXN1EL
06-29-2014, 10:57 PM
What I do is clamp the blade on a table and place a bottle full of water with a hole on the cap and have the bottle spray water on the blade while I'm sharpening it with an angle grinder It does't even get warm

Groomer
06-30-2014, 10:01 AM
my blades were so dull it made me lose my temper!

milkie62
07-02-2014, 12:22 AM
Try cleaning your wheel with a stone.You could be plugging it up with crap from the blade causing you to apply more pressure which in turn makes heat.

Snyder's Lawn Inc
07-02-2014, 12:33 AM
You can use harden rods weld on the blade

There is a new Blade sharpener I can buy from my wholesaler The Wheel is in a bath of water sharpen blades with a wet grinder If I can find someone buy mine I'll buy a wet sharpener

unkownfl
07-02-2014, 01:04 AM
Ditch the bench grinder for a flapper wheel on a angle grinder. I use a 60 grit and it's really hard to get it overheated. Also, it's a lot easier and faster for me than the bench grinder.