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Discussion in 'Magna-Matic' started by zapper, Jan 12, 2008.
Too cool! This is one of the reasons I love Lawnsite!
Works great too!
I can sharpen my Honda HRX waved blades as easily as the Bad Boy straight blades on this set up...
The belt/grinding wheel heating up is not the cause of steel losing temper. Your blade will turn color just as quickly on your sander.
I think it says a lot about Lawnsite and Magna Matic that your posts of this nature are still here. Your way of sharpening may be very nice, but it might have been more appropriate in another forum. I'm not saying all posts here should smell like roses towards the manufacturers/sponsors. I've surely blasted my share, but geez...
PS. Magna Matic 9000 order on the way...
Don't get me wrong. Magna-Matic is top notch equipment and I would buy from them if I had the need to sharpen more blades than I do.
I find my setting just a little more versatile and adequat for my use.
On this setting, I have yet to get a blade so hot that I could not touch it with my hand. The sanding belt takes a lot of the heat away from the blade and instantly cools down as it runs while a grinding wheel "accumulate" heat.
Just to add some clarification.
The blade temperature is not due to GRINDING WHEEL vs SANDING BELT. You can burn blades with sanding belts, angle grinders, bench grinders etc. The only time a belt would be cooler than a grinding wheel is if you were to compare identical compounds, grits, running at the same speed, etc of both the sanding belt and grinding wheel, AND that the belt had a greater surface area then the grinding wheel. In other words the belt would need to be very long. HAPPY FROG in the post above this one, says that grinding wheels accumulate heat. This is incorrect. Instead, it should be said that all abrasive operations generate heat via friction.
Magna-Matic sharpeners are designed that the grinding wheels relieve the heat of the grinding process by proper grinding compound, hardness, surface feet per min, speed, etc. Also note any abrasive process has the potential of overheating the material, but through the design of the machine the heat is managed or relieved.
When making comparisons, many variables must be addressed. Dont compare apples to oranges.
In the subject of abrasives there are many many factors that affect heat build-up. For example: abrasive speed, surface feet per minute, surface area of the abrasive, drive speed, (grinding wheel diameter, belt length), abrasive compound, grit, hardness, rate of feed, steel type, and much more.
Heating a blade to the point that it turns blue will remove the temper UNLESS it is immediately quenched. Heating a blade to that point changes the crystal structure of the metal, as it cools slowly it will slowly return to its original base carbon steel hardness.
Austempering, and other hardening processes function by heating steel up to a temperature, and quenching it. The heating changes the crystal structure, and the quenching (fast cooling) keeps the crystal structure where it was when it was heated. Type of hardening is dependant on type of steel, temperature, quenching medium, etc. Example quenching mediums are water, oil, salt, etc.
This post is in reference to a post in this thread left by HAPPY FROG, on 1/15/2008 7:41 am. Happy Frog challenges us (Magna-Matic) to consistently maintain proper cutting edge angle.
Magna-Matic was the first, and continues to be the only manufacturer of lawn mower blade service tools, that offers sharpeners that will consistently sharpen blades at 30 degrees every time. The angle remains consistent regardless of grinding wheel diameter. This 30 degree reference point angle is Also our equipment can easily be set to match any angle you like if you prefer something other than 30 degrees.
To add an important safety recommendation:
In the photos of HAPPY FROGS belt sander, I assume as with the vast majority of belt sanders the direction of the belt is running down through the slot in the table they provide as a guide. When HAPPY FROG removed this table to insert his blade angle guide, he created a PINCH POINT or a point at which the part (blade) he is holding can jam between the guide he made, or pinch the sanding belt causing it to break. In abrasive machines it is highly unsafe to create pinch points of this nature. This is why the tables that are put on belt sanders have very small slots only for the belt to go through. HAPPY FROGS design may be inexpensive, but it may also be unsafe.
Also remember a belt sander at $70.00 that is probably made in China for light home use, is NOT intended for heavy metal removal or hogging those belt sanders are generally intended for light metal deburring, or woodworking. Re-sharpening a lawn mower blade is sometimes a re-machining operation where a great amount of material must be removed. It is also unsafe and unwise to load a machine not intended for the purpose you are using it for.
Keep in mind it is for this precise reason that YOU the landscapers and lawn care professionals use COMMERCIAL mowers. Not a modified MURRAY that you purchased at Wal-Mart.
Magna-Matic is a family owned company, and we love innovation, and in the past Lawnsite.com members have provided valuable advice and ideas on how to improve our products. This thread was not deleted, or moved, nor will it be because it initiates an important dialogue that provides the Lawnsite members with valuable information. We certainly do not want to suffocate an innovative spirit, but please do not risk your safety for a small dollar savings.
There are many good points in your explanations.
Nice machine! I did around 40 blades and after the first few it went much easier. It took a while to get them to the sharpener's angle, but once this is done it will be much quicker. I noticed new blades are not the same angle either.
It would be nice to have the extension table standard. It wouldn't cost that much more for it be to included with the machine. It would help to reduce burning the very end tip of the blade as a result of lack of support.
All in all, a very nice piece of equipment though.
Thank you for the complements.
Please note due to all the different blades in the industry, we keep the standard worktables onthe MAG-9000 as standard. There are many blades that the extended worktable would restrict from being sharpened. We also have 2 styles of extended worktables.
So we felt that shipping every MAG-9000 with items that may or may not be used with every user was not prudent. And in the future as other blades come out we may have to create new worktables. It is actually a fairly low percentage of people that purchase the extended tables, compared to MAG-9000 purchases.
In regards to burning the tip. The extended table would probably not improve this. If you are burning the tip, it indicates that you are grinding it for too long without movement. Grinding requires some heat managment. Moving back and forth along the cutting edge helps distribute the heat. If you have an exceedingly BAD (worn) tip, grind for some time, then switch to the other end of the blade to allow the first to cool a little. Quenching with water will also speed up the process.
Once your blades get in proper shape (angle cut, and mantenance schedule) this will not be such a problem, because you will be removing a smaller amount of steel which = less grinding time which = less heat also.
Thank you for your comments!!
The tip was being burned because of lack of support for the blade. As I pull back and get to the tip, there is the great majority of the blade hanging off the table. This causes the tip to go upwards into the wheel unless excessive pressure is placed on the blade to keep it flat. It isn't the speed at which I pass the blade under the wheel. I have also seen the table flex in an effort to keep the blades from doing this.
I have also found that the wheel kicks a heck of a burr on the underside of the edge. It just took me a a bit to figure out it makes the blade "stick" then burn, as I drag it across the plastic. I keep a file handy and remove the underside burr every couple of passes.
The blades I am sharpening are the standard/hi lift/mulch from J-Thomas as well a few OEM Scags. 52 and 61" decks. Nothin' fancy....