Sharpening Bush Hog

[jdkid]

Hi ya
yep cracks and bent blades are best tossed and tossed in pairs if 2 of them .now as for angle i have seen some guys grind on about 30 degrees which even for a lawnmower is a bit flat a better grind is 45 and 60 45 base with a 60 finsh it leaves a thicker eage that will take knocks better .now as for the rounded ends if doing light bush and grass i'd say grind back square ya get a cleaner cut and use less power rounded the blade wants to slide off what ya cutting .as john said blades are cheep so ya could sharpen a set for rocky and thicker bush and use the newer one's on better ground ,from the ground i have done with a slasher i found the blades never got to the point of being sharpened as rocks broke them..another point someone come up with about grinding and the effect on steel it will make ya cutting eage softer witch is not a bad thing in stones ,alot of new blades are to hard and chip or brake instead of denting or bending
catch ya
JD Kid

 

[pennwalk]

Changed the blades today. I was all set for a major struggle. It went so smooth it frightened me. I didn't even have to get the 4 foot pipe out of the truck. Came right off with the 18" slider bar. The chinese sockets underwelm me. I think the nut is 1-5/8 but it wouldn't fit in the 1-5/8 socket. Had to use the 1-3/4 which was kind of loose. I made the nuts as tight as I could get them with the 20" ratchet. I don't have a way to measure how tight they are. Is that enough or should I go back and use some blue lock-tite?

Chris

 

[Anonymous Poster]

How about 1 11/16...? {very popular}

Use a pipe extension (24-36") and go a few more "inches of bar travel"... after about an hour of usage... tighten again with an extension... then check about every 10 hours of usage... {when you grease the loader.../w3tcompact/icons/smile.gif}

Good luck... /w3tcompact/icons/wink.gif

 

[looch]

You used the words bush hog to describe your cutter - I assume it is a Bush Hog brand. My manual lists the bolts as either 1-5/16" or 1-11/16". I suspect yours were 1-11/16."

The torque spec is 300ft./lbs for the 1-5/16 and 450ft./lbs for the 1-11/16. That's a lot of torque - more than most consumer-grade air impact guns. I'd need to "feel" how tight that is before guesstimating. I don't think you could over-tighten them by going as hard as you can without a pipe on the end of your wrench/ratchet.


**looks like JMIII beat me to it.

 

[MikeH]

Hi John,

<font color=blue>they recomend replacement versus "re-sharpening"... due to the "tempered" and "hard-surface process" technology in use now...

<font color=black>Another reason to replace this style blade more often than a finish mower type is due to the "pounding" the blades are subject to in mowing brush, trees, rocks, etc. This "pounding" will have a "work hardening" effect on the blades, which will make them more likley to break.

The "hard-surface process" you mention has been around for a very long time in the form of "case-hardening". Although with todays technologies there are different methods of achieving this, what these processes do is "harden" the outer skin of whatever, and toughen the core.

In the case of Rotary Cutter Blades, sharpening eventually will grind off this hardened steel, exposing the softer core material. But - this core material stands a good chance of being in a "work-Hard" condition, this will "stiffen" the blade making it subject to fracture.

Oh- John, thank you for remaining "unregestered" my PC is most grateful !!/w3tcompact/icons/wink.gif.

Mike

 

[Bird]

Chris, if you got them as tight as the specs call for with a 20" ratchet, you're stronger than I am and have a tougher than normal ratchet./w3tcompact/icons/wink.gif I suspect that you got them tight enough to not have a problem, but I don't think I'd want to risk it.

 

[Anonymous Poster]

<font color=blue>...20" ratchet,...</font color=blue>

Thanks Bird... you're a great proof reader... /w3tcompact/icons/smile.gif
________

Chris...

I missed the "ratchet" part... even though it's a deluxe Taiwanese 3/4" socket set... (busting chops now.../w3tcompact/icons/wink.gif), I'd use a "breaker bar" with pipe extension...

The blade bolts will be grade 8, about 1 1/8" and will handle up to 1200-1500 ft. lbs. of torque...{if that rachet handles that, I'll buy a few sets.../w3tcompact/icons/blush.gif}

The main thing you want to look out for after you torque down the bolts... is to still have the blades "swing" and not be "torqued" too tight into a fixed/non-moveable position... /w3tcompact/icons/frown.gif

 

[ewoss3]

Dang, I want to thank all of you for this enlightening post. My the father-inlaw has been reading this post and admitted he has owned his brushog(unknown make) for 18 years and the blades have never been removed or sharpened. I looked at his blades yesterday and surprisingly they still have a cutting edge(really dull) and are not bent. He uses this thing about 4-6 times a year and takes out everything up to 3", I guess they just don't make blades like they used too

 

[Anonymous Poster]

Question-How do I torque down a bolt @ 1400 foot lbs. with only using a 100 ft. lb. torque wrench...?

<A target="_blank" HREF=http://www.specialpatrolgroup.co.uk/spooky/torque/torque.html>Answer…A Unique Approach To Torque Wrench Multiply/Extensions & Torque Formula's…</A>

 

[AndyR]

Great article John - thanks! Makes much more sense to me then the costly torque multipliers one occaisionally sees.