GB Mill Modifications- REDUX

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aggiewoodbutchr

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A while back I posted this...

http://www.arboristsite.com/showthread.php?t=37090&highlight=gb+mill

Well, finally, I'm closer to finishing what I started. Before I get into the details of the mill mods, I must detour a bit and explain what brought about the sudden need to finish this project.

Last evening I set out to make a 24" square, 8' long oak cant for testing various ripping chains. I mounted a brand new GB 44" harvester bar with FX style roller nose and a brand new Woodsman Pro 3/8 ripping chain to the 084, put it on the mill and got to work. Things were going well; saw was set, rails were on the log, aux. oil flowing, raised rpms to get the chain moving, started the cut, full power, dug in. Made about 12" of cut and it all went to hell. I saw sparks shooting from the bar end out of the corner of my eye and immediately shut her down. Upon inspection I found that bar nose had come loose and cut into the mill about 1/2", wrecking the chain in the process.(Image 1 & 2) Actually, the bar had melted it's way loose from my "prototype" plastic bar mount. You may think that the plastic is to blame here but I have used this exact setup with my 72” bar and .404 chains many times with absolutely no problems.

After studying all the evidence, I was able to conclude that the root of the problem was a combination the FX bar nose and 3/8” chain. GB advertises that their FX bar tips will function similar to a sprocket nose but with the advantage of being able interchange 3/8” and .404 chains on the same bar. I found this to be only partially true after comparing the fit of both .404 and 3/8” chains of various manufacturers on a new FX bar tip. As you can see in Image 3, the .404 chain chassis is picked up clear of the rails as it should be to reduce friction. Not so with 3/8” chain due to it’s shorter drive link (Image 4). The result of this when I was milling was a tip that got very hot, very fast as you can see by the burnt paint (Image 5).

Continued…
 
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After speaking with the GB rep, I decided my best course of action was to grind down the rails on the tip to give the 3/8" chain the clearance it should have (Image 6).

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Then I turned my attention to the mill. I replaced the plastic doohickie I made months ago with this.


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Tomorrow I will give it a whirl. My fingers are crossed until then...
 
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Bites that you ruined a brand new chain! Ive done the same thing though, bolts worked themselves a little loose and started cutting into the mill.

Good fix.
 
Bites that you ruined a brand new chain! Ive done the same thing though, bolts worked themselves a little loose and started cutting into the mill.

Good fix.

Fortunatley it's not a total loss. It's just stretched real bad. Some work with the chain grinder should salvage some life out of it.
 
update

I got to finish what I started today. The mill and bar performed flawlessly. Also got to play with *cough*... test a few different ripping chains. The results are promising. More on that in the future...

Sorry some of the pics are dark. I was using the cheap camera (weak flash).

This was as far as I got the other day.

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set up for the second pass

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Using lag bolts to support the middle of the rails.

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last cut almost complete

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24" sq. cant

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aggie thanks for all that detail, and pics. A picture is definitely worth a thousand words when it comes to this kind of thing. Yeah beating up a new chain right off the bat is a bad way to start a milling session. I did something similar, ran my just sharpened milling chain right into one of the steel supports that was holding up my guide. 30 minutes of serious hand filing. In my case though, it was just pure stupidity. In your case, you had every reason to think you were doing everything right given your past experience with that setup.
 
Got to really put the mill to work today. This is what I brought home. These cants will be slabbed down at a later date.

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When I find the camera I was using all day I'll post some pics of how I got there.
 

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