Grinding carbide chain - your input required...

[Mike Kunte]

Hi Guys!

As you may know, I recently acquired a Stihl Rapid Duro carbide chain for cutting old, hard, dried-out bluegum. It really works splendidly for this application. That is, until I ran over a flat stone under one of the logs I was bucking... I was fortunate in that none of the teeth chipped, but the rock did "flatten out" the leading edge of the cutters on the top plate. See below for the "before" image...



Yesterday I spent over 2 hours restoring the chain on the grinder with my diamond wheel. I took a photo before grinding, and one after grinding. Interestingly, there is a slight difference in the side profile now. Whereas the original grind left the very top egde of the cutter in the "lead" so to speak, my grind left the edge below "in the lead". See below for the "after" image...



Q.1 Do you think having the working edge below the top edge will harm performance?

Q.2 If so, what adjustments can I make in the grinding procedure to restore the profile to factory settings?

Grinding angles used were 75/30/0. I subsequently found another thread on the forums which quotes the angles as 65/25/0, so this could have contributed to the problem. I did find that there was very little room in the gullet, and the grinding wheel kept touching the depth gauge on the inside...



Any help will be appreciated!

Mike

 

[Mike Kunte]

As you can see from the above pics, the shape of the carbide-tipped cutters lies somewhere between that of a full-chisel and a semi-chisel cutter. It literally has a "flat", angled section between the top plate and the side plate. In the factory grind, the working corner is on the "top" of the flat section, whereas on my grind it lies on the "bottom" of the flat section. I tested it out on some of the hard dry wood, and it cut satisfactorily. Even the original grind did not "self feed" (I had to pivot the saw over the spikes), so the feeling is pretty similar on my grind. Slow and steady, with smallish chips.

I need to emphasize that the grinding is a very slow process, mainly because I had to take off quite a large amount of the cutter (probably 1/16th) to get to a "clean" top plate surface. If it had just been a touch-up, I'm sure it would have gone more quickly. Furthermore, the carbide is so hard, that it deflects the travel on the incoming grinder head, which pushes the disc to the right. One really has to "lean" in left to keep it cutting on a straight path. A learning curve for sure...

 

[Brent Adams]

Seems lile depth gauges are really close to the cutter. Guess thats why the stone gets into them. What diameter wheel are you using?
I'm thinking that chain is designed for extreme conditions, and that may be the reason for the cutter profile and depth gauge setup.
Sacrifice cutting speed for longevity.

 

[Mike Kunte]

Seems lile depth gauges are really close to the cutter. Guess thats why the stone gets into them. What diameter wheel are you using?
I'm thinking that chain is designed for extreme conditions, and that may be the reason for the cutter profile and depth gauge setup.
Sacrifice cutting speed for longevity.

It's the standard 5 3/4" wheel, just like my others...

 

[CR888]

'Chamfer chisel' may be the descriptive term your seeking. I think your side profile appears OK but whether you have taken ground the top plate back to fresh metal or not cannot be seen.

 

[Mike Kunte]

'Chamfer chisel' may be the descriptive term your seeking. I think your side profile appears OK but whether you have taken ground the top plate back to fresh metal or not cannot be seen.

Thanks, CR888!

I knew someone here would have the correct term! I did manage to get the top plates back to clean metal. I was just wondering if I could change some or other setting on the grinder to keep the working edge in its proper position.

 

[CR888]

75° is pretty steep, is 15° off being 90°/flat but that's not exactly a bad thing on a chain dedicated for such demanding work. Testing is what will best answer that issue. But you could use anywhere from 60-80°. I don't have much hands on exp with carbide, I tend to avoid it & use .404 chipper. Only because I find it cost effective to repair/maintain & sharpen. Nothing is perfect every chain type has its good/bad points. If your 75° chain is not feeding well perhaps bring it back to 60°-70°. Pain in the butt when you smash up such expensive chain.

 

[Brent Adams]

Sorry, meant thickness of wheel. Brain was still asleep I guess.

 

[Mike Kunte]

Sorry, meant thickness of wheel. Brain was still asleep I guess.

Hey Brent!

No worries! If memory serves, it's a 3/16ths wheel. I'll send you the part number for interest's sake! I must say, it's quite a tight fit in there. On the other hand, as I noted in my original post, the carbide chain is so hard that it deflects the wheel to the right (probably due to a little bit op slop in the pivot point), and you have to keep "forcing" the wheel to the left.

Mike