Thread: ripping chain jumping around

Originally Posted by footrot

I recently made up a ripping chain to go on my lucas slabber (skip tooth Carlton chain) by grinding off three teeth, leaving two. I also took the rakers off. Its factory sharpend to 15 degrees.
At the start of the cut the blade jumps about a lot, to the point instead of a 10mm kerf its about 30mm for about 30-40mm into the cut. After that it seems to cut fine.
Has anyone tried this, had the same problem, can suggest what I might be doing wrong.
I swap the 27 RX back and the jumping stops.
Cheers

You will need to file the top plate filing angle to close to 0º to avoid the jumping at the start but that's no good either. Maybe you can get away with about 5º. The other way to reduce jumping at the start is to use mid-bar support but it takes a bit of effort to do that on a lucas.

From my limited knowledge skip tooth (more than one) usually go Left Right then right left then left right as well as that i am sure the rakers are left on but ground down further than normal. As for the jumping around that might be the rakers - all i can suggest is feed it in really slow for the first 50 mm

to acheive LR RL LR RL you cut off odd number of teeth ie 3 or 5 never 2 or 4.

Hope that helps

Cheers

i've made a heap of chains following the lucas supplied stuff, both 5 skip and 7 skip and haven't had the problem you describe, like calm says, get the left right cutters the right way and you shouldn't have to many problems

thanks fella's for advice so far.
I've ground off three, left two on which gives me LR RL LR etc.
yeah BobL you can put a mid bar brace on the lucas slabber-its called a stick. Tried that too.
I had left the rackers on initially. With the jumping I ground off the rakers to try to solve the problem, thinking it was probably the rakers hitting the wood without the stabilising factor of the tooth biting in to hold it steady.
I usually sharpen to 10 degrees-maybe as you suggest Bob the 5 degree difference is enough to cause the jumping.
I was slabbing crows ash which being very hard probably acentuates the problem.
Hmmm back to the drawing board

The first time I used my big bar I used full comp chain with a 30º top plate angle and noticed huge amounts of jumping. I then started the alaskan at a bit of an angle so only a short section of the chain was making contact with one corner of the log, then I cut the other corner and then cut the middle. By then the bar was half buried in the bar and all was OK. Then I filed the top plate to 10º and had no problems. But it's a bit hard to do that with a lucas.

Are you starting the cut at full throttle? If so, try dropping the revs till you get the cut started then bump the revs up, also if you have removed all the rakers from in front of the cutters left, I doubt that you'll stop the jumping.

DJ, I've not cut the rakers off the teeth that are left, just off the links I've cut the teeth off.
I must admit I did'nt try dropping the revs, it must be a habit I've gotten into where I just set the throttle and leave it there.
When setting the log into the mill I have been expirementing with setting it a bit skewed so I'm cutting along the grain as much as I can rather than straight across. That way I'm also tending to start the cut on the edge rather than across the whole width at once.
Footrot

Originally Posted by footrot

DJ, I've not cut the rakers off the teeth that are left, just off the links I've cut the teeth off.

Originally Posted by footrot

I must admit I did'nt try dropping the revs, it must be a habit I've gotten into where I just set the throttle and leave it there.

Give it a try, it does make a difference. Because of the torque from the motor, you can start the cut at a lower speed

check this link for ideas on ripping chain

http://www.arboristsite.com/showthread.php?t=35585

i run 5 chains at present al of witch are 3 skip. i have made these chains myself by as you say grinding off teath.

here is what i do.

left, right, skip, skip, skip, right, left, skip, skip, skip, left, right.

i use a cutting disk and cut teh tooth and depth gauge more or less flush with the chain.

i then take teh top plate angle back to 17* and drop teh depth gauges with teh angle grinder a fair amount.

the chain will move on teh end of teh log but s soon as it starts to cut its fine. like once i start to put some weight on it it cuts in and is all good.

are you sure your motor i revving flat out. mine will just around if i have it just below flat out.

are teh bolts that hole your bar on tight?

how tight is your chain?

bar might need dressing?