Open discussion on hook angle for CSM chain

[BlueRider]

When thinking of hook it is easiest to think in extremes. If the hook were ground at 90* the cutting edge would be very strong but it would take a lot of power to make a cut with it. if the hook were ground to 20* it would take much less power to pull it through the wood but it will get dull very easily. the optimum hook is somewhere in the middle, something that optimizes cutting speed with the available power and maximizes the sharpness of the cutting edge. put another way it will depend on what saw and what wood you are cutting as for what hook angle is best.

That all said I file my chains with 40* hook, 10 top plate and no tilt. because I hand file I tend to keep them the same rather than change them to suit the wood I am miling, a bit of lazyness on my part.

 

[glennschumann]

mntgun,

Nice work. I'd like to know the results of changing the 8 pin to 7 if you run the same set up... will you get the same wash board effect with the 7 pin. The reason I ask is that I had a lot of wash boarding with an 8 pin on my 066 set up, while the 7 pin gave smoother cuts. I could not remember if this was the only variable between the cuts, but my theory is (If it was the only variable) is that chains repeat their sequence every 8 drive links, and if the chain gets the same "oomph" from a combustion event every time, say, a right hand cutter is in the same place in the log, it may lead to a tendency for some sort of sympathetic vibration or wobble in the chain resulting in the wash board. Since I use a 7 pin on everything except my 24" bars, and my 24" bars (one old, one brand new) give more wash boarding, it is a theory I want to test when I get back to milling after a few honey-do projects.

 

[redoakneck]

opcorn:

Very interesting, and all this is for hardwood for a fine smooth finish??

40 degrees, 0 degree top plate. I have to sharpen some wp 3/8 ripping with a file, I may try to head my chains in that direction.

I mill mostly hardwood.



Anyone try a triangular file for that 40 degree cutter face angle, or are you using 7/32 or 13/64????(round)

 

[mtngun]

all this is for hardwood for a fine smooth finish??

Only softwood here, unfortunately. Motivated by A NEED FOR SPEED. :cool2:

 

[mtngun]

Retested the 084 with a 7 pin rim. Same 40/0/2 chain which hasn't been touched up.

1st test -- 0.92 inch/sec

I then leaned out the H another 1/16 turn. Sounded perfect to my ear.

2nd test -- 0.89 inch/sec

3rd test -- 0.82 inch/sec

Average -- 0.87 inch/sec

Speed in cut was still only 7000 - 8000 rpm, and it still required a light touch to avoid bogging.

So maybe a hair faster with the 7 pin, but not a huge difference.

Finish was slightly better than with the 8 pin, but still not as smooth as my 066. Perhaps because chain speed is slower ?

Next step will be to retest the same chain with my 066. I'm betting the 066 will actually outcut the 084 with the same chain.

 

[redoakneck]

Nice work mtngun.

Re: Washboard, It looks like you are getting chain speed and log width synchronicity. Try angling the mill relative to the log so that the synchronicity is disturbed.

Cheers

Will pushing the wedges in tighter keep the board from vibrating or is this not caused by the board vibrating???

I don't know but that washboarding seems could be caused if your chain was too loose?? I seem to have to tighten my chains pretty tight to keep them from dancing all over. I can move them with my hands with some force, need to get a fish scale to see just how hard they are to pull. I am new at this and still trying to get all the info I can.:bang:

Man it is hard to file to that 5 degree angle when you are used to 25-30 for reg chain!!! Seems like driving on the left side of the road when you are used to the right. :msp_w00t:

 

[BlueRider]

An often over looked cause of excessive washboarding is a bent bar. I had a bar with a very slight twist, so slight that I had to pull it off the saw and lay it on my table saw to see that it was bent. It milled fine but would pull strong to one side when bucking,like half the teeth were dull.

Check your bar groove for excessive wear too.

 

[john taliaferro]

Its that new 084 it just isn't any good for milling soft wood . Ive got a nice 036 i could trade you for, if it would help ya any:hmm3grin2orange:

 

[mtngun]

That's thoughtful of you to offer to trade your 036, John. But, I'll force myself to live with this overweight, overrated 084. :msp_biggrin:

More speed tests, the usual 12 1/4" wide ponderosa cant.

First up, the hi-comp 066 wearing the same 40/0/2 3/8 chain discussed in previous posts.

1st test -- 1.26 inch/sec (average 9000 rpm in cut)

2nd test -- 1.2 inch/sec (average 9000 rpm in cut)

3rd test -- 1.2 inch sec (average 9000 rpm in cut)

average -- 1.22 inch/sec

Compare that to 0.82 inch/sec on the same saw with WP 3/8 milling chain ! Impressive. It's also nearly as fast as the 1.24 inch/sec turned in by the same saw with the lo-pro Malloff grind. I don't understand why 3/8 was almost as fast as lo-pro ?

Here's the finish left by the 066 with the 3/8 Malloff grind.

Next, the mildly ported 084. Last time I tested the 084, it had the muffler screen installed, but today I removed the muffler screen. It's running a 7 pin rim.

A granberg'd WP milling chain, ground 40/10/10 on all the teeth. Cutting rakers are slightly less than 6 degrees and scoring rakers are slightly more than 6 degrees.

1st test -- 1.04 inch/sec (averaging 9000 rpm in cut)

2nd test -- 0.89 inch/sec (experimented with 9500 rpm in the cut)

3rd test -- 1.04 inch/sec (back to 9000 rpm)

average -- 0.99 inch/sec

And here's the finish with the 40/10/10 granberg.

Next, the 084 with WP milling chain and the conventional 60/10/10 grind.

1st test -- 1.0 inch/sec (9000 - 9500 rpm in cut)

2nd test -- 1.09 inch/sec (9000 - 9500 rpm in cut)

3rd test -- 0.96 inch/sec (9000 - 9500 rpm in cut)

average -- 1.02 inch/sec

The standard 60 degree grind spun a little faster and was a little harder to bog than the 40 degree grind. Makes sense, because the 60 degree grind does not cut as aggressively.

Here's the finish with the 60 degree grind, definitely the smoothest of the day.

Conclusions: 40 degrees is usually, but not always faster than 60 degrees. It's more aggressive, so it may bog easier, or perhaps the raker angle could be adjusted to compensate ?

Finish is slightly rougher with 40 degrees, but not necessarily enough to worry about, depending on your chain speed. Higher chain speed seems to produce a smoother finish.

I'll try to have one more speed test later, the screenless 084 with 40/0/2 3/8.

 

[mtngun]

Screenless 084 with 40/0/2 3/8.

It so happened that I'd used up a cant and had to switch to a different cant for this speed test. Same width, same species, and same age, but still -- it's a natural product with natural variations. Just so you know. :msp_rolleyes:

1st test -- 1.85 inch/sec (average rpm 9300)

2nd test -- 1.85 inch/sec (average rpm 9300)

3rd test -- 1.71 inch/sec (average rpm 9300)

average -- 1.80 inch/sec

That's my all time best speed for any saw or any chain. However, my gut feeling is that this new cant is simply softer than the previous cant. :msp_mad:

Here's the finish with the 40/0/2 at 9300 rpm.

And another spot on the same board.

Conclusions: The 40/0/2 grind seems to work as well as anything, if you don't mind a slightly rougher finish.

 

[mtngun]

I did a little more porting on the 084 and retested. Same 40/0/2 chain and same 7 pin rim.

Here's an end view of the cant used for the test. The sapwood has "blued," which I think is the equivalent of spalting. Anyway, the sapwood is pretty soft.

The previous cut -- the one that turned in the amazing 1.8 inch second -- was 100% sapwood. That's probably why the speed was higher than expected.

Today's cut was about 50% heartwood. Not surprisingly, the speed was slower even though I'm hoping my mods gave the saw a little boost.

1st test -- 1.5 inch/sec (9000 - 9500

2nd test -- 1.5 inch/sec ( 9000 - 9500 rpm)

3rd test -- 1.85 inch/sec (8800 rpm -- I deliberately pushed harder)

Average -- 1.62 inch/sec

I'm not going to draw any firm conclusions from the speeds on this particular cant because the wood seems to be the biggest variable. Also, how hard you push and what RPM you maintain seems to matter. It's a bit of a guessing game to find the optimal RPM.

I guess I need some fresh cants, seasoned but not spalted ?

Why was today's cut rougher than the previous cut ? Well, I don't have a push-o-meter, but it felt like I was pushing the saw a little harder today, forcing it to take bigger bites.

 

[OH_Varmntr]

Very interesting!

 

[820wards]

Mtngun,

Here are few pictures of the Ponderosa pine I milled using a 12* angle on my chain. I'm also running an 8 x .404 rim and I have contoured my rakers very similar to what BobL has done on his chains. The cuts from my mill came out real smooth. Going with the 8 x .404 sped up the chain and I can feel the difference even when milling hard dry oak.

The tree I milled into a bench had only been on the ground for a week, so I don't know if that makes much difference being green. Maybe it does.

The other two trees I milled have been down since last August and they also milled quite smooth. Your logs look like they have been down for awhile and dry, do you find that dryer pine mills rougher or do you think the hook angle on the teeth make for a rougher cut?

These pictures were taken at different areas of bench from the log we milled. I was trying to make the pass without stopping and keeping the mill RPM at a constant speed. With the 8 pin rim I only need to run the motor at just over half throttle. I would say that without the aid of an rpm gauge, my mill head is turning between 6-7K rpm.

 

[mtngun]

Your logs look like they have been down for awhile and dry, do you find that dryer pine mills rougher or do you think the hook angle on the teeth make for a rougher cut?

Roughness seems to be a combination of the hook angle and the 084. Have yet to run into a significant finish problem with 60 degree hook, or with the 066.

Why only 1/2 throttle ? Does that max out the RPM's ?

 

[820wards]

Why only 1/2 throttle ? Does that max out the RPM's ?

I have found that just above 1/2 throttle the 820 PowerBee motors torque curve or power-band drives the chain at a fast comfortable speed once I begin the cut. I could make more power with the motor by installing a higher compression piston and removing one of the three stacked head gaskets, but I haven't seen the need. It has the torque to pull the chain through the wood with ease at a lower rpm. I also have cut my rakers to .043".

The factory rpm range for a stock 820 motor is only about 7600 rpm using points. I am running an aftermarket electric ignition, carbon fiber reed valves and a 1" intake/carb. with a 2" exhaust pipe, so it breathes. I can rpm the motor pretty good when I need to, I just don't need to run it a full throttle to make my cuts. I use less fuel at better than 1/2 throttle without loosing any cutting power. Just to see how rich I could run my mixture, I mixed the last gas I used at 32:1 and I didn't feel much difference in top end power. I normally mix at 40:1.

I have another one of these 820 motors and I'm seriously thinking of building it up to use strictly as a mini-mill motor so I don't have to use my Husky 365 Special for mini-mill work. I was thinking of saving the motor as a spare, and then thought, what am I saving it for. Maybe this motor I'll take out one of the head gaskets and do some porting on the intake runners. I just found a company that sells a .060" cylinder and high compression piston for these motors. I think it would take the 134cc motor and put it very close to a 140cc's. Where's BobL to figure this out when I need him.... :msp_confused:

So, are you changing the hook angle on the tooth to speed up the cutting time? I think it's cool that you are trying the different angles and testing them for cutting times. It will give us all good bench marks to work with. Good milling and thanks for the information you have provided to all.

jerry-

 

[mtngun]

So, are you changing the hook angle on the tooth to speed up the cutting time?

Yep.