Chip Clearance, what is it?

[Terry Syd]

'Chip clearance' is a term that keeps getting batted around. So what is it?

You get comments that it slows down the cutting. OK, why? Well, there are too many chips. So, why does that slow down the cutting - you know, the PHYSICS OF WHY it slows down the cutting.

If any cutting should slow down because of chips, it should be when noodling. The chips are considerably longer than cross-cutting chips. Crikey, look at the amount of wood that comes out of a cut while noodling.

I have a theory that when a raker is pulled over a chip while cutting, the chip decreases the cutting angle of the cutter and tends to take a smaller bite. That theory seems to be supported by the rakers that racers use on their racing chains - they make the front of the raker vertical, probably to block chips from getting under the raker.

If that technique works to prevent 'chip clearance' during racing, it should also work when using a very long bar when you are out logging, like on a big back-cut. Anybody have any experience with modding a chain to decrease/eliminate any problems with 'chip clearance'?

I've never had any problems I can relate to 'chip clearance', however I would like to clarify this concept as it keeps getting thrown around when someone has trouble with a chain.

 

[spencerpaving]

One thing I can say about clearance....On the bikesaws high tooth chain cuts alot faster than reg 404 sharpened the same way....It also takes alot more power....When I run a practice chain the cut time is slower but the saw is easier to handle...With the high tooth you can feel the saw working and it will push you back out of the wood on the upcut if you aren't ready for it...

 

[Terry Syd]

I'm not sure what you mean by 'high tooth'. Is that a chain where the cutters stand taller on the chain chassis or is it a chain with the rakers lowered (increased cutting angle).

 

[Terry Syd]

When a chain takes a lot more power, that is usually indicative of a larger cutting angle (it is taking a bigger bite). The fact that a saw tends to push back immediately on the up cut suggests a large cutting angle and nothing related to 'chip clearance' as the chips haven't even started to flow.

Raker depth can be deceiving as to what the actual cutting angle is. The cutting angle is a trigonometric function. The hypotenuse of the right triangle is measured from the tip of the cutter to the CONTACT point of the raker with the wood. If the raker is flat on top the contact point will be all the way to the front of the raker. If the raker has a good slope to it, the contact point should be all the way at the back of the raker. That makes a big difference in the length of the 'gullet' and the trigonometric function.

Here is a trig calculator for a right triangle -

http://www.pagetutor.com/trigcalc/trig.html

x=the cutting angle
C=the gullet length
A=the raker depth

When you put in the gullet length and the raker depth, you get the cutting angle.

 

[cre73]

Interesting read, but way above my paygrade!!

 

[mdavlee]

Long bars buried can clog the whole kerf to the point of stopping the chain and having to pull the bar out and clear the bar.

 

[mgr1]

High tooth is a harvester chain?

 

[Terry Syd]

Long bars buried can clog the whole kerf to the point of stopping the chain and having to pull the bar out and clear the bar.

Now there is a 'chip clearance' problem I can readily understand. So many chips backed up in the kerf and creating friction that the chain stops moving. Perhaps that may be a reason that some racers 'tunnel' the cutters, they can create more area inside the cutters to hold the chips instead of the chips lodging against the side of the chain.

 

[mdavlee]

Now there is a 'chip clearance' problem I can readily understand. So many chips backed up in the kerf and creating friction that the chain stops moving. Perhaps that may be a reason that some racers 'tunnel' the cutters, they can create more area inside the cutters to hold the chips instead of the chips lodging against the side of the chain.

Pretty much. Some race chains pull chips so fast they can't clear the kerf and will be slowed down. Gum is the worst to rwce in thst they use in the southeast

 

[Terry Syd]

OK, then a SYMPTOM of inadequate 'chip clearance' is that the chain slows down. There is more load, but the chain is still cutting.

One of the racers I know in Oz uses a Narrow Kerf chassis for the chain and then puts on square cutters off of a regular .325 chain. He can square file the cutters and has a lighter chain with more clearance on the sides.

Since there is a lot more wood being cut during noodling, then it appears that a 'chip clearance' problem is more likely to occur when cross-cutting with the small chips being able to lodge against the side of the chain.

 

[Wilhelm]

Take a drill bit with flutes shorter than the desired hole depth and start drilling.
As long as the flutes are outside of the material they can clear the chips, the moment the flute ends are buried below the holes entry surface the chips can no longer clear. The chips will pack the flutes solid and cause loss of feed and high friction to the point of drill bit breakage or engine stalling. With a hand held drill one can easily get hurt if the drill bit is large and the drill powerful.

I know this is not exactly what You are looking for but it is the same principle.
I work with drills on a daily basis, we often have issues with chip clearance when drilling deep holes and taping blind threads.

Generally, chip clearance issues occur when the teeth of a specific loop cutting a specific type and diameter log are creating more wood chips than can fit in the free spaces between and under the cutters.
This will cause loss of bite, binding and quite possibly engine stalling.

The amount of chips to clear bucking vs noodling is the same, given that all related circumstances are identical!
But noodles are larger sized which may cause chip clearance issues sooner then when bucking.
To my understanding an engine gets loaded more while noodling than while bucking!

Disclaimer:
I'm no expert, I'm no pro, I'm just a homeowner firewood hack!
My writing could contain faulty information, if so it is unintended.

 

[Terry Syd]

To my understanding an engine gets loaded more while noodling than while bucking!

Yeah, I've run into that myself. However, if a noodling chip is removing 4-5 times as much wood as a cross-cut chip, then there must be some extra resistance to the cutting. Granted, the noodling is going with the grain rather than cross the grain, but I still think taking out that extra amount of wood should put a bigger load on the engine.

I don't know. I'm tempted to try a trick I read about. You cut a thin cookie halfway through the log and hit the kill switch and leave the saw in the wood. Then you lever off the top half of the thin cookie and take a look at what the chain looks like. It should show how the cutters are working and how the chips are moving.

 

[Deets066]

'Chip clearance' is a term that keeps getting batted around. So what is it?

You get comments that it slows down the cutting. OK, why? Well, there are too many chips. So, why does that slow down the cutting - you know, the PHYSICS OF WHY it slows down the cutting.

If any cutting should slow down because of chips, it should be when noodling. The chips are considerably longer than cross-cutting chips. Crikey, look at the amount of wood that comes out of a cut while noodling.

I have a theory that when a raker is pulled over a chip while cutting, the chip decreases the cutting angle of the cutter and tends to take a smaller bite. That theory seems to be supported by the rakers that racers use on their racing chains - they make the front of the raker vertical, probably to block chips from getting under the raker.

If that technique works to prevent 'chip clearance' during racing, it should also work when using a very long bar when you are out logging, like on a big back-cut. Anybody have any experience with modding a chain to decrease/eliminate any problems with 'chip clearance'?

I've never had any problems I can relate to 'chip clearance', however I would like to clarify this concept as it keeps getting thrown around when someone has trouble with a chain.

This is why skip chain is used for long bars. It's not about being easier to pull because there are less cutters. It's easier to pull because you have a more efficient area to pull chips out of the cut

 

[Terry Syd]

Yeah, I was just thinking about skip and semi-skip chain. If you had a long bar that was jamming or slowing down, then a loop of semi-skip/skip should fix it. Not only are you taking less bites and therefore less chips, but there is more area for the chips.

EDIT: If you had enough power, then perhaps go to skip chain and put on a larger rim. You could keep the chips flying. but with less 'chip clearance' issues.

 

[Deets066]

Yeah, I was just thinking about skip and semi-skip chain. If you had a long bar that was jamming or slowing down, then a loop of semi-skip/skip should fix it. Not only are you taking less bites and therefore less chips, but there is more area for the chips.

EDIT: If you had enough power, then perhaps go to skip chain and put on a larger rim. You could keep the chips flying. but with less 'chip clearance' issues.

I used to run a 32" full skip with a 9 pin. It creates more heat, and is harder on the clutch. 8 was a little easier on everything

 

[Terry Syd]

Thanks guys, if I ever run into the 'chip clearance' phenomena, then I will know what to do to fix it.

 

[spencerpaving]

Bad pic...Top is a old .404 high tooth compared to a reg .404

Sent from my Pixel using Tapatalk

 

[Wood Doctor]

If the raker (depth gauge) is too low and the tooth too high, you will cause more vibration and put more load on the motor. It can get bad enough to stop the chain dead, even with a strong engine, and drop your cutting speed to zero.

On the other hand, if the raker is too high, you will produce powder galore and practically no chips. Your saw becomes at most a power rasp.

A few loggers I know never drop the rakers. They give those chains to me after they start producing lots of powder. I drop the rakers and hardly need to sharpen the cutters in order to salvage the chain. They already did that with a file in the field and gave up on the chain.

 

[Czed]

Long bars buried can clog the whole kerf to the point of stopping the chain and having to pull the bar out and clear the bar.

Absolutely
And dead ash is the worst for me
As far as fine dusty chips
Even on a 20 it will load up after some cutting.
Softwoods no issue's.

 

[Deets066]

Bad pic...Top is a old .404 high tooth compared to a reg .404

Sent from my Pixel using Tapatalk

I was lookin for some of this a while back. Still would love to try out a loop