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Author Topic: homemade circle mill 25"blade gets hot and dishes  (Read 14087 times)

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Offline Chico

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Re: homemade circle mill 25"blade gets hot and dishes
« Reply #40 on: September 27, 2010, 12:35:01 am »
In reality a saw collar is measured by thousanths and the taper should only be on the first 3/8 to 1/2 inch or so where is your guides in relation to the eye and the rim of your saw how much lead do you really have in in it and is the tooth spacing and set or swage the same all the way around the saw these are critical factors in saw performance and being free from rust and having flat surfaces where you collars fit is very important  jmo
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Offline simplicityguy92

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Re: homemade circle mill 25"blade gets hot and dishes
« Reply #41 on: September 27, 2010, 09:19:17 pm »
so wat is the better rpm 500 or 300 for a circle mill

Offline buildthisfixthat

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Re: homemade circle mill 25"blade gets hot and dishes
« Reply #42 on: September 27, 2010, 10:16:47 pm »
500 rpms is the better speed most run 500 to 700
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Offline weisyboy

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Re: homemade circle mill 25"blade gets hot and dishes
« Reply #43 on: September 27, 2010, 10:35:38 pm »
depends on your saw diamiter.

Offline Carpenter

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Re: homemade circle mill 25"blade gets hot and dishes
« Reply #44 on: September 27, 2010, 10:50:08 pm »
Thanks, Buildthisfixthat.  I had a much more detailed explanation but you beat me to it.  It's all a balancing act really between power available, feed speed, and saw diameter.  Weisyboy mentioned rim speed, and I think he has a point however my headsaw 50" is running at 600 rpm and the rim speed is 7850f/m.  It seems to cut pretty well.  Number of teeth play a role in feed speed and power needed as well.  300 rpm would be pretty slow, the blade would not have much inertia to make it through the cut, however I have seen one old blade on a water powered mill that was designed to run slow, so it can be done.  

Offline Ron Wenrich

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Re: homemade circle mill 25"blade gets hot and dishes
« Reply #45 on: September 28, 2010, 05:44:41 am »
If rim speed was that important, why don't all mills running a certain sized saw run at the same RPM?  Why is there a difference in shank styles?  Why don't all mills have the same sized collars?  Rim speed is a factor, but not the factor.  I've run 54" blades as slow as 325 or as fast as 700.  They can be made to cut at all those RPMs, and to cut efficiently.  The faster you go, the more the problems.

One factor is power.  Less power means you can drag fewer teeth through the log.  Many guys will only use every other tooth when power is not enough. 

Then there is how the power is delivered.  I've seen guys run big engines, but not enough belts to deliver the power from the engine to the arbor.  That's a problem, but they often know much more than I do and think you can deliver 150 hp through 3 or 4 belts.

Feed speed is important.  I've seen guys take their control stick and pull it back the whole way to feed as fast as they can.  Their lumber looks like it too. 

Sharpness counts, as does proper filing techniques.  You can file lead into or out of a saw.  Sometimes the teeth aren't manufactured very well.  Sometimes the logs grow in a manner that doesn't allow for fast feeding.  When you have problems, you better be able to figure out which ones to target. 

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Offline bandmiller2

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Re: homemade circle mill 25"blade gets hot and dishes
« Reply #46 on: September 28, 2010, 06:56:10 am »
Anouther factor with headsaw speed is the chip size per tooth,you want each tooth to take about 1/10 inch per revolution.At high rpm's that log is flying buy you like your standing beside the interstate,anything happens you have little time to react.High speed sucks up horsepower and fuel and throws a big load on your offbearer.As Ron says their are many variables,but when everything works out right you know it. Frank C.
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Offline Tim

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Re: homemade circle mill 25"blade gets hot and dishes
« Reply #47 on: September 28, 2010, 07:39:03 am »
Anouther factor with headsaw speed is the chip size per tooth,you want each tooth to take about 1/10 inch per revolution.At high rpm's that log is flying buy you like your standing beside the interstate,anything happens you have little time to react.High speed sucks up horsepower and fuel and throws a big load on your offbearer.As Ron says their are many variables,but when everything works out right you know it. Frank C.

Actually, the feed rate rule of thumb is 4" per revolution. I built the hydraulic drive on my mill to this capacity. That makes it PDQ, and I rarely, if ever run the feed to this speed. Mind you, I also set up the circuit to return 4x as quick.

I have the headsaw on my sawmill hammered for 800 rpm. Both my 48" and 52" are hammered this way.

I have a Ford 300 6cyl for a power plant on the sawmill with a direct drive through a modified drive shaft. With a good mechanical governor. Quite frankly, it is underpowered. I used what I had...

So: As we've moved away from builditfixthat's issue in the thread... :) I'm sure some of you are looking at this with a raised eyebrow. This is why I set my mill up in this manner:

The blade is hammered for 800 rpm to provide extra stiffness to keep the saw straighter when the rpm drops off in larger stuff, particularly on the first flitches that are taken off.

The feed rate is important. If the rpm drops off the saw tends to wander. Control of that feed rate to a fairly reliable degree contributes to this. The control for my carriage drive is mounted on the floor with a long piece of pipe for a handle to make it easier to feather the valve.

Sharpening is important, both the tooth and the shank. Throw in tooth clearance here as well. Clearing the gullet prevents the saw from scrubbing on the wood. In frozen, or partly frozen wood, it prevents the sawdust from refreezing on the cut and rubbing on the saw. Shanks and teeth have to be centred. 

Rust free saws and collars are important. The slightest bit of dirt in the collar, where it bears on the saw, can cause heating in the saw.

Torque through the drive line will twist the shafts; This twist translates into lost power. Try this with a seized nut and bolt sometime. Put a few extensions between the ratchet and the socket and try to loosen the seized nut, then remove the extensions and do the same. I shortened my drive shaft by 8" and figure I saved about 5% of my horsepower.

There are more issues to running a circular saw than rim speed. Weisyboy's math looks in line to me though...

I've found that if mine is heating, the first place I look is to the sharpening, then cleanliness of the saw.

The 8" saw on the shingle edger I built is running 8000rpm. The 32" blade on my shinglemill is running 1700 rpm. I run the sawmill at 750 rpm... I hate slow equipment, but I feed them to keep the rpm up as well.
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Offline Jeff

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Re: homemade circle mill 25"blade gets hot and dishes
« Reply #48 on: September 28, 2010, 09:09:57 am »
Actually, the feed rate rule of thumb is 4" per revolution.

Actually, that statement can only applied to a given saw with a given amount of teeth.  Bandmiller2's  statement about per tooth is much more accurate.  He said per tooth, per revolution, not just per revolution.
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Offline Tim

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Re: homemade circle mill 25"blade gets hot and dishes
« Reply #49 on: September 28, 2010, 10:06:31 am »
Actually, the feed rate rule of thumb is 4" per revolution.

Actually, that statement can only applied to a given saw with a given amount of teeth.  Bandmiller2's  statement about per tooth is much more accurate.  He said per tooth, per revolution, not just per revolution.


I should read more closely...
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Offline buildthisfixthat

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Re: homemade circle mill 25"blade gets hot and dishes
« Reply #50 on: September 28, 2010, 11:11:06 am »
ahah now that my blade stays cold and flat thank you to all forum responders made targeting my problem a easy bullseye ,(toothset)i almost threw in the towel on 4 weeks of enginerring and fabracating .now that im sawing logs into lumber ,whats the average time it takes to saw lets say 6"dia 10 foot long log into a 4x4 ?my time is 10 minutes from dogging to done .what do you think also carpenter metioned inertia =torque im looking for a bit more torque i have a flywheel from a model a weight is about 30 lbs was thinking to put it on the arbor ? any ideas as to ideal placement ? jackshaft ?end of arbor . how will it relate to h/p 
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Offline Tim

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Re: homemade circle mill 25"blade gets hot and dishes
« Reply #51 on: September 28, 2010, 11:29:30 am »
I'd put it on the arbour.
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Offline Ron Wenrich

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Re: homemade circle mill 25"blade gets hot and dishes
« Reply #52 on: September 28, 2010, 05:23:51 pm »
ahah now that my blade stays cold and flat thank you to all forum responders made targeting my problem a easy bullseye ,(toothset)i almost threw in the towel on 4 weeks of enginerring and fabracating .now that im sawing logs into lumber ,whats the average time it takes to saw lets say 6"dia 10 foot long log into a 4x4 ?my time is 10 minutes from dogging to done .what do you think also carpenter metioned inertia =torque im looking for a bit more torque i have a flywheel from a model a weight is about 30 lbs was thinking to put it on the arbor ? any ideas as to ideal placement ? jackshaft ?end of arbor . how will it relate to h/p 

I average 5-6 lines/minute and that includes turning.  Also, that's in oak.

 
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Offline Jeff

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Re: homemade circle mill 25"blade gets hot and dishes
« Reply #53 on: September 28, 2010, 05:35:01 pm »
For clarification in case its not clear what a line is, Its the sawing pass and return of the saw.
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Offline Corley5

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Re: homemade circle mill 25"blade gets hot and dishes
« Reply #54 on: September 28, 2010, 09:54:05 pm »
I can break a 16" diam x 14' long big tooth aspen down completely into 2"X10"s in 9 mins from the time the log is dogged until I release the dog board  :)  My offbearer did the timing  :)  I guess I wasn't sawing fast enough if he had time for that  eh eh
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Offline Reddog

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Re: homemade circle mill 25"blade gets hot and dishes
« Reply #55 on: September 28, 2010, 10:19:47 pm »
I guess I wasn't sawing fast enough if he had time for that  eh eh

You sure work your dad hard.  ;D