56 insert blade

[Bandtocircle]

Anyone have info on how dished a 56 inch blade should be at stop and how do you set guides while stopped. Blade cuts true in pine and poplar but not in oak over 12 inches blade tends to cut deeper to log side.

[Ron Wenrich]

I'm not sure that dish is the problem.  A lot would depend on the last time the saw was hammered, and if you had any damage since then.  Also, you have to run your RPM for the speed the saw was hammered for.

Many times there are problems with the teeth.  It comes from filing in an angle, or swaging to heavy to one side.  Pine and poplar are more forgiving.  The harder logs will bring out the problems with the filing.  Whenever I troubleshoot a mill, the first thing I do is to put in new teeth to neutralize that as a problem area.  If it still cuts in on the oak, then you have other problems.

I never liked setting saw guides on a stopped saw.  I did it early on, and to do it, I would look to see if the saw was touching the guides when running.  You want to see daylight on the sides of the saw.  If you have too much of a gap on the log side, it would probably dig in.  I found on my saws that the board side was not as critical as the log side.  They wear out faster.  You don't want to push the saw with the guides.  If it looks like too much light by the saw, just stop it, adjust the guides, and see how it looks.  It might take a few tries until you get it where you want it.  Not quite as hairy as doing it while the saw is running. 

It could also be that you have too much lead on your saw.  There is no standard setting for lead.  It may be different from one saw to the next.

Is there a cover over the mill?  Sunlight can do strange things to a saw.  

[Blaszer]

Either lead or blade speed..If a large hardwood log has issues, the blade may be slowing down too much causing it to not saw true.Check your lead......put your carriage next to blade. mark one spot near a tooth.. measure the space from the spot to carriage.....Then spin the blade to the opposite side and make the same measurement...the measurement at the back of the blade should be 1/8 greater.

[dgdrls]

I suspect as Ron pointed-out, you have other issue(s).

Does the saw run true at full speed and what is full speed set at?

As I understand, the saw body should not be "dished" when plumb and set on the arbor,
the log side should be flat unless the collars, guides or ??  are pushing it to a dished condition.

https://www.fpl.fs.fed.us/documnts/misc/cirsaw.pdf

good guide for a circle mill above

D

[Ron Wenrich]

When checking the lead, you need to make sure the guides aren't touching the saw.  They may be pushing lead into it.

[Trapper John]

Whether a saw should be dished or not has always puzzled me, and I know Lunstum says it should not be dished.  However the 3 blades I own are all dished.  And all circle millers say a saw must stand straight at hammered speed.  So I assume that at rest they are not standing straight.  Can anyone clear this up for me?

[Don P]

The rim of the saw is smaller in diameter than the body of the plate at rest. That means that the body of the saw has to go somewhwere, into the third dimension, it pops to one side of the rim or the other, that is the dish. The amount depends on the size of the saw and the speed it is tensioned for.

When the saw spins up to speed the body of the saw is slung outward against the rim which restrains it and the saw "stands up". When you lose tension or operate outside of the hammered speed significantly the rim is loose and wanders.

The dish on my relatively thick and small 46" belsaw blade is very slight, basically flat on the log side and slightly convex on the board side. If I lose speed in cut it heats the eye, too much metal in the body from the heat swelling and it dishes out tremendously. In all of this, because of the lever arm lengths involved, a little moved metal or a little heat, a little goes a long way.

[Magicman]

Thank you Don P.  I know nothing about a circle sawmill but I still read and wonder. ??  Your description explained some of the dynamics that are going on with the blade as it saws.  :P

[Ron Wenrich]

The rim isn't smaller in diameter, but thinner in thickness than the body.  You'll see saws rated as a B-6/8, it would be a 6 gauge at the eye, and an 8 gauge on the rim.  The B would be the style of tooth.  When hammering, they have a ring that they go to and it stretches the steel so that it is consistent all the way around.  They also remove all the high spots from the log side.  When I watched guys hammer a saw, they had 3 areas that they hammered.  The eye, to make it flat, a center ring for tension, and the rim, right below the sockets.  I never questioned they whys and wherefores of what they were doing.  Most saw docs put the saw on a machine that will evenly stretch the saw.  It is usually better than using a hammer.  They still take out the high spots with a hammer.  

You need to have the correct lead to prevent the saw rubbing on the eye.  The tooth is also wider than the rim to provide the needed clearance for the saw not to rub.  When you lose speed, your saw will lay over and open the blade to heat.  Same goes for damaged teeth or dull teeth.  Swaging is a method to spread out the tooth.  The problem with the heat is the steel at the eye can't support the saw.  

If a saw is hammered for the right speed in a mill, it should stand straight.  Usually they hang away from the log.  A saw hammered for a right handed mill can't be used on a left handed mill.  I always had problems with saws that were originally made for a right handed mill, then dished for a left handed mill.  The steel has memory and wouldn't perform as well.   

[mike_belben]

These terms have always interested me but i have no clue what it all really means.  Are we really talking about a voodoo doctor just eyeballing and hand hammering the saw blade?  Against what, like a shot bag or just on a bench?  Or is it a planishing hammer?  How does one figure what speed their hammer job is suited for?


Do saws behave different on first cut of the day when cold?  Im kinda surpised blade temp isnt maintained with fluid.

The mental image im forming here reminds me of old time machinery scraping on ways and dovetails.  

[Ron Wenrich]

This shows the saw doc at work.  It is a little to short to justify what they do, and they will continue to check it out with the level and check the high spots.  

Hammering a circular saw blade. - YouTube

Casey Cramer at Seneca Saw Works is a saw doc that has lots of articles written pertaining to saw hammering.  

The saw speed is figured by the RPM that you're running.  The standard for most of the older mills is 540 RPM.  The last mill I ran was running 690 RPM.  The slowest I run was 350 RPM which is way too slow.  

Temperature does make a difference.  My best production months were May and October.  The cold months brings on things that are frozen on the logs.  I had a debarker and that eliminated most.  But, cold times also slows down hydraulics, which factors in.  Frozen wood acts different than thawed wood.  Cutting half frozen wood is a bigger challenge.  

Summer brings higher temperatures and any heat makes a saw fickle.  Also, high temps on hydraulics is not good.  We had to run a cooler to keep hydraulics at a decent operating temp.

Saws generally run better on the first cut.  It has more to do with a sharp saw than being cold.  I only ever saw one mill that ran water on the saw.  It isn't necessary, and I would look for the reason the saw gets hot before running water on it.  A good way to ruin a saw is to get it hot, then throw water on it.  You'll end up at the saw shop getting the saw hammered.   

[mike_belben]

Thanks for that info ron  :laugh:

[bandmiller2]

As Ron has alluded to saw are extremely sensitive to heat. Even a small piece of bark rubbing agents the saws plate is enough to disturb the tension. The saw is the primidone in the mill, and must be treated as such. There are two kinds of hammer smiths the ones that treat it as a dark art and have learned it by wrote, not fully understanding it, just cause and effect. The other understands the physics and why they do as they do. Even the smiths anvil must have a good foundation not set on a bouncy wood floor. To complicate matters not all saw are the same temper some like my old Diston are softer. Frank C.

[bandmiller2]

Ron, have you found you can get a good idea of a saws tension by shaking it.?? By shaking I mean saw standing vertical on a wood floor off the arbor and the top moved back and fourth. Some feel floppy others stiffer. It really helps when setting the saw guides to have something white under the guides to see the gap when running. A smooth piece of board sprayed white, be careful not to let the saw catch it, keep it low. Frank C.

[Ron Wenrich]

I've never found a newly hammered saw to be floppy.  I know new saws are stiff, as we bought several.  We ran left handed mills and there are very few in the area so there aren't very many good used saws for a left handed mill.  

Where the stiffness has to be is mounted on the arbor.  Bad collars won't do much for a saw whether its stiff or not.  A stiff saw will run better, but eventually you'll have problems.  I think bad collars have more to do with poor saw performance than not.  

As for setting guides, I set them with the log side being pretty tight, nearly against.  The board side being a little more open seemed to work okay.  Running at 700 RPM is a bit different than running at 540.  I never had any problems with seeing the light.  A white board would help, but the abrasiveness of sawdust will blow holes in metal, so I imagine a board wouldn't be white for very long.

[Bandtocircle]

Turned out saw was cutting deep on the log side because of excessive lead almost 1\4 and also rust in saw guide area on blade was eating oak guide , replaced with phenolic for now running true. Thank you for your in depth reply