The Forestry Forum

Hi,
I bought my Lewis saw in the late 1980s. At the time the designer was trying and designing new circular saw blades to handle Western Australian hard woods. We were in a way guinea pigs and were given these different blades to try. The early blades were brazed on tungsten of, 6, 8 and lastly 4 teeth. The last blade I tried, was a replaceable tooth or "knock in" model. Our main problems were that the blades cupped through overheating. The mill delivers water directly onto the blade, but this still did not stop the blades cupping.

When cutting hardwood boards up to 200mm. To prevent overheating, I stopped doing this cut in one pass and tried two 100mm passes to cut the board through, this reduced blade cupping.

During all this time and after milling a shed full of boards, not one tungsten tip let go from the any blade.
I have recently resurrected the mill to cut "eucalyptus wandoo" floor boards. I ordered 2 new blades. The new blades use 4 brazed on tungsten teeth. The blades have sections of the saw face relieved, supposedly to limit heat build-up and relieve stress and cupping.
The first blade cut well, without overheating. After cutting 6-8 boards, the saw began a slight shudder. I checked the blade thinking it needed sharpening, but found a tungsten insert missing.
I replaced this blade with a new one. From here I increased cooling water, but after cutting only a few boards, 3 tips let go. This has happened again on another brand new blade from a different manufacturer.

The first 2 blade came from a supplier in Queensland and the last came from a different supplier from Victoria.
I have a repaired blade arriving this week and am hoping the tungsten tips will hold together. I am hoping it is a manufacturing problem.
I check the teeth for sharpness after each board and only sharpen when they lose their edge. I sharpen on average every 6 boards.
The logs have the bark removed and I have not found any metal in the boards, I look for it.
Has anyone else had similar problems with tips letting go and do you have an answer?
Thankyou    
DarkanJohn
N.B.   Another local farmer using a "knock in" toothed blade, had a tooth let go and it shattered his shin bone. Be wary of blades using knock in teeth or wear Kevlar pants.

I had a lot of trouble a long time ago with teeth regularly letting go.... I changed sawdoctors but I think the issue was with the guy using the wrong flux.... you can get cracking using phosphorous based flux on ferrous metals.

For all that if they are new blades off... I'm assuming Combined Saw and Knife in QLD, and Central Saws (Opteco) in Vic (there arent that many suppliers in 'straya after all) ... it won't be the braising job, and the chances of problems from both at once are like a billion to one.

Maybe check for backlash in your bearings.... it might be a shaft issue causing a flutter/wobble that is causing the saw to run eccentrically. And toss your saw retaining bolts out in case one has stretched. And have a look for imbedded stones in the bark of the log, only takes a grain of sand to chip out a TC tooth and then the next one gets damaged clearing the broken one out the cut. 

Be something like that...

Gday darken John,
I've got a lewi saw as well, brought in the mid or late 90's, wondering how you went with your issue?
Regards rog