Re: Blade tracking problem
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Hi all It's actually quite astounding that there are so many faults with these saws, and it's not?just one brand, it's all? of them. If they were making lathes no-one would buy them!?? Part of the problem is that there are so many adjustments that almost anything can be MADE to cut, but when it comes to cutting accurately these adjustments sometimes don't work. and you have to resort to drastic measures like Mark did. One way I've found to look at the wheel position and tracking is to use a bit of thin string (braided fishing line is ideal) instead of the blade.? Make a loop ~62" long (a bit smaller than the 641/2" std blade loop length so you can stretch it some when tensioning) and position it in the middle of the land?where the blade runs on the bandwheels.? Tension it up quite tight and see where it passes through the guides. It should be where the middle of the blade runs and not touching either side guide roller and should be clear of the back support roller by about 1/4".?? I bet you it's not!? Taking off one or both side guide rollers will show where the blade wants?to run. That's how I found where to silver-solder the bits,?to position the guide rollers, when making a new set of guides Like Mark found, if the rear support rollers are too far forward (esp the bottom one), the blade comes off, when you increase bow weight to make it cut quicker. This is because it's bending the blade across its 1/2" width and when the weight comes on, the blade pivots around the rear support roller and jumps off the bottom wheel (I use the saw with the head vertical and the viewer standing with the vice handwheel in front of them for any up-down/, back-forward bottom-top etc directions)? - jv?
On Sun, Feb 20, 2022 at 02:05 PM, John Vreede wrote:
Then the bottom wheel is moved in or out on the drive shaft to get it to also track <0.040" from its rim.? You do this by changing the length of the spacer between the bottom wheel and the gearbox out bearing.
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This is excellent information. I have a new saw (actually over a year old now) with some discrepancy between the ledge of the upper and lower wheels. if I remember right it's about .030" further out on the lower wheel and in my opinion it's not enough to worry about. I remember thinking the only way to fix this would be to move a wheel in or out but I wasn't really sure which wheel.?
I have something to add about blade tracking that is worth looking at. When I got my saw it seemed like everything was set up and ready to go so I started using it without making any adjustments. Then I started increasing the weight (it was cutting very slow) and as a result the blade started falling off. Most often this mutilated the blade and made it unusable. After the third blade I realized I needed to take a closer look. I found what I thought was the problem and then confirmed this with other saw manufactures.
First, (as you said John) the blade tracking need to be set with the blade guides removed. Then when the guides are installed they should twist the blade along the center line without deflecting downward or to the left or right. Ideally the bearings in the guide should only contact the back of the blade while cutting although it needs to just barely kiss the bearing all the time. Very slight pressure is also fine.?
The problem on my saw was that the blade guides were deflecting the blade downward nearly 3/8". With the guides set correctly the saw would not cut deep enough. The cover near the top wheel hit the base. Even when I removed blade cover the upper frame hit the switch housing before completing the cut. After doing a little research I realized my saw was defective. I looked at two other older saws that did not have this issue. I suspect this problem is a result of a bad setup at the factory. Maybe the pivot point for the head was not located correctly. In reality the pivot point on my saw needs to be dropped over 1/4".?
I ended up putting a 1/4" steel plate under my vise. This elevating plate raises the stock enough so that the blade can complete the cut without being deflected significantly by the blade guides. Since making this change I can increase the downward pressure to full. Sometimes the saw stalls but the blade never comes off. In fact, I have had the same blade on my saw almost a year now. It has cut a LOT of steel.?
I had a bunch of these elevating plates made (laser cut) and have sold over 60 of them (apparently quite a few saws have this defect). I currently have one plate in stock but if there's enough interest I can have some more made. When the price of steel went nuts I raised the price from $29.50 to $39.50 but honestly it's barely worth my effort. After the cost of steel, laser cutting and shipping I'm about $2 ahead. Let me know if your saw needs this plate. If there is enough interest I'll have more made.?
Mark
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John Vreede