Warped bandsaw blade?

[Winston Chang]

I recently purchased a 10" bandsaw (Rikon 10-306), and along with it, a Starrett blade, a 'Duratec SFB 70-1/2" x 1/4" x 4tpi Skip'. I first set up the band saw with the stock blade (I think it's a 3/8" blade), following the instructions from Alex Snodgrass's "Band saw clinic" video and managed to get a reasonably good quality cut. Bear in mind, though, that I have little experience with band saws, so I don't have a good point of reference.

I swapped out the stock blade and installed the new Starrett blade, then tuned it up again, but the cut quality ended up being much worse. When I turn the wheel by hand, I can see that there's a region of the blade that wobbles off to the left, when viewing the blade straight-on toward the teeth. The wobble is consistent with a particular region of the blade, (the deflection occurs once per revolution of the blade, and not once per revolution of the wheel).

I took off the blade and set it flat on a table, and the same region that wobbled to the left didn't sit flat -- it was raised off the table, as you can see in this picture:
bandsaw-blade.jpg

It makes sense to me that if that part is lifting off the table, then when viewed head-on, it would also be slightly deflected to the left. But I don't know enoug

Here's what the cut looks like, in a piece of wood that's about 1/4" thick:
bandsaw-new-blade-cut.jpg

For comparison, here's what the cut looks like using the stock blade:
bandsaw-old-blade-cut.jpg


Is the blade defective? Should I take it back? I'm pretty disappointed with the result, especially since I was told it was a high quality blade, and I'd expect as much from a Starrett product.


I'm also wondering, how clean of a cut can I possibly get if the band saw is really tuned up well and I have a good blade in it? I can see a little runout in the upper wheel when I turn it by hand. I managed to get a dial gauge to ride on the saw blade on the wheel (though at an awkward angle) and the range is .006". I think that if the dial gauge was perpendicular to the blade, it would measure significantly more runout. Here's a picture -- note this is with the stock blade):
bandsaw-wheel-runout.jpg

[justin sherriff]

I am new to bandsaws too but that blade is defective take it back if you can. Is that where the blade was welded?

[John K Jordan]

Sounds to me like the blade is defective; I'd return it.

How smooth the cut is depends on the type of blade, the TPI, the set of the teeth, and the speed of the blade through the wood. Wider "resaw" blades may cut cleaner but a small saw might have trouble tensioning. I mostly use 1/2" 3 or 4 TPI Lenox spring steel blades since I cut a lot of thick, green wood for turning blanks. The cut is usually not too clean but that doesn't matter for this use. I have some 3 TPI carbide blades that cut much cleaner. Kind of expensive, though.

If cutting thin wood you might want to try a blade with more teeth per inch.

How straight the cut is depends on other things.


JKJ

I recently purchased a 10" bandsaw (Rikon 10-306), and along with it, a Starrett blade, a 'Duratec SFB 70-1/2" x 1/4" x 4tpi Skip'. I first set up the band saw with the stock blade (I think it's a 3/8" blade), following the instructions from Alex Snodgrass's "Band saw clinic" video and managed to get a reasonably good quality cut. Bear in mind, though, that I have little experience with band saws, so I don't have a good point of reference.

I swapped out the stock blade and installed the new Starrett blade, then tuned it up again, but the cut quality ended up being much worse. When I turn the wheel by hand, I can see that there's a region of the blade that wobbles off to the left, when viewing the blade straight-on toward the teeth. The wobble is consistent with a particular region of the blade, (the deflection occurs once per revolution of the blade, and not once per revolution of the wheel).

I took off the blade and set it flat on a table, and the same region that wobbled to the left didn't sit flat -- it was raised off the table, as you can see in this picture:
bandsaw-blade.jpg

It makes sense to me that if that part is lifting off the table, then when viewed head-on, it would also be slightly deflected to the left. But I don't know enoug

Here's what the cut looks like, in a piece of wood that's about 1/4" thick:
bandsaw-new-blade-cut.jpg

For comparison, here's what the cut looks like using the stock blade:
bandsaw-old-blade-cut.jpg


Is the blade defective? Should I take it back? I'm pretty disappointed with the result, especially since I was told it was a high quality blade, and I'd expect as much from a Starrett product.


I'm also wondering, how clean of a cut can I possibly get if the band saw is really tuned up well and I have a good blade in it? I can see a little runout in the upper wheel when I turn it by hand. I managed to get a dial gauge to ride on the saw blade on the wheel (though at an awkward angle) and the range is .006". I think that if the dial gauge was perpendicular to the blade, it would measure significantly more runout. Here's a picture -- note this is with the stock blade):
bandsaw-wheel-runout.jpg

[John TenEyck]

The first cut quality photo confirms to me the blade is bad. I really like Starrett blades, so don't give up on them, just get another. No one welds them perfectly every time. The second cut quality photo is much more typical of what you can expect from a 3 or 4 tpi blade. If you want something smoother you could go to a 6 tpi blade if you are cutting thin stock like 3/4" and thinner, but that's not a great choice for anything thicker. If you want a smoother cut on 1" and up you could consider a variable pitch blade, like a 3-4. The Woodslicer is well regarded for exceptionally smooth cuts. The downside of that blade is short life in hard woods. Carbide blades cut the smoothest and longest, but I doubt that's a possibility on your saw. In the end, a BS is not a tablesaw and you shouldn't expect the same cut quality from it.

John

[Al Launier]

I suspect that when the blade was welded one side was not fully up against the back-stop. This would cause the blade not to sit flat as shown in the first photo. I would suggest you bring it back for a new replacement, or have it re-welded.

[Winston Chang]

Thanks all for your help. I exchanged the blade for another one. The quality of the cut is better, but still not as clean as the stock blade.

From top to bottom: stock blade, original 1/2" Starrett blade, replacement 1/2" Starrett blade.

bandsaw-cut-quality.jpg



When I turn the wheel by hand and look at the blade head-on, I still see noticeable left-right motion of the blade.

For the first Starrett blade, I'm pretty sure each ridge corresponded to one revolution of the blade. For the new blade, it looks like there are twice as many ridges, so I think each revolution of the blade results in two ridges (I think I had approximately the same feed rate for both).

The wheel circumference is about half the length of the blade (~33" wheel circumference, 70.5" blade length), so you might think that the ridges are due to something with the wheels. But since the cut with the stock blade doesn't have ridges that are that large, I'm inclined to say it's the blade, not the wheels, that is causing the unevenness in the cut.

[John Lanciani]

a 1/2" wide blade is too much for a 10" saw, you'll never get enough tension on it to get decent results. 1/4" is ideal, and 3/8" is right at the limit.