Problems cutting circles on a bandsaw

[Anthony Whitesell]

I need to cut down some logs for bowl blanks for my father. He would like to saw the log in half then lay it sawn-faced down and cut the largest circle I can from it. So if the log was 12" diameter, I should end up with a 12" diameter circle 6" thick in the middle.

Sawing the log in half has not been a problem. Cutting the circle has been problematic. I made a sled with a pivot point and a stop on the table. I slide the log in straight until I hit the stop and then rotate the log to cut the circle. Or at least that's the theory. The problem is that I get HUGE blade deflection and the log becomes more difficult to cut. I think it has something to do with where the pivot is in relation to the saw blade, but I've tried moving it front and back and can't seem to find a sweet spot, if there is one. Any ideas, where I am going wrong?

[Prashun Patel]

I've been going through this myself.

What's the tooth count on yr blade and what's the thickness? Higher tpi can clog easy. I have a tough time navigating a blade more than 3/8" around curves less than 5".

I was also able to increase my 14" saw's ability to plow through green wood by operating at the lower speed (1750). I get less slipping and better power.

At any rate, cutting bowl blanks into perfect circles - especially from green logs - is unnecessary. You can just trace the circle on the bark (take care to mark the center) and then cut it into an octagon. The lathe will make it round easily from here.

If you feel like it, you can even cut the corners off the octagon with 8 mini-passes.

[Anthony Whitesell]

I have the G0513X2 saw, I think I was using the 3/4" 3tpi because it was on their from cutting the log in half. I have to 1/2" blades. One I think is 6 tpi and the other 10tpi, maybe. I also have a 1/4" 14 tpi all timberwolf. Plus I have the stock 1/2" blade that I have been using when I need to abuse a blade (like cutting scraps to fit into the scrap bin for the fire).

My father has a small lathe . He said it was murderous to try to round off the blanks on the lathe between the sharp corners and the off-balance weight. He said what I have provided him so far was a tremendous improvement and help. Then proceeded to drop of another bunch of logs.

[Prashun Patel]

Yeah, you have PLENTY of power for this. Your blade is the right tpi, but the 3/4" might just be too much for cutting a curve. Might yr blade be dull?

A narrower, 3tpi blade will be easier to negotiate.

[Anthony Whitesell]

The 3/4" blade is the wider kerf than the 1/2" blades. I'll try them plus anything else we can figure out.

[Kyle Iwamoto]

If it's for a lathe, just free hand it. I made round templates from those brown folders, and screw it on top of the log. Just sort of follow the paper circle on the saw. As long as it's close, it will be easy to turn. Plus, you'll have a hole in the center for a reference.....

[Ken Garlock]

Hi Anthony.

Yes, I had similar problems.

The most important part of building a circle cutting jig is: the cutting leading edge-point is exactly in alignment with the pivot point of your jig. You want the blade to cut when it is exactly tangent to the circle, id est, perpendicular to a radius drawn from the pivot point to the leading edge of the blade.

Second, make sure you use the same band saw blade tension you used when you built the jig. To keep from dragging out the tension gauge all the time, I put a piece of blue tape on the tension wheel when the blade was properly tensioned. Then between uses, I turn the wheel loose about two turns.

IF it were me, I would use the Bill Grumbine solution. Scribe the desired circle on the face of the blank, and just free-hand trim the log to a little larger than the circle. Then go to the lathe, and grab that big thing called a roughing gouge. :)

As always, my recommendations are worth the price of admission.

[Ruhi Arslan]

Higher tpi can clog easy.
So what tpi one would choose for this kind of cut? You have to cut through thickness varying from nothing to 6". If I understand correctly there is a "recommended" tpi based on the thickness. :confused:

[Prashun Patel]

low tpi cuts more efficiently, but rougher. I have not resawn dry lumber, so I'm not the person to ask about that. But as far as green log cutting, there is night and day diff between low and high tpi for me.

[Anthony Whitesell]

But that wasn't the blade I was using.

Perhaps I should have said "when I don't want to take the chance of ruining a nice Timberwolf"

[Ken Fitzgerald]

I do as Ken Garlock suggests.

Use a pattern....mark it on the bark and freehand it.

Keep in mind, the wider blades will not EASILY cut smaller diameter circles and are more difficult to tension correctly.

[Van Huskey]

In general you would want to be using a 1/2" 3TPI blade for this. The blade needs a decent amount of set for the green wood, which generally means do NOT use a Woodslicer or any of the other hardened spring steel blades from the meat cutting industry. In the end it sounds like a blde and/or tension issue.

[Curt Harms]

get one of these:
http://www.highlandwoodworking.com/woodturners-bandsawblade.aspx
supposed to work well for roughing bowl blanks.

[Van Huskey]

get one of these:
http://www.highlandwoodworking.com/woodturners-bandsawblade.aspx
supposed to work well for roughing bowl blanks.


If he is doing small bowls (I didn't ask) that is exactly the type of blade he is looking for, low tooth density and large tooth set. Given the gauge of that blade I would suggest tensioning one size up ie: for this 3/8" blade tension it at 1/2" to get the proper tension. If he is doing larger bowl blank I still think a 1/2" blade with significant set is the way to go.

I have a feeling the problem is the combination of the set of his blades and the green wood.

[Tom Hammond]

I think I'd just cut it into an octagon with a miter saw, then knock off the excess freehand at the band saw. Actually, you could 22.5 your miter saw and give it 16 sides. That should be good enough for rough turning to complete the job. I really dont like doing this kind of thickness at the bandsaw.

[Peter Quinn]

I need to cut down some logs for bowl blanks for my father. He would like to saw the log in half then lay it sawn-faced down and cut the largest circle I can from it. So if the log was 12" diameter, I should end up with a 12" diameter circle 6" thick in the middle.

Sawing the log in half has not been a problem. Cutting the circle has been problematic. I made a sled with a pivot point and a stop on the table. I slide the log in straight until I hit the stop and then rotate the log to cut the circle. Or at least that's the theory. The problem is that I get HUGE blade deflection and the log becomes more difficult to cut. I think it has something to do with where the pivot is in relation to the saw blade, but I've tried moving it front and back and can't seem to find a sweet spot, if there is one. Any ideas, where I am going wrong?

Timberwolf makes blades for working green wood with low TPI count and more set, also big gullets for clearing those sticky plugs of dust that develop. I'd suspect that your primary problem is the blade, not the jig. Check the Suffolk Machine website for info on green wood blades and sawing green lumber.

[Anthony Whitesell]

Sorry, no miter saw...yet. 1) Install new electrical service, 2) Install new DC taking up room in the shop, 3) Buy Miter Saw (I'm liking that new Bosch one)

[Anthony Whitesell]

Timberwolf makes blades for working green wood with low TPI count and more set, also big gullets for clearing those sticky plugs of dust that develop. I'd suspect that your primary problem is the blade, not the jig. Check the Suffolk Machine website for info on green wood blades and sawing green lumber.

Funny thing is that I don't have a problem with the resaw step, just the circle cut. The blade pushes away from the pivot as I rotate the piece until I can't rotate it any more. At that point the blade is under some serious side load/deflection.

[Thomas Delpizzo]

I agree with Kyle; why bother cutting it into a circle. Just cut a slab, throw it on the lathe and cut it to shape there! Just my $.02

[Alan Schwabacher]

If the blade pushes away from the center, change your jig so it stops sooner as you push the center forward. If you move it too far, the blade should deflect in the opposite direction. A 3/4" wide blade is not ideal for cutting circles, but should work to some extent.

The Highland woodworking woodturner's blade would be a better choice. It's a 3/8" wide 3 TPI blade with extra set for a wide kerf.

http://www.highlandwoodworking.com/woodturners-bandsawblade.aspx

[Van Huskey]

Funny thing is that I don't have a problem with the resaw step, just the circle cut. The blade pushes away from the pivot as I rotate the piece until I can't rotate it any more. At that point the blade is under some serious side load/deflection.


OK, first proper tension. Try cranking it up one blade size higher on the scale.

2. make sure the upper guides are as low as possible and the lower guides (if adjustable) are as high as possible

3. Not knowing what guides you have it is hard to give exact advice but you want to make sure they are set correctly.

4. I still think you need to address the blade, you may be asking the 3/4" blade to turn to tightly, 6" radius is right on the edge of 3/4" blades ability PLUS you are cutting green wood which has the tendency to close kerf which reduces your turning radius. 1/2" blade with an agressive set is the largest blade I would use for your task. With this in mind it should be clear why the 3/4" blade is working fine for resawing the blanks but not roughing them out.

5. I gotta say for me the miter saw is about the last tool I would use for this, this is definately a bandsaw job. Most guys/gals that turn exclusively will have 2 machines in their shop, a lathe and a bandsaw.

[Anthony Whitesell]

I fairly sure that I have items 2 and 3 covered. As for the blade tension, I can dial it up more, but to even get the 3/4" blade to stop fluttering, the tension is off the scale. Based on that and #4 I'll try the 1/2" blade.

Many have mention Highlands Green wood blade, and I'd like to try a wood slicer blade as well.

[Prashun Patel]

The Woodslicer blades are not recommended for green wood because the tooth set is so slight. They are designed for resawing and minimizing waste. The green wood blade is designed for evacuating the wet sticky chips from the kerf.

A 17" saw should be able to tension a 3/4" blade properly. I wouldn't trust yr scale. Yr manufacturer should have instructions how to reset the scale. I never trust mine anymore...

[Myk Rian]

The scale is a REFERENCE point. Nothing more.
A short or long blade will throw it off.

[Mike Konobeck]

For the money this is a really cool product. I struggled. Used everything from homemade jigs to a few other crazy solutions on the router table. This was easily the best solution. The key is that it keeps the entry of your cut in line with the pivot point. Someone else mentioned that so sorry for the repeat but it makes such a huge difference. Also, as people have mentioned, I would stay away from 3/4" blades on a 12" circle. Use a 1/2" or less with an aggressive tooth. I think there are guidelines in the directions that came with it.

http://www.carterproducts.com/product.asp?product_id=502&cat_id=76

Carter also released something called the "Blank Creation System". I might give it a try. Always a sucker for new tools.

*No affiliation with Carter Products. Just happy with their circle jig.

[Van Huskey]

The scale is a REFERENCE point. Nothing more.
A short or long blade will throw it off.

The first part I absolutely agree with, it would be impossible for a single mark on the scale for a blade size to be accurate since bi-metal and carbide blades need more tension to work correctly than spring steel and carbon blades for example. It really becomes a feel issue particularly if you accept Duginski's assertion that BS tension gauges are not accurate at wood cutiing tension levels. Though he does suggest just using the gauge, which in general I do unless I have a dulling blade or a bimetal or carbide tipped blade all three of which I increase tension on above what the scale indicates.

The second sentance I don't agree with, obviously if the blade is outside the proper range for the saw you may not be able to get the blade on the wheels OR you may not be able to get it up to proper tension as the saw runs out of travel on the tensioning spring. However, if you take 2 blades one longer than the other but both within the manufacturers recommended range they should both read the same on the scale when tensioned properly. All the band saws I have used read based on the actual tension placed on the spring and are not referenced off the tension screw or the absolute height of the wheel. To show this just crank the "tension" up with no blade on, the indicator may wiggle a little but it won't move up like it does with a blade on it. There certainly may be some saws that have a different reference for reading but I have not come across them.

[Anthony Whitesell]

I looked at that system and used it as the basis for mine. The difficulty with both is to figure out where the pivot point should be in relation to the blade.

[Anthony Whitesell]

I don't want to use the woodslicer for cutting circles, but for resawing. Based on a few other things in life, it is sometimes more about finding what works best for you. IMHO, the Timberwolf blades I have are good. Maybe they would be better for me with a different TPI, or perhaps the Woodslicer would be even better. But I've not been able to justify spending all that shipping for one item.

[Van Huskey]

I don't want to use the woodslicer for cutting circles, but for resawing. Based on a few other things in life, it is sometimes more about finding what works best for you. IMHO, the Timberwolf blades I have are good. Maybe they would be better for me with a different TPI, or perhaps the Woodslicer would be even better. But I've not been able to justify spending all that shipping for one item.

Get a Kerfmaster from Spectrum supply, even with shipping it is about the price of the Woodslicer without shipping. Excellent resaw blade for either minimal waste or use on a saw that can't properly tension a wide bimetal or carbide blade.

[Brian Kincaid]

... Most guys/gals that turn exclusively will have 2 machines in their shop, a lathe and a bandsaw.

Don't forget the slow speed grinder / buffer. :rolleyes:
-Brian

[Van Huskey]

Don't forget the slow speed grinder / buffer. :rolleyes:
-Brian

I was thinking of true floor standers and not bench tops, guess more accurately it would be "if a person that turns exclusively has one floor standing saw it is probably a bandsaw". Since if you saw saws in general many/most probably have a chainsaw as well, one can get an awful lot of blanks for the cost of a couple of gallons of premix and a quart of bar oil.

[Anthony Whitesell]

My father doesn't turn exclusively but does have a lathe and I have the bandsaw. Well actually he has a Craftsman tri-wheel 9" bandsaw. Does that count as a real bandsaw or just a PITA?

[Anthony Whitesell]

I was thinking of true floor standers and not bench tops, guess more accurately it would be "if a person that turns exclusively has one floor standing saw it is probably a bandsaw". Since if you saw saws in general many/most probably have a chainsaw as well, one can get an awful lot of blanks for the cost of a couple of gallons of premix and a quart of bar oil.

That's my father's plan.

[Gary Herrmann]

FWIW, I've got a 3/8" 3 tpi blade on my BS. When cutting up logs into bowl blanks, I mark out a circle and cut to the line. As has already been stated, it won't matter much for green wood. Even dry it's not too difficult to knock down whatever isn't perfectly round once on the lathe.

[Faust M. Ruggiero]

I just bought the blade recommended by Van. I used it this weekend and it worked well. I tried several others and was not happy. Green wood is difficult to cut on a band saw. The saw dust has a difficult time getting out of the kerf, and causes heat to build up. Circles are particularly troublesome with the wrong blade. Dirt in the bark plays havoc with the sharpened edges and generally dulls the blade quickly. Even worse is the fact that the face we leave when cutting the log through the middle is rarely flat. When we lay that flat on the band saw and begin to cut a circle, the blade begins to bind. That causes heat that can actually melt the tires on the saw.
fmr

[Josiah Bartlett]

Two more things that will help, in addition to the blade:

1.) Remove the bark before sawing, so the entrapped grit doesn't wear out your blade as fast.

2.) Joint the sawn face of the blank flat, or screw it to a sacrificial piece of plywood. Then it will turn smoother on the pivot point, and this should help with the deflection.

[Lee Schierer]

You want the tips of the teeth at the tangent point. The center of rotation must be aligned with the tips of the teeth. Too far forward or back of the that point and the blade will wander in or out and bind.

Some additional thoughts:
If the blade is wandering outside your desired circle then your center point is behind the teeth. If the blade wanders toward the inside of the desired circle then the center point is ahead of the front of the teeth.

[dirk martin]

Gang, I do hundreds of these round blanks per year. Hundreds.
3TPI, 1/2" blade does the trick, with lots of tension.
I've cut blanks up to 17" thick, and 24" in diameter on my MM24 bandsaw and my Grizzly 24" saw.
Messing with a jig is just that...a mess.
Free hand it....but BE CAREFUL!

One hand will be acting as resistance behind the blade, and the other hand will be doing the pushing. That push hand is always pushing directly at the blade, which is very dangerous. Always use a push stick in that pushing hand. It will feel very awkward at first doing that pushing with a stick, but you will be suprised how quickly it will feel natural using the stick. And it's certainly worth taking the time...my brother in law lost his thumb doing exactly this, without a stick.

[Anthony Whitesell]

I didn't like that position much where I'm pushing my hand toward the blade, so I stand to the side of a saw. A circle is a circle no matter where you stand. The only disadvantage is that the off switch is no longer right next to me.

[Bill White]

Ken Garlock's advise is correct. Pivot point in line with leading edge of blade.
Bill

[Mike Cruz]

Here's what I did. Works perfectly!

http://www.sawmillcreek.org/showthread.php?t=147942

[Anthony Whitesell]

I have the same idea for the jig I built, but I still can quite find the right point to start the curve.

[Mike Cruz]

Anthony, when you place the wood chunk onto your circle jig, butt the chunk up against the blade and sit it down onto the post (or whatever you have to pivot the chuck around on. This method doesn't create a "perfect" circle for blanks, but I have had little blade deflection issues. Every once in a while, when I rush, or the chunk is cut really funky, it is more challenging, and you might end up with a flat spot, but I haven't noticed that to be a problem.