Problem cutting blanks with my bandsaw

[Tom Porter]

I'm new to turning and want to turn some blanks with a bunch of green wood I was given. I built a simple circle cutting jig for my bandsaw, which seemed to work ok when I tried it out on some plywood scrap. However, when I tried it on the thick log sections, the blade kept binding. The saw is a older Central Machinery one I bought used and still had the blade which was on it when I got it. So I went out and grabbed an inexpensive 4tpi blade from Lowes (I'm ordering a Woodturners blade from Highland but had some time this weekend, so I figured the blade might not be quite up to the task but at least might make it through a few blanks while I'm getting better at it). I started on my first blank and it worked great for about 30 seconds, getting about halfway around the blank pretty smoothly but then bogging down. So I'm wondering what the problem is. I've done some searches here and several indicate that the tension on the blade may not be tight enough. I had set the saw up following instructions I found here (which were very helpful) but there wasn't much to indicate the tension. There's a little gauge on the back of the saw for tension but I gather those are pretty inaccurate. Is tension the likely cause? If so, how can I tell how tight to make it? As I said, I'm pretty new and want to be careful to not damage the saw or me.

Any thoughts?

[Lee Koepke]

I am not an expert, but the blade is likely a large part of the issue. Once you get the woodturners blade from highlands, you should notice a difference. I am due for a replacement, so i struggle thru cuts.... those blades are meant for cutting green wood on a curve. I dont use a jig, I just freehand mine.

[Bruce Pratt]

Several possibilities: 1) What size of blank are you trying to cut? Larger blades, e.g., 5/8 or 3/4" will not cut small circles as the back edge of the blade binds in the curve, 2) in wet wood, the kerf can close up behind/on the saw blade, as tension is relieved within the wood. As practical solutions, for the first possibility, just make a series of straight cuts, i.e., shape your blank into an octagon/decagon, which will approximate a circle. You can round it from there on the lathe. If the latter is the problem, make a series of radial cuts from the edge of the piece just up to, but not touching your circle. When you cut the circle, the radial cuts will allow the wood to flex and not bind up the blade.

[John Thorson]

The Highland Woodworking Woodturners bandsaw blade cuts green wet wood very well. I would look for a 3/8 to 1/2 inch 3 TPI alternate set with raker blade, this type of blade works great in green wood for most of us cutting bowl blanks.

[Scot Roberge]

Tom, you might also give it a try without your circle cutting jig. Depending on the size of the log, your cut is going to go through several changes in grain direction as you make your way around the circle. I find that the blade cuts pretty true when cutting across the grain and with the grain, but when cutting diagonally across the grain the "lead" on the blade has to be changed (sometimes quite radically) to stay on the circle. Make sure your blade is not being deflected by a diagonal grain situation that is causing it to bind.

[Dan Forman]

It the flat surface of the log you are cutting isn't truly flat, say if one corner is higher than the others, it will cause the blade to bind when the blank is being turned, as it changes the orientation of the piece to the blade. Hope that makes, sense --- it's as if you were resawing a board and then tilted it to one side or the other, the blade will bind in the slot it is cutting.

Dan

[Reed Gray]

Most of it has been covered. First, the bottom of the blank needs to be pretty much dead flat. Not too easy to do with a chainsaw. Generally you rip the log section down the center with a chainsaw, they put it on the bandsaw to round it out. You can rip a log down the length on your bandsaw if you do it with a straight edge, or even chalk line, or I have heard of making a sled to hold the log steady. Problem here is most logs aren't straight, so again they can rock and roll on you, but this can give you a more straight log section. When I use the chainsaw, I mark plumb/straight up and down lines on both ends of the log, and use the chainsaw to mark the line across the top, then follow the line down the face of the log. This generally gets it close. If the blank rocks at all when you are cutting the circle, that puts the kink in the blade. Some times it just jams up, some times it destroys the blade. You can cheat a little bit by cutting off the corners first making an octagon, then try the circle. You can use a round template on top and eyeball it to the template, making sure to keep the part near the blade flat on the bandsaw table. Some times you can true up the flat surface of the blank with an axe, plane, chisel, hand planer, or other tools.

The blades that come on the saws are junk. My favorite blade is the Lennox Diemaster Bimetal blade. They cut straighter and longer than any other blade out there. There is a long thread on them if you search for it here that I started. Most of the time you want 3 tpi with a set to the teeth so they can clear the shavings. I prefer a 1/2 inch blade. You can cut a 6 inch diameter circle with it. A dull blade will make things a lot worse, no matter how flat your log face is. Some can be sharpened (the Diemasters can be sharpened a number of times). Also a dull blade is very dangerous as you tend to push harder.

Try to find the nearest club to you. You can get a lot of help that way, and save yourself a lot of time trying to figure things out.

robo hippy

[Tom Porter]

Thanks for all the helpful comments. There is a lot there that I think applies. I'm certainly looking forward to the better blade. And the points about the piece rocking are well taken. I've tried to get them as flat as possible but that may be contributing to the problem. The wod is 4-5 inches thick at the thickest part and the kerf doesn't seem to be loading up and I'm not trying too tight a circle. I think the diagonal grain issue may be a contributing factor. My guess is that I'm looking at collection of problem rather than a single glaring culprit.

Since I'm new at trying to set up the saw and have little faith in the gauge on the back of the saw, I'm still concerned about the tension of the blade. Is there a good way to know if the blade is taut enough?

[Jim Kirkpatrick]

I guess everyone has there own favorite brand. I previously had a 1/2" Woodslicer from Highland Woodworks. Not a blade for cutting curves. I cut out a blank freehand with it and the result was about as round as a stop sign. (outer cut). I just recently upgraded to a Timberwolf 3/8" alt tooth blade from Suffolk Machinery. One that is designed for cutting bowl blanks. Man oh man, what a difference! Best $20 I ever spent. I recut the same blank freehand and look at the difference on the inner cut.

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[Thomas Canfield]

Check to see that the pivot pin is located at the front of the blade tooth. If it is not, the blade will tend to drift. Also make sure the pin and sled is held. My circle cutting jig has a sled to allow me to push the wood into the position to start the circle and not rely on a tangential start. There is a stop to position the pin at the blade front, but there is still some drift occurring due to the bottom not being flat or the teeth on the outside dulling faster. You can always go with a cardboard template tacked to the blank and cutting by hand without jig and that will usually work even with a duller blade. The larger kerf with the Highland Woodturner blade does help with green wood.

[Rob Price]

I'll add the Carter green wood blade to the mix of recommended blades. It's a bit thicker, 3 TPI, 3/8 blade. I've been very happy with it.

[Jeff Folkert]

No matter what blade you end up with, make sure it as very few teeth so the blade has a place for the sawdust to collect and get removed from the cut. Wider kerf blades are best for green wood especially and the blades from the saw manufacture are junk and many of the big box stores carry low quality bladed. It is worth the extra money to buy a good quality blade from a known reputable manufacture. Typically when a blade binds it is due to too many teeth, trying to cut too sharp of a radius for that blade or a bottom that is not flat causing the binding.

Jeff

[John Beaver]

I think it's been mentioned, but make sure that the pivot point is lined up perfectly with the front edge of the blade. This is critical.

I generally find it easier to just mark the blank and do the cut freehand. This way you can make adjustments if the blade starts to drift.

[Pat Scott]

As for blade tension, a good rule of thumb is raise the upper blade guide 6" to 8" above the table. Push against the side of the blade with your finger using slight pressure, and when you have the right amount of tension the blade should deflect 1/4". You can set a machinist square or something similar against the blade to see/measure the amount of deflection if you want. This is more a "feel" type of adjustment as of course if you push too hard you can get too much deflection, and if you don't push hard enough the blade ends up too loose. Just use slight pressure.