Circles with the Band Saw from WoodCentral

The poster who started this discussion was attempting to achieve a technique -- cutting circles with his band saw -- and ran into some problems. He turned to fellow forum members for advice. - Editor

"I tried to cut circles on my band saw using a crude circle cutting setup. I tapped a short nail into a scrap and positioned the nail about 3 inches to the right of the blade. I fit a 6.5" square into the nail slightly off-center so the edge of the scrap was right up against the blade. Blade is 1/2", which is supposed to be able to cut a 3" radius circle. When I fire up the saw and start cutting, I systematically found that the cut would tend to spiral in, forming a spiral. When I got around back to the beginning and the 'circle' could release, I would see the band saw blade spring back to the left. I tried various things, like positioning the nail in line with the gullets, either along the direction perpendicular to my saw's lead line or just perpendicular to the blade. (The lead is about 3/8".) And the best I got was a circle where I only spiraled in 1/8" when I got all the way around. Again, the blade was pulled off-center by 1/8" by the jig setup. What is the explanation for this spiraling behavior? How can I get an actual circle?" - Adrian

A couple of respondents offered explanations. - Editor

"I think the main thing is to have the blade guides and your blade backup bearing just about against the blade, about a paper thickness away. Also, the pivot of the circle has to be right in line with the front edge of your blade, not a little in front nor not a little in the back. These are the main problems I found out that can really mess it up." - Larry

"Spirals are a sign that your pivot is too far in front of or behind the cutting point of the teeth. Ideally, the pivot should be exactly in line with the tips of the teeth; however, you may need to adjust this one way or the other to get a perfect cut due to the actual tracking of the blade due to tooth set or wear. I would also suggest a thinner blade. A 3" radius is pretty tight for a 1/2" blade. You may also want to round over the back edge of the blade with a hard sharpening stone so it can turn more easily." - Lee

And one shared experience. - Editor

"Attach a slide in the miter channel to a piece of plywood, then cut about one-half the way across the plywood. Clamp the plywood tight to the band saw table and then mark a 90 degree line using the cut in the plywood and the tip of the blade. I marked one inch increments down the line and drilled a 1/4" hole at each inch. I used a 1/4" dowel for the pivot. An adjustable pivot would be very much better, but I was only experimenting. I used this jig to cut a 16" round top for a Craftsman tabouret. As the others have said, the tip of the blade is the critical element. Get off on that and you'll have an interesting design, but you won't have a circle." - Clementine

The original poster came back with part of his problem solved -- and a new one created. - Editor

"It looks like the problem was saw setup after all. I was getting ready to do more test cuts when I noticed that the guide assembly was shifting on the shaft. I tightened it up and tried again, and the behavior was much better. The blade no longer deflects to the side. Instead, the saw jams up and the wood starts burning. That's what happens when the pivot point is misplaced. I tried placing the pivot point in line with the teeth tips and also in line with the gullets (relative to the saw's lead line), and it seemed like in line with the gullets worked a bit better than in line with the teeth. Now I just need to figure out how to secure my board with a nail through it to the saw without getting in the way of the 10-inch circle I want to cut. I realized that the simple clamp isn't going to do it. Or maybe I have to make a real jig." - Adrian

He got a suggestion for that problem, too. - Editor

"I`m happy to hear that you're coming along with your circles. Your circle table jig could be clamped down by making it longer and going past the blade to the other side of the band saw table and clamping it there out of the way of the circle you are cutting." - Larry

That worked! - Editor

"Your suggestion was helpful because I was trying to think of a way to secure the jig staying on the right side of the blade, so it helped me think in a different direction. I cut a notch for the blade out of a larger scrap of plywood and set a nail in place and got a decent 9.75" diameter circle. " - Adrian

Crib Builder's Question from WoodCentral

The starting question for this thread came from a future grandpa. He has the crib building in hand, overall, but wanted to know what to use to support the mattress. - Editor

"I'm starting construction design work on a crib. Basic design is chosen, but I've a question on mattress suspension. I know that I can get a steel spring platform ready-made, but am wondering if anyone has used a true platform instead. I can make a nicely rigid platform in MDF and then fix it to the crib ends with 'L' brackets bolted to threaded inserts or an inlaid steel bar drilled/tapped at intervals. Makes it pretty simple to change the height of the mattress as the child grows, and gives better support to the mattress." - Mark

Feedback came from others who have built this item before -- or were working on one. - Editor

"Kids weigh next to nothing. I can't imagine that it matters what is under the mattress. I always use a piece of plywood, but I didn't arrive at this choice as a result of any scientific investigation." - Bill T.

"I, too, have used plywood, varnished well so it can be cleaned." - Kneale

"I'm getting ready to start a baby set, too, so went looking at cribs-- pretty crappy stuff, including the chests, most especially the drawers! The style of crib my son and his wife are looking at had brackets and/or steel or hardwood rails attached to the corner posts running across the front and back that supported a sheet of MDF and the mattress. There was nothing running front to back at the ends (short sides) of the crib, however, so the thin (1/2"? 3/8" ?) MDF was already sagging there with nothing but the weight of the mattress on it. I imagine the sagging could be worse by the time the baby is ready to transition to the toddler day bed -- I'm making a 3 in 1 convertible bed. As I see it, an MDF board is definitely out. I will likely use support rails across the front, back and along both sides to support a sheet of good birch ply." - Alan

And the original poster announced his decision. - Editor

"Was considering MDF for the finished edge, but have decided to edge band good ply with hardwood to match the crib, then use some 1x1 angle iron on the short sides to take the hanger straps. Fixed rails (no drop-side) will be 30" tall, so I plan 5 positions spaced at 4" intervals for the height adjustment. That gets outgrown and Granpa'll be makin' a Big Boy/Girl bed anyway." - Mark