Making ends square on cylinder

[Craig D Peltier]

My dad has a sono tube that either 10 or 12 inch by about 40 inches. Both ends are out of square? How do you take a measurement to make a line around one end to cut it assuring thats its level?
He has a band saw but it may be only 10 or 12 inch. I believe the tube is 10 inch. He also has a TS and jig saw and skill saw.

Thanks

[Steve Roxberg]

Place a mark on the tube that will mark a starting point.

Wrap a piece of poster board around the tube. The poster board will allow you to square the line you draw by lining up it's edges. Then draw your line.

I am using this method on 6" spiral with very good luck.

To cut the spiral I'm using a metal cutting blade in an 4 1/2" angle grinder. It allows a fairly straight cut.

Worth a try, but it will not be perfect if that's what you need. Easily would be very close though.

[Craig D Peltier]

Place a mark on the tube that will allow you to cut it square.

Wrap a piece of poster board around the tube. The poster board will allow you to square the line you draw by lining up it's edges where they meet have going around the tube. Then draw your line.

I am using this method on 76" spiral with very good luck.

To cut the spiral I'm using a metal cutting blade in an 4 1/2" angle grinder. I allows a fairly straight cut.

Worth a try, but it will not be perfect if that's what you need. Easily would be very close though.

Thanks thats slick.

[Ken Fitzgerald]

Craig....I have a plastic ruler that's about 24" long and 2 inches wide by about 1/16" thick. I wrap it around a cylinder and over lap itself keeping the sides even. Similar to the poster board described above. Any thin straight edge that can be bent around the cylinder will work.

[Kevin Groenke]

Make a v shaped sled to use on the tablesaw. All you need is 4 pieces of sheet stock.

Butt join (screw, brad nail or staple) two sheets ~ 6"x24" on the long axis.

Use a jigsaw or bandsaw to cut a 90 degree V in a couple pieces of 3/4" sheet stock ~6"x9". Size this piece of stock so the bottom of the V is 3/8" from the edge of the sheet.

Put the boards with the V cuts out of them into the tablesaw's miter slots. Lay the joint of the two long butt joined pieces in the bottom of the Vs and and screw them together.

If you want to spend a bit more time on a nicer jig, miter the edges of the V setions so that the sit flat on the tablesaw top as in the attached illustrations.

To make a cut: raise the tablesaw blade so that it is just higher than the bottom of the sono-tube resting in the V sled. Turn on the saw. Carefully slide the V sled into the spinning blade. Hold the sono-tube firmly in the V sled to resist the tendency of the spinning blade to make the tube rotate. Now while holding the sled in position, rotate the tube in the sled. Pay particular attention to rotate the tube in the opposite direction of the spinning blade so it doesn't start spinning. Rotate the tube 360 deg and you've got two pieces. Depending on the lengths of tube you need you should be able to clamp a stop onto the sled itself or use the rip fence with a auxiliary stop block in front of the blade.

g'luck
kg

btw, this is also a great sled for cutting spline joints in mitered boxes.

It should go without saying that this a somewhat unconventional and potentially dangerous operation to attempt with a tablesaw. Do not attempt without a thorough understanding of the inherent risks and a healthy dose of respect for the equipment.

[jacques nolin]

i keep an old 4" sanding belt around just for stuff like that it wraps around nicely and once it overlaps you have a guide for your mark hope this helps

[William OConnell]

Heres a picture of how I do it. It works like a charm
http://www.woodworkslive.com/index.php/topic,7796.0.html

[Charles Wiggins]

Craig....I have a plastic ruler that's about 24" long and 2 inches wide by about 1/16" thick. I wrap it around a cylinder and over lap itself keeping the sides even. Similar to the poster board described above. Any thin straight edge that can be bent around the cylinder will work.

Craig,

Ken is on the right track. I used to do sculpture out of scrap metal cylinders, and a friend who had worked as a pipe-fitter showed me the same trick the Ken describes. As long as your cylinder is basically true (as sonotube usually is) any flexible straight edge will do - but the wider the better. I have a piece of thin spring metal I use that's about 4" wide.

Of course cutting the tube is another issue. Not quite sure how I'd approach that.

The v-sled idea might work, but the problem I see is keeping the tube in the same plane while you rotate it through the blade.

[Craig D Peltier]

Very nice there seems to be alot of objects to use but all done the same way.
Also thanks for the explanation of the v sled and diagram, that was cool.

[Bruce Pennell]

My 4" x36" welders wrap was a whole $9 a few years back. Works great for getting a straight line. If you ever burn metal or work with round stock its a great tool. I use it mainly for cutting pipe true with my plasma but more than once on wood rounds too.:D