exwestracer
11-04-2011, 02:32 PM
For those of you who've never heard of the book "Zen and the Art of Motorcycle Maintenance", it was more about a way of thinking than it was about being a mechanic...
Well, over the years, I've found the same thing applies to all those notches we have to make when building anything out of round tubing. So here goes:
Successfully notching tubing isn't about having super-expensive tools, or a computer program to draw the notches out (although those things never hurt). It's about imagination. Imagining yourself being the tube that is going to run through that saddle...[
When doing angled miter joints, one thing that REALLY helps is to cut the desired angle on the end of the tube FIRST. That way both notches are the same depth. If you are using a hole saw, this isn't AS important, but when laying notches out by hand, it is much easier to visualize the cut needed.
I teach (and do) it in 3 steps:
First, determine the axis of the joint (fancy way of saying which direction the notch needs to run on the tube) and cut the desired angle. A simple way to figure the angle is to lay the tube in place with a square cut end and measure how much "gap" is on the long side of the joint.
50995
Just make sure to leave enough extra tube on your initial (square) cut for angle and notch.
Second, mark depth of notch. This varies depending on what size tube you are notching ON TO. For equal size tubes, I use 1/2 diameter - 1/8". This will leave a little material at the tips of the notch so it won't vaporize when you weld around it. If you REALLY want to know how to calculate the notch depth for any combination of tube sizes, Google "arc sagitta" and learn the geometry. Once you've figured out how deep the notch needs to be, mark that depth on the tube along the center line of the notch axis.
Third, draw the notch profile right on the tube. Keep in mind that we need a ROUND shape, so if what you drew looks like this: \_/ .... wipe it off and try again. What you should have is a "smiley face"
50994
Once you have the shape correct as you are looking at it, turn the tube 90 degrees and you will see the straight line you need to cut to get the notch shape. This method works no matter what the miter angle is.
I do most all my notching with a suicide wheel (6"X.045 severing disc) in a Bosch angle grinder. It is the fastest, most versitile tool for the job...and I've tried them all over the years. For thin-wall 4130 tubing (.065 or less), I use a belt or disc sander.
Well, over the years, I've found the same thing applies to all those notches we have to make when building anything out of round tubing. So here goes:
Successfully notching tubing isn't about having super-expensive tools, or a computer program to draw the notches out (although those things never hurt). It's about imagination. Imagining yourself being the tube that is going to run through that saddle...[
When doing angled miter joints, one thing that REALLY helps is to cut the desired angle on the end of the tube FIRST. That way both notches are the same depth. If you are using a hole saw, this isn't AS important, but when laying notches out by hand, it is much easier to visualize the cut needed.
I teach (and do) it in 3 steps:
First, determine the axis of the joint (fancy way of saying which direction the notch needs to run on the tube) and cut the desired angle. A simple way to figure the angle is to lay the tube in place with a square cut end and measure how much "gap" is on the long side of the joint.
50995
Just make sure to leave enough extra tube on your initial (square) cut for angle and notch.
Second, mark depth of notch. This varies depending on what size tube you are notching ON TO. For equal size tubes, I use 1/2 diameter - 1/8". This will leave a little material at the tips of the notch so it won't vaporize when you weld around it. If you REALLY want to know how to calculate the notch depth for any combination of tube sizes, Google "arc sagitta" and learn the geometry. Once you've figured out how deep the notch needs to be, mark that depth on the tube along the center line of the notch axis.
Third, draw the notch profile right on the tube. Keep in mind that we need a ROUND shape, so if what you drew looks like this: \_/ .... wipe it off and try again. What you should have is a "smiley face"
50994
Once you have the shape correct as you are looking at it, turn the tube 90 degrees and you will see the straight line you need to cut to get the notch shape. This method works no matter what the miter angle is.
I do most all my notching with a suicide wheel (6"X.045 severing disc) in a Bosch angle grinder. It is the fastest, most versitile tool for the job...and I've tried them all over the years. For thin-wall 4130 tubing (.065 or less), I use a belt or disc sander.