Best way to square for mitre cut on round tubing

Date 12-10-2012 20:36

Look on page 80
http://www.mathey.com/pdf/catalogs/MD-Blue-Pipe%20Fitting%20and%20Flange%20Tools.pdf

You can also use a combination square with an adjustable center head. Once you determine where you want to make the centerline and mark as "top" with a center punch, you can use the centerhead level to make sure that "top" is still "top" when you flip end for end before you make your second cut. This way your second cut will be in the same plane as your first cut. Do this for all four pieces and your frame should be square and level.

By Waynelund (*)

Date 12-10-2012 21:57

Looked at D205 and may fit the bill. But it still relies on eyeballing the punched mark.

I'm thinking now of making a box out of wood, like an old fashioned miter box with clamp, thus cut one end and flip the box and cut pipe for second cut.

By jwright650 (*****)

Date 12-11-2012 13:56

OK you may want to use some machine shop fixturing if you need to be more accurate where you need to be within thousanths of an inch or within several decimal places of a degree.

But for general fitting purposes you can use the centerhead on a combination square and do some fairly accurate work.
I looked quickly on Youtube and found this series that really goes in depth showing all of the functions for the combination square, (you may get bored with this and want to fast forward to the interesting parts)...and demonstrates the use of the center head on a piece of pipe. We use this centerhead method on all of our structural pipe fitting.

http://www.youtube.com/watch?v=K7rItfydkPA

http://www.youtube.com/watch?v=5mzjD3ClfEY

http://www.youtube.com/watch?v=J-BEmr0-N1A

By Oneatatime (**)

Date 12-10-2012 22:22

http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&ved=0CFYQtwIwAA&url=http%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%3DIqTJRt7NdEw&ei=pWDGUI-0D47GqQGFkIDABA&usg=AFQjCNH0a9ivurEmXeYHmFRFcAqgkHPUyg

By yojimbo (***)

Date 12-11-2012 16:42

Wayne-
Sounds like you are asking for two different cuts. one a parallel miter cut, the second a parallel cope [fishmouth] for round tubing. For square or round parallel miter cuts the procedure I use is straightforward. Determine your angle of miter, set your chopaw fence to that angle and make the first cut. Endo the piece for the opposite end miter cut, set it in chopsaw then level two planes: first level the length of the material horizontally, then level the first miter cut vertically. This will produce parallel miter cuts in either square or round tubing. I use the seam of the pipe on round tubing as a general visual reference. Using the center finder and a punch mark as mentioned in another post will work as well but I find it too time consuming.

To make parallel copes for round tubing [fishmouths] I have built a jig to fixture the pipe. I use a Bailiegh TN 250 for cutting copes, it is similar to the Harbor Freight Joint Jigger in design except it is designed 20 times stronger, more accurate and durable at only about the same factor in price. Very nice tool, but even if you are using a less expensive hole saw fixture tool to do your cuts, the principle is the same for the parallel coping jig.

The cutting tool is mounted to a work bench. The jig is a clampable length of 5/8" X 4" flatbar with two lengths of 3/8" sq. stock welded to each edge to form a sliding track. Into the track is a length of 3/8" X 3" flatbar that will slide in the track. To that 3" flatbar is welded a pivoting device with a threaded adjustable rod to allow for height adjustment for different diameter round tube/pipe to get to center. At the top of the adjustablly threaded, pivoting rod a short length of 1 1/2" pipe. I am using this pipe diameter as an example, the short length of pipe simply has to match the material diameter you are working on. After making the first cope, endo the piece and align the cope with the short length of pipe on the threaded pivot. When it is aligned, tighten the hole saw tooling [in this case a radial vice on the Bailiegh tool]. Make second cope, it will align the copes parallel to each other regardless of angle of cope as the short length of material on the end of the threaded rod will rotate to match angle of first cope. It is difficult to describe in sufficient detail with words, a diagram would be more usefull, but if you have a lot of this kind of work to do this might give you a starting point for some ideas. If it's only a few cuts/copes go with a level and a center finder/punch mark.

By Waynelund (*)

Date 12-11-2012 17:04

Good points, thanks for your ideas.
A lot will have to do with the base plane from which all angles stem from, methinks. Have been thinking more on a modified kind of mitre box used in the woodshop into which to cradle the tubing to be cut, then flip the box over to mitre the other end of the tubing. If tuging is too long, then use two modified clamping mitre boxes to simulate the tube being square and thus able to simply flip tubing for accurate parallel faces to be welded into the perfect frame.

Will cut and paste your reply in my to-do list of experiments.... again, thanks!

Wayne in Chula Vista

By Waynelund (*)

Date 12-11-2012 19:23 Edited 12-11-2012 19:33

here's an idea for easing the pain of mitre and fishmouth on both ends of round tubing, short or long pieces;

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