pipe miter

[ieezitin]

Hi guys.

I need to make a handrail so I need to miter the pipe to make the joints, in the attachment is a hand sketched Iso it shows my runs, angles of rise and angle of turn.

What is the formula to making a swing joint off set miter joint. I really want to make a template out of card so I can wrap around the pipe and trace the line to make the cut on the pipe.

Or is there a simple program I could use to get the same effect.


I than you in advance. Anthony.

 

[kustomkb]

Just input your variables, print the template and cut away!

http://www.ozhpv.org.au/resources/shed/tubemiter.html

 

[Tin Falcon]

Anthony: Has been a long day/week but If I am thinking clearly should not be a big deal . when you straight cut your included angle is 180 degrees so you cut 90 degrees to the edge right? and if you are doing a 90 degree angle you cut at 45. Those are the easy ones we are used to. but in your case you have an included angle of 144 so half of that would be 72 degrees . but you do not have that on your miter saw but 90-72 = 18 that you can cut on a saw try it on paper and see if it works.
Tin

 

[ieezitin]

Tin.
Your math is correct for a level miter, but I have a rise and angle projection together. I called that a swing joint( maybe wrong here).

In essence my y value from left to right on the sketch is 71.58* rise from level heading to z, my run is 64.875 then I hit my miter joint, then at the joint I rise 69.35* in z travel while 144* away from x value.

You think you have had a long week.


Anthony.

 

[gbritnell]

Anthony, your sketch is a little hard to follow. First off if you had an angle of 71.58* from the horizontal your line would be 18.42* from the vertical. Are you sure this is what you're asking because your sketch is nothing like that? Lets say that it's 18.42* from the horizontal for a distance of 64.78. Now, what would be the slope of the next pipe? Surely it can't be 69.35* from the horizontal because that would be 20.65* from the vertical. So let's say these numbers are also reversed. Now the second pipe is inclined from the first pipe by 2.23*, the difference of 20.65-18.42. Now we throw in this 144.0* number. I am guessing that you want a rotational angle from the first pipe to the second pipe of 180-144=36*. If all this is correct then what you have is a compound angle which is easy enough to solve if all the things I said are correct. If you could clarify your numbers we can help.
gbritnell

 

[Maryak]

Anthony,

Looking at your sketch IMHO the pipe only needs a 90 deg notch 2" long starting from the inner side of the bend at 54 deg and cutting 2/3 of the way through. Bend until the 2 inner edges of the notch mate. Check the 144 deg angle and when its correct tack the check again and if OK weld around and grind to suit.

Hope this helps

Best Regards
Bob

 

[tel]

This is why its sooo much easier to do hand rails on site. Get it close, offer it up, run the angle grinder thru, offer it up, nibble a bit here and a bit there and Bingo! It fits!

 

[HS93]

just out off interest how many people have seen handrails notched all the metal ones I have seen are mitred if they are notched they leave an open end .the uprights to them may have a notch.


Peter

 

[Maryak]

if they are notched they leave an open end
Peter

Where ? when its all welded up.

Best Regards
Bob

 

[ieezitin]

Gentlemen



This is a rolling off set, the miter has to do two functions swing an angle (off set) then roll up at an angle.

Allot of people have answered my question I thank them but all the answers I am getting is just for a general miter.

My first sketch has the wrong angles I have amended this with another sketch. All so read the drawing as an Isometric three dimensional.

I did not mean to complicate it its my fault for a bad drawing.

Thanks Anthony.

 

[mklotz]

I'm a bit puzzled about what you are trying to compute. Are you trying to compute the angle ABC? If so, it seems it's a simple vector dot product problem and I can help with that. I'll await your answer to my question before starting on the math.

 

[ieezitin]

Marv.

I got my math what I am asking is for a formula and or instructions to make a template to actually cut and miter the joint. As you see from my third sketch if I were to miter off the obtuse angle of 144* or acute angle of 36* split that in 2 that certainly will give me my correct angle. But because the pipe is on the rise from the starting point over its run its raised 20-½ inches which in essence draws in the second pipe finish point by so so inches.

I have scaled down and made a model with welding wire and it sweeps my end point back. Which it should,

I am not saying I am right here, It could certainly be me and I am missing something.

Refer to pipe lengths on second sketch

Again thanks for helping me Anthony

 

[johnthomp]

if this was a purlin on a traditional roof it would be called a compound mitre something ive only ever done by makeing a model in a shoe box with a bendy drinking straw as trial and error then copied the angles to full scale by makeing a mitrebox set at thr correct angle

 

[ieezitin]

John.

compound miter!!! that’s it that eluded me

Good advice on the shoe box theory I have done something similar with the welding wire, I have a go at the miter box.

There are little programs out there that will print out a template on paper which you cut up and scribe on the pipe, but there is none I know of the does a compound miter (rolling offset in pipefitting terms).

Thanks Anthony.

 

[gbritnell]

Hi Anthony,
Here's a PDF of your dimensions. I layed this out in projections as it will be a little easier to see than the math. The first triangle is in green with associated dims. The second triangle is in orange with assoc. dims. You will see that the final angle, in red, is 178.274*, or almost 180 degrees. This makes the 2 rises almost flat so in the top view you see an included angle of 144.00*. Divide that in half and you get 72.00*
George

View attachment PIPE RISE AND RUN ANGLE.pdf

 

[johnthomp]

just out of interest i figured an easy way to do this mitre i did it in wood coz i dont have a coldsaw blade for my mitre chopsaw but i drew the angles up the shed wall useing the good old marker then another set of lines exactly 2" paralelle with the original lines then where they all cross over at the point of the mitre it should look like a diamond and drew a line through this frome one point to its opposite and just set the sliding bevel to the new line giveing me the exact angle of the mitre without the use of any calculations and just takes 20 mins or so then transferred the angle off the bevel to the mitre box and off i went and had a perfect fit first time
this method is how its been done in the joinery trade for any handrail or bannister rail and us joiners are still in the tudor age with working things out like this because its a method that works and has never had any need to change it ive seen joiners straight out of college and university try and work it out on cad and with all these crazy equations and never get it right
this is why i think company owners have got it wrong by takeing on lads with nvq's comeing out of their ears rather than lads like me who just do the job right it really pees me off getting told im not getting the job coz i have no papers to say i can do it
hope this revised method helps
best reguards john

 

[Bill S]

Anthony,

If you are looking for a pattern to wrap around the pipe, use parallel line development. I'm a bit busy now, but I can sketch up a sample a little later to get you going.

Bill

 

[ieezitin]

George.

Thank you for your investment in time to draft up the sketch for me. Drawings always make sence rather than just numbers on a page.

Bill S.

I know the line trick, the customer has made a change now the old rail was 1-½ od now were are using 1 inch sch-40 which gives us a 1.315 od even smaller, but I am sure a fine sharpie would work. I would love to see your paper template and wait for your explanation. I thank you in advance for your time and effort.

Johnthomp.

I too always layout with lines, and or string. Works for me every time. I got the idea on the miter box, you and several other people suggested this method and today will give it a try, I have never done it this way but with all the explanations it makes the most logical sense to me I will let you know of my progress. I totally agree with you with the practical verses book smart comment, I have been dealing with that all my working life.

Anthony.

 

[Bill S]

Parallel Line Development

If you have drafting tools this will be simple, if not it will just take a bit longer. Start with a straight horizontal line near the bottom. This will be the baseline. On one side draw your pipe to scale with the exact miter at the top, you can make this whatever height you wish, 4-5" will be fine. Find the center of the pipe and draw a line from the baseline to the top. At this point you will need a pair of dividers, set the dividers to the radius of the pipe and at the baseline point A draw a semicircle. Keep the dividers set at the radius and at points B C and D scribe arcs through the semicircle. This will divide it into 6 segments. Using a square draw lines from the baseline through where the arcs hit the semicircle up to the miter line. Mark the intersection points on the miter from 0 to 6 and then back to 12

Next the stretch out of the pattern. Find the circumference of the pipe and on the baseline mark the start and stop points of the circumference off to the side of the pipe layout. Then divide the circumference by 12 and mark those out on the baseline then draw lines perpendicular up from the baseline from each point at least as high as the top of the miter. Mark the lines from 0 to 12.

Now you can either square lines across from the intersection points on the miter to the corresponding number lines on the stretch out. Or you can measure each one individually and mark the height on each stretch out line. Just make sure you go 1 to 1, 2 to 2 ,etc. Then just connect the dots and you’re good to go. You’ll be able to tell right away if you transposed any numbers. For small diameters keep your layout lines as fine as possible. The whole process is much simpler than it appears at first.

Hope this is what you are looking for. If you have any questions feel free to ask.

Bill

 

[tel]

I think you've complcated the whole thing by introducing the second angle (rise), after look ing at your shoebox projection, isn't all you have to do is make a simple 144° bend and tilt the whole issue upwards?