Solving/finding miter joints

Ashcat

Active Member
Location
Wisco
Figured this was the best place to post this subject

I didn’t pay much attention in high school because had they mentioned this stuff would be useful with race cars I’d been straight A’s.

This latest project stumped the hell out of me. I’m building err uhh a hand rail, yeah, a hand rail! That’s it. A standard double corner miter joint in a single plane isn’t rocket science. However when you throw a rotation into a second plane, add a second joint and a third plane, it smokes your mind.

The internet only retrieves results of inconclusive is it strong enough debates, when did this become cool and keyboard fabricators calling six figure trophy trucks hack jobs.

Any technical content was for roll out templates and some Greek terminology for building hand rails. <——— I have a feeling somewhere in the pipe fitters book or boring as mud hand rail equations is my answer but I need laymans terms.
 

Ashcat

Active Member
Location
Wisco
PVC was used because I knew the rotation screws with the miter angle. Wasn’t about to practice or waste steel. Basically I started with the base angle in a single plan and started guessing from there 5* either direction and painfully narrowing it down to the 1/2 degree.

The first joint (short stubby top of model) was a parallel offset with a 48* in a level or 180* plane, the second leg of the offset (long leg) runs a 23* downward angle to the 90* vertical leg that jogs offset 14*.

The upper joint turned out to be 25.5* and the lower at 35* something. The rotations weren’t even guess work. They were total witch craft and mostly solved with precision optometry.

After a week and a couple solid days of cursing and slicing dozens of pvc parts I completed the job in steel with zero waste. Oh and I had to duplicate the assembly on the other side of the uhh ummm stair case, yeah stair case!

All 3 pieces were sliced and slid over the steel to trace the cut pattern and each cut was made by hand with a cutoff wheel.

Each joint is fitted with a bulkhead plate for ultimate safety for all who utilize the uhh staircase. 1404891C-0BDB-46D4-9146-9CB76BB50E56.jpeg6DACF524-42F1-403A-9209-012D3B75D2EA.jpeg49A1A120-5C74-4B05-BC13-229F5872B902.jpegB85FD0BD-0886-4BAE-888B-2AA0DCC1FB6F.jpeg82A9A4CE-D37A-4603-8FF4-B4B86A0EED63.jpeg
 

YROC FAB.

BUGGY TIME
Location
Richfield, UT.
laymans terms.
Cut to fit is my preferred method. I could care less about a few inches of waist here or there. Time is money. If its too complicated that i cant simply do it in my head then i just cut over sized and mark where it needs trimmed. Now this is only true with what i consider cheap if i mess it up, which any piece of roll cage material is not worth my time trying to be clever by cutting it one time. I have found my self anymore not even using a bevel guage to get my angles of my notches dialed in anymore. You said "precision optometry", ive always said Calibrated eyeball, i believe its a developed skill, im petty good at guessing length >48". This is what i find my self doing with notch angles is just eyeballing them. I used to bevel gauging them then notch them 1/4" ish long and then re notching them for a perfect fit, but anymore i will will just eyeball the angle, notch it long and then make the needed adjustment for that perfect fit, now this is really only on complicated angles and fit ups like you have with your mitters. What i have found to be my biggest reason for gettting lazy with my metrology is the progression of my tooling, I can renotch a tube in about 15 seconds with my notch master. Your mitter for example i would cut close on the chop saw hold the tubes up where i want them to meet and blow off a 1/4" in no time on the belt sander with 36 grit ceramic belt. I wish i had a good laymans term for it but i think you will have to open up your Unions pipe fitter hand book, maybe try this "Bend Tech" ive heard about?:rofl:
 

Ashcat

Active Member
Location
Wisco
I thought about asking the people I know with cad or bend tech dragons but wasn't going to give up that easy. So that’s why I got close and snuck up on the angles because technology or the mathematics weren’t available to me. I just had to fumble through it until I got it right. I would still like to understand the math involved without taking a college course because, yes, time is money, even though I’m the client :p That’s why I calibrate my dies, have cost of material gauges and my machinist paper with basic geometry tools. I can bend tube with quick math and chicken scratch on scrap paper or even do it in my head. Typical notch junctions are figured on paper in moments with 2 controls (rise and run) solve for the angle, give myself roughly 1” waste and notch away. Notcher is for performing the heavy labor, fitment is achieved with a flap disc. It’s not intimidating anymore and I don’t stress and labor over setup for most operations. I’ve learned a lot a little tricks through experience and observation and for the topic at hand it’s not about tooling, tricks or production, it’s about learning how the problem is formally solved in general.
 
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