T&F Fabrication Practice Jig

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wwalton

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I wasn't sure if I should just post this in my build thread and then ask questions or start a thread asking first?

Either way here is my first attempt at building the Little Scrapper Tube and Fabric practice jig, henceforth referred to as the jig.
Screenshot_20200529-115520_Gallery.jpg


I really enjoyed laying out the .090. I didn't have the layout dye, it's on order, so I used a sharpie and made the lines thick and marked areas for radius and holes with the sharpie. Used a scribe on the sharpie ink and it worked well.
20200529_102736.jpg
I made some mistakes that I will correct on the next one. I will go through what I see. I give it a C overall I consider it a airworthy part, so far. I'm not through fabbing this fitting.
I'm stuck at the bend.

First my errors, that I see: On the .5" radius I didn't use a caliper, I used a washer, so the radius doesn't match the hole center.
Also my hole center was slightly off. My center punch was pretty close but the starter drill bit, 3/16", drifted some.
20200529_103412.jpg20200529_104551.jpg20200529_105610.jpg
I used a metal cutting band saw with a table attachment in my vise to cut the fitting off the sheet. And a bench grinder to shape the radius.
20200529_105800.jpg20200529_110750.jpg
Now I'm up to date with my progress because I'm hung up on the bend.
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This is the bend layout, just half the length of 4.5". I've laid it out 90 degrees to the grain. And my first thought on bending. Just pinched on my weld table with a C clamp and large piece on top? No heat and big hammer?

So I would like advise and constructive criticism, I realize there are a lot of ways to do things. I will find my comfort zone. But it's been over 30 years since I did some of these things in A&P school so if I'm doing something wrong I want to know.

Particularly I'm looking for a good (best) way to make an accurate bend. I don't have a hyd. press. Do I need one?

Thanks
Walt
 

wwalton

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I'll just add a bit of information that I looked up on this 90 degree bend. Material is 4130 (n) .090" thickness. So bend radius is .281" according to the chart I found. Now if I remember correctly that's a minimum, so if I attempt a 5/16" radius it should be safe.

Now I tried this on a piece of mild steel .125" thickness I used a 1/4" radius and it worked okay. I used a thick piece of steel to push down one side and then put the piece in a vise to complete the 90 degree bend. For the radius I just offset the center mark half of the bend radius over the edge of my welding table. The top corner of the table is rounded some. Then in the vise I used another piece of steel that was previously bent to 90 degrees to support the bend area.

This all seems a little crude to me. It's repeatable but not overly accurate.

I guess if you needed to repeat with accuracy a Hyd. press with bend radius anvil into a 90 degree form would be nice. But is that what people do?
 

Little Scrapper

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Oh man, you’re doing it buddy! Congrats! You officially have skin in the game!

BJC is right, there’s a reality about this but hey, we make the best of it. I have 3 more service calls and I’ll be free to help. Tell ya what, I’ll make that part and shoot a video for it. I’ll tell you how I approach it and you can adjust to fit ok?

I’ll be back between 9:00/10:00 ish central time zone with a short video.
 

Little Scrapper

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Made 3 video. Uploading now. They are raw, unplanned and just kinda loose with only a bit of narration once in a while. I poured a scotch, turned on some tunes and just had a good time. Hopefully this helps. I haven’t replayed them so I don’t know how they will work out. I’m a plumber not a video man. Three video coming up........
 

Little Scrapper

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All three videos were blocked for violating copyright laws. I had background music playing and somehow sophisticated software picked it up and stoped me. That’s crazy.

sorry. 45 minutes of video down the drain.
 

wwalton

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Oh man that sucks. Sorry.
I appreciate the effort. I was actually out in the shop melting .035.
It's crazy what is allowed to get posted and what they restrict.
Guess the music industry has some decent lawyers.
 

Little Scrapper

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Oh man that sucks. Sorry.
I appreciate the effort. I was actually out in the shop melting .035.
It's crazy what is allowed to get posted and what they restrict.
Guess the music industry has some decent lawyers.
my son is gonna help me upload it to the computer and mute it, then I’ll narrate it. We’ll figure something out. Or just reshoot it.
 

wwalton

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Thanks Scrapper I really appreciate the work. I learned a lot today building that fitting and doing some practice welding. Looking forward to cranking out some completed jigs. It's the little tricks that people who do this stuff know that I need to learn. Drilling holes, grinding metal...all of it. I've been working on roll cage size metal and mig welding so it's almost like a whole new world. Kind of exciting and occasionally very aggravating.

I used my left hand for the torch and right hand to feed filler today...that was just like running backwards up a staircase.
 

wwalton

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No problem at all. I'm have plenty to practice welding. I have to work on my van for a few days also so I'm going to have to take a short break for that.

Don't worry about me I'm not going anywhere this is too much fun.

Thanks again Scrapper.
 

Little Scrapper

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Walton. I just looked at your Skybolt log. Your welds are coming along nicely. Exactly what is to be expected.

If I may, the issue I see is a simple one of consistency. This is almost always a result of position and practice. All very normal.

Doing awesome bud! You’re gonna make a great welder by mid June if you keep this up. Easily mid June.
 

wwalton

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Thanks Scrapper, I have taken a few days off basically, had to do some honey do's. I did work on the jig a little but not much. Tomorrow I'm getting back at it. Argon is down to 400 psi so probably have to do that but I'll get my initial jig done first hopefully.

I appreciate the feed back on the welds...yeah it's just a helmet fire going on once the puddle from the solid tube melts and the coped tube starts to go...I just have to get ahead of the action.

I'm still loving it. I do occasionally wonder if I'm improving..lol

Thanks again.
 

wwalton

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Thanks, Well it wasn't pretty. I started with the fitting C clamped to my welding table with a 5/16" bar on top. The top of my tabel is rounded a bit probably from being sheared. I figured it was close enough to the safe bend radius. I used another thick bar to start the bend but that 4130 is some amazingly strong steel totally different than the mild so I ended up using a large ball peen and the bar to hammer the bend to about 90 degrees. Once I was close I took it out and used the hammer to straighten out the bow caused by the initial bar use. It's pretty good but I missed my setback distance so the center of the radius is too far out.
I'll improve the process.
 
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