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Indexing rounds for miter

DesignForgeFab

Plastic
Joined
Jan 4, 2014
Location
Seattle, WA USA
I need to miter round bar. If it's mitered at one end - easy: cut it the miter first then cut square to length. However an upcoming fabrication requires round bar mitered on both ends, AND the ends must be square/plumb to each other.

(Example: make a square frame out of round bar. If the miters are misaligned the square won't lay flat)

Parts will be mitered from 20' lengths of 5/8" SS tube with a cold saw. 1000's of parts to be cut; individual parts ranging from 6" to 2-3'
Production mode will mean that we'll likely rough-cut sets of parts at various lengthsk using a stop (1st miter), then cut final lengths for multiples of each part.

They'll be fused together with TIG welder.

Yes we're doing this layout & cutting the old way: by hand.

What's a good, quick, readily repeatable way to align the miters to each other at precise lengths?
 
I would use a large V block for a stop, large enough that the whole miter rests on one face of the Vee. That should allow one to feel that the round bar is properly seated. If the V block is clamped square to the blade the cuts should be properly oriented.

Dennis
 
I need to miter round bar. If it's mitered at one end - easy: cut it the miter first then cut square to length. However an upcoming fabrication requires round bar mitered on both ends, AND the ends must be square/plumb to each other.

(Example: make a square frame out of round bar. If the miters are misaligned the square won't lay flat)

Parts will be mitered from 20' lengths of 5/8" SS tube with a cold saw. 1000's of parts to be cut; individual parts ranging from 6" to 2-3'
Production mode will mean that we'll likely rough-cut sets of parts at various lengthsk using a stop (1st miter), then cut final lengths for multiples of each part.

They'll be fused together with TIG welder.

Yes we're doing this layout & cutting the old way: by hand.

What's a good, quick, readily repeatable way to align the miters to each other at precise lengths?

You need to fix one axis of rotation. Once you have cut the pieces to rough length clamp them in a small flat vise upside down so the top of the tube is flat with the vise jaws. Then you need to fixture the cold saw in a way that you can cut both ends mitered with the jaws firmly on the saw table and the tube parallel with the fence. Or you could make a wooden fixture that supports the entire length :)
 
1. Level the saw.

2. Make an outboard support with three wheel (ball bearing) support so the tube can rotate easily in it.

3. Make a fixture with a Vee that fits over the tube but completely open on other side. This will sit on top of the tube, just outside of the outboard support. Cut the end at 45 degrees to match the first miter on the tube. Cover this cut with a flat arm 18 to 24 inches long so it can be pushed against the mitered end of the tube and hang below it. This aligns the Vee block and arm on the tube. Add a weight of several pounds on the bottom end of the arm so it will hang vertical.

4. Add a clamp (welding clamp with a spring to close it) to the Vee block to apply clamping force on the bottom of the tube in the Vee. This will hold the fixture in place on the tube. Something like electrical tape on the clamp and the Vee surfaces to keep it from slipping.

So you slap the tube into the fixture with the mitered end against the flat bar and the clamp holding it in place. The tube then sits on the outboard support and the weighted arm will level it via gravity. The spring clamp makes attaching and removing the fixture fast and easy. All you need to do is measure and cut.

Of course some kind of attachment could couple the saw and the jig with an adjustment for different lengths. That would make fast work of making several or many tubes of the same length.

And a test piece or two would be needed to check the initial set-up. If the angle is off the weight at the bottom of the arm could be moved one way or the other to bring the jig to true.

Edit: My apologies, I said tube but you said bar. I am not going to go back and edit the above, just read bar where I said tube.
 
The problem here is where to clamp the tube in the cold saw. If you clamp the long length and set a stop the mitred part will be loose once the cut is finished. The best way is to clamp the part and use a bevelled stop as Modelman said. Your tube is very small so it will take a bit of practice to get the mitre lined up with the stop perfectly. I would also use some flat bar on the back side and front side of the stop so the tube is held in alignment with the saw fence and clamp face. If you just use a bevelled block as a stop the tubing can ride up the bevel and your parts will come out at different lengths. My bevelled stop would have guides so the opening is only a hair more than the 5/8" tube.

So you need to set up and mitre all your long stock on one end and then set up for the mitre cuts to length. You can just roll the bar after each cut and index to the stop. I cut a lot of stock on my cold saws and prefer to clamp the part as it is cut so it is not trapped between the stop and the blade.
This is the fastest way to cut up so many parts to multiple different lengths. Also start with your longest parts so if there is a problem they can be cut down to the next shorter size. Check and double check before cutting hundreds and check again after ten or fifteen parts, check length and miter angle.

Do you have a semi-auto saw or all manual? Also will you be autogenous welding these or using filler rod?
 
Clamp the lengths of round bar inside a square tube with a couple of pinch bolts on the diagonal (so the bar fits in a ''vee''), then you have 4 faces to work from.
 
1/2" 5c collet in one of those square collet blocks at the far end of the tube and index it with a level. The saw doesn't have to be level, you only care about the rotation.
 
It seems the OP has done a runner. Never to return or pay his dues.
I also think some of those responding did not read the part about the thousands of parts required?
The indexing needs to be fast, really fast. Messing around with jigs, collets and levels or tubes with screws is going to turn a tedious job into a nightmare. Even with the fastest method the cutting is going to take days to complete.
The tig welding is going to take many weeks.
 
I certainly did read and remember the part about hundreds of parts. That means that a small investment in time to make a jig will pay for itself when that number of parts is made. And the jig I suggested would not only be fast to use, but also would accommodate different rod sizes with no changes. It may be just me, but it seems that it is the best of all the ideas thrown out here.



It seems the OP has done a runner. Never to return or pay his dues.
I also think some of those responding did not read the part about the thousands of parts required?
The indexing needs to be fast, really fast. Messing around with jigs, collets and levels or tubes with screws is going to turn a tedious job into a nightmare. Even with the fastest method the cutting is going to take days to complete.
The tig welding is going to take many weeks.
 
Tiger stop with a vice or quick-grip on the end. rough cutting is cutting twice, which is more than twice the work. Cut once, shuttle, swing saw, cut, repeat.

You can also tack a 5/8 square on the end. This can be faster if miters are the same (30 - 30, 45 -45) on each end. Cut, shuttle, spin bar (no saw swing), cut, shuttle, spin rinse and repeat.
 
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Op here.

I didn't get any notifications so had no idea of the lively discussion going on here. I thought my post has disappeared into the ethers. Thanks for these ideas!

Agree re clamping the part not the stock when cutting. Miter & spinning round stock is the way to break $150 blades. Voice of experience...

Swinging the saw each cut: nope nope nope. So much nope.

This is a completely manual situation. No air clamp, no power down/up, no magic cnc stop system. It will however miter to 60deg one way and 45 to the other. That's pretty sweet.

We're getting 10% extra material so have to be really judicious about drops. I'm sure somebody here has purchased SS in the last couple weeks, so you know drops mean $$$ especially right now. Thanks Putin. We can't even get stock until a month + out.

The fixturing is a challenge as I'm set up with infeed/outfield rollers, so no reliable surface to align a clamped square fixture to the saw for a whole 20' length of material.

Some version of the vee stop is probably the way to go - no marking to do... even sharpie was going to be an issue for the finish.

Open to additional brainstorms if you have 'em.

Cheers!
 
Your material is small and I would be inclined with your setup to make a sub surface jig that you can attach to the infeed and outfeed rollers. This would allow you to clamp the stop as required and material that small does not need roller tables, it may not even cause the rollers to roll it is so small.

You should have plenty of height for cutting so that is not a problem but you might have to make a temp jaw for the vice to allow clamping over the sub surface. You need to have a clear view of the bevelled stop from above and ideally it would be great to have a light from below so you can see when the bevelled cut meets up perfectly with the bevelled stop.
Also the workpiece will be clamped but the material length will not be clamped so you need to make sure there is no burr on that surface so it registers on the stop perfectly.
With the right setup you should get cuts that meet almost perfectly when clamped for welding. Also the best way to check you mitre setting is to cut four parts and clamp them together. This will show the smallest deviation. All things considered the cuts will not be perfect and you should aim for the mitre to be slightly open on the inside corner, this is the best scenario for welding ( if they don’t come out perfect).

I do a lot of miter cutting and often weld without filler, depends on final strength needed.
 
Something like an outboard stock support, with a traveling piece to engage the already cut miter. Could be as simple as some square tube with a shuttle of larger square. Part tolerances dictate precision required.

Programmed via Mazatrol
 
Make a V-block fixture with a difference. Offset each leg of the "V" so excess tubing can stick past the cut zone. Cut both pieces at the same time and as long as the two legs of the "V" are at 90 degrees to each other the tube ends will fit perfectly, even if the "V" fixture were slightly misaligned so that one tube end was 44.5° and the other 45.5°.

This is a useful trick in woodworking to cut matching miters on a tablesaw or miter saw so I don't see why it wouldn't work here.

EDIT: On thinking about it I realized that I forgot to add that the legs of the "V" fixture need to be offset VERTICALLY so the tubes overlap under the saw blade. The blade will cut through the top tube first and then through the bottom one, making a perfect 90 degree joint.
 
@Scotti - this is a pretty cool solution for matching meters for individual joint fitup, but this doesn't address the need for the meters at both ends of each piece to be square/plumb to each other. Thoughts?
 
No it is not a good solution for your situation, too much time and no indexing.
Which cold saw do you have? With this large of a job I would seriously consider getting a used semi-auto.
I have an 11” which will cut up to 3 x 3 square tube. With a semi-auto you get perfect control of the feed which means better cut quality.
 








 
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