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Indexing rounds for accurate miters

DesignForgeFab

Plastic
Joined
Jan 4, 2014
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Seattle, WA USA
1000@ of parts to make from 5/8' SS tube, to be mitered in a cold saw. Parts need to be mitered at both ends at repeatable, accurate lengths for fabrication. (ANALOGY: making a flat, square frame from round bar.)

I need to index the bar (20' raw lengths will be cut down to final parts @ an appx range of 4" - 24" with multiples of each interim length) so that the resulting miters at opposite ends of each part will be plumb/square relative to each other. I'd like to cut rough lengths then set a stop to cut final lengths with a visual reference for rotational position.

Marking & cutting to be done by hand. Ideally, minimal finishing to be performed on the completed assemblies (i.e. no scribing)

What's an efficient way to accomplish this?

(I tried to post this earlier and don't see it anywhere. Apologies for duplicates)
 
1000@ of parts to make from 5/8' SS tube, to be mitered in a cold saw. Parts need to be mitered at both ends at repeatable, accurate lengths for fabrication. (ANALOGY: making a flat, square frame from round bar.)

I need to index the bar (20' raw lengths will be cut down to final parts @ an appx range of 4" - 24" with multiples of each interim length) so that the resulting miters at opposite ends of each part will be plumb/square relative to each other. I'd like to cut rough lengths then set a stop to cut final lengths with a visual reference for rotational position.

Marking & cutting to be done by hand. Ideally, minimal finishing to be performed on the completed assemblies (i.e. no scribing)

What's an efficient way to accomplish this?

(I tried to post this earlier and don't see it anywhere. Apologies for duplicates)
Could you make a round dial with marks on it install it in the end with a expanding mandrel with a pointer that can pivot from the center it will always point down so you can tell where your at. Work towards the end with the pointer in it. Hopefully you can figure out what I’m saying. Muffler shops use this to bend exhaust pipe.
Don
 
Make a vee block with SHCS to clamp the round. Saw the parts 1/8" oversize before clamping. Clamp the vee block and make a cut. Swing the saw table to the other miter. If possible set up a length stop. Push the miter to the stop block and make the second miter.
 
I would:

Set the saw to 45 degrees.
Cut one end of your stock at 45 degrees.
Place the saw on a three foot board (you said 4" to 24" lengths)(a 12" wide shelf board would be good).
Use some feature of the saw to align it to a single position on the board so you can repeat the set-up at a later date. Fasten it firmly in place.
Make a stop with another piece of that board about 6-8 inches long.
Install two lag bolts in the stop board with a gap about 1/2 the tube's diameter between them.
The top of the stop board should align vertically with the top of the saw's table.
A 45 degree cut will wedge into that gap at a fixed distance and tube orientation.
Clamp the stop board on the 3' board at about the distance for the first size part you need. Allow a little extra for adjustments.
Wedge the 45 degree end of your first piece in the gap and cut the second end, also at 45 degrees, but opposite to the first end.
The two lag bolts will align the tube at the correct angle so that the two 45 degree angles will be aligned as you need.
Check the length of that first part and adjust the position of the stop board as needed. Re-cut that first part to size and check again. It should be very close.
Mark the position of the stop board for that part on the three foot board so you can return to it later.
Make as many identical parts as you need. You should be able to work your way down a piece of stock with no waste after that first cut.

Repeat for the other lengths you need.
 
How accurate do you need to be?

If it's for welding...................................

Cut to rough length, miter one end, use a Flange Wizard to put a mark at the midway point of the rough length while it's clamped in the saw for the first miter.

Miter all pieces.

Put a stop on the infeed, flip the cut pieces around, and use the mark you made with the Flange Wizard to find top dead center, and cut your second miter.

This assumes that the cold saw is leveled.

Besides..........a good welder will deal with any gaps, as long as the lengths are good. It's the final setup jig that really sets it up for welding.
 
You don't have to pound the Flange Wizard with a sledge hammer LOL, just enough of a tappy tap to make a mark you can find later. Or use some ink I guess. Ink the tubing, and slide the pointy end of the Wizard longitudinally to make a mark in the ink.
 
I would clamp the tube in a fixture that indexes off the saw frame. Though I wouldn't actually I wouldn't do that -- I would do everything in my power to source the part to someone with a tube laser and not have to 3x cuts and 1x fixture loads on thousands of parts. My time, and yours, is worth more than that.
 
I would clamp the tube in a fixture that indexes off the saw frame. Though I wouldn't actually I wouldn't do that -- I would do everything in my power to source the part to someone with a tube laser and not have to 3x cuts and 1x fixture loads on thousands of parts. My time, and yours, is worth more than that.
Hell, that's an elegant solution. I was operating on the premise of "visible mark". Take care to make a fixture that's accurate, and it's a slam dunk.

About time................................if it contributes to covering overhead, and your guys aren't fully engaged at the time.............it's time well spent. Or, they can stand around with their thumbs up their backsides, doing nothing. I guess it just depends on how busy you are, or aren't.
 
You did post this last year at some point and I replied with how I would do this task.
I searched but could not find the other thread.

A very important part of this procedure will be getting the correct blade for the material. Cold saws need different pitch blades for different wall thickness and material size.

Make an end stop that is mitred so that after the first cut the mitred stop will index the part. You will need a decent infeed and outfeed table to support the tube.
Set the saw at 45° and cut the end of the tube. Then rotate the tube and slide it along until it hits the stop.
If the stop is out past the machines fence then it will need its own “fence“ reference surface so the indexing is controlled. Otherwise the thin tube may want to bend a little and slide past

With some practice you will get good at indexing the tube so it is tight against the stop. Clamp and make the second cut. The problem is the finished part will not be clamped given that most cold saws cannot use two vices when mitring at 45°. This is not such a big deal with the longer parts but the 4” is pretty short so it depends on the cold saw you have and the amount of time you want to spend setting this all up. I would put a front fence in place so the cut part will just sit there as the saw retracts.

I have two semi auto cold saws and use them both daily. I was just cutting some 3 x 3 x .125 hss tubing on 65° angle. The saw will mitre to 60° so I had to shim to get the extra 5° but it worked for the eight cuts needed.
Just enough blade on my 16” machine to make that 8.375” long cut.

Of course the fastest way would be to have someone else cut them but that is not what you asked.


Good luck with your parts,
Michael
 
We just re-designed a double mitered tube weldment. It was difficult to get the miter on each end to be inline with each other on the bandsaw. The weldor dealt with it, but it wasn't an ideal situation. We have gone to having the parts tube lasered. I'll have my first batch of these parts in a week or two and I'm anxious to see the improvement. Since the parts are going through the laser, I've got it etching in alignment arrow and some notches. Saves a fixture and a trip through the mill.
 

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For much smaller quantities I have used my Miracle Point clinometer, which reads to 1 degree, I have also clamped a vee block to the end, and used a level on the side to confirm a 180 degree index.
 
seems like a square collet block, with a slightly larger than 5/8" bore, and a set screw, with a piece of tubing in it, will work.
It would be a reference cut- say, a 45' cut on one end. But the block would need to be drilled offset so the tubing could be resting on the outfeed table of the cold saw, not up in the air. And the block would need some kind of flange that you could clamp to the fence.
That is, assuming you have a fence and an outfeed table.
Then, lets say you need 20 pieces with 45 degrees at both ends 12" long.
You clamp the collet bloce the appropriate distance from the blade, make an initial cut on the end of the 20 footer at 45', then slide the 20 footer over till your recently cut 45' aligns with the reference cut in the block.
basically, its a mitered stop.
The human eye and hand can pretty easily roll the tube so it is flush with your reference cut, meaning the new cut would be at the proper orientation.
you could also just use miter blocks, on an adjustable stop.
my cold saw has a fence and outfeed table ten feet to the left of the saw blade, and a biesemeyer style stop with a steel tape measure on the fence for reference, so once i know the actual distance to blade, its easy for me to just slide and clamp the stop. The stop can have the miter end on it. In the photo it has a right angle end, but a mitered block could screw on as well.
Clear as mud, I know, but its actually pretty simple, and it works.
 

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I could see attaching a collet block to the off end of a 20'er, setting the saw for 45 deg, making a cut, rotating the collet block and the stock 180 deg, shoving the cut end against a stop and making another cut. The surface the collet block slides on would need to be flat, with good geometry to the saw.

Might have to shim the lower surface of the cutting area up to compensate for the collet block thickness, also shim the fence out an identical amount, and maybe also at the stop, but the vise could work as usual. No need to clamp the collet block, it's just a reference.

An abrasive saw would be a lot faster if it were permissible. Curious about the tolerance, too.
 
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