Losing my accuracy - bit by bit ....

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Feb 7, 2008
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Hi all
How can I do this better ?



I am trying to weld a M12 bolt into some round or in this case square tube for a SA drum brake axle ....
So they need to be square to the axle , although not necessarly to it's centre line as long as they are the same each end.

It is not going well ?

First loss of accuracy ?
M12 hole cutter in the 3mm plates makes a bigger hole than M12 ! :mad:

Easy to weld bolt head to inside plate as I made up a crush tube and tightened it up with washers and welded each facet , although first problem ensure they are NOT in the same place for both inner plates grrr:mad:

Second loss of accuracy
How to weld second plate on ?
I tried clamping to bench with wood same width as gap and tacked it on the outside , then had to bash it square and tacked 180' away from first tack.
The had to weld all the way around the inside as outer tack's had to be ground out for washers to fit , plates loose parallelness [ if they had any ] :mad:

plates are not 100' square , then I have to hand file plates for a good fit in tube before welding them in , not very accurate either !:mad:

Any better ideas ? stop my delta being knock kneed ?

please no ' take to a machinist/engineers and have them etc etc etc ' that is NOT the Zombie way we do it with the tools we have at hand:-

Pillar drill
files
angle grinder

thanks for looking Paul
 
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Three points define a plane. So, instead of welding the bolt to two plates, connect it to only plate 1. Then start with soldering(?) 3 pillars to plate 1 and 2. Next step is to center the plates (or do this after soldering a pillar). In the next step the bolt can be welded to the second plate. And afterwards the 3 temporary pillars can be removed (or not, ymmv).
 
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I know it may be too late but if I recall correctly when I did mine.

I made the inner one a snug(ish) fit inside the tube with the puddle weld holes pre-drilled for final welding.
The outer plate was effectively a cap on the tube end and I used a pair of engineers V blocks to align the axles/bolts with everything lined up/packed out and clamped along the edge of my bench.
For a tight fit of the bolt in the outer plate you could try drilling undersize and filing out? 11.9mm and 11.5 drill bits are available. My experience of large drill-bits is that they drill an oversized hole that isn't perfectly circular.
My 12mm bits seem to give me a roughly triangular hole with rounded corners.
 
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You could cut the head off the bolt and weld the bolt to the outside of the box section. Assuming a straight box section you then only have 1 plane to align the bolt which is simple enough using a long straight edge accross both of them at once. You could make a cap that is too long with an oversize hole for the bolt to pass through to give a backplate to the bolt and also weld the bolt to the cap at it's rear. It would be useful to beef up the insiide of the box near the headless end of the bolt with one of your current square bits plug welded in to prevent the box crushing at that point.
 
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Alternatively do it the same way as you've just tried but use a single length of high tensile m12 studding instead of two bolts. That's essentially what I did on my trailer. If you drill the two internal squares at the same time and keep them in the same orientation in the box then even if not perfectly central it will at least keep the studding in the same plane as the box.

Drill a small pilot hole before the 12mm. The central part of large drill bits can't be ground to cut perfectly or the drill bit has no strength. It's not a perfect solution but it does help.
 
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One way might be to use a cut wheel. Make a cut across the top of the tube and then down the sides just past the center line. Then cut along both sides and remove your cutaway piece of tube and set it aside. Use an appropriate piece of flat steel to lay into what could now be regarded as a cradle, line up your axle bolt, weld it securely and then weld the cutaway piece of tubing back on. Cap it off at he end and done.
 
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Thanks all for your answers , much appreciated and more to ponder ?

Kiezel & Hugh I think the less pieces that need cutting the better ;) my ability to cut accurately seems to be the inverse of the accuracy required !

DannyC - your cap end can float about without having those expensive engineers blocks you have and even with them I don't think I have anything straight enough for long enough to use them ?

Popshot - I did wonder about a straight through threaded rod however I believe welding it to any plates would have the ability to bend it ?

DannyC & Popshot I used a M12 holesaw not drills so drilled a M3 pilot hole then used the holesaw , yes if I had drilled it I would have gone M3 , M8 , M10 and M12. A smaller drill may have helped however there is no way I could have accurately filed out a smaller hole to M12.

The 3mm plates will be plug welded at the bolt head end on 4 sides and welded just inside the tube at the outer end then I can look at filing the unwanted weld off the outside.

I had though of cutting say 2" of 1" x 3mm angle and welding the bolt inside the valley , then I could plug weld the angle inside the square tubing and end with a 3mm cap on the outside ?

Paul
 
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Using 8.8 high tensile should help reduce any welding bends. At least it would start off aligned.
Now that begs a serious question ?

Can you actually buy 8.8 high tensile rod ? I have never been able to establish that ?

Paul
 
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