What am I doing wrong?
- Thread starter ban-all-sheds
- Start date
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I wouldn't be surprised if the welded seam showed a slightly different colour, and may be slightly harder or softer than the parent material. That certainly won't help achieve a good finish.
The weld filler may be soft, but the edge of the weld could be relatively hard from chilling where it meets the parent metal. Just beyond that edge, the parent metal could have been annealed by the welding process, the annealed zone then giving way to a work hardened area where the tube has been formed, then back to an annealed area on t'other side of the weld.
Heating conduit during the galvanising process could relieve some of these localised variations, which may be more apparent in black japanned conduit.
Some of the stuff isn't even round, at least not in the way that a piece of ground steel shafting is round. there's often a small lump or flat where the seam is.
The weld filler may be soft, but the edge of the weld could be relatively hard from chilling where it meets the parent metal. Just beyond that edge, the parent metal could have been annealed by the welding process, the annealed zone then giving way to a work hardened area where the tube has been formed, then back to an annealed area on t'other side of the weld.
Heating conduit during the galvanising process could relieve some of these localised variations, which may be more apparent in black japanned conduit.
Some of the stuff isn't even round, at least not in the way that a piece of ground steel shafting is round. there's often a small lump or flat where the seam is.
The only thing I did differently this time was to clean the end of the conduit of all traces of rust & black enamel.
Through the whole process the tool turned much more easily than the first time.
I backed it off about every one turn by about ¼-½ a turn.
Still not perfect - there are some surface imperfections (OOI I'll try taking a wire wheel to it), but the thread is sound, and I'm happy to use it.
So I don't know why it went wrong the first time - maybe it was just that the cutter needed to bed in a bit, maybe the end of the conduit was slightly out of shape, or maybe I didn't have the tool on square, although I was sure I had.
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You're getting there!
The guide usually keeps things more or less square, cheap conduit or dies might not help. Backing it off and giving it a jiggle seems to work OK for me, a smidging of trefolex makes a big difference too.
The guide usually keeps things more or less square, cheap conduit or dies might not help. Backing it off and giving it a jiggle seems to work OK for me, a smidging of trefolex makes a big difference too.
So who knows what went wrong with #1? Ah well - whatever it was it's gone now...
The only other thought I had was could I have used too much Trefolex, and the whole thing got gummed up with swarf that wouldn't clear?
H
holmslaw
..
6.
It does, and there's a constant resistance too. On the first go it got so tight to turn that I could see the conduit twisting (and I don't mean turning in the vice jaws).
Now the only roughness I encounter is when backing it off - usually after about a ¼ turn I can feel something snagging, but quickly rotating a little bit forwards and back clears it.
Yup. Thinking about using a bottle brush to sweep it out too.....
Anyway - now that I've sorted the cutting of the threads, the one remaining Q (I hope... 
) is how long they should be.
In the diagram below, which is a section though a length of conduit fixed to a box via coupler and bush, and the threaded part is grey, does it matter if the thread extends beyond the coupler, as in the top one, or should it be short enough so that the coupler goes to the end of it, as in the bottom drawing?
Sorry about all this but I'm b****red if I can find any guides online...
) is how long they should be.In the diagram below, which is a section though a length of conduit fixed to a box via coupler and bush, and the threaded part is grey, does it matter if the thread extends beyond the coupler, as in the top one, or should it be short enough so that the coupler goes to the end of it, as in the bottom drawing?
Sorry about all this but I'm b****red if I can find any guides online...
It wants to be like the bottom picture.
Normally for a coupling, you thread the conduit so that about three threads are sticking out the end of the die.
Normally for a coupling, you thread the conduit so that about three threads are sticking out the end of the die.
Ta.
yup, same length as the pre-threaded end when you get the conduit..
you could do it as 1 if you need room to get the coupler in ( tight to a ceiling or going over a lip or something ).
screw the coupler fully on, put it in place, then screw the coupler off until it meets the box..
a lock ring chould be used to lock the coupler in place..
it's like a running coupler.. ( you know how to do those right? )
you could do it as 1 if you need room to get the coupler in ( tight to a ceiling or going over a lip or something ).
screw the coupler fully on, put it in place, then screw the coupler off until it meets the box..
a lock ring chould be used to lock the coupler in place..
it's like a running coupler.. ( you know how to do those right? )
Yup, not that I'll ever need to.....
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