Oxy-Acetylene root penetration

I'm taking welding classes and we are doing Oxy-A at the moment, but am
having great problems getting nice root penetration on simple butt welds at
the same time as adequate reinforcement of the weld face.
With a No3 nozzle (3 cu foot acetylene per hour), neutral flame, I'm using
2mm plate, spacing to about 2.5mm and using a leftwards technique. If I let
the 'onion' form then move off filling the puddle before I know it I've
blown a hole. If I feed fast enough to avoid blowing holes I end up with
insufficient root penetration and/or inadequate re-inforcement.
Any tips or advice would be appreciated whilst I go off and get my cylinders
refilled and try and find some more 2mm offcuts :(
Andrew Mawson
Bromley, Kent, UK
Reply to
Andrew Mawson
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I think a no 3 nozzle is much too big for 2mm plate.
Even on 1/4" plate I use a no 2 nozzle. With 2mm I would probably go down to a 0 or 1.
2.5mm spacing seems like alot as well.
Reply to
Many thanks for your comments - I apprecate your quick reply (but !) Different manufacturers use different ways of labelling their nozzles.
I think your nozzles may be using a different numbering scheme from mine which is why I quoted cfm used per hour - in the BOC range the number is the cu foot of acetylene used per hour, so a number '0' wouldn't do much at all but my number three uses 3 cf/h. As an example in the Butro 'model O' nozzles a number 3 only uses 1.1 cf /h - there is a useful table on their web site at:
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(The table at the top of that page corresponds to the BOC nozzles I'm using)
Reply to
Andrew Mawson
Try making the gap the same thickness as the plate, or even a tiny bit less.
Make sure you have a "keyhole" happening. no keyhole = no penetration
Point the flame where you _want_ the filler metal to go (just ahead of the edge of the keyhole)
Sounds like to much heat, as another pointed out, try the next size torch down. You could also try inclining the torch slightly more to change the rate of heat input.
Last, if you are trying out different things, try to only change one variable at a time.
Reply to
Wayne Bengtsson
Try a smaller nozzle or close your gap it is to wide. Try it butt together first.
Reply to

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