How to drill a larger hole in a gas welding tip?
Any ideas on how to enlarge a #74 orifice in a Smith welding tip to a #71? I have a set of small number drills but actually don't have a pin vise or anything to hold them in. Also, how would I drill the hole square? The tip is a non orthogonal shape so can't easily be held or aligned. I might be able to centre my mill over the orfice with a co-ax aligner BUT how do I guarantee that the hole is square to the drill? (assuming I could hold the drill!!)
I don't think you can. The hole is the whole length of the tip and makes a bend. You might try to make your own tip, but drilling that small in copper for that distance will be very tedious. Not to mention a few broken drills.
As far as aligning the hole, you could insert a snug fitting pin and indicate off of two different points on the pin to align the axis of the hole to the spindle axis of the mill. If there is a bend in the hole this probably won't do you any good.
What you are trying will most likely result in a unusable tip. The flame will probably have a poor shape. I have done this several times in an emergency where tips were weeks away. I got the job done, but it was not easy welding.
The tip has an "orifice" (about 1/2 long IIRC) and it is swedged into the main tip. The body has a nice gig hole so you only have to enlarge the Office tube (again about 1/2 inch). The factory has the entry/exit rounded to make the flow smooth. Yours will be a sharp transition. I've never been able to get a nice shaped flame after modification. It is much like welding with a dirty tip.
Jets (offices) on carburetors have the same problems many times. If you must modify and the result is no good, I would suggest removing the orifice (which will ruin the tip forever) and looking carefully at what the factory has done (just for future reference). Let us know how you come out.
When I enlarged the Offices, I did it one drill size at a time, held the drill in vice grips and backed out many many times. Remember- my instructions are no good because my modification was unsatisfactory for future use. On Smith life time tips the copper WILL unscrew from the adapter so you can see the size of the hole to the tip(I just unscrewed one a few minutes ago to verify that memory is correct about disassembly).
I'd try forcing tip cleaner files to enlarge the hole first. Maybe burnishing the hole to make it smooth would help- I have wondered if the spiral left by drilling made the gases swirl and resulted in the poor flame.
I had jobs to get done by any possible means in the time available so i just worked with what i had. If at all possible, A man would be better advised to get the right size tip (though I am not sure Smith makes such a large tip for my torch).
Best wishes for success on a thankless task.
(edit comment- the hole through the orifice has no bends. Remove the adapter, push a piece of FLEXIBLE wire through the the tip until the orifice stops the wire. Pull it out and you have a pretty good idea of the length of the orifice. It is not very long but it is many times the drill diameter, so a broken drill is apt to happen. A pin vice or other hand held tool may be be the more sensitive way to detect binding )
[This message has been edited by docsteve66 (edited 02-29-2004).]