By -
Date 08-24-2001 17:42
I think that this sounds like a good aplication for "cad welding". At any rate, that is what it is called in South Africa. (I think it may be a trade name.) May also be called "Thermite" welding or exothermic welding.
It is often used to join conductors.
Bottom line, they mix a lot of the metal oxide powder with aluminium powder and place it in the hole. Next it is ignited and within a fraction of a second you have welded up your hole due to the extreme exothermic reaction.
Can't really give you suppliers, but if you search for "cad welding" on any of the major search engines, you will get some links.
Hope this helps
Regards
Niekie
hi ,there are 8 to 10 holes in machineable steel ,,not quit sure of the grade,mild steel thou ,,I now that .they are .75 diam.roughly 1.5 to 2 inches deep.I havent seen the piece , may be in the horz. position.Do you have the capabilities of doing such work.Thank You,,,paul
I assume that using heli-coils are out of the question.
I've been trying to find some of my trade magazines that advertised a bore welding apparatus. I'm wondering if those will weld a hole as small as you have. Maybe a search on the 'net under "bore welders" will get the info for you.
In the mean time, are the holes close together? Are they through-holes and can you get at boths sides? I'm thinking that you might countersink from both sides, leaving 1/2 inch of the bore at .75 dia. That way you would have access for manual welding methods. Grind a piece of ceramic backing to about 13/16" to plug the center, weld up 1 side, chip the ceramic and slag, and weld out the 2nd side.
If you can only weld form 1 side the countersinking could still work but you will have a huge weld.
If the holes are close together you could have some significant distortion and warpage. Even without being close together you will get some distortion but not as bad.
Hope it helps,
CHGuilford
hi again,,thanks first of all for all your input.I have since learned that there are at least 22 holes and they are blind holes, not thru holes.And on top of that, they are in a flange of a machine,and closely spaced.This in itself creates a problem of distortaion.And ive been doing searches on the web for bore welding equipment,to no avail.It seems now that there is onlyone option is to machine the flange with the holes in it OFF,of the machine and reweld a new tapped block on in its place.This will most likley req. field machining equipment ,,to get a good level base to mount the new block ,,,yada,yada,yada,,,,thanks again ill let ya know how it goes,,or if it DOSENT,,,,paul
If you're not looking to spend a lot of money on a Borotech machine, get a magnetic based drill and a bit to bevel the holes back to 20 degress or so. Then use SMAW, FCAW or GMAW to weld them out. Start the arc in the bottom of the hole and weld in a circle around the bevel and work toward the center of the hole. When you get to the center and fill the crater, stop and clean the slag out, then start the next layer. We used to do this with SMAW on submarine bolt holes when they were put in drydock. One of the jobs I hated most too, because they were all on the bottom of the hull and you had to weld them overhead. It did help keep the slag from building up too bad, but it had a way of finding a way into your shoes.
Marty
I sure don't envy you on that job Marty. GMAW is an excellent choice for plugging holes if they are in the flat position. They can be welded out nonstop with that process (similar to electro-gas). 3/4" is a bit tight for 2" depth, I would open them to at least 1". In any case drill out threads as threaded holes are nearly impossible to clean out sufficiently and tapping oils will always cause problems. Use 98/2 or 95/5 argon/oxygen, set wire speed high relative to voltage to get to the bottom of the hole, however, maintain spray mode to ensure fusion.
Through holes can be welded using a copper sump slightly larger in diameter and about 1/8" deep. Care must be taken to start the arc on the steel not the copper!
It's always best to run and section test pieces first. When they can be made without voids or LOF, should be ok to run on non-code mild steel applications.
Unfortunately, this method puts a lot of heat in a small area and distortion may make it unsuitable for Paul's application. And I think it's here, as well as for deeper or out of position holes, where the Bortech machine has a definite advantage.
Dave
