DC welder heating...why no luck?

GregSY · Oct 11, 2021

So...as I continue to try to resurrect the Voest drill press that no one loves but me, I have discovered the vertical acme thread-screw that is used to raise and lower the head is stuck.

This is odd, as the drill appears to be well lubricated...no rust. But the screw is stuck dead solid....I can put a 24" pipe wrench in it and it won't budge even a bit. I've run some Kroil down the screw for about a day, still no luck.

I decided to try putting some heat in the screw. I connected my Miller 180SD TIG welder in the arc welder mode. Positive polarity on the electrode side, and the ground is negative I must assume.

I turned it on and dialed up the amps all the way to 180.....the top lead (electrode) stays at 84F room temperature. The bottom lead (ground clamp) does get up to about 130F. The screw itself also shows no temp rise at all.

I suspect the answer is I don't have enough welder. But not sure. Also, why is the positive side showing zero temp rise while the ground is at least picking up 45F?

mjk · Oct 11, 2021

have you tried applying pressure with a jack to lift the head/relieve the pressure on the threads

is it possible the threads are split inside the case

eKretz · Oct 11, 2021

Does the welding machine show actual current or just setpoint? If only setpoint, got an amp clamp? Stick it on a lead and see if you've got the 180 amps. Maybe you have a bad connection and no current flowing. Or maybe there's one of those arc control functions that limits the "dig" characteristic active.

Garwood · Oct 11, 2021

I bought a 180SD brand new. I felt it was very overrated to claim 180 amps.

If no heat rise I would guess the 180SD might be too "smart" to short like that.

If you find a reasonable Syncrowave, buy it.

metalmagpie · Oct 11, 2021

I have restored a machine where the table lift screw got abused and collected swarf to the point where it would not move. I was able to remove the screw and its "nut" and soak them and pick out chips and keep working it until I got it to move, then I got the screw out. I had to file the OD of that screw quite a bit to get it to move smoothly again.

The thing you want to heat is the "nut", not the screw. Heating the screw expands the screw and will make it tighter. Heat the "nut" with a torch. Or, if you can get the screw assembly removed from the machine, you can put the whole thing in your BBQ grill and heat it all up. With a lot of preheat you should be able to get it to wiggle unless something is plain broken.

I would use an oxypropane rosebud turned way up, and keep moving the flame around the "nut".
Some guys say they have had luck spraying something very cold on the screw just before trying to move it. The idea is to shrink the screw and expand the nut, allowing more clearance.

Take your time. Work on it until you get really frustrated, then walk away from it until you get another idea to try.

metalmagpie

GregSY · Oct 11, 2021

If you look at the photo, you can just see a black shape under the head...that is a floor jack which I have 'lifting' the head a little.

Good idea on the DC ammeter....but I don't have one that will measure that kind of current. I have AC clamp-on ammeters that go to 600a but no DC.

What weird is the location of the nut in the head is not apparent from the outside. The screw passes through a good 12"+ of head and who knows where the nuts is.....I'm guessing it on the bottom but because the head is lowered all the way I can't see or access it, if it is.

My guess is just that...someone ran it down hard on a bunch of swarf and jammed it. But it feels 'damn solid'. Imagine if you welded it to the head...that's how unwilling it seem to turn. If it is jammed, the only answer might be 'lots of torque' to turn it back.

kenton · Oct 11, 2021

Is the TIG pedal disconnected? I had a similar issue trying to stick weld with my Miller 180sd and found it was not sending current until the pedal was depressed or removed all together.

link to thread: Miller Syncrowave 180 SD stick welding does not work

GregSY · Oct 11, 2021

No, I can try that though.

I do suspect the welder is limiting itself...though when I had it apart 10 years ago to install the CoolMate I clearly recall it still uses an old style transformer, not wizardry.

GregSY · Oct 11, 2021

lol....I tried disconnecting the TIG pedal and after about 45 seconds the welder shut off. The 30 amp breaker in the wall had popped. So at least something was happening. I'll try it again later when I have more time....I'll have to creep up on the amps to keep the breaker happy.

Scottl · Oct 11, 2021

Garwood said:
I bought a 180SD brand new. I felt it was very overrated to claim 180 amps.

If no heat rise I would guess the 180SD might be too "smart" to short like that.

If you find a reasonable Syncrowave, buy it.

My guess also. Many electronic control welders limit short-circuit current so no arc, no full current.

mjk · Oct 11, 2021

Any chance of access to the "nut" if you pull the ram/motor/head out?

eKretz · Oct 11, 2021

metalmagpie said:
I have restored a machine where the table lift screw got abused and collected swarf to the point where it would not move. I was able to remove the screw and its "nut" and soak them and pick out chips and keep working it until I got it to move, then I got the screw out. I had to file the OD of that screw quite a bit to get it to move smoothly again.

The thing you want to heat is the "nut", not the screw. Heating the screw expands the screw and will make it tighter. Heat the "nut" with a torch. Or, if you can get the screw assembly removed from the machine, you can put the whole thing in your BBQ grill and heat it all up. With a lot of preheat you should be able to get it to wiggle unless something is plain broken.

I would use an oxypropane rosebud turned way up, and keep moving the flame around the "nut".
Some guys say they have had luck spraying something very cold on the screw just before trying to move it. The idea is to shrink the screw and expand the nut, allowing more clearance.

Take your time. Work on it until you get really frustrated, then walk away from it until you get another idea to try.

metalmagpie

Heating the inside component can work just fine also. It's all about breaking the bond between the two. That can happen by heating either-or. It's obviously best when doing this to heat and allow to cool before attempting any movement... And if the nut were reachable I'd try heating that too. One at a time, fully cooling in between.

GregSY · Oct 11, 2021

Yes, heating the nut would be best but it's inaccessible (without dismantling the head). If I heat the screw, it'll transfer some heat to the nut and also break the bond.

This drill press is apparently wicked-rare, at least in the USA. Even the Oerlikon press...there is information floating around. But the Voest, I have found nothing. I'm generally not afraid to disassemble it without a manual or exploded diagram but I am also aware parts availability cwill be 'zero' and that could be a risk.

I'll be honest....my investment in this drill press is mostly one of pure interest. If it requires too much suffering on my part....it's gonna take one last ride to the scrap yard. I hate to scrap it but it's also not gonna occupy space (especially broken) in my shop forever. I really want to get it working then sell it cheap to someone who can use it.

boslab · Oct 11, 2021

Don’t give up on it, I’m sure it’s trying to teach you a valuable lesson.
Mark

GregSY · Oct 11, 2021

Well...I tried the welder with a lower amperage of 50 then 75. The breaker held. The ground lead heated up...the cable would hit 150F and the jaws of the clamp were a bit over 300F.

The top lead stayed within 3 degrees F of ambient. The screw never gained one degree, even. So I gave up on that idea and decided to try the old standby of brute mechanical force.

One of the difficulties in trying to turn the screw with a pipe wrench was that the column clamps need to be loose to let the screw raise/lower the column. But, when the column is loose, the force of the pipe wrench makes the whole column spin instead of the screw, to a degree.

I stuck an 8 foot long 4x4 in the horizontal column and had a mere child hold it. Then, I put the pipe wrench on and a cheater bar and set to tugging. It finally broke free....I think it was jammed on swarf for sure. Once I spun it a couple revs and raised the column 1/4" or so, it hardly takes any force to rotate it. The screw suffered some scars from the pipe wrench but that's life.

Now I think the motor drive will work (it shuddered before against the jammed screw), so that is the next test.

Just a Sparky · Oct 11, 2021

I can tell just from glancing at your picture that the reason most of your heating is occurring in the leads rather than the screw is because the leads have greater resistance than the screw. In spite of iron having poorer conductivity than copper, the screw is many times greater in cross-section than your leads.

You'd probably want right around 1kA at 2~4 volts to get that thing warmed up any time within this century. A spot welding transformer would do it, but not an arc welder. And then you're talking heavy, bare copper braids that can tolerate a lot of heat or else two 700kcmils paralleled.

GregSY · Oct 11, 2021

Well, the screw is still sticky....it freed up but a few turn up it started gaining friction.

This design is not the best....the vertical acme thread has no sort of seal....the hole just runs down into the head casting. That means anything and everything can make its way down the thread....facilitated by the thread itself and gravity and floating on a film of oil.

I'll keep oiling it...hopefully that will do the trick. Right now, the electric motor doesn't have the guts to spin it.

pavt · Oct 11, 2021

IMHO for electric heating nothing beats the old lincoln buzz box on about 75A. Its just old-school AC brute-force.

Glad you got it free, anyway. Keep us posted WTF is up with the screw?

GregSY · Oct 14, 2021

So...I did more inspection and was able to determine the nut for the vertical screw was at the bottom of the head...no surprise. I decided to raise the entire head enough to access the bolts that hold the nut in place...that required that I take the top plate off the upper gearbox. Everything in there looks nice....and for sure, the amount of complexity and cost they incurred just so the column could be raised/lowered with a motor is extensive. Compared to the Oerlikon...it uses a simple rack and pinion and hand crank....this thing is way more involved.

Anyway, the nut is exposed. It's interesting the penetrating oil I had been spraying down the screw did in fact reach the nut. It just didn't help.

When I started this, I knew that dropping the nut out the bottom would allow me to see it, but it also means I can't apply any turning force to it since it's unsecured. I think I will next clean it up, heat it up with a torch, and see if that breaks it loose. If not, I'll reinstall it all and try turning the screw with the pipe wrench until the nut is all the way unthreaded from the shaft. Of course, once it's off....it's not like I have a tap I can chase it with....

eKretz · Oct 14, 2021

If it's that stuck you may be up against a nut so worn that it's trying to skip over the threads on the shaft. Those can get nasty tight. In that case a chase with a tap won't help you any. If you have a lathe you can make a new nut, or alternatively, if the nut isn't that badly worn, your own chasing tap.

DC welder heating...why no luck?

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