Power transformer mounting bolt stuck in varnish???

[dehughes]

Hey all,

SO, in my (seemingly) never-ending PT saga, I received a (huge) PT from Allen Amps (their TP-40D). I thought about taking the end bell off as that would give me room internally to run wires, as well as removing the mounting bolts (stock ones are usually cheesy...I like to install stainless steel hardware...).

I tried to do both...remove the bell cover and remove the mounting bolts...but they are soooo stuck on there due to the varnish (I'm assuming it's varnish...whatever the PT is dipped in....). It's a dark amber color and can be scraped off slowly (did this on the threads of the bolts, as the nuts were kinda hard to screw on), so I figure they can be removed.

SO, I scrape away the buildup at the head of one of the bolts and then use my screwdriver and attempt to unscrew the bolt, thinking what little varnish has made it into the threads will surely be broken away and allow the bolt to be removed.

Nope.

What ends up happening is that, in spite of going slowly and carefully, I COMPLETELY SHEAR the bolt's head off, about 3/4" down the shaft. That's insane...what is this stuff? I mean, I know these bolts aren't super tough, but my goodness! My other PT's were coated a bit with a light waxy glaze, but not nearly this much, and I easily removed the mounting bolts and bell covers (just slipped in and out...no problem).

Am I totally screwed (literally...well, bolted...)? Is there a way to melt the varnish enough to get the bolts out? Maybe a drop of acetone? Should I just figure that the varnish is obviously holding the bolt in well enough, and just mount it anyway? Dah...

I just want this amp FINISHED....but there seems to be a problem lurking around each solution...

Thanks in advance...

[Structo]

Boy I don't know.

Probably a Chinese made bolt.
I have noticed their steel in most cases is rather soft.

You could try the acetone.
Then a narrow drift punch.
I'd be afraid of the lamination's coming apart if you get too aggressive.

[mojo2001]

I'd just rely on the remaining three bolts and get on with it. There won't be much force on that sheared bolt with the other three tightened down. You can glue the head back on with some Goop for cosmetics.

"Steel" is a bit of a reach for some hardware these days, much of which is made out of some kind of metallic looking pressed cheese.

Don't let this bottomless pit interfere with progress toward the goal.

[dehughes]

Thanks dudes. My face is set like a flint to get this thing finished by next Saturday, so if I have to glue on the freaking transformer, I will.

But yes, I'd be worried about separating the laminations as well. However, if the bolts are this cheesy then I don't know if I trust them holding in such a heavy PT.

Any other suggestions before I go buy some acetone and start praying?

[Cygnus X1]

Just wondering...are those bolts supposed to insulated?
Some have a plastic bushing/sleeve that runs along the length.

[dehughes]

Just wondering...are those bolts supposed to insulated?
Some have a plastic bushing/sleeve that runs along the length.

This had a plastic bushing at the top by the head...it's only about 1/2" long. No bushing at the bottom, though... My other PT's had bushings at both ends.

The bottom of these bolts look to be saturated in varnish...no bushing there.

[dehughes]

So...I applied some acetone to the sheared off bolt head, and after sitting for 30 seconds it slipped out of the sleeve. Cool! That's progress. So I then dripped a few drops of acetone into the hole in the hopes of loosening the bolt from that end, as well as applying some acetone to the other end. I let that sit for a bit and scraped away some buildup, then applied a bit more.

Then I took a few flat washers and put a nut on the remaining threaded portion, thinking I could just tighten it down and hopefully extricate the reminder of the bolt now that the varnish has loosened. I tightened it up and then started to firmly tighten some more...and then it seemed to be working! However, I soon found that what was happening was that the bolt HAD SHEARED OFF AT THAT END AS WELL! What a joke...

Turns out that the PT is vacuum impregnated (with the bolts installed) with a varnish and then baked in an oven, therefore making the bolts extreeeeemly hard to remove.

So now I have a PT with three (very firmly!) installed bolts, and one which has about two-thirds still remaining embedded in the mounting hole. Any suggestions now? Drill it out? Leave it? Sell it cheaply and go back to the PTs I was using before? It's such a bummer as this IS a nice PT and hasn't even been wired in....

[mojo2001]

Dude, I tolds ya to leave it alone!

I'd epoxy in the sheared off ends, rig them up as best possible--having the nut side intact will at least work as a spacer, and get on with the amp!

Three bolts should hold the iron. If you drop it hard enough to shear off three bolts, even metal cheese bolts, the cab will probably go first.

Sometimes perfection has to take a back seat to progress!

Have fun

Joe

[dehughes]

Dude, I tolds ya to leave it alone!

I'd epoxy in the sheared off ends, rig them up as best possible--having the nut side intact will at least work as a spacer, and get on with the amp!

Three bolts should hold the iron. If you drop it hard enough to shear off three bolts, even metal cheese bolts, the cab will probably go first.

Sometimes perfection has to take a back seat to progress!

Have fun

Joe

HA! You're talking to Mr. Amp OCD. I leave nothing alone!

But seriously, yeah, I think what I'll do is epoxy in both ends and call it good. I have some crazy strong epoxy that's WAY stronger than these lame bolts, so I'll just do that and be done with it.

[Tubetastic]

Personally I'd drill the old bolt and use one of those Screw/bolt extractors - but that's me.

[Phil_S]

I agree with the guy who says to leave it alone, fix the cosmetics and move on. But I can see you aren't going to do that.

You will need a drill press to drill out that bolt. Cut a hole right in the middle of it, deep enough to insert an extractor. In case you aren't familiar, the extractor is a reverse threaded thing that looks more like a drill bit than a screw. It needs something to grab onto.

However, I suspect you will also break the extractor. This is why I say you need a drill press. With a press, you might be able to push a drill bit all the way through. Then you might be able to enlarge it. Enlarge the inner hole to remove as much of the bolt material as you can. I believe this will accomplish two things. First, it will allow you to run the extractor well into the shaft, reducing the chance of breaking the extractor and/or it will let you use a larger extractor. Second, and this is important, drilling will heat up the remainder of the bolt. The heating and subsequent contraction might just break up the varnish lock on the threads.

Heat is both your friend and your enemy here because it will soften the varnish. You need to head only the bolt because you don't want the rest of the varnish breaking up.

Sorry to get on your case here, but for anyone else who might be contemplating this, it is a classic case of fixing it 'til it's broken.

[Kregg]

"Leave it alone" ... p*ssies.

Worse case scenario would be if the thru bolt has rusted to the plates.
Here's how you remove set bolts.
First will they screw out?
Using two nuts, thread them so that one nut locks the nuts. The top nut should be slightly proud of the end of the bolt. Before the next step see if you can unscrew them from this end (using a ratchet or wrench). Next, tap the end until the bond gives.
Worse case scenario would be if the thru bolt has rusted to the plates.

Remember too the bells could be varnished as well.

[dehughes]

"Leave it alone" ... p*ssies.

Worse case scenario would be if the thru bolt has rusted to the plates.
Here's how you remove set bolts.
First will they screw out?
Using two nuts, thread them so that one nut locks the nuts. The top nut should be slightly proud of the end of the bolt. Before the next step see if you can unscrew them from this end (using a ratchet or wrench). Next, tap the end until the bond gives.
Worse case scenario would be if the thru bolt has rusted to the plates.

Remember too the bells could be varnished as well.

I tried the two nuts thing, and that's what sheared off the end of the bolt. The head sheared off because the bolt is stuck mid-PT in vacuum impregnated, heated varnish. Here's my plan...

No more tinkering. Clean up the end and thread the broken nub through a bolt with a lock washer, and epoxy THAT to the end of the PT where it would have come through anyway. The epoxy will be much stronger than the stupid bolt, so that'll settle that.

Thanks guys! Next time I'll just buy a PT from MM, where I have usually gone for transformers. That's what I get for trying something new, huh.

[mojo2001]

"Leave it alone" ... p*ssies. Cool

Since you are such a player, try a miniature shaped charge. Plastique.

[Kregg]

I tried the two nuts thing, and that's what sheared off the end of the bolt. The head sheared off because the bolt is stuck mid-PT in vacuum impregnated, heated varnish.

You could bore them out. I don't think the varnish froze the bolt. I'd be more inclines to believe that inferior quality metals reacted and rusted to the iron. I say this because I've set bolts into epoxy and they threaded out just fine afterwards.

"...try a miniature shaped charge. Plastique."

HA! Thermite would work just fine. Be careful though ... DHS might come a knockin'.