J-B Weld not setting

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I agree with Michael.

I would (if it was me) prefer to try that option rather than have welding splatter to deal with. If it should fail it could always be milled out with a slot and that then welded.

Nick

Michael,

You know, I will give your suggestion a try. After all, I've nothing to lose by it. Will report back if and when.

Nick. You may well be right. Weld splatter is not very pretty.

John

Although running a tap down partially broken out hole can, and does, work its tricky operation at the best of times as the tap will not only try to run out sideways through the broken bit but also attempt to jam up in it. How great the problem is depends on the depth of the broken out bit relative to the thread. If the broken out part is deeper than the thread its likely to be a battle. For a similar issue I was advised to clamp a piece of light alloy over the break and run the tap down. Theory was that the alloy would keep the tap sufficiently straight. Probably used a second cut tap. It seemed to work adequately but on reflection I wasn't over happy so welded it up for a do-over. At least I didn't have worries about body distortion affecting precise dovetails. Re-drilling the hard weld posed its own problems. Milling out a clean slot so all the re-work is in weld sounds to be a good approach.

i'm pretty sure that given a bit of practice I could have nailed the technique for straight tapping partially broken out holes to give more than acceptable results. But for something I never expected to do again the effort seemed disproportionate especially as by the time I needed to do it again I'd have lost the technique. Currently running at less than once a decade on that particular problem. Possibly because having discovered what right pain in the posterior fixing it is I tend to take a bit of extra care.

Clive.

Using a spiral tap might make threading such a hole easier. That is the way I would go, if I had gotten that far with the project. I would avoid welding because of the distortion and redrilling problems. I might even clean it out as a slot or dovetail and simply replace the area with an insert (grub screws at the edges would hold the new piece in).

Clamp a piece of metal against the gap then tap?

Geoff - Been a long time since I posted.

Do I understand that there will eventually be a pin sticking out of this hole? If so how about machining the existing hole into a rectangular slot, with the centre of the slot where the centre of the pin should be, then make a pin square one end, round the other , set it into the slot and put screws through to hold it in place. All a bit of a tricky set up, but the worst is that you have to have a few attempts at the square/round bit. In fact you could make the first deliberatley undersize, fit shims to get it in the right place, then make the final one to correct geometry.

I'd regard welding as a last resort, it could easily cause distortion to what you've already machined.

I bet you're all busting to know what cock-up I'll make next, aren't you? Decided to try the Michael Gilligan approach first and did as Geoff suggested and clamped a bit of steel to the edge before tapping. As I've only got a plug tap in 6mm, I had to go a bit careful-like. Didn't want to end up with a broken tap end to get out as well. As a consequence, I couldn't get right to the bottom of the hole, but near enough. After a clean up with an end mill, I'm at the stage you see below:

Not pretty, I grant you, but I console myself with the fact that it doesn't take any great strain in operation, serving only to locate the idler gear; neither will it be visible when assembled. Unfortunately, I know it's there and I can't erase that from my memory. I might even pop a bit of J-B weld in for cosmetic reasons! Now that would be ironic!

I'm taking a rest from the garage to watch a bit of Wimbledon, but I hope to continue the saga tomorrow.

John

Hey, we aren't doing this because we're dainty are we? Nahhh, rough work is ok by me. It's nothing compared to the state of some of my things, you should see my bench vice.

Michael W

Job's a Good 'un, John

MichaelG.

The bane of all (or most!) of us, John

Good luck,

Roger

So you can see some thread ?

Why not warm it up with a gas torch and flow some solder into the voids then clean up afterwards?

And finally..........

Following a brief exchange of emails with a gentleman at the J-B Weld UK importers, I have come to the conclusion that I can't explain it! Possible reasons are contamination, insufficient curing time or too low a curing temperature. I have mixed up a much larger amount (about 5cm of each), used a minute amount to clean up the exposed threads and left the rest to cure. I popped the repair in the oven after dinner to speed things up a bit, to no avail. (Temp around 40 to 50 degrees C.) Next day, I'm still able to shave bits off with a hobby knife. Now, some several days later, the remainder, left to cure in the unheated garage, is still plastic. Time to buy a new welder, methinks!

To be fair to J-B UK, they were very sympathetic and have very kindly sent me a replacement two-pack of J-B Weld original recipe. I haven't made any more mistakes on which to try it yet, but it's only a matter of time!

John

I have used the J/B Weld original for many years, since 2003, and have never had a failure of the mix to set. I measure out equal volume of each. Then mix usually with a tooth pick or bamboo stick. Mix very thoroughly then apply. I have not used it in cold conditions. In winter I bring it inside the house, summer in the shed is fine. For a faster cure, I place the items in a small bench top oven and set it to the defrost setting of 40C to 50C and leave it for 6 hrs and it is set. I find with most glues and epoxies, if they are at 18C or higher they mix and set better than if they have been colder at say 12C or colder. Don't mix epoxies with anything Teflon or on a teflon board. The smaller the batch the more accurate you have to be. I draw around 2 small coins, and that has become my minimum mix size.

Neil

Neil (Lickfold) - Thanks for the additional information. I'll try that next time. No more need for it at the moment, although I'm going back out to continue work on the boring head after lunch - so I may not have long to wait!

John