JB Weld

[Ron LadenParticipant @ronladen17547]

I have never considered model engineering to be a long painful experience, I,m afraid if I did I would be long gone. I think I have a reasonable level of patience but it's not unlimited.

I also have a DRO set on my mill, I have used laser cut parts and I use and am a big fan of JBWeld (original) but I don't think that means I am cheating. To date apart from flywheels I have not used castings but made parts from bar stock. Everyone to their own but for me producing quite complex parts from solid against machining a preshaped casting is far more satisfying and if that means a fillet of JB to give a cast look in places that's fine.

I have found JBWeld to be excellent, I have turned, it milled it, drilled and tapped it with no problems. I have used a couple of other metal filled epoxies but they were not as good as JB original. One of the things I also like about it, is its longer cure time I,m sure that gives a stronger joint/material than the rapid set types.

Edited By Ron Laden on 18/03/2021 05:52:03

[Ramon WilsonParticipant @ramonwilson3]

Hi Bill,

'Too old and too slow' eh – yeh I really know the feeling. I returned to flying C/L about six months before the lockdown and found it difficult to keep my balance – not dizzy but definitely unstable at first. I was just beginning to find my feet (pun intended) when lockdown struck. I'm hoping however to try our local common again next week where I haven't flown for many a year. I shall only take a 1.5cc powered Talisman – wonder how long it will take the Nay Sayers to zoom into our patch!

Ron – interesting to hear your comments on that you've turned JBW and tapped it. I've milled it of course but not tried those ops. I would imagine the turning to be no different to the milling but how did the tapping actually go? Was this into solid JB and how did the thread(s) stand up if so. I'd certainly be interested to hear your findings on that.

Regards – Tug

[Ron LadenParticipant @ronladen17547]

Hi Tug

I have repaired 3 threaded holes, the first was a M2.5 where I drilled clearance instead of tapping size, I opened up the hole (blind) to 3.0mm and packed it with JB making sure it was full with no trapped air. Let it cure for 48 hours and then drilled 2.1mm which is a tad over and tapped it clearing the tap regularly.

I used the same procedure repairing two stripped M4 holes in a friend's lawnmower casting which I opened up to 6mm before packing with the JB.

In both cases the screws tightened well though I was a bit cautious but I went with what I thought correct for the size and they were fine. It's also worth noting that in both cases the screws would seldom be removed. What the JB thread would be like with screws that are regularly removed and refitted I can't say but providing it's not a heavy duty job and the fixings are not over done it could be ok.

Ron

[not done it yetParticipant @notdoneityet]

I would expect a helicoil insert to be preferable fitted into drilled JB Weld. Questionably a more usual thread repair than undertaken by Ron – but it worked all the same.

Optimum conditions are strictly adhered to by commercial twin-pack users – proportions, mixing, temperature control, dispensing time limits, curing times, surface texture and cleanliness, thickness of the joint, etc(?) – and will likely be better than most of us can attain in our workshops/kitchens/lounges.

Manufacturers claims are always those attained under ideal conditions. That said these types have given more than satisfactory performance on many a job in the past. I would not use it on all jobs without some ‘braces’ attached (as in ‘belt and braces’🙂 ).

[Ramon WilsonParticipant @ramonwilson3]

Thanks for that Ron that's an interesting use of JB and shows another of it's capabilities. Something to bear in mind for the future

Though I would agree that a helicoil would be the better option NDIY that does mean one has to have the right helicoil insert to hand along with the relevant helicoil tool. A couple of tubes of JB on the other hand can sit there for use on all sorts of occasions.

It goes without saying that any manufacturers claims are based on optimum conditions but for this product and similar – attention to cleanliness, correct proportions of base material and hardener, and thorough mixing are easily attained. Gentle heat as mentioned previously is not specifically necessary but does help the cure time and possibly the cure strength.

Patience however, to ensure a full cure before stressing the item by machining etc, is down to the individual of course

Regards – Tug

[Ron LadenParticipant @ronladen17547]

I also agree that a Helicoil would be a better fix and I did also consider making a metal plug after drilling out the holes but the JB worked well on the small M2.5mm and considering the lawnmower holes only held a cover I thought I would give it a try.and it worked. I always have JB on the shelf and as you say Tug it saved the bother and expense of buying Helicoils and the appropriate tool.

If I had a part or repair that was built up with JB and that area required some threaded holes I would have no hesitation in drilling and tapping it providing the fixings were fairly permanent once fitted.

Ron

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