Using JB Weld

[Alan Haisley]

It seems like a lot of this stuff gets used, but noone provides a lot of (any) detail about just how to go about it.

1) How do you prepare the surface?
2) How do you prevent or minimize dripping?
2a) Do you use tape or clay as a dam?
3) Cure time before drilling, milling, turning, sawing, etc.?

Alan

[GailinNM]

Some helpful info on JB Weld.
http://www.jbweld.com/pages/faqs

Gail in NM

[Jo]

For preparation I treat it like any other glue: degrease and remove dust particles.

JB Weld slumps, so it is best kept flat or prevented from moving around. I use tape as a dam round edges and sometimes on top of it.

Time: minimum of 24 hours, longer is better. Cleaning off the excess is easier when it is not fully cured. i.e. if I am filling holes in the bed of a machine after 6 hours you can use a flat blade to cut away the excess.

Jo

[Jasonb]

Same as Jo says.

I only really use it for structural or heat resisting jobs, anything cosmetic is easier done with car body filler (bondo) as it's far easier to sand down, quicker setting, cheaper and does not have the slump problem of JBWeld

[Ramon Wilson]

Hi Alan, as a long time user of JB I've never given thought to mention the the questions you raise.

I always prepare the surface by cleaning with acetone or similar solvent.

The product itself is not thick enough like some epoxy steels to prevent 'slumping'. You can use Colloidal Silica with epoxy resin to act as a thickening agent but whether this would have a derogatory effect on JB's great properties I would not know. Though I have considered using it I have always come down in favour of two (or more) layers to build up any losses due to slumping.

You could use tape as a masking agent but it would need to be removed before the product begins to set. I guess a clay like substance - plasticene or similar? -  would be ok to use too.

In a warm environment  it will usually set with 3-4 hrs but will not cure for a full 24. Personally I prefer to leave it as long as possible before machining as it does appear to continue hardening after the 24 hrs is up.

Hope that helps some

Regards - Ramon

[tel]

I'm with Jason, not a big fan of the stuff at all, though it has its uses.

[fumopuc]

For later powder coating of a part I have given some iron powder on the still wet surface, so it will be electrically conducting for the powder coating process after curing.

[Brian Rupnow]

Alan--I use j.b. weld with a fair degree of success, but you have to realize that despite the name, it is only a good quality epoxy with a lot of iron powder in it. I don't do any surface prep, but I suppose roughening the surfaces to be joined with some 220 grit sandpaper prior to use would help the adhesion a bit. I clean both surfaces to be joined with laquer paint thinner to remove any traces of oil. As others have said, j.b. weld is quite "runny" so if you want to build up an area, then you can use masking tape or Plasticine for a "dam". It is imperative to wait at least 24 hours before trying to do anything with it, and as previously said, "longer is better". Heat from a 60 watt light bulb hastens the drying time somewhat. I recently used it for gluing ends into a model engine gas tank, and as a test I submerged some j.b. weld in a container of Naptha gas for 72 hours and found that gas does not soften it in any way. ---Brian