Work Holding Trick. Super glue and masking tape.

[Perry]

I'm sure some of you know this trick already. I just learned about it from another metal worker site who got it frorm the first link. Sure beats super glue by itself.

This video shows using the trick for woodworking, but it does work on metal also.

Jump to 4:26 ish 13:29 is interesting also.

There are metal working sites that also show this used.
This site claims to have refined the process....

I did notice most of the metal working sites use the blue masking tape.

 

[Tom O]

I’ve used the green tape with no problems.

 

[PeterT]

I got introduced to CA glue for metal work holding through Clickspring videos. I noticed his backing surface is almost never completely flat, he usually cuts a series of grooves to make annular rings. I always assumed this was more about reducing the surface area a bit & so that the bond wasn't too much of a good thing. He goes straight to the blowtorch or heat gun though for disassembly.

I'm not exactly sure what the painters tape is about. I'd like to hear if you guys have tried regular masking tape or other kinds of tape. I have a theory. CA ideally likes some degree of open porosity for good bonding. Two pieces of balsa wood bond aggressively & instantaneously with a small puff of dramatic exothermic smoke for good measure. Two pieces of hard plywood (denser, less porosity) is a slower reaction, typically has to be held clamped for a bit unless you use accelerator on one surface. Two pieces of metal (zero porosity) slower yet. In fact I've had metal parts fall off as I was turning in the lathe that were completely cured along the edge but still uncured in the middle. I wonder if the Clickspring mandrel grooves are more about allowing internal air gap to mitigate this? Maybe the painter tape is giving some porosity? It might also assist with peeling off glue residue which is a pita. There are much stronger double stick tapes, but the downside is they are designed to be permanent; quite impervious to solvents & heat can be a real mess as they wont let go until they are burning.

I was actually amazed NYC was able to get away with those cutting forces. Hogging on the upper edge of the tall block means he is putting tension on the glue joint. Glues are universally not great in tension, they are best in shear. So a thin part would stay put better than a thick part all things equal. I can see some down sides too. You can have a super CA bond between part & tape, but now you are entirely at the mercy of the tape's adhesive & the fixture plate. Generally painters tape (or tapes like that) use lower tack glue so it peels off easier & doesn't take underlying finish with it. Maybe its thin viscosity CA & its soaking in a bit? Clickspring uses quite thick viscosity CA, approaching a gel.

FWIW acetone will soften CA but its not nearly as effective solvent as what they specifically sell as de-bonder. Also, cutting fluids like the ones favored for aluminum including WD-40 are really effective at completely removing tape residue - and therefore can also work their way into a CA bonded joint & risk letting go while machining.

I dunno. I think CA for sure it has its place. But a cnc shop on a large part? You can buy 10 Mitee-Bite clamps for $50 & swap in a part faster than you can tape & spread glue, nevermind glue cleanup or risking a $$ part or $$$ cutting tool flying off?

 

[6.5 Fan]

An interesting tip for sure, i have watched NYC using it and was a bit sceptical. Someday it will come in handy.

 

[Perry]

Some of the "stunts" I've done could only have been completed with crazy glue. lol I work with some pretty small pieces and there is very few ways to hold them.
I haven't tried the tape method yet, but I can see where it will solve a few of the issues of crazy glue alone.

@PeterT, In one of his videos, Clickspring does mention to add the grooves to allow the crazy glue to cure faster.


Another one that I've know about for a long time but was reminded when searching video on the carzy glue and tape trick is the crazy glue and baking soda. Not a work holding trick, but great for small repairs for the handy guys in the group.

 

[DPittman]

I've used permanent loctite numerous time to hold pieces for machining successfully.

 

[PeterT]

The baking soda thing is one of those 'controversies' that have been debated for a long time. There is no doubt it accelerates the cure and acts as a type of structural filler. The question is how much is due to the chemical composition of baking soda & how much due to the particle size that offers substantial surface area which is part of the accelerated cure. For example microballoons (microscopic glass spheres) are used extensively in the composites & hobby industry to add low density bulk to resins & such, for example light weight fillers, paste, putty... that can be used to bridge gaps, fillets etc. Anyways if you put a drop of CA on microballoons, you get the almost identical reaction as baking soda. It gets hot from exotherm & turns a little pile into something that feels like a chip of glass. Even sawdust in a crack is beneficial to CA as a glue joint.

http://scienceline.ucsb.edu/getkey.php?key=459

But if you want an outright accelerator, then just buy what is specifically formulated for it. In CA lingo it susually called 'kicker' or 'accelerator'. In Loctite lingo its called 'primer' or 'promoter' but is slightly different in its application.

ps - I've tried the tape thing myself & and results vary. For one thing there are all kinds of 'paint tape' on the market. Some are paper based, some are plastic/vinyl based, some are a blend or mix of the two. CA actually does not work well on many kinds of plastics so that might explain variation in bond. Thats why I wasking about old school masking tape which I think in still mostly paper based but probably still other resins & binders in there.

Anyways, I'm happy to use CA on smallish things stuck to a mandrel. As the parts get bigger or more valuable, I am reluctant to to risk fly-away. Another technique I see used is is bedding a part in epoxy (hardware 5 min is fine). It completely conforms to whatever odd shape. Then you can machine other features. Once done, just use a heat gun to soften & out it pops. Here you have much more lateral 3D support because the goop is 'potting' the part. It also requires much less heat to soften & distort to th epoint the part can be popped off.

 

[PeterT]

Epoxy potting technique for 2 sided cnc milled parts.
Pics from HMEM, Terry.M quarter scale 'Offy' engine con rods.