PDA

View Full Version : using crazy glue to hold parts to machine



Carld
10-23-2009, 11:43 PM
I am building a PMR #5 vertical steam engine. I am getting ready to drill and tap the crank bearing caps so I can bore the crank bearing holes. They are small and the only way to hold them while I spot them and drill the cap and main frame. I don't want to use epoxy to hold them because I may have to get it to hot to remove them.

I got to wondering, maybe crazy glue breaks down at a low temp. Does anyone know what temp it would come loose at? All I can find is about 300 deg F.

I am starting to think about soldering them in place because I will have to drill and bore or ream the bearing journals. The super glue may break loose during machining.

Walter
10-24-2009, 12:36 AM
Carld,

I routinely use super glue to hold parts and pieces for machining. I've never had a problem with drilling parts super glued together. The majority of what I use glue for is attaching small parts to a holding rod so that I can file in small details. I also use the same setup to sand and buff those small parts. (Much like how a jeweler or stone cutter might do)

I do take good care to keep the parts from getting hot as the glue will fail. Just this week I actually was in a position where I had to crank out a part and had no time to make a proper fixture. I resorted to super glue and did the work I had to do (grind a .75" radius on a rectangle shaped part on the surface grinder in the spindex).

As long as you use care to avoid extreme loading you should be fine. try it on a test part first =)

I can't really speak on the crazy glue as I don't much use it.

Evan
10-24-2009, 12:52 AM
Cyanoacrylate glue will hold really well but it won't take hardly any heat. It forms acrylic plastic when it cures and has a low melting point. I use it frequently to fix things in place temporarily. It is initiated by water in the air and on the part so before you apply it the part must be clean but not chemically dried such as rinsing in alcohol would produce. I always give the parts a breath to condense some moisture on them before applying.

If you ever end up in a situation where the glue just won't set then give it a very light dusting with sodium bicarbonate. The chemical is a hydrate and the water in it will instantly fire off the glue.

Pete F
10-24-2009, 02:40 AM
Thanks Evan, that is really good to know. I use CA glue for model building, and when it doesn't set right the first time, I find it is really hard to get it to stick afterword. Perhaps a light breath on it before trying again will help? Or the bi-carb trick. Or get my dog to breath on it - that always seems like humid air.

You know what my daughter uses CA glue for? Hardening the wooden shanks of her (ballet) pointe shoes. Apparently, once you get them broken in to just the right shape, you don't want them to move anymore, so they soak them in CA. Future floor wax is another favorite for this.

-Pete

Evan
10-24-2009, 03:30 AM
For model building when you need a really strong joint lay in a fillet of bicarb with your finger. Then soak it with very low viscosity CA glue and stand back. It will go off with smoking fumes that you don't want to breath or get in your eyes.

Something to be very careful about is that the thickened CA formulations may contain isocyanates. Isocyanates are potent allergenic sensitizers and a single exposure can make you permanently sensitive to the chemical to the point you cannot ever come into any sort of contact or breath even a trace of it in the future without a potentially fatal reaction.

Do not breath the fumes from any sort of glue that polymerizes when it sets including CA, urethanes (contain isocyanates) and epoxies.

Carld
10-24-2009, 01:49 PM
Thanks for the replies and I use the CA for model building and use the baking soda trick too. I just never tried to use it to hold parts while machining but it appears it will work.

I intend to drill and tap the bearing caps and base and put the screws in to help hold them together while I drill and ream the crank bore. I may use my coolant mister to keep things cool.

It looks like I have a plan. Thanks

chrisfournier
10-24-2009, 02:21 PM
If you check out "Satellite City" you will see that they produce an accelerator and a solvent for crazy glue. I have found both of these products to be very useful over the years on wood, metal and glass. The accelerator gets you a good bond the first time and you can spray it on the parts prior to gluing or after the parts are inplace and the glue has been applied. The solvent will get your set up apart without heat.

I've used crazy glue for a mic fixture that I use to actuate valves on motorcycle heads while they are on a flow bench - aluminum to aluminum bond.

Clean both surfaces with acetone first for the best adhesion.

I've noticed that the crazy glue bond is most susceptible to jarring impacts. If your tooling catches while you're machining I think that things will go to pot very quickly. I'm sure that you can likely avoid this but I bet that a squealing reamer would be very tough on this glue joint...

Carld
10-24-2009, 03:05 PM
I have the accelerator and debonder and I was leary of heat or shock but it I thread both parts and screw them and use the mister coolant it should work. The parts are brass so cutting should not be a problem. What I will have to watch is the drill or reamer grabbing.

John Stevenson
10-24-2009, 03:19 PM
One method of holding for machining, usually drilling, that has been used for years but still works well is to paint one part with white PVA wood glue then stick a strip of what we know as cartridge paper or old fashioned drawing paper.

Paint the top surface with the glue and place your second part on, clamp and leave.

When set you can machine these parts and by pouring boiling water over them they will free off and they can be cleaned easily.
Small parts can be 'boxed' in by packing pieces with a greater surface area to hold them.

We used to use this method for gluing and clamping 3 strips of metal to make boxway slides up, when drilled and tapped whilst glued together the holes were perfect.
I have even glued thin shim to faceplates by this method as it supports all over and comes off so easy without having to tug at the shim afterwards.

As I say it's a very old method but seems to have got lost in time.

.

gary hart
10-24-2009, 03:24 PM
Just did something similar. Didn't use CA glue because of shock and grabbing and didn't want to use soft solder because need to silver braze later. Used cheap 5 minute epoxy. Held very good, but took lots of heat to free the part when removing. The part is about 1/4" square copper for spacer between fire box and boiler shell and had to be the right thickness.
http://img.photobucket.com/albums/0903/ghart3/Models/American%20LaFrance%20Fire%20Engine/FireDoorspacer003.jpg
http://img.photobucket.com/albums/0903/ghart3/Models/American%20LaFrance%20Fire%20Engine/FireDoorspacer005.jpg