Thumb Screws From A Combination Of Materials

[Ripthorn]

I recently tried making a pair of thumb screws that used aluminum as the wheel and steel for the threaded stud. However, neither red loctite or epoxy seemed to hold really well. Is there a preferred technique or adhesive for making a permanent connection on dissimilar materials? Could it just be that I did not adequately clean the surfaces? The steel was black oxide and the aluminum was plain old 6061.

 

[David S]

I often make something similar by pressing steel SHCP into an aluminum wheel or knob. The linear knurling on the SHCP heads make for a good secure press fit.

David

 

[kingmt01]

I second what David said adding that a helicoil may be a good idea as well. Steal in aluminum can react not allowing your screw to ever come back out.

 

[Bill C.]

Have you considered using a rolled pin to hold the two parts together if they are large enough to do so?

 

[TOOLMASTER]

DON'T thread the alum all the way so the stud gets tight when forced into the slightly taped part..and red locktite

 

[RJSakowski]

I recently tried making a pair of thumb screws that used aluminum as the wheel and steel for the threaded stud. However, neither red loctite or epoxy seemed to hold really well. Is there a preferred technique or adhesive for making a permanent connection on dissimilar materials? Could it just be that I did not adequately clean the surfaces? The steel was black oxide and the aluminum was plain old 6061.

Super glue or cyanoacrylate glue makes a permanent joint. Is is not as heat resistant as red LocTite but sets quickly. I used to use it on screws and nuts for production assembly and many times the screw would shear before the bond broke. I have also used it for extension drills by making an extension shank and drilling a socket for the drill bit and inserting the drill bit. I have never had one fail with this technique

Should you want to separate the two at a later date, heating with a heat gun or soaking in acetone will break the bond. You can apply on the external threads and assemble quickly or apply to the base of the connection after assembly and let it wick in. Use the water thin type.

Bob

 

[Ripthorn]

Thanks for all the suggestions. These will be parts that won't have tons of torque, but that will also be decorative, so cross pinning is definitely out. I could probably get away with the approach of cranking the stud in since the hole will be blind and then using loctite or super glue.

 

[David S]

Here is a small one I made by pressing a hex head screw into a blind hole in the knob. No loctite.


David

 

[T Bredehoft]

Loctite offers Locktite 7649 Priming liquid. The bottle says it accelerates the cure, It also may have a cleansing function. It comes in a small brown (amber) bottle with a brush.

 

[joshua43214]

Red Loctite should give you a permanent bond.
You are probably just not getting it clean enough.
Try cleaning the parts with acetone and blowing them off with compressed air.
if you want to be really fussy, wear gloves. finger prints can interfere with the bond. I personally never get that fussy, I just avoid touching the parts after they are clean.
You also want to do this right away on a freshly machined surface for best results. Aluminum oxidizes very rapidly. If the parts have been sitting around for a while, clean the oxide layer off with some very fine abrasive like 3M pads or even scrape with a sharp knife.