I have to bond a metal collar with a 1/4" center hole to an acrylic block with an identical hole and align the holes precisely before the adhesive dries. This is to link a CMR turntable's table to the motor's drive shaft, so the bond must be strong
I can use Elmer's Sitx-All silicone adhesive or thin CA. The Stix-All will allow precise positioning with it's 20' skin time, but I'm not sure how strong the bond will be. The CA will produce a strong bond but may set before I can align the holes precisely. I can align the parts with a 1/4" dowel, but I'm concerned that if I use CA the CA will run and bond the dowel, at which point suicide will be my most attractive option.
I'd appreciate any advice--thanks.
Rick Krall
Rick - Try wrapping a piece of waxed paper around the dowel before applying the CA . If the CA does leak it won't stick to the dowel and should be a simple matter to lightly sand off any wax paper that does stick.
Otto
You could also soak the dowel in a wax mold release agent. Or maybe rubbing the dowel on a candle.
But if the dowel does stick, could you just drill it out without damage to the other parts?
Elmer.
The above is my opinion, from an active and experienced Model Railroader in N scale and HO since 1961.
(Modeling Freelance, Eastern US, HO scale, in 1962, with NCE DCC for locomotive control and a stand alone LocoNet for block detection and signals.) http://waynes-trains.com/ at home, and N scale at the Club.
Good suggestions, Otto and Elmer. In thinking about the issue, I had another thought--positioning the parts precisely and applying the CA to the perimeter of the collar. Would it wick into the joint, and, if so, do you think the bond would be strong?
Rick
fkrall Good suggestions, Otto and Elmer. In thinking about the issue, I had another thought--positioning the parts precisely and applying the CA to the perimeter of the collar. Would it wick into the joint, and, if so, do you think the bond would be strong? Rick
CA will produce a strong bond, however, if the is any flexing, torque or other forces exerted on this piece the "brittle" CA bond could fail. Epoxy or Polyurethane (Gorrilla glue) would be a better choice for bonding these 2 dissimilar materials. I prefer epoxy, the polyurethanes can expand as they set. The waxed or otherwise protected dowel is a great idea for the exact positioning.
Modeling B&O- Chessie Bob K. www.ssmrc.org
Instead of using dowel for alignment, use 1/4" brass tubing and lightly coat it with oil before inserting.
Wayne
I second the use of epoxy over CA, this will be a moving joint and CA< while strong, is also rather brittle. Ultimately strength-wise, the part will break before the bond, but vibration and CA don't mix. Epoxy won't run, so unless you slop it on in excessive quantities, you can leave a clear spot where the alignment hold is so it will not bond the alignment dowel, yet the joint will be more then strong enough even with the small 'missed' spot.
Or perhaps a little outside the box thinking - something like latex caulk. Depending on the materials to joined, it will form a strong but flexible bond. ANd with a slow setting time, you will have ample opportunity to remove the alignment dowl before the adhesive sets, even if it does get in the area of the hole. You'll have at least 20 minutes to remove the dowl after attaching the parts - just don't move anything until at least the next day aterwards.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
Great input on CA--I wasn't aware of its sensitivity to vibration. That puts Stix-All front and center; it's silicone-based, presents a good balance between strength and flexibility, and gives me plenty of time to make the alignment. The alignment is not a big deal unless CA's involved with its instant cure. DAP Kwik Seal latex caulk is an ingenious alternative as well. I have plenty of both.
In my limited experience I have found that the best way to fasten one flat surface to another where shear forces may be present is to pin it in place in conjunction with whatever glue you choose.
My $.02
Mark
I would also recommend epoxy (JB Weld or JB Quik). I would not trust any silicone type adheasive as they do not make a tight enough bond and are too flexible especially in a toque type situation.
Jay
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How big is the metal collar? Is there room to drill two holes thru and put pins or small screws into the acrylic block? This could be in addition to one of the epoxy adhesives. I would definately use some form of mechanical connection where a shear load is involved.
-Bob
Life is what happens while you are making other plans!