OzarksEric
member
Reged: 07/09/08
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cast aluminum repair?
#4460354 - 03/19/11 05:22 PM
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The mount for my scope is cast aluminum I think.
Its broken. Can it be glued? or can I buy new piece? Broken mount
Anyone try those aluminum weld rods? Supposed to weld with just a propane torch?
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Trev
scholastic sledgehammer
Reged: 12/18/05
Loc: Fort McMurray, AB
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Re: cast aluminum repair?
[Re: OzarksEric]
#4460418 - 03/19/11 05:49 PM
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If you can find someone with a high frequency mig welder they might be able to fix it, cast is very touchy to repair.
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mikey cee
Postmaster
Reged: 01/18/07
Loc: bellevue ne.
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Re: cast aluminum repair?
[Re: Trev]
#4460434 - 03/19/11 05:59 PM
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I'd drill small holes into both pieces for the JB Weld to grab. JB Weld is so strong that I could literally bust castings trying to undo the stuff. It's much under appreciated by those who have never used it or better yet used it wrongly.  Mike
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rtanton
Vendor (Explorer Scientific)
Reged: 02/06/07
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Re: cast aluminum repair?
[Re: OzarksEric]
#4460436 - 03/19/11 06:01 PM
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I have had success with JB Weld epoxy (standard not quick set).
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Bart
Carpal Tunnel
Reged: 05/28/06
Loc: Somewhere near Charlottesville...
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Re: cast aluminum repair?
[Re: rtanton]
#4460522 - 03/19/11 06:56 PM
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It's my humble opinion that JB Weld wouldn't be strong enough for the type of break that Eric has. I think taking it to a welding shop would probably be his best bet.
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RTLR 12
Post Laureate
Reged: 12/04/08
Loc: Capistrano Beach, Ca
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Re: cast aluminum repair?
[Re: Bart]
#4460526 - 03/19/11 06:59 PM
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Take it to a welding shop and get a professional opinion. You are gambling your OTA that the repair does not fail!
Stan
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Jon Isaacs
Postmaster
Reged: 06/16/04
Loc: San Diego and Boulevard, CA
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Re: cast aluminum repair?
[Re: Bart]
#4460530 - 03/19/11 07:00 PM
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It's my humble opinion that JB Weld wouldn't be strong enough for the type of break that Eric links to. I think taking it to a welding house would probably be his best bet.
It looks like it failed at location that was already weak. Unlikely glue would work, welding might but it's pretty questionable and would probably just break again... 
What mount is it? Maybe a spare is available.
Jon
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Bart
Carpal Tunnel
Reged: 05/28/06
Loc: Somewhere near Charlottesville...
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Re: cast aluminum repair?
[Re: Jon Isaacs]
#4460540 - 03/19/11 07:05 PM
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He might have to bite the bullet and have a new one milled.
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jmiele
Patron Saint?
Reged: 12/04/10
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Re: cast aluminum repair?
[Re: Jon Isaacs]
#4460549 - 03/19/11 07:10 PM
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Aluminum can be welded. What about getting a used replacement piece?
Good Luck
Joe
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Trev
scholastic sledgehammer
Reged: 12/18/05
Loc: Fort McMurray, AB
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Re: cast aluminum repair?
[Re: jmiele]
#4460579 - 03/19/11 07:27 PM
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Cast aluminium cannot be welded like regular aluminium, cast has a slightly higher carbon content and isn't annealed or extruded so it doesn't have anywhere near the same strength.
JB Weld is useful but I would hesitate using it somewhere where it would cause damage if it broke again.
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avarakin
Carpal Tunnel
Reged: 07/13/09
Loc: Parsippany NJ, USA
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Re: cast aluminum repair?
[Re: OzarksEric]
#4460803 - 03/19/11 09:32 PM
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Based on signature of OP, it looks like his scope is a cheap 70mm F10, so even if the mount fails and the whole rig goes down and breaks, probably no big deal.
How about this:
1. drill and tap couple of ~M6 screws. Looking at the picture, I think it should work
2. glue with JB Weld
3. put in the screws
I think this should provide very good combination - screws to hold things together and glue to fill all the gaps
Alex
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Eddgie
Postmaster
Reged: 02/01/06
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Re: cast aluminum repair?
[Re: avarakin]
#4460905 - 03/19/11 10:29 PM
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I am inclined to agree that welding is not an option, and epoxy is unlikely to hold.
Your suggestion I think is the right one, but I would go further than just two screws.
Better would be maybe three screws.
OR...
Drill holes all the way through on a press (a drill should go through this easily) and do long bolts with nuts on the ends.
I agree though. Screws would be the best way to fix this.
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Billydee
professor emeritus
Reged: 01/23/08
Loc: Winter Haven, FL
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Re: cast aluminum repair?
[Re: Eddgie]
#4460958 - 03/19/11 11:12 PM
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Probably the three screw option + the JB Weld + a pipe clamp around the whole thing. That large screw in the picture looks like it puts major tork on that one side.
Luck, Bill
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Bart
Carpal Tunnel
Reged: 05/28/06
Loc: Somewhere near Charlottesville...
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Re: cast aluminum repair?
[Re: Eddgie]
#4461005 - 03/20/11 12:01 AM
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I am inclined to agree that welding is not an option, and epoxy is unlikely to hold.
Your suggestion I think is the right one, but I would go further than just two screws.
Better would be maybe three screws.
OR...
Drill holes all the way through on a press (a drill should go through this easily) and do long bolts with nuts on the ends.
I agree though. Screws would be the best way to fix this.
I'll second that!
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DavidD
professor emeritus
Reged: 07/23/09
Loc: Phoenix, AZ
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Re: cast aluminum repair?
[Re: Bart]
#4461084 - 03/20/11 01:15 AM
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Is this the dovetail shoe? If so, you can buy a replacement rather inexpensively. The only issue might be finding one with the same sized hole in the middle, though it's relatively easy to drill a larger hole if needed. Anthony at ADM can probably come up with a custom made part, or you could start with something like this:
http://www.optcorp.com/product.aspx?pid=12611&kw=dovetail&st=2
David
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OzarksEric
member
Reged: 07/09/08
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Re: cast aluminum repair?
[Re: DavidD]
#4461605 - 03/20/11 10:56 AM
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Yes its the shoe. It is about 1 3/4 in across. Would that fit the OPT Dovetail Mount Adapter - Female? My scopes Dovetail shoe
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OzarksEric
member
Reged: 07/09/08
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Re: cast aluminum repair?
[Re: OzarksEric]
#4464146 - 03/21/11 01:19 PM
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I sent an email to liquidnails
I need a glue to repair two cast aluminum pieces. Will need to hold 10lbs.
Here was the answer
I would recommend one of our polyurethane adhesives (in addition to permanent mechanical fasteners) listed below along with where-to-buy information.
LIQUID NAILS FOR MARBLE & GRANITE (LN933) is a polyurethane adhesive. It is sold at Home Depot and Lowe's. It is Home Depot stock #562-222 and Lowe's stock #267707.
LIQUID NAILS POLYURETHANE (LN950) is available at the following retailers:
ACE Hardware: LN950 is stock#1260454
Do-It Best Hardware: LN950 is stock#265929
True Value Hardware: LN950 is stock #603136
Cure time for the polyurethane adhesives is 12-16 hours.
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PHampson
sage
Reged: 10/25/05
Loc: Nashville, TN
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Re: cast aluminum repair?
[Re: OzarksEric]
#4464178 - 03/21/11 01:39 PM
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Looks like a standard Vixen dovetail - 1.7 inches wide - so, yes, looks like it would fit the OPT shoe. You'll have to work out if the OPT shoe will fit on top of your mount. You might call or email OPT to find out the hole dimensions, etc. Something like this would be much preferred over gluing up an already broken part that was obviously weak to begin with. Good luck with it.
Paul
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Midnight Dan
Postmaster
Reged: 01/23/08
Loc: Hilton, NY, Yellow Zone (Bortl...
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Re: cast aluminum repair?
[Re: OzarksEric]
#4464441 - 03/21/11 03:37 PM
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I need a glue to repair two cast aluminum pieces. Will need to hold 10lbs.
The 10 pound weight of the scope is not what the glue has to hold. Being part of a dovetail seat, the clamping screw puts an enormous amount of pressure on the parts - FAR greater than 10 pounds.
My personal opinion is that no glue, including JB weld which I've used before, will hold up to the stresses involved in this particular part. Drilling and pinning (or screwing) *may* help, but there's issues there too. Drilling removes material and makes the overall part weaker than before.
You might get away with drilling, pinning and glueing with something like JB Weld. But any way you look at it, that's a high stress point and the chances of success are fairly low. If there's any way you can replace the dovetail seat, that would be the way to go.
If you can get a flat-bottomed dovetail seat, you might be able to saw off the other ear of the broken dovetail seat, file the base flat, drill some holes through it, and bolt the new dovetail seat onto the base. That would allow you to mate the dovetail to your mount using the circular base part of the existing (broken) dovetail seat.
-Dan
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frolinmod
Pooh-Bah
Reged: 08/06/10
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Re: cast aluminum repair?
[Re: Midnight Dan]
#4464489 - 03/21/11 03:57 PM
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It's probably going to be less expensive to replace this part than any other sort of futzing around you might be thinking of doing. If you can't obtain a replacement part, you can have a local machine shop re-create it. Perhaps this time out of steel or at least a better grade of Aluminum. You're looking at maybe a $200 bill here if you have to have it machined.
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