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Old 05-10-2015, 09:57   #1
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Aluminum brazing

This is no boat related. I was trying to reassemble the engine on a 1986 XL250r dirt bike. One of the bolt holes has had most of its threads removed. Don't want to buy a $56 helicoil kit for a m10x1.25 bolt. Anyone ever use those aluminum brazing rods to fill a hole and then rethread it? I tried to use inserts but the bolt hole is too close to the cylinder and the over sized hole would have to be drilled mostly in the aluminum but also in the cylinder sleeve.
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Old 05-10-2015, 10:11   #2
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Re: Aluminum brazing

Forgetaboutit. Heli-coil it
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Old 05-10-2015, 10:28   #3
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Re: Aluminum brazing

The problem with aluminum is that it forms an oxide coating which melts much higher than the base metal. There is a specialty rod that you can use to solder with a torch, but you must scrape thru the oxide layer while laying down a bead. You won't be able to do that inside a bolt hole, and I'm dubious if it would hold well even if you could.
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Old 05-10-2015, 10:39   #4
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Re: Aluminum brazing

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Originally Posted by ryon View Post
The problem with aluminum is that it forms an oxide coating which melts much higher than the base metal. There is a specialty rod that you can use to solder with a torch, but you must scrape thru the oxide layer while laying down a bead. You won't be able to do that inside a bolt hole, and I'm dubious if it would hold well even if you could.
I saw a video online for HTS 2000 rods and they show how to do it. They also show the bolt shearing before the threads ripping out. I would just like to see if anyone has had real life experience with it. Seems like it would be good to have around in case of broken aluminum parts as well as fixing threads. Harbor Freight sells some rods I might buy some to practice and see if it works.
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Old 05-10-2015, 10:47   #5
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Re: Aluminum brazing

Charlie:

Loctire Form-A-Thread is another solution.

We've used it on tool steel molds that had hardened inserts that stress cracked the threads. Works fairly well...

Loctite® Form-A- Thread® Stripped Thread Repair -
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Old 05-10-2015, 11:02   #6
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Re: Aluminum brazing

Could you Loctite in a stud and use a nut?
I've done that with Stromberg carbs, used S/S acorn nuts, and other rodders want to know where I found the cool carbs.
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Old 05-10-2015, 11:14   #7
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Re: Aluminum brazing

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Originally Posted by Bill Seal View Post
Could you Loctite in a stud and use a nut?
I've done that with Stromberg carbs, used S/S acorn nuts, and other rodders want to know where I found the cool carbs.

I'm guessing he is talking the cylinder studs. If so I believe the only real fix is to split the cases and have the hole TIG welded, preferably a machine shop drill and tap, hole has to be perfectly straight, time sert or helicoil may work, or may fail. But brazing in my opinion is a waste of time.


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Old 05-10-2015, 11:33   #8
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Re: Aluminum brazing

Sounds like time for a machine shop, Charlie. Maybe they can put in the heli-coil, they already have the kit and just need the insert. Or maybe they can overdrill it and rethread it.


Or maybe, time to sell the bike "as is" and replace it with one better made. If it isn't worth $50 to fix...could just be better to write it off.
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Old 05-10-2015, 14:46   #9
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Re: Aluminum brazing

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Originally Posted by hellosailor View Post
...maybe they can overdrill it and rethread it...
This is not recommended on a head bolt, where even torque is essential.
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Old 05-10-2015, 16:15   #10
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Re: Aluminum brazing

Attaining the right torque might be difficult, but then again, if the OP needs that engine fixed, that's the kind of compromise that might be in order. A good machinist can do many things that expert engineers and manual-writers would tell everyone else not to do. A dry run using Plastigage instead of a head gasket, to confirm just how much tension and compression is being applied, might do well enough. (I'm not saying it would be, just that there are many "forgotten" ways to do what companies now tell you to forget and replace.)
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Old 05-10-2015, 16:25   #11
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Re: Aluminum brazing

Ryon has it right about the aluminum brazing rods. To be successful with them inside a hole will require a really good, really thorough way to remove the oxides, and you must do this immediately before the brazing. I've used these rods, I wouldn't try it unless I was stuck on a desert island with no other way off.

A helicoil will be stronger than the original thread. Maybe you can get a local shop to put one in for you for less than the kit cost. It is a 5 minute job.
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Old 05-10-2015, 18:12   #12
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Re: Aluminum brazing

You can try E-Z loks if you have enough material. They install similar to a helicoil, but don't require special taps and insertion tool. Drill out the hole, tap for external thread, screw insert in with a regular screwdriver. Mcmaster.com has them, but I can't provide a link to the page from my phone because their site is not mobile friendly.

Edit: here's a link! http://www.mcmaster.com/#97084a125/=z8or31

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Old 07-10-2015, 00:14   #13
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Re: Aluminum brazing

Quote:
Originally Posted by Zach View Post
Charlie:

Loctire Form-A-Thread is another solution.

We've used it on tool steel molds that had hardened inserts that stress cracked the threads. Works fairly well...

Loctite® Form-A- Thread® Stripped Thread Repair -
I thought about this but the torque spec is according to bolt diameter. I will see what a 10 mm bolt will handle.

Quote:
Originally Posted by Bill Seal View Post
Could you Loctite in a stud and use a nut?
I've done that with Stromberg carbs, used S/S acorn nuts, and other rodders want to know where I found the cool carbs.
Interesting thought. Will look at that for a solution.

Quote:
Originally Posted by hellosailor View Post
Sounds like time for a machine shop, Charlie. Maybe they can put in the heli-coil, they already have the kit and just need the insert. Or maybe they can overdrill it and rethread it.


Or maybe, time to sell the bike "as is" and replace it with one better made. If it isn't worth $50 to fix...could just be better to write it off.
HS Bike is not worth the money. This is one of those projects where I just want to do it on my own. I picked the bike up for a song and am being stubborn about spending as little money as possible on it.


Quote:
Originally Posted by CaptNemoO2 View Post
You can try E-Z loks if you have enough material. They install similar to a helicoil, but don't require special taps and insertion tool. Drill out the hole, tap for external thread, screw insert in with a regular screwdriver. Mcmaster.com has them, but I can't provide a link to the page from my phone because their site is not mobile friendly.

Edit: here's a link! McMaster-Carr

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Great product. In this case it will not work b/c the ez loks would need a hole that would affect the cylinder sleeve.

I ended up asking a friend and he had the helicoil tool I needed.I ended up using two helicoils and it works great. Cost will be replacing the two inserts I used. Worst case is $11.41 on Amazon.

He also gave me some of the Aluminum brazing rods and I am going to practice on some scrap.
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Between us there was, as I have already said somewhere, the bond of the sea. Besides holding our hearts together through long periods of separation, it had the effect of making us tolerant of each other's yarns -- and even convictions. Heart of Darkness
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Old 07-10-2015, 00:16   #14
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Re: Aluminum brazing

Quote:
Originally Posted by ryon View Post
The problem with aluminum is that it forms an oxide coating which melts much higher than the base metal. There is a specialty rod that you can use to solder with a torch, but you must scrape thru the oxide layer while laying down a bead. You won't be able to do that inside a bolt hole, and I'm dubious if it would hold well even if you could.
Saw a video where it was done wanted to see if anyone had real life experience with it.
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Old 07-10-2015, 02:29   #15
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Re: Aluminum brazing

Aluminium can be brazed with oxy-acetylene using silicon alloy rods and the approriate flux, however aluminium (assuming it has been impeccably cleaned of oxide immediately prior to brazing) doesn't glow red and is hot short which means it will fall away without warning so you need some skill to braze it successfully. Additionally, motorbike castings tend to be alloys high in magnesium which can ignite in a worst case scenarios or otherwise gas out and form porosity if not done properly. And then to top it all off, it is actually quite difficult to fill a hole with weld or braze successfully if not experienced at it.

Me, I'd buy a cheapo helicoil kit on ebay and fix it that way. The repair will be strong enough to snap the bolt if overtightened (don't ask me how I know!).
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