Repaired a brake caliper

[Pete.]

Had a guy pop round with this today. The stub carrying the bleed nipple snapped off - it had been cracked a while going by the dirt in the line of parting. I said I'd have a go at welding it back on for him but it might end up a soggy blob. I found it a bit tricky especially getting the casting up to temp without melting the small bit. there were a couple of bits that didn't fuse properly but I didn't want to risk going back over them and wrecking the threads.

 

[Richard.]

Had a guy pop round with this today. The stub carrying the bleed nipple snapped off - it had been cracked a while going by the dirt in the line of parting. I said I'd have a go at welding it back on for him but it might end up a soggy blob. I found it a bit tricky especially getting the casting up to temp without melting the small bit. there were a couple of bits that didn't fuse properly but I didn't want to risk going back over them and wrecking the threads.

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That looks a very decent job Pete.
I've repaired a couple of calipers in the past where unions and bolts have been over tightened causing the cast to crack. Not the easiest material to get going.
Your prep work looked very good and certainly a big part of your success.

 

[Pete.]

Cheers Richard. It did take a lot of cleaning with wire brush and brake cleaner - but you gotta do your best for these high-paying jobs!

 

[The_Yellow_Ardvark]

Nice Payment.

 

[Richard.]

Cheers Richard. It did take a lot of cleaning with wire brush and brake cleaner - but you gotta do your best for these high-paying jobs!

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Good profit in that one Pete

 

[Windy Miller]

Job well done there Pete!

 

[Pete.]

Yep I'll definitely be drinking the profits

 

[The_Yellow_Ardvark]

Yep I'll definitely be drinking the profits

It looks like it will have to be "QA"
I will be able to do that at no charge. No work.

 

[Pete.]

Just as an aside - and remember I'm still very much a novice at TIG welding - I just want to run my settings past you.

I set the AC balance to 65 to increase the cleaning a bit. I got the outside nice and clean but I was concerned about tdirt in the threads, even though I blasted them out well with brake cleaner and compressed air.
The frequency I set to 90 to warm the casting up, and tried to weld at 100 but the arc was flicking all over the place. It was better at 120 but still hopped onto the small bit and I was worried about melting it down so I took out the tungsten (2.6mm) and ground a taper with a wide point. After that I had a much better arc and did the welding at 120hz
Filler rod I used was 1050, it was the thinnest filler I had.

 

[awemawson]

Excellent looking work Pete, but personally I'd decline work on safety critical parts like that. Too easy to be blamed for a nasty crash, and I'm sure the part is a/ available and b/ not a Kings Ransom

 

[Pete.]

I hear you Andrew but it has no load on it, it's just a threaded boss for a needle valve. Plus it's not like he was a paying customer, just someone who couldn't get to work tomorrow without his bike. The beer probably cost more than a caliper.

 

[Richard.]

1050

Not the best choice of filler Pete. There is very little strength in that been a non alloy adding filler. It's more suited to 1*** and 3*** grades I believe. You would of been much better off with a silicon based filler despite its diameter.

 

[Pete.]

Thanks I'll remember that. TBH I got quite a bit of autogenous weld in my efforts to get heat into the casting.

 

[Robotstar5]

Cheers Richard. It did take a lot of cleaning with wire brush and brake cleaner - but you gotta do your best for these high-paying jobs!

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There's a woman at work known as Kronenbourg 1664, looks 16 from the back and 64 from the front

 

[Chris Stevens]

Had a guy pop round with this today. The stub carrying the bleed nipple snapped off - it had been cracked a while going by the dirt in the line of parting. I said I'd have a go at welding it back on for him but it might end up a soggy blob. I found it a bit tricky especially getting the casting up to temp without melting the small bit. there were a couple of bits that didn't fuse properly but I didn't want to risk going back over them and wrecking the threads.

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Easiest way to do that would have been vee out, clean out the thread with a tap, screw in the bleed nipple, and weld with 1.6 tungsten and 1.6mm 5356 rod. Parts like calipers always have a fair amount of mag in them, so its best to use rod as close to base material as possible. When cooled unscrew bleed nipple, run tap down thread again and job done. 1050 will be ok, but wont weld as nice as 5356, which I tend to use for most castings, and welding things like broken fins on heads and cylinder barrels. Silicone rod makes welding easier, but seems to crack much easier than mag type rods if casting is taking any sort of major force.

 

[Pete.]

I would have used the nipple to anchor the part Chris but the threads didn't extend past the broken part. I considered tapping the bleed hole and clamping it with a screw but I didn't want to risk messing the seat up though I could have drilled it slightly bigger. In the end the little jig held it very firmly.

 

[doubleboost]

Just as an aside - and remember I'm still very much a novice at TIG welding - I just want to run my settings past you.

I set the AC balance to 65 to increase the cleaning a bit. I got the outside nice and clean but I was concerned about tdirt in the threads, even though I blasted them out well with brake cleaner and compressed air.
The frequency I set to 90 to warm the casting up, and tried to weld at 100 but the arc was flicking all over the place. It was better at 120 but still hopped onto the small bit and I was worried about melting it down so I took out the tungsten (2.6mm) and ground a taper with a wide point. After that I had a much better arc and did the welding at 120hz
Filler rod I used was 1050, it was the thinnest filler I had.

Some good info there the 65 balance surprised me

 

[Chris Stevens]

I would have used the nipple to anchor the part Chris but the threads didn't extend past the broken part. I considered tapping the bleed hole and clamping it with a screw but I didn't want to risk messing the seat up though I could have drilled it slightly bigger. In the end the little jig held it very firmly.

Thats fine, but the main purpose of leaving the nipple screwed in would have been to dissipate heat, which would have meant a lot less chance of broken part blobbing. I do most welding now with my old Hitachi which is 60hz fixed frequency, if I had been repairing that caliper would probably have used it rather than my Kemppi at higher frequency. Small fiddly jobs like those are very good practice, and another is welding up broken cylinder fins, and getting an old cylinder and breaking off some fins and building up is a very good idea for beginners.

 

[Richard.]

Some good info there the 65 balance surprised me

It's about where I would of been John.60- 65% DCEN.

 

[Richard.]

Easiest way to do that would have been vee out, clean out the thread with a tap, screw in the bleed nipple, and weld with 1.6 tungsten and 1.6mm 5356 rod. Parts like calipers always have a fair amount of mag in them, so its best to use rod as close to base material as possible. When cooled unscrew bleed nipple, run tap down thread again and job done. 1050 will be ok, but wont weld as nice as 5356, which I tend to use for most castings, and welding things like broken fins on heads and cylinder barrels. Silicone rod makes welding easier, but seems to crack much easier than mag type rods if casting is taking any sort of major force.

If the calipers are mag cast then 5356 is the better filler to use From a composition POV
Si castings are better welded with 4*** filler materials. We've had this debate and yes 5*** series is a stronger all weld metal but it's not a superior joint if applied to an Alsi parent material.