Stainless brazing help

I am making my first stainless bike. The build is XCR tubing, and I have a paragon machine works T47 Stainless Steel threaded bottom bracket. I’ve used SIF silver solder 39 brazing rods and have used LGT Sliver flux paste. I’m using Propylene.

I tried to tack my frame last night. All the XCR tubes, including the thicker headtube joined together perfectly with a nice flow and heat drawing the filler into the joints. I was really pleased.

When it came to trying to attach the seat tube and down tube to the BB, I just couldn’t get the braze to bond to the BB shell. I thought it was lack of heat in the bb shell due to it’s thickness so made sure I put extra time into getting warm. It just wouldn’t bond. I took the shell out, cleaned it up and tried again. No luck.

Any thoughts where I’m going wrong? My initial thoughts were I had the incorrect material for the BB shell, but I have reviewed what i bought and have a stainless steel T47 BB from paragon. Now I’ve confirmed this I’m stumped!

Any suggestions? is the bb the ‘wrong’ type of stainless steel? have I missed something?

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I would also think you’ve gotten a titanium BB shell or something like that… Can you check the OD? Titanium seems to be 52mm and stainless 50.8mm.

interesting - thankyou. I’ll measure tonight. Would Stainless steel be magnetic and titanium non magnetic?

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The stainless steel we use is 17/4, which is magnetic and can be silver-brazed. If the BB shell you have is not magnetic, then it is titanium. If so, we apologize, and we will get you the correct one.

I’m not familiar with SIF silver solder 39 brazing rods, but all silver I am aware of works well with 17/4. It is extremely important that all material is clean. Good practice is to mechanically clean with an abrasive, such as emery cloth, and then a hot water and detergent wash.

Regarding this, we have titanium shells 50.8 and 52.4 mm; stainless steel is only available 50.8 mm. Magnetic/non-magnetic is a much simpler diagnostic tool.

My fridge magnet doesn’t ‘stick’ to the shell but it does stick to my fridge! Looks like it may be titanium???

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Hello Ivan, Please send me an email at . I’ll need the name that you used to place the order to find your order information. - Coco

If your BB is titanium and you’re not going to build with it, I’d be happy to buy it off of you (assuming it’s 68mm).

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assuming it’s titanium your welcome to it. I’m in the uk, so might not be worth the postage?

Ah shoot, cross-Atlantic shipping makes less sense. I’d say it would make a good paperweight but it’s probably too light!