More Experienced Brazing Techniques

[meech151]

I have heard of, although haven't witnessed, brazing techniques for pulling the frame one way or another in order to make it come out of the jig more aligned. I have been fillet-brazing for about 3 yrs. now and would like to learn a more advanced method. Would anyone like to shine some light on this subject?

[Dave Kirk]

I do a full tinning while the frame is in the jig and I let it cool there. When I remove it it's right on straight.

Then when laying the fillets I work each joint in quadrants. I do 1/4 going clockwise and then the next counter-clockwise and so on until the joint is done. This gives very good results in the end.

Dave

[Tom Kellogg]

A similar but slightly different approach here. We do our tacking in the jig and ONLY tack in the center of the joints. ie. top and bottom. This way, any temperature related movement is in a vertical plane. Once the tacks are cool, the frame comes out of the jig, into a Park stand for the first and second passes. We do those in a similar manner as Dave in that we take each joint in quadrants; right-top, left-top, right-bottom, left-bottom. Because you are not welding, any "pulling" is so minimal that cold setting, if you still need to do it, will be minimal. In fact, for us, needing to set the front triangle means that we made a mistake somewhere along the line.

[Andrew R Stewart]

I have been taught to use an equal amount of heat and time for each part/quadrent of the joint. (After the tacking along the centerlines). Assuming good fit up/mitering and equal energy going into all parts of a joint, the joint shouldn't move much. I believe that if you have more heat on one side of a joint the tubes will contract on cooling towards that side.

[meech151]

Thanks for all the input. Some of what you all said i have been doing however many times I get caught up in the brazing and forget to rotate one direction or the other.
I also put the frame back in the jig after finishing and reheat all the joints and this has helped quite a bit. Thanks again for all the info and I'd love to hear any more ideas someone may have.

[Dave Kirk]

Thanks for all the input. Some of what you all said i have been doing however many times I get caught up in the brazing and forget to rotate one direction or the other.
I also put the frame back in the jig after finishing and reheat all the joints and this has helped quite a bit. Thanks again for all the info and I'd love to hear any more ideas someone may have.

This is something I would stop doing with your next bike.

Dave

[crumpton]

i like what Dave and Tom have added here. they produce some of my fav filleted bikes. i also agree that we are not welding, there is no melting/shrinking of the base metal. the brass shouldn't be pulling the on the frame much however if your fit up is poor, it can move a frame a bunch. i think good miters are key to a nice straight fillet brazed bike. brass shrinking in a gap is not a good thing.

[Andrew R Stewart]

Nick- Then how do you explain the distortion left over after heating one side of a bar of steel? No brazing needed just the torch in one spot on one side. I might not know the underlying science but I do know what I've seen.

[Dave Anderson]

My method is similar to Tom's....except I tack, verify alignment, and then tin the seat tube to the BB shell, before returning the seat tube/BB assembly to the jig and fitting and tacking the other tubes. I then pull it out of the jig and check alignment, and then braze in a park stand in quadrants as well....I do 12 o'clock to 3, and then 6 to 9, then 3 to 6, and finally 9 to 12. The frames come out quite straight....

Dave

[meech151]

Hey D. Kirk, just curious as to why this is a bad idea? My frames normally come out of the jig within 3mm of alignment and then cold setting is not that difficult.
I remember when I first started frame building I put my Scott CR1 on the alignment table just to see if it was perfect and the seat tube was 4mm off center at the top.

[crumpton]

Nick- Then how do you explain the distortion left over after heating one side of a bar of steel? No brazing needed just the torch in one spot on one side. I might not know the underlying science but I do know what I've seen.

bar? as in solid? thats a lot of heat. i'm not sure there are many similarities in heating a bar to a point of movement and getting brass to flow around some thin walled tube. but hey, i'm no expert. plus in teh frame, we are heationg around the joint, not just one side.

besides, my point was about nice fit up and mitering.

[Dave Kirk]

Hey D. Kirk, just curious as to why this is a bad idea? My frames normally come out of the jig within 3mm of alignment and then cold setting is not that difficult.
I remember when I first started frame building I put my Scott CR1 on the alignment table just to see if it was perfect and the seat tube was 4mm off center at the top.

Good Morning,

Two quick things before I head out on the snow for the day. 3 mm is a big number to me and I would really want that to be 1 mm or less. And the idea of locking a bike that is not straight into the jig and heating it so that the jig can then bend it into shape while hot seems risky to me.

I would work on getting it to come out of the jig very straight and then develop a brazing pattern that will not change the alignment.

I hope that helps,

dave

[Scheisserad61]

Meech 151 says : "I remember when I first started frame building I put my Scott CR1 on the alignment table just to see if it was perfect and the seat tube was 4mm off center at the top"

How sure are you that your alignment table is accurate ?

Putting a frame back in the jig and unnescessarily re-heating it, only to have it STILL be out of alignment when it cools down, is caveman framebuilding, at best.

[meech151]

Its never too early for an insult. Keep'em coming. Maybe I'll make a Geico commercial.

thanks

still learning

[steve garro]

Its never too early for an insult. Keep'em coming. Maybe I'll make a Geico commercial.

thanks

still learning

He's not ripping on you - he's right. Heat cycles & the duration of them has allot to do with frame longevity. - Garro.

[bellman]

Its never too early for an insult. Keep'em coming. Maybe I'll make a Geico commercial.

thanks

still learning

Nobodys ripping on anybody.
Keep asking questions based on the responses, you're doing fine.
There is a lot of good info getting divulged here.
I can drive the octagonal peg thru the hexagonal hole too but wouldn't you rather know how to make a hexagonal peg?

[meech151]

No, I should've clarified. I totally agree with what was stated about heat contro. I am not biting the hand that feeds. I totally respect the above responses and that is why I asked the question
in the first place. My remarks were directed at the "caveman" remark above. Even the question from Scheisserad61 about the levelness of the alignment table is fair enough. I relish constructive criticism and
have learned many things from these frame forums and the builders on them but the one remark seemed a little egotistical. If I am wrong then I stand corrected. Thanks for the helpful responses and I am actually going
to try them on a frame this afternoon. Now I need to get back to my cave and try to level these rocks that my alignment table is on. Enjoy.

[Chauncey Matthews]

What, doesn't everybody club their frames into alignment? ;)

It's helpful to keep careful track of your brazing sequence and repeat it everytime. That way it's easy to see the results small changes in the sequence make.
Also, posting your basic sequence here might make it easier for the masters (Kirk, Anderson, and Garro) to give you more specific pointers.

[Scheisserad61]

Dear Meech,

Sorry about the "caveman" description. Where I come from (N.J.) insults are often used interchangeably with terms of endearment. Along with sarcasm and making fun of peoples families and ethnic/racial backgrounds, it is how we were taught to show affection and make good impressions when first meeting someone.

[meech151]

Oh man, New Jersey, I should've known. Insult and apology accepted. Stop by my cave sometime. Chao hombres.