torch tip for lugs- Mtbr.com
Results 1 to 13 of 13
  1. #1
    Squelch the weasel.
    Reputation: JaquesN's Avatar
    Join Date
    Sep 2009
    Posts
    154

    torch tip for lugs

    Hi All,

    After building a few fillet brazed frames and racks, all with the same Victor torch and size 0 tip, I am practicing my lugs. I am wondering if a larger tip would help me.

    Basically, my practice consists of
    • cutting an odd-shaped piece of 1.125x.058 tube,
    • sanding the inside a bit for a looser fit,
    • slipping it over a 1x.035 tube,
    • fluxing it, heating it
    • and trying to pull brass fully from one side to the other.


    It's been going OK but not great. To get the penetration I need, I am heating the whole joint more than I'd like - bright orange.

    I was thinking a larger tip would allow me to heat a broader area to a more uniform, but slightly lower, temperature.

    Thanks,
    J

  2. #2
    Bike Freak
    Reputation: jgerhardt's Avatar
    Join Date
    Aug 2009
    Posts
    323
    I use a #0 tip as well for fillets as well as lugs.
    In my (admittedly very limited) experience the #0 tip works well for both. From what I was told at UBI and have seen from experience you should never really need to get the lug to change color. When you heat up the lug, unlike with brass fillets, you really need to get the lug heated up pretty consistently so that there is no one focus of heat. To get that consistent heat I am constantly moving the torch all over the lug, never really keeping it that long in the same place.

    That said, I am sure some of the more experienced posters will have some better tips to getting a consitent heat.
    My bikes [Fe][C]ycles

  3. #3
    mtbr member
    Reputation: Clockwork Bikes's Avatar
    Join Date
    Jun 2006
    Posts
    707
    http://www.youtube.com/watch?v=EuazU..._order&list=UL
    I only use silver for lugs, but Nagasawa's flame for brass lug brazing is big and hot!
    NOTHING WORKS LIKE CLOCKWORK

    www.clockworkbikes.com

  4. #4
    Bike Freak
    Reputation: jgerhardt's Avatar
    Join Date
    Aug 2009
    Posts
    323
    Quote Originally Posted by Clockwork Bikes View Post
    http://www.youtube.com/watch?v=EuazU..._order&list=UL
    I only use silver for lugs, but Nagasawa's flame for brass lug brazing is big and hot!
    I didn't even notice that he said he was using brass, in that case I can only imagine the difficulty of getting the brass to flow all the way through.
    My bikes [Fe][C]ycles

  5. #5
    Squelch the weasel.
    Reputation: JaquesN's Avatar
    Join Date
    Sep 2009
    Posts
    154
    Yeah, brass is going to be a bit of a challenge, and I know that silver is what most are using these days. Thing is, I'm almost there with brass, and I like a challenge, and brass is cheaper.

  6. #6
    mtbr member
    Reputation:
    Join Date
    Mar 2007
    Posts
    725
    it is hard to convert exactly, but try a bigger tip and see how it goes. I would say I fillet braze with a similar sized tip but I lug braze with a bigger tip. At least a size or two bigger than you are using.

    For a heavy BB I might use the bigger tip, for a delicate lug, I might go down a size or two.

  7. #7
    mtbr member
    Reputation:
    Join Date
    Jan 2006
    Posts
    278
    think of it like this--
    the torch is like a can of spray paint. hold up real close and you get a lot of paint (heat) in one spot. back it up and you get more coverage, but the paint (heat) is spread out. So if you bump up your tip a size or 2 you can get more heat given for a larger area.

    When I do big joints with brass I like a big loud flame, get it hot, then get in and get out. Getting the tube inside and the lug the same temp at the same time to flow the brass was the hardest part to learn.

    Also since you are practicing dont worry about the temp/color. Get it to the temp you need it to flow at. For slip joint brazing brass you do need to get it pretty darn hot, and from my experience pretty close to orange. not a BRIGHT orange, but right around where the bright red starts to get orange.

    Plus you're doing it right, practicing. So you mess some stuff up who cares?!
    Also try slip joint brazing smaller diameter stuff to start with, because it is easy to get everything up to temp evenly and to get the brass to flow. Since you mentioned you've built racks try some 5/16" x .035 and 3/8" x .028, it is a nice gap for brass. Then you can applied this technique to heat everything evenly to large joints.

    keep in mind a well done brass lug wont look as pretty as silver.

  8. #8
    Squelch the weasel.
    Reputation: JaquesN's Avatar
    Join Date
    Sep 2009
    Posts
    154
    @ HomeGrownSS: "5/16" x .035 and 3/8" x .028, it is a nice gap for brass"

    That's a pretty tight gap. .00325 inches, assuming it's even all around. I've been going for a slightly looser fit on the assumption that the brass will flow better. Maybe it doesn't matter (?).

    Thanks all for the words of advice.

  9. #9
    mtbr member
    Reputation:
    Join Date
    Jan 2006
    Posts
    278
    Henry James's C-03 bronze rod wets out really nice. Maybe that is why it works out? Even though the numbers say its only a 3 thousandths gap it doesnt feel as tight as it reads when you actually slip them over, and once the inside and outside of the tubes are prepped it loosens up a tad more.

    here is a 3/8 x .028 and 5/16 i used for a rack bit. I used it to couple 2 ends of a tube, so i didnt have to flow the brass from one end to another, thats why i didnt put flux in the middle. but you get the point! Also when I do the prep i dont sand the exterior of the "lug", as to help facilitate the brass going to the clean inside of the joint, not the dirty outside.






  10. #10
    Squelch the weasel.
    Reputation: JaquesN's Avatar
    Join Date
    Sep 2009
    Posts
    154
    Looks real nice.

    Did you feed the brass from one point, or did you go around? I've been feeding mainly from one or two points on my "fake lug", trying to pull the brass through. My main worry is to have a perimeter of brass around the edge of the lug, and big bubbles without brass under the surface of the lug, between the lug and the tube. Ideally, brass should flow all the way down and form a mini-fillet on the inside of the tube.

    Was the external piece at a sort of medium orange when you were flowing the brass?

    In that Nagasawa video it looks like he's heating the crap out of everything! Then again, he knows what he's doing and I don't, so I tend to go by the book, or by conventional wisdom (as much as that can be determined).

  11. #11
    mtbr member
    Reputation:
    Join Date
    Mar 2007
    Posts
    725
    Nagasawa is doing it right BTW. He gets in there quick and flows the joint. Dwell time is important in post brazed strength.

    Just a tidbit. actually the optimum joint clearance distance is .0003 inches but that is for critical joinery (turbine blades and such) .003 thousands is what most framebuilders shoot for. There is a precipitous drop in shear strength around 15 thou so there is a large range to work with.

    Cleanliness, proper abrasive penetration and flux flow have as much to do with it as gap. i.e. your flux has to be able to get out of the way or the filler can't get there so the holes on the previous example were a good idea to facilitate this flow. Feed points or flux channels were more than just cosmetic as most people think they are.

  12. #12
    Squelch the weasel.
    Reputation: JaquesN's Avatar
    Join Date
    Sep 2009
    Posts
    154
    dbohemian: Didn't mean to imply Nagasawa wasn't doing it right! Point was, I won't able to replicate what he does with my level of experience.

    Good to get some information to work with on the joint clearance. Also, I did not know that about the vent holes in the lugs. I was thinking of adding some holes so I could be slightly more sure that the brass had flowed.

    Thanks for taking the time to impart your knowledge. Now it's back to the shop for more practice.

  13. #13
    mtbr member
    Reputation:
    Join Date
    Jan 2006
    Posts
    278
    Quote Originally Posted by JaquesN View Post
    Looks real nice.

    Did you feed the brass from one point, or did you go around? I've been feeding mainly from one or two points on my "fake lug", trying to pull the brass through. My main worry is to have a perimeter of brass around the edge of the lug, and big bubbles without brass under the surface of the lug, between the lug and the tube. Ideally, brass should flow all the way down and form a mini-fillet on the inside of the tube.

    Was the external piece at a sort of medium orange when you were flowing the brass?

    In that Nagasawa video it looks like he's heating the crap out of everything! Then again, he knows what he's doing and I don't, so I tend to go by the book, or by conventional wisdom (as much as that can be determined).
    for that little example i mostly fed from one spot. if i recall the whole section i was brazing was a bright red, some people might say borderline orange. its tough to tell what the color really is when wearing green goggles!!!

    when everything is up to temp and you add the filler, you can actually see through the metal to where the filler is going. so look for that, it happens very quickly when you first add the filler, a very subtle color change will occur where the brass is going. thats why i think practicing on the little joints is so helpful at first, its easy to see through.

    also right when everything is coming up to temp, i like to chuck a little extra heat further in on the joint, not so much at the shoreline, but enough at the shore to get the filler to adhere. that way the filler will zip deep into the joint instead of hanging around the shoreline, like dbohemian said when everything is at the right temp and you add the filler you will see flux bubbling out from the shores and holes as the filler material displaces the flux. if you can get everything up to temp at the same time and get the internal middle hot, it all flows very quickly. you will know when its right.

    ill see if i can get my wife to video me doing a slip joint in a few days if you want...im working on a teeny tiny bike for my daughter and will be brazing a section of crazy gas-welded/bilaminate fork.

Similar Threads

  1. customizable lugs
    By win brooks in forum Frame Building
    Replies: 3
    Last Post: 02-11-2009, 11:22 AM
  2. making my own lugs
    By mchimonas in forum Frame Building
    Replies: 3
    Last Post: 01-28-2009, 02:42 PM
  3. Lugs???
    By crux in forum Frame Building
    Replies: 11
    Last Post: 12-23-2008, 01:40 PM
  4. How do you chrome lugs?
    By aka brad in forum Singlespeed
    Replies: 2
    Last Post: 06-16-2007, 08:26 PM
  5. lugs...
    By ShockStar in forum Singlespeed
    Replies: 4
    Last Post: 10-01-2006, 05:02 PM

Members who have read this thread: 0

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  

THE SITE

ABOUT MTBR

VISIT US AT

© Copyright 2020 VerticalScope Inc. All rights reserved.