Greg (and others)
If Doug will have you it would be well worth the trip to see his shop.
I built my share of frames in the early 80s and I can tell you that without a doubt Doug builds some of the most beautiful frames you have
ever seen. (Doug, I remember you from RAGBRAI. Sorry for the shameless
plug)
Steve Leitgen La Crosse, WI
On Dec 3, 2005, at 5:31 PM, Doug Fattic wrote:
> Greg Parker from Ann Arbor, Michigan asked:
>
> What percent silver was your wire? What brand and part number? How did
> you
> get your miters good enough to use silver? Without any lugs, the gaps
> would
> be even more critical. How did you build a fillet with
> high-silver-content
> wire? That sounds a bit fishy to me, unless the silver content was
> actually
> quite low.... Professional framebuilders, what say you?
>
> That would be me, Greg, and I\u2019ve been following these various topics
> regarding KOF fillet brazing frames with some interest and at times
> amusement. Let me first shed some light on silver brazing a fillet.
> It is
> possible to do this but it\u2019s not likely when using the latest tubing
> like
> Reynolds 853. This is because they have designed it to be tig welded
> and
> have combined the alloy\u2019s so that when it is heated over 1600
degrees,
> it
> gets stronger. Silvers\u2019 melting point is 1200\u02da or so, so it\u2019s
greatly
> adde
> d
> cost wouldn\u2019t take advantage of the tubes properties. The most
common
> silver used by framebuilders with lugs is 56% cadmium free (I use 45%
> with
> cadmium because it flows better but I will die younger for it). The
> temperature range with either of them between the liquid and solid
> state is
> very narrow \u2013 meaning that it doesn\u2019t have good \u201cbuild up\u201d
qualities -
> as
> soon as it gets liquid to melt, it will also start to run away.
> Keeping th
> e
> filler in between the liquid and solid state is how we control the
> build up
> of the filler so enough of it stays in the right place to create the
> shape
> we want. Now 35% silver has a broader temperature range between the
> liquidus and solidus states (I don\u2019t know why the brazing industry
> makes
> those words sound Latin instead of using plain English. Perhaps it\u2019s
> to
> market it\u2019s users as seeming to be intelligent.) so it will build up
> more
> easily. This silver can be used to fillet braze more easily than the
> typical ones we use. Of course it\u2019s broader range also means it
gets
> to a
> higher temperature at the top end. The most likely candidates for
> fillet
> silver brazing was older thinner walled tubing like Columbus KL which
> wasn\u2019
> t
> very commonly used. It\u2019s thicker walled cousins SL and SP could
> withstand
> the higher temperatures of brass better so the trouble and expense of
> using
> silver wasn\u2019t as necessary.
>
> Fillet brazing is more common today than before among some KoFs
> because of
> the challenges presented by using a threadless stem instead of a quill
> stem
> .
> In my opinion, it looks better not to have lots of head tube above the
> top
> tube (which a threadless design requires). By putting a bit of slop
> (not
> compact style steep slop) to the top tube, it can place the top tube
> closer
> to the top of the head tube (keeping the length head tube the same) so
> it
> doesn\u2019t have that extended head tube look which I personally don\u2019t
> prefer.
> Remember this extra height is necessary for those of us that have more
> weight and less flexibility than we had in our youth and, as a result,
> need
> a higher handlebar height than the racing crowd this stuff was
> designed for
> .
> Keep in mind that another controlling variable is the need to keep the
> top
> of the top tube low enough so we can stand over it. There aren\u2019t
many
> lugs
> available to accommodate this newer design variation. Also thrown
> into thi
> s
> mix is carbon forks which usually have 1.125\u201d steerers that require
a
> bigge
> r
> diameter head tube. These factors eliminate use of the older lugs.
> So an
> easy and common solution is the fillet braze. I also like to file my
> fillets. I can get close to an end look by brazing alone but think
> perfection can only be reached by filing. I also think it is easier
to
> fillet braze than use lugs \u2013 but of course I insist on filing even
> investment cast lugs a lot to get the effect I find most attractive.
>
> Greg, I\u2019m not very far away from you in the southwestern part of
> Michigan.
> Come and see me if you want to learn how extremely accurate miters
> can be
> made. I\u2019ve got a super nice mitering device sitting on my
Bridgeport
> mill.
> I\u2019ve also got a few nice old frame around that are mine or customers
> frames
> in the painting process. I like visitors.
>
> Doug Fattic
> Niles, Michigan