How hard is it to get a great polish on a lug as prep for chrome?
A determined amateur has that one huge advantage over the pro. No time constraints whatever if they so wish.
Kurt Sperry Bellingham WA USA
On 9/6/07, Doug Fattic <fatticbicycles@qtm.net> wrote:
>
> Garth,
>
> Let me continue our discussion of lug thinning and whether disturbing
> poorl
> y
> filed lugs is sacrilegious. My feeling is that crappy work doesn't
> deserve
> special protection irregardless of who made it unless it has significant
> historical value like Confente's first frame or something. There can be
a
> lot of lug shaping preparation before brazing in getting the curves just
> right and the point to be sharp and centered. We'll ignore that part of
> building because you are wanting to do after brazing thinning.
>
> I categorize lug filing after brazing into 4 levels of achievement - whic
h
> can also be used as guidelines to judge other work. The first and most
> basic level is to make the surface even. For example knocking off any
> casting ridges or welding seams or overflowing silver. The second is to
> continue filing until the entire surface has the same flatness. This can
> b
> e
> a challenge to keep the file exactly level (or at the same tilt) with the
> tube on every file Stroke. The third, if one has the ambition, is to
> keep
> filing until the entire socket has the same thickness throughout. And th
e
> fourth is to thin everything down to a consistent amount. At the NAHBS,
I
> went around and checked out everyone's lugs using that criteria to measur
e
> what I saw. I think every builder can decide at what filing station they
> want to get off at. Sometimes those steps can get mixed up, for example
a
> builder can really thin the lugs but they don't make the surface quite
> flat
> or even. Most students that put real effort into filing do get them
> thinner
> but the surface isn't quite even. It seems like the hands can't keep the
> file rotation (twist) consistent throughout the entire process. It is
> like
> looking at a car bumper and the light spot doesn't reflect evenly.
>
> I always use the best brand files like Nicholson or Simonds or, as a 2nd
> best choice, Grobet. Cheap ³import² files dull quickly and waste eff
ort.
> I
> would at least get bastard cut round and half round files in 4, 6 and 8
> inc
> h
> lengths and also a 10² round. In addition I would also get (if you don
¹t
> mind spending $30) a Grobet Swiss pattern 6² half round file (not the m
uch
> smaller Swiss pattern needle file) for finish filing. I would buy the
> Scroo-zon brand file handles that match the file sizes.
>
> Remember to start at the hardest place to file - right on the side of the
> lug with the flat side of as large a half round file that you can handle.
> You can only take very small file strokes before the end bumps into the
> hea
> d
> tube portion. The flat of the file should be parallel (or at a slight
> tilt
> )
> with the top tube. You can tell if it is at the right angle by watching
> th
> e
> results on the lug and adjust accordingly. You keep filing that small
> 1/8t
> h
> of a section until you have reached the desired lug thickness. The top
> and
> bottom points can be filed fairly quickly (maybe too quickly if you aren'
t
> careful). Just remember to move the file enough so as not to create flat
> spots during your stroke. We don't want to mimic a diamond's
> facets. Roun
> d
> files work well in downsizing the thickness of the crease between the
> frame
> tubes and head tube. When using a round file, you use a twisting or
> rotating motion and ³slide² the file over a greater area than the wid
th of
> the diameter of the file. If you don¹t you¹ve created a channel into
the
> lug. You want to slide the file far enough to reach the lug edge but not
> s
> o
> far as to fall off of it. That can be nasty because it is easy to start
> th
> e
> next file stroke on the tube and wipe out a small section of lug edge.
> Repeating again, the successful clocklike motion is to file a stroke, mov
e
> just beyond the filed area and stroke again, move incrementally and strok
e
> again (leaving no unfiled space in between strokes) until you need to mov
e
> the work. Always move the work rather than file in an awkward position.
> Success is achieved by coming right up to but not over the lug edge. It
> is
> that hand control that separates the good from the not good. Beginners
> hav
> e
> a hard time visualizing the desired result and piddle around not taking
> muc
> h
> off and then start getting ride of file marks too soon before the shaping
> process is complete.
>
> You should take encouragement from the fact that patience and taking your
> time trumps pure hand coordination. Many times I¹ve seen less talented
> students turn out nice work because they were determined to do so. It
> will
> take you longer but it is possible to get to a high standard with
> persistence. Don't be surprised that it can take a day of work to get t
o
> level 4 on one lug even if you are experienced. In addition it is tediou
s
> work that is difficult to stay at for too long of a time and not go nuts.
> You don't need an excuse to check the CR list but it does help to take
> breaks like that to keep your sanity.
>
> I'll send some before and after pictures so you can send some gushing
> prais
> e
> in return (well hopefully, I'm not big on receiving ridicule and scorn) a
s
> well as my class notes on filing tips. I'm teaching 3 framebuilding
> classe
> s
> before the new year. There is a special one next week for making
> transportation frames. I have one starting Oct. 22 and another Dec 2. I
f
> I
> remember right, there is still one space open in those 4 student classes.
>
> Doug Fattic Niles, Michigan USA