From: Bianca Pratorius <biankita@comcast.net>
I have decided I really like my mid 80's 3Rensho. The shifting is good, a nice mix of campy, Suntour parts etc. I absolutely hate the fade paint on it because it is impossible to touch up and ends up looking very dirty all the time. I am sending it out to my local painter but before I settle on which decals to use ... original or repro, I need to thin those lugs. (my 3rensho is lacking in that department). I feel I'm up to the task but I don't want to reinvent the wheel. What's the best way to go about it. ie.. file, sandpaper grit, methodology....?
Garth Libre in Miami Fl USA
Garth,
One of my day jobs is teaching framebuilding classes (besides building and painting) so I've outlined for you a 4 step process to follow when you want to go to your workshop and play with your SanRensho (San being the Japanese word for 3). Keep in mind that I believe filing is more difficult to get right than brazing although our instinct might suggest otherwise. I'm also going to assume you haven't been frightened away from doing this after hearing the startled, fearful gasps of your CR "friends". I personally see no beauty in a lug that hasn't had some work to at least even the thickness all around and I have no affection for one that hasn't been thinned. Otherwise they look just like production frames with different decals. I'm also going to assume you have the basic equipment to do this work that includes wood blocks to hold the frame and file handles on the files. Right? If not you can order very nice wood blocks from Dave Bohm.
Step 1. Rough out the shape using as large a bastard cut file as you are comfortable with. Start on the sides and work toward the tips using short strokes until - as you move towards the center - you can lake longer ones a s you clear the interference from the side. When you can take longer stokes, be sure and rotate the file around the tube some with each motion so you don't create flat spots. Keep an eye on the edge to know the depth you are removing and don't let the file touch the tubes in order to guard the lug edge which can get destroyed if the file slips off the lug.
Step 2. Smooth out the roughness from hogging off the lug material with a smaller and/or smoother cut file. I typically use #1 Swiss pattern file to do this. The file motion will be clocklike from the lug crease to the edge being careful to advance each stroke just enough so that it is not cutting where the last stroke did but just next to it. You want to remove and not create flat spots. After you have reached the end of one area that doesn't require you to adjust the frame being held by your wood blocks, shift the file stroke direction and file back with this motion to where you started. Your goal is to have a consistent look throughout the area you just worked on. When necessary, move the frame position and then do the next section.
Step 3. Remove file marks with a smooth cut file. I typically use a round or half round #2 or 3 cut Swiss pattern file. This motion is the same as i n step 2. However because the file cut is smoother, you can't shape with these files, only remove file marks. Your goal again is getting a consistent look throughout the area being filed.
Step 4. Polish with 80 grit emery cloth without yucking up the lug edges.
I've measured the outside thickness of various builders lugs (on 1² tubes) with my calipers. A typical lug will start around 1.090². Depending on th e era I built a frame, my lugs ended up to be 1.060" in my thinner early year s to 1.070² when I liked more definition. Tom Sanders has a Chris Kvale from Minneapolis frame. He is an extremely fine builder that is known for havin g very thin lugs. They varied a bit from 1.060² to 1.070². I also repainted a frame from another very fine American builder Peter Mooney. He learned from Ron Cooper who was a better builder than were some places other Americans went to learn in England. He makes sure the lug surfaces are fla t and filed but not as thin nor as consistent in thickness. His lugs were around 1.080² give a take a few (maybe up to 10) thousandths depending on where you measured. The difference between 1.090² and 1.060² doesn¹t seem like much but to my eye it really is a lot. I can easily tell .010² difference when I¹m looking at them. I¹m pretty efficient with filing but it still takes me a number of hours to do each lug. I think the production guys like Curt Goodrich use the belt sanders for prethinning before brazing and Dynafiles afterwards a lot more than me.
That 4 step list is nowhere near exhaustive (it's just a starter guide) and if you decide to really give it a go, I'll send you my written out filing tips (including common rookie mistakes) from my framebuilding class in an attachment. Don't expect instant success. I'd estimate about 1 out of 10 do a really decent job filing lugs on their first frame. It takes a tremendous amount of hand control and it is easy to have the file slip just a bit and ruin the lug edge. If you are really good, the frame tubes themselves will show no marks of from either the file or emery cloth.
Good Luck and you're welcome,
Doug Fattic
Niles, Michigan USA