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Framebuilders Thinking about a custom frame? Lugged vs Fillet Brazed. Different Frame materials? Newvex or Pacenti Lugs? why get a custom Road, Mountain, or Track Frame? Got a question about framebuilding? Lets discuss framebuilding at it's finest.

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Old 07-19-11, 11:26 AM   #1
nardo1221
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filing lugs / shaving off parts

Hi all,

I've been using the bike forums for the answers to all my cycling questions but this is my first post. I searched and found a little on what I'm asking but not much, so here it goes...

I'm restoring a 1982 peugeot ph10. Several components were missing so I just recently purchased another peugeot for parts. Having the extra frame, I figured it would be a great opportunity to build up a clean fixed gear (though typically I'd prefer to restore than completely alter/potentially ruin a bicycle, I just can't get over the look of a super clean simple machine and I have no emotional connection to bicycle I just purchased .

Anyways, I'm in the process of removing/filing down the brake housing guides and extra nubs here and there but I was wondering about the lugs and fender bosses (not sure if that's the proper name, I'm talking about the threaded nubs near the front/rear dropouts where a fender/rack could be attached). For the lugs, I was wondering if I would damage/cause structural issues if I filed them down so they smoothly transitioned to the tubing - is this possible? I've seen frames where the lugs smoothly transition but am not sure if this is possible after the fact - especially on a 30 yr. old frame. I wouldn't file the entire lug down; the transition would start from the tubing into 30-40% the lug. If ill-advised, is it at least sound to bevel the sharp edges or round out the points? For the fender nubs, I just want to clean cut them off and was wondering if this could weaken the frame. Since I'm not concerned for the original finish (I'm repainting), I'd like bring the frame down to a most minimal form. Thoughts?

Thanks!
Bernardo
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Old 07-19-11, 11:53 AM   #2
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The dropout fender/rack threaded eyelets can be removed without affecting the structural integrity of the frame.

Lugs are often "thinned" by filing them down as the lug approaches the shoreline with the tube. This reduces the potential for stress risers at the tube to lug interface. It's not a good idea to file the edges of the lug so much that the lug "feathers" into the tube as that removes too much meat from the lug and could compromise strength.

See "So how does finishing the lugs add strength?" HERE.
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Old 07-19-11, 12:40 PM   #3
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I would leave it alone myself. Especially the chrome bits. I don't know your model of bike, but Peugeot usually spot welded the "braze ons" on.

I'm not a big fan of cleaning up lugs after the fact. Who knows what you might reveal? There are bound to be voids under those lugs; to completely fill them would have taken longer than it was worth for Peugeot. A pressed steel lug almost always has gaps where the metal was bent and welded. The welds were crappy enough that it would be very difficult to fill them without adding another step to the process. One look at these bikes will tell you they didn't take any unnecessary steps.

If you clean up any stray filler, make sure not to cut into the tubes.

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It's not a good idea to file the edges of the lug so much that the lug "feathers" into the tube as that removes too much meat from the lug and could compromise strength.
I can't see why this would be correct. Most builders don't do this because it's not what people want nowadays, but the UK builders from back in the day would feather their lugs, and there were plenty of U.S. builders that did it as well. I imagine feathering was mostly done after the fact because otherwise the lug would be hard to braze.

Last edited by unterhausen; 07-19-11 at 12:44 PM.
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Old 07-19-11, 03:01 PM   #4
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I can't see why this would be correct. Most builders don't do this because it's not what people want nowadays, but the UK builders from back in the day would feather their lugs, and there were plenty of U.S. builders that did it as well. I imagine feathering was mostly done after the fact because otherwise the lug would be hard to braze.
I remember reading an account of someone who was replacing a tube on a damaged frame with very thinned lugs, and when they hit the "lug" with the torch for a couple of minutes to loosen the end of the tube, most of it disappeared. You see, most of what the builder left behind was just silver brazing material where the lug had once been.
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Old 07-20-11, 12:06 AM   #5
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It has long been a tradition that the best of the American builders file lugs thinner. We don’t taper the thickness so the edges blend into the tubes but we do thin them so they end up to be about a mm thick. This comes from a couple of influences. The first is that the father of American builders - Albert Eisentraut - did this and got a lot of publicity in American bicycling magazines in the 70’s. It became the defacto standard of judging quality. The second reason was that when we got back from our apprenticeships in Europe, we needed to visually show why our frames were better than our European competition (we didn’t compete against other at that time). Our spiel was that we not only took time to make frames look better where you could see it but also with alignment and mitering where you couldn’t.

There is plenty of meat on your Peugot lugs to thin them some, just don’t get carried away. I would start by evening the thickness all the way around. Pressed lugs are always uneven in thickness. Then you could evaluate whether you wanted to thin them more.

Start on the sides of the lugs first where it is more awkward to get a decent length file stroke. Be careful not to let the file slip off the lug onto the tube. This rounds the edge (the mark of an amateur). The top and bottom lug tips should be done last because it is easy by comparison to motor those down. Use a bastard cut file to hog off the offending bulk. Next go to a fine cut file to remove the file marks left by the bastards and then polish with 80 grit emery cloth to give a final smooth finish.
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Old 07-20-11, 12:15 AM   #6
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when they hit the "lug" with the torch for a couple of minutes to loosen the end of the tube, most of it disappeared. You see, most of what the builder left behind was just silver brazing material where the lug had once been.
I'm going to question the accuracy of that persons account- thinning the lug away to a .005" thin strip of silver shaped like a lug is not likely. Hitting a very thinned lug with and overly intense flame during a repair and nuking it in a hurry sounds much more probable.

I'd leave any bike boom lug alone. I've seen plenty of bikes held together entirely by the spot weld on the bottom of the tube/ lug. I recently saw an older French bike that I could actually see day light through the gap (not crack) between the ST and BB socket- it just never had filler added there. Lug thinning presupposes tight miters and good filler flow/ internal fillet. If you don't now that is there (and it likely isn't) then leave the thick lug to act as the structural member it has been for the last few decades.
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Old 07-20-11, 08:28 AM   #7
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having fixed many bike-boom European bikes, I have to agree with Eric. You never know if you have a bike made by the new guy after lunch on Friday. It's typical to find major flaws in the construction in these bikes.

BTW, modifying a vintage bike is frowned upon by a lot of people. Not that it's anyone's business what you do with your bike, but it's a consideration.
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Old 07-20-11, 01:07 PM   #8
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Thanks everyone for the replies!

I will cut off the eyelets for the fenders since there are no concerns and will proceed with caution regarding the lugs. I think first I will strip the bicycle down to raw metal to better evaluate the lugs. Most are fairly clean and actually not too thick so considering the potential poor construction I will likely just clean them up a bit and perhaps thin them down slightly to even them out.

I know many folks strongly discourage altering vintage bicycles - like I said earlier myself, I'm usually one for original restoration... which is why I'm painstakingly cleaning and fixing the '82 ph10 (cleaning/sanding/polishing heavily abused metal is a real test of love and patience!) My dream fixed gear would be a custom design I'd have built for me but considering I don't have the cash to drop for such a frame now... I'd like to build up this peugeot as a temporary vision of what could be Plus I think a tasteful conversion wouldn't be too frowned upon... no wacky colors or ridiculously deep rims. I'm thinking the Brooks swallow, shellacked cloth tape and Ghisallo wooden rims will likely be the best this frame ever saw.
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