lug inside diameter
 

How much space between the lug and tube? I am going to make some lugs and need an inside diameter. Thanks!

I remember reading the All-State 11 brazing rod brochure, Nickel Silver I think, which suggested "0.001 to 0.003 inches of clearance for maximum strength". Hehe I think 1 thou would be pushing it! Generally I think you are fine with 0.005". I think I also read about Freddy Parr's silver who could fill 10 thou?

So I think there is an amount of flexibility :) People that make lugs usually use tubing the next size up (+1/8") with a 0.058" wall, that gives 9 thou diameter clearance. Thin it a bit on the lathe and presto a good slip fit for brass or silver (I tried it for the latter).

when making lugs, people typically use .056 wall tubing, the next 1/8" OD up. I.e., lug for 1" would be 1 1/8" .056 wall. It's a tight sliding fit

What are people doing to clear the lug for tube penetration so it contacts the tube to be joined. Say you welded the external seam, and you had rough cut the internal, it ends up with a lot of grinding, I suppose one could use a cutter and plunge the internal diameter, sorta tight work though.

I'm wondering about that. I guess you can work your way from a vent hole with files and/or adjustable reamer...

I have been thinking about different ways of doing this. I thought about using a .058 DOM 1020 and flairing the mitred end where it joins another lug section so when I TIG the pieces of lug together they might not require too much grinding and have a smooth, larger radi transition on the inside. I also thought of the formed sheet approach with a simple broach to remove the long seam. perhaps some type of backup under the seam to control drop-through. making rolled sheet round can be a challenge.

I have thought about blacksmithing some pressed lugs. They were (are) made in halves and welded down the centerline.

I was actually thinking, insanely as usual, about starting a frame building deal that would be frames with all custom made lugs. eliminating the design constraints of lugs coming only in certain sizes. This isn't a new idea, so it can be done - In Italy at least. The main problem I saw was how to get even badly paid for building 2.5 bikes. First one tigs a small frame together, then one cuts it up, carves it into lugs, does finish work on the inside, and then starts building a lugged bike. All in order to avoid the pitfalls of a Tig bike, which at it's heart it still is... It's this lack of a cheery can-do attitude that is keeping me poor...

Yeah basically you make twice the bike (or 2.5 hehe) by making your own lugs.

I'd like to give it a try. Since I'm a beginner I figure it can only help to hone those brazing (I'd fillet-braze them) and filing skills :)

there are a lot of people doing bilaminate construction. Not too many people making lugs.

I missed the tweet!! What is bilaminate construction!!??!!

Oddly my post above reads "constraints" twice but when I go to edit it, it only appears once. Kinda eerie considering the two for one nature of the subject...

Peterpan1, are you being sarcastic or is this a serious question? My helper Herbie made a bilaminate bicycle to show at NAHBS (we were next to unterhausen). You can see that frame and the one he is doing now on Flickr under Helm Cycles. He had to answer the question how he made those lugs all day long.

I have no idea what "bilaminate construction" is but Herbie made a nice bike! holy cow..

I just want to build my wife a nice steel frame that fits her. She cooks me three hand-made meals nearly every day. There is no such thing as "too much work" when it comes to her bikes.

Bilaminate means that the joints are sleeved and then fillet brazed

Herbie's "seat lug":

http://farm3.static.flickr.com/2790/...632739d6fb.jpg

Okay I'll tell you but first you have to listen to a history lesson about bilaminate construction. Claude Butler was a famous brand in England from the thirties through the fifties. He pioneered (or at least championed) this process where decorative sleeves were cut out and placed onto the ends of tubes and then the whole mess was fillet brazed together. Claude himself wasn't a framebuilder but rather had 4 or 5 guys churning out a highly rated product. His business was probably similar to Serotta or Independent Fabrications. Some of the most famous British builders got their start at Claude Butler. You can read more about his history and his techniques on the Classic Rendezvous or classiclightweights.co.uk sites. If I understand it right, he rolled flat sheet into the sleeves that were cut out (or cut out a pattern on a flat sheet that was then rolled into sleeves). Part of his motive was that conventional blank lugs were difficult to get at times so he developed a technique that didn’t require him to be dependent on iffy supplies. He eventually sold his business in the mid fifties (fancy bicycles became less popular and rumor had it he had a drinking problem) and I heard he was a gas station attendant when I was apprenticing in England in 1975.

Unless you are Dave Bohm (who has the rollers to do this) in the States we do this with slip tubes. A tube with a wall thickness of .058" will slip nicely with just enough clearance for silver brazing over a tube with an OD 1/8" smaller. A wall of .058” is too thick so it needs to be turned down on a lathe to about half that thickness. This construction can be done 3 basic ways with variations. The first way the slip tubes are mitered and brass fillet brazed together to form a lug and then the frame is silver brazed together. The second way is the tubes can be cut out and brazed onto the ends of the tubes and both of them can be mitered together. Then they are fillet brazed into a frame. The third way is that the sleeves are cut out and mitered separately from the tubes. They are slide together and all the pieces are brazed together at one time.

You can see Herbie’s latest creation in Philadelphia at the show Steve Bilenky is putting on the end of October. He has been designing and cutting out the lug sleeves all summer. He just started to braze them up into a frame last week. He helps me teach my framebuilding classes. He is an illustration of how the best learn. I tried to find the right place(s) to learn from in Europe (when America was just starting to have framebuilders) and brought those techniques back with me. After adding my input, he is able to take that knowledge and add his own twists to it.

Doug Fattic
Niles, Michigan

Thanks for the history lesson Doug, fascinating stuff, and a very talented protege you have there. One thing I object to or find curious about the preference some have for lugs is that the symbolism is all wrong in the modern world. The imperial or royal symbols are largely disrespected today, and the alternative one finds in say biker culture (dice, skulls, etc...) hasn't any connection to bicycles either. I think his patterns have , a nice relaxed modern look to them.

From the structural perspective I had wondered whether this method was possible so it is good to know it has a long history. It lacks the interlock in the tubes that one gets with penetration in the intersected sleeve, not to mention the welds. Though for that to be a problem would presuppose that the stuff was in motion and had failed in the first place. In a sense it is like a fillet brazed frame with home made butts, as much as, sharing aspects of lugged construction.

Wow, that is interesting. I saw a 60's Claude Butler not too long ago, I wish I would have taken a closer look. Managing the heat properly looks like it would be quite difficult. I haven't fillet brazed anything since the early 70's so I would need to brush up quite a bit before trying this.

Files, just files, nothing wrong with a file and some care and skill
one only has a thin section, 1.20mm lug wall of approx .50mm left of the undersize hole to remove.
No need for a reamer either.

I have a somewhat related question; what do you use to make the more intricate cuts in lugs? Sure, you could use needle files for final finish work, but I would think that removing unneeded lug with a needle file would be a very time consuming process. Is there such a thing as a coping saw for metal?

Pete

Yes, its called a jeweler's saw. They are available from such places online as ottofrei, gesswein and contenti. Blades vary in thickness and number of teeth. They are easy to break if you tilt the saw slightly during your stroke. It is possible to break dozens on a lug until you get the hang of it.

I don't saw right on my cut line but rather close to it and then finish with a regular or needle file. Often it is not possible to keep the blade at a 90º angle to the surface anyway (because other parts of the lug are in the way) so this off-the-line cut is necessary.

Thanks. I normally don't cut to the line (when doing miters) anyway, so it shouldn't be a problem. Is there a recommended TPI for cutting cast lugs?

Jeweler's saw blades designations run from 8/0 the finest to 14 to heaviest. What is right for the job depends on the thickness and hardness of the material, the intricacy of the pattern and the skill of the user. I would try starting out somewhere where the / numbers become single numbers. You are going to break a lot in the beginning so a few dozen in several sizes will help you find the right ones for you. I used the 4/0 size when cutting owner's initials out of lugs but that is probably too fine for beginners in most applications. I use heavier ones when hogging out blank areas. The general TPI sawing rule applies here too - 2 teeth should be on the work surface at all times. That is because if there is only one, the teeth will drop into the work and break off with motion.

I don't think I am clear on what you are saying. You are removing .5mm from the ID of a tube with a file or just some weld drop-through?