Thursday, November 8, 2012

On Notching, or the Joys of the Hole Saw

Tube Notching
This might surprise some of you, and it was certainly a surprise to me, but my favourite thing about the framebuilding experience so far has been learning about all the machines in Mike Flanigan's shop. I have never been into this sort of thing before, preferring to use the simplest tools possible for DIY stuff. The "shop atmosphere," with its various lathes and saws spinning menacingly, has always confused and intimidated me. I am not sure what changed now. Maybe the part of my brain that's responsible for this kind of stuff is just now maturing, but suddenly I am like a kid in a candy store. The machines are super-useful, physically easy to operate, and are proving to be excellent teaching tools when it comes to mechanical concepts I find difficult to grasp. For example: notching!

Tube Notching
Building a bicycle frame is mainly about joining together pieces of tubing, which involves a lot more work than merely brazing or welding the joints. For instance, before the tubes can be joined they need to fit together properly. 

Tubing, Lugs, Dropouts
Think about it: When we get a tube, its edge is cut straight across. But if we want that edge to join the rounded surface of another tube, we need to sort of scoop out the center of that opening, to scallop it. This is what's called notching - also known as mitering or coping. 

Tube Notching
And because the tubes join at an angle that is almost never 90°, the notch must be done asymmetrically, to fit the precise angle. In theory, I understood the concept, but in practice I had a hard time imagining concretely how this was to be done. How were builders able to determine the shape of the scalloped edge with such precision and draw it on the edge of the tube? Too embarrassed to ask this question, I tried to read up on it. Unfortunately, the more I read, the more confused I got.

Tube Notching
But the mystery was cleared up in a matter of seconds once it was time to notch my own tubes. Mike has what's called a horizontal milling machine, which can be fitted with all sorts of tooling - including hole saws of various diameters. 

Tube Notching
A hole saw is literally a round saw that makes holes in things. They are available in a variety of diameters. You choose the saw that matches the diameter of the dominant tube - the one to which you will be joining the tube you want notched.

Tube Notching
After attaching the correct saw and installing the to-be-notched tube in the clamp, you then set the angle of the joint, according to your bicycle frame's geometry. 

Tube Notching
And that's it. As you turn the crank, the hole saw makes its way through the edge of the tube and notches it. Basically the saw forces the shape of the dominant tube through at the correct angle. Watching this happening I experienced a sudden flash of understanding and it was immensely satisfying. 

Of course, by far not everyone who builds bicycle frames has this type of machine handy, and the low-tech notching method involves using lugs to make guide marks, then a hacksaw to make the cut. But even if I never have access to such machines again, operating them has done me more good than I can express. 

Tube Notching
I love the clean look of a notched frame; the way everything fits together perfectly and makes total visual sense before you get it all filthy with flux and leaky brazing marks. But also, watching the tubes fit and actually getting how and why they fit is wonderful. My head is bursting with the sudden understanding of concepts I've previously struggled with, and that is an exciting feeling to have. Whether it's framebuilding or any other subject-matter, it is never too late to learn new things.

32 comments:

  1. The frame pics look great! I've never seen the process shown this way, with the mitering done before the lugs are involved. I just learned something, too.

    Such things make you appreciate what used to be called "Industrial Arts' quite a bit more, eh?

    That mill has a wonderfully designed 1930s-40s logo plate. It wouldn't surprise me if it was of pre-WW II manufacture.
    A well made machine like that can be occasionally refurbished and used for over a century.


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    1. Putting the frame together this way was new for me too. Industrial Arts FTW!

      It is a shame I never learned any of this formally until now. My parents taught me a lot of DIY stuff with hand-held tools, but the only proper shop class I took was in grade 4, in Europe. In American junior high and high school, they steered the "college bound" students away from taking shop classes. By the time I left school, I already had it in my head that I wasn't good at that stuff.

      Interestingly, my experience with printmaking (etching on metal plates) came in handy. The amount and type of prep work involved (the endless sawing, filing, polishing) is similar.

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    2. "In American junior high and high school, they steered the "college bound" students away from taking shop classes. By the time I left school, I already had it in my head that I wasn't good at that stuff."

      Me, too. Imagine my surprise when I discovered that so many folks in my field of artisanry possess advanced degrees.
      The trick is ignore your qualms and jump in with a good teacher.
      Get your hands dirty. Get you some tool time, as Spin Dizzy might say.
      The printmaking (or sculpture) experience surely helps.

      It's fun -and kind of funny- to both use a Mill and read Mill. And Milton, for that matter.

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  2. When I took a class with Mike, conversation meandered to this blog at one point or another. I couldn't help but think at the time that it seemed inevitable that you'de end up at a class like this somewhere along the road. Glad to hear you ended up at Mikes classes, he's a great teacher, only getting better; take notes!

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    1. I have many notes and pictures; and will try to get a good chunk of it up this weekend.

      Just to clarify, I am not taking a class like the ones Mike offers; what we are doing is a little different in tempo and approach. But one thing I can say is that Mike's teaching style works really well on me. He is nice, but at the same time absolutely no-nonesense. He approaches everything with the assumption that I will understand it and be able to do it, and it becomes a self-fulfilling prophecy. Building a frame involves lots of little steps and some careful measuring, but mostly it involves work - manual labor. If you're willing to follow instructions and do the work, why wouldn't you be able to do it, is his attitude.

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  3. I always thought that lugged construction meant that the tubes could be cut square and the difference filled in prior to building a frame. It never occurred to me that the tubes had to intersect with such precision.

    A hacksaw to make the cut, but various files - if your instructor denies you the mill "for your own good" - to make the miters. Pretty sure this is what put all the black stuff up my nose and killed my hands.

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    1. It depends on the frame and lugs. Huge, socket type lugs that swallow the entire edge of a tube don't require notching. Skinny curvy lugs do; they don't cover much. Lightweight frames typically are notched and use skinny lugs.

      Oh I've used a hacksaw and many files, don't you worry. Over and over. Learning the machines has been super useful though.

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    2. So all that talk about mitering before didn't sink in...sigh. And "craftsmanship" and "quality" only refer to finish quality when visually inspecting a frame.

      Take the straw out of your sundae, make some peaks then lay it across: there's your miter.

      Those crude socket 'n' plug old Raleighs, as charming as they were, really aren't the same animal.

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  4. Good to hear you are enjoying the workshop environment. I like to be in them too, kinda like being in a wizards cave!

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  5. There is indeed something almost sublime about using a tool that is totally suited to its job.

    A recent experience of this has been using my daughter's new Mason & Pearson hairbrush (on her unruly hair, not my ever increasing lack thereof). How well it does the job it's made for is for me a thing of almost endless pleasure. b

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  6. Oh yeah, tool heaven..........I have sent you the link to the Tool Whore apron.

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  7. The lowtech method may or may not involve lugs. The cut can begin with a hacksaw or with tinsnips. The miter is completed with files. A skilled worker can use a file to create a joint that fits just as accurately as a joint made with a mill. For a few the miter is completed just as quickly with a file as with a mill. The saving in tooling costs is very significant for a small builder.

    Shaping with files used to be a very significant part of producing precision machinery and a universal feature of manual training. It is still the way to shape small parts like rear triangle bridges, seatstay tops, small tubes for racks. And artful lugs.

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  8. There is real genius in the design of milling machines.

    Fortunately I live in a small space. Otherwise I would have a mad collection of these machines. Really appreciate the photos of them in use.

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    1. It's not just about the space... Your floor has to withstand their weight! These are machines that you need a special truck to transport.

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    2. So, was the first milling machine made by a capable, motivated guy with a hacksaw and some files as the Machinists legend contends?

      Spindizzy

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  9. Just great! Thanks for that post. I'm enlightened.

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  10. Now, I marvel even more at the guy who made my wife's frame w/o any power tools, or lugs! It's like a piece of jewelry.

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  11. When my kids played hockey there was a local skate sharpening guru where everyone took their skates. It was a small shop in a small town. His main business was some sort of metal machinery thing making and designing I don't know what...But inside this little shop were all these cool tools which could be adjusted to the smallest of measurements to cut or grind or, again, I don't know what :) But my kids would stare and marvel at all these cool projects going on whenever we'd pick up the skates. Machinery is cool, and so is small scale one man operations who use it for crafting whatever our imaginations come up with.

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  12. Lucky you. You got to you use a milling machine on your mitres. During my framebuilding course, I had to create my own guides, then hacksaw and file it away until I had a flush mitre on my abutting tubes. The teacher wanted me to come to grips with the process and obtain a feel for the materials and tools through hand-work however if I were to manufacture frames commercially (which would be nice) then a milling tool would be indispensible.

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    1. I learned it both ways. I'll upload some hacksaw p0rn soon. The machinery is great, but it is not the real world unless I have access to a shop like Mike's. What I found most useful about the machines was the way they demonstrate special rotation and other mechanical scenarios of which I only had a murky understanding prior to this week.

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    2. spatial rotation, not special : )

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  13. Peppy (your miaws are music to my ears)November 9, 2012 at 7:41 PM

    The tears of those who had to mitre by hand are delicious.

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    1. not had to....choose to. we do things differently:)

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    2. Peppy has no sympathy for the toiling builder with hand tools. When I showed her my super-polished lugs, she knocked them over with her paw scornfully.

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  14. Ok, got that about making the first miter on one end of one tube. Can I trust you will now go on to show us how it is insured that the miter on the other end is in the same plane? And that the length after mitering both ends is correct for the frame design? Where do we send our tuition payments for this course?

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    1. I did it by laying a piece of half inch angle aluminum stock down the length of the tube with the 'open" part of the L laying around the curve and tracing a line down it.

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    2. VI Cyclist -Just want to make clear that my posts here are not meant to be instructional for those attempting to make a frame. There is too much detail missing; do not attempt!

      Kevin's way sounds pretty good. We used the machine shown here, with a backstop that allowed us to get precise alignment.

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  15. The Chimonas book recommends a program called tubemitre.exe which takes in the relevant parameters and prints out a paper cutting guide you wrap around the tube. Less accurate than the horizontal mill / hole saw probably, but targeted for good results on a low budget.

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  16. I used BikeCad to plot my frame, a really neat little program. It's a bit expensive but cool to play with even if you never make anything. It allows printing templates, which I then cut out, taped around the tube and traced with a marker. Then I cut them out with a dremel. I wasn't brave enough to make a fork though, I just put on one that I had.

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  17. This series is of all your posts the most interesting, because it enlightens us about much more than simply style, or even quality, but goes into the type of information that allows riders to appreciate the work of the people who create the bikes even more. After this, perhaps a look at the mass production of frames, to see how it compares, might be a worthwhile project.

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    1. I would love that actually. It's hard though, wihtout traveling to the Far East : )

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