S-bend seat stays

This was my first attempt at S-bends seatstays. I have built two frames with single-bend stays but those were a couple years ago and I did the single bend on my 7″ radius oak fork blade bender.  After hummin and hawing for awhile and attempting to make my own somewhat clunky 8″ radius bender out of MDF,  I decided to fork over the Franklin’s and get a properly made tool that will last for a long time and make life easier.  There are many bender options – from expensive used DiAcro’s that need customization, to new benders from ProTools and the like – but most of them need some customization to get the job done right (to fully encapsulate and support the tube so it doesn’t fold or flatten).  After looking at simplicity, cost, amount of work needed to do what I want, the Anvil was the obvious choice for me.  So for many frames to come I’ll be using my new Mr. Bender Rodriguez.  I got the 3/4″x 9.375″ mandrel for doing anything from 5/8″ stays to fork blades (yet to attempt that).  With it I can get away from mostly doing my time-intensive segmented wishbone stays to quickly bending single or S-bends in two tubing diameters (5/8″, 3/4″).  After practicing on some 4130 x 0.035″ and 0.028″ tubes, i went for it with some Nova single taper stays.  There was a little bit of flattening on the bend (5/8″ tube, 3/4″ mandrel) but almost nothing to write about.  After getting the initial bend, you flip the tube for the 2nd bend and use the phase keeper arm to make sure the bend is in the same plane as the 1st.  Then when it seemed like it’d work (comparing it to the life-sized drawing), I measured down from the tire mark on the stay/apex of the 1st curve (widest part of tire), and marked where the top of the slot needed to end up.  Then, i cut and slotted the stay for the dropout in the mill.

For now my ‘custom’ seatstay mitering fixture will work.  It’s not super pretty but i also didn’t have to file to fit at all after getting the right miter length.  The aluminum extrusion doesn’t clamp that well in the mill vise, but it’s mostly because i’m clamping so little of it due to the angle of the miter.  It all stays put after some serious force but I’m thinking that I need to fabricate an updated mount. But for now this will be my only non-Anvil fixture 🙂

Sputnik chainstay mitering fixture – SOLD


I bought this chainstay mitering fixture in 2011 for approx. $800 total with:

  • 3 sets of tubing blocks size = 2 of the 30×16 (one square and one with rounded corners) and one 26×18. ($200). The newer rounded corner 30/16 fit better than the squared edge blocks for MTB s-bend stays like True Temper (HSBENDCS1) and Dedacciai. The 26×18 fits the single bend True Temper chainstays (HOX4CS). (Was $100 extra for each tube block set.)
  • Hooded/Wright/Breezer dropout blocks, and tab-style dropout blocks. (was $100 additional for the 2nd style of dropout blocks.)
  • Custom tapped angle plate for use on a vertical milling machine. (was an extra $55 for this.)

This is the older version of this fixture, the new version is seen here. It’s in excellent shape. I used it to miter 16 sets of chainstays. The only modification is that I drilled and tapped M5 holes for 170mm axle spacing.

I would like to sell everything for $550 plus shipping. Thanks for looking.

MTMF on the horizontal

The Anvil main (all, actually) tube mitering fixture barely fits on my horizontal mill.  Mostly the 5×20″ table is pretty tiny for an 8″ rotary table (rotab) which is what the MTMF requires.  I have the rotab attached in the center t-slot but really i should have fabricated an extension plate so I’d be able to use the full Y-axis.  But because the knee/Z-axis is somewhat limited (15″) I could barely center the fixture with the spindle as it was.  To help this effort, Anvil fabricated me a special adapter plate for my rotary table that is thinner (3/4″) than the stock adapter plate (~1″).  Even this little bit of difference helped.  The adapter plate also came with slots instead of single holes to attach it to the rotary table so you can tram the plate’s rail to the spindle axis like seen in the photos.  The reason? Anvil makes their adapter plates for Phase 2 rotary tables and I have a Yuasa type that has the t-slots about 19 degrees offset/different than the Phase 2 table.  So when I had the stock adapter plate the rotary table read 119 degrees when it was perpendicular to the spindle instead of 90 degrees.  With the new plate I was able to set it right at zero (or 90) with the rail perpendicular to the spindle.  Makes it mush simpler to set the miter angles this way! It sounds like Anvil now offers this type of plate as an option for the MTMF because not everyone will have the same type of rotab.

Then, i found a nice slotting saw arbor in the box of goodies that came with the mill. It was made for the Brown & Sharpe #9 spindle so I just was able to load it right to the existing drawbar.  Super easy set up and the MTMF keeps the chainstay or seatstay in phase without any futzing.  Just load it, lock it down and slot.  Seriously, it’s easier and more accurate than the hacksaw method I was using previously.  I love how the horizontal serves it up on a plate right in front of your face whereas with a vertical mill you’re (or at least I was) ducking and tilting your head to try and see under the mill’s head to align the tube and see what’s going on.  At least for me, I prefer horizontals now for mitering that I have one, even a tiny one.

Process pics – seat tube collar for 31.6 dropper post

Just getting back to blogging about fabricating some stuff but been busy with other things lately.  I’m done with Scott’s fatbike fork with an good amount of bling (brazons) for fatty loaded touring goodness and the use of a Dyno hub with internally routed wiring.  I’ll post something on that fork soon once it gets painted and i can take some glamor shots.

I’ve started on Russell’s slack-ass all-mountain 29er.  In usual fashion, I run before I can walk so stuff takes me three times as long as it should.  Russell’s build has a 34.9 bent seat tube (True Temper 1/7/1 Supertherm) with a collar so he can use a new internal cable-routed 31.6 dropper post (no doubt a blog post on that cable routing later on…), an arched and ovalized top tube, and arched seat stays attaching to Paragon’s Rocker dropouts.  The geometry is similar to the Kona Honzo where it’ll have a 68 degree head tube angle and a 120mm X-Fusion fork.  Chainstays will be at most 416mm effective length (16.4″) with the Rockers all the way forward and he’ll be using an XX1 crankset with a 32t ring and a 10spd cassette in the back. It’s going to be tight with clearances…!

Here’s some photos of the collar making sans lathe.  Kinda hard to get faced/square collars without a lathe and the horizontal mill almost cut it but ended up failing.  So I just laid a fusion pass on a 65mm section of 1.375 x 0.65″ tubing without a ‘step’ to hold it in place. Worked fine but I’d rather have a step!

this looked so promising…

No, not the approved methodology. Can’t get the right angle with this vise for the cutter, and definitely not rigid enough and the mill doesn’t spin fast enough. FAIL!

slotting the collar

take 2 with a new collar but not trying the insert this time.

facing  the collar

The cold saw got it very close to being square, but just took a few thousands off to be sure. No lathe, this is as good as I can get it.

flat plate alignment

This is why i love my flat plate. So many uses for lining stuff up, fixturing with magnets, tacking while on the plate, etc etc.  Just wish it was supersized!

fitted collar

Pretty close, not a perfect fit though. I then ran a small fusion tack on top, then flipped in place and tacked and then did the other sides before fusion welding it all up.

fusing the collar



mitered in fixture.

I use that tube block near the BB the whole way to make sure it’s in phase from bender to the BB miter using the vise on the vertical mill. Also helps draw the tube centerline after bending for water bottle boss placement.

I am not a machinist

But I am giving it a try.

I’ve watched many of the Tubalcain’s YouTube videos and they do in fact rock, but you also need the right tools and hands on training and experience to get even the simplest job done on the mill or lathe. I’m sure I’ll get there with more trial and error but the danger factor is a bit greater in machining than with hacksaw and file! And when I spend 3 hours to fabricate this little plate for my seatstay fixture…well, I start to wonder why I try. Granted, the stupid 1/4″ end mill kept coming loose from the drill chuck (i don’t have an endmill holder for that size end mill yet) so it took me way longer than it should have, but still. The taking of multiple passes to cut through the 3/8″ aluminum (don’t have a bandsaw or high RPM cold saw to make the rough cut), and the resultant swarf (chips) overwhelmed me a bit. I kept wondering why i wasn’t just saving up for a REAL seatstay fixture from Anvil or Sputnik. But then i thought, what’s the difference between that and

saying “why don’t I just save up and buy a (enter your favorite framebuilder’s name here) frame”…WHY? Because it’s strangely fun and satisfying to make shit yourself, even if it does suck. The slots are too wide, the edge isn’t square on one side (tried to get creative and round the corners…), but it’s mine, all mine.
I am not sure I will continue trying to make my own tools since it takes so much time away from frame building, but I do see the reason the elders of the trade say it’s a great step ladder. I also see the need to build something when nothing else exists, like my upcoming wishbone seatstay fixture. This was just practice.

PS- the Grizzly drill chuck on this milling machine really sucks. It’ll soon be a ineffective paper weight.

Fixturedom – Anvil’s MTMF

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I got a new fixture. I feel guilty just saying that. After all, it’s cooler not to have fixtures and use files, or make your own.  I know, but I gave in to the inner tool whore. I’m trying to streamline and quicken my process so I can actually make bikes for people one day and not lose much money doing it.  So anyways, yep, I got a new fixture.

I got an Anvil main tube mitering fixture (which should really be called an All-tube mitering fixture).  It will help solve my keeping-tubes-in-phase issues (keeping tubes perfectly in phase while mitering so that little to no filing needs to happen after the coping on the mill). This will actually save me money over time by reducing the # of tube-rejects I create.  On each frame, i go through one or two tubes MORE than I should because I cut them too short, file them too short after cutting them too long, and some variations on that theme.

The fixture is awesome, it’s huge, and it’s heavy. It barely fits on my mill (that will be remedied in the coming months I hope!).  I had to raise the mill’s head to the very top of the round column so that it would fit.  The clamping v-block mechanism is sweet — no dents on 0.035″ tubing and I cranked it all the way down just to test. It can fit almost any type of tube other than round – i.e, ovalized, tapered, or both like with unicrown blades and chainstays. And it fits tubes down to around 14mm diameter. Good purchase me thinks.

The phase indexing mech is what I’m mostly psyched about.  Seeing the miter fit on the dummy tube and then marking the cut on the mill will be damn cool. I’ll likely rant more about this fixture later when I have more than an hour’s time on it. Here are some pics of the new toy over the weekend.

My own (if ugly) seatstay mitering fixture

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I usually make wishbone stays but I wanted to make this current cross frame more ‘classic’ looking and a little lighter, so I went with fastbacks.  I’ve been filing my fastback seat stays as a way to “earn my chops.”  (If you’re not a new framebuilder you don’t know this…but the old/er guys mostly recommend (want) you to learn the hard way, like they did.  Kinda the “walked uphill to school in the rain – both ways” type of thing. I understand it,  I respect it…and even get it.  Even though I’m the first to admit I have acquired more tools and fixtures than some would have just starting out,  I think it’s helped me progress faster than I would have otherwise with framebuilding and welding. Not in other ways of course (like making my own tools and understanding the intricacies of that craft) but I have been able to focus on building bikes which is what I want to do after all.  Had I started by building my own tools, I’d likely have built only a few frames if that.)

The irony is now that I’m kinda know what I’m doing, I have a much better idea of what I actually need to build a better bike through a more efficient and accurate process, as well as what I need and want in my mitering fixtures. Had I started out from scratch, I would have had NO clue on what I would want in a fixture. I still have very little experience using machinery to actually MILL, but I at least understand more how it’s done and can do more basic processes.  Yes, a community college course in machining would be a good idea, but really…who has the time? I live at least and hour or more from the nearest community college and have no one to ask that does this for a living nearby. So, I do what I’ve always done, trial and error.

I’ve seen lots of builders use 80/20 aluminum extrusion for anything from frame fixtures to chainstay fixtures.  It looks pretty easy to work with since there are many parts and pieces available. I figured that’s what I’d try using for my first seatstay fixture.  I got the materials from McMaster Carr, and their website is just awesome. It does take some getting used to, but the amount of info and product on there is endless.  They even had the CAD drawings with specs on each item. The t-slotted framing and hardware is located together so you can figure out what goes with what and order it up together.  For starters, I just got a 1.5″ solid extrusion that’s 2ft long and some fasteners.  I had the 1/4″ piece of steel from another crappy “fixture” I used long ago to make unicrown forks but it needed some work. I cleaned up the middle slots with a 1/4″ endmill so I could slide the tube blocks side-to-side, and also get a 4mm allen key in there to tighten the blocks up from underneath.  It’s not an extremely rigid fixture, but it actually works just fine (see pictures)!

The key with this fixture will be to create a top plate to hold down the tube blocks while mitering (like with the Sputnik stay fixtures) to improve rigidity.  Keeping the shortest amount of the stay sticking out of the front of the tube blocks really helps with rigidity.  I was getting some catching/snagging/popping of the hole saw on the tubes because of the long arbor flexing as well as the stays flexing.

I used just the single extrusion because of the tube blocks lying flat on the plate idea you see here.  Most seem to build it on the wider double extrusion (i.e., Meade’s seatstay fixture) and make a better platform for the tube block.  I may go there some day as well as make a better axle holder. My axle is totally clunky but is mostly just for the spacing since the tube blocks hold the spacing and tubes where they need to be.  The axle is my Bringheli dummy axle that came with my alignment system, inside a 1 x 0.049″ split tube, inside the 1″ single clamping tube holder from McMaster.  The total cost of new stuff was under $60. So, if you were to do this the right way and put more time into it (this took me a couple of hours) it’s possible to make a much stiffer, prettier, better fixture for around $100 total (and that’s without any fabrication of parts myself, which could lower costs even more).  It’s pretty damned fun to piece this puzzle together and get a usable result.

Improvements: I want to use a Anvil indexed dummy axle so I will have to fabricate a different rear axle holder. They only sell the tube holders in 1″ diameter, so I’ll have to create a baseplate for the axle and use a toggle clamp for easy in/out.  The modified (mutilated) Paragon tube blocks work but I’ll likely flip them and drill/tap holes in the bottom to attach to the steel plate to make the fixture quicker and easier to load up and get centered.