# 80/20 Frame Jig Build Thread



## seahuston (Jun 17, 2008)

Hi All,

I'm new to the frame building world but not new to bikes or machining. Really looking forward to getting into the craft and playing with geometry, materials, and techniques. 
Even though it may be a little backwards (since I still don't know my way around a torch!) I thought I'd start with building a frame jig. It's been a fun project and I thought I'd share the details so far.

Design is based off of the Arctos frame jig clones.
Tanner W.'s ever popular jig:
Bicycle Frame Building Jig
Pithy Bikes similar jig and great videos:
https://www.facebook.com/pithybikes
And 44 bikes frame jig:

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https://flic.kr/p/4935230598

I decided on a hybrid of all of these since I liked the fixed BB position of the 44 jig but the axle support of Tanner's jig. I went with the fixed BB position because I didn't feel that I would be able to machine the slot accurately enough on my mill since I don't have CNC or a rotary table. It just seems to make most sense to me to have your major datum fixed instead of simulated.

For extrusion I used Misumi 40 series stuff. 160-40 for the bottom rail and 80-40 for the vertical. I HIGHLY recommend Misumi for your extrusion, it's really high quality and much cheaper than 80/20 brand. They also custom cut for no extra change so you only pay for what you need. My only complaint is that this series is drilled for an m12 blind joint hole. That's a big bolt! 
Total spend on extrusion: $153

Small parts and hardware were all sourced from McMaster, I've made two orders so far and I hope not to have to make another. Was going to go with handles for every movement point but then I realized I could get a box of M8 screws for the price of one handle! 
Total hardware spend: ~$75

For the aluminum, our local material supplier has a great remnant area of 6061 for $2.50/lb. I found everything I needed an more here. 
Total material spend: $80

Here is the mocked up extrusion.


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## seahuston (Jun 17, 2008)

*Spine Joining*

I've already made good progress on this jig before posting to the forum so I'll try and provide quick updates.

To join the spine I first did a light skim cut on the end of the extrusion after aligning it to the mill table. The cut was already pretty square but because of the long arm being attached to it, I though it was very important to get it as good as possible.
Cutting the end:









Next I drilled and spot faced the 80-40 piece for the M12 bolts:









To clamp it together, I used the mill table as as datum while tightening. This setup worked okay but still required some tweaking.









Assembled:


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## todwil (Feb 1, 2007)

looks like a good start I did the same thing, did a little internet R&D (review and duplicate) and did an 80/20 jig I think total cost was $400 or so....The guys jig I copied PM'd me saying he went and looked to see if it was still in his shop I didn't think I copied it that close.


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## seahuston (Jun 17, 2008)

*Dummy Axle Holder*

My last update might be stuck in new poster purgatory but here is the next round. Again, I'm nearly done with the jig so this is more of a documentation for others in the future.

Here is the full dummy axle assembly complete (without axle)









I made the horizontal support and used two screws plus dowel pins to secure it to the vertical sliders. The pins allowed for a very clean and snug assembly that kept things on center. I machined the slot for the axle with a 1/2" ball end mill, leaving 0.02" of clamping room. 








I did, however, mess up cutting the side reliefs and overcut. The plan was to do the slot at 2.5" so I could use Anvil axles but since I'm planning on making my own anyways 2.25" works just fine!

More blind joints to hold together the extrusion and then I counter sunk two M12 bolts in the support plate to hold it on. Here is a good view of the assembly:









You'll notice I didn't face the 1/2" slider plate that mounts to the 160-40 spine. I debated this but all three slide plates were within 0.002" which seemed to me to be as good as I could expect of myself. When you consider all of the stack contributing to the center line of the frame, this seemed pretty good to me! If I wanted to go crazy I could have bought the cast mic aluminum remnant but that was $6/lb vs $2.5.


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## DSaul (Dec 13, 2012)

This is a jig I recently built for another builder. There are more pics on my Flickr page here https://www.flickr.com/photos/starrcycles/ if they help you with any ideas for yours. Some of the ideas were borrowed from Kris Henry at 44Bikes.


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## A. Spence (Sep 25, 2009)

seahuston said:


> For extrusion I used Misumi 40 series stuff. 160-40 for the bottom rail and 80-40 for the vertical. I HIGHLY recommend Misumi for your extrusion, it's really high quality and much cheaper than 80/20 brand. They also custom cut for no extra change so you only pay for what you need. My only complaint is that this series is drilled for an m12 blind joint hole. That's a big bolt!
> Total spend on extrusion: $153


Never tried the Misumi extrusions. Did you buy directly from them, or do they have an outlet store, kind of like how 8020 has 8020 garage on Ebay?

Alistair Spence,
Seattle, WA.


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## seahuston (Jun 17, 2008)

A. Spence said:


> Never tried the Misumi extrusions. Did you buy directly from them, or do they have an outlet store, kind of like how 8020 has 8020 garage on Ebay?


I bought direct from the Misumi website. It's a little bit clunky since the site configures a part number each time but it works pretty well. Their applications support is also super knowledgeable and ready to help and provide ideas. I can't say the same for 8020.

DSaul nice jig! Very similar to how mine will turn out. How did you align the measurement tape/pointers? I assume just make some measurements off the jig locations and glue it on?


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## DSaul (Dec 13, 2012)

The scales I used are self stick vinyl from McMaster-Carr. For convenience, I had to offset some of the pointers from the actual centers. I just took measurements from the bottom bracket and aligned the appropriate mark on the tape with the pointer before sticking it down. The pointers are from a Skil miter saw(I think). I was able to find them at eraplacementparts.com They still needed some modification, but I'm happy with the way they worked out. I can probably find the part number if anyone wants it.


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## seahuston (Jun 17, 2008)

*Bottom Bracket/Seat Tube Fixture*

Here is some more:

I didn't like the idea of the floating BB that some of the 8020 designs use. The clearance is nice but I didn't think my manual machining and no-rotary table setup would get me the tolerances that I wanted.










I decided to go with a fixed pivot. For this I made a block for the end of the seat tube and then bored and pressed in a brass bushing. After pressing it in, I reamed to size and counterbored for thrust bearings. The counterbore on the backside is sized so that the bushing sits just slightly proud of the housing.


























I turned the shaft from 0.75" steel bar stock










Assembled on the jig:


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## seahuston (Jun 17, 2008)

*Head Tube Fixture And Cones*

Head tube fixture is very similar to the bottom bracket but in this case I elected to put the pivot in the middle of the 8020 by pressing in and boring the bushing.










This ended up working out really well, I wish I had done the same for the BB. The second hole is for the cone mounting bracket. I went with a fixed bottom arm design. I'll swap in pucks of different heights for each head tube diameter to keep the rotation axis at the bottom of the tube.










For the cones, I did a 10 degree taper for the head tube and seat tube tops and a puck style for the head tube bottom. These are located by a dowel pin in the center and 1/4-20 bolts.










The arms were made from two different pieces of .5" bar that I bolted together and then finish machined. Instead of using dowels I put a key into the bottom.


















Last step is dummy axle! I don't often turn between centers so this was pretty fun! I think it came out really well without much drama. Messed up centering the slot so it's at 131.80mm not 132mm (starting with a road bike first).


















And then, just like that. It's DONE! Mounted it up on an engine stand I wasn't using. Now I really need to learn to braze!


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## PithyBikes (Dec 30, 2014)

Seahuston! I just found this thread. Great work and love the jig man!
-Steve


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## seahuston (Jun 17, 2008)

Thanks! Your awesome videos were a huge help!


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## MannaDesigns (Mar 5, 2013)

How did you end up machining the curved slots in your plates? You mention a few times that you weren't using a rotary table so was curious how you ended up doing it. Nice work!


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## seahuston (Jun 17, 2008)

For the curved slot on the ST extension, I attached the bracket and the pivot point to the plate and mounted it in the mill. I centered the mill over the locking hole for the angle screw. Using the pivot point (screw tightened so that I could just barely move it) to move the extension I drilled a hole and both ends of the angle sweep. Next I swapped in an endmill and with progressive depth cuts, manual swept the extension between the holes.

This worked OK but it was a little freaky (though nothing bad happened). I made sure to stand outside of the arc of the extension and put up safety stops (bolts) to make sure it couldn't over rotate.

For the HT extension, I printed out a hole table for 30 points along the arc and used an endmill to plunge the holes. Quick cleanup with a file and it looked like a pretty smooth arc. I didn't want to do the sweeping approach since the lever arm is so much shorter with this piece.

Both methods worked okay for me but I think I would just to the plunges in the future, feels a lot safer. Because the arc isn't the actual pivot point in this design, it doesn't have to be very accurate.


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## tangerhub (May 5, 2021)

Dear Seahuston - this is just awesome, 

it is a great thing to see you creating a jig out of the three

pithy-bikes
tanner W ( instructable) 
kristofer Henry (44 Bikes )


awesome: i also work on a 80/20 jig I think total cost gets approx 400 Euro 
At the moment i am working on a chainstay-mitering (fixture)


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