Framebuilders - Fast back issues

I am a new frame builder, been building for about a year and a half. I have been using fast-back style stays on all my frames just because I like it better than other styles. My problem is this, I miter all my tubes with files because I don't have a mill or any other machinery of the nature. Mitering 2 identical seat stays by hand is the most dificult process I have in each one of my frames, I can continue to do this however I was wondering what I would need to make this process a little better. I read on one website of a guy who spoke of this exact problem and said he uses a vertical mill, sounds expensive and you would still have to have some sort of jig to get the compound angles correct on each different frame correct? Can anyone tell me the best way to do this process and any other means that could save me a little time? The cheaper the better. Any advice would be greatly appreciated. Thanks.

Dimitri
MEECH

I feel your pain.

Just thinking out loud but what about a cylindrical sanding drum with the same OD as your seat tube (or lug as the case may be, and then a wooden fixture of the correct angle. You could mount the drum in a drill press and then feed in the stay using your fixture to provide some guidance. It would still require careful detail filing for the final fit, but the setup should get you close.

I used to do the whole back and forth 30 times with each stay process until I worked in a shop with Anvil fixtures and had one of those head slapping "duh, why didn't I think of that before?" moments.
What you need to do is make something that will clamp both stays together in the right position- fit the stays to the drops while leaving the tops a little long-hold the stays in the right position (the tops are usually touching each other) and clamp them- now,leaving your clamp attached, put the stays in the vice sandwiched between a couple blocks- hold the file at the right angle, and do both miters at the same time!
Of course I don't have any pics to show:rolleyes:, but there isn't much to see and since I made my clamp from a piece of my jig and a couple of Anvil clamping blocks, it probably wouldn't help anyway.
Hope this helps!

ps-
I still hand file everything, but check out the pic, it took all of 10 min to fit those stays to the st.

These are both good ideas and I appreciate it. I guess its sick to be happy that you all are feeling the same pain but I am happy I am not alone. The machinery to do this stuff is too expensive and the guy who taught me how to build frames said sometimes it takes longer to get the machines set up right than it does to file it by hand, so anyway thanks again. And if anyone else wants to throw a dog a bone, I'm listening.

I used to do the whole back and forth 30 times with each stay process until I worked in a shop with Anvil fixtures and had one of those head slapping "duh, why didn't I think of that before?" moments.
What you need to do is make something that will clamp both stays together in the right position- fit the stays to the drops while leaving the tops a little long-hold the stays in the right position (the tops are usually touching each other) and clamp them- now,leaving your clamp attached, put the stays in the vice sandwiched between a couple blocks- hold the file at the right angle, and do both miters at the same time!
Of course I don't have any pics to show:rolleyes:, but there isn't much to see and since I made my clamp from a piece of my jig and a couple of Anvil clamping blocks, it probably wouldn't help anyway.
Hope this helps!

ps-
I still hand file everything, but check out the pic, it took all of 10 min to fit those stays to the st.


Great advice, but I'm finding it really hard to visualize exactly what you are doing. BTW, when you refer to stays, I assume you mean seatstays, and not the chainstays, correct?

My method involves building the rear triangle of the frame first. So, I'm not sure if I can do a simple jig like you describe. I start out with the chainstays and braze them to the dropouts. Then, I braze the chainstays to the BB. Now, I file the seatstays and recheck ever like 50-some-odd times, usually cursing that one seatstay is not exactly the same length as the other. Does this seatstay filing jig of yours look like a brake-bridge boss of some sort? Can I even attempt your method if I completely braze up my chainstays first?

A vertical mill isn't necesarry and horizontal mills show up for a few hundred with regularity and are in some regards better. To figure out the tooling, look on the Anvil site, their jig is not all that complicated to make a rougher version of.

There is a third option and that is to use a Bontrager stay approach. In this approach the lower stay slides into the upper stay (normally aircraft chromo), think of the stay like a radio arial. So when you fix the lower part, you can extend the upper part until it touches the seatstay, mark the cope, file it, extend it further till it touches again, make new marks, and get it just right. It is enormously faster and easier because the stay is not fixed in length. When you get the right overall fit you can remove the upper piece and trim for length at the overlapping end then braze or weld up. While I have never seen it done this way, it should be possible to do a similar thing with a tapered stay and shorter piece that would end up looking a bit like a lug. Since you don't have to worry about taking away too much, you could even freehand the cope on a abrassive coper for max speed.

Just an Idea but if you can fit one stay fairly easily, then take a paper pattern of it and put it on the other stay and go to town, might get you a whole bunch closer in a hurry..............

Hey Live Wire, I like your idea about clamping the seat stays and filing at the same time, I think its the way to go however I have a question. In your photo of the 29er, the stays are mounted more or less on the side of the seat tube, this is good because I prefer to mount my stays rotated around a little as well, I think it is more stable and it gives room for brazing, however when you clamp the stays together before filing don't they have to have the gap between them when you clamp it or can you clamp them together touching at the top, file them, and then still be able to rotate them outward? Is this making sense? Keep in mind I will be happy with 2 stays mitered identically but I prefer to have them sit on the seat tube sort of like a cross between directly behind the seat tube and mounted on the side of the seat tube, follow me? Thanks for your time. Are you Mathews Cycles, the same as the link you post on here? If so, that video that is posted on your blog of the monkey kids on bikes is far out there, way out there. Gives me bad dreams. Later.

Great advice, but I'm finding it really hard to visualize exactly what you are doing. BTW, when you refer to stays, I assume you mean seatstays, and not the chainstays, correct?

My method involves building the rear triangle of the frame first. So, I'm not sure if I can do a simple jig like you describe. I start out with the chainstays and braze them to the dropouts. Then, I braze the chainstays to the BB. Now, I file the seatstays and recheck ever like 50-some-odd times, usually cursing that one seatstay is not exactly the same length as the other. Does this seatstay filing jig of yours look like a brake-bridge boss of some sort? Can I even attempt your method if I completely braze up my chainstays first?

Yup, talking seat stays here.
My jig is just a 1"x 8" piece of steel with a slot in it with the anvil blocks bolted on, looks kind of like the top of a brake boss jig. You just have to have a way to clamp both stays so that they stay in alignment with each other.
I fit my seat stays after the rest of the frame is brazed up, so if I understand your question right, it will work fine for you.

Hey Live Wire, I like your idea about clamping the seat stays and filing at the same time, I think its the way to go however I have a question. In your photo of the 29er, the stays are mounted more or less on the side of the seat tube, this is good because I prefer to mount my stays rotated around a little as well, I think it is more stable and it gives room for brazing, however when you clamp the stays together before filing don't they have to have the gap between them when you clamp it or can you clamp them together touching at the top, file them, and then still be able to rotate them outward? Is this making sense? Keep in mind I will be happy with 2 stays mitered identically but I prefer to have them sit on the seat tube sort of like a cross between directly behind the seat tube and mounted on the side of the seat tube, follow me? Thanks for your time. Are you Matthews Cycles, the same as the link you post on here? If so, that video that is posted on your blog of the monkey kids on bikes is far out there, way out there. Gives me bad dreams. Later.

Where the seatstays contact the st depends on how much you want to file. If I start with the stays touching and just file enough to make the miter, the stays will attach on the back of the seat tube- the deeper you file, the farther apart the stays get. For the bike in the pic I wanted a lot of tire clearance, so that's why they attach there. Like everything in framebuilding, you get a better feel for the process the more you do it.
I'd post an in process pic, but I took the jig apart to retap a hole in a block and haven't touched it because the next two frames look like they'll have straight side-tacked stays.

Yup, thats me in the link- the monkeys kids are too freaky, aren't they? Funny how they all meet a horrible end. What the hell were they thinking with that film? Gotta love the 70's!
-Chauncey

Gotcha. Thanks for the help. You do some nice work. Keep the videos coming even if it is scary,its much better than real TV. Later