Cobra Stay Slayer setup

I’ve always mitered my seat stays at the TT/ST junction by hand using BikeCAD’s paper templates. It’s fairly quick but fiddly and not easy to get them nuts on.

So I bought a used Anvil SS fixture and tried it out. The miter was excellent but it took ages to set the dang thing up. After a couple of attempts I switched back to the paper templates.

When Joe at Cobra released the Stay Slayer it was hard to resist. The thing looks fabulous. I now have one sitting in my workshop and will use it later this week on a frame. But before I do, I’d love to get a head start.

Is anyone willing to share their setup process for the Stay Slayer? Do you use a dummy axle or the measuring rod? Which BikeCAD dimensions do you use to set it up? How do you quickly lop off the extra tubing so they don’t bump into each other passed the cut line?

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I might be able to help with the Anvil fixture (I own I think the first one Don ever made of the SS fixture, as well as most of the other stuff, since I was his test mule for a bunch of stuff) if you want some tips there. I can get it set up in a minute or two at most usually, I think, though I haven’t timed myself.


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@anon91558591 If you’re willing to share your setup process for the Anvil fixture, I can likely apply it to the Stay Slayer. Plus, there’s probably plenty of other builders with the Anvil who could learn from you. Thanks!

Ok, I’ll take a crack at it.

First, I’m assuming you’re mitering the seatstays free (ie, you haven’t welded them to dropouts yet) and that you’re done with any bending/manipulation you plan to do.

Step 1: Adjust your dropout dummy cones to approximately the width of your actual dropouts. You don’t need to be particularly careful about this, just get close. My fixture is old enough that it doesn’t even have a scale for this, I generally just eyeball things these days.

Step 2: Install seatstays into your clamps/v-blocks and make sure they’re even/centered and that they’re not twisted out of plane. This can be really quick if you have a newer fixture with a centering wedge, or it can take a little futzing around if yours is as old as mine. Regardless, though, having the stays perfectly centered in the fixture doesn’t really matter. Having them extending out from the clamps evenly is more important, and you can accomplish this with the aid of a parallel and your eyeballs.

Step 3: Set your desired angle (generated from a CAD program or via whatever method you use) and get your hole saw centered. The quick and easy way to do this is to back the table away from the spindle/saw a bit, lower the saw to the point where the teeth are below the stays (so that the side of the saw will touch the stays as you tram in), then start the machine and sneak the saw in closer and closer. Since hole saws are never perfectly round, you’ll get to the point where the high spot on the saw is just tapping one stay. Once you get it just barely tapping both (your eyes and your ears will tell you) you’re good.

Remember, you have to have the stays extending evenly from the v-blocks for this technique to work.

Step 4: In some cases, your setup might not be rigid enough to keep the stays centered, since the saw is pushing one stay and pulling the other. If you find that your miters end up slightly offcenter because of this, you’ll want to tram over on the X by a small amount (ie 25-50 thousandths or so) to compensate. Experience will tell you how much (keep notes) so that you can compensate on the initial cut going forward.

Step 5: Seatstays are thin and hard to hang onto! It’s easy to mess them up in a mill, so don’t fully tighten the drawbar. Just go hand tight, no wrench. If you do snag something or break a tooth, you’ll just spin the arbor in the collet instead of destroying the stay. And no, you won’t hurt the collet or the arbor doing this at bike mitering speeds/loads (unless you leave it running for a few hours). Don’t do it for anything else, though.

Step 6: Miter away.

Hope that makes sense.


Wow, great tip! I will try this out next time and see how it works.

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Thanks @anon91558591! You make it sound so easy while I feel like I’m sweating bullets.

Have you already mitered the stays at the dropouts before setting them in the fixture for the ST cut?

How do you determine your cut length? Or do you eyeball the length, err on the long side, and make successive cuts until you’re happy with where they meet the ST?

I don’t miter the seatstays at the dropout end at all, just cut them to length (after I’ve made my seat tube miter) and then weld them on. On a hooded dropout I might do a quick pass with a rat tail file so they stay in place on the hood a bit better while I’m tacking.

So I do my seat tube miter, then adjust/cut from the other end to determine how high/low the stays meet the seat tube. Does that make sense?



Thanks @anon91558591! That seems so simple. I’ll have to give it a go.