Mitering the Downtube for My Hardtail MTB Frame!
HTML-код
- Опубликовано: 7 фев 2025
- The hardtail mountain bike frame build continues. Today: Downtube mitering!
First, I cover a bit about tube rolling and dealing with bicycle-specific tubing (butted tubes, specifically). I discuss how I rough cut my tubing to length and how I use BikeCAD to determine the length and angles I need for mitering. Then I make the miters at both ends of the downtube (using hole saws in a Bridgeport vertical mill), and I demonstrate how to fine-tune the fit-up between the downtube and head tube with a hand file.
Here is the playlist of the whole Hardtail Mountain Bike Frame Build-I'll keep adding to it as we go: • Building a Hardtail MT...
SUBSCRIBE for more videos on bicycle framebuilding and other shop-related topics: / @cobraframebuilding
SHOP MY TOOLS: If you're looking for bicycle framebuilding tools: cobraframes.net.
FOLLOW my shop updates on Instagram (@cobraframes): / cobraframes .
MUSIC: "Star Eyes" by urpleactus ( / urpleactus )
![Felix "Unfair" | [Stray Kids : SKZ-PLAYER]](http://i.ytimg.com/vi/Oswujxm2Ag0/mqdefault.jpg)
such great thinking throughout... brilliant... inspiring
While I will never build a frame I really appreciate you taking the time to explain it all. Very interesting thank you.
Thanks for watching!
You're one of the main inspirations for me getting into welding
Make me proud!
Hole saws typically cut more at the welded seam and oversize. Turn the cutter in reverse and grind OD of cutter till it cuts the right diameter. It will grind more on the weld and make the cutter more concentric.
The angle should've been 20.9 degrees, not 21.9 ... 06:42 - that probably explains the gap at the bottom of the DT/HT miter
One thing I like to do for marking cut to cut distance is to use the mill itself. If you put any sharp, concentric point in your quill and mount your tube square to your table after your first cut, you can use the mill DRO to measure to the next cut edge or at least make a known measurement mark on the other side of your tube block. It's still not ideal, but I find it less finicky than using a ruler.
Not a bad idea. My mill’d DRO doesn’t have enough travel for every length of cut but you could at least transfer the Mark looks you said.
@@cobraframebuilding Mine usually doesn't either. But I usually make my transfer mark and then use a big old caliper for the final. It doesn't really save any time over the ruler method, but I'm clutsy enough that it's worth it. Your videos are excellent by the way.
can i know that butting cnc machine model name? so...i want know tube butting cnc model name
sorry...im korean so im not good at english.
thankyou!
30:24 lol
what are the spindle speeds and down feed speed you are using?
Spindle speed depends on cutter diameter. Usually 330 or whatever is in that ballpark for larger diameter cutters and 660 or 1100 for small cutters. I forget what specific RPMs the step pulleys give you. And probably .003” downfeed per rev, but I forget. .0015” and also .006” down per inch are options also and they work. Seems to be fairly forgiving but if you did production you might notice big cutter life gains by optimizing the setup, and I haven’t ever done that.