[GrundleJuice]

Hello and thanks for reading. I had been TIG welding occasionally at my previous job with no formal instruction and was enrolled in a local CC TIG welding course for this spring that has since been cancelled for obvious reasons. Hoping to pick up some experience and really learn the basics and good habits so I can make hobby welding something I do well instead of just good enough. My modest garage "shop" is evolving and turning out to work well for my needs so far. Long term goal is to build my own fatbike frame for winter cycling.

Resources like this forum and the YT channel are great to have and I appreciate them very much!

[Poland308]

Welcome. What kind of materials are you going to use for the frame. There are several bicycle builders around here. And several old posts on the topic.

[GrundleJuice]

Welcome. What kind of materials are you going to use for the frame. There are several bicycle builders around here. And several old posts on the topic.

Yes, I saw a couple threads with some bicycle talk. I plan to use some type of steel. Maybe 4130, maybe something more bicycle specific. Butted would nice but I'll see what kind of weight that saves vs cost.

[Poland308]

I’d recommend investing in a tube notcher with adjustable angles as most bicycle joints will be some variation of that.

[TraditionalToolworks]

There are some guys that do this on horizontal mills, notably old Nichols mills. You can pick them up pretty cheap and it would be a good option if you're mechanically inclined, which I would hope you are if you're building bicycle frames.

Josh's reply of a tube notcher is spot on, I just don't know how much they cost, my guess is you can pick up a used horizontal mill cheaper.

[GrundleJuice]

There are some guys that do this on horizontal mills, notably old Nichols mills. You can pick them up pretty cheap and it would be a good option if you're mechanically inclined, which I would hope you are if you're building bicycle frames.

Josh's reply of a tube notcher is spot on, I just don't know how much they cost, my guess is you can pick up a used horizontal mill cheaper.

I've been a practicing A&P along with doing lots of R&D for a DOD supplier (for lack of a better term), so I know my way around a shop generally. I have access to a vertical and horizontal mill which could be quite useful.

I’d recommend investing in a tube notcher with adjustable angles as most bicycle joints will be some variation of that.

See above. I'd love a tube notcher and have been looking casually for that and a frame building jig on the cheap. If I can't find any worth buying, I'll have to make my own setup.

[TraditionalToolworks]

I've been a practicing A&P along with doing lots of R&D for a DOD supplier (for lack of a better term), so I know my way around a shop generally. I have access to a vertical and horizontal mill which could be quite useful.

One thing to consider would be making your own tube notcher. Many people use a hole saw to create the coped area to fit the tubes together. If you had a jig that would let you offset the hole saw, you could move it around so that you can create the proper fitting for most any angle the tubes fit together.

Many people use a hole saw for 90 degree fittings, but if you could offset the hole saw, by changing the size of the hole saw you could in theory create a similar fit in a variety of angles. Even if some grinding is required, it would save a lot of time and get some really nice fitting tubes.

Just a thought, but that is kind of what people do with the horizontal mills, they use it to fixture the tubes to cut the coped area.

Here's a thread on Practical Machinists that talks about using the horizontal mill to create the fitting. Evidently people are saying that the fitting of a tube notcher doesn't cut the mustard for high quality frames. That I can't attest to.

https://www.practicalmachinist.com/vb/g ... ons-196370

[GrundleJuice]

One thing to consider would be making your own tube notcher. Many people use a hole saw to create the coped area to fit the tubes together. If you had a jig that would let you offset the hole saw, you could move it around so that you can create the proper fitting for most any angle the tubes fit together.

Many people use a hole saw for 90 degree fittings, but if you could offset the hole saw, by changing the size of the hole saw you could in theory create a similar fit in a variety of angles. Even if some grinding is required, it would save a lot of time and get some really nice fitting tubes.

Just a thought, but that is kind of what people do with the horizontal mills, they use it to fixture the tubes to cut the coped area.

Here's a thread on Practical Machinists that talks about using the horizontal mill to create the fitting. Evidently people are saying that the fitting of a tube notcher doesn't cut the mustard for high quality frames. That I can't attest to.

https://www.practicalmachinist.com/vb/g ... ons-196370

Thanks for the link!

I think with the irregular shapes if some of the tubing, especially the head tube, some amount of grinding is unavoidable without a fancy CNC machine if some sort.

[cj737]

You don't want a hole saw if you plan to use 4130 tubing. You want carbide mills, especially if you can get your hands on a horizontal mill. you will still need some type of filtering jig for angular alignment to position the tube end for milling. That can be made easily enough from some aluminum plate (3/8) with some milled holes, slots and use off-the-shelf clamping fixtures. Best part is to have the angular plate on a base that also pivots so you can do complex notches.

Milled, then tubing ends should only need the smallest amount of deburring when done. Else, you're doing it wrong!

[GrundleJuice]

You don't want a hole saw if you plan to use 4130 tubing. You want carbide mills, especially if you can get your hands on a horizontal mill. you will still need some type of filtering jig for angular alignment to position the tube end for milling. That can be made easily enough from some aluminum plate (3/8) with some milled holes, slots and use off-the-shelf clamping fixtures. Best part is to have the angular plate on a base that also pivots so you can do complex notches.

Milled, then tubing ends should only need the smallest amount of deburring when done. Else, you're doing it wrong!

I have no intention to use hole saws for anything other than making holes in doors for a doorknob. There are tubing notch cutters, rotating broaches, etc for this kind of stuff. A carbide mill would work, too. No amount of jigging will notch a tube to mate up to the compound curve surface of another tube without grinding or some sort of computer controlled movement, as far as I know of.

[TraditionalToolworks]

You don't want a hole saw if you plan to use 4130 tubing. You want carbide mills, especially if you can get your hands on a horizontal mill. you will still need some type of filtering jig for angular alignment to position the tube end for milling. That can be made easily enough from some aluminum plate (3/8) with some milled holes, slots and use off-the-shelf clamping fixtures. Best part is to have the angular plate on a base that also pivots so you can do complex notches.

Milled, then tubing ends should only need the smallest amount of deburring when done. Else, you're doing it wrong!

I have no intention to use hole saws for anything other than making holes in doors for a doorknob. There are tubing notch cutters, rotating broaches, etc for this kind of stuff. A carbide mill would work, too. No amount of jigging will notch a tube to mate up to the compound curve surface of another tube without grinding or some sort of computer controlled movement, as far as I know of.

Actually cj is correct, if you used a horizontal mill with a carbide mill you could set the angle in a fixture and mill the proper angle into the tube, that is exactly how other people are doing it. The key is in being able to hold the tube at the proper angle so when you move the mill table into the cutter, it can cut the proper angle. The it's just milling until the fit is correct. No computer involved, you just move the table on the mill once the tube is set to the proper angle.

In theory you could use a vertical mill, but the problem is they don't take side force nearly as well as a horizontal mill since the horizontal mill has an outboard arbor support.

[GrundleJuice]

Actually cj is correct, if you used a horizontal mill with a carbide mill you could set the angle in a fixture and mill the proper angle into the tube, that is exactly how other people are doing it. The key is in being able to hold the tube at the proper angle so when you move the mill table into the cutter, it can cut the proper angle. The it's just milling until the fit is correct. No computer involved, you just move the table on the mill once the tube is set to the proper angle.

In theory you could use a vertical mill, but the problem is they don't take side force nearly as well as a horizontal mill since the horizontal mill has an outboard arbor support.

Most modern bicycle frames have few if any constant angle notches. I can't understand how a mill head and or table that is not constantly moving could cut a tube to fit against another with a compound curved outer surface. I'm not a mill operator by trade so maybe it's just ignorance on my part.

Wouldn't notching the downtube to fit that head tube require a shaped cutter, CNC or constant cutting and repositioning over and over to get some sort of negative contour? That's one of the more tame head tube designs I've seen on new tapered headtube frames.

[Poland308]

It’s all about the angle. Unless the tube your saddling onto is bent then your working a straight line. Even bent you would be able to get a saddle milled with a straight cut close enough to weld. Your tube has such a thin wall on an application like this that it really won’t matter if the angle isn’t perfect flat.

[TraditionalToolworks]

I can't understand how a mill head and or table that is not constantly moving could cut a tube to fit against another with a compound curved outer surface. I'm not a mill operator by trade so maybe it's just ignorance on my part.

I've highlighted the key words here. As I have said before, the mill is stationary, this is not an end mill, this is what is known as a plain mill. You'll need to use your imagination here, but this is the type of mill you would use.

Imagine if you will that the mill stays stationary, but the end of the bike tube can rotate or move in any direction, it's up to you to fixture it. with the tube held to the table on some type of fixture, you move the table towards the cutter and it essentially mills a notch into the end of the bike tube to fit another bike tube which you weld onto the side of.

using plain mill on a horizontal milling machine

slot-slab-mill.jpg (53.17 KiB) Viewed 1709 times

Wouldn't notching the downtube to fit that head tube require a shaped cutter

Yes, you use a mill/cutter that is the size of the tube, therefore the shape you mill into the end of the tube fits on the side of the other tube you weld it to. You can create a fixture that holds the bike tube in any direction you desire, and you have both sides of the table to mount the fixture to. The options are endless...If you look at the arbor support you can get an idea of how rigid a horizontal mill is when milling like this.

Go back to the link I posted above, in the 2nd post of that thread you can see how you would mill a tube end to weld to another tube side.

[cj737]

You don't need a horizontal mill for bicycle tubing. A vertical/knee mill will be just fine.

You need this type of tube jig: https://www.youtube.com/watch?v=P5HBuKXW4bg&app=desktop
Install that onto the table of your mill, position the tube at the correct intersecting angle to the cutting tool, then advance the table into the cut.

You would do well to buy/make a frame jig. This helps you establish proper lengths and angles for all your tubing.
http://kirkframeworks.com/anvil-frame-jig/

[TraditionalToolworks]

You don't need a horizontal mill for bicycle tubing.

cj, indeed you don't. However if you want the best tool for the job it is the preferred way many professional bike builders do it. I agree and mentioned above, a hole saw works, but pales in comparison to a horizontal mill with a good jig.

I bought that Nichols mill in the pic on Ebay shortly after Ebay was started for $17. People were still trying to figure out how to list and price items...the auction started out at $0.99...

That said, not hard to find a horizontal mill for a couple hundred bucks if one looks. They're not in high demand, and one reason bike builders like to use them.