couple of questions regarding tube thickness, brazing and milling

[bencooper]

B.Cooper 8-12 tpi (fine pitch) at what speed would you use for a 40 mm hole saw?

As fast as my DeWalt goes ;-) 1200rpm or so I think.

Manual feed, definitely - I find that I don't need to push much at all, it pretty much pulls itself into the work. I was worried about snagging too, but best thing to do is have a go with some old tubes and see what happens.

[John Winston]

setup: whatever mill you have. the least amount of tubing 'sticking out' from where it is clamped. as short of an arbor that will get the job done. your mill quill retracted (for starters)
I run my spindle speed around 165 rpm. manual feed is fine (though boring). If you've auto feed, that will free you up from standing at the mill for a few minutes.
It exciting when your feed is too fast or your setup isn't rigid. Usually results in a broken tooth or two on your saw, and a chewed up tube. Either way, if you were sleeping, it'll wake you up.
Experiment. You'll find there isn't any issue mitering on the mill.

[Eric Estlund]

For tubes, it's a and b.

[Amaro Bikes]

Hola, Andrés.

It's not just a or b, but as Eric said, both parts take place. 0,8mm thickness tube without the previous lug "reinforcement" makes a thin tube (hainv in mind you're actually surrounding it by three tubes (tt+2ss) with their HAZs. Also, the thinner the tube, the more easily heat distortion to happen
The use of heatsinks is helpful with TIG (although not necessary if you manage good travel speed), but not so sure about it when brazing as they'll take heat needed on the tubes to make the silver/brass flowing.
When Tig welding you'll also have to keep in mind the welding puddle "geometry" avoiding any "peak" or "discontinuity" where tensions will accumulate and create a possible failure on fatigue after time.

If you ask for my personal opinion, I would go with a minimun 1mm thickness on the area, with also a bonded alu shim (I do usually go with 31,7 seat tubes and 27,2 seatpost, so enough space for the shim and much more confidence on the long time realiability).

Cheers

[steve garro]

As fast as my DeWalt goes ;-) 1200rpm or so I think.

Manual feed, definitely - I find that I don't need to push much at all, it pretty much pulls itself into the work. I was worried about snagging too, but best thing to do is have a go with some old tubes and see what happens.

This is in jest, right?
- Garro.

[bencooper]

This is in jest, right?
- Garro.

No. I know the rules about cutting speeds and this goes completely contrary to them, but it works very well with this setup.

[ToddFarr]

This might help some find a starting point for holesaw RPMS. Found it flipping through my black book yesterday at work.

[bencooper]

Yes, though it's worth pointing out that those speeds are assuming the hole saw is cutting into a flat surface so quite a few teeth are in contact with the material. Mitring a tube, you're effectively cutting edge-on, and even with a 10tpi hole saw you only have one tooth in momentary contact with the material at any one time.

[Andrew R Stewart]

I've read the many posts over the years about cutting speeds, hole saws, tooth counts and such. I agree that rigid set ups are first and formost important. But I found with both my loose Atlas 6" lathe and the Joint Jigger I had the faster cutting speeds worked better. Truing up or grinding the hole saw's outside is a good idea. Always wanted to try Andy S's cutters but at the rate I build a hack saw, grinder and file is almost as quick and much easier to set up. Andy.

[arregui]

Thank you very guys for sharing.
I think i got they idea on the seat cluster joint vs. thin walls.

on the hole saw issue not that clear thought. I guess this is the point to try and error.
I tried high speeds before and with some tubes the thing get really hot and teeth cant go through.
the right conditions to make a nice cut seems to depend much on the type of alloy.

ill try low and high speeds with 4 tpi and 10. ill try grinding (Andy you mean like sharpening, right????) the outside of the hole saw also.

again thanks, i i can say something new out of my cuttings ill keep you posted.

Andrés