Through cuts in thin brass with 1/16 upcut spiral

[walter_davis]

I am cutting a production run of pieces from .032" wall brass tubing (272 alloy). Using a 1/16 no-name upcut spiral carbide bit starting from the Shapeoko aluminum settings, but reducing the layer height to .05mm and the feed to 360mm/minute. Also cut the plunge rate down to 100mm.

My cut is set to climb, inside contour cut, with 10% ramps. I have the HDZ on my S4 XL, and a no-name spindle at 18K. Workholding is an interference-fit pocket in MDF, and there is little to no vibration, except during plunge.

As I have tried to raise my cut speed, I notice that I am snapping bits on the smaller features (a 3.5mm hole) while the larger 4.5mm holes and 3mm slot are not affected. I’m on my last bit, and so my questions are these:

1. Is there a better bit for this? These have a long nose, but I am only cutting to a 1.1mm depth to clear and finish the hole.
2. Do I need carbide? These are, but would HSS be stronger in a lateral stress? Brass is nice and soft and clean-cutting.
3. Would a different RPM make a difference? Higher? Lower? This “feels” like a harmonic thing. The snap happens as the bit is negotiating a relatively sharp turn and plunging at the same time.
4. With that in mind, would turning off the ramps be better?

Any and all thoughts appreciated.

[Dooryard (Knox)]

is using a 1/8" bit acceptable for your design? bit strength will go up quite a bit and should still be able to accomplish a 3.5mm hole. 3mm slot will be a challenge though haha

fwiw I’ve been cutting a lot of brass lately and oflute bits have worked really well for me. but idk if that exists in 1/16" or not.

[SLCJedi (Josh Tenny)]

With that small of a diameter, I’d go 2 flute. They’re stronger. I’d also get the shortest flutes possible to cut to the desired depth.