Drilling copper fail..

[minimutly]

I've spent way too much time making a sink for the welding of one of the legs of the float valve on a Hitachi carb. I cut it out of a piece of 8mm copper, filed to fit around the spot face of the socket that the brass valve screw up against, got it perfect.
Then I drilled through so it could be used to mount the new "leg" to. Or rather I started to drill it - 2.5 mm, pillar drill on max speed, take it easy, but, maybe not easy enough... It looked like the high speed and not enough clearing caused the swarf to melt and bind - snapped the drill bit... I tried and tried to "unscrew" it with some pointy electronics pliers, no way was it shifting. So the decision was made to turn the piece around and drill the other side. Well bu**er me, I did it again!
So now I'm on attempt no 3, pics when finished, with a lot of luck will have 2 legs on the carbs float pivot...
Edit to ask - what's the trick with this copper drilling - less speed?

 

[Dee J]

Copper is sticky-chewy stuff. Less rake and drill slow. Tbh for a 2.5mm hole I'd use an old egg-beater hand drill so I could feel when the bit catches.

 

[BrokenBiker]

slow speed for copper. i snapped god knows how many drills trying to put a 4mm hole in bit of old bus-bar

 

[Erie Fred]

Was in a shop doing allot of bus bar work, drilling thick copper bars.
Allot of drills were butterfly ground.

 

[Pete.]

Use milk as coolant for drilling copper.

 

[tom2207]

Was in a shop doing allot of bus bar work, drilling thick copper bars.
Allot of drills were butterfly ground.

whats butterfly ground , a new term to me

 

[Shiny Steve]

Milk?

 

[BrokenBiker]

Use milk as coolant for drilling copper.

is that genuine or do you just want to see which ones of us fall for it?

 

[Pete.]

 

[Erie Fred]

is that genuine or do you just want to see which ones of us fall for it?

No, it's a real thing.
Most shops have switched to some form of synthetic coolant, but in day's past, it was the goto for copper.

 

[Onoff]

Will oat milk work for the vegans on here?

What about yoghurt?

 

[Erie Fred]

whats butterfly ground , a new term to me

regrinding the end of a twist drill to look like a wood spade bit is best I can describe it.

 

[Pete.]

Will oat milk work for the vegans on here?

Why are you thinking of drilling one?

 

[Onoff]

Why are you thinking of drilling one?

Now looking up "celebrity female vegans"...

 

[Morrisman]

regrinding the end of a twist drill to look like a wood spade bit is best I can describe it.

Grinding the cutting edge to give zero rake, we called it ‘clipping’ the drill, used to do it for drilling brass too. So the swarf sprayed off neatly and it didn’t suck the drill bit into the job.

 

[minimutly]

Thanks all, wish I'd asked before messing the job up...
Milk and slow it will be, eyes not good enough to regrind a 2.5mm drill. Glad it wasn't just me to do this...

 

[Kram]

I have done a reasonable amount in copper and not had issues. Too fast rpm? What speed is your pillar drills high speed?

Milk may work but I have learned the lesson with veg oil that food based will eventually go rancid/sticky/smelly and has no place near a lathe.

Oil works fine. Engine oil thinned with wd40 is my choice. RP60 for getting a nice finish.

 

[minimutly]

Max speed? Estimate around 6000 rpm, based on pulley sizes alone. I think a syringe full of milk shouldn't make too much mess, but I take your point.

 

[Kram]

I'd suggest 1500 or so as that works for me on lathe. 6k might be closer to the ideal speed but my lathe wont go that fast.

 

[Erie Fred]

Grinding the cutting edge to give zero rake, we called it ‘clipping’ the drill, used to do it for drilling brass too. So the swarf sprayed off neatly and it didn’t suck the drill bit into the job.

Not just the rake, no drill point angle either, other than a little tit in the center.