Thread: drilling brass?
ping...cue ricochet sounds as another M2.5 drill bit whizzes past ear and off wall behind me...
I decided to have a go at iimproving backlash on the cross-slide of the lathe by drilling two holes through the nut parallel to the axis of the thread, tapping them M3, drilling M3 clearance 1/2 the length and cutting a slot across the nut 1/2way along...
well i never got past step 1... the HSS M2.5 drill hardly made a dent before snapping... and the second fared little better...
I thought brass was about the same as ali to work...clearly not... so where am i going wrong...
Off to order another job lot of M2.5 drills!
Is this old brass?
I used to have terrible trouble with brass and it's wonderful tendency to snatch, but not for many years, thought maybe they'd improved the formula and the world had standardised on CZ something or other.
To drill it you mustn't have any slack in the system, it mustn't be able to pull the bit forwards and dig in. That was it's ambition in life.
Lube might help, you could soften it up, possible not a good idea if it's a bearing face. Treat as per copper, apply soap, heat 'til it goes black. Quench or air cool makes no difference, only way to harden brass is to wait a few years.
Edit: Forgot, it does work harden
Um, err, good luck :whistling:
Last edited by Robin Hewitt; 19-01-2010 at 01:15 AM.
old as in 100 years give or take 5 - the lathe was made in 1914!
i've ordered some stubbies....
The cutting edge of the drill needs to have a negative cutting angle. Grind a flat on the cutting edge. This way the drill can't snatch.
Sorry Peter you'll have to explain that more
The problem is probably 'engineering speak'.
Brass 'snatches' where other metals 'dig in'. It has a word all of it's own, probably because it does it so well.
If Irving, thinks 'dig in' rather than 'snatch' then the 90 degree, or more, rake angle might make more sense.
I understood the snatching bit... it was the negative rake angle I needed clarification on... I dont do drills - when they get blunt I replace them, when they break I replace them. I have never sharpened a drill or taken a grinder to one.. but I found this description helpful. A picture paints a thousand words and eventually found one that mentions drill and rake angle in the same sentence... but I am still not clear what it should look like when I am done.. or how I am going to do this on a 2.5mm drill... I suppose the die grinder held in the vice and a small wheel as my big griinder is...too big!
You just need to remove the sharp cutting edge, use oil stone or diamond file.
Only problem then is they are not much use for steel!
Mind you if you keep breaking them you will have enough for a separate brass set.
I always thought the cz bass was worse for snactching than plain brass.
hmmm I wonder then if I could repurpose the broken end, its still got about 20mm of fluting on it... i'll need to regrind the point but I reckon I could manage that using the diagram... well I can't do any worse I suppose....
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