# Newbie- drilling with small dia drills



## cruiser1 (Aug 26, 2012)

Need to drill brass with a # 75 drill bit- what speed do you recomend
do i peck at it - should i get cobalt bits - flood coolant?- any tricks to this
before i ruin anything?


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## Tin Falcon (Aug 26, 2012)

run it fast like 30,000 rpm or as fast as your machine will allow.  
yes peck, coolant will help. no need for cobalt on brass. 
Tin


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## prof65 (Aug 26, 2012)

Brass needs very sharp tools, so if piece is "critical" use a new drill bit.

Roberto


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## Sshire (Aug 26, 2012)

Be careful at breakthrough. Brass grabs. I've been working almost exclusively with brass on my Epicyclic engine build and I started using a diamond file to knock the edge of the bit. That helped, although if the piece is held in a vise or clamped correctly, sharp bits haven't given me any problem.


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## cruiser1 (Aug 26, 2012)

Thanks - wish me luck - the smallest i have delt with is a #43 - i have 8 hrs
in the part already - already bought some ALUM- and a rope to hang myself
just in case


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## Aydelott (Aug 26, 2012)

ive  never seen a machine that can run 30,000 rpms what do you have Tin ? if you have a smart phone there apps you can get to calculate feeds an speeds i machinist, journeyman machinist,  if not Google it there are a few formulas for it i would give them to you but there at the shop


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## Maryak (Aug 27, 2012)

3 x drill dia = depth of cut before the flutes must be cleared. The smaller the drill the shallower the depth between cleans.

Best Regards
Bob


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## Tin Falcon (Aug 27, 2012)

I used the data and calculator on the LMS site.
http://littlemachineshop.com/Reference/CuttingSpeeds.php
#75 bit =.021 sfpm 160 those numbers come out to 290102.
I think I plugged in the size of a 76 yesterday . like you said most machines will not go that High . my x-2 with pulleys get up there pretty well have not clocked it. 
I would put my dremel tool in the dremel drill press adapter a dremel goes to 35000rpm .
Tin


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## jtrout13 (Aug 27, 2012)

How deep is the hole?  You might want to use a "sensitive drill attachment" which makes it a lot easier.  Check out Little Machine Shop # 3790.  There are much cheaper alternatives out there but that's the idea behind it.


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## Ed T (Aug 27, 2012)

As stated above, spin it as fast as you can otherwise the surface speed of the bit is too slow to do much. The most likely cause of a broken bit is that the chips got stuck in the hole so, yes, peck and don't try to cheat; just do it. In my experience Dremel tools don't have wonderful bearings, so if the hole size is real important, I'd not go that way. Buy several drills. In a previous life we found that some of the tiny ones look like drills but don't actually cut. Also it's likely you will break one or two. Since you have a lot of time in the part already, I'd be inclined to learn how to use the tiny drills on a test piece before doing it for real. In fact, I find that learning how to do a new process is almost always worth doing on a trial piece to get down the learning curve a bit before trying it for real. A Dumore high speed, precision drill would be a great tool for this, but a bit spendy for just a few holes.
Good luck!!


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