Drilling calculations

[metiz]

Hello everyone

For school I need to describe the production process for several items to the detail. I've run into problems with drilling calculations.

I need to drill a 6.5mm hole through a 6mm deep piece of Ms58 (brass) but I can't find the calculations to do so. (on a lathe btw)

Can anyone help me with this? I need to calculate drilling time, power consumption and the likes.

(In metric)

[Johansson]

Holy crap that is corny, do you have do describe how to drill a hole??

[wolfdragon]

More than likely they want to full on heres the process type thing.. I hope... how to drill a hole wtf...


Assuming that you are already chucked up and centered with a tolerable runout it is

square the surface
spot face pilot star the hole
drill to depth with a smaller drill bit (assuming this is a through hole)
ream or boring bar to finished OD
chamfer edges if required

as for what bit to use first... brass is super easy to do so I'd use a 5mm bit to blast the hole out and then go a tapered start ream that straightens out at 6.5

[metiz]

Thanks, but I need the calculations, unfortunately. RPM and time it takes to drill it.

[Johansson]

20.000rpm, 0.5 seconds. There you have it! ;D

[metiz]

Are you serious? if so, can you show the calcs?

[Johansson]

Jan 21, 2012 13:28:56 GMT -5 metiz said:

Are you serious? if so, can you show the calcs?

Ha ha, no that was a joke.

[racket]

Hi Metiz

You'll never be able to workout the power consumption , it'll depend on a multitude of variables ............drill sharpness,angles, temperature of the lathe bearings/lube , general frictional forces , lathe rpm potential etc etc etc

LOL, considering the variables I've run into over the years when drilling holes you'd be lucky to get within 50% of the theoretical optimum........................this has got to be a joke question they're asking of you.

Cheers
John

[metiz]

Unfortunately not. The theoretical numbers are ok. If not power consumption, then theoretical drilling speed.

Other calculations for decreasing a cilinder in size on the lath, for example, are: n=Vc*100/(pi*d)

You seem like you know your way around the lath, could help me out with at least the calcs for drilling a certain depth in a certain material?

[wolfdragon]

metiz, you need a copy of the machinist's handbook aka machinery's handbook, it has lists of feeds and speeds for various materials and hole sizes

[metiz]

Good idea but I kinda need the info tomorrow

[racket]

Hi Metiz

Theres plenty of info on the Net , but an rpm of 2,500 and a feed rate of ~0.15mm/rev would do the job in about 1 second ...................the catch will be getting the drill right through the material as you'll need to calculate the time taken from when the point enters the metal until the OD of the drill enters it , and add it onto the time for the drill OD to pass through the 6mm .

You'll need to get the drill angle and do some calcs , ...................consult a machinist's handbook as Wolf suggests ..................I'm only a backyard machinist :-))

Cheers
John

[metiz]

"Backyard mechanic" I've seen real meachanics not half as good as you (if this ass kissing isn't working, let me know )

Anyway, thanks for the numbers! where did you get them? also, what does 0.15mm/ revolution mean exactly?

[racket]

Hi Metiz

LOL.....................ass kissin' doesn't work with me :-)

The numbers are in my head , but a quick Google will throw up what you need .......................0.15mm/rev means every time the lathe chuck turns one revolution the drill is fed 0.15mm towards the article being drilled, though how you'd accomplish this on a lathe without mechanical feed I don't know, much easier on a drill press with automatic feed .

Cheers
John

[Richard OConnell]

OMG i just realized what is this doing in turbine discussion?? anyways yea, I have to agree with anders