Will my spindle even allow me to drill

[William]

Hi All, I have a project with a number of 4mm holes. This boring bit looks perfect:

https://www.toolstoday.com/v-6755-304004.html

but... my 5hp spindle is rated for 12,000 - 24,000rpm and, I'm assuming, the 12000rpm bottom end is far to fast for a boring bit.

Does that mean that I'm out of luck or do I not understand how the spindle works and it can actually go slower?

Thanks,
William

[barney]

I have drilled thousands of holes from .062 to 35 mm with my cobra.
I have used rpms slower than 12,000 but I did not know that they are rated for
12,000 plus.

[William]

I have drilled thousands of holes from .062 to 35 mm with my cobra.
I have used rpms slower than 12,000 but I did not know that they are rated for
12,000 plus.

Sorry Barney, I'm very new at this and "rated" may be the wrong term. I have a chart which shows 12K to 24K and I just don't know how variable they are.

For a 4mm hole, is there an RPM and plunge rate that you would recommend?

Thanks,
William

[TimPa]

i see that the bit has a left hand twist, is that similar to cutting in the climb direction? is chip removal adequate for bit cooling?

i also have some drilling projects coming up and very interested... thanks!

[barney]

Good catch Tim that bit would not work in a spindle. You need a right hand twist usually black.
William I run my 5mm boring bit at 12,000 rpm 150 ipm plunge in melamine.

[guitarwes]

Use an 1/8" upcut bit and profile inside the hole with a spiral ramp in one pass.

4mm to inches is .1574. I would draw .158 holes and cut with the bit mentioned above. 12k rpm at 150ipm.

[Charlie_L]

With my smaller machine I do the same as Wes. Slightly different speeds, 10k rpm and 100 ipm for x, y and z. Sometimes rpm is set another thousand or so slower.

[William]

Tim and Barney, thanks for the catch and clarification on the left vs right hand bit! That would have been bad.

Barney I'm surprised at your 12,000rpm, seems really fast but that's good to know. I'm using 3/4 baltic birch which I'm assuming is harder and may require me to slow down a bit.

Wes and Charlie, thanks for your numbers on the spiral ramp. You also answered another question, I wasn't sure if an 1/8 in bit was sufficiently smaller than 4mm to use that techniques.

As everything I do at this point has a big learning component, I'm leaning towards using the boring bit. I also have some short 4mm slots which I will pocket or profile with an 1/8in end mill so I'll get to practice with both bits.

Thanks for the advice,
William

[gtgmarine]

I approach drilling the same as Wes. The 1/8" up-cut works fine in anything from acrylic to oak to plywood.
If you do a test and find some tear out at the top of the material then start the holes with a downcut bit but only go 1/8" deep then finish with the up-cut bit.
Good luck.

[Gary Campbell]

A bit of clarification here:
Spindle are "rated" at a certain RPM range. What is missing is that they are "full torque rated" at that range. Which means you will have less torque available at lower RPMs. Drilling usually requires a lot less torque than routing. So, in most cases there is more than enough torque to drill small holes right down to 3000 RPM. But in any case it is your job to ensure that the feeds and speeds are proper.

With that said, there will always be the one idiot that misconstrues my words and tries to run a 3" bit at 1000 rpm and blames me for his failure. Go for it Buddy! I love the smell of burnt up motor in the morning! Dont forget to post!

[Jim Becker]

What Gary said...I routinely use much lower RPM for simple drilling toolpaths, typically something like 5-6K RPM.

[William]

A bit of clarification here:
Spindle are "rated" at a certain RPM range. What is missing is that they are "full torque rated" at that range. Which means you will have less torque available at lower RPMs. Drilling usually requires a lot less torque than routing. So, in most cases there is more than enough torque to drill small holes right down to 3000 RPM. But in any case it is your job to ensure that the feeds and speeds are proper.

Perfect! Thanks Gary that clears up my miss-understanding.

[William]

I routinely use much lower RPM for simple drilling toolpaths, typically something like 5-6K RPM.

Thanks Jim. I'm assuming I should try on the lower end to be as close to regular drilling speeds as possible.

Any advice on what I should look out for to indicate I've got the wrong speed? Also can you recommend a good starting place for plunge rate?

Thanks,
William