Drill press speeds


#1

Ok, maybe more @switchpod bait here.

I am looking at drilling through some stainless steel with different drills (can you smell a new 80% build going on?).

I have been using the calculator at https://littlemachineshop.com/reference/cuttingspeeds.php#Drilling to put in my drill bit size (there are a few different sizes needed for this build). And just need a second set of eyes on the math.

For instance, I will be using a #9 drill bit. On the calculator, I used 50 FPM and a size of .196 inches (Grabbed from here https://littlemachineshop.com/reference/numberdrillsize.php) That gave me an RPM of 974.

Is that correct? I would have thought it to be a little faster than that.


#2


#3

Fish on!!!

Sfpm- surface feet per minute.
Mild steel-100
Tool steel-70
Cast iron-60
Aluminum-250
Brass-300+
Formula:
4xcutting speed\ diameter
( on a lathe the diameter is the work)
#9 drill bit= .196
4x250=1,000
1,000/.196=5,102.04082RPM
So yes 974rpm is a little on the slow side.
I realize that your machine doesn’t go that fast, so just go as fast as she will go.
Remember aluminum is gummy and can grab the cutting bit so no real heavy pressure on the lever. Let the bit do the cutting and use WD40 as cutting lubricant on aluminum.


#4

#5

Ok. so if I am following you…

SFPM of Stainless Steel is 30-50 (from what I can find on http://www.vikingdrill.com/viking-Drill-FeedandSpeed.php).

So lets assume 50.

4X50=200
200/.169=1020

Now for the next question… Since this is a drill press… same formula for mill and lathe?


#6

Stainless kinda sucks to work with.

Yes you can use that for the mill or the lathe, but remember on a lathe the diameter calculation use the diameter of the piece in the lathe.

Remember stainless is a little gummy ( depending on the type) it can grab the bit, so if you are drilling it and you want a certain depth make sure you have your stop set on your mill/ drill.


#7

Thanks @switchpod! I just recalculated all of my speeds and they were off a little. For speeds, I have one drill bit that is going to come in at 2010 RPM and I have a choice of 1850 RPM or 2260 RPM. Is it better to go with the slower speed than the upper speed?


#8

Yeah always go lower, and use cutting oil to help cool the cutting bit.


#9

Thanks. Yea that is one thing I have learned to appreciate… Cutting oil.


#10

@switchpod Thanks for the education! It definitely helped with my P320 80% video that I released today! I put up a chart in the video with the RPM speeds of the drill bits used for everyone.


#11

Right on Brother. I’m happy to help with what I can.
Today might be another 12 hour day for me, but I will make a effort to watch that video!


#12

No hurry… the video is going to be there for you whenever you have the time.


#13

Hope you don’t mind but I put a quick shout out to you in the video description.

I would like to thank switchpod (https://forum.full30.com/u/switchpod/) on the Full30 Forum for doing an excellent explanation of how to calculate drill speeds.