[thinkless]

Hello all,
This is my first post on the site, so if I'm in the wrong forum let me know.

I work at an automotive company, and in going through some of the G-code for some of our parts I saw some feed rates that seemed on the low side. I am considering upping the feed rate on the 5-axis deep drilling operations with the goal of reducing cycle time, and potentially increasing tool life which has always been an issue for us.

Here are my current variables:
Feed Rate = F23.0 IPM
Spindle Speed = 4000RPM
Cutting Feed = 23.0IPM / 4000RPM = 0.00575 IPR (this seemed high to me given our hardness)
Tooling = 0.246” Twist Drill
Stock (material) = SAE J431 Gray Iron; Average BHN = 232 over a sample of 415 units; over a Range between 207-255BHN
Drilling Depths = ~9” maximum

I’d like to start by making a jump to variables like this:
Feed Rate = F30.0 IPM
Spindle Speed = 6500RPM
Cutting Feed = 30.0IPM / 6500RPM = 0.0046 IPR

My questions are:

1. Is this a good starting point?
2. Will using a spindle speed this high likely give heat issues for a deep drill?
3. Can I expect to see an increase in tool life when reducing the cutting feed?
4. What spindle speed starts to become too high for a drill bit such as this?

[Jim Dawson]

I would get some advice from your tooling supplier. I would think that a twist drill is not the right tool for this application. A gun drill with through high pressure coolant is typically used for deep hole drilling in a high production environment.