Unlike drill press power feeds milling machine power feeds are independent of the spindle rotation. Once you determine what RPM you want to run multiply the RPM by the feed per revolution to get the feed rate in inches per minute or mm per minute. It is unlikely the machine speeds will correspond exactly to what you calculated so pick the speed just below what you calculated. Remember this: when you change the spindle speed you need to recalculate the feed rate.

I used to drill with the horizontal mill on occasion. It worked well except for the nuisance of calculating the feed rate.

You can also drill by hand feeding.

Try feeding the Z axis instead of the X axis.

It can be done. I recently finished drilling 814 holes of 3/32" diameter through 1/4" steel plate under power feed without a breakage. This was with the drill bit mounted in a chuck in the lathe spindle and the job (dividing head index plates) mounted to the lathe cross slide. Power feed was by the usual leadscrew, at a rate of about .003" per revolution and spindle speed of about 950rpm. I used a short stub drill bit sticking out of the chuck only about half an inch or so.

What feed rate are you using on your milling machine feed? Can you slow it down?

How much slop is there on your Z axis ways? Are the gibs snugged up, or can the job move about laterally while being drilled, leading to broken bits? Do you have the X and Y axes locked to stop movement there?

Edited By Hopper on 17/09/2017 07:18:24

Edited By Hopper on 17/09/2017 07:21:02

Sorry to rain on your parade but drilling on your mill is never going to be easy, most drilling operations require 'pecking' & that's what you cannot do.

Tony

It's a trap isn't it. You know perfectly well that G83 will peck and you are just waiting for a Newbie to say you are wrong so you can strike. Go on then, I'll bite…

"You're wrong"

If the drill chuck is mounted in the horizontal socket powered feed drilling could be carried out using the Y axis, but with such a large motor indicates an early machine that would not have high spindle speeds, especially on the horizontal spindle, hence much lower feed rates are required to avoid drill breakage.

The X axis could also be used for powered feed drilling if the head was turned 90 degrees, this may be the best method as usually on a universal mill vertical spindle speed is double that of the horizontal spindle.

Emgee

I suspect the reference to CNC arises from the comparison made by Jason to CNC canned cycles, although it doesn't deal with the complete story. For completeness:

G73 pecks by backing off a small amount (defined as a system parameter) every peck distance, specified in the command line. The intention is to break the chips but not clear them

G83 pecks and retracts clear of the hole on each peck distance, both breaking and clearing the chips

As to the original problem I suspect the answer will be in the feedrates. However, I wouldn't bother pilot drilling for a 6mm drill, I'd just go straight in. My vertical mill has quill feeds of 1.5, 3 and 6 thou per rev. But I don't use them for drilling as they're generally a bit slow and rather a faff to set up.

Andrew

IMO power feed drilling is only for mass production purposes

They figure out the best way of drilling a zillion holes automatically

But not practical for most hobby work which is mainly ad-hoc and bespoke work

so … the obvious answer is you need to peck the hole … but another thing to check is that the drill is truly perpendicular in X and Y to the workpiece and also the feed direction. Because only a slight misalignment will also cause the effect described.

A 6mm 3 flute drill is a real bargain at £34.40