drill chips

[mielke]

I am looking for a reference of different types of chips produced by drilling with a cnc mill. specifically what kind of chips are desireable or indesireable and what one can change (speed/feed/coolant??) to go from an indesireable chip to a desireable chip.

Ive tried doing a quick google search but didn't find what i was looking for. wondering if anyone knows a good reference website or can give me a few pointers for a novice.

 

[looslib]

More information from you would help.
What material are you drilling?
What tool material are you using?
What diameter drill?
How deep is the hole?



"Wildfires are dangerous, hard to control, and economically catastrophic."

Ben Loosli

 

[CastMetal]

A lot of what a desirable chip is(size, color, formation) is dependent upon the material being machined. I would check a Machinery's Handbook for generic speeds and feeds.

 

[mielke]

right now im drilling into 304SS with 5/8" deep holes 1/4"-5/8" diameter. but im more interested in general rules of thumb to watch for from chips. (if there are any)

 

[ProgressiveRacing]

Chip length and form is as much a function of feed (in/rev) as it is anything else, though drill geometry plays a role as well. You could simply increase feed and produce shorter chips, with better chip control – but at a reduction in tool life. As with anything else, there's always a point of diminishing returns but your goal is always: produce a hole within production limits at the lowest cost per hole.

What I would be even more concerned with is drill wear and built-up-edge. Drill wear diagnosis is covered in most "tech" sections of manufacturer catalogs. Try OSG Sossner, Mitsubishi and Guhring as a few examples.

As for starting points, use median values (SFM & in/rev) from the drill's manufacturer. If you don't know the manufacturer and are using a cobalt drill, start at 30 SFM and .004 in/rev and adjust from there.

The Manufacturing Reliquary

http://cmailco.wordpress.com/

 

[Troy2601]

In my opinion your chips should be blue and breaking cleanly, stringy chips are usally due to dull drills or improper speeds and feeds

 

[mrainey]

Some (stringy) chip control problems that come to mind include:

The chips damage the workpiece.

The chips wrap around the tool or toolholder and interfere with the toolchanger.

The chips jam the chip conveyor.

The coolant is blocked from reaching the tool tip.

The tool tip is damaged by recutting of chips or rapiding into chips (CNC deep hole cycle).


In general, more drilling problems arise from underfeeding than from overfeeding.


Software For Metalworking

http://closetolerancesoftware.com

 

[MikeHalloran]

If you want to screw around on some scrap, start with the SFPM recommended by the drill manufacturer, or what you can find in Machinery's Handbook, etc. Do actually calculate it. Even experienced machinists tend to run drills way too slow. Drills are consumables; consume them.

Start with an arbitrary feedrate, and double it until the drill splits. Then use half that rate.


Long stringy chips are fun to produce with a hand drill, but on a CNC machine they'll jam the drill in the hole and break it, and/or form a birdsnest that will snag a fixture, pull the drill to the side, and break it, and/or ... you get the picture.

Short chips literally fly out of the hole, and don't foul the flutes.




Mike Halloran
Pembroke Pines, FL, USA