Deep hole drilling

I am trying to drill a .380"(+.002/-0.00) dia. x 3.200" deep blind hole. The material is 7075 aluminum. I am running it on a Doosan mill. Any suggestions on deep hole drills?

Thanks!

I'm a big fan of the Guhring 6512 series for applications that aren't long enough to require an actual gun drill. Longer drills will require a pilot hole, and limited RPM until the drill is inside said pilot hole. At 9xD, you may be able to just start drilling into the part -just read the catalog instructions.

There's really not much to it if you are using quality tool holding, have halfway decent through spindle coolant, and can read the chart.

Guhring.com: Drill, 9.7mm 12xD, RT 100 U, Carbide, nano-FIREX, Coolant through - Size 9055250097000

That is the drill that I am using. I followed the chart and tried it without peck but it did not sound right and the chips were not evacuating the hole. Could this be a coolant pressure issue?

I actually had to program the drill to do small pecks with an rpm of 2200 and feed at 9 IPM but that takes 15 minutes

Holy hell bro!!!!! You're literally 10x too slow.

I'd run 1000 SFM, (10,000 RPM). And a feed of .0059" per revolution, per flute (112 IPM).

I understand that if you've never run those parameters before your eyes are prolly . But that's how those Drills run. The heavy feed will provide a heavy chip, that will literally blast out of the hole. Do NOT peck. Keep upping your feed until the chip comes out----assuming you're shooting 300psi or better. Check tool runout too.

R

15 minutes?! Must be a .001” peck. Are the chips coming out like powder?
You will need to make sure there is no runout in the drill. Start with a spot drill, leaving a spot with a diameter just a little bigger in diameter than the web thickness of your drill. If you have through coolant with decent pressure and flow, you should be able to jam through in one shot with no pecks. Maybe try a chip breaking cycle where the drill will “bump up” a few thousandths at certain intervals during the cycle. Super fine pecks will work against you by introducing chatter.

thanks! I will give this a try.

litlerob1 said:

Holy hell bro!!!!! You're literally 10x too slow.

I understand that if you've never run those parameters before your eyes are prolly . But that's how those Drills run. The heavy feed will provide a heavy chip, that will literally blast out of the hole. Do NOT peck. Keep upping your feed until the chip comes out----assuming you're shooting 300psi or better. Check tool runout too.

R

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so true, a bunch of years ago I had a ton of parts to drill .375 and .5 dia holes in, +.003 -0.001 and they wanted a 63 or better finish about 2.5 deep
Called the garr guy here in the valley he sent 2 out with feeds and speeds. Im like I aint running this fast there $250 and $350 drills. he said run them like I said if they break I will buy you new ones. that was over 10 years ago. still use them from time to time same ones. if I recall the feed was like 45IPM at 3500 RPMS they were 3 flute NO thru spindle coolant. found it best to peck 2 times. I was really impressed. Chips come off that thing huge and you dont even hear it cut. just chips flying everywhere. cool thing is it eliminated a center operation , and a reaming operation plus slow drilling on 50+ holes per part thats adds up to a ton of time

Spruewell said:

15 minutes?! Must be a .001” peck. Are the chips coming out like powder?
You will need to make sure there is no runout in the drill. Start with a spot drill, leaving a spot with a diameter just a little bigger in diameter than the web thickness of your drill. If you have through coolant with decent pressure and flow, you should be able to jam through in one shot with no pecks. Maybe try a chip breaking cycle where the drill will “bump up” a few thousandths at certain intervals during the cycle. Super fine pecks will work against you by introducing chatter.

Click to expand...

9 ipm feed at roughly 3" depth thats 20 seconds and with pecking maybe 1 minute ? full peck usually set for dia of drill or .38 peck roughly 8 pecks
.....if rapids when pecking are over 200 ipm each peck non drilling maybe 1 second ? so 20 seconds drilling and 8 seconds for pecking thats about 30 seconds per hole.
.
not sure how it would take 15 minutes a hole unless that time for many holes. with aluminum coolant usually needed to prevent chips sticking to flutes. long stringy chips wrapping around drill bit can be a problem with certain alloys that like to do that