Need help on drilling large holes in 4140

bigjon0123 · Aug 3, 2018

Need help on drilling large holes in 4140: sovled

I’m trying to drill a 1.181 inch diameter hole in 3 inch thick piece of 4140. Currently I’m going center drill, then 3/8, then 1.181 spade drill doing a peck drill. My problem is when I’m running the 1.181 inch drill after about the first inch the chips get stuck in the hole and eventually jams up the drill stopping it from spinning. We can’t do through coolant since our cnc doesn’t support it.

The 1.181 inch drill is running with a feed of .5625, 340 rpm, and the peck depth is .3.

mhajicek · Aug 3, 2018

Try a shorter peck? What you really need is for coolant to blast the chips out, whether that's through tool or external. How much coolant pressure do you have?

You could always interpolate the hole after the pilot.

Guest · Aug 3, 2018

That is a strange looking feed number is that IPM?

Mtndew · Aug 3, 2018

Did you try a chip break cycle instead of a peck cycle to make the chips smaller?

Larry Dickman · Aug 3, 2018

how many do you need to do? Coolant thru would help tremendously. We've done it will a collar type adapter which worked great. Obviously doesn't work with the tool changer, though.

Guest · Aug 3, 2018

How about cutting the rpm, increasing the feed and making a thicker chip? A long stringy chip that peels out of the hole.

bigjon0123 · Aug 3, 2018

Dualkit said:
How about cutting the rpm, increasing the feed and making a thicker chip? A long stringy chip that peels out of the hole.

I’ll give it a shot.

bigjon0123 · Aug 3, 2018

Larry Dickman said:
how many do you need to do? Coolant thru would help tremendously. We've done it will a collar type adapter which worked great. Obviously doesn't work with the tool changer, though.

2 holes per part and lots of parts

bigjon0123 · Aug 3, 2018

Mtndew said:
Did you try a chip break cycle instead of a peck cycle to make the chips smaller?

I have not I’ll look into that thanks

bigjon0123 · Aug 3, 2018

mhajicek said:
Try a shorter peck? What you really need is for coolant to blast the chips out, whether that's through tool or external. How much coolant pressure do you have?

You could always interpolate the hole after the pilot.

Not really sure, the pump says it’s a 1/8 ho output, 50/60 cycle, 2850/3450 rpm.

bigjon0123 · Aug 3, 2018

Dualkit said:
That is a strange looking feed number is that IPM?

I believe so, I’m just reading off what the screen says.

Finegrain · Aug 3, 2018

Sounds like you are doing this in a VMC, right? In that case, and given that you have no thru coolant, I think your best shot is to get the swarf to snake out of the hole intact -- no chip break!! Once the chips break, and the drill body doesn't carry them out, it's going to be very difficult to get them to flush out of the hole with any sort of external coolant. Once you are 2" deep or so, I think those steel chips will just swim around in the hole instead of evacuating.

Maybe, if you can get one of your nozzles pointed straight down a few inches off to the side and very close to the workpiece surface, you can drill a ways, retract, move over so the hole is directly over the nozzle, hold it there for a few seconds, move back under the drill, drill some more, retract, move back under the nozzle, etc.

Regards.

Mike

Larry Dickman · Aug 3, 2018

bigjon0123 said:
2 holes per part and lots of parts

then I would definitely recommend a spade type insert drill w/ coolant thru. A little investment that'll pay for itself in no time.

michiganbuck · Aug 3, 2018

seems many are using spade drill nowadays.. what is wrong with HSS or carbide twist drills?

We tested a drill with a hump going down the flute face, then snubbed straight ant near the poimt end to become the chip curler..it was a kick-but drill for steel but I forgot who made it. holes were about 1" dia and perhap 3" deep.

HuFlungDung · Aug 3, 2018

Spade drills like to be pushed pretty hard. Perhaps .010"/rev would be normal, so 3.4ipm not .562ipm!

If operating in a vertical position, I think about all you can do is flood it, and don't stop for a peck because there will be a chip down there. if you get a decent feed on it, the flutes won't pack with the mush you're currently making.

Mud · Aug 3, 2018

Larry Dickman said:
how many do you need to do? Coolant thru would help tremendously. We've done it will a collar type adapter which worked great. Obviously doesn't work with the tool changer, though.

This - A coolant inducer on the drill will help, You can try adding air to the coolant to blow the chips up out of the hole like heavy mist coolant.

bigjon0123 · Aug 3, 2018

HuFlungDung said:
Spade drills like to be pushed pretty hard. Perhaps .010"/rev would be normal, so 3.4ipm not .562ipm!

If operating in a vertical position, I think about all you can do is flood it, and don't stop for a peck because there will be a chip down there. if you get a decent feed on it, the flutes won't pack with the mush you're currently making.

The most I can push my machine 1.3 after that it starts red lining but 1.3 and the no peck seem to be working.

White Lightning · Aug 3, 2018

Just wondering if you may drill a slightly bigger pilot drill to allow a faster feed . I have battled drilling bigger holes in gummy material with a underpowered machine. The drill pushes away with pressure and when it decided to drill it grabbs stalling the machine. Kind of like drilling brass. Leaving the impression that it grabbs on a chip but actually it's because the chip load ramps up when it decided to actually drill and increases chip load . I hope this makes sense. I go to a chip break cycle. The chip doesn't actually break with a small peck but allows the machine to push harder without stalling. Maybe .030 peck. Sounds small but keeps the spindle from stalling and the feed up to get the chip out.

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Need help on drilling large holes in 4140

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