Trouble drilling stainless 316 with an End Mill CNC Lathe

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LukeGernon

Plastic

Joined

Sep 6, 2018

• Oct 24, 2018

• #1

Attempting to machine a 11mm hole flat bottomed to 42.5mm deep, with a 7mm hole through, I am pecking down attempting to clear the swarf as it build but cutters snap at about 35mm deep, any ideas?

This is a 16mm diameter turned piece on a CNC lathe.

 

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Larry Dickman

Titanium

Joined

Jan 30, 2014

Location

Temecula, Ca

• Oct 24, 2018

• #2

LukeGernon said:

any ideas?

Click to expand...

with the info you've given, no.

 

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Gobo

Titanium

Joined

Jun 4, 2013

Location

Oregon, USA

• Oct 24, 2018

• #3

Are you using a center cutting endmill?

 

Mtndew

Diamond

Joined

Jun 7, 2012

Location

Michigan

• Oct 24, 2018

• #4

You're using a cnc lathe, use a boring bar.

 

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LukeGernon

Plastic

Joined

Sep 6, 2018

• Oct 24, 2018

• #5

yes, 6 flute carbide vari-helix.

 

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LukeGernon

Plastic

Joined

Sep 6, 2018

• Oct 24, 2018

• #6

havent got a small enough bar. wish i did.

 

Finegrain

Diamond

Joined

Sep 6, 2007

Location

Seattle, Washington

• Oct 24, 2018

• #7

Predrill with a 10.5mm, highest tip angle you can find.

Sometimes when plunging an endmill it can "catch" on the sides of the hole and make a big mess since there is no back relief with an endmill. You can grind back the flutes on your endmill behind the tip to avoid this.

Regards.

Mike

 

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Gobo

Titanium

Joined

Jun 4, 2013

Location

Oregon, USA

• Oct 24, 2018

• #8

I just saw you had a 7mm thru hole. Can you circle mill it?

 

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LukeGernon

Plastic

Joined

Sep 6, 2018

• Oct 24, 2018

• #9

What do you mean by circle mill it, as in generate a hole?

 

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Booze Daily

Titanium

Joined

Sep 18, 2015

Location

Ohio

• Oct 24, 2018

• #10

Shallow peck with full retract to keep the chips from making a birdsnest and starving the tool of coolant.

 

Mtndew

Diamond

Joined

Jun 7, 2012

Location

Michigan

• Oct 24, 2018

• #11

LukeGernon said:

havent got a small enough bar. wish i did.

Click to expand...

Grind the end mill into a boring bar.
Relieve the hell out of it, get rid of the other 3 flutes and grind more relief.

 

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Guest

Guest

• Oct 24, 2018

• #12

How many? I would use a drill first then knock the bottom out with a 2 flute end mill.

 

charlie gary

Stainless

Joined

Oct 4, 2009

Location

near Seattle, Washington, USA

• Oct 24, 2018

• #13

LukeGernon said:

yes, 6 flute carbide vari-helix.

Click to expand...

More flutes equals less chip clearance.

 

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FredC

Diamond

Joined

Oct 29, 2010

Location

Dewees Texas

• Oct 24, 2018

• #14

Anyone still hand modify regular drills to flat bottom? I still do this and it is trouble free and I get consistent results. If I need really flat bottom I finish with a boring bar.

 

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jjxtrider

Aluminum

Joined

Mar 15, 2018

• Oct 24, 2018

• #15

Flat bottom Allied spade is what I use . Plunging endmill can be a crapshoot in SS ,316 being bad , not even the "L" alloy . Same as Fred with borebar if perfect finish needed .

 

litlerob1

Diamond

Joined

Nov 4, 2013

Location

Utah, USA

• Oct 24, 2018

• #16

Bottom line is, that isn't the right tool for the job.

Drill it closer to size. Get more Boring Bars. Use a 2 flute Endmill. Make a Boring Bar. Flat a regular Drill.

Don't keep trying to paint a house with Hammer.

R

 

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hanermo

Titanium

Joined

Sep 28, 2009

Location

barcelona, spain

• Oct 24, 2018

• #17

I fail to understand some of the issue.
Why not drill to 6.9 mm+, endmill semiflat, and finish with a boring bar.

You probably need a tiny boring bar for that depth, carbide, to get to the edge of the hole.
11 mm - 7 mm = 4 mm /2 = 2 mm == 8 mm boring bar 42 mm deep.

I have no idea if the finish can be done in one pass with boring.
My "feel" is 2 passes.
3 generic tools and 4 ops.
So what, no ?

 

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Gobo

Titanium

Joined

Jun 4, 2013

Location

Oregon, USA

• Oct 24, 2018

• #18

LukeGernon said:

What do you mean by circle mill it, as in generate a hole?

Click to expand...

Is your lathe a two axis, or do you have live tooling/

 

Coadster32

Aluminum

Joined

May 4, 2011

Location

Milford, Ct

• Oct 24, 2018

• #19

litlerob1 said:

Bottom line is, that isn't the right tool for the job.

Drill it closer to size. Get more Boring Bars. Use a 2 flute Endmill. Make a Boring Bar. Flat a regular Drill.

Don't keep trying to paint a house with Hammer.

R

Click to expand...

I agree with this point of view. The Post title says it clearly.

If I posted a thread called" Can't mill a hole with this drill", I'd get bashed pretty good.

 

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LukeGernon

Plastic

Joined

Sep 6, 2018

• Oct 25, 2018

• #20

Another issue with the micro-boring is that its 42.5mm deep by 11mm D, so most standard tooling does not reach this kind of depth, well from looking in my tooling catalogs anyways.