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Miniature Hss Drill Feeds and Speeds

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  • #1

I am drilling a .156 hole in 303 SS. The drill I am using is a solid parabolic drill jobber length. I am drilling at 1000 rpms pecking .25 at a time and 1.675 deep. Carbide Depot said that the recommendations were 20-40 sfm and .006-.01 Feed. I am feeding at .0015 the problem I am having is a very long cycle time and I am wearing after just 30 pieces and then the hole goes oversized. I am using a Lico LNT51 with Fanuc Series 3ti-Model A controls. I was just hoping its something simple that im just not thinking of that would make the drills last much longer.

thank you in advance.

Mike

  • #2

At those parameters, 30 holes is a good production rate for HSS.

That peck depth of .250 is a lot for that size drill. I would cut that in half. RPM is is also high for 300 series SS. Try around 600-750 RPM.

To shorten your cycle time, go with carbide. Thru-coolant if you have it.

  • #3

drill hole oversize

I am drilling a .156 hole in 303 SS. The drill I am using is a solid parabolic drill jobber length. I am drilling at 1000 rpms pecking .25 at a time and 1.675 deep. Carbide Depot said that the recommendations were 20-40 sfm and .006-.01 Feed. I am feeding at .0015 the problem I am having is a very long cycle time and I am wearing after just 30 pieces and then the hole goes oversized. I am using a Lico LNT51 with Fanuc Series 3ti-Model A controls. I was just hoping its something simple that im just not thinking of that would make the drills last much longer.

thank you in advance.

Mike

.
most drill bits drill 1 to 3% oversize so 0.003" oversize would not only be expected but normal. some new drills drill oversize a less amount but that is not normally counted on. if you got tight tolerances then ream the hole. you also don't mention coolant use. most cutting tools if dry can develop a false cutting edge or material sticking to cutting edge influencing tolerance as it build up and breaks off.
.
as to drill bits lasting longer tool life of 60 minutes minimum cutting time is normal in 1018 steel but with stainless a shorter tool life would be expected and normal. occasionally pecking more or shorter amounts helps with tool life but will increase cycle time.

  • #5

I havent worked much with stainless......when using HSS I usually peck 1/2 - 1x the diameter of the drill

  • #6

Increasing feed will make tool life longer... at least until the edge can handle it.

303 machines well, so increase feed !

adama

Diamond

Joined
Dec 28, 2004
Location
uk
  • #7

How you peck in stainless affects drill ife a fair bit too. You must not dwell for too long and you also must not just rip the tool out of the cut. Feed wise your at the lighter end and bumping it up a little would probaly not harm tool life can't see you doing 6 thou + though at that diameter! But 3 should be achievable depending on the 303, i would also try dropping the speed a bit as well as try increasing it a smidgen. It should soon become clear life time wise what you want to be running at.

Other thing is sharpen the bit . A sharp drill will drill better, cut cleaner and be far less inclined to cut oversize which is normally either caused by material build up on the cuting edge which gets worse as it gets blunt - rounded (see bit bellow about coolant) Other cause is corner chipping especially at break through in stainless.

What is your coolant like? IMHO stainless like aluminum benifits if its a bit on the oilier side of things. Too weak and it can really impact tool life especially if your chasing speed.

  • #8

Have a look at the OSG VPH-GDR drills.
Those things are beasts in stainless! And not a bad price either.
I use their speeds and feeds and the drills look brand new after a ton of holes, although I haven't used that size, I've mainly used the 1/2" drills.

  • #9

the company I work for refuses to provide a refractometer and I refuse to buy one so it can grow legs and walk away. Im using Trim E206 and im measuring about 8% of a 5 gallon bucket full of water to coolant

  • #10

the company I work for refuses to provide a refractometer and I refuse to buy one so it can grow legs and walk away. Im using Trim E206 and im measuring about 8% of a 5 gallon bucket full of water to coolant

Tell them that a $100 meter will save on that $1,500 barrel of coolant. ;)

farquharyesectood.blogspot.com

Source: https://www.practicalmachinist.com/vb/cnc-machining/hss-feeds-speeds-278405/

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