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HSS Drill in 1144 "Stressproof" S/F

Nerdlinger

Stainless
Joined
Aug 10, 2013
Location
Chicago, IL
Just drilling on-center in a lathe. I burned up two 13/32" HSS drills going 1/2" deep in 1144 "stress proof" with Blaser Swiss Lube Oil flood. I started with my usual 80SFM @ F.005 but after 200 holes the outside of the lips burned up...the tip of the drill and half way up the lips looked good as new. I thought maybe the coolant wasn't getting in there so I switched to G83 peck cycle but to no avail...the same failure mode after the same number of holes.

Then I remembered that the 1144 was a bit harder than the stuff I usually work with and saw the recommended speed is more like 60SFM at about the same feed rate (~F.005,6,7...)

SO this is my question - seeing as how the outside of the drill was black/burned and the core was good I DO believe that 80SFM was just too fast and tomorrow I will slow it down and see what happens, but still can I get 500+ holes out of a regular HSS drill in 1144 or do I need to switch to carbide??

Thank you!
 
What brand, geometry, coating are you running? “HSS” could be a myriad of things, before going to carbide, maybe try a premium “HSS” with a decent coating, 135 deg split point TiN, or TiCN?
 
It is a non-coated 118 degree tip screw-machine length HSS drill from McMaster-Carr. I am spotting with a 90 degree carbide spot drill.
 
It is a non-coated 118 degree tip screw-machine length HSS drill from McMaster-Carr. I am spotting with a 90 degree carbide spot drill.

Corners are probably getting trashed when they're contacting the 90 degree spot without being supported/centered by the point.
Open up the spotter to a 140 degree. Might not help tool life but you'll probably see more even failure and give you a better idea whats going on.
 
If you have hundreds of holes to drill, go for a coolant-thru carbide, wind up the RPM's (if able), and get after it. I've done like 1,000 5/16" holes in 303, 1-1/4" deep, with a single Kennametal carbide coolant-thru drill.

I spot with the drill -- first .06" deep I go slow, then back off a little and dive in.

Regards.

Mike
 
Thanks for the help, everyone! They are Viking (bright) drills from McMaster.

The reason I am curious about this one application is because for a while I was on this "get the best drill possible" kick, but for more and more applications (just in my little world) I am finding a good-ole HSS drill has gotten the job done just fine with a life of thousands of 1-2X deep holes in soft 4140, 4340, 8620. IF I wanted to invest more money into this hole I would go get an Iscar Sumo-Cham and forget it, but I have just had such good luck with the HSS that I didn't want to give up on these $5 bargains just yet!

Regarding the spot drill, I have always done what Ghuring says in the catalog - when spotting for a carbide drill the spot needs to have a greater tip angle than the drill (so I use a 142 degree spot for a 140 degree carbide drill) and when spotting for a HSS drill the spot needs to have a smaller tip angle than the drill (so I use a 90 degree spot for a 118 degree HSS drill.) Also, FYI, I am only spotting to maybe 3/16" diameter...then drilling to 13/32" then coming back and chamfering.

Again, I didn't realize how much harder the 1144 was and according to Viking's site they recommend (as a broad rule of thumb) reducing SFM by 10 (from 80) for every 50 brinell hardness the steel is above 100. My material should be around 200 so I suppose I will try 60SFM and see what happens.
 
Thanks for the help, everyone! They are Viking (bright) drills from McMaster.

The reason I am curious about this one application is because for a while I was on this "get the best drill possible" kick, but for more and more applications (just in my little world) I am finding a good-ole HSS drill has gotten the job done just fine with a life of thousands of 1-2X deep holes in soft 4140, 4340, 8620. IF I wanted to invest more money into this hole I would go get an Iscar Sumo-Cham and forget it, but I have just had such good luck with the HSS that I didn't want to give up on these $5 bargains just yet!

Regarding the spot drill, I have always done what Ghuring says in the catalog - when spotting for a carbide drill the spot needs to have a greater tip angle than the drill (so I use a 142 degree spot for a 140 degree carbide drill) and when spotting for a HSS drill the spot needs to have a smaller tip angle than the drill (so I use a 90 degree spot for a 118 degree HSS drill.) Also, FYI, I am only spotting to maybe 3/16" diameter...then drilling to 13/32" then coming back and chamfering.

Again, I didn't realize how much harder the 1144 was and according to Viking's site they recommend (as a broad rule of thumb) reducing SFM by 10 (from 80) for every 50 brinell hardness the steel is above 100. My material should be around 200 so I suppose I will try 60SFM and see what happens.


Just FYI, if you can get them from any of your distributors, MAFord solid carbide twister drills with AlTiN coating can be had for only about $14, and will WAY outperform a HSS drill.
 
1144 stress proof/fatigue proof is a beautiful material to cut, but it doesn't like high sfpm. Once you find that sweet spot though it's almost as fun as cutting Delrin.
 
I'm surprised anybody uses HSS anymore, maybe in aluminum. Cobalt isn't that much more expensive and will outlast HSS significantly especially in Steels.

I haven't bought a HSS drill in 20 years, always Cobalt, and occasionally carbide.
 
I'm surprised anybody uses HSS anymore, maybe in aluminum. Cobalt isn't that much more expensive and will outlast HSS significantly especially in Steels.

I haven't bought a HSS drill in 20 years, always Cobalt, and occasionally carbide.

Yea we use HSS Drills all the time- if the job warrens Cobalt or Carbide we buy that otherwise use HSS. (unless we have that size in carbide or cobalt on hand)
 
PTD cobalt screw machine length drills are your friend.
Proper spot drill helps a lot too, and up the SFM, I drill stainless with these at 50-60sfm all day long. 1144 I'd start around 100sfm. For only 1/2"deep I wouldn't peck, chips break and come out of the hole real easy on their own with this stuff.
 
I've always been happy with the drills that show up from McMaster, they're usually PTD.

It is unbelievable to me that a professional would order a critical tool not knowing what brand they are getting.

(Why I dislike McMaster. Yes they will tell you if you ask, but I shouldn’t have to)
 
It is unbelievable to me that a professional would order a critical tool not knowing what brand they are getting.

“Oh, I just trust McMaster to send me what I need, they know best”... wow

Yeah but with McMaster you get to pay 2-3X more for that mystery drill than you would by going with a real tooling supplier that could sell you the right tool.
 
I tried everything with the Viking HSS drills but just couldn't get it past 200 holes. I'm almost done with the job so for now I just put a TiN-coated 135 degree split-point cobalt in there and so far so good. Will report back with the final number of holes on this job for reference.

The next time I run it I will look into what a better drill is (if not just the cobalt one) but for now I just want to get it done. Maybe the MAFord or Iscar SumoCham recommended above :scratchchin:

Fun fact - the same S/F with the 135 degree cobalt yielded a 55% Z-axis load when drilling while the 118 degree HSS yielded an 80% Z-axis load. (I imagine this has more to do with the tip angle/geometry than it does the material/coating but whatever...)
 








 
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