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Drilling more stainless: WOW cutting fluids!

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  • Drilling more stainless: WOW cutting fluids!

    I just decided to switch from using TapMagik as my primary cutting fluid to McMaster's generic "Lard Oil". I'm working on a production run of little doo-dads I've done many times in the past. This time it is with stainless. I set up to drill my 5.5mm thru-hole and encounter all sorts of problems. I drastically reduce speed, slightly increase speed---all to no effect. Sitting here discouraged with a number of work-hardened, ruined pieces, I decide to change back to TapMagik (ProTap). To my utter amazement, the stainless returns to drilling with little trouble. I guess the stuff IS worth $50/gallon! But really... what is going on? What exactly are "extreme pressure additives" or whatever it is that makes certain cutting fluids provide more than just "lubricity"? The final question I dare not ask given this experience... is there anything that works as well that is LESS expensive?!

  • #2
    The secret to stainless is never let the tool get dull, and never let the cutting edge rub.

    You need to keep the cutter pushed into the work or you'll end up work hardening it before making a chip.

    Other than that, Moly D (but it's expensive too).

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    • #3
      I use the same Tapmagic for drilling SS. Yes, it's good. Extensive too, but you don't need much.

      Pay attention to speeds -SS is a lot slower and more pressure than say mild.

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      • #4
        I have used every liquid I could find to help with SS drilling and tapping. The tapmagic stuff is ok. Better than most.

        But the REAL king for SS drilling and tapping is Moly-Dee. Buy it by the gallon and its not too expensive... That stuff makes it a pleasure to machine SS.. JR
        My old yahoo group. Bridgeport Mill Group

        https://groups.yahoo.com/neo/groups/...port_mill/info

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        • #5
          I guess the point for me was that there was no difference with the lard oil when single-point turning 304-SS (using HSS tooling). Drilling, on the other hand, was a totally different story! I'm guessing it is due to the action of the chisel (using 135-deg., split point, screw-machine length, HSS-Co.) that makes drilling so difficult with SS. What is actually going on from a lubrication standpoint which allows such increased machinability?
          Last edited by Arthur.Marks; 01-20-2012, 01:14 PM.

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          • #6
            Often it just about stopping buildup and keeping the temperature on the cutting edge down.

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            • #7
              IIRC, typical single point turning operations are usually considered light or medium duty, so even a typical lubricant will work. Drilling, boring, single point threading, etc are considered heavy duty operations and are benefited greatly by a EP lubricant. That's what I seem to recall from reading product brochures, but take it with a grain of salt.

              Honestly, the biggest thing you can do to help yourself out is to use a sharp tool and keep your feed up, just like Jim Shaper said. I'd rather stall the machine with too high of a feed when drilling then have too slow of a feed. As you found out, too slow of a feed will result in a ruined drill and a ruined part!

              I've drilled literally thousands of holes in 316 and 304 from sizes ranging from 3/4 down to whatever the tap drill size is for 2-56 and I did most of the smaller sizes dry and didn't have any trouble. The small sizes are a little tricky at first since too much pressure will just break the bit instead of stalling the machine but you'll get a feel for it pretty quick. I've also used sulfurized heavy cutting oil and tap-magic. I preferred the tap-magic. It made it much less onerous.

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              • #8
                Fasttrack, your comments on pressure reminds me of one other thing I learned in this experience. I recently acquired a lever tailstock. I was using it for the first time on this job. I now understand why there was both a lever tailstock and a "starwheel" tailstock made for this lathe. The latter has a multi-spoked hub like a drill press. While I always preferred the quick, direct feel of a lever feed, in this instance it was a negative. The starwheel tailstock has a rack and pinion for advancement. This allows an increase in force. I was literally leaning on the lever feed, and the bits were still advancing with inadequate pressure, galling and work hardening. 304 stainless is oddly gummy in comparison to plain steel, the SFM is way lower---it all adds up to needing comparatively more pressure on the advancement. That makes the lever feed a lot of work even with a 5.5mm bit!
                Last edited by Arthur.Marks; 01-20-2012, 02:21 PM.

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                • #9
                  Originally posted by Arthur.Marks
                  Fasttrack, your comments on pressure reminds me of one other thing I learned in this experience. I recently acquired a lever tailstock. I was using it for the first time on this job. I now understand why there was both a lever tailstock and a "starwheel" tailstock made for this lathe. The latter has a multi-spoked hub like a drill press. While I always preferred the quick, direct feel of a lever feed, in this instance it was a negative. The starwheel tailstock has a rack and pinion for advancement. This allows an increase in force. I was literally leaning on the lever feed, and the bits were still advancing with inadequate pressure, galling and work hardening. 304 stainless is oddly gummy in comparison to plain steel, the SFM is way lower---it all adds up to needing comparatively more pressure on the advancement. That makes the lever feed a lot of work even with a 5.5mm bit!
                  I've actually found that the pressure required to get a big bit cutting properly in the 300 series SS is enough to cause lever-locking tailstocks to slip. At first I thought that was what you meant, but you are talking about an actual lever acutated tailstock, right? I can see how it would be tough to generate the force required to keep the drill cutting.

                  Like you said, it is sort of "gummy" compared to mild steel. Where mild steel tends to chip pretty well, SS will create long, razor sharp ribbons. Extra care has to be taken in selecting/grinding a chip breaker or otherwise dealing with the situation.
                  Last edited by Fasttrack; 01-20-2012, 04:43 PM.

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                  • #10
                    drilling stainless

                    There is an English product called Rocol RTD in paste form that is exceptionally good for drilling stainless, assuming appropriate speeds and feeds and of course a sharp tool.
                    Very little is needed and should be used at the start of the cut like most others.
                    \Google it ITW Rocol North America
                    Sawing, drilling, broaching works for all.
                    Cheers, Paul Z

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                    • #11
                      75% triko, 25% ATF to stop it evaporating, stainless cuts like butter.
                      .

                      Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.



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                      • #12
                        Originally posted by Fasttrack
                        I've actually found that the pressure required to get a big bit cutting properly in the 300 series SS is enough to cause lever-locking tailstocks to slip. At first I thought that was what you meant, but you are talking about an actual lever acutated tailstock, right? I can see how it would be tough to generate the force required to keep the drill cutting.
                        Exactly what I had happen with my lathe. Drill 1" in, Measure hole, 1/2" deep. Hmmm. Tailstock moves back as far as the drill goes in!

                        I solved it by replacing the tiny little 1 1/2" wide cast iron clamp under the lathe ways with one made of 3/4" thick steel plate... 7" Wide! Also used my ulgyest carbide insert endmill to cut the recesses for the underways, giving it an awsomely bad surface finish with lots of grooves to let oil into and run outta the way.

                        I also turned myself a new cam for my tailstock with about 1/2 the eccentric motion, meaning I got 2x the leverage, and adjusted the exact engagement point some.

                        The idea of it being 7" wide was I got another huge bar, and if that plate alone did'nt do it, it extended behind the tailstock enough that I could mill this huge bar into the shape of my lathe ways, and I was gonna drill a hole through this bar and through the bottom clamp plate and put a bolt through em, So id have a backup 'wrench clamp' behind my tailstock to keep it from sliping.

                        Others here have suggested using CVT transmission fluid on the underways, Claiming it has addatives that under high pressure *increase* friction. My huge underplate has worked fine however.
                        Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.

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                        • #13
                          Originally posted by John Stevenson
                          75% triko, 25% ATF to stop it evaporating, stainless cuts like butter.
                          Where'd ya get your triko? I don't think it's sold anymore ....

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                          • #14
                            Further ruminations from drilling this stuff... Hmm, faster feed is not always the answer with SS, I am finding. I was feeding WAY too fast. The feed and pressure I settled on is not all that much. Slow, steady and even. Once I found that balance, my lever-advancing tailstock works beautifully in achieving this. As the depth increases, I've even found I can minutely slow the feed pressure to coarsen the pitch of the spiraling chip. Go faster, the chip doesn't have room to follow the drill flute and curls in on itself. That breaks the continuous chip, leads to more heat on the drill and possibility of galling. As I go deeper into the bore, I try and let up a little. The chip remains continuous in most cases.

                            Other point of note: It is actually detrimental to clear the drill from the work even in deep holes. I started this way, thinking it would be a chance to cool the drill and re-lubricate the point. I was careful not to dwell---but to change from feeding to reversing the drill in one, quick motion. All I've really found is a tendency to gall the split-point of the drill. Counterintuitively, the heat is also more pronounced when I drill in two passes.
                            Last edited by Arthur.Marks; 01-20-2012, 09:01 PM.

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                            • #15
                              Originally posted by Arthur.Marks
                              Slow, steady and even. Once I found that balance, my lever-advancing tailstock works beautifully in achieving this. As the depth increases, I've even found I can minutely slow the feed pressure to coarsen the pitch of the spiraling chip.
                              You found the sweet spot! I hear people complain about SS all the time, but it really isn't all that bad. Some alloys are worse than others, but once you get to know them, they are kind of nice. In fact, I prefer SS over mild steel. Once you get that chip flowing, you're golden. The way I generally approach SS drilling or turning is by rapidly increasing the feed up until I get a good chip and then I try to keep it steady.

                              When I talk about keeping the feed up, I often do this by feel. When drilling from the tailstock, you get a pretty go idea of what kind of pressure is required. In mild steel, I find a balance between forcing the bit and letting the bit do all the work. In SS, the feed may seem "slow", but I keep a much greater amount of pressure on the tool than in other materials. As you found, I don't back the tool out unless it's a small diameter bit.

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