No announcement yet.

1/2" holes in .120 304 ss

  • Filter
  • Time
  • Show
Clear All
new posts

  • 1/2" holes in .120 304 ss

    I've got some 500+ holes to put in .12 stainless and it occurs to be a 135 split point may not be the best way to go. Or maybe it is? Anyone wit advice?

  • #2
    Originally posted by Horst
    ......a 135 split point may not be the best way to go.
    Why do you say that? Are you thinking of an alternative method to drilling?

    Assuming the holes are to be drilled, rather than some other method e.g. punch, etc., I would think an aggressive approach is called for in a work hardening material like 304 SS. A 135 split point would be doing more cutting, and less rubbing than a 118 degree chisel point, or so I would think.

    I'm no expert; I'm just basing my comments on what I've perceived as the conventional wisdom. If I had doubts I'd probably make some trial holes.
    Lynn (Huntsville, AL)


    • #3
      304 Ss

      The trick to running 304 is to never let it heat up, even a little. What mainly generates heat is spindle speed and dull tools. I would run solid carbide drills with 2 straight flutes and flood coolant. You can probably get through the job with 5 or 10 of those. For spindle speed, experiment with 200 to 500 RPM. You will find that even at 200 or 300 RPM the drill will sink right through fairly quickly. You can use a Cobalt or coated twist drill, but the flanks right above the corner will wear quickly, causing heat and friction.
      Kansas City area


      • #4
        If it's flat sheet send it to a fab shop with a CNC punching machine or laser. It'll be easier and cheaper than trying to do it yourself.

        If you need to do it yourself use a Rotabroach type tool with coolant and low rpm. Keep in mind you need the low rpm!!!!!! Lower rpm than a drill press will do.

        Drilling stainless sheet with any form of conventional drill is difficult. The material is work hardened from the mill (unless you can buy fully annealed material).

        .120 material is thin for drilling. Even with a 135 point the drill tip is breaking through almost before the body is securely into the stock. This can cause grossly out of round holes, not to mention grabbing of the drill as the tip breaks through.


        • #5
          water jet or laser?


          • #6
            Can you stack pieces and secure them firmly?

            That is a double question, asking if your job will allow that and asking if that procedure will overcome some of the problems mentioned above.



            • #7
              Half inch holes in 1/8" 304 won't be fun at all. 500 of them is downright miserable. A drill bit is definitely not the best way to go regardless of the type. Punching, water jet, laser are all much better ideas even if you must pay for it.
              Free software for calculating bolt circles and similar: Click Here


              • #8
                Again with the 304 .... I've been machining the stuff forever and I don't get the paranoia about work hardening. Now 316 is another story. I'd go with the carbide ONLY to avoid having to touch up the drill from time to time. Don't need flood coolant either unless to keep both hands free. Just brush on a mix of water-soluble coolant. Just cut the speed down on the .500 and predrill first ... piece of cake.


                • #9
                  I'd go with a slow-spiral solid carbide screw-machine length drill.

                  No spotting, just blast it through.

                  On second thought, I ran the (free) Titex "TEC+CCS} software I have and it came up with this more-affordable solution:

                  Last edited by PixMan; 12-12-2011, 10:45 PM.


                  • #10
                    I haven't had to drill that many holes but when I need to drill thin SS I use a TIN coated Unibit and use a flap wheel to remove the burr on the back side.



                    • #11
                      Originally posted by tsmartin_98
                      I haven't had to drill that many holes but when I need to drill thin SS I use a TIN coated Unibit and use a flap wheel to remove the burr on the back side.

                      ts ; I've found that the best way to get rid of those huge S.S. exit burrs is to turn the piece over, set a butt stop so it can't grab and spin the workpiece, and then use a drill about 50% bigger than the drilled hole as one would use a countersink. The key is to go very very slow with the RPM and set a stop so you don't go too deep. Makes for nice, clean burr removal without the unsightly sanding marks.


                      • #12
                        You'll need a shallow point on the drill if your going to drilling that many in stainless.

                        118 degrees or more

                        all the best.markj


                        • #13
                          Like the others have said drilling them is not gonna be fun. But.... If drilling them is the way you have to go then Id use carbide.

                          Then you think, carbide? Im killing my pocket book. They arent cheap. YES!! I agree, they are expensive and to be honest I dont get the carbide drill thing?

                          Why are solid carbide drills made? It HAS to be for folks that resharpen them right? Cause everything after the cutting edge is just wasted carbide (and cost).

                          I bought a box of carbide tipped drill bits, they were a purchase in an auction lot so they were basically free. I looked at the bits and they were all concrete drill bits modified with a grind on the tip that was more like what you would see on a steel cutting drill bit, not a rock drilling bit.

                          The shop that I bought them from were using masonry (read very inexpensive) bits ground for use on steel.

                          I thought that was genius!! So I used some for a project. It was some highly polished 304 SS sheet that was just about impossible to drill through with some cobalt 135 bits. And I tried everything!! I use castrol moly-dee for tough SS. Proper rates. It was eating my drill bits. This mirror finished SS was impossible.

                          So I tried one of the bits that was in the lot, it was still pretty sharp, could have been better. But it was the correct size. I was just in failure mode and trying anything. I didnt care if I ate the bit, it was free for the most part and I was just curious.

                          I started on one hole (no moly-dee) and damn it the bit start cutting. This is after I was ready to use the plasma cutter and start free handing the holes, I was DONE burning holes through it with drill bits.

                          I was surprised, and still skeptical. I thought I hit a soft spot. Went to the next hole and the masonry bit ate it right on through. This was 22ga sheet so there wasnt really much drilling going on once it bit and popped through. I actually finished all the holes within a half hour even though I only wanted to see if the bit would cut, I was just playing around and got so jazzed that I was able to drill this bear of a metal. I was having fun drilling it after awhile, I couldnt stop. YEAH, I WAS happy to finally get through this stuff I just couldn't stop. I dont know why this mirror finish 304 is SO tough, it sucks!!!

                          But after that I will use re-sharpened masonry bits again. They are so inexpensive that its hard to believe they actually work, but they do. JR


                          • #14
                            The OP of this thread has not given us enough info to best answer his question.

                            If it's a for profit job in large sheets that's one thing. Punching, laser or maybe water jet are the obvious methods. Drilling is ridiculous.

                            If it's a home project like one hole in each of 500 pieces thats something else entirely.


                            • #15
                              Originally posted by JRouche

                              Why are solid carbide drills made? It HAS to be for folks that resharpen them right? Cause everything after the cutting edge is just wasted carbide (and cost).
                              Solid carbide drills, in general, aren't for home shops though I do have a couple.

                              Our older manual machines don't have the rigidity to take advantage of the features and benefits of modern solid carbide, coolant-fed four-margin drills of up to 70x diameter. Still, they can be used in home shops very effectively under the right conditions. Perhaps in tougher materials and with shorter length-to-diameter ratio drills they can make sense.

                              Solid carbide drills are certainly NOT a waste. Modern tool design uses the advantages of the higher rigidity of solid carbide to push drills at unbelievable speeds and feeds. This is productivity, and lowers cost-per-hole in huge numbers. The flutes can be polished to a mirror finish to aid in chip flow, and that's why no pecking is required. The points are incredibly strong, and the rigid structure means no spot drill is required.

                              I'd like to believe that solid carbide has taken the place of brazed carbide in metal-cutting applications because it actually works, not just because the tool grinders need the business.

                              Here's an example of how much more productive solid carbide can be over conventional drills. I can't find anything on brazed tip drills because so few people use them in machining of metals.

                              Last edited by PixMan; 12-14-2011, 08:31 AM.