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I think I can.. Well maybe I can..

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  • I think I can.. Well maybe I can..

    I've got a customer waving an order in front of me. Can I do this? I'm a metal salesman ( 20+) years but I'm trying to learn machining as a hobby for profit.

    500 pcs 304L SS .375x4.750x10.00 plate. One end rounded (4.750 DIA) TOL: +/- .010. No edge profile. Just deburred.

    I'll buy plate saw cut to 4.750X10.000. (doubtfull I can find 4.750 cf flat)

    If I buy a mill/drill ($1500?) and allow for $500 fixtures/mills, can I machine the rounded ends in 60-70 hrs. I'm a pretty quick learn, but learn is the operative word.

    I'll take any answers or advice from "your crazy as a s/house rat" to "sure you can" I got advice from this board about cutting and drilling small pcs of 4130 plate. I did it and the customer actually accepted them. But maybe this is a little too ambitious. I don't want to ruin $3000 worth of SS and lose a customer.

  • #2
    I am confused on how you are going to do it without cnc. You do know stainless is really bad to workharden. Meaning if a cutter or drill gets dull it hardens the part and heats the tool up to red hot. Just try sawing or drilling a stainless weld.

    I was thinking, gee he can just spin it on a lathe faceplate, but the 10 inch length kills that ideal.

    Easiest thing to do I think is find someone with a plasma cutter cnc table, wave money at them to cut a sheet up for you, stack the nearly clean pieces up for light cleaning with a file.
    I would not relate all this to customer if you want to pocket some money or he will go elsewhere next time.


    • #3
      Stan, Have a serious look at getting these laser cut with nitrogen from sheet stock. Very little finishing to do and that tolerance is easy to hit. Quick, fast and no outlay, just put your markup on and light the bar-B-Q

      If you are thinking about machining these be aware that 304 is a bitch to machine. Squint at it the wrong way and it work hardens. 303 is far better to handle.

      John S.

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


      • #4
        Actually, if it were me, I'd have a waterjet shop cut it. That would eliminate even the minor hardnening of a laser/plasma cut, and most setups can easily hold +/- .010".

        Have 'em knifed from whatever is the easiest size of 3/8" plate to get, and maybe have the shop tumble them for minor deburring as well. (Check for surface finish specs.)

        Doc's Machine. (Probably not what you expect.)


        • #5
          I'd use a punch press to cut to length and radius in one shot. It would involve a little bit of tool work though. As far as the width, I'd hope they could live with a sheared edge.
          Waterjet or laser would give nice edges.
          I get shivers thinking about trying to mill that radius on a small machine.


          • #6
            John has the best solution - laser cut the pieces. This is the fastest and neatest way to do it. It will cost you far less that the endmills you will destroy trying to machine it yourself. 304 Stainless is a bitch to work with because of its severe work hardening qualities.

            If you cannot find a shop that can Laser cut it I would then look for waterjet cutter with dynamic cut control - this is a special machine that tilts the cutting head for higher accuracy cutting in thicker materials. Water cutting will leave a minor bur and slightly distort the top edge.

            It would take months to machine these on a small mill-drill and a couple of weeks on a high horsepower CNC mill. Set up cost and machine time for a CNC machine would be a killer.

            The Laser cutting is the most effecient way to do it from an energy conservation standpoint, milling it is the most time consuming and far more expensive than Laser or Water Jet cutting.

            Don't even consider plasma - 304 cut this way is a bitch to mill.

            Having it punched out in a press would be the most expensive way to do it as custom tooling would be required - some large turret punches might be able to do it, but nibbling a semi-circle on the end of 304 stainless that thick would be a nightmare. IMHO this is the last resort way to approach the problem.


            • #7
              I'm with Doc Nickel, I'd go with the water jet. With the proper equipment, deflection isn't much of an issue any more. Either way, I'd say there would be a better profit in farming out the job.


              • #8
                Yeah...What Thrud said...

                Laser cutting will achieve a better tolerance than water jet...water jet leaves a dull sandblasted look (which I don't like)..laser cut will leave a dark color which can be buffed out...

                good luck,



                • #9
                  My waterjet guy has cut 6" stainless steel with very good quality surface finish and edge quality. Tolerance is easy to do if they go slow enough with the waterjet. The waterjet does not heat treat the edge and that feature becomes more important as the thickness of the parts increases. The nice thing about waterjet cutting is that you can stack up the material and cut 4-5 parts at once. You can get the plate sawed up in 4.75x 20.5 long pieces stack them up and have the waterjet guy cut only the radius on each end and then cut the stack in two. About 22 stacks to get 500 parts cut it all in one day. Waterjet charges by the inch of travel so you save money by having the plate cut to width and the stacks of 4-5 plates I mention here sawed in two pieces. A key is to make double sure the waterjet guy understands what is important. Have him cut a trial stack before cranking up on the whole order.


                  • #10
                    Laser cutting with Nitrogen will not discolour the edge or harden the edge surface. If oxygen is used then both will occur.
                    Nitrogen is a slightly higher cost process but saves on cleanup time. I have some 10mm large washers in the workshop that have benn laser cut, I'll post a pic later on.
                    From the sizes given of the part and knowing how fast a modern 3Kw laser can cut I guestimate about 1 minutes 40 sec to 2 minutes 20 sec per part.

                    John S.

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


                    • #11
                      Okay I give.. I live next to Chattanooga and have had plates and brackets made all over the place. I don't know of a nitrogen cutter or a waterjet in tennessee, much less chattanooga.

                      Do I live in a non-tech redneck city? I love new toys and surely would have looked up such a contraption.

                      I thought cnc-plasma was at the top of the chain.. I learn something every day it seems.

                      I was thinking of hooking up the cutting torch on a gantry off my cnc mill table, I got to make it pay for it's room and board somehow. (with a a-cloth curtain thank you)
                      I thought cnc flame-cutting would at least bring my lil shop into the 80's


                      • #12
                        Thanks for helping me dodge a bullet. Going to contract this one out to a waterjet shop I deal with. I'll have to find find another order to finance my mill/drill. Stan


                        • #13
                          Ibew, I'm pretty sure that I saw a TN company demo'ing waterjet cutting at a Huntsville, AL Tool & Machinery trade show 2 or 3 yrs ago. There's usually several Chattanooga Co.'s present at the shows here. But maybe this Co. was from up in the Nashville area. Don't remember now if this vendor was offering a service, or retailing the equipment. ...but it was fun to watch.
                          Lynn (Huntsville, AL)


                          • #14
                            <font face="Verdana, Arial" size="2">Originally posted by ibewgypsie:
                            Do I live in a non-tech redneck city?</font>

                            Why, yes you do as a matter of fact!

                            The Laser cutting without oxygen (they use argon or Helium up here for critical applications - Nitrogen can harden the metal under ideal conditions, hence the inert gas) is best. A jet of oxygen (often used) is emmitted from the Laser cutting head - this clears the vaporized material out of the kerf.


                            • #15
                              I would get RFQ (request for quoatation) from both a water jet shop and a laser cut and see which is less expensive. I have preference for water jet but IMHO. Please post back on the quotes!