How to with s/s?

Date 01-26-2007 23:30

Hello monsoon12, my suggestion would be to drill these holes either with a conventional radial arm drill, or to clamp a piece of steel to the surface of the tube and then use a mag drill with an annular cutter to make the holes. Once you're done,use a machinist's deburring tool to knock off the sharp edges, or a good quality countersink. Since you're talking about stainless, use the appropriate speeds and feeds as they are available and also a good quality cutting fluid designed for stainless. Good luck and regards, aevald

By billvanderhoof (****)

Date 01-26-2007 23:41

Drill? Can you move it to a drillpress? If not and the material is magnetic (some stainless isn't) a magnetic drill is nice. If nothing so far works drill a pilot hole 1/4 inch or so and then enlarge it perhaps in steps. You will need a substantial and slow turning drill, with a sharp bit. Resharpen often, stainless is tough. Take your time, it's faster in the end. If absolute perfection is required drill undersized and then ream to finished size.
Bill
Aevald beat me in I see we essentially agree.

By Molten Metal (**)

Date 01-27-2007 03:29 Edited 01-27-2007 04:33

Hey Monsoon12.I may actually be of help here for once.I set up drilling operations at Boeing here in L.B.While we dont use much stainless on the aircraft,it is used in the tooling sector of the assembly process.304 stainless,I would suggest using about a 140 degree drill point angle.You want to spend as little time drilling in stainless as possible to avoid work-hardening.This shallow angle will get the lip of the drill involved quickly.Try using a flat chisel point as this will have less heat build up.About 500to 750 rpm's be about right.Without knowing exactly what the pupose of these holes are,or you tollerance variables,I can't really give you to much more detail.There are several different tricks to s.s. drilling.Try about a 12-degree lip-relief angle.Any tool and cutter grinder worth his salt will be able to rattle off what you need pronto.The main thing though is to not stay in the hole along time.118-degree bits will just turn blue and fail and will make your matl. work harden a.s.a.p. Also,Titanium nitride coating(TiN) on the drill will have a lower coefficient of friction=less heat.Also you could get Cobalt drills as they are very hard.Slow rpm and pretty heavy feed rate is what you want.

By ssbn727 (*****)

Date 01-27-2007 03:51

Hi Monsoon12
Both good answers to your question!!!

Question... when you state 8X8X3/8 for the dimensions of the SS square tubing? just out of curiosity, what is the length of this tube, and how precise must the location & size tolerance of these holes be with respect to their layout? are the holes to be located on more than one surface of the tube, drilled completely thru both walls or are they staggered in some sort of pattern on each of the tube's surfaces or all drilled thru one surface only? How many holes per unit? Finally, is there the potential of fabricating more than one of these tubes?

Why do I ask these questions? Simply put, to cover all the bases in order to respond with the best possible solution for your situation, and at the same time offering as much efficiency into the response to your query. Please let us know more so that we can add to the already excellent suggestions if necessary.

Respectfully,
Henry

By DaveBoyer (*****)

Date 01-27-2007 04:11

With due respect to the already mentioned good points, stainless work hardens easily. To avoid this START with a perfectly sharp drill or cutter, Keep the speed low, Use sufficient feed pressure to keep making chips- the material work hardens when a dull cutter or a chip lodged under the cutter turns agains the work without actually cutting. Split point drillbits work the best. 135-140 degree point angle is a good idea. If drilling in steps, use a small 3/16 to 1/4" drill first, then go for full size. If You try to take out only a small ammount the drill is likely to snag in the hole. Don't even try without cutting oil.

By Molten Metal (**)

Date 01-27-2007 04:22 Edited 01-27-2007 04:35

If you are going to use a split-point as stated above,you should use a "modified" split point,often reffered to as (msp).Reason being,conventional split points have nuetral corners that result from splitting the point,and impede the escape of the chips.A M.S.P. drill will have a positive rake,as opposed to the conventional,which results in secondary positve cutting edges up to the chisel.They are also self-centering.With this configuration I would suggest a minus 5-degree rake across the web.This is used here with Titanium as it is so hard.I still prefer a flat chisel point to a split point myself for non-production ,one-off usage.P.S. You cant use a conventional split-point for sizes over 1/2" at all.It is not possible.F.Y.I. Hope this helps.

By monsoon12 (**)

Date 01-27-2007 13:43

Thank you all for your input it was very helpful.Ssbn727 to answer some of your questions ill do my best.The length of the tube is about 4ft.It will have 2 holes at center of tube with a 13/16th hole .The tolerances is really not a factor the hole is already over sized by i would say a 1/8 inch.In the shop we have a cnc drill machine.Its mostly set up for drilling all shapes an sizes of carbon steel.I beleive its called something like a beamliners.The operater had told me last time he tried to drill stainless with it he just burned the bits up.We do have access to mag drills or a plasma cutter hand operated.I will be looking into the suggestions that where given to me from all of you.An once again thanks so much,
monsoon12