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dneufell
02-07-2005, 08:19 PM
Hello All!...Thank you for letting me join
your group.May i ask a question? What is this best way to drill
sheetmetal (.020 thick copper-500 pc +.020 thick steel-500 pc) so it leaves minimal
or no burr? The job i am doing is(in a bridgeport) drilling
two .232 diameter holes that are .500 apart
in a round .810 diameter end cap(like a copper end cap for 1/2 water pipe). My problem is not deburring the outside. That is easy(i use a whirlybird). The problem is
the inside of the cap. The holes are very
close to the wall and tuff to get at. The parts get .0002 solder diped afterward. I have deburred with a small countersink
but have always had to beadblast inside the cap for the last little bit near the wall... Any sugestions? Thank you very much....Dean

gary hart
02-07-2005, 08:28 PM
Just a wild idea, no idea if it will work.
Howsbout a quick shot with a small oxidizing
flame form a oxy/acetylene torch.

wierdscience
02-07-2005, 08:29 PM
First,welcome aboard!

I have used HSS drill bits ground to look like brad point bits for wood.The theory is to let the spurs cut the od of the hole first.
I would also make up a slug to fit the inside of the caps so the cut is backed up.In thin copper and brass even steel they cut really nice holes.

If this is a regular job for you,would it be possible to make up a O-1 steel punch and die to punch the holes in a small arbor press?
You could make a punch and die set where the punch would fit up inside the cap and support the work while being punched.If kept nice and sharp that would make your best/quickest hole for the money,hope this helps.

torker
02-07-2005, 09:35 PM
Hello! I haven't tried this yet but I read somewhere that if you put a small bit of thin rag over the hole before you drill, it is supposed to leave a burr free hole in thin sheet stock.
Russ

matador
02-08-2005, 12:53 AM
dean,years ago i was given a quantity of short double ended drillbits.was told they were "panel drills",used to make 1/8th holes for pop rivets.they don't leave much of a burr,so might be worth a try.

------------------
Hans

speedy
02-08-2005, 01:27 AM
Dean, try drilling the pilot then useing a piece of soft cloth place it between the final size drill bit and the work and drill. I can guarantee that this method works on sheet metal and gives a clean burr-free hole. I have not used the method on copper so use a test piece first.
Can you set up in the lathe, drill undersize then bore outward so that any burr is easier to remove.

cheers, ken

WJHartson
02-08-2005, 02:07 AM
As weirdscience said, make a punch that punches from the inside to the outside it will be quicker than drilling and will leave holes in the same position everytime. Since you have to clean the parts prior to dipping have you though about a vibratory tumbler. They work great and will deburr, clean and polish all in one step.

Joe

Al Messer
02-08-2005, 09:18 AM
Two holes in each cap? Umm! Maybe mandrel on the inside with a brad point drill as previously suggested? May I inquire "why" or "what is the end result"?

drof34
02-08-2005, 09:47 AM
Sandwich the sheet metal between two pieces of wood or two pieces of thicker scrap metal and then drill thru it all.

Jim W.

DR
02-08-2005, 10:04 AM
Punch 'em. No question about it.

You've got a B'port that'll make the die, buy stock punches and make a holder.

You punch 5 pieces in the time it'd take to reposition the mill to do the second hole.

Michael Moore
02-08-2005, 10:22 AM
If you can find a unibit in the right size they work very well in sheet metal.

But it does sound like punching might be the way to go, especially on such thin stock.

cheers,
Michael

Paul Alciatore
02-08-2005, 12:13 PM
Nothing I have ever tried has ever left no burr. I find that the Unibits will do the best job on sheet metal. Best to back it up with a hard wood. That may be difficult inside a cap. Next best thing is a really sharp drill. Sharpness seems to matter more than the actual tip geometry, IMHO anyway.

I would try to do the drilling from the inside. That way, the burr will be on the outside and easy to remove with a quick dab on a countersink.

PS, if you do use the Unidrills, they will do an excellent job of deburring by lightly pressing the drilled hole against the next step. They apparently have a radius between steps and it makes an excellent edge. I set the depth stop to use the step to deburr the top while I drill and then flip it over and deburr the bottom in one quick motion. Makes nice holes in sheet metal. I don't know your tolerance for the job but 15/64" is only 2.4 thousanths oversize. Perhaps you can find a Unidrill with that size?

Paul A.

Forrest Addy
02-08-2005, 01:12 PM
Punch the hole from the inside. This puts the burr on the outside. It's thin copper. It'll only take 100 to 200 lb to punch it. You can use the BP as the punch press.

dneufell
02-08-2005, 11:30 PM
Hello All! The company i make these for use
to punch them but it distorts the cover. They want me to drill them for that reason. These are cases for small special instruments are placed in.(goverment)
I will try the different drill tips you guys have mentioned. The job is in the lathe
this week and should go in the mill next week. I will let you know what works best. Thank you....Dean

dneufell
02-08-2005, 11:32 PM
Hello All! The company i make these for use
to punch them but it distorts the cover. They want me to drill them for that reason. These are cases for small special instruments are placed in.(goverment)
I will try the different drill tips you guys have mentioned. The job is in the lathe
this week and should go in the mill next week. I will let you know what works best. Thank you....Dean