PDA

View Full Version : Perforating 2" OD, .065 wall 6061-T6 tubing... Best method?



Royldean
06-11-2015, 11:56 AM
I've already got it secured in Vee blocks nice and rigid. I've got to put roughly 36 holes in around the circumference and length, largest holes being 3/8".

Should I:

a) plunge with a center cutting endmill
b) spot drill, drill a small pilot hole, then plunge with the endmill
c) spot drill, drill with a small pilot hole, finish with a 3/8" drill
d) spot drill, drill through with a 3/8" drill
e) just be a man and use the 3/8" drill (i'm afraid of walking)

"a" makes the most sense to me, but I'm wondering if the endmill will grab when breaking through and do naughty things.....

Willing to consider an "f" if there is a better way. All I've got is a rockwell mill and a clausing lathe....

Duffy
06-11-2015, 12:15 PM
Center drill all your holes and use a step drill.

Royldean
06-11-2015, 12:46 PM
Hmm... good idea. Really good idea. But can I get a step drill that goes to 3/8" that won't be long enough to drill through the opposite side? Searching now....

[edit] looks like I can... Thanks for the tip!

Rustybolt
06-11-2015, 01:01 PM
option A

CalM
06-11-2015, 01:02 PM
Watch for the "un-even" chamfer / drill through with the limited step depth on a step drill.

I'm in the "center pop, spot drill, then through drill" camp. I see no reason to use an endmill, unless that is all you have on hand. The spot drill doesn't even need to go all the way through the 065 wall, just give the 3/8th's drill a good start.

garagemark
06-11-2015, 02:00 PM
This is what I use:

http://www.homedepot.com/p/Kreg-3-8-in-High-Speed-Steel-Step-Drill-Bit-KJD/100401246

Center punch and drill.

Toolguy
06-11-2015, 02:37 PM
Best to use a 3/8 ball end mill. Just use it like a drill bit. Don't forget that endmills always drill a few thou. oversize. If you need it right on size, use a smaller ball endmill, then ream. Also, a solid carbide 2 straight flute drill works very nicely for that application.

mattthemuppet
06-11-2015, 02:46 PM
the plus side of using a step drill is also that you can deburr the outside edge of the hole if you're careful, plus they tend to leave less of a burr on the inside (drill exit) edge than do twist drills in thin material. Given that step drills are so short and rigid you shouldn't get any wandering.

edit: these are what I use. They haven't been used intensively but they have held up really well drilling in all kinds of material (other than stainless). Work well in both a drill press and a hand held drill
HF step drills (http://www.harborfreight.com/3-piece-titanium-nitride-coated-high-speed-steel-step-drills-91616.html)

Royldean
06-11-2015, 03:38 PM
The step drill can't really be used for a chamfer in this application, as the hole is in a curved surface. There is no real tolerance on the holes (.050 would be more than enough).

boslab
06-11-2015, 07:17 PM
I did have a success once with thin tube, I centre drilled then opened the hole to the pin diameter of a counterbore, oddly that was 3/8, it went through the tube quite well, didn't catch, not much burr,but I was just messing about to see what I could do with a counterbore on tube, inquisitive day!
Mark

mattthemuppet
06-11-2015, 07:41 PM
Good point Roy, didn't think of that!

CalM
06-11-2015, 10:59 PM
Good point Roy, didn't think of that!

It was mentioned in an earlier post ;-)

CalM
06-11-2015, 11:07 PM
I've already got it secured in Vee blocks nice and rigid. I've got to put roughly 36 holes in around the circumference and length, largest holes being 3/8".

Should I:

a) plunge with a center cutting endmill
b) spot drill, drill a small pilot hole, then plunge with the endmill
c) spot drill, drill with a small pilot hole, finish with a 3/8" drill
d) spot drill, drill through with a 3/8" drill
e) just be a man and use the 3/8" drill (i'm afraid of walking)

"a" makes the most sense to me, but I'm wondering if the endmill will grab when breaking through and do naughty things.....

Willing to consider an "f" if there is a better way. All I've got is a rockwell mill and a clausing lathe....

Here is a "tip" if you are drilling a series of holes "in line" down a tube.

Clamp a weighted arm to the work in such a way that the arm hangs down nearly to the floor, and the desired line of holes is "up".
With the work located by fixed Vee blocks, you can then move the work "down the line", knowing that the alignment of the holes will be maintained. (given an acceptable rough precision)

Just something I've done using an old lathe drive dog. 2 inch dogs might not be that common, but use your imagination.

That step drill from Home depot would be the cat's pajamas!

mattthemuppet
06-12-2015, 02:11 PM
It was mentioned in an earlier post ;-)

okay okay, so I wasn't thinking or reading :)

Forrest Addy
06-12-2015, 05:17 PM
Unibit or step drill similar to this:

http://www.ebay.com/itm/Lenox-30886-VB6-Vari-Bit-3-8-Inch-to-1-2-Inch-Step-Drill-Bit-with-1-4-Inch-Shank-/111507787759?pt=LH_DefaultDomain_0&hash=item19f661cfef

Nice round holes; quick, neat, and tidy. Get a set if you work with sheet metal and light plate.

CarlByrns
06-12-2015, 05:40 PM
edit: these are what I use. They haven't been used intensively but they have held up really well drilling in all kinds of material (other than stainless). Work well in both a drill press and a hand held drill
HF step drills (http://www.harborfreight.com/3-piece-titanium-nitride-coated-high-speed-steel-step-drills-91616.html)

Agreed. They work great.

garyhlucas
06-13-2015, 09:00 PM
When I owned a CNC knee mill I started using Screw Machine length drills because of the limited Z axis. Once I realized how nice and stiff they were, don't walk, and how infrequently I ever needed a deep hole I switched to them completely. That is what I would use, pop the holes in one step and move on.

wierdscience
06-14-2015, 11:00 AM
+1 for the screw machine drills,especially the aircraft split point type.Run them fast with a spot of lube (WD40) and they make nice round and clean holes.

Royldean
06-17-2015, 02:45 PM
I didn't get to read the final posts, but what I ended up doing wasn't any of the above mentioned.

I had bought a nice step drill with the intention of spot drilling and then using the step drill as mention in one of the first few posts. But as I was spot drilling the very first hole, I noticed realized that my spot drill was 3/8".... so I just plowed through. It's short, like a screw machine drill, and it handled the thin wall aluminum easily! So I've got a $40 step drill still in its packaging that will have to wait another day for it's time to shine....