Drilling straight through aluminum square tube

Dave: Since you are working with such a thin wall on your tubing, I would suggest trying a 1/4 inch end mill. You can chuck it up in your drill press since it is hardened, it may slip if it hangs, but if you get a center cutting one, it may resolve your problem. I would suggest a 4 flute end mill. If you can resolve the slop in the drill spindle, that would help. I drill a lot of 2 inch square tubing for trailer hitches. We use an annular cutter in a drill/mill. also, be sure you are not drilling thru the side where the seam is. It is hardened and thicker and will caouse drifting of your drill.

Sounds like you need to make a small fixture with a hardened drill bushing to guide things. A drill bushing for a 1/4" bit will be about

The fixture can be made of wood (hardwood) or metal (alum> I've worked with wood most of my life, but I'm not as experienced with

Can you purchase a bushing block to stabilize the drill bit prior to it hitting the tube?

How many holes are we talking about for the whole project? 100, a million, etc.

Joe - V#8013 - '86 VN750 - joe @ yunx .com Northern, NJ Ride a Motorcycle? Ask me about "The Ride"

Have unwanted music CDs or DVDs of any type? I can use them for our charity. eMail me privately for details. Donation receipts available.

Why not get ahold of the traffic department where you live, and ask them about buying a length of the pole they use to mount road signs? Look around your neighborhood and you'll notice most of the traffic signs are mounted on a piece of square tube that has holes every inch on all four sides. It may be worth it to you to make some adjustments in your project, materials, etc., to not have to drill all those holes. Ronnie

I'll bet that in addition to the drill chuck being junk, the table is not square with the spindle. If you did this in a bridgeport, it would work fine, so it should in a good drill press. THink about finding a good quality used drill press. An old delta, rockwell or some other, with a real chuck and a sqare table.

I really like ht esears drill presses, but I alway replace the chuck , usually with a taiwanese albrecht cl> I've worked with wood most of my life, but I'm not as experienced with

It's tough to get better than about +/- 0.015" accuracy when locating holes with a center punch and drill press. The slop in the quill bearings, chuck, table, and the starting point of the drill all add up pretty quick, as you found out.

If you need better accuracy than that, you'll have to build a jig and spot-drill each hole before going in with the bigger bit. Of find a cheap milling machine -- almost anything will have better rigidity and accuracy than what you're using now.

... the holes on both sides of the tubing have to be

... works for the top hole... There's no chance at

I must be missing something here. As I understand it, you need to have holes on opposite sides of the tube aligned. It seems obvious that you would just start at the top and continue through the other side. That it seems so obvious is why I think that I must be missing something. What is it?

The other part is how the series of holes down the length of the tube are aligned. There are 2 parts: how far apart they are and how closely they are to a straight line. You need to quantify both of these. E.g., they have to be 1" apart +- 1/32 and they need to be within a 1/32 of a line. A 1/32 was just an example, but your being a woodworker and not having much metalworking experience, 1/32 would be a realistic goal. If it needs to be much better than that, you'll probably need some help.

If 1/32 is good enough, a simple jig should get you there. Let us know and I'll go into it more.

Bob

BTW - you're in luck using aluminum - it works more like wood than it does steel.

On 29 Jan 2005 10:02:00 -0800, the inscrutable "Ronnie" spake:

Has anyone here EVER successfully purchased anything from "the city" or "the county"? All I've ever heard was "We're not set up to do that." Of course, I haven't tried the "bribing the lone workman with cold beverages ploy" yet, either.

======================================================== TANSTAAFL: There ain't no such thing as a free lunch.

snipped-for-privacy@aol.com wrote in news:1106983013.521991.220000 @z14g2000cwz.googlegroups.com:

If you're pretty good at wood working, this should be a pretty easy fix. Build a jig out of wood. Use a good quality hardwood board to make a base to which you will attach a fence. Next drill a 1/4" hole so that the center is precisely 3/8" from the fence, drill another that is spaced the same distance that you want the holes spaced on the tube., this hole will be used for a dowel pin that will determine the linear spacing of the holes. I would drill the holes first, then locate the fence by inserting a 1/4 inch pin in the holes then placing a 1/4" piece of flat stock between the pins and the fence. Instead of just using 3/8", I would measure the tubing and divide by two and locate the center of the hole at that dimension. Now clamp the jig to the table of the drill press. Locate the inside hole in line with the spindle of the drill press. The easiest way to do this is to insert the pin in the hole and then chuck on it with the drill chuck. Allow the jig to float to the center of the drill chuck. After you drill your first hole you are going to put a pin in the second hole and put the previously drilled hole over it to give you the linear spacing. Now drill the hole in the tube as follows: Locate the first hole by measuring, clamp the tube to the base and the fence. You should be able to use "Quick Clamps". Get a combination drill and countersink otherwise known as a center drill. Start the hole by drilling with this bit so that the countersink is just slightly larger than 1/4". Change bits to the 1/4" drill and drill through one side only. Now unclamp the tube and insert the pin in the hole located under the spindle. Flip the tube over putting the previously drilled hole over the pin. Repeat, drilling with the center drill and drill. If the mis-alignment is no good either adjust the jig or if being exactly in the center of the tube isn't very important, flip the tube and rotate it end for end. For the second and subsequent holes insert the second pin and use it to locate for precise spacing between holes. You need to minimize the drill runout if you can. If you can't, try using a small trepanning tool, or a two flute end mill instead of the drills.

Hope you can understand what I'm trying to describe. Good luck,

Dan

Purchase? No. But a lot of the time the workmen will give you small stuff for free. Ask in the yard, not the front office.

--RC "Sometimes history doesn't repeat itself. It just yells 'can't you remember anything I've told you?' and lets fly with a club. -- John W. Cambell Jr.

Purchased, no... But I've got friends there and I've acquired some decomissioned stuff for the price of a question...

Regards, Joe Agro, Jr.

My eBay:

Those are all good suggestions guys, thanks. As to the idea of the table being off square, that was the first thing I checked. So it wasn't that. But I did end up building a jig as suggested, and it helps a lot. But as a side note... I noticed Harbor Freight had it's little press on sale for a ridiculous 39.95 this week. I had absolutely no expectations, since I tried two presses that were more, with poor results. But I figured for $39.95, what did I have to lose. If it didn't work, I was going to give it to a friend... Well, guess what... Not only is it better quality then the two over $100 presses I tried, but it seems to drill straight. Go figure. Maybe I just had bad luck with the others.

Thanks for the help,

Dave

antenna

Since you work with wood, do you happen to have one of those self-centering dowling jigs? Like this:

Stan