Drilling aluminum router plate

[Victor Robinson]

I need to drill a 1/2" hole in a Rockler router plate (to enable the use of the above-table bit adjustment on my Triton router).

I do have a drill press. Best bit for the job? I imagine a forstner is not the way to go... A hole saw, carbide-tipped?

[Joe Chritz]

Any twist drill (non-brad point) will do just fine. Slow the speed down from what you would use for wood.

Run it about 1500 RPM, use a center drill to start (or center punch) and drill away. You could dab on some wax to lube during the cut but for the thickness of the plate it really isn't necessary.

Joe

[Terry Welty]

Joe is correct. Especially use the center punch!! I didn't and hole was a fraction too close to the router base. I had to run the drill bit through the hole and the router base to allow the crank to go through. Works fine. You'll love the router and the above table bit change is sweet..... I really like how it automatically locks the router when it's raised above the table for bit changes.

[Lee Schierer]

I'm with Joe. Use a centering drill, a center punch or a center punch with a small diameter (3/32-1/8") through hole for the 1/2" drill tip to follow.

[Patrick Grady]

Twist drill bits can be tricky when working aluminum hole sizes above 1/4" due to biting and binding. Start with a pilot hole, use cutting fluids (water is better than nothing), and always clamp the work securely. Never hold the work, especially smaller pieces with sharp edges, with your bare hands. For a 1/2" hole in aluminum (not harder metals), I like Black and Decker's 'Bullet' bit (I think the 1/2" bit is #19111) ;it cuts a smooth safe hole like butter. I always find many uses for this bit which have justified the twelve dollar purchase price (mine is 14 years old and still cutting well).

[Bill Huber]

I agree with Joe......

I would measure for the hole 3 times, use a good sharp center punch and start with a 1/8 drill, then go to a 3/8 and then the 1/2. Don't use a lot of down force, just let the the bit cut and you will have a nice clean hole.

[Bruce Page]

...and clamp the aluminum plate down to your DP table - don't freehand it!
Personally, I would run it at ~ 500 RPM

[Floyd Mah]

Try one of the stepped drills from Harbor Freight. They're cheap and permit you to mill vs. drill the hole. The attack angle of the cutting edge is less aggressive than a twist drill. Drill the lead hole, see if it is centered and proceed to the next size. If you are off a bit, file the hole with a chain saw file to shift the center before enlarging it with the next size. Years ago, I drilled a Rockler aluminum plate as carefully as I could using a drill press and a progression of drills, but I still ended up with a messy plate. The other thing is, if you need a ring of holes that are equidistant from the router center, clamp the plate to the router and use a piece of wood or aluminum chucked into the router to scribe the radius via a guide hole.

I just measured a twist drill and a stepped drill. Comparing the cutting edge to the trailing edge at 60 degrees, there is a .005" difference in diameter at the 1/4" nominal diameter when comparing the twist drill to the stepped drill (0.246 to 0.233" twist vs. 0.245 to 0.240" stepped). This means that the stepped drill is less likely to bite into the plate and deflect it. Also at some point you have to create a countersink. The stepped drill will remove some of the metal if you are careful in your approach. Don't use a twist drill to countersink. Use a real countersink bit and clean the cutting edge frequently of aluminum that is welded to the bit. Hope this helps.

[John Coloccia]

I would drill a pilot and use a step drill to finish it off. Aluminum typically likes high speed and light pressure, by the way.

[John Coloccia]

Great minds think alike, Floyd.

[Bruce Page]

Aluminum typically likes high speed and light pressure, by the way.

That is true in a production environment. High speed and a flood of coolant is how it is done. I have plunge cut aluminum 1” deep with a 2” diameter hog mill at 40” a minute – in a production environment with production machinery.
When you are looking at those feed & speed charts on the web or in your Machinist Handbook they are talking Production environment with production machinery, not Joe-blows Taiwanese/Chinese drill press in a garage.
Aluminum will cut, mill & drill perfectly well at 500 – 600 RPM albeit a little slower, and it is less intimidating to the non-machinist.

[John Coloccia]

That is true in a production environment. High speed and a flood of coolant is how it is done. I have plunge cut aluminum 1” deep with a 2” diameter hog mill at 40” a minute – in a production environment with production machinery.
When you are looking at those feed & speed charts on the web or in your Machinist Handbook they are talking Production environment with production machinery, not Joe-blows Taiwanese/Chinese drill press in a garage.
Aluminum will cut, mill & drill perfectly well at 500 – 600 RPM albeit a little slower, and it is less intimidating to the non-machinist.

For the record, I don't usually post stuff based on "the web", although I do own the Machinist Handbook (which is around here somewhere). I'm simply speaking from my homebuilt aircraft building experience. Personally, the best holes I get are run at high speed and light pressure. If not in the drill press then I use an air drill that goes to 4000RPM. If I'm going through more than a thin sheet, I typically lubricate with BoeLube. Low RPMS and moderate pressure always give me a triangular hole. Anyhow, that's just my personal experience. That's not to discount anything you've said. I just wanted to clear up that this is all just based on my experience, and not some cut&paste from an authoritative source or (perish the thought) some random web site.

All that said, I'd have to agree that it probably just doesn't matter that much here and whatever speed/pressure is used will give a functional hole! :)

[Victor Robinson]

Thanks much y'all. I'm glad I asked. I've taken the opportunity to order a stepped drill bit (didn't have one and my twists are low-quality...been meaning to upgrade those eventually as well).

We'll see how it goes!

[Bruce Page]

Victor, just an FYI. The stepped drill, aka, "Unibit" will work fine but they are really designed for thin material and each "step" is around 1/8" in length. Assuming the router plate is the standard 1/4" thick you may still need to finish the hole with a twist drill.

[Victor Robinson]

Thanks Bruce. So you're saying I should upgrade my twist bits too? :p

[Floyd Mah]

As it turns out, Harbor Freight has a set, under $20, of three bits, one of which has quite deep cuts, at 3/8", in a diameter which goes to 1/2". It will work quite well. Don't forget to have a countersink bit also. John is correct that you get triangular holes with standard twist drills. I almost forgot that. By the way, all my experience is practical with whatever will fit in a one (no) car garage, so no airplanes. I'm really impressed that John made an airplane. I used to have a lot of experience with take-offs and landings, but that was in my job as an anesthesiologist before I retired.

(I checked and edited the info about the drill).

[John Coloccia]

I never completed them. When we moved back east, it made no sense to own an airplane anymore. When I lived in the California high desert, I could literally fly everyday anytime I wanted. Out here, it's just too difficult to line up free time with good weather, and it's much more expensive too. I ended up selling them. I don't know if I'm allowed to post a link to my website. It's not commercial, so I think it's OK.

ballofshame.com

Check out the rv-7 build log in particular if you're interested. I kind of started loosing interest in keeping the website going when I got to the wings, and was really losing interest in the website when I got to work on the Bearhawk.

[Bruce Page]

John is correct that you get triangular holes with standard twist drills. I almost forgot that.


Yikes!! Don't tell that to the thousands of machinists and craftsman that have used the lowly twist drill since 1863! OMG, how in the world did we build the Queen Mary, Space Shuttle, even the Model T, with triangular holes!?! :eek::eek:

Come on guys, be careful what you put out there.

Triangular holes are caused by two things: Plunging the drill bit through at an excessive feed rate or an improperly sharpened bit. Period.

BTW John, I helped a friend build an RV- 8A. Great fun!

[John Coloccia]

All I said is I get triangular holes with low RPMs and moderate pressure. :cool:

[John Coloccia]

BTW John, I helped a friend build an RV- 8A. Great fun!

It really is amazing how people are willing to help out just for an oppurtunity to be involved in a seemingly whacky endeavor! I've even had friends and neighbors buck rivets for me. Sure, they bend a bunch...and then they learn to drill them out :D

Has your friend's RV taken to the skies yet? Nose draggers are especially ugly sitting on the tarmac ;)

[Bruce Page]

He has. here’s his first rivet to first flight video. About 2:17 into it is the throttle body block I made for his engine. Bucked more than a few rivets too.
http://www.youtube.com/watch?v=8f9HXzZT1dE&playnext_from=TL&videos=Q75Y_aqLdXg

I’m not trying to bust anyone’s butt but for many years I made a living drilling round holes.. I get a little snarky when people espouse fiction for fact.

[Terry Welty]

A simple reasonably sharp twist bit worked fine on my router plate. I believe it was 3/8" thick... I went with low speed on the drill press... light pressure... cut like butter

[Floyd Mah]

This discussion about the shape of holes reminds of the time that a certain financial analyst/commentator by the name of Herb Greenberg complained in print that he felt poor after a laparoscopic surgery (appendectomy I think) and that it must have been the anesthesia. Of course I couldn't let that pass, so I emailed him, reminding him that although the incisions in his abdominal wall were each small, there were several, that the wounds also had depth as well. In addition, who knows the effects of burning your intestines with electrocautery, both physiologically and toxicity from the vapors generated, and also there is the effect of the gases used to insufflate the abdominal cavity. I suggested that conceptually, it was not too different from pulling a barbeque into your closet to cook a few hot dogs. I got a reply later saying that he got many replies to his comments from anesthesiologists and his problem was most likely due to trying to get active too early.

An apparently good result with a twist drill in sheet metal doesn't necessarily carry over to thicker material. A dull drill bit and heavy pressure can result in a deformed hole, but in my experience, drilling aluminum plate with a twist drill, with home shop equipment is likely to not give you the desired result, especially when you are hoping to create a platform for more precision work. Also, if I needed an accurate round hole in an aluminum plate, I would use a reamer on a mill for a final cut and not rely on a twist drill. There is no place on a twist drill beyond the shank where there is more than two points with drill to metal contact, so there is an inherent deficiency in the design.

Anyway, I just wanted to say that there are those who find that twist drills don't aways create perfect round holes in all materials, independent of the machinery and the operator.

[Rich Johnson]

Heck I just did that exact same thing with my Triton 3 1/2 TRA001 router and the Benchdog 1/4 aluminum plate. If you look at the plate that is presently on the router it has about .20% of the circle where the above table winder shaft goes through. I removed it from the router and set it on the Benchdog plate. Scratched the .20% of the circle onto the plate. Then found a template for a 1.2 inch circle. Aligned it up on the partial circle i scratched and presto I had my circle. I took a small punch and eyeballed the center of the circle and made an indentation for the tip of the drill bit.

Put a regular 1/2 inch bit in the a corded drill pulled the trigger full spead ahead and by hand drilled the hole. If I had a drill press I would of used that but hey what the heck.

Filed away the edges with a circular file. Installed the router in on the plate. Put the plate on the CI benchdog top. And stuck the winding handle in (after removing the spring) and whoooooolaaaa perfect. That baby cranks up and down and has 1/128 marks like a $300 router lift.

Dont get to hung up on the fomalities or my spelling for that matter.

Its not as complicated as it seems. And the way the crank sets on the router there is room for small misalignments.

[Terry Welty]

Rich hit the nail with the hammer... It ain't no big deal... and even if you screw up (like I did), it can be fixed. Just do it and start enjoying your router... It's a great machine.