TECH: How I drilled my dropped axle

There are at least 5,467,523 ways to drill an axle. I thought I would share how I did mine.

Is it tech week yet???

I started with a Chassis Engineering 4" dropped axle (basically a heavy '32 axle). I did this all with common shop tools. Nothing special here. No mill, no crazy expensive bits or hole saws, just common stuff you can get at your local hardware store... Well, except the axle of course.

Tools and such...

* Dropped axle of choice
* Stand-up drill press (heavy duty would be best)
* Oil can of some kind and your favorite cutting oil
* Plywood or table to allow the axle to sit flat, or some kind of clamping system
* hammer and center punch (or a strong auto-punch)
* starting drill bit, 1/8" or so, but I wouldn't go smaller (breaking it off in the web would suck)
* hole saw with pilot bit
* more oil
* clamps of some kind to hold the axle
* heavy template paper and something to make accurate cuts with
* a small square
* did I mention you will need oil??
* small flexible ruler
* long flexible ruler (36" ought to do it, unless you have a later axle)
* fine felt tip pen
* deburring tool
* half round file (or drum sander and die grinder)
* 1" masking tape
* your favorite safety gear (if you care)
* patience
* music?? (speed metal probably not the best choice for this project)
* cold beverage of some kind helps

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***SAFETY NOTE!***

This is a forged axle, as were the original Ford axles, NOT a cast axle. If you're going to drill an axle and you're not sure how it's constructed, you will want to consult the manufacturer. I'm not going into the argument as to why or what type of axle should be drilled. There are other threads for this. Do your research first!
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So... Here goes.

The first thing was to decide how many holes, what size, and what the spacing will be. It's a little bit of a guessing game, but do your research based on what axle you have. Doing the math based on usable webbing area, I chose 15 holes at 2-1/4" on-center starting from the center and fanning out the length of the web.

Finding the center of the web is sort of tricky because of the shape of the cross section. There is no place to really measure from that is an absolute perfect edge. I made a guide based on what I saw another HAMBer do and applied. I used some sheetmetal template paper that I had. It's basically heavy construction paper. You could also transfer this templaye to a wood or plastic material to get real accurate, but keep in mind that the hole saw will "walk" slightly anyway, so there's only so much you can do unless you decide to do this with a mill, or something more accurate.

The template... It's very important that the knife be pink or it won't work right.



I folded the paper in half so I could get it perfectly symmetrical and opened it up from time to time to check the fit. Just kept trimming until I got the right fit. The fold line becomes the center line, so it's important that it be a nice, vivid fold.







Next I taped a washer to the bottom to keep the bottom edge from folding under as I ran it down the axle web. This edge must stay true or your center line will be all over the place.





Then I flipped it over and drew the center line



Check the fit and measure if you're not sure, just to be safe



Next the center line was marked on the axle. I decided to use a good sticky masking tape instead of blue Dykem spray because I had it, but the spray could be used as well.





Draw the line!





At this point, it's a good idea to check the line to make sure it really is on center. Run the template over the line to check it. Flip it around just to make sure you've been consistant. Make adjustments to the template and/or line, if needed. You only get ONE SHOT at this. Better to screw it up and fix it now.

The most difficult part of this whole thing is laying out the center marks for each hole. You want them in the center of the web, and you want them equally spaced. Obviously if you have an odd number, you want to start at the center. So how on EARTH do you find the center of a curved axle that basically has very little to referance from? Guess?? Hmm... There's a bunch of ways, but I'll show you how I found mine.

I used the plywood table top to draw and trace all the geometry on. I used the inner-most perch/wishbone holes that straddle the beam that was going to be drilled. First I found the center of the holes and measured down to the table and marked it.







Use a straight edge/ruler/yard stick, draw a line between the to hole centers and find the center of the line.



Use a square to transfer the center to the axle

 

This is where the flexible measuring stick comes in handy. After transferring the mark to the axle (again using some real sticky masking tape) it was easy to check the mark.





So why didn't I do this first? Because I needed a line to transfer the mark up and over the top using the square.



Okay! Now there's a starting place. The marks can be setup for the centers of each hole.

Here's the mark.



I used a small flexible ruler to layout the holes center to center.



I just happened to have a washer that was 1" in diameter so I used it to trace the holes and check my layout.



Now reality sets in. Check EVERYTHING! Make adjustments! No going back now! It's hammer and punch time!



Check the layout again to be safe and transfer the centers to the axle webbing.



Peel the tape and your centers will be obvious

 

Time to start drilling holes. Set the drill press up with a sturdy work surface and a way to secure the axle. Get your oil handy and put your starting bit in...





Drill holes at each center mark



Once this is done it's time for the REAL holes!!! No going back unless you're one talented welder and capable of blending welds back into that surface finish!

I used a standard 1" hole saw intended for metal to do this. Nothing special. Although the web is real thick, it's still only steel. As long as the speed is correct (the manufacturer recommended 235, for cast iron I ran it at 230) and the saw is being oiled constantly, it will break through in no time!

***NOTE ABOUT HOLE SAWS!*** They have a tendancy to "walk" a little bit on first plunge. GO SLOW! Make sure it's tracking on-center or the holes will be off-center and you will be sad.





OIL OIL OIL OIL OIL!!!! Keep that oil flowing or you will burn it up and go through hole saws like crazy. Oil is much cheaper than hole saws. I used only ONE HOLE SAW and plunged each hole in less than 2-minutes each. That makes for some quick work and the hole saw is still in great shape!

So now things are lookin' good!!

 

So now it's almost done! Time to just clean up the holes!



A half-round file could be used for this if you don't have a die grinder, but I had a die-grinder so I took advantage of it. First I used a round carbide cutter and cleaned up the hole...



Then switched to a small sanding drum



Then finished off the edges with a deburring tool.



A little more time could be spent to polish up the bores, but here's the result of the first go-around.



And here's the finished product. Ready for prep and paint!



Thanks for reading!! Hope it helps someone drill their axle!!

 

Fucking genius bro!!! I definitely would enter this tech on the next "tech week".
I love when you post your HOW TO'S!!!

Keep it up bro, i love this shit!!

Ian

 

Awesome thanks

 

I've been wanting to do mine, and now I will. Thanks Scott!

 

Setting up the job correctly makes for an excellent results.

 

Nice work!

 

That was an excellent bit of Tech dear sir! and its' pretty obvious that you are a hand model.
I've drilled a few axles over the years for my self & others I would say you did an awesome job & expalined it even better! Thank you for taking the time to share with us.

Hitler Bad....Scootermcrad HAMB TECH GOOD!!

Sincerely,
Cheatercarl

 

Nice work, just out of curiosity did you wieght it befor and after? people drill axles now because it looks bad ass but it would be interesting to see actualy how much wieght was saves by the early rodders.

 

Now that right there is real hot-rodding!!

Cheers,
Art R.

 

scooter...excellent!

can you elaborate on what specific oil was used when cutting?

 

Who care about weight savings... it looks badass!

 

Very cool

 

Nice job Scooter! It's crazy how something so simple is so complicated.

What hole saw did you use (brand, blade material, tpi)?

 

Nice work S.Co.T!!! You're a really talented builder with a drive to so shit right......and once. I have never drilled an axle but I did not think there was that much prep time going into one. Now that you went through all that I don't think there is a better way about doing it.

Perhaps except plotting that sucker out on in Cad and having a plotter print it out so you can layit over the axle for perfect measurements but who the hell would do that?

 

Cool stuff Scott. Always look forward to your posts.

 

Thanks for the nice words, everyone!

OH MAN! the second I first starting drilling I thought to myself "DAMN! I should have measured it! I guess I could weigh the slugs and add a little bit to that number...

I'm sure there's tons of high-tech, crazy, cutting oils specifically for certain things, but the 10w-40 that was hiding under the workbench worked just fine...



Chips and dip??

The hole saw is a 1" diameter, "Bi-Metal" hole saw, made by RIDGID. P/N 7002, (14 tooth/appx .224 TPI). Weird enough, it actually has a lifetime warranty as well. It's made in the USA and I bought it at Homeless Depot for $7.95, or something. The recommended cutting speed for mild steel is actually 350 RPM. I set it to 230. Cast iron was 235, so maybe that would have been a more realistic speed selection anyway.

Glad you guys liked the method. It's not 100% accurate, but the centers have to be within an 1/8" or so of "IDEAL" placement on the axle. Admittedly, one of the end holes got away from me too. Didn't catch it in time and it got off center. But then... I guess that just gives it more of a "hand made" look. Right? D'OH!

Seriously though, thanks for the compliments guys! It was fun! It's all in the setup and just paying attention and measuring over and over to make sure. The drilling part is basically mindless. 3-hours of getting everything setup and perfect with everything on hand and another hour of drilling and finishing off the holes, another HOUR just cleaning up all the oil and shavings. That why I did it on a piece of plywood, also. I just through it away when I was done.

 

Awesome article. Thanks. How about those split wishbones, are you drilling those as well?

 

Thanks!

Not going to drill the bones. I originally planned to, but because of where the final location of the spring ended up being (shackles attach to the bones themselves) I thought it would be wise to not drill them. If I were running the spring over the axle, I would have drilled them for sure.

 

Wise man!!

 

Not hard to calculate if the web thickness is know. Looks to be 3/8" or less but assuming 3/8", then 15 hole = the equivalent of a 1" diameter steel rod 5 5/8" long = 2.66 lbs per ft = 1.25 lbs. What's the actual web thickness?

Bob

 

1/2" web thickness and you would also have to take in account how much the hole saw orbited, how much I removed with the teeth, and how much I removed with the carbide bit and drum sander.

There was a thread done by Hotrodchassis and he weighed his axle before and after. I want to say he lost like 7 pounds, or something.

 

That came out awesome Scooter!

I bought a 1" holesaw for this purpose, but I didn't really think that hard about the prep procedure.

This is very helpful bro!
-Tyson

 

Good work.
I guess i dont drill any holes to the axle,but i think those methods of yours could be useful with something else too.

 

Very impressive my friend....

 

I'd believe the "something" rather than the 7 lbs! At a weight of ~ .111 lbs per hole, you'd only need about 63 1" holes in the web. Not callin' BS or anything, just sayin'--

Bob

 

Great job!

 

Yeah... not sure. Don't remember. I remember a 7 in there somewhere, for some reason. HAHA! You're right though. Not 7 pounds. (stupid) HAHA!

So that's just over 1-oz per hole.