Pretty Easy Drum Drilling Jig

After gleaning through the archives and some links, here's my version of a brake drum drilling jig. I'll give a brief description, hopefully the pics will show what you need.


Start with the cereal box of your choice, open it up flat, should be at least 12"x12". Find the center and draw a line through it, take a protractor and mark every 20 degrees on both sides of the line using the same center point for all. Connect the marks through the center and you should have 18 equal segments. Using the same center, draw a 5 1/2" circle and divide it into 72 degree segments, this will be for the holes corresponding to your lugs, or the holes in your drums.
I used spray contact adhesive to glue the pattern to a 12"x12" piece of plywood. I then cut the plywood into a circle corresponding to the diameter of my drums.(I think it was 11") Drilled 1/2" holes for my "lugs", and squared my 20 degree marks across the edge of my plywood disc/jig.

 

I then bolted the jig between my hubs and transferred the dividing marks to the hubs.




I decided on three rows of 18 holes, staggering them slightly to cover more area of the drum.
The base for my drill press is pretty simple; two cleats screwed to a piece of plywood. spaced to keep the drums from moving. Centered under the drill bit and clamped down.

 

After center punching all of my marks, I went to work drilling all those holes! A drop of oil for each hole kept things cutting nicely. The stool was very helpful.

 

Here is the end result.

 

I'm on a learning curve with posting pics, perhaps Mr Focker will be kind enough to clean up my mess....OH Braaaad??

 

Very nice. But (forgive me) is there any actual benefit to all that precision?

 

Very cool!

Circumferencial symmetry and accuracy seems like a good idea. Uneven spacing could affect wheel balance, though it's probably negligible with holes that small and that close to the axle. Still, aethetics require a certain amount of accuracy ... at least it would for me.

 

It's only tape measure/eyeball precise. I doubt it will make any real difference at the speed they will be turning, but was hoping to avoid causing any balance issues. The machinists among us have end mills with dividing heads that are much more precise.

 

Yeah, the pattern seemed to make sense to me.

 

Looks great. How many drill bits did you go through? Did you have to clean up the contact surface of the drums.....burrs? I'm gonna do this one day. Thanks for the thread. Well done.

 

Submitted for admission to the Tech Index.

 

I only used one bit, recently sharpened (Drill Dr. is your friend ). I used gentle pressure and let the bit do the work. Start the hole just enough to hold a drop of oil, add a drop, and drill.
The inside of the drum was pretty burr free, but I did give it a buff with a flap wheel on my angle grinder.

 

Iron drums are soft metal and don't dull drill bits unless you are using the cheapest available. Nice work on drilling your drums.
-Donny

 

I've alway heard to not use oil when drilling on cast iron - the graphite in it is sufficient, and oil clogs the chips.

 

Most of my drilling is in steel, so I've gotten in the habit of using a drop or two. I didn't try drilling the drums dry. Clogging wasn't an issue in this case. I will keep that in mind when drilling cast iron in the future.

 

Thanks, "copy" and "paste" shouldn't be as tough as it was...

 

Wow, I'm honored!