What is a drum wrench you might say? No, nothing to do with music rather a tool for opening those uncomfortably shaped, hard on the hands caps on containers/drums in which you might purchase pool chlorine or bulk detergents or acid for example. The drum I have an occasional challenge with is shown here and there is a not too expensive tool for opening them readily available. Here's another.

Why buy one you might ask when you can purchase a flimsy, almost as uncomfortable plastic one? Hey, if I can make something to do the job, it doesn't cost me much more - not including my time - then I like to give it a go. How much time I put into designing and planning depends on the importance of the item and the target audience. This project - not vitally important - and the target audience - me. Therefore, I am kind of making it on the fly - no sketches (well one) and working without a net.

Step 1: A Bit Rusty . . . . .

Nothing like grabbing something out of the scrap bin - a piece of 2.5mm thick mild steel with a bit of surface rust.

A small angle grinder fitted with a flap wheel did the trick - both sides of course. The flap wheel, 105mm diameter and 80 Grit did the job although the rust was a bit deeper than it first looked so just a bit of pitting here and there.

My preference to using an abrasive flap wheel in cases like this is using a strip-it-disc. I think it does just as good a job, is less damaging to surfaces and edges and doesn't throw any sparks - they also last a long time.

Step 2: Some Numbers and Some Mathematics!

I know I said only one sketch so this is it.

To assist with seeing what I am doing - even with my glasses on - I use masking tape, 50mm wide to do my setting out on. Then just peel or scrape it off afterwards.

With an inner diameter of 62mm, I opted for a 30mm radius circle, using a centre punch mark not only for a future drill hole but to hold the point of a pair of compasses.

31mm radius plus 2mm gives me 33mm radius circle - a good clearance size for the 62mm inner circle on the sketch. 2mm you ask? Well if I use a 4mm drill - as you will see later - then when drilled on the circumference, gives me 2mm hanging outside the circle. Thus my 33mm radius.

Yep, I dragged out my old compass set from high school.

Step 3: Pin It, Clamp It, Drill It.

Having drilled a 3mm hole in the centre, I inverted the drill bit and used it to 'pin' the metal to my base board.

Then clamp the baseboard securely to the drill press table with the 4mm drill centre on the circumference of the circle. Secured in this way I could systematically drill a series of holes around the circle, close enough together - hopefully - so that the centre could be punched out.

Yep. made one mistake at the start - should have used 2 clamps to secure the base board to the table - a future picture shows what happened :-(

Been a while since I have used this method for drilling out a largish hole in steel - patience and steady drilling pressure is the key - don't rush.

Step 4: See the Light, Give It a Bash, Knock It Out.

You can see here the result of not securely clamping the baseboard.

Opening the vice to just a bit larger than the circle and using a ball pein hammer - striking near the drill holes and surely enough the remaining metal between the holes tears away.

Of course if your holes are not close enough together then you can use your drill is a 'mill' and just rock the plate side to side, enlarge the holes a bit closer to each other and that should do it. A bit of a hack but it works.

Step 5: More Manual Labour.

Well, there is only one thing to do at this stage. Break out the half round second cut file, choose some good music and rip into it. File away until you get down to the line.

Step 6: Set Out and Moooore Manual Labour

No fancy geometry tools here. Just sit the drum cap under the hole you have just filed out and mark the place of each of the nodes or tabs on the cap.

Small - 150mm (6 inch) file, on its edge and file away to the outer circle, Once again good music and patience.

Keep the edge you are filing close to the jaws of the vice to help minimise noisy vibrations.

If you are consistent with the depth of the groove you create and work right to the line then not much time is needed to get the wrench sitting down neatly, not tight, on the cap.

You may notice that I started by creating a full sized gap for a pair of cap lugs. This may seem visually logical - which it is, but a heck of a lot more work. So I opted for just creating a slot for each of the remaining 10 lugs. It would have been worth going back and marking the centre of each of the tabs. I initially marked the gap I would need for two tabs but when I opted to just file out individual tab gaps I should have changed my set out. Marking the centre of each of the remaining 10 tabs would have given me a much much more accurate file out. Lesson learnt!

Step 7: Get the Drum, Think About It, Mark It Out

All well and good that the wrench fits the cap!

But, sit the wrench in place on the drum and the obvious hits you between the eyes. Not unexpected.

So, without too many options, I chose the largest outer circle size I could, grabbed a pencil, used my finger gauge and marked an outer line for the wrench profile.

Step 8: Handle It

I picked some logical sizes out of thin air.

30mm wide for the handle, long enough to give a bit of leverage.

Using the outer edge of my masking tape roll to create a fillet or two and bingo - handle fully designed and resolved!

Step 9: Hmmm. Note to Self. Remember to Take Photographs

Ok, Ok, Ok, yeh I know I should have some images but I just started cutting, making sparks and lots of noise. A rush of blood to the head and 5 minutes later I was ready to start cleaning up with my mate the half round 2nd cut file.

Seriously though, I used my 105mm angle grinder with a 1mm metal cutting disc, some ear muffs, safety goggles, gloves and a face mask and before you know it the waste was trash on the driveway.

Step 10: File It . . . . Again, Check It Again . . . Paint It

File the straight edges - done

File the fillets - done

File around the circle - done.

Spend some time taking off square edges and the burrs around the inside of the circle - particularly the edges of the notches.

Grabbed the flap disc and angle grinder again and cleaned off the rest of the surface rust.

Oh yeh, and I drilled a 3.5mm hole with a 5mm countersink at the end of the handle. Need to hang it up somehow!

Shake shake shake . . . . . the spray can of cold galvanising paint and apply 2 light coats as per the overly detailed instructions on the can - waiting patiently between coats.

Step 11: Done and Dusted - Evaluate

A bit of paint makes all the difference. A couple of coats of gloss black - sprayed, and we are done.

OK a bit of an evaluation.

music selection - pretty good
planning and preparation - adequate but a bit on the short side
material - does the job
the make: a bit rough and inaccurate in spots - well, many spots
aesthetics: black - always in fashion and well, how good looking can a wrench be?
function - it works.
what would I do differently if I was to make another one?
- perhaps start with a cleaner base metal
- do all the setting out before starting construction
- drop Abba from the playlist and add some Aussie Little River Band and The Eagles
- perhaps laminate some timber on each side of the handle . . . . mmmm . . maybe not
- aluminium instead of mild steel - not such a bad idea given it will live near the salt water pool

Only one thing left to do - clean the bench . . . later . . . .