Cutting 6mm aluminum plate

J

JC99

Well-known member
I want to cut into my skid plate to enlarge a cut out that currently partly covers one oil screen bolt, everything else is accessible with the plate on for an oil change. Taking the skid plate off to remove this one bolt is getting tiresome as it’s fiddly with multiple screws/bolts etc. This is a reasonably common mod but I want to make sure I do it right and the actual method hasn’t been posted anywhere I could find, just the enlarged access hole shape. I have drills/dremels/orbital tool and angle grinder etc and I want to do this job with the plate on the bike preferably (seriously, it’s a pain in the ass to remove).

What’s the best way to do this in 6mm aluminum plate? My current thoughts are to use a drill to drill holes marking the corners/edges of the shape I want (I bought a 1/4” hardened metal bit today just in case) then a metal cutting blade on the orbital tool to connect the drill holes and finally a grinding bit on the dremel to smooth the edges. I think the extra cut I need to make is only about 1” by 1” but maybe a bit more.

Would that work? Would it be better to just use a cut off disc on the Dremel for everything? I don’t think the angle grinder would work for smaller length cuts etc.
 
Do you have enough room under the bike to even use a drill? How much clearance between the skid plate and the expensive stuff behind it? If you don't want to dismount the plate you might want to grab your wife's best cutting board and jam it behind the plate just in case.

I haven't had great luck with cutoff wheels or grinding bits on aluminum, but maybe that's just the ones I was using. They clogged up fast with the soft aluminum. I'd consider a hole saw for a nice clean shape, but a coping saw and file would work just as well if you resign yourself to dismounting and remounting the plate one last time.
 
Aluminium and grinding media usually don't play nice. It clogs up the grinding media and stops grinding in no time flat.

IMO drill a small hole aligned with where you want the clearance hole, then take the part off the bike and complete the job with a hole saw. Any reasonable method of making a "nice" hole is going to need clearance behind the part for the tool (e.g. saw blade, drill bit, file, etc) to do its job. It will be easier and less risky to do this with the part being cut, removed from the bike so as to not put expensive bike parts at risk.
 
Hmmm. Thanks for the advice about grinding wheels etc.

I have room to manoeuvre a drill as the hole enlargement I need to make is at the side of the skid plate, not underneath. Between the plate and any bike bits there’s a decent amount of space too so I'm not overly concerned that I'd do any damage with a drill. There’s enough space between the plate and bike parts at this enlargement point that I can actually get some to and fro movement with a saw blade too so I was thinking a jewellers saw might even work.

Taking the part off might be the easiest approach, this one last time though.
 
If you have a jigsaw and tons of room to work, you could shorten a jigsaw blade (grind it down on a belt/disc sander) so that it isn't long enough to contact the bike bits behind the plate. I'd still want to remove the plate to clean up the edges of the cut with a file, though.
 
This reminds me of that one time I was replacing door speakers with aftermarket and mounted the new expensive speaker to an adaptor plate only to realize the speaker wire required a larger hole in the adaptor to get through. Being tired/lazy I figured "I'll be careful and I have enough clearance behind the plate before hitting the speaker" and could enlarge the hole carefully with a drill without taking the speaker apart from the adaptor plate. 5 minutes later I was ordering a new speaker.
 
Hardwrkr13 said:
This reminds me of that one time I was replacing door speakers with aftermarket and mounted the new expensive speaker to an adaptor plate only to realize the speaker wire required a larger hole in the adaptor to get through. Being tired/lazy I figured "I'll be careful and I have enough clearance behind the plate before hitting the speaker" and could enlarge the hole carefully with a drill without taking the speaker apart from the adaptor plate. 5 minutes later I was ordering a new speaker.
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Yup.... I would bet removing the plate will actually save time in the long run.
 
Aluminum is pretty easy to cut, no overly fancy tools are required. Maybe give us a pick of the spot... For best results, once you mark up where to cut remove the plate before cutting. Drilling small holes and connecting them is likely the worst method.

Your cleanest method could be a simple metal cutting hole saw as it will make a round hole that you can easily clean up any edges. The trick may be how to keep it centred and prevent it from wondering around initially if you are cutting where there is already an off shaped hole. Easy if you can drill a pilot to centre or if you have a drill press.

They make carbide burrs for aluminum and they can be had pretty cheap. If you are widening an existing hole they will work BUT it can be difficult to keep them going where you want freehand unless you have the skills. Still an option. They are intended to work in a die grinder but if you have LOTS of free time a fast drill can work, it is even more awkward and a PITA.

Others mentioned a jig saw, it will also work with a metal cutting blade depending on the shape of the plate.

You have a Dremel, if you have a metal cutting wheel(s) you can trace out your route and work it around. I would create a grove and then just keep working deeper BUT you have to look over angles to make sure you can get things fully cut through.

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What is the finish, lots of these things are anodized and the edges where you cut out it won't be now, age will make this worse. Might look bad. If it is panted or you are going to paint it afterwards that is less of an issue. Masking tape over the cut area will help eliminate any marks made by the tools on the surface.
 
DragWing 3.jpgI made the aluminum rearsets shown here. As others has said it's very easy to work. I cut the pieces with a jig saw then cleaned them up with a file.
 
This is the plate. You can see the oil screen bolt through the largest cut out. Thats what I need to enlarge. Looks like raw aluminum but the description from the KTM powerparts catalogue says "hardened". Poor design as they only needed to change the cut out a little to save some grief.
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Aye. A hole saw isn't going to work. Drill another hole on the far side of where you want to cut out, then use a jigsaw with a small metal cutting blade to connect the existing opening to your new hole on each side, then use a file to clean up. I would do it off the bike, clamped in a vise.

Original designer failed.
 
On something like that, if you have a Dremel, you can use a carbide burr bit but run it slow or take small chunks out at a time to let the aluminum cool otherwise you end up with a ball of melted aluminum on your bit.

The alternative is to just use a file if you have the room to go back and forth. It should go pretty quick on aluminum.

Or a combination of the above.
 
Yes it is kind of a stupid design as they could have changed the "speed hole" locations to better accommodate service.

Cutting a for clearance will weaken the plate as the plate above it will be a lot narrower, but unless you actually use it as a skid plate (hit it hard) I doubt it will matter. I think the trick is to cut it for clearance and still have the lines flow so it does not look like you bodged it.

You could still cut it with a hole saw but then you will have some odd round hole in the top corner of that shape. The blue circle is roughly the access you need. The yellow cut would make it look more factory.

I see three options:
Cut out the full yellow and radius each corner with roughly the same radius of the original, drill those corners and cut with a jigsaw or Dremel--best looking.
Cut the access with just a hole saw and have an odd hole at the top left of the original shape--easiest.
Cut the hole and then just the yellow lines to blend into the original shape and forgo the top left extension.

For cutting, as it is hardened aluminum, for the jigsaw or hole saw use carbide ideally with lubrication, WD40 will work in a pinch. Cut it off the bike with it secured. Clean things up with a file.

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backmarkerducati said:
Yes it is kind of a stupid design as they could have changed the "speed hole" locations to better accommodate service.

Cutting a for clearance will weaken the plate as the plate above it will be a lot narrower, but unless you actually use it as a skid plate (hit it hard) I doubt it will matter. I think the trick is to cut it for clearance and still have the lines flow so it does not look like you bodged it.

You could still cut it with a hole saw but then you will have some odd round hole in the top corner of that shape. The blue circle is roughly the access you need. The yellow cut would make it look more factory.

I see three options:
Cut out the full yellow and radius each corner with roughly the same radius of the original, drill those corners and cut with a jigsaw or Dremel--best looking.
Cut the access with just a hole saw and have an odd hole at the top left of the original shape--easiest.
Cut the hole and then just the yellow lines to blend into the original shape and forgo the top left extension.

For cutting, as it is hardened aluminum, for the jigsaw or hole saw use carbide ideally with lubrication, WD40 will work in a pinch. Cut it off the bike with it secured. Clean things up with a file.

View attachment 77971
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Yellow looks good as it gives me some wiggle room when working. My days of bouncing my 1290 super adventure off babyhead rocks are probably behind me so I'm not too worried. The skid plate is more for deflecting kicked up crap these days.

You have all made my wife's day since I need my workbench to work on this off the bike. The workbench is currently covered in “stuff”. The “stuff” comes from clutter and disarray in the garage, that comes from storage issues. So now I'm ordering shelves, to rearrange the garage and tidy it up to get to the workbench.

Bastards. :p
 
Apply masking tape to the bottom of your jigsaw and you won't scratch the work.
 
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