Ok, so I’m about to attempt a mold that has several perfectly round holes that I need to fill in. I’d like to not put anything permanent into the plug as it’s a stock part that I’d like to keep.
It’s a motorcycle heel guard, pretty much a perfectly flat piece of aluminum, with several holes in it. What could I use to plug them that would give me a nice finish on my mold?
Here’s a pic of one on ebay for better reference.
You can use several different products to fill in the holes.
Melt some bees wax or white candle wax into the holes, then use a metal tool, scrapper, or razor blade to level the wax to the part surface.
You could also use modeling clay ( an oil based clay that does not dry out). WalMart carries colored modeling clay for a couple dollars, and all good composite supply stores will sell the clay also.
Both of these will be able to clean off the original part once you are finished with the plug. I’m not sure about how to clean wax off a good part, but with modeling clay you just use a dry rag and wipe it off. I have found that to be the easiest way to remove clay.
Yes, you will not be able to make the mold with those holes still there. You will not be able to mold it with holes already there.
You will have to drill the holes after making the part…
Werks, I wasn’t talking about making a mold with holes already there. I’m trying to plug up the holes on the tip of the heel guard and have one smooth piece. Obviously I would have to drill any other holes later.
or, if you can’t get a perfectly flat piece, if you fill the holes with clay, up to the first surface side, and leave a slight bowl, you might be able to create dimples. That way if you can’t get a perfectly smooth AND glossy surface in your mold, the dimples will create the illusion that you meant to have the dimples/etc there.
…or the dimples will be drill bit starting locations…
Does anyone know who/where sells composite drill bits? I once saw an ebay auction for some composite drills. They looked like metal reamers but tapered.
Anytime I drill carbon fiber it seems to break out the carbon from one side or both - so frustrating when you want a nice clean looking part.
Thanks all for the tips. I melted some candle wax into the holes and as it was my first ever attempt at making a fiberglass mold, or working with epoxy or laminates of any type, this proved to be the least of my worries. In the end it sort of worked, but not completely.
I am taking a mix of the ideas here though to optimize my next mold. I’m going to use the wax that is already in the holes to make a dimple in the exact center of the hole thus making it easier to drill when I have my finished piece.
I did make a final set of the carbon heel guards, but I was having issues holding a vacuum with the space saver bags I’ve seen other people use which made for a crappy mold and an end piece that needed lots of work to look good, as well as not thoroughly wetting the carbon down.
I am going to revisit the vacuum situation and start back from square one with the knowledge I now have.
On the plus side, between the mold release wax and the PVA I had no issues at all with things sticking. Thought, that could have been traced back to the bad vacuum as well.
Learn from your experiences and don’t repeat the mistakes!
Drilling CF, it is like drilling acrylic so test this idea out: Use brad point / Forstner wood bits (Stanley used to have these power point bits…same thing) and drill 1/2 of the way thru then flip it over and finish drilling thru the other side. Meeting in the middle…
I’ll try and shoot a picture of the drill bit but have the flu right now…
Well, I did everything real ghetto-like. I just picked from the random drill bits floating around in my tool box. They seemed to work fine. I used a small bit to drill a pilot hole and then, using the bigger bit, just very easily drilled on one side to make the hole bigger, but not the full size, flip it over, ease off some material, flip it over again and just go back and forth like that until you go all the way through. Then just roll up some fine grit sandpaper and give the edges a bit of a bevel.
I think I’m going to pick up a foodsaver device in the next couple of days. All of the parts I want to do are small and this will suffice until I get into the bigger stuff at which point I’ll go ahead and build one from a fridge compressor as I’ve seen others do here.