I was thinking 4/0 stainless steel wool like the pioneers used to stuff horn driver rear chambers, but wondered if there was an appropriate etching chemical.
My partner did some Plexiglas (flat sheets), he used his orbital sander with low grit sandpaper
dave
dave
Right, some form of buffer for flat pieces, I was just thinking for hand buffing. When you say low grit, I assume you mean (very) fine grit commonly used for wet sanding like used for smoothing a paint finish, etc., prior to the final gloss buffing.
So I tried sandpaper of all grits. I've got good German 'Starcke' stuff but all grits either leave distinct scratches (coarser grits) or smears of scratches (finer grits). Even with a lot of work in different directions. Orbital would be good but hard to apply to a cylinder and impossible to apply to the inside. I bought some 97% acetone as it etches acrylic but it was unsuccessful, just more smears no matter how i applied it, didn't try soaking. I wanted to frost it so I could have a gentle warm-white led in the speaker illuminating the port (cheesy maybe, opinions welcome 😉) but it didn't go as well as I hoped.
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If anyone is curious, if you soak acrylic in acetone, it does frost blotchily but causes cracks to form in under a minute:
I've ordered this giant (for my 1/4" router) bit from Aliexpress to chamfer the 18mm ply around the edges of the speaker.
An almost 2” diameter bit on a 1/4” shaft could be asking for trouble; if your router has variable speed, I’d slow and make many shallow passes.
If that was me, I think it was probably 220G on a high speed air powered random orbit sander with 3/16” orbit.
I completely agree! In fact after chipping my tooth I got a 3M G500 face shield today to add to my PPE defenses. Terrifying! My 90s AEG router can go pretty slow.
So I have progress and bad news. And I need some advice to rectify a mistake. Here is my progress:
Cabs marked-up and 6mm pilot hole for router circle jig drilled.
Rebate partially routered. I wanted to end up with a 10.5mm wide rebate but started off making them two 6mm router bits wide (12mm) as I would be cutting the center circle out. Once it was gone I would be left with 10.5mm rebate:
Despite tightening the bejeezus out of the thumb screw from my circle jig, it failed me and slipped. I've replaced it with a hex bolt and wide washers, too late...:
The bad thing. I did not notice the slip occur (at 12 o'clock below) as I began the first pass to cut the center out. I didn't notice as I moved the router between speakers. The upshot is that my recess is only 7mm wide. I had the final 2mm deep pass with the router to go before I noticed so the center here is held with 2mm thick ply while I decide what to do:
7mm recess is barely enough for the screw hole:
Cabs marked-up and 6mm pilot hole for router circle jig drilled.
Rebate partially routered. I wanted to end up with a 10.5mm wide rebate but started off making them two 6mm router bits wide (12mm) as I would be cutting the center circle out. Once it was gone I would be left with 10.5mm rebate:
Despite tightening the bejeezus out of the thumb screw from my circle jig, it failed me and slipped. I've replaced it with a hex bolt and wide washers, too late...:
The bad thing. I did not notice the slip occur (at 12 o'clock below) as I began the first pass to cut the center out. I didn't notice as I moved the router between speakers. The upshot is that my recess is only 7mm wide. I had the final 2mm deep pass with the router to go before I noticed so the center here is held with 2mm thick ply while I decide what to do:
7mm recess is barely enough for the screw hole:
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The cross section looks like this where the screw is going to have very little (zero) purchase on one side:
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If I follow, add glue blocks where the bolt holes go to add sufficient thread depth strength before drilling them.
Get fibreglass resin and pour into the cut until flush with the baffle surface and then recut.
Absolutely! Variable speed a must with a bit that size, particularly if hand held, and with a 1/4" shaft. Scary.
Thanks Andrewbee and GM for your suggestions! I did do some research into screwing into epoxy and it seemed like it could get a little tricky. A good fix to have up my sleeve for another time. And GM that was useful, I had not come across glue-blocks, I may well still use them to reinforce my repair.
In the end I decided to plug my mistake using a ring of 15mm ply which I will glue and then re-router.
To recap, I had accidentally made the recess too narrow (in yellow below). I realised when I had almost cut-out the driver hole and stopped 2mm shy (on the y-axis) of cutting through into the cab:
To begin with I enlarged width of my mistake (in red) to better allow a repair ring to fit. My too-small recess is in yellow):
I cut two circles from scrap ply, their circumference will fit flush against my small recess:
Stuck down with double sided carpet tape:
Then a cut with the router to create a ring. I read someone on the forum suggesting an up-cut router bit for quick jobs which I may look into as removing 6mm x depth material is a bit excessive for a simple cut:
The ring fits great which I'm super happy about. The ⌀OD needs to fit flush, the ⌀ID doesn't matter as it's going to be routered away tomorrow:
Glue should be dry tomorrow (I wiped down after this photo!) and then I can start routering from scratch carefully this time!
Sorry if my build-log is a bit long winded for what is essentially a super simple cabinet! I find it quite helpful to write-up like this to go over what worked and what didn't. Maybe this will help another beginner in the future.
In the end I decided to plug my mistake using a ring of 15mm ply which I will glue and then re-router.
To recap, I had accidentally made the recess too narrow (in yellow below). I realised when I had almost cut-out the driver hole and stopped 2mm shy (on the y-axis) of cutting through into the cab:
To begin with I enlarged width of my mistake (in red) to better allow a repair ring to fit. My too-small recess is in yellow):
I cut two circles from scrap ply, their circumference will fit flush against my small recess:
Stuck down with double sided carpet tape:
Then a cut with the router to create a ring. I read someone on the forum suggesting an up-cut router bit for quick jobs which I may look into as removing 6mm x depth material is a bit excessive for a simple cut:
The ring fits great which I'm super happy about. The ⌀OD needs to fit flush, the ⌀ID doesn't matter as it's going to be routered away tomorrow:
Glue should be dry tomorrow (I wiped down after this photo!) and then I can start routering from scratch carefully this time!
Sorry if my build-log is a bit long winded for what is essentially a super simple cabinet! I find it quite helpful to write-up like this to go over what worked and what didn't. Maybe this will help another beginner in the future.
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PS I know everyone hates the 2" chamfer bit in a 1/4" router idea 😉 but yesterday I enlarged the base with a bastard file to allow the bit to fit through. Annoyingly (predictably?) the circlip from the top of one of the rods pinged away never to be seen again. My collection only goes up to 10mm so I had to order a set of 10-20mm clips. Handy for the future hopefully.
I also ordered some 10oz cotton coveralls, mainly as I'm beginning to learn to weld, but also as a bit of protection in case I take a router bit to the gut..
I also ordered some 10oz cotton coveralls, mainly as I'm beginning to learn to weld, but also as a bit of protection in case I take a router bit to the gut..
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After the glue dried I was able to router the recess, you can see the dark seam of glue in the middle of the recess from the repair.
As I was about to make the final cuts all the way through the ply I overtorqued the bolt on my circle jig and stripped the thread in the aluminium flat bar it inserts into. 😡 Gaah two steps forward and one back. This was going to be the final use of my circle jig in this project. I won't have access to a pillar drill until Wednesday when I can drill a new hole in the alu bar and tap it. Ultimately I should buy a 5*10*115mm steel bar and replace the alu one. It's a bit of a ship of theseus situation but I do like this Chinese style of circle jig. The Jasper one is silly money in the UK
As I was about to make the final cuts all the way through the ply I overtorqued the bolt on my circle jig and stripped the thread in the aluminium flat bar it inserts into. 😡 Gaah two steps forward and one back. This was going to be the final use of my circle jig in this project. I won't have access to a pillar drill until Wednesday when I can drill a new hole in the alu bar and tap it. Ultimately I should buy a 5*10*115mm steel bar and replace the alu one. It's a bit of a ship of theseus situation but I do like this Chinese style of circle jig. The Jasper one is silly money in the UK