[WoodFrog]

I have been trying to replicate a frame for a grill off of a speaker I am refurbishing. However, I have not been able to find an exact match for the roundover used on the original grill. I had 3/8" and 1/2" bits on hand, it was bigger than those, so I ordered an CMT 838-990-11, 3/4" and it is a bit too big. I went over to the local big box store and held up bits to my profile, tried the Bosch 5/8" and another one that was bigger, but none of them were exact.

What am I missing here, did the OEM use a non-standard bit or are there more than one type of each incremental 1/8" size? i.e. is there different profiles that are still the same size, such as 1/2" or 3/4"? I see that they list a rise/run and radius, so could very well be, but how would I know what my job calls for?

I think the 3/4" bit would work, I could just make the old and new grill the same using the new bit. However, I would like to learn how to measure and know exactly which bit I need for a match...your thoughts please?

Gavin

 

[MEBCWD]

Gavin does the roundover have to be exact? Usually, a roundover is a decorative element so a little variation smaller or larger should be okay. I'm not sure how far apart the speakers are but most people would ever notice that the roundover is slightly different. Or, as you said you could do both the old and new frames so they would match. One other thing to consider is how much sanding was done on the roundover after it was cut, that would change the roundover slightly and maybe that is what you are dealing with.

As far as knowing exactly what bit to use, I would use the one that fits the profile the closest.

 

[TWheels]

Look at the selection of roundover bits offered by Freud, this Forum’s preferred brand. https://www.freudtools.com/explore/router-cnc/edge-treatment/rounding-over

 

[mgmine]

The OEM most likely made the profile on a shaper so you won't find an exact match.

 

[sunnybob]

Where was the speaker made? its most likely metric.

 

[DesertRatTom]

I also suspect it was cut metric. It will likely be hard to find in an Imperial world. I suggest you consider sanding to get as close as possible to the original. Or, if it's all one piece, get the closest fit, but slightly smaller, and rout all four sides with it. But I'd go with sanding. Maybe use a concave block and affix a bit of sandpaper to the inside curve so you can control the curve more easily.

 

[WoodFrog]

The speaker was made in Canada, it is an older Mirage BPS-150 subwoofer with an 8" driver on each side. Therefore, could be metric. Very unlikely anyone would ever notice a slight variance as it is on the floor, and painted flat black, but I wanted to get close and learn from this.

The frames will have black grill stretched over them and glued down with 3M 77 spray adhesive.

All good points on the reason I can't match it, shaper, sander, metric, etc. At least we ruled out, mostly, that I am crazy!

Freud are my go to bits as well, but my "advanced" 1/4" starter set only came with a 3/8" roundover, I had a unknown 1/2" I got thrown in with a big box of woodworking stuff I bought at an estate sale, and the CMT was on a great sale. I initially thought I would go 100% Freud, but that goes out the window the first weekend you are in the middle of a project and need to buy a bit fast or you see a great sale on a bit from another good quality brand.

Gavin

 

[WoodFrog]

I got my PC 690 that I ordered, this thing is mint! It is a 'Type 6' and made in the USA, hopefully that was a good generation of the router.

I did my setup and routed the new and old grill frame, wow it turned out great. I was surprised, it didn't take all that much off the old one so I was actually fairly close on my bit choice.

As far as painting them flat black, would you rattle can them or 'stain' them black using something like a diluted craft acrylic? Keep in mind, I will be putting spray adhesive on them to attach the grill cloth.

Gavin

 

[harrysin]

Rattle can flat black has always been my choice, thinners based so that it takes just minutes to dry in mild weather.

 

[WoodFrog]

The grills turned out great, thanks for the tips and support!

Gavin

 

[Nick2727]

Great looking piece. Thanks for coming back to share it with us! Sure it sounds great as Well!