Oval to D hole

B25Gib

Hello Jay -
You can buy some thin basswood at a large "craft store" wide enough to cut some increasingly larger D-hole templants until you have enough room to put your hand and wrist angle thru to shave the braces. This could help you get a starting point on how much larger an opening to cut! Quite inexpensive as I used 1/32" basswood to reduce the D-hole opening on my mid 90's Saga D-500 with noticable less bass heavy response. Check it out!
Jam on!
Rocky

noodlenot

good to know your comfortable with he technique. i seldom use routers and i find them a bit daunting (and noisy... ah, and dirty!): all that torque on top of a thin and light piece of select wood makes me nervous. i also don´t like the tear out (edit: like a fuzziness) they leave on softwood endgrain, so i´ve scored the purfling/binding lines with a purfling cutter before going in with a router on the two guitars i´ve used one. but only for the purfling channels. i´m sure you could sand it of, though.

but i´d really like to know what you´re trying to accomplish here. you want access to carve braces? which ones? how much? what for? i don´t have my selmer plans here with me, but i can try to find them if you don´t have them already. and remember that the bigger the soundhole, the upper the "air" resonance goes in the frequency spectrum. the effect will be most dramatic in the beginning of widening the hole, if my memory serves me.

keep us posted!

Jazzaferri

Ahah.... Is it the larger the hole the higher the frequency response.

Yes the idea is to remove as much material from the braces as possible without substantially changing the strength.....hence the parabolic shape.

There is a guy in the states who does this for high end flattops and the difference between the before and fter is amazing. He just charges way more than the guitar is worth. The dremel mini router I would use for cutting the hole while noisy and dusty has a cutter that is more like really aggressive sandpaper so the tearout when used with masking tape is almost nothing.