[DannyBadorine]

In the latest video, Danny R mentions using an inverted roundover bit to apply to the back of the speaker hole on the inside of the cabinet.  Does anyone know where to get one of these?  My palm router has a 1/4" shank.  I'm having trouble finding one.  Cheers!

[WGH]

Many inverted roundover bits have a 1/2" shank, probably for a good reason because any wrong move and the router will take off like a race horse.

I haven't seen the video, do you have a link? Danny has too many to sort through.

The Whiteside 3196 has a 1/4" shank, a 3/8" inverted roundover and at 1-3/8" diameter should scare the hell out of you when used in a one-handed palm router. Even with 40 years professional woodworking experience I wouldn't attempt it one handed, but then I still have all my fingers too.

Whiteside has smaller radius bits: 1/8", 3/16", 1/4"

https://www.whitesiderouterbits.com/products/3196




$64.25 at Amazon
https://www.amazon.com/Whiteside-Router-Bits-3196-Diameter/dp/B0012JG8O0/ref=sr_1_4?crid=3CI6HSO9BYLMS&keywords=Whiteside+Router+Bits+3196&qid=1690752799&s=hi&sprefix=whiteside+router+bits+3196%2Ctools%2C168&sr=1-4

[mlundy57]

The bit you are looking for is called a roundunder bit. Mine is from Whiteside. I don’t know house too a link from my phone so I will add it later from a computer

[WGH]

So far the only rounding under bit I have found with a 1/4" shank is the strange looking one above. The other Whiteside rounding under bits are 1/2" shank. I might have missed some.

I would make an extra large custom base for your palm router so it will never fall in the speaker hole or accidentally tilt.

[mlundy57]

The rounding under bits I have, and have seen, are large and heavy. They have 1/2" shanks for a reason and need a full size hand router to be able to power and control them. A router base large enough to completely cover the cutout opening when the bit is engaged is also, at least from my point of view, necessary for both safety and to keep the router from tipping during the cut. I made mine large enough that no part of the opening is exposed at any point during the cut.






https://www.whitesiderouterbits.com/collections/solid-surface-rounding-under/products/2034

[Danny Richie]

Just Google "inverted radius bit" and you'll see some options.

[WGH]

Just wondering... is there a technical reason everyone is rounding over the inside of the speaker hole after the speaker is assembled?
Seems like it would be quicker, easier, cheaper and safer to do it before assembly.

[JCarney]

Just wondering... is there a technical reason everyone is rounding over the inside of the speaker hole after the speaker is assembled?
Seems like it would be quicker, easier, cheaper and safer to do it before assembly.

Right? That is what I thought, and have thought every time this subject comes up. Do the interior round overs first, before anything else. Seems logical to me.

JCarney

[mlundy57]

It is much easier to do it before assembly with a round over bit. However, if for some reason that didn't happen than a round under/rounding under/inverted radius bit is the way to add it after the fact. A couple reasons could be you are modifying an existing cabinet as in an upgrade, or like me, you got ahead of yourself and glued the baffle on before adding the roundover to the back side.

[MarvinTheMartian]

If you do find an appropriate radius round under bearing bit with ¼” shank (I couldn’t)

++1 oversized base plate is absolutely critical for safety’s sake.

And remember you do not have to make this entire cut in one shot.
A palm router may not have the horsepower to hog out all that wood at once.
Approach your final target depth in multiple passes . For the best finish  save the smallest change for the final pass.
Example: for a 3/4” round over bit, pass:1 = 1/4” shy  > pass:2 = 1/8” shy > pass:3 = right on the money.
It sounds like 3 times the work but you will be one with the machine by the third pass.

Or get creative with a medium/fine hand rasp, it won't look pretty but heck, it's on the inside  : )

Shawn

[WGH]

If you do find an appropriate radius round under bearing bit with ¼” shank (I couldn’t)

The entire router bit does not have to be used. Whiteside 3196 (see above)

[MarvinTheMartian]

If a 3/8” round over is sufficient for a 6/8” baffle.
You have found the biggest radius 1/4" shank pick = Whiteside.

I was looking for 4/8" round under, they are all 1/2" shanks and rightly so.
Shawn

[DannyBadorine]

So many good replies here.  Thanks to everyone!

[DannyBadorine]

Just wondering... is there a technical reason everyone is rounding over the inside of the speaker hole after the speaker is assembled?
Seems like it would be quicker, easier, cheaper and safer to do it before assembly.

There are times where I'm making a prototype and I am changing drivers on an existing cabinet.  In doing this, I am placing a new front baffle on and cutting the holes out after.  There are also times where I'm improving an existing speaker for someone.  And then there are times where I forgot to do it first.  Again, it's usually on prototypes and once the design is done, the baffle work can be done before it's glued on.

[T4Man]

An inverted roundover bit would be useful for upgrading some retail speakers.