Trimming the soundboard and the back without a router

[Jim Kirby]

OK, after a bunch of posts here without anyone mentioning it, I feel like I may be making a total whatever of myself for asking, but, here goes. If you are going to rout for binding channels (an assumption on my part), why do you need to flush up the plates anyway? Just go right to the binding process. (Heh, maybe I live out on the edge.)

[Trevor Gore]

No need to Jim, as Mario said here

UNLESS

you build using an outside mould and need to slide the rims, with one plate on, through the mould to get access to the other edge of the rim. If you use thin moulds (say < 50mm) you don't end up pushing the plate into the mould. But if you use thick moulds (say > 80 mm) and you glued the back on first, to get access to the top edge the back plate has to slide into the mould. Don't try that unless you have the edge trimmed flush or even slightly undercut, as I mentioned here.

Regarding, thick verses thin moulds, thick moulds are stiffer and the extra depth gives a little more stability to the end blocks when you glue the last plate on and lock up the geometry. Thin moulds are lighter (can be a plus or a minus), less stiff, but you don't have the trim issue.

The majority of my moulds are thick, but flush trimming on a table router can be safely done in seconds, so is not an issue for me.

[Clay Schaeffer]

If you are trimming the plates without a router, then you are probably cutting the binding channels without a router. If you are using a gramil or some such device you would need to flush trim the sides first.
Not all the instruments I build are bound, but even for those that are, I like to flush trim the plates before routing the binding channels. It just seems to make them come out better.

[Mario Proulx]

The "rotozip" guidepoint bits(I use the 1/4" one) are the greatest if you're going to use a router. But the OP was asking for non-router methods...

Trevor, doesn't everyone use 2-piece molds that can be opened? I can't imagine why we'd want a one-piece mold for the reasons you state.

[Mario Proulx]

Here's a short video of the rotozip bit in action.

http://youtu.be/0ss5ysf0Ouw

An extra detail to note is that I placed a few "pads" of masking tape to prevent scratching/gouging the top. Not necessary when trimming the harder woods of the backs, but a must-do for the softer top woods.

[Trevor Gore]

Trevor, doesn't everyone use 2-piece molds that can be opened? I can't imagine why we'd want a one-piece mold for the reasons you state.

Sure, the moulds are two pieces. But if you want to hold the rim set +1 plate below the surface of one side of the mould, a flush trim is essential.

Here's an example. This mould is classical shaped, but gets used for both SS and classical guitars which are different depths with different body tapers and are also occasionally wedged.

If I want to dome-sand the top edge to fine tune it before I drop the top on, I clamp the mould to a bench, which means the back has to be inside the mould and so has to be flush trimmed.

There's other ways to do this, of course, but this method is handy (and quick) for me, especially when dealing with an assortment of rim profiles.