A whole new way to cut F holes

Frankly, cutting the F holes in the two fragile tops I had just spent a couple of weeks carving scared the shit out of me.

Everybody who writes about building archtops agrees, "using a pin router is the way to do it." I don't have a pin router, and haven't ever needed one so far, and I'm not going to add a homemade or expensive store-bought stationery tool o my shop, so my saga became making them cleanly without one.

I considered using a drill press with a pin in the table, but checking my machine, 2700 rpm was its top speed, and my router goes about 25,000 rpm, I think - so that probably wouldn't work without chattering. Also, I had a picture of the spiral upcut bit I wanted to use pulling the Jacobs chuck down out of the socket, destroying one of the tops, then bouncing up into my eye.

So I developed a low-tech router table template, and it worked just fine. In fact, I can't see why anyone would want o use a pin router. Here's how I did it:

Rough cut 3/4" AC pine plywood template base,  glued up with biscuits, room for pattern insets.

Cleaned up template base, routed ledges for pattern insets.

Blank pattern insets of 1/4" masonite, smooth both sides. I scanned full-size f-holes from Bob Benedetto's book, then used Indesign to produce mirror prints the same size as the insets, and spray-mounted them in place.

After cutting the pattern inserts slightly undersize, I cleaned them up. I use this odd tool only about once every six or eight years, but here it was perfect in the drill press.

Final filling he pattern inserts, right to the line.

Final pattern template, ready to use. The indent near the top is for the top braces, which lay slightly below the rim of the tops.

The point of no return - drilling a 5/8" hole for the bit to stick up through. Located it in the widest opening of each hole.

After a dozen different ideas, here is the router table setup I decided on. There simply isn't a top bearing router bit narrow enough for the "necks" of the f-holes, so I decided to use a 1/4" shank, 1/4" diameter solid carbide twin flute straight twin flute bit (did I describe that fully enough for you?) and let the pattern simply rub against the lower, uncut part of the bit. Frankly, I had fears of it smoking against the masonite pattern, but it worked just fine.

Test piece of cedar- worked great, so I went ahead with the actual tops.

This photo tells the whole story. Nice clean cut! I need to finish the inside corners with a chisel, then my next step is lining the f-holes. Everybody uses precut plastic strips for this, but I'm going to avoid plastic and use a strip of African mahogany (same board as the backs and sides) and a strip of tiger maple, which may be too difficult to bend without fracturing, in which case the center-facing strip will be rock or red maple - I have plenty of scraps of both.

Here's how a top looked when it was finished on the router table. So far, so good!