how would you make this chamfered edge?

[roger wiegand]

As part of rebuilding an organ action I need to make a board with an array of 72 wells in it. The wells are about 3/8" deep and 1-1/8" " in diameter. Clearly drilling the holes is easy, but how would you reproduce the chamfered edge (there are several reasons why it is important to the eventual function of the piece-- a piece of very thin, dished piece of leather will be glued over top of it and air pressure from underneath will actuate a valve. I can get into the details if anyone cares. So I'm not interested in redesigning it, just trying to figure out how it can be made. Dozens of organ manufacturers have made the same thing over the last two centuries, so it must be pretty straightforward, but there is no tool to do it in the organ supply catalogs. They need to be reasonably uniform from well to well.

The holes are too shallow to accommodate a router bearing, all of the countersink type cutters I can find go to a vee and would bottom out long before shaping the edge. I can imagine what the right cutter would look like, but is there any easy way to do this without having someone make me a custom tool? I don't have a mill or CNC machine, hoping for a drill press based solution.

Here is a side and top view of the shape of the well.


pouch well.jpg

[Maurice Mcmurry]

Would a 45 degree bevel router bit with a bearing guide work? Intriguing project, I am interested!

[roger wiegand]

No, the well is not deep enough to accommodate the depth of the bearing. I'm looking at a brass piloted bit from Infinity that might work, no bearing, just a rub surface that can be filed down to length. Seems like it would be easy to mess up the edge though with any slight tilt of the router. I'd be less concerned if I didn't have to get it right 72 times in a row!

[Maurice Mcmurry]

How about a fly cutter in the drill press with the cutter bevel facing out? Or a custom fly cutter for the hole and chamfer at the same time? I am guessing each one will be a different diameter?

[Maurice Mcmurry]

How about a fly cutter in the drill press with the cutter bevel facing out? Or a custom fly cutter for the hole and chamfer at the same time? I am guessing each one will be a different diameter? ... I have a D.I.Y compass router base for round work.

[Greg Funk]

I think I would drill a small hole in the center (before cutting the main hole) and make a circle cutting base (if you don't already have one) for a small router. Register the base using a small nail/pin in the center hole and cut a v-groove followed by the main larger diameter hole. If you keep the indexing hold small enough it should be feasible to center the main hole although it might not be perfectly aligned with the v-groove.

[Jamie Buxton]

No, the well is not deep enough to accommodate the depth of the bearing. I'm looking at a brass piloted bit from Infinity that might work, no bearing, just a rub surface that can be filed down to length. Seems like it would be easy to mess up the edge though with any slight tilt of the router. I'd be less concerned if I didn't have to get it right 72 times in a row!

You can fix the tilting problem with a flat base on the router which reaches all the way across the hole to rest on the other side. The OEM bases on most routers will do that on your 1 1/8" hole.

[Andrew Seemann]

You might be able to regrind a 1 3/8" (or whatever size it works out to be) spade bit a to match the chamfer profile. Then you can cut it in the drill press with a jig that holds it centered, and the depth stop set on the quill.

[Brian Tymchak]

You might be able to regrind a 1 3/8" (or whatever size it works out to be) spade bit a to match the chamfer profile. Then you can cut it in the drill press with a jig that holds it centered, and the depth stop set on the quill.

Along these lines, and with 72 to do, I might look into a custom profile blade for a rosette cutter. Not sure how long it takes to get a custom profile ground these days. Seems like everything else service-wise is really slow.

[Bill Dufour]

I would drill it into one thick piece of wood to allow a deep registration hole. After it is drilled and and chamfered resaw off the portion you want. The other way would be to attach the thin work piece to a chunk of 2x6 with double sided tape, some screws etc.
Aircraft countersinks max out at about 7/8" Diameter so no good.

[Bill Dufour]

For that big a hole I think you will have to look at insertable countersinks. Her eis a link to a one on ebay. The problem will be finding one with a small enough shank your drill press can grab it.
The linked one looks like it uses standard inserts. It also looks like it can chamfer two different diameter holes. You may have to drill your holes to match the pilot then enlarge them after the chamfer operation.
Bill D.

https://www.ebay.com/itm/26331299177...temCondition=4

Idea on a tool you could make from wood with a plane blade.
https://www.ferguson.com/product/ree...25/_/R-4190752

[Maurice Mcmurry]

Neat ideas, and neat tools! It is a small hole for the compass router idea. Like John, I am not sure I am getting the big picture. Will the holes be made in individual blocks? How about using a lathe? How about modifying a hole saw?

[Walter Plummer]

Here is a company that sells blanks if you want to try grinding your own profile. https://www.southeasttool.com/produc...router-blanks/

[roger wiegand]

A bunch of great ideas to explore here, thank you! For further explanation here's a picture of a pouch board like this that I was in the process of re-leathering. You can see a couple of un-leathered wells at the left side, the rest have been covered with 0.01" thick leather, with a cardboard button glued in the center to push on the bottom of the valve stem. So in answer to several questions these are not individual squares but all in one long board. Exactly as in a player piano, as John noted.

IMG_4221.jpg

One issue with a square edged hole is that if you get a bit of squeeze out of glue when you put the leather down it can make a sharp edge that will, over time, cut the leather, causing a leak and failed note. That doesn't happen with the chamfer. At the same time it increases the area, and thus the power of the pouch to lift the valve without increasing the total volume of the well by much.

Re-grinding a spade bit, or starting with one of those grindable router bits seems like a very practical, low tech and quick way to attack this. I'll probably attempt the spade bit route this morning and see how it goes. If I got really clever I suppose I could make both the hole and chamfer with an appropriately shaped spade bit; that may not be worth the extra effort and I'm not sure I'd like the quality of the resulting hole.

I suggested that that a CNC machine would be a great addition to the shop to solve this problem, but DW was having none of it!

[Maurice Mcmurry]

https://www.stltoday.com/lifestyles/...07184a0f5.html

A bit off topic, There is an image of some wonderful workmanship.