Has anyone used the finger joint router bits?

I am looking at putting together a wooden steering wheel for a 27 chevy and the original pieces are finger jointed together. Of course I don't have any finger joint tooling and I was looking online and there are some inexpensive options. I am thinking of using my cnc router to rough out he curved section and cut to length, run a finger joint bit on the ends then finish cut the width/curve and maybe even run a roundover.

So, my question is, how deep do these fingers cut? It has been awhile since I had the original wheel in my hands, but I recall it being 1/2" depth of the fingers. I am looking at this type: Freud 99-037 Finger Joint Router Bit 1-3/8-Inch Diameter w/ 1/2-Inch Shank

It says on this that DOC is 5/16", do you guys think that is deep enough? I am not worried so much about 100% factory original.

Anyone used one? I guess worst case I could get a shaper cutter with a deeper cut and cut the joints on a shaper.

Jason

Since I used to make so much curved work, I've made my own finger joint cutters for 40 years. Have numerous in various configurations for router and for tenoner. Most are made by stacking up standard 1-3/4", 1-7/8", and 2" wing router cutters, with shop made spacers and shim washers. On the ones with wider fingers, I use bearings between at least one set, and often sleeve the bearings. Depending on bearing and original OD, these will cut 5/8" deep, or up to 3/4" deep with no bearing and 1/2" dia spacers. Mine don't have the taper land, though.

Can't find a picture of the cutters, but here's a very small curve, (scrap from) nosings for landing stair starter.



If you have not done this before, note the amount of undercut at each joint, depending on the angle and the depth of cut. The blank has to be made enough wider toward the inside curve, to accomodate. As can be seen, I (rough) pre-bandsaw the OD of the blanks, leaving clamping ears. On less than a full circle, the rest is pulled together with a bar clamp or strap across the open crescent end.

The fingers can just be seen in the large arch here



And faintly in the small arch here



And used in every full piece of arched moulding, inside and outside the window because it makes it so much easier to deal with the components moulded complete in the shop, and to install as a unit on site.

Very, very nice work, Stephen!

Mike

I have done a ton of curved work on the router, the pcs were usually just end cut straight for a regular butt glue joint, it is pretty satisfying to cut curves... Anyway, I have quite a few wing cutters, didn't know if that was a viable cutter as all the finger joint cutters I see have a curve to it with rounded ends. I may just stack up wing cutters like you did and try that.

Then I get to figure out how to make the finger hold bumps.

A well made and glued 14:1 ratio scarf joint can net nearly the full strength of a solid board of similar section, and probably 85% for practical use and calculations. 14:1 finger joints to sharp points can net about 70% with a fairly fine pitch, dropping to 20% or so with a coarse pitch and blunt tips or a steeper slope.

My guess is that parallel lapped finger joints with a "reasonable" number of fingers can net somewhere close to 50% if the laps are well made, well glued, and clamped across the joint as well as end-wise. (BTW, this is also recommended, clamp both ways, for highest performance with tapered fingers as well). When there are "enough" fingers and the glue area is "enough" that the test piece always breaks on one side or the other & not in the joint itself, it is failing where the wood cross section is aprox. 50% due to alternating fingertips and gaps. There is a tiny bit of additional end-grain strength, but that is usually not practical to calculate or include.

I usually do not clamp across the joint for millwork purposes and use yellow glue to get parts done faster. When the structure matters, (or for exterior work) I use epoxy and/or clamp across what are usually slightly longer joints. (I make the fingers longer for larger glue area, but hence they are more flexible and need clamped flat)

The quoted strength estimates are a crude summary of several graphs and figures on the subject in _Adhesive Bonding of Wood_ by M.L.Selbo, 1978. Information in the book is based on Forest Products Lab reports and on industry tests.

smt

stephen thomas said:

Since I used to make so much curved work, I've made my own finger joint cutters for 40 years. Have numerous in various configurations for router and for tenoner. Most are made by stacking up standard 1-3/4", 1-7/8", and 2" wing router cutters, with shop made spacers and shim washers. On the ones with wider fingers, I use bearings between at least one set, and often sleeve the bearings. Depending on bearing and original OD, these will cut 5/8" deep, or up to 3/4" deep with no bearing and 1/2" dia spacers. Mine don't have the taper land, though.

Can't find a picture of the cutters, but here's a very small curve, (scrap from) nosings for landing stair starter.

If you have not done this before, note the amount of undercut at each joint, depending on the angle and the depth of cut. The blank has to be made enough wider toward the inside curve, to accomodate. As can be seen, I (rough) pre-bandsaw the OD of the blanks, leaving clamping ears. On less than a full circle, the rest is pulled together with a bar clamp or strap across the open crescent end.

The fingers can just be seen in the large arch here

And faintly in the small arch here

And used in every full piece of arched moulding, inside and outside the window because it makes it so much easier to deal with the components moulded complete in the shop, and to install as a unit on site.

Click to expand...

Wow beautiful work Stephen. You must cut and fit the glass inserts also. It must be a real challenge to get all the prices to fit close and still make overall size.

"Stephen Thomas":[I've made my own finger joint cutters]

Just thinking with bought cutters even at the sale price of $85 or so would be a high burden to pricing such work. Yes face sharpening would help get a few uses out of the bought cutters.

Most of the finger jointers are, as stated above, stacks of 3 or 4 wing (router) cutters. They come typically 1-3/4", 1-7/8" & 2" OD depending on source. Usually used for cutting single slots. I stack them with shop made spacers and shims to get good fitting joints. As can be seen, they come in versions from 1/16" thick through about 5/16" thick.

With this type of high end millwork do you have to bid or is it time and material?

Click to expand...

Both. This one was a replacement window for one that rotted out in a church after a century plus. A group from the congregation got together to fund it (donate) so I gave them a price up front, and they did things like prepping the stone work, and repairing the plaster after it was installed.

Thanks for the compliments, guys!
Jason, who started this particular thread does fascinating and often astounding work, too!

smt

If you like we will give you a free router bit if you do a review.

Call whitney at 800 346-8274

Tom Walz
Carbide Processors

Jason-

Not to put you on the spot but....
You owe it to the rest of us to take Tom up on his great offer.

smt

Not really looking to put someone on the spot.

Would like a review of the finger joint bit. If anyone else is interested please let us know.

Tom

Tom, didn't intend to blow you off, I had some family things that I needed to take care of and have been catching up since I got home. I would like to check out your cutter, I'll give you guys a call as soon as I can.

Jason

No problem. Just getting caught up myself.

Tom