Bridge City Kerfmaker Geometry

Create a review for a woodworking tool that you are familiar with (Shopsmith brand or Non-Shopsmith) or just post your opinion on a specific tool. Head to head comparisons welcome too.

Moderator: admin

Post Reply
User avatar
tdubnik
Platinum Member
Posts: 545
Joined: Wed Nov 12, 2008 8:04 am
Location: Talmo, GA

Bridge City Kerfmaker Geometry

Post by tdubnik »

I have been studying the Bridge City Kerfmaker pictures and videos and was intrigued by this little device. It's pretty ingenious and pretty simple when you think about it. I played around with it in Sketchup until I had a working mock-up shich I'll post and describe below.

Image

This would be the basic set up with all parts collapsed. There are basically 3 pieces plus the locking devices. With all parts collapsed the offset between the top 2 parts and the bottom part determines the maximum blade width.

Image

You would set the Kerfmaker to your blade or cutter width by sliding the middle part out until the offset between it and the bottom part matched your blade and then lock it down. I used a 1/8" saw blade for this example.

Image

You would set the device to your material thickness by sliding the top two parts (which are now locked together) until the gap between them and the bottom part matches your material and then lock them down. My example shows a 3/8" material thickness.

Image

This shows how the device is butted against the stop for the first cut. Notice that the stop has to be narrow enough that the stop will slide into the notch created by the offset of the device. In my example I show a cut at the very end of the Kerfmaker for illustration purposes. You can set it up to make a cut anywhere along your board.

continues on next post...
User avatar
tdubnik
Platinum Member
Posts: 545
Joined: Wed Nov 12, 2008 8:04 am
Location: Talmo, GA

Bridge City Kerfmaker Geometry - continued

Post by tdubnik »

Image

The kerfmaker is now flipped over and butted against the stop again, but this time the notch does not slide over the stop. This makes the second cut to the precise distance as your material thickness. You will notice that the measurement from the inside of the blade on the first cut and the outside of the blade on the second cut is 3/8"; which matches the thickness of your material.

I am thinking of making a prototype and looking for a knurled thumbscrew nut about 1/8" thick that looks like the Bridge City one. If anybody knows where I can find one let me know.
User avatar
dusty
Platinum Member
Posts: 20230
Joined: Wed Nov 22, 2006 6:52 am
Location: Tucson (Wildcat Country), Arizona

Post by dusty »

"Making Sawdust Safely"
Dusty
Sent from my Dell XPS using Firefox.
keakap
Platinum Member
Posts: 1331
Joined: Tue Jan 16, 2007 5:09 pm
Location: Kailua, Hawaii

Post by keakap »

tdubnik wrote: I am thinking of making a prototype and looking for a knurled thumbscrew nut about 1/8" thick that looks like the Bridge City one. If anybody knows where I can find one let me know.
Very nice drawings and explanation. Thanks. (Although it will take the edge off my anticipation somewhat, while I await delivery.)

About the knurled nuts or knobs, have you looked at Bridge City itself? I know at least at one time they sold knobs of various sizes without the usual RW inlays, so you could turn your own. I believe the parts like that were 'blanks' of the various sizes used in their special tools, like the Squevel, CenterScribe , etc., so they might offer Kerfmaker type pieces as well.
User avatar
tdubnik
Platinum Member
Posts: 545
Joined: Wed Nov 12, 2008 8:04 am
Location: Talmo, GA

Post by tdubnik »

I found knurled thumbscrewsthat work at Stewart-MacDonald.

I've already completed my prototypeand it works great.
Post Reply