More Cheating

[jteneyck]

A friend is just starting the build of a Thorsen sideboard, shown in FWW 125, 126, and 127.  It's quite a project.  The author used classic drawer and guide/glide construction, but my friend is planning to use Blum undermounts.  The author makes it pretty hard to ferret out the dimensions of all the parts, but my friend and I managed to figure it all out, and I drew it up in SketchUp for him.  




The darker color represents plum pudding mahogany, of which he has a single large plank.  Some will be cut into veneer, and some will be the parts that have to solid, like the breadboard ends of the top and doors.  The lighter color is plain grained African mahogany.   

The drawers have half blind dovetails to join the sides to the front.  When I looked at them, I thought it would be a nice challenge to see if I can do them on my CNC.  So yesterday I gave it a try with a generic design. Using the undermount slides adds another element to the joint.  There needs to be a 5/16" rabbett on the back of the drawer front for the required clearance of the slides, when using 1/2" thick stock.  

You can go about this a couple of ways on a CNC.  If you want sharp corners then you use a DT bit.  The problem with that is you are limited to the bits that are available, and not many can produce the look of a handcut one.  If you can accept rounded corners then you can create any size and shape DT you want.  I showed some through DT's I did on this little project a few months ago, from a project by Michael Pekovitch in FWW. 

 


I was able to use a 1/16" bit in the corners of the tails, so the DT's are about as close as you can get to what Pekovitch did by hand.  I had hoped to do the same with the drawers on the Thorsen cabinet, but the need for that rabbett complicates it because of how deep the cuts need to be to make the pins.  A 5/16" deep rabbett plus a 1/2" drawer side means the bit has to be able to reach 13/16".  That's no problem for a 1/8" bit but I don't have any 1/16" or similar sized bits that have that much reach.  They may exist, however, so I'm still looking.  But for this test I used a 1/8" bit, so the corners look machine made.  There are a lot of mistakes in this, but it's still not bad for the first attempt.  This isn't glued, just fit together. 



The V's are out of place, but easily fixed.  They are inlays and represent my friend's last name.  I forgot to round over the outside corners of the pins when I did the CNC drawing, so I did those by hand.  

If I can't find a small diameter endmill to get really sharp corners then I may consider using a different shape altogether, like the dog bone type, or another that purposely has rounded corners.  

John

[BpB123]

Looks great!

Thanks for the detailed post.

One question: have you considered just cleaning up the tail conners by hand? (Just reverse of the pin cleanup you did)

Just a thought

Thanks again for this and the many other posts

-Brian

[jteneyck]

Looks great!

Thanks for the detailed post.

One question:  have you considered just cleaning up the tail conners by hand? (Just reverse of the pin cleanup you did)

Just a thought

Thanks again for this and the many other posts

-Brian

Yes, I've thought about cutting the corners by hand.  Getting a chisel down inside the tails, though, becomes the problem, made worse if I narrow the pins even more.  It's still a possibility though.  

I did find some longer cut length 1/16" endmills.  And then I realized I also should cut a rabbett on the inside of the drawer sides, so you get a nice clean edge on the inside.  The side benefit of that is that the pin sockets will be less, probably 1/8".  

John   



John

[jteneyck]

Yes, I've thought about cutting the corners by hand.  Getting a chisel down inside the tails, though, becomes the problem, made worse if I narrow the pins even more.  It's still a possibility though.  

I did find some longer cut length 1/16" endmills.  And then I realized I also should cut a rabbett on the inside of the drawer sides, so you get a nice clean edge on the inside.  The side benefit of that is that the pin sockets will be less, probably 1/8".  

John   



John

Well, I did end up chiseling out the corners by hand.  It wasn't hard after all, and the results were worth the effort.   These look just about exactly like the ones on the Thorsen cabinet.  



The CNC takes care of the difficult part.  A little handwork makes it look traditional. 

John

[MstrCarpenter]

Even though totally unnecessary, if you used your marking gauge to scratch a light line at the bottom of the tails, it wouldn't look like you cheated at all. Those look great!

[jteneyck]

Even though totally unnecessary, if you used your marking gauge to scratch a light line at the bottom of the tails, it wouldn't look like you cheated at all. Those look great!

Thanks.  Yes, that certainly would do it.  

I probably spent as much time figuring out to get the CNC to do it as it would have taken to learn to do them by hand!  But now I know how and can easily adapt it to any design.  

John

[Hank Knight]

...  

I probably spent as much time figuring out to get the CNC to do it as it would have taken to learn to do them by hand!  But now I know how and can easily adapt it to any design.  

John

I came to that conclusion a long time ago when trying to use a Leigh dovetail jig. I used it so seldom that I had to re-learn it every time. I decided to spend the time learning to cut dovetails the old fashioned way and I haven't looked back - gave my Leigh to a friend. Once you learn those skills you don't forget them. A little practice once in a while keeps them fresh, but you have them always, and it's faster than you might think. I can mark a set of dovetails, cut them and fit them in less time than it took me to set up the jig and the router.

[jteneyck]

I came to that conclusion a long time ago when trying to use a Leigh dovetail jig. I used it so seldom that I had to re-learn it every time. I decided to spend the time learning to cut dovetails the old fashioned way and I haven't looked back - gave my Leigh to a friend. Once you learn those skills you don't forget them. A little practice once in a while keeps them fresh, but you have them always, and it's faster than you might think. I can mark a set of dovetails, cut them and fit them in less time than it took me to set up the jig and the router.

I tried my friend's Leigh jig once.  After an hour or so, I took it back to him.  Too complicated.  What looked like a 30 page manual for it should have been my first clue.  I admire folks who can efficiently cut dovetails by hand.  I'm just not one of them.    

The benefit of the CNC is that now that I have it figured out there will be no need to relearn how to do it the next time.  My drawings are annotated where needed, and the toolpaths are all there.  If I wanted to recreate these exact parts, it would be nothing more than chucking the wood on the machine, installing a bit, and pressing go.  

John

[EdL]

I have an Akeda dovetail jig....same story, get the manual out, re-learn from page 1....lol

Ed

[Hank Knight]

I tried my friend's Leigh jig once.  After an hour or so, I took it back to him.  Too complicated.  What looked like a 30 page manual for it should have been my first clue.  I admire folks who can efficiently cut dovetails by hand.  I'm just not one of them.    

The benefit of the CNC is that now that I have it figured out there will be no need to relearn how to do it the next time.  My drawings are annotated where needed, and the toolpaths are all there.  If I wanted to recreate these exact parts, it would be nothing more than chucking the wood on the machine, installing a bit, and pressing go.  

John

That's amazing! I would love that, but I have two things working against me: I'm technologically challenged and I'm old, past the time when I looked forward to adding a major piece of equipment to my workshop and learning a new set of skills.