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randyjaco
10-06-2011, 05:27 PM
I got interested in the Dovetail Puzzle in this month's issue of Machinist's Workshop. The impossible joint looks like an interesting build but one of the additional features shown in Figure 2 on page 29 also looks impossible. In the portion marked Top Block, I can't figure out how to do. Shouldn't the 4 interior corners be radiused rather than be sharp corners? I just don't see how one could cut those interior angles the dovetail router bit stated in the article.
What am I missing here? Maybe his skills are just much better than mine.

Randy

randyjaco
10-07-2011, 12:27 PM
It looks like there aren't MW readers here.:)
Bump

Arthur.Marks
10-07-2011, 12:50 PM
One place where a shaper would be helpful. Haha. That said, there are a few ways to do it. Rough it out and use a cold chisel for the bottom of the pockets. Rough the two angles with a smaller diameter end mill. When you reach the bottom, finish the pocket with a purpose-made cutter. You might be able to come up with a method using a drill-point end mill? Grind a lathe bit to be the correct angles for the corner pocket. Manually align it in a mill and use the quill as a stand-in manual shaper?

garyphansen
10-07-2011, 02:59 PM
I looked at the photos but didn't read the article. Doesn't the article explain how to make it? Gary P. Hansen

lynnl
10-07-2011, 03:09 PM
I think the author made a comment acknowledging the difficulty with the sharp corners. I don't think he actually made them. ...just included that drawing sort of as a "what if."

I once had a wooden puzzle like that. I could see how the dovetails were cut, and how it was supposed to work, but could never get it apart. There was a little spring loaded ball that kept it together and that ball or spring was "frozen" in place.

Finally sawed it apart just to learn what the problem was. I'd already deduced what was holding it, but even slipping in thin sheet steel I couldn't make that ball retract.

KiddZimaHater
10-07-2011, 05:41 PM
The author didn't actually make the topside 'dummy' dovetails. Just the drawing for said dovetails.
My guess is that they could be roughed out by plunging an endmill straight down, (or drilling) and then finish the inside corners by hand. Chisel, file, and ALOT of sanding / stoning / finishing.
.
Speaking of simple puzzles. Here's mine:
Two 5/8-11 Socket-head Cap screws, with a large 1.5" Aluminum nut between them. :D
.
http://img802.imageshack.us/img802/9103/001fe.jpg (http://imageshack.us/photo/my-images/802/001fe.jpg/)

Gravy
10-07-2011, 06:33 PM
The author didn't actually make the topside 'dummy' dovetails. Just the drawing for said dovetails.
My guess is that they could be roughed out by plunging an endmill straight down, (or drilling) and then finish the inside corners by hand. Chisel, file, and ALOT of sanding / stoning / finishing.
.
Speaking of simple puzzles. Here's mine:
Two 5/8-11 Socket-head Cap screws, with a large 1.5" Aluminum nut between them. :D
.
http://img802.imageshack.us/img802/9103/001fe.jpg (http://imageshack.us/photo/my-images/802/001fe.jpg/)

The right side socket head looks suspicious. The threads run right up to the underside with no relief area. Is there a left-hand thread involved?

KiddZimaHater
10-07-2011, 07:19 PM
AAAhhhh ... good eye Gravy.
No, there's no left-hand thread involved.
I just faced-off & drilled a hole 5/8 deep into the end of a 2 inch long bolt.
Then turned a 1/2" long bolt down to a nice press-fit.
Loctite, press, and VIOLA!!!
(Hint: Don't forget to install the nut before pressing halves together :) )

Gravy
10-07-2011, 08:36 PM
AAAhhhh ... good eye Gravy.
No, there's no left-hand thread involved.
I just faced-off & drilled a hole 5/8 deep into the end of a 2 inch long bolt.
Then turned a 1/2" long bolt down to a nice press-fit.
Loctite, press, and VIOLA!!!
(Hint: Don't forget to install the nut before pressing halves together :) )

Don'tcha know that you're not supposed to give out trade secrets? Couldn't you at least claim that it required an inverted involute banjometric farkle joint with micron tolerances? You could dare anybody to prove you wrong!

:D :p ;)

I might have to make one just to mess with the neighborhood kids.