Wedged and Shouldered Half Dovetail Notes

October 1, 2012 Leave a comment


* Don’t print out only a sheet with all the dimensions of elements in the mortise and tenon, it causes cumulative error – make sure to print out all the distances across the length from the end of the piece as a reference, then use a square to draw lines across the piece, and check length of other side

* Use a square to offset and pencil and slide the square to draw offset lines to complete rectangles

* Make sure your smallest wedge height is greater than the half dovetail height so you can seat it properly


Hollow Chisel Mortising

* Don’t cut all the way through, flip the piece over and meet in the middle to avoid tearout

* Double check the wedge angles, where they terminate (before making any cuts as if the wood were whole) so you do not cut too much

* You really want the proper sized chisel to avoid doubling work

* To avoid jams on first use of the day after using it prior (bit cool and compresses leftover wood in the chisel), either clean out the chips at the end of use or go very slowly to push out the old wood

* Use wide blade chisel to clean up the sides, tilting a little go across, and come from both side meeting in the middle

* Use a Dial caliper to gauge opening thickness before test fitting to avoid wasting time


Chiseling out the half Dovetail and Wedge

* Create a long hardwood guide so you can clamp it down, angled so that you cut towards the mortised out hole, and it is important to mark if you are to cut the top or bottom of the wood, and label if for which side of the mortise it is used on

* Clamp hard to avoid slip


Cut the shoulder

* Create a thin (thinner than the shoulder thickness) hardwood template of the required cut so you can use it as a guide where to remove more material and when to stop

* Use a caliper to test the width


Cut the tenon

* Establish the shoulders with a saw, clean with shoulder plane and/or chisels

* You can use a router plane to clean up a hand saw cut of the cheeks, unless it’s big, at which point either use other same width pieces around the tenon for support or use a portable router validating the depth from both sides leaves the desired tenon width, you can only remove material once as you route away your support, especially when using a trim router


SSH-ing across multiple boxes

August 22, 2012 Leave a comment

Some environments require you to hop across one or more “bastion” hosts that are intended to keep anyone unauthorized from being able to access internal networks.  This generally is a pain, but I ran across a useful workaround that makes it look like you are ssh-ing directly to the destination box, allowing things like scp, rsync over ssh, etc. all work without any extra fiddling.

In your .ssh/config file, make sure that you have the following:

Host *
ForwardAgent yes
This will allow you to leverage the same ssh key on the destination server as well as the bastion host, make sure you add your ssh key to the ssh-agent with ssh-add
ssh-add ~/.ssh/id_dsa
Then you can add an entry for your destination server:
User plock
ProxyCommand ssh bin/netcat %p 2> /dev/null

The ProxyCommand directive tells your local ssh client to connect to stdin and stdout of the ProxyCommand instead of opening a socket, the ProxyCommand uses netcat on the bastion to act as a proxy on the bastion host, connecting it’s stdin and stdout to the ssh process that connected to the destination server.  So in effect, you are sshing to the destination server, and all other ssh features work normally like additional .ssh/config options and command line arguments.

You can even chain two together

User plock
ProxyCommand ssh bin/netcat %p 2> /dev/null
User plock
ProxyCommand ssh /usr/bin/nc %p 2> /dev/null

Quick Connectivity Test

April 6, 2012 Leave a comment

This is the fastest connectivity check that I know of:

echo "Hello World" | nc -l -p 8080

And of course you can redirect the output to /dev/null or a file.