Return to the shop
The last few weeks were taken up with vacation and conferences. So there has been no progress on the crib. Teal and I had brought in the last of the wood from the shed, but it was not thick enough for this project and has to wait for another project. This was the last of the Wisconsin Woodworker’s Guild Logfest hauls that I had set up to air dry. At its peak, it was over 1300 board foot of lumber, which has now been reconstituted into many pieces of furniture for the family and friends.
So yesterday we set off for Kettle Moraine Hardwoods which is our local lumber mill. They had a nice selection of thick Red Oak (5/4 and 8/4 – 1.25-2″ thick) and we picked up some Hard Maple and an Elm slab for future projects, as well.
Once home, it was time to surface the boards on the jointer and planer and then cut them to rough length in preparation for sending them to the CNC router. At this point, there was a minor design change as the thick stock for the legs was completely cleaned up at 1.86″ vs the 1.5″ I had in the design. So we decided to go with thicker legs. However, this leads to more work as I did not have a router bit that would cut deep enough, which will be detailed later below.
I fired up the computer for the CNC router and some problems arose. I had not used it for ~2 months and only had the windows 10 logo showing for 45 min. At this point, I rebooted again and it came up in a few minutes. However, Mach 4 which is the CNC controller software for the router had a whole series of errors when starting, and was unusable. Most of the plugins would not work. So I restored it from the backup copy, restarted the PC again and it started to work. However, in testing, many of the configuration parameters were missing including “little things” like the home switches and control for the spindle. Digging through my notes for the configuration values, I got it running again. Now, thoroughly annoyed, it was time for a reward of our home brew Imperial Stout which is now ready for consumption.
After re-zeroing the CNC router it was time to set up the first part and make a test run. The crib end top rails were chosen as they are the smallest parts and least costly in case of problems. The 8/4 stock for the leg pieces was over $150. Making wach leg approximately $35-50, so I was not going to try those first.
So the stock is clamped on the CNC router and you can see my “cheat sheet” where I have printed out the outline and marked the distances from the near end for the various clamps.
Next you can see the cut under way. At this point I have left off the dust shoe, so there are chips EVERYWHERE.
Now the top rail is completed and vacuumed off.
Another shot in progress, looking down with the dust shoe in place.
With the top rails successfully completed, now I move on to making the legs. One of the front legs being cut. In order to prevent the part moving I used not only the 5 clamps shown but also some small strips of double stick tape which help reduce the part sliding under load immensely. With this CNC router, the limitation on cutting speed is not the machine, but the ability to clamp the work and avoid it slipping under the cutting forces. Cutting speed was 100 inches per minute, 18,000 RPM at 1/4″ depth of cut with a 1/2″ 2 flute carbide end mill.
Set up for one of the rear legs – 43″, 110 cm long. Not your ordinary tabletop CNC router. . Note the beautiful curl figure in the stock. Later, you will see how I make this “pop” when finishing.
The other back leg ready to cut
This is why I use wooden clamps. Just a minor nick this time. These are shop made on the CNC router.
Another look at the scale of these cuts and the finish off the CNC router. This was without a reverse last pass as I don’t (yet) have a router bit long enough to do so and that would look even better.
Here are the legs off the CNC router. As you can see I was not able to cut all of the way through. The depth of cut was limited to 1.5″ based on my largest end mill / router bit. So now they need to be run through the band saws and then flush trim routed. The end curves are too tight for my big band saw (24″ with 1/2″ resaw blade ) and need to be run through my small one (12″ with 1/4″ skip tooth blade).
Bandsawing the excess off the legs on the 24″ band saw.
Flush trimming off the excess. The holdfast works great to clamp irregular stock like this. Teal also assisted in taming the work. The Oak is a bit unruly. I often had to reverse directions to minimize tear out. This means taking climb cuts which try to throw the work and router around.
First dry fit test. Not bad. The cross pieces will be flush with the upper / inside edges of the legs in the final assembly.
The CNC router made this work feasible in a few hours. Otherwise I would have had to make templates, band saw to size and flush trim through several steps. I had done a similar project with curved legs – Elyse’s Sleigh Bed. This is MUCH easier and with less chip out to fix.
Movies of the CNC router at work
The first part is without the dust shoe (chips Everywhere) and the second part is with the dust shoe in place (much neater) .