Thursday, 9 December 2010

Router Surfacer / Planer

I’m in the process of making some finger jointed boxes but to do so I needed to rip some planks in half to get the thickness I needed. The challenge I had was ripping 1500mm long planks that were 19mm thick and 110mm wide. My circular saw only cuts to a max depth of 65mm and I don’t have a table saw. My only option was to make some bench buddies to hold the planks up and against the side of my work table and then make two passes on the plank with the hand held circular saw. It’s very ghetto and was never going to produce a nice cut but I had no other option. So I proceeded to rip down the middle of the 19mm plank, flip it over and rip down the other side. Very early on I noticed that the wood wanted to fold in on itself behind the blade as I made the first and second cuts. To overcome this I cut some 3mm shims from hardwood post I had laying about and as I cut along I slipped a shim in behind the blade every 100mm or so. This was quite effective in preventing the cut wood from clamping on the back side of the blade which was causing the timber to burn.

With the planks cut in half I was left with a lovely set of saw/tool marks, burning and a groove where the wood had shifted during the process of flipping it over for the second cut. It was never going to be perfect but I’d hoped for a nicer initial result than what I got. So, I jumped online and began looking for thicknessers and was astounded at the cost of the machine and the cost of the replacement blades and parts. I am not in a position to be spending that kind of money on something that is going to only be used every so often. This presented me with challenge two for this project – how to surface the material and get it to a uniform thickness using what I had laying around in the man cave (aka workshop).

I got thinking, rather dreaming, about how far away my CNC is from being started and had an idea to make a manual sled to move the router around. What followed were some sketches for a 2 axis manually controlled router sled system. The idea being that the X axis was long enough to do a whole plank in one pass and wide enough in the Y axis so that it could do a few planks at the same time. Using the sketch I began looking at what I had available in the scraps pile to see if I could get it to work. It turns out that I did have all the materials to make the basic sled (minus the bearings to make the linear carriages slide nicely).

So I set about using:
-          1x old laminated chipboard cupboard door
-          3x 25x22x1.8mm aluminium extrusions (that I had first used for the proposal to my whifey)
-          Some 6mm (1/4”) polycarbonate/plexiglass
-          A handful of screws

I did place an ebay order for the bearings and my father in-law was kind enough to get me some M8 bolts from Bunnings while he was there. The total cost of all of that is well below $50.

Initially the sled was made to slide on wooden pads so that I could get a piece of plank surfaced nicely. Since then I’d received my order from ebay and I set about drilling and tapping the bearing carriages. BAM! I’d made a boo boo here by not considering the additional height the bearings would add to the whole assembly. It effectively put another 2” distance between the cutter and the material hold downs. As a result I had to modify the Y axis carriage so that the router base sat inside and at the bottom of the Y axis rails – where as it was on top of the rails initially. I’ve also had to modify the X axis carriages so that Y carriage sits closer to the X axis rails. Not a huge problem but it has since limited the movement of the Y axis – something I’m hoping to overcome with a few more modifications to the Y carriage and rail assembly.

With it now complete I can surface anything, including horribly uneven and figured timber, that is 1900mm x 430mm x 35mm. The best thing about the design of this unit is that I could easily increase the Z distance/clearance by adding a series of spacers to the bottom of the existing X rails. I’m thinking some pre-cut and pre drilled mdf strips will work really well for this and having them ready to go will make it easy to lift the X rails in increments of 9mm and 12mm (depending on which pre-cut strips I combine).

I am eager to see if I can use a template with this jig to do some nice engraving work on my finished pieces. More to come on that should I be successful (or if it fails).

My next mission is to create a circle cutting jig for cutting circles that are smaller than 300mm OD. My current sketches suggest I can cut a circle that is 1mm OD – provided I could get a cut work piece that small to stay put and not be shredded by the spinning router bit. In reality something as small as 5mm should be easily cut with my 3.17mm (1/8”) carbide end mills.

The original setup with wooden slides. This was upgraded once the bearings turned up from ebay.

The original piece including burns, tool makes and grooves.

The surfacing half way through the process

The finished work piece. nice n smooth

The whole assembly and finished work piece

A comparison (original on top, finished workpiece below)

The upgraded bearing rail assemblies

a short video of the diy router  surfacer / planer