Monday, February 13, 2017

chainsaw mill

My friends know I'm a big woodworker, every now and then, there's tree cutting down, or falling down, they will pass the information to me. I'm very interested in the wood, but since I don't have anyway to mill them, I have to watch them go to landfill, very sad. It's not only a waste of resource, some wood are very beautiful, and I can image if someone make furniture out of them, they live to tell a great story.

So finally I decided to make a mill, I want it to be cheap and capable. Efficiency is not my top concern, since I don't do it that often. there are basically two options: bandsaw mill and chainsaw mill. Here's a break down of pros and cons:

bandsaw mill:
  • efficient, kerf is thin, so less waste and less power needed.
  • cut faster
  • can double as a vertical bandsaw for resaw.
  • can be driven by electric motor, so can be quieter.
  • hard to port, setup is much complicated
  • ground needs to be flat
  • much more expensive
  • much complicated to build
  • less cutting capacity
  • takes room to store

chainsaw mill:
  • much cheaper.
  • easier to build.
  • more cutting capacity.
  • nimble, can cut on almost any terrain. 
  • compact
  • the chainsaw can used as a standalone.
  • setup is easier
  • cut slower
  • less efficient due to the wider kerf, waste more wood
  • noiser

For my use case, the chainsaw mill is a winner, I do milling only occasionally, don't mind do it slow and waste a little bit of wood. I most likely want to get a slab for table top or bench from the fallen tree rather than lumber. 

The classic Alaskan chainsaw mill design is pretty simple: two rails to keep it  flat on top of the slab, two vertical clamp to clamp on the chainsaw bar, and can adjust the height.

To keep the cost down, I want to use material that is readily available and cheap, Unistrut appear to be affordable and stiff enough for the application. Also with the many clamping options, it's easy to make it work. The only challenge part is the vertical clamp. I welded some round pipe on to a 1 inch square steel tube to make the vertical clamp. To finish it, I also made a tip guard out of SS sheet and a round bar on the top to stiffen it up.

To keep the cost down, I picked a home use Stihl MS311, with less than 70cc displacement, it's definitely under powered to run a chainsaw mill. To gain the maximum capacity, I used the longest bar it supports: 36 inches. Withe the clamping and everything, the max cutting capacity is 30 inches.
I tested it out on some small logs I have in back yard, it worked ok.

We had some redwood tree cut down for a trail renovation project, so I have a chance to test it out the first time. It worked pretty well, with two things to improve:
  • It's pretty heavy, since the frame is all steel
  • the vertical clamp slipped once, and the clamping does not have a positive locking feeling, meaning you don't know when it tight enough.

 I got some 80/20 stock for free as scraps. 80/20 are very versatile, lots of clamping option. Build from aluminum, means they are light and don't rust, perfect for my application. I remade the vertical clamp from 80/20, it's all bolted, so not twist from welding, also means it's easily changed if something doesn't work out. The vertical bar is clamped with four 1/4 bolt, with only 1/4 of the turn, it's loose. I also added a winch, so when doing one man operation, I can just keep the pressure down, and grind the winch, it also means a much consistent pull. I also added a scale to the vertical bar, so no tape measure needed.

The other morning a friend of mine had a Italian pine fall down, so I got a chance to try out the new mill. It worked great, the vertical clamp is very easy to adjust and locked down easily. The winch pulled the saw in the consistent rate. The only complain now is that the rails are still made from unistrut, which is still steel, so still heavy. But given the price of 8030 (about $1 per foot) I'll keep it steel until I got some more 80/20 for free ;)

Once I have the mill, I found a lot of opportunity to get beautiful slabs, I'm running out of space to store/dry them. 

Tape holder

Emma loves doing crafts, and tape if a tool she use a lot. I always want to make a cute tape holder for her. I prototyped with some ...