Well – here is my version of the short fence.
I’d really appreciate your looking at this and letting me know if I’m all wet in my description/explanation or if I’m missing the point or did not explain something very well. That’s the only way I’ll learn – if you tell me.
I sincerely appreciate your honesty and your input.
So here goes.
The case for the short fence is all about safety. When you cut a board you only have complete control of the board as it begins it’s connection to the blade. Once the connection to the blade is made and wood severed, you no longer have complete control – despite using a push stick. The reason for this is that once the board is cut you now have two ends independent of one another and you have released all the internal pressures of the board up to that point. This internal pressure will make both ends act in different ways. The ultimate would be for the board to just maintain a straight path through the remainder of the blade. The second option is for the board to move in toward your blade or out toward your fence. The intention of the splitter is to keep the saw kerf open to keep the board from contacting the blade. However, the board is split into two portions before it reaches the splitter. If the board is going to move it will begin doing so before it reaches the splitter. The board on the opposite side of the blade (typically the waste portion of your board) has plenty of room to move out away from the blade. The board between the blade and the original fence has no where to go – it’s trapped. If the board comes back towards the blade and touches it, the teeth coming up out of the back of the throat plate can pick up the piece and potentially toss it back at you—this is kickback.
The short fence will help stop this by creating a “space’ for the board to move in one direction – away from the blade. It does nothing for the board if it wants to move towards the blade at this point because it has not reached the splitter. I think the hope is, is that if the board is going to move when it is first cut that it will move away from the blade. The space created by the short fence gives the board room to move and not be jammed between the fence and the blade.
The position of the front edge of the short fence should be just past the first tooth that actually cuts the board. Anything past the first tooth or two is defeating the purpose and function of the short fence. The actual physical position that the short fence will rest on top of the regular fence will depend on the height of your blade. Therefore, the fence will be in a different location for ¾” material than it would be for 2” material.
The length of the fence material will depend on your saw. Mine is 19” long. The length, in my opinion needs to be at least long enough to be placed an inch or two in front of the throat plate opening and at least cover the majority of the fence back toward the front of the machine (I consider the front of the saw the edge that you stand by).
The width, or top piece, of the fence will depend on the width of your saw’s original fence.
The fence is made up of 5 pieces of wood or mdf, two knobs or levers, two pieces of metal that the knob/lever will push against and two short pieces of dowel rod.
Of all the short fence materials I have found on the web – Steve Maskery of Woodshopessentials.com has made the most sense to me. You should check out his website and the video that he has put out about the jig. He does a much better job explaining this than I do. But I am trying!
On to the building. This is really a very simple jig. 5 pieces and some hardway. And no fancy joinery. Mr. Maskery uses biscuits to join his pieces. I don’t have a biscuit cutter worth getting out of the cabinet, so I plan to use screws to join my parts.
So first – the three main side pieces are the left and right and a pressure plate which goes on the right side of the fence. These three pieces need to be the same height as your current fence.
The pressure plate needs to have two dowels inserted for placement of the outside right piece. There, of course, needs to be a corresponding hole in the right side to accept the dowels.
The outside right piece also needs to have the screws.
The pressure plate also must have a metal piece that corresponds to the back of the screw – this provides the pressure to hold the fence in place.
I clamped the two right pieces together and drilled the holes for the dowel and screw at the same time – this insured they were located correctly.
The next photo just shows the dowel and the “pressure plate.” I don’t generally have anything metal in my shop that I have scraps that I can use for something like this. So I used a flat washer. I used a spade bit to cut the hole and used CA glue to put it in.
One thing you should know about CA glue. It really does bond skin together. Really, really, really well. Acetone is the answer. The picture police will have to forgive me I was not thinking and did not take a picture of my index finger and thumb stuck together. What was I thinking?
This next picture shows the back of the outside right piece and the back of my T-bolt. Mr. Maskery uses a lever to put pressure on the plate to create the fit of the fence. However, I did not have a lever so I am counting on the snug fit of the fence from the “joinery” and the small about of pressure that tightening the knobs will create.
After the fact, my screw does little to nothing as it is not the right design to move out and against the pressure plate. When I tighten the knob it just pulls into the right outside piece. So this is my mistake. You have to create pressure – my set up does not create that. However, my fence is snug enough that this may not present an issue. I’m no engineer.
The left piece has a 1½” wide strip attached to the bottom that allows for using a push stick safely when ripping thin strips of wood. I attached these with screws through the back.
The top is just laid on top of the three pieces and screwed to the left and to the outside right side piece. I clamped the three pieces together before screwing the top on – this made for a pretty snug fit.
That’s all there is to it.
I cut several pieces to test this outfit and it works as advertised. The material moves smoothly through and I have to admit it actually “felt” safer.
Now the questions: As to the outside “waste” portion that is cut off. As I understand it, this portion of the board is generally not what gets kicked back at you. Is this just physics or because the featherboard (provided one is used) keeps it from coming back? Seems to me that if the waste portion curls in when cut and touches the blade that the teeth coming out of the back of the throat plate would catch it and pull it up and over the featherboard and still throw the wood back.
Seems to me a good blade guard would keep most kickback from actually getting all the way back to the user as it would act as a very loud brake when the wood hits it. The kickback would probably break the guard, but still protect you. Is that right? Just another reason to use a blade guard?
Is this a device that you think you would use? I can see where it would come in handy.
Thanks for looking. Hope this makes some sense. I really would value any comments or suggestions.
-- "Our past judges our present." JFK - 1962; American Heritage Magazine