July 11, 2009
Leveling throat plates on a saw
When making scale models, engineering models, birdhouses or dollhouses I want precision cuts to a particular size that have accurate angles on the sides of the cuts. It can take a lot of fussing and a lot of patience to make that happen. Many of the cuts I make are done on a 10 inch table saw, I want that saw and my small table saws fine tuned so that what I get is accurate to the dimensions I am trying to achieve. It all starts with a good table saw tune-up but that is not the subject of this blog.
To get an accurate cut it is essential that the throat plate be dead level to the top of the table saw. If your throat plate is too high then the edge of the wood sitting on it will slope down towards the fence and your intended 90 degree cut will end up being made at an angle. If the throat plate is too low you might get sloped cuts on short pieces or the wood might hang up on the back edge of the plate opening and mess up your nice cut. If you are trying to accurately cut a groove of a particular depth it too might turn into a mess.
Every saw is a little different, the one I am working on today has small tabs extending into the opening for the throat plate. There are hex head screws in the throat plate that rest on those tabs. I fiddle and fuss and fuss some more back and forth between the screws until I get it just right. To check if it is level I use a steel rule or some other object that has a long straight edge and sharp corners. If the corner hits onto the edge of the plate or the table top I know the plate is not perfectly level so I tweak the height a little more until I feel nothing hitting. Every time I change the throat plate I have to be sure there is no sawdust on the adjusting screws or on the support tabs. Just that little bit of debris will mess up the level. I always grab a straight edge and check when I change plates or if I have been cutting for a long time as vibration from the table saw can move those screws.
Some table saws including miniature saws don't have adjusting screws. If there are no ajusting screws you will need to resort to using shims of metal, paper, plastic, cellophane tape, whatever you can find that works is OK to use. If your throat plate is too high to begin with you will have to make new ones or reduce the thickness where it rest on the edges of the opening. Making your own throat plates is a good thing to learn. I will cover that in another post sometime later.
A lot of the throat plates for miniatures saws are warped to begin with. You might have to back them up with another layer of material to stiffen them. Of course you don't want that layer to touch onto the recessed ledge the plate rest on and it can't be so thick that the saw arbor hits on it and bends the plate upwards.
Want a dead flat plate on a 4 inch table saw that needs no fussing? Then buy a 4 inch table saw from Byrnes Model Machines, he has taken the time to match the recess in the table top to the thickness of the throat plate. There is a link to Jim Byrnes in my file of links on this blog.