homebrew table saw?

"tony" wrote in news:2YhMb.94447$_P.3563934 @news4.tin.it:

Ignoring the construction requirements or safety issues here's some regular table saw info and a few thoughts for comparison.

What diameter blade do you intend to use? the standard 10" tablesaw blade has a 5/8" arbor hole.

Blade size will determine the rotational speed needed. Roughly a 10" blade is 3000rpm a 7 1/2 is 4000-5000.

My 3hp Powermatic 66 Arbor is 1 3/4 diameter for the man section between bearings, taken down to 5/8 at the drive and blade end. I think you need to have at least a 5/8 arbor and would probably think about support between each blade if you're planning on two or more blades.

Each blade will need a splitter behind it to avoid the cut wood kerf closing or binding on itself or adjacent blades. Any binding during cuts on a single bladed saw can get interesting, let alone a gang saw.

Adjusting height; if you've not seen one the height and angle adjustment on a cabinet saw is about 250lbs of cast iron and it's big and very strong. I'd suggest instead of trying to engineer that from stratch you maybe fixed mount the arbor and adjust the height by adding thickness to the worktop in the form of sheet ply or mdf or something. Just screw down a whole sheet over the entire worktop with slots for the blades and splitters to protrude only and so reduce the effective height of the blade.

Think about infeeding and outfeeding this wood and how to use hold down's like finger boards to locate this stuff bothe side to side and down in front of the blade. If you're cutting fixed dimensions the fence can just be a 2x4 screwed in place.

good luck..

The high volume wood plants use gang rip saws all the time. Huge feed rates. The plant I visit regularly hasn't let near their rip saws yet, plenty of time spent in the moulding department though! LOL!

You aren't going to like a 1/2" shaft. Not enough beef. If it doesn't vibrate it will bend on the first jam. But why 1/2"? why not move up to 5/8" and use 7-1/4" blades that are designed for portable saws. Lots of options from $1/blade to whatever. Even

You will need some machined spacers to hold the blades apart. these are what drives the blades as well as stabilizes the sides to avoid runnout. There also needs to be some adjustment (or spares) since the kerf versus blade thinkness varies with different blades.

I'd toss out a guess at 1 hp per inch of cut in hardwood. ie 2" in one cut or 1" in 2 cuts. Southern yellow pine almost qualifies as hardwood, some softer stuff would require less. I suspect you could get by on less HP but a production shop pushes on it. A nice 3hp TEFC motor should run 6 blades all day long.

If at all possible, design it to run with a dual belt or at least with pulleys at least 2-1/2" in diameter. Use cast iron pillowblocks and double sealed ball bearings.

To adjust blade height, mount the whole arbor (and perhaps the motor) on a SOLID frame with a couple pivot points lined with brass bushings. Think heavy as in 2"x2"x1/4" wall square tube as a starting point.

Safety is a problem, this system will just love to kickback. Power feed is a must. the other issue is how to get the last boards out when you try to shut it off. Or you may not care, just run in a sacrifical board, shut it off with the board in place. Plan on using a sacrifical zero clearance aluminum blade cover. Make up several, just toss when they get chewed up.

For production use you will need full guards, guard interlock, and a pretty convienient E-off button. Pine is going to have some big and loose knots, if they let go, things will get noisy in a hurry, especially if they twist and jam in between two blades.

Cheers.

t> greets all.

I'd approach this using the ultra-thin-kerf (approaching 1/16") blades sold for skilsaws. HP requirement is largely proportional to kerf width. There is some variety in hole size and blade diameter.

Power feed is pretty much mandatory, IMO.

You can cut down on the feed pressure by setting the blades for full depth of cut, so the direction the teeth are cutting is more straight down towards the table, instead of straight out towards the feed direction. Do you need to adjust the depth or can you just build it to cut only the max depth?

Shaft rotational shear, rigidity and tensile strength are all issues. Maybe a 1/2" shaft is OK for four 7-1/4" thin-kerf blades. No way for even a single 10" blade. Since there is a heck of a safety issue - I'd start with a 1" arbor, maybe 8 blades, 1" ought to allow clamping down tight enough.

The bushings need to be precision ground as to thickness so that they will tend to straighten rather than warp the arbor. Balancing shouldn't be an issue.

Power feed at a 6" per sec, thin kerf blades, ought to be OK with a true 1/2 hp per blade.

Just some musings. Don't sue me.

Bob

I used to work in the sawmilling industry and multi-rip saws were amongst the most dangerous. Beware of kickback. You will need a kickback preventer. This is a set of hinged teeth which only allow the wood to pass one way. When the wood flies back out of the saw, imagine where it will hit you! We used to cut small sections and they hurt. There were mentions in the trade press of injuries arising from these saws. Power feed is essential. You cannot hand feed that many pieces of timber. It will jam so design it strong, very strong or it will bend. How about looking for a used multi rip saw? Let others do the hard design work for you.

John

thanks for all the input, fellas. i'd already considered some sort of anti-kickback device.. but not the powerfeed. i'm leaning towards buying a little gangsaw, as suggested.. but just curious, what do powerfeed units look like for gang saws?

i'm imagining something akin to a planer.. but with no knives. two rubbered? powered rollers. yes? no?

thanks,

-tony

What I've seen ... having never been near one in operation... is a usual stock feeder, but with rollers wide enough to contact the full width of the stock. And rollers both ahead and behind the blades so that the board is at least relatively under control all the way through.

Adjust blade height with a table that raises and lowers , far easier the moving the arbors. A plywood or similar table would allow you to lower it over the blades producing a zero clearance setup.

Most blades today come with a 5/8 arbor Most gangsaw blades come with an even larger arbor hole an inch or more sometimes keyed/pinned. I would not design around 1/2" shafting.

HP per blade will be very dependant upon kerf, you want thin kerf blades .100-.125 at most with as few teeth as will produce an acceptable cut. I'd wager 8-10" dia x 18 teeth, a triple chip grind or at least a slight chamfer on every other tooths corners might cut a bit smoother, 20 degree hook angle.

For gaurding you want to enclose the entire cutting head so that you can't see the blades unless you lift it off or peek through the infeed or outfeed . You definately want powerfeed as it will also help prevent kickbacks.

Last I looked Tenryu and Matsushita made thin blades that could work for you.

Use 5/8" shafting, with snug fitting spacers bringing the unsupported shaft size up to 1.25 or more from bearing to bearing. As long as you keep the shaft in tension it cannot bend

On Mon, 12 Jan 2004 12:13:58 -0000, "John Manders" vaguely proposed a theory ......and in reply I say!:

I reckon the injury may well be the _only_ thing a-rising after that.

I was frightened by the idea of a conspiracy that was causing it all. But then I was terrified that maybe there was no plan, really. Is this unpleasant mess all a mistake?

I usually cut with the table all the way down for this reason. I believe the advice to "just leave one tooth showing" was written by lawyers.

My senior project at ODU: Google Groups, then "dgoncz" and some of: ultracapacitor bicycle fluorescent flywheel inverter Equipped with BoBike Mini removable child seat, too!

The blades on a gangsaw must be positively driven, that is with a pin or a key. If driven by friction, and one of the blades stalls, all hell breaks loose. You don't adjust the cutting height on a gangsaw. They cut all the way up to max capacity at the same setting. the powerfeed of course must be adjustable. If you have something like a Foley Belsaw planer you can set it up for gangsawing. Paul