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Page History: Unisaw Disassembly

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Page Revision: 2008/04/03 23:46


Keith Bohn posted http://www.owwm.org/viewtopic.php?t=13307

Starting of course means taking off the top unless you're really into pain. OK, it's mandatory onna 'count of you can't undo the trunnion brackets without the top off.

Next up you'll want to brush/blow/suck every spec of dust from the cabinet interior. This is because when you drop a part or screw you won't be having to fish around in the pile of crap in the bottom of the saw cabinet, unless of course you are into pain in which case I'll not discourage you.

Next up you'll probably find that the blade raising/tilt shafts are pretty skanky from years of pitch and gum building up. Get your favorite razor handle (I prefer the Titan (tm) brand).

http://www.amazon.com/exec/obidos/tg/detail/-/B0002JN34E/103-1475100-2041426

After you have razored off the heavy gunk you can go at it with the Scotch-Brite (I prefer the No. 8541 Doodlebug Brown Scrub 'N Strip Pads/the closest thing you'll find to an abrasive griddle brick).

]http://www.instawares.com/3M-Doodlebug-Brown-Scrub-n-Strip-Pad-8541.8541-3M.0.7.\htm]

Go across the shafts holding the Scotch-Brite two-handed like you were shining shoes.

(stops to wait while everyone Googles "Shoe Shining")

Now you want to inspect the shafts for dings or where some idjit took a vice grips to them because he was too brain dead to know better. File these down.

Once the shafts are brought back to smooth and shiney you can go about sliding them out. On the older machines the stop collars and worm gears were held in place with tapered pins. I like these better than the later roll pins. With both you'll need a proper pin punch but since these are the tools people should own (I have a single Starrett that makes my nipples hard but my more complete set are Enders and they are fine) you won't mind getting a set. With the tapered pins you can use a smaller than recommended pin punch but with the roll pins you really need to size the punch to match the pin otherwise you'll just curl over the ends and it makes for a skanky looking job. Take great care with the tapered pins to drive them out from the narrow end. The reverse will not free the pin and only lead to frustration and pain but again, you might like the pain so have at it.

I should note here that with the blade tilting shaft the shaft will have to be spun until the worm gear pin is horizontal (parallel to the floor). You'll notice a round hole beyond. It's there so you can drive the pin out.

So, as we said, be sure to mark everything as it's being taken off and pay attention to which way the pins went in if they are tapered and with the roll pins be extra careful to note the orientation of the collars and worm gears to the shaft. For some reason over the years there wasn't much in the way precision when these parts were machined and what you'll find is the drill holes won't be dead center and actually must mate back up with the collar put there at the time of first assembly.

One tiplette is to re-assemble some assemblies as you go along. For instance, with the shafts you can slide the collars, fiber washers and worm gears back on and set them aside. If you have tapered pins it's a good idea to drop them in their holes but there's no need to seat them. Just enough friction that they don't fall out on their own.

Also at this time you'll discover the fiber (fibre David) washers. Be careful that you keep them in the same order as they were found. Installing a too thick washer where it's not supposed to be will later cause you to exert too much force to raise/lower and tilt the blade.

Don't be afraid to flood the shaft with lubricant (I prefer Marvel oil but there are others) because this will make the job of removing the collars and worm gears easier. Also, you might find that some of the pitch and gum are close up to the collars and worm gears and this will temporarily slow you down. Once you clear that everything pretty much slides off with little resistance.

Something else you can try with parts that assemble to a shaft is to use zip ties (cable straps/ties/the uncomfortable style handcuffs that some po-lice departments use).

With the shafts removed you can go about removing the rest of the guts. There are three major components. The rear trunnion bracket that screws down to the rear right and left hand corners, the front trunnion bracket that screws down to the front right and left corner and the trunnion/blade raising bracket/yoke assembly. Once the trunnion brackets are loosened it all comes out. Be mindful that you don't allow the trunnion brackets to fall into the cabinet. Once free of the cabinet they are a free agent and are no longer fixed to anything.

Lay the trunnion brackets aside and take a look at the trunnion/blade raising bracket/yoke assembly. The yoke is screwed to the trunnions and aligned with steel dowel pins. Once the screws are removed you can tap it apart with a rubber mallet.

The blade raising arbor bracket is assembled to the yoke via a heavy shaft that slides through the yoke and into the motor bracket. There is also a pin (tapered on older models) that will need to be driven out. Once the pin is removed and the screws are loosened it pretty much spilling on some lubricant and using a rubber mallet to drive everything apart. It does not hurt to have a fat wood dowel as a drive pin for this.

From here it time to buff bright the machined surfaces, cleaning the painted surfaces and just getting everything clean. Paint is optional.

Once all this is done it's time to re-assemble which for the most part is a reverse order of dis-assembly.

Prior to this though you would be smart to bench assemble the entire thing to be sure that you have everything where it should be. Dis-assembling a freshly re-assembled saw from inside the cabinet isn't the funnest way to spend an afternoon, right David?

With everything bench assembled attach the blade rasing hand wheel and see how it operates. It should be smooth. If not and you find something sticky take a look at the fiber washers where the mate up against the collars. They might be too tight in which case you could have the wrong washers in the wrong spots. Try switching them around and maybe even thinning them with a piece of sandpaper taped flat against your bench.

Something to keep in mind when bench testing the assembly is the works aren't as they were designed, i.e., hanging from the cabinet so try to be sure that something isn't proper because it's sitting on it's back.

When you are ready to drop the whole thing back in remove the shafts while keeping all the collars, washers and worm gears in proper order.

Give all the machined surfaces that run in a machined surface a good lubricating. You can use paraffin (Gulf wax), chain lube, graphite spray or any of the fanci-schmancy products on the market for this. Try to avoid greases that attract dirt because this will just become a gob of crap later and could cause binding and your'e back here doing it all again.

Next take the front and rear trunnion brackets and seat them against the front and rear trunnions. Using both hands and being careful not to allow either bracket to drop away (and crash onto the floor thus breaking) lower the whole assembly into the cabinet. It will stay in place at this time but drop the cap screws through the holes in the four corners and run the nut up just this side of finger tight.

Start threading in the shafts adding the collars, washers and worm gears as you go.

Drop, or drive the pins into the collars but don't seat them yet.

Again, with the blade tilting shaft the shaft will have to be spun until the pin is near horizontal (parallel to the floor) to get it in. This pin will have to be fully set before testing as anything sticking too far proud of this gear will rub against the casting and you will either have a hard time tilting the blade or you won't be able to tilt the blade at all. File it down if necessary.

So eventually you'll get all of this to where you're pretty much all back together but everything is somewhat loose. At this point you can grab the front and rear trunnion brackets and squeeze them towards each other. Hard finger tighten the screws going through the trunnion brackets at the four cabinet corners and then give them all just enough wrench tightening that they won't go moving about. Now test everything to see how it operates. Locate and loosen anything that seems to be binding.

You might notice some back lash in the hand wheel(s). Back lash is a term to define how far you have to go in one direction with a gear engaged to the other direction and have the gear re-engage. In other words, you're raising the blade, you stop, reverse direction but for the first 1/8 turn it isn't engaged. That 1/8 turn is your back lash. This is caused by there being a space between the mating surfaces each side of the worm spiral and the rack teeth. There is always some back lash, just degrees of how much. My saw is 65ish years old and I'm not bugged by it's back lash. You might be. I guess you could take a chance and buy a new trunnion(s) and worm gear(s). Me? I live with it.

And in case you were wondering, anything with "zero back lash" is otherwise defined as "froze up", i.e., you have to have some back lash, otherwise the resistance of both sides touching would be too great to over come. In other words, zero back lash is a myth.

So where were we? Oh yeah, rinse and repeat with the lubricating, tweak things here and there and when you're satisfied it's the way that God, Al Gore and Herbert Tautz intended it to be. You can tighten down all the screws, tap in all the pins and pretty much get it buttoned up like it was race day. I've left out a lot about the itty-bitty parts but with an exploded drawing you'll figure that out.



Further discussions, and another post by Keith Bohn here: http://owwm.org/viewtopic.php?t=25715

I removed the tilt trunnion bracket and the entire guts came free just like I knew something.

This is the piece.

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