Yes there ways, though not easy.?
BUT this is the MOST important factor in your saw cutting square (esp vertically down).? So much so, that you have to fix it or get rid of the saw (unless you don't care whether it cuts square, but then you'd ever want to fix it).
To cut square the pivot shaft MUST be parallel to the workpiece in both front elevation (i.e. horizontal to the base of the vice - not easy to measure, therefore not easy to set correctly) AND in plan view (i.e. looking down from above - effectively parallel to the back of the vice, which is always easy to do).? The back of the sawblade also has to square to the pivot in front elevation and plan view.? Although they're related, they have different adjustments available and don't really concern you when re-bushing the pivot.?
Because the pivot shaft is set-screwed to the sawframe side of the hinge, the wear is only in the ears of the base. With luck you may need to only do the bush next to the blade, which is normally the one that wears first.? However ANY slop on the bearings translates to un-square cutting. Turning the pivot shaft end for end may get any shaft wear into places it doesn't matter. If you want your saw to cut square within 'thou' the pivot shaft alignment must be parallel within the same amount.? The 2 are flip sizes of the same coin.
The ways I know are:
1. Milling off the ears and bolting on replacement pillow block style bearings -? has been done and there are photos in the Photo section of the site. The pillow blocks need only be square steel bar reamed to 15mm diameter of the pivot shaft. You can ensure parallelism of the bearing mount to the saw base when setting up in the mill.??
2. If you don't have machine tools, then drilling and/or filing out the base ears until they're sloppy enough to accept a bronze or brass bush will work.. Because the worn hole is oval, drilling it out dead size for the bush may not get it It is aligned with vice base and back.? Try drilling dead size and measure the alignment before easing it open any further. You can ensure alignment in a sloppy hole by using 3 set-screws in each ear (one up from underneath and the other 2 in from the back and front).? Once aligned the gap between the bush? and the cast iron base ear is injected with epoxy resin from a hypodermic syringe through an additional hole from underneath so it flushes the air out. An o'ring on the shaft either side of the ear will stop the epoxy squishing out the sides. Suitable diameter bushes are available from engineering supply places like McMasterCarr.com, though you'll have to cut them to length.? You might get lucky and getting a bush that's twice as long as you need and can just cut it in half.??
The only relatively simple method of measuring whether the pivot shaft is parallel to the vice base casting is to cut some 4'x1" soft pine or fir joinery timber (dressed all sides, it winds up under size but that doesn't matter):
- mark one of the 1" edges with a pencil or marker pen (so you know which way up the piece was when cut)?
- grip it 4" face vertical in the vice, so 1" edge sits flat in the vice base, with about 1/4" ready to be cut off and mark line upwards (get used to doing it the same way all the time, as you will have to do it many times before its right..
- ?cut off the end of it by lowering the saw through the wood by hand so it take at least 10-12 sec to make the cut (the blade teeth are rasping the wood to the shape the pivot geometry makes it).? Discard this piece.
- ?turn the wood over 180 degrees (now mark line is against the vice base), again about 1/4" to be cut off, exact length is not important.
- ?cut the piece off in same 10-12 seconds as before.? This is the test piece.
- ?measure the thickness of each end (with digital calipers is best) and subtract one measurement from the other??
- ?ONLY if the pivot shaft is parallel to the vice base will the measurements be the same and the difference between them zero. Otherwise it will be tapered, either toward the mark line or away from it, depending on which end of the pivot shaft is higher than the other.
- less than 25thou" taper is ok for most general engineering work, less than about 10thou" is good for accurate work but is not worth adjusting further as you're just as likely to overshoot as much in the opposite direction, obviously parallel is best.
Hope it helps - jv
