Old Delta jointer blade adjustment - how good is good?

[Tom Dacon]

A friend of mine has an old 8" Delta jointer, circa 1952 (the old Crescent

4-blade machine), on which we've been trying to install sharpened blades, and we've been having a hell of a time getting them adjusted.

For starters, there are a couple of critical tools missing - the special t-handled wrench for moving the blades up in the holders, and a small jig to set the height. A screwdriver works sort of OK as a substitude for the wrench, and we've been using a combination of a straightedge and a depth micrometer across the two tables, which we adjusted to the same height with the straightedge.

The problem, of course, is that you can chase your tail on a blade for a couple of hours, levering it up with the screwdriver, tapping it down with a soft metal rod (taking the honed edge off the blade after a while where you tap it, naturally). A few thousandths too high, then a few thousandths too low, back and forth, up and down. Finally you decide it's good enough and tighten down the wedge nuts, and the wedge nuts raise the blade back up a thousandth or two or three, generally not the same on both ends of the blade, because you can't keep the throat block up tight against its pins while you're fiddling with the blade height. Naturally, on a machine this old, there are no springs to hold the blade up or micrometer bolts to fine-tune the blade height.

After about four hours of levering and tapping and cursing, we got all four blades as good as we thought we could get them without losing our minds. On one end of the cutter head, the difference between the highest and lowest is

0.004 inch, and on the other end the difference is 0.003 inch, with the highest blade the same (thank god) on both ends. We took a pass with an already-smooth piece of cherry that had just been planed in a well-tuned planer, and I have to say that it felt pretty good.

But I'd like to think that we should be able to get the blades the same height within a thousandth, and ought to be able to perform the whole operation in no more than a half hour at worst.

Before you ask, my buddy borrowed a magnetic jig for adjusting planer blades, but we couldn't get it to fit on the cutter head of this particular machine. I've also been to the Old Woodworking Tools site and studied the Crescent section for tips. A Google groups search turned up not too much except some belly-aching about adjusting similar machines.

What do you think? Did we get it as good as it needs to get? Better than it needs to be? How would you do this in a half-hour instead of a half-day?

Thanks, Tom Dacon

[Jamie Norwood]

Here is how I set new blades:

I have an aluminum bar 1/2" square and about 12" long. I lay the blades in the holders and adjust by snugging them lightly with the gib screws and then use a piece of maple to tap them even with the outfeed table. This is rough setting.

I then take the aluminum bar and lay it across the knife near one end of the knife with about 8 inches on the outfeed and the other 4 over and past the cutterhead. I mark the outfeedtable where the end of the bar is with a sharpie to mark where it starts moving. Rotate the cutterhead in the cutting direction to lift the bar (if it doesn't lift the bar then lower the outfeed table until it does) with the cutting edge and keep rotating until it drops the bar further down the infeed table. Now mark the end of the bar on the outfeed table again. Take a combination square and square these lines across the width of the table. Now move the bar to the other end of the knife and set the bar at the starting position and rotate it and see if it drops at the same mark as the other end. If it comes up short the knife needs to come up at that end, if it goes past then tap the knife down with a maple block. Continue with the other knives. When they are all even raise the outfeed table until the bar is just grazed by the knife. Test cut a board and check for a concave or convex edge. Raise or lower the outfeed table to fix either problem, the infeed table only affect depth of cut. This will get your knives close enough for any work you need to do on a jointer.

Jamie

Tom Dac>A friend of mine has an old 8" Delta jointer, circa 1952 (the old Crescent

[George]

If you don't have knife lifts, run a piece of twine side to side to keep 'em elevated until they're even with the outfeed table. You can squash slightly more easily than you can elevate. The outfeed table is all that counts, not the dumb spider gage they give you. When the blades are secured, soak a bit of WD40 into the twine and slide out.