arbor runout

[skeezics]

how much runout is acceptable on an old unisaw? if im doing it right [could also use some instruction with pics ] im showing .007 - .008 seems a bit much at the arbor. thanks.... skeez

[Leon]

Sounds like a lot to me. Remember that will be greatly magnified at the teeth on the blade. Forrest claims .001" on their blades.. For that benefit to happen on your saw the arbor run out would have to be less than .001". Mine is close to .0005.

[skeezics]

thats what i thought but as i said im not sure i am doing this right. i picked up a cheep dial indicater and a magnetic base from HF. probly my first mistake! i set it up to touch the threads of the arbor and added some presure to it to get an acurate starting point then hand turned the blade. maybe i should remove the blade and hand turn the arbor using the belts or pulleys? this would put the indicater closer to the bearings so im guessing that would be more accurate. i get a very slight wobble from the blade on shutdown but its a cheep thin curf piranna so im sure that is part of the problem. if i drill a 5/8 hole in a piece of 1/2 inch plexiglass or lexan would that give me a better picture? [no i would not be running the saw like that of coarse] thanks... skeez

[The Davenports]

Tirst step is to get the indicator tip OFF the threads entirely...check right next to the arbor flange, where there should be a straight 5/8" diameter. Also, be sure to check the face of the flange, too. In some ways, that is more important the the arbor concentricity because if thearbor is out by .003" at the arbor, it's also .003" out at the working part of the blade. But if the flange is .001" out near the arbor, the blade will be out by closer to .010" at the rim of the blade.

Luck

Mike

[Mark]

Your right, your not doing it right.

[skeezics]

could you elaberate? where might i find the correct way? skeez

[Preston Andreas]

You want to check the flange near the outer rim. Runout should be .001" - .002". Turn the arbor by hand. If there is any roughness or play, replace the bearings. That also could give poor runout on the arbor.

Preston

[skeezics]

did that and came up with .004 - .006. best i can tell!!! i dont see so good these days. lol... i replaced the bearings already so im wondering if the arbor may be bent or the flange not flat. but as i say im not too sure about this procedure. this is a very old saw and has seen some hard use but seems to cut well with a frued glue line rip blade. maybe i sould not be fiddling with it. sometimes things should be left alone. curiosity got me though. skeez

[nospam_coloradotrout]

here's how i did mine..

screw board to miter guage; screw dial indicator to board with rod extending out into path of blade.

oh.. cut off the board if it's extends into the blade; get tight fit of miter guage in miter slot

slide "assembly" into blade; raise/lower blade until the dial indicator rests on the outside of the blade, but not the teeth, just where the metal of the blade seems to be smooth.

rotate the blade a full 360.. read min/max on the dial. your arbor runout will be much less than the actual blade runout. my blade runout is .002; so I have to believe my arbor runout is .001 or less.

getting down to the arbor itself will probably be a pain. if possible, try to find a blade or vibration damper that you know has very low runout

clean dust and gunk off the arbor and blade

[Bridger]

some places where the dial indicator will yield interesting/useful data:

1) the flange. what you are measuring is how square the flange is to the axis of the arbor. the plunger of the indicator should be parallel to the arbor with the tip riding near the outside rim of the flange. measurement is indicated variation in one revolution. 2) the blade. what you are measuring is the total runout of the blade and flange. if both have runout the reading you get will change if you loosen the arbor nut and rotate the blade without rotating the arbor. the plunger of the indicator should be parallel to the arbor and the tip should be near the rim of the blade. be careful not to allow the tip of the indicator to fall into the gullets or anti vibration slots of the blade. measurement is indicated variation in one revolution 3) the miter slots. what you are measuring is the squareness of the miter slots to the arbor. mount the indicator to a tight fitting bar in the miter slot with the plunger parallel to the arbor and the tip reading the rim of the saw. choose a clean spot on the blade and draw a circle of 1/2" or so on it with a sharpie. raise the blade to full height and rotate it so that circle is at the front of the saw. take a reading inside the circle. rotate the circle on the blade to the rear and slide the indicator to follow it. take a reading here. measurement is the difference between the readings.

Bridger

[Preston Andreas]

Bridger has a good point, the dial indicator should be as nearly parallel to the table as possible when checkin the arbor runout. You might also check the outer rim of the blade, but be wary of any dust between the blade and arbor/nut and remember, the runout on the blade may accentuate or dampen the runout reading overall depending on how the arbor and blade line up to each other. You can take a reading on the blade, rotate it A 1/4 against the arbor and get a wholly different read out.

I talked to a Delta tech sometime back. He said they were using a different method to weld the flange to the arbor than they used when my arbor was manufactured. He said the runout in general was less than with the older arbors and you should now expect 0.002" or less runout on the arbor flange. You might call Delta and check that out.

[skeezics]

ok im understanding this better now. .003 - .004 on the flange. i did this by mounting the magnetic base to the inside of the cabinet so should be accurate.

yep see above.

the freud glue line rip blade has so many slots cut in it that it is hard to get a reading i feel is acurate. i have some lexan in 1/2" size so i may try making a plate to check further out from the flange. the flange was rough too so i cleaned it up with an old course stone. that got me to the .003 -.004 reading. this is more than most are getting but it may just have to be as good as it gets. this saw was made in 1948 and has been used in a cabinet shop environmentso......

i believe im real close to square with the blade but ill check further when i get the chance. thank you for the info. the saw cuts great. what caused concern was the slight wobble during shut down. the new glue line rip blade cut down on that somewhat. the new beismeyer fence improved this saw a LOT. know anybody that wants the original fence?

again thanks. skeez

[skeezics]

my arbor flange screws on with fine threads. no welding on this one. i was trying to figure a way to maybe flaten it. but i havent figured a way to do it acuratly enough while still mounted to the saw,. if i could do that theory say it could be gotten perfectly flat no matter how out of round the arbor may be. hmmm.... something to think about? skeez

[Bridger]

when it's all said and done this is the where cut quality happens. if the flange is out of true a perfect blade will blow chipsout of your workpiece, and if the blade has runout a perfect flange won't correct it. however, it is possible to oppose equal amounts of runout between the blade and flange to cancel them out. it's kind of fiddly, and a kludge fix, but doable.

as far as indicating the rim of the blade, there is no need for the blade to be rotating while you are taking the reading. choose a spot a little inside the gullets. mark a tooth with the sharpie so you will know when you've gone all of the way around and take a reading. with one hand retract the plunger of the indicator while with the other hand advancing the blade past the slot. let the plunger back to the blade, take the next reading, repeat. just make sure you don't move your indicator holder setup.

the lexan is unlikely to be accurate enough to give you meaningful results.

a machinist can true your arbor, but you'll have to dismantle the saw to do so. if you do go this route, take the opportunity to replace the bearings. if the rest of the saw is in good shape it might be well worth it.

Bridger

[Keith Carlson]

Someone else here probably has experience doing this, but wouldn't there be a way to flatten the arbor flange while it's spinning? I suppose there's all kinds of safety precautions here, but you've already got it spinning, almost as if it were on a lathe. Well, faster than a lathe. And if there's not much material to remove, you might even be able to use some abrasive paper backed by a flat flat board.

I would think no matter what you do, you'd reduce the runout. You'd have to be careful to not make it slightly dished, or cone-shaped, which might bend the blade when the nut is tight.