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Forum topic by Dabcan posted 08-15-2014 12:53 AM 673 views 0 times favorited 19 replies Add to Favorites Watch
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Dabcan

99 posts in 1360 days


08-15-2014 12:53 AM

Topic tags/keywords: table saw full kerf blade belts tension

I’ve got an old unisaw with three belts. It was sitting for a long time before I got it, and the belts are stretched so that when you turn the blade by hand, it always returns to the same place where the belts want it to go. I never thought this was an issue as I had good cuts with my full kerf Forrest blade (which is very dull).

I got a Freud 1080 thin kerf blade, which is really well reviewed and it produced horrible cuts. I returned it for another blade, and I have the same issues. I can’t believe that I could have got two bad ones in a row, I have never seen a bad review period.

Is it possible the belts are causing the problem? If so, why doesn’t it affect the full kerf blade?

-- http://www.craftcollective.wordpress.com


19 replies so far

View knotscott's profile

knotscott

5515 posts in 2064 days


#1 posted 08-15-2014 09:18 AM

If there was a problem with the blade in manufacturing, it’s very possible to get two defective blades if they were from the same run. If purchased from the same store, it’s very likely that they’re from the same run, so it’s possibility.

-- Happiness is like wetting your pants...everyone can see it, but only you can feel the warmth....

View Dutchy's profile

Dutchy

538 posts in 857 days


#2 posted 08-15-2014 10:08 AM

There are a lot of issue,s who can cause a bad sawing result, but believe me it isn,t mostly the blade. The tolerance of most well made sawblade,s are very high.
But thin blades need a very precise machine. What is the diameter of the flanks (For good working mostly this has to be at least a 1/4 of the blade diameter, in your case 2,5” but 1/3 is better, especially by thin blades), Are the flanks flat and are they clean. The max swinging of the flanks has to less than 0,01 mm. What is the sawblade speed (revolutions per minute). When this is all oke it is a lot more diffecult to find the problem, but I would search the problem in the machine and not in the blade. Also it is important to know how many teeth the blade has and your wood thickness It’s worth to mention that a full blade has less wobble. The same as by wood, how thinner how more instable. And yes also bad belts can cause fibration with lead to bad sawing results.

-- My englisch is bad but how is your dutch?

View Fred Hargis's profile

Fred Hargis

1890 posts in 1182 days


#3 posted 08-15-2014 01:02 PM

When you say “horrible cuts” is that bad splintering on the wood, rough cut surface, or some other problem?

-- Our village hasn't lost it's idiot, he was elected to congress.

View Dabcan's profile

Dabcan

99 posts in 1360 days


#4 posted 08-15-2014 01:18 PM

Rough cut surface. I tried varying the feed speed without much difference.. I am thinking the flat spot on the belts is not helping the problem

-- http://www.craftcollective.wordpress.com

View Fred Hargis's profile

Fred Hargis

1890 posts in 1182 days


#5 posted 08-15-2014 01:45 PM

The set in the belts isn’t helping…..but I’m doubtful they are causing the problem. Is possible that when you first changed the blades a piece of something got onto the inner arbor washer (cause blade wobble)? If you put the dull Forrest back on does it still cut relatively well? I suppose the set in the belts can cause a thinner blade to vibrate more than the full kerf…...but that really seems like a stretch.

-- Our village hasn't lost it's idiot, he was elected to congress.

View Don Broussard's profile

Don Broussard

2033 posts in 940 days


#6 posted 08-15-2014 02:29 PM

I have a 1947 Unisaw that set up for many years before I got it. I shifted the belts so the set on each belt was in a different position. I don’t know if it affected the cut, but it was not as noisy. I did end up replacing the belts with a matched set.

I don’t have a clue about what’s going on with the full-kerf versus thin-kerf blades. I would try ruling out Fred Hargis’ suggestion about the arbor washer though.

-- People say I hammer like lightning. It's not that I'm fast -- it's that I never hit the same place twice!

View Dutchy's profile

Dutchy

538 posts in 857 days


#7 posted 08-15-2014 04:50 PM

In my first post I talked about flanks, what I ment is in englisch called arbor washer.

-- My englisch is bad but how is your dutch?

View Dabcan's profile

Dabcan

99 posts in 1360 days


#8 posted 08-15-2014 07:00 PM

I’ve tried putting the old blade back on and it still works fine. The arbor washers are clean and in good shape. I think I will replace the belts and return the blade for a full kerf one instead.

-- http://www.craftcollective.wordpress.com

View CharlesA's profile

CharlesA

1692 posts in 486 days


#9 posted 08-15-2014 07:08 PM

Get what works for you, but I can’t imagine it is the “thin” in the thin kerf blade that causes that kind of problem. Maybe there was a bad run . . .

-- "Man is the only animal which devours his own, for I can apply no milder term to the general prey of the rich on the poor." ~Thomas Jefferson

View Fred Hargis's profile

Fred Hargis

1890 posts in 1182 days


#10 posted 08-15-2014 07:35 PM

Try the Goodyear AX-24 belts. Those are cogged and a lot smoother than the OEM bekts.

-- Our village hasn't lost it's idiot, he was elected to congress.

View MrRon's profile

MrRon

2864 posts in 1932 days


#11 posted 08-16-2014 03:35 PM

Are you sure the nut on the arbor is not too tight? Over-tightening the nut can cause a thin kerf blade to become “dished”.
As far as belts are concerned, all three belts should be matched. That is, the amount of stretch between individual belts should be in accordance with the Rubber Manufacturers’ Association (RMA). Gates, series V80 belts meet and exceed the standard and are highly recommended. Don’t use the link belt type. They will not maintain even tension. They are only good for single belt use, not multi-belt.

View Dabcan's profile

Dabcan

99 posts in 1360 days


#12 posted 08-16-2014 06:28 PM

yep not over tightened. thanks for the info on belts.

-- http://www.craftcollective.wordpress.com

View runswithscissors's profile

runswithscissors

1017 posts in 714 days


#13 posted 08-19-2014 06:42 AM

Following up on Mr. Ron’s point: The blade flange on the Unisaw is dished (that is, has a slightly raised rim). The arbor washer must also be dished, with the hollowed out part facing the blade. I had a similar problem to yours (lost washer, of course), when I tried using a flat washer. Tightening the nut distorted the blade. So I made my own hollow washer buy cutting one of the right diameter with a hole saw (same D as the arbor flange), and hollowing it with an angle grinder. Held the washer in a vise, of course. The steel was 3/16”. Eliminated the problem. Those washers and left hand threaded nuts are very hard to find nowadays, especially from Delta.

I agree a TK blade would distort much easier than a FK.

View OldWrangler's profile

OldWrangler

640 posts in 283 days


#14 posted 08-19-2014 07:53 AM

A 20+y/o belt on my Rockwell Contractors saw sat for too long and the belt took a set. I could hear the lopeing sound and the saw was noisy. On a suggestion from a LJ buddy, I switched to a link belt. Problem solved. Noise level dropped in half and the saw cut like new. That was the best money I have ever spent on up grading a machine. Woodcraft, Rockler, Amazon and others have the belts
They ain’t cheap but worth twice the price.

-- I've had trouble with both wives, the first one left me and the second one won't.

View MrRon's profile

MrRon

2864 posts in 1932 days


#15 posted 08-19-2014 05:41 PM

A contractors saw only uses a single belt. Link belts are fine there, but link belts are not suitable for multi-belt saws.

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