drive belt jumped track; why? - Woodworking Talk - Woodworkers Forum
 
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post #1 of 12 Old 09-18-2020, 02:03 PM Thread Starter
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drive belt jumped track; why?

Delta Hybrid TS 36-714, left-tilting cabinet saw from 2005.

I'm getting ready to make a riving knife and noticed that the drive belt has moved over two ribs on the motor pulley, and one on the arbor pulley.

Why would this have happened? Shafts not parallel? Pulleys not aligned with one another? Something else?

In the 2nd pic you can see no wear polishing in the two outer grooves of the pulley, and bight metal from wear on the inner, non-grooved portion, as well as worn ribs on the belt. Clearly it has been so for a long time, maybe since it left the factory?

No pic possible of arbor pulley, but it has jumped only one groove in the same direction as the motor.
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post #2 of 12 Old 09-18-2020, 02:17 PM
where's my table saw?
 
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Do a check up ...

It's time to check everything out like pulley alignment for sure, and whether one could have shifted on it's shaft..... and a new belt. No need for OEM Delta belt, just get the number from it and do a online search.


If the saw was ever completely stalled and then allowed to start spinning again, that could have caused the belt to jump those small grooves, I donno?


Or if the saw was ever tilted such that the belt tension was released, another potential cause. But, typically the belt is under sufficient tension from an fixed adjustment, unlike gravity tensioners in the old days.

The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)
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post #3 of 12 Old 09-18-2020, 05:38 PM Thread Starter
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Thanks,

I hadn't thought of tilting as the cause. Yes, it is gravity tension setup. Might even have happened when I first got the saw and, with a friend, had to man handle it out of the back of my cargo van. We might have tilted it on its front side allowing the motor to pivot toward the arbor. That could account for there being no wear polishing on two of the pulley grooves too.

I have a new belt on order from Renovo Parts.

While on the subject, you saw my riving knife thread, I think. Near the end of her video, the YouTube poster had to grind a notch apparently about 1/4" deep in the cast iron motor mount, to allow clearance for the lower end of the RK when the blade is all the way down. The OEM belt is 27", which has the two shafts about a foot apart as the motor hangs from the arbor shaft.

Do you think I could install a 28" belt instead (Renovo has one), so the motor would hang 1/2" lower to allow clearance without grinding the mount?

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post #4 of 12 Old 09-18-2020, 07:06 PM
where's my table saw?
 
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It would be a better solution IF .....

It's worth a try for sure. A 1" difference in OAL is only a 1/2"

difference in actual distance between centers, so it may work. Try It!

The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)
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post #5 of 12 Old 09-18-2020, 07:26 PM
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while you're that deep into making the riving knife, I'd suggest drilling/tapping some holes for set screws to permit 3-axis adjustments.
otherwise you'll need to use shims around the edges.


also check the thickness of the knife to be sure it'll be thinner than your narrow kerf saw blades.
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post #6 of 12 Old 09-19-2020, 12:21 AM Thread Starter
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I use only 1/8" kerf blades, but if for some reason I ever get a thin kerf blade, I could make a 3/32" knife for it. It will be removable for when I use the stacked dado.

Can you elaborate on how I might use set screws? Sounds intriguing, but I can't picture what you mean.

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post #7 of 12 Old 09-19-2020, 12:30 AM Thread Starter
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Quote:
Originally Posted by woodnthings View Post
It's worth a try for sure. A 1" difference in OAL is only a 1/2"

difference in actual distance between centers, so it may work. Try It!
What test would you use to verify that the longer belt provides enough tension? Since motor mount and arbor tilt together, would I be right in assuming that 45ļ tilt would be the likeliest setup to fail?

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post #8 of 12 Old 09-19-2020, 08:57 AM
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...using set screws


think of it as making a three legged stool - they are "adjustable feet" - allows you to fine tune the position of the knife to the blade
the knife needs to be parallel to the blade horizontally, and vertically, and centered to the blade.
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post #9 of 12 Old 09-19-2020, 10:42 AM Thread Starter
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So, you are talking about where I mount the 1/4" thick extension plate to the arbor-raising casting? That is an interesting idea. I expected to have to use shims under the mounting screws to get that coplanar with the arbor flange.

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post #10 of 12 Old 09-19-2020, 03:09 PM
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multiple options - you'll need to decide which works best with the space constraints....


set screws on the 1/4 plate - since that heavy plate doesn't need to move once "perfectly set" shims would be an easy way to make it co-planar "in distance."
just make it co-planer for the thinnest kerf distancing - otherwise if you later go thin blade, you'll need to contact Star Fleet for some anti-shims. set screws there could accommodate horizontal and vertical - using three to adjust the distance would be more tricky. note that the blade would have to be dismounted for adjustments - that means lots of trial and error, since you don't have the blade for immediate reference points....



other option: mount set screws tapped in from the back side of the 1/4 plate - bearing directly on the the knife. use longer set screws so you can use a nylock locking nut to ensure they don't move / vibrate loose in operation.


personally, having diddled and fiddle with lame mounting adjusts on a commercial saw, I like the second option - simple & direct effect adjustment.
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post #11 of 12 Old 09-19-2020, 05:14 PM Thread Starter
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Quote:
Originally Posted by TomCT2 View Post
set screws on the 1/4 plate - since that heavy plate doesn't need to move once "perfectly set" shims would be an easy way to make it co-planar "in distance."
just make it co-planer for the thinnest kerf distancing - otherwise if you later go thin blade, you'll need to contact Star Fleet for some anti-shims. set screws there could accommodate horizontal and vertical - using three to adjust the distance would be more tricky. note that the blade would have to be dismounted for adjustments - that means lots of trial and error, since you don't have the blade for immediate reference points....



other option: mount set screws tapped in from the back side of the 1/4 plate - bearing directly on the the knife. use longer set screws so you can use a nylock locking nut to ensure they don't move / vibrate loose in operation.


personally, having diddled and fiddle with lame mounting adjusts on a commercial saw, I like the second option - simple & direct effect adjustment.
Now I understand what you are saying. There will be a lot of trial and error with the extension plate; shim, tighten bolts, put on blade, check alignment; then remove blade, unbolt, add/subtract shims, re-bolt, re-install blade, check again; rinse and repeat until it is right. Tiny shims on the mounting bolts of an 11"-long extension plate may produce big movements out at the end. I'll have to think about that when choosing the mounting bolt pattern while fabricating the extension; put them as far apart as possible.

Fortunately for me, my 1/4" extension plate mounts 7/16" behind the arbor flange, so once the extension plate is coplanar with the flange/blade then an 11/64" shim at the end would bring the inner edge of the RK in line with the inner edges of the carbide blade teeth. Would work for both thin kerf and full kerf blades. I would need only to change from 3/32" RK to 1/8" RK.

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post #12 of 12 Old 09-19-2020, 05:48 PM
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The riving knife need not be zero clearance.....

Of course the blade kerf should be made to suit the kerf of the blade for reduced tearout. The riving knife plays no other roles than keeping the kerf from closing after the cut AND to maintain the lightest/slightest pressure of the workpiece on then fence to prevent a "up and over" type of kickback.

The insert should be as flush as possible with the table surface to avoid a feeding stoppage and any rocking of the workpiece during the pass. This is where the set screws will help to level it out. My saw has cast in "pads" for the insert leveling screws as do most saws I've seen.

The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)
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