Read this if you made an A+ in geometry class

[Bill Bryant]

Bill,

The curve in the ZCI tells you that your blade or the trunnion is NOT lowering in a perfectly perpendicular plane with respect to the table top or the blade is bent.

Raise the blade to a height where the gullets are just clear of the table top and you can measure at that surface just below the gullet. Manually rotate the blade and check the run out on the blade. If you don't see a remarkable runout on the blade, then I'd bet your trunnion isn't lowering perpendicular to the surface of the table top.

The blade isn't bent. Or, at least, if it is, it's still inside .001 runout 3/16 from the teeth. I measured this by puting a dial indicator on it and slowly rotating the blade using the motor pulley. The indicator dial hardly twitches all the way around. Flattest blade I've ever seen. Ridge Carbide.

All comments continue to convince me that the axis of the blade arbor is not parallel to the axis of the height adjustment pivot. This is a can't fix it situation. It's a big piece of cast iron that's supposed to have had two perfectly parallel holes bored through it. But I'm pretty sure they're a few thousanths off parallel.

[Mike Marcade]

All comments continue to convince me that the axis of the blade arbor is not parallel to the axis of the height adjustment pivot. This is a can't fix it situation. It's a big piece of cast iron that's supposed to have had two perfectly parallel holes bored through it. But I'm pretty sure they're a few thousanths off parallel.

You should be able to confirm this by tilting your blade ever so slightly and see if the distance changes. See post #15.

[Bill Bryant]

Is it possible the axis of your blade arbor is not perpendicular to the axis of the blade raising mechanism.

If you've got access to a parts diagram, this makes communication much easier.

What I believe is that the hole in part #207 (elevating bracket) that part #202 (arbor shaft) goes through is not parallel to the hole in #207 that #205 (shaft) goes through.

[David Epperson]

All comments continue to convince me that the axis of the blade arbor is not parallel to the axis of the height adjustment pivot. This is a can't fix it situation. It's a big piece of cast iron that's supposed to have had two perfectly parallel holes bored through it. But I'm pretty sure they're a few thousandths off parallel.

Well yeah I tend to agree, that's the way it's sounding. It's not really a "Can't fix" situation, but it is one that you shouldn't have to fix. The fix involves some additional machine work on either the casting, the trunnions, or the mount.

[Mike Marcade]

If you've got access to a parts diagram, this makes communication much easier.

What I believe is that the hole in part #207 (elevating bracket) that part #202 (arbor shaft) goes through is not parallel to the hole in #207 that #205 (shaft) goes through.

Agreed. I attached the parts diagram for reference.

[Bill Bryant]

Mike, Thanks for posting the pdf file of the parts diagram. That's a real help.

[Mike Marcade]

Mike, Thanks for posting the pdf file of the parts diagram. That's a real help.

No problem. Best of luck to you getting Delta to fix this. It does make me question their quality control processes though.

[Rob Will]

This has nothing to do with the blade being 90 degrees to the table.

This has nothing to do with the blade being paralell to the miter slot.

So let's put the dial indicators aside for a moment.

Were this not a contractor's saw, the saw's top could be completely removed leaving the trunions and blade arm undisturbed.

Let's imagine that the saw's top is not even there.

Now we raise and lower the blade.

If the axis of the blade arm pivot and the arbor axis are paralell, the blade will move in a singe plane......not sideways.

This would hold true if the saw were on it's side, hanging from the ceiling, or in China.

When the blade is tilted one degree it still must move in a single plane.

When the blade is tilted 45 degrees, it still must move in a singe plane.

Again the saw's top (an unrelated plane somewhere in space) has nothing to do with whether or not the blade moves in a single plane.

Bad blade arm.

JMHO

Rob

[Mike Marcade]

If the axis of the blade arm pivot and the arbor axis are paralell, the blade will move in a singe plane......not sideways.

Keyword here: IF

[Bill Bryant]

OK the saw is back upside down. A possible new twist. (pardon the pun)

Part 251 is a eccentric bushing--the hole through it is not centered. Part 246 goes through 251 and it engages the threads on 207 either tightly or loosely by rotating 251 and locking it with 245.

On my saw 251 was rotated to make the worm gear on 246 very tight against 207.

The curved, "threaded" part of 207 is not a perfect arc in relation to the worm gear on the end of 246, so toward the end that would be "blade down in table" the worm gear pushes hard against 207. This pushing against 207 increases as the saw blade is lowered.

There is enough flex (not play in bearings) in 207 that I can bend it a few thou with two hands gripping hard.

I think it's possible that 251 can be adjusted to free up the worm gear at the end of 246 so as to stop pushing against the threads in the arc on 207--there are shiny worn spots at the bottom of the threads in 207, especially at "blade down," and the peaks of the threads on the worm gear are shiny, but not the slopes.

I'm going to free up this worm gear and see whether it was slightly bending 207 as it moved it to the "down" position.

[Rob Will]

IF flex is occuring for whatever reason then the two axis are no longer paralell.

IF some outside force is creating flex, then I retract the "bad blade arm" comment. (Assuming it will spring back to the correct shape when the outside force is removed.)

I think you're getting close.
Good luck!

Rob

[Art Walker]

Part 251 is a eccentric bushing--the hole through it is not centered. Part 246 goes through 251 and it engages the threads on 207 either tightly or loosely by rotating 251 and locking it with 245.

I think the eccentric is there to allow the long-time owner to compensate for wear on the gear and screw surfaces to keep backlash low. Waiting on bated breath for the impact on your problem of reducing the bending moment on the elevation shaft. Seems to me a little backlash would be a small penalty to keep the blade from translating as its elevation is changed.

Art

[Bill Bryant]

Well, rats! It didn't help. Not one bit. I eased the worm gear eccentric bushing and put enough slop in there to make totally sure nothing was binding, and it didn't help.

My conclusion tonight as I wash the grease off my hands and get ready for bed:

I think part 207 is made of cheap cast iron that wasn't seasoned properly before machining and is probably slightly warped. This makes more sense than it having been bored poorly. I don't know though. It's late, I've given nine hours to this investigation today, and I'm ready for some shut eye.

[David Epperson]

Well, rats! It didn't help. Not one bit. I eased the worm gear eccentric bushing and put enough slop in there to make totally sure nothing was binding, and it didn't help.

My conclusion tonight as I wash the grease off my hands and get ready for bed:

I think part 207 is made of cheap cast iron that wasn't seasoned properly befor machining and is probably slightly warped. This makes more sense that it having been bored poorly. I don't know though. It's late, I've given nine hours to this investigation today, and I'm ready for some shut eye.

Right now, as I look at the parts diagram, I tend to agree with you. Will Delta not send you a new Part 207 at least? I would think that they would do more (or should), but that's another matter. To really check you could take 207 out of the saw, install the arbor bearings and some dead straight witness shafts, and check parallel between the arbor axis and the pivot axis. Micrometers, center to center both sides and plate glass and gage blocks across the top. Again the "fix" will be either a new 207 or rebore and bush at least one set of the holes. Not a job for a dremel tool either.

[Chuck Wintle]

One thing that occurred to me was if the fit between part 207 and part 250 was loose because part 205(pin) was undersized. This could allow part 207 to slop from side to side causing the problem being observed.