delta 10" direct drive table saw bogs down - Woodworking Talk - Woodworkers Forum
 
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post #1 of 8 Old 06-16-2019, 10:08 AM Thread Starter
dbnewton
 
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delta 10" direct drive table saw bogs down

This did not happen when the saw was new (but that was quite a few years ago).

The saw seems to take an inordinately long time to come up to speed unloaded.

The blade is new and sharp. It is a thin kerf blade. 32 teeth.

The fence is straight and adjusted very very slightly wider at the back than the front to avoid binding on the fence at the back of the blade.

The wood is ply and not pinching the blade or twisting (outfeed roller).

Because of the slow start up and the fact that this is reasonably new behaviour I am suspicious of the motor. Perhaps brushes????

Anyone experience this and if so what remedy?

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post #2 of 8 Old 06-16-2019, 10:22 AM
where's my table saw?
 
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Possible issues ......

I would check the brushes first. Remove them carefully and note the orientation of the curvature on the end. They should be long enough to apply a reasonable amount of pressure on the armature. If not, there are many common sizes available to replace them.


https://www.ebay.com/sch/i.html?_fro...ushes&_sacat=0



Next check the power supply circuit. Eliminate any extension cords IF possible and use only 16 GA or 12 GA if needed. The supply outlet should not have other motors plugged in and running simultaneously, like a shop vac or dust collector. Avoid a circuit that has the lighting and the power tools on the same line. Power tools like "dedicated" supply circuits.



I don't think a AC/DC direct drive motor has a starting capacitor, BUT and induction type will have one..... mine do, but they run on 220 volts only. A direct drive table saw is much like a circular saw inverted under a table top. It's a cheap way to manufacture a tablesaw, but is not the best approach.

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 8 Old 06-16-2019, 07:16 PM
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first, the saw is not "bogging down" - that describes a motor slowing down under load.
I presume you're not cutting anything when you hit the on switch.... so the adjustment of fence, etc. plays no role.



electromagnetic forces are instantaneous and hugely powerful.
slow starting/rev up is much more likely to be gummed up bearings than a problem with the motor brushes/etc

depending on model, may not have brushes... a weak capacitor is a possibility tho.



unplug

crank the blade all the way up
spin the blade by hand


it should spin/turn with near zero resistance.


if it's not 'stiff' then check the capacitor.

Last edited by Leo G; 06-17-2019 at 03:31 PM.
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post #4 of 8 Old 06-17-2019, 11:01 AM
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This is the problem with direct drive motors in the jobsite and cheaper table saws. They do not handle loads and are little more than a circular saw.


Probably time to start looking for a more substantial machine with an induction motor.
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post #5 of 8 Old 06-17-2019, 11:44 AM
where's my table saw?
 
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Cheap is cheap, no matter .....

Circular saws with brush type motors, can run for ever with proper use, and maintenance. In fact, most corded hand held power tools have brush type motors.



Of course, an induction motor is made for continuous duty and is much more robust. If the brush type motor is made on the cheap, it will certainly fail sooner..... bushings rather than bearings, lack of proper ventilation for cooling, or operator abuse by overloading will all affect the life of the tool.

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 #6 of 8 Old 06-17-2019, 03:25 PM
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Quote:
Originally Posted by DrRobert View Post
They do not handle loads and are little more than a circular saw.

not a lot of load when switched from off to on.
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post #7 of 8 Old 06-19-2019, 03:14 PM Thread Starter
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Thanks everyone for all the suggestions.

I checked the brushes (was easier than I feared). But there was still nearly an inch on both, so I doubt it is brushes.

I also didn't think bushings because the blade spins freely (I should have mentioned that in the OP).

I also didn't mention that the saw is on its own 29A/12GA circuit with a very short run.

For TomCT2: the point of the OP was the saw is bogging down, yes under load... I only mentions the slow start because it might be related, but I wouldn't give a damn about slow start if it didn't also big down.

So maybe the bottom line is it's just time to upgrade as DrRobert suggested. Heck I've had a lot of good years out of that saw and it was never a great saw to start with (small table, difficult to adjust, low quality fence, ...)

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post #8 of 8 Old 06-20-2019, 08:38 PM
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After years of use the brushes wear a channel into the commutator bars and down to the mica separators between the bars. After a while the brushes are riding more on the mica than they are on the copper. This condition can rob power to the motor.

Not an easy task and chances are that the magnitude of the task will make replacing the saw the path of least resistance.
Screwy picture sequence. Its backwards. Sorry about that.

https://www.woodworkingtalk.com/atta...376525&thumb=1
Needing attention
https://www.woodworkingtalk.com/atta...376523&thumb=1
cutting down the mica slots by hand
https://www.woodworkingtalk.com/atta...376521&thumb=1
deepened mica slots
https://www.woodworkingtalk.com/atta...376519&thumb=1
partial lathe turning
https://www.woodworkingtalk.com/atta...376517&thumb=1
turned armature ready to go.
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