burned table saw switch

[SteveHall]

Has anyone upgraded their table saw switch to a "safer" style with the big red stop paddle?

My Delta contractor table saw (36-382) power switch (part # 438010170206S) finally died today. Here's what the contacts look like now:

(Of course, I completely removed the motor first to diagnose it before realizing it was just the switch--surprisingly more difficult to take off than the motor!) I'm relieved it is just a $20 part. But...

My saw is the relatively new style of power switch with a cheap black plastic lock-out hood to make it easier to press. But the switch is still located below the fence rail and impossible to see from standard operating position overhead. I've marked the fence to easily find the switch and have used it comfortably for years with no problem.

Has anyone re-worked a dual-voltage saw switch with one a little more user friendly that might work better for teenagers learning to woodwork? I can't decide how much trouble it might be to rework all the wire connections and mounting points for a new switch.

 

[junquecol]

Years ago, I converted my Delta CS to a magnetic switch. Power goes out, saw won't restart until start switch is pressed. Assembled it from "off the shelf components." Handy box with no & nc switches along with relay, and transformer to operate relay. Relay is dual voltage thermostat transformer from Grainger as were most of the parts. I mounted it on the rail of fence, so no stooping over to find it. Actually I moved it from my old Sears saw. New location was about an inch different from old. Took me months to train my muscle memory as to where it now resides.

 

[chris_goris]

Years ago, I converted my Delta CS to a magnetic switch. Power goes out, saw won't restart until start switch is pressed. Assembled it from "off the shelf components." Handy box with no & nc switches along with relay, and transformer to operate relay. Relay is dual voltage thermostat transformer from Grainger as were most of the parts. I mounted it on the rail of fence, so no stooping over to find it. Actually I moved it from my old Sears saw. New location was about an inch different from old. Took me months to train my muscle memory as to where it now resides.

Grizzly sells these for replacements and has great wiring diagrams. If you are thinking of going to a mag switch, which I would, look at their website, you can find one there that will work.

 

[Dee2]

I replaced one with a Grizzly switc on an older model Unisaw and then found the original style switch on ebay. Used the Grizz switch when I put the DC motor on the old lathe. I have spares of both (if I can find them after redecorating the shop). Let me know. All are new, unused but not in original package.

You'll need some wiring awareness. The terminal orientations are not always the same with replacement switches. Replaced a switch on a porter cable belt sander that was stuck "on" recently. The replacement rotated the terminal orientation and I didn't pay enough attention. Popped the circuit breaker during the smoke test before I looked carefully and the switches terminal labeling.

 

[SteveHall]

I replaced one with a Grizzly switch...

Never thought to check Grizzly, I could probably make do adding an electrical box and one of theirs. Thanks for the idea. (And offer on yours, but I probably won't be in Winterville for a few weeks, although I do projects at ECU.)

You'll need some wiring awareness.... Popped the circuit breaker during the smoke test before I looked carefully and the switches terminal labeling.

Hilarious way to write this. I didn't want to have to re-do electrical connectors for this reason. Not hard, but one more step...

 

[Dee2]

Learned smoke testing at the Savannah River Site in SC - LOL.

 

[SteveHall]

To wrap up the outcome, I ended up putting on a magnetic paddle switch for $10:



For anyone else attempting this...

My switch was sold as a POWERTEC 71054 currently available at Amazon for $10. It is manufactured by and stamped KEDU KJD17B, although it appears more similar to their HY56 with many "OFF" and "STOP" variants found around the web. (Like the Woodstock D4160 also sold by Grizzly.) I actually like "OFF" over "STOP" because it is more accurate for what it does. You can tell it isn't an expensive component, but the quality feels adequate for my purposes and contractor saw grade.

The switch is rated for 16A at 120V and it appears other variants have slightly higher ratings and state specifically they are suitable for 30A and/or 240V. Although this wouldn't be suitable for a larger saw and circuit, it will be just fine for any 120V saw running on a residential power circuit. It has 1/4" spade connectors which fit my existing Delta contractor saw's connectors. I wasn't expecting that to be so simple, and perhaps older Deltas or many other manufacturer's models would require new connectors, but I didn't have to re-do any. (My Delta is the last of the right tilt saws, purchased approximately 2004 or so.)

It definitely has a magnetic safety stop. I tested by turning on the saw, uncoupling the power cord without touching the switch and re-connecting the cord after the motor spun to a stop. The switch had turned off, and I had to re-press the ON button to re-start it.

It comes with lockout holes through the ON button suitable for a long, thin padlock sold for the purpose.

Replacement was relatively easy. I had to buy and add a deep electrical box for mounting the switch. It meant drilling a hole to mount it to the original heavy steel switch mounting plate which extended down behind the fence. I am pleased that this new switch and electrical box now sticks out a bit more than the old one so that the OFF paddle is nearly flush with the fence and easily visible from above, unlike the original switch which was uncomfortably hidden behind the fence. It is also suitable for turning off with a knee, something the old switch wasn't.

 

[scsmith42]

Learned smoke testing at the Savannah River Site in SC - LOL.

Whoa! There are definately some things there that you don't want to see smoking!

 

[SubGuy]

Definitely....

Whoa! There are definately some things there that you don't want to see smoking!

 

[mkepke]

The switch is rated for 16A at 120V and it appears other variants have slightly higher ratings and state specifically they are suitable for 30A and/or 240V. Although this wouldn't be suitable for a larger saw and circuit, it will be just fine for any 120V saw running on a residential power circuit. It has 1/4" spade connectors which fit my existing Delta contractor saw's connectors.

Steve - I looked at the switch specs and that particular switch is only rated for a 0.5HP motor load. The 16A rating is for a resistive load, like lighting.

Since you are using it to switch a 1.5HP motor,expected service life will be much shorter. No idea if it presents an actual safety hazard tho.

http://powertecproducts.com/71054-120v-magnetic-paddle-switch/

-Mark

 

[CrealBilly]

Not to be Capitan Obvious here but there were to many amps flowing through that switch. Don't know if it was the result of a severe drag on the blade (dull or sawing through thick wood) or the result of a voltage drop, which would cause amps to spike also.

When i lived in NC we were constantly fighting voltage drops in the summer. I figured out the house across the street was causing the voltage drop everytime the AC unit kicked on. We shared a transformer with 4 houses and was subject to whatever they did. Once i caugt on it was easy to figure out. AC across the street kicked on, our lights would dim. Called progress energy and got no where. Talked to my neighbor across the street and got nowhere also.

Eventually the AC unit across the street burned up and she had a new one installed and we didnt see the voltage drop after that.

Here in southern IL we have our very own private transformer and our juice has been rock soild since day one.

 

[SteveHall]

Since you are using it to switch a 1.5HP motor,expected service life will be much shorter.

Is it really a 1-1/2 HP motor? I've always heard they can't actually be that high on a 15A circuit and that the manufacturers tend to inflate the numbers.

Thanks for the info, I'll keep an eye on this and report back if it is an issue. Plenty of work coming up to test shortly...

 

[SteveHall]

Not to be Capitan Obvious here but there were to many amps flowing through that switch. Don't know if it was the result of a severe drag on the blade (dull or sawing through thick wood) or the result of a voltage drop, which would cause amps to spike also.

It actually died after about five quick on-off cycles cutting through several small pieces. I'm suspicious of dust. (Our power in this part of Apex is rock solid.) The inside of the case was full of powder and the original switch wasn't dust tight. I didn't notice any inside, but it may have all just burned off very rapidly! I'm going to seal off this box with silicone to avoid this potential problem in the future.

 

[bob vaughan]

On "switch ratings", most hobbiest type equipment, the ratings are totally bogus for their intended purpose (induction load [motor], rather than resistive load [light bulb])


Set of contacts from an IEC type starter that burned up after a couple years use in a 3 HP table saw. The starter has a sticker on it saying it was "rated" for the intended load. At the bottom is a NEMA size 1 contact with a 27 amp rating. The starter label says maximum 3 HP on single phase.



On the left is the same set of small contacts from the above example, except in this photo in the middle is a NEMA size 0 contact set that's rated for 1 HP single phase. The one on the right is the NEMA size1 as mentioned above.




Another great example of mega BS in the ratings department. The contacts on the bottom are from the Asian-made switch that goes with the label. 30 amps? Really? Above that is the 30 amp NEMA rated contact.




Still another example. NEMA size 0 on the left, NEMA size 00 in the middle (including starter rating label) and on the right are contacts from a Furnas 12BA21T manual push button switch that's also over-rated.



Label on a Furnas 12BA21T manual switch often found on both Delta and Powermatic equipment.

 

[ehpoole]

Bob,

Thank you for taking the time to lay out the above photos to emphasize the degree to which most consumer switches are grossly overrated based upon resistive versus reactive loads as such is always quite frustrating to those who are in the know about the difference between a 20A resistive load that pretty reliably draws little more than 20A peak and an inductive or capacitive load that may draw upwards of 100A+ peak on initial contact closure prior to establishing the magnetic field or topping off a large capacitor bank and returning to a 20A load within several seconds after contact closure. Obviously if the contact closure load may be up to 100A then the contacts should be rated for that initial load to keep contact resistance low and adequately clean the contacts and not a mere 20A load, but in the never ending quest to make a quick buck and reduce materials to add to profits that is precisely what happens everyday in our consumer gear -- made good enough to generally last past the warranty period before the design deficiencies require repairs. Just as bad, inductive loads can also arc very badly upon contact break due to the back EMF created by the collapsing magnetic field within the windings and can further wear contacts not designed to handle that disconnect arcing.

I always enjoy your posts when you choose to chime in as you are very good at educating our members on such important issues that most are not even aware of or would never give a moments thought to under normal circumstances.

 

[SteveHall]

....the contacts should be rated for that initial load to keep contact resistance low and adequately clean the contacts....

I'm curious how the consumer would know what to buy without taking the manufacturer's ratings. I see references to NEMA, is that a reliable measure?

The insides of my original switch were surprisingly poor quality and small contact area. And when I look over the Grizzly catalog page for switches, all three paddle types are about the same price. Is the 220/440V 16A switch really that much better than the 110V/16A one? I see no mention of NEMA.

 

[bob vaughan]

The Allen Bradley 509 series are good NEMA starters. They're rated for millions of start-stop cycles.
The problem these days is that the internals of "consumer grade" switches all have dinky little contacts.
Another point about cheap switch contacts is that they starve the capacitor by constricting amp flow. This usually means premature capacitor failure and potentially motor failure. In most motor capacitor failures I've seen in the last 10 years, the machine had an Asian-made IEC type starter.
With motor starters, you get what you pay for. A good Allen Bradley or Square D will run about $400.00 or more. Are the $40.00 switches only one tenth as good? Not even that in my experience but $400.00 will buy lots of cheap switches and capacitors.



This is a shot of a old ad showing the differences. IEC is the European style magnetic starters so commonly seen for about fifty bucks. They come in those little plastic boxes about 4" x 6".

I suspect that in the long run, the NEMA starters will become more and more rare because the buyers will vote for the cheapies time after time.

I forgot to add, that the definite purpose starters are what are found in things like whole house air conditioners. They aren't much either.

 

[ehpoole]

I'm curious how the consumer would know what to buy without taking the manufacturer's ratings. I see references to NEMA, is that a reliable measure?

The insides of my original switch were surprisingly poor quality and small contact area. And when I look over the Grizzly catalog page for switches, all three paddle types are about the same price. Is the 220/440V 16A switch really that much better than the 110V/16A one? I see no mention of NEMA.

As a general rule, if you want proper commercial rated switches, where you generally have more trustworthy specs, you would go to an electrical contractor supply house to request such or research such online very carefully -- many will sell to the general public. But the first big tip off is the price, as you have noted already none of the switches on that page, especially the magnetic switches, are at all likely to be properly rated for a 2-3HP motor just based upon price and enclosure sizes alone.

NEMA is the National Electrical Manufacturer's Association, and they serve as a standards organization for many types of electrical equipment and enclosures, amongst many other things electrical in nature. But be careful of ratings on equipment imported from, particularly, China as they often overstate the ratings and claims on such items for market share (again, this is where especially low pricing can be a tip off) by offering underrated gear at rock bottom prices compared to what the real deal sells for. China is perfectly capable of manufacturing quality equipment, but such does come at a more appropriate price, so being manufactured in China is not a universal tip off (if only life were so easy). When it comes to untrusted sources sometimes the only way one can tell if a product is likely to meet its claimed specs is to dismantle and inspect such as the better knockoffs can use oversized enclosures and even include added deadweight to make it appear as if they have heavier components inside, particularly for online photo purposes. So it is easiest to just buy trusted name brands from trusted vendors whom have a real and established reputation to uphold.

That said, even an underrated switch can potentially deliver years of service in a consumer application where the device is not switched on and off hundreds of times each day. The big advantage to installing quality and properly rated switches is that they will deliver many decades of very hard use before they finally wear out and are less prone to welding closed on you (where the device remains permanently powered), or the opposite (where contacts are so chewed up it does not power on). Also, there are simple magnetic switches that cut out when power is interrupted (an often desirable trait) and then there are much better magnetic switches that also protect the motor from overload by also cutting out if the motor is pushed too hard or the rotor locks and draws too many amps (such as failure of the starting capacitor or centrifugal switch). You really have to choose for yourself what level of quality you wish to invest in for a home shop as we can accept downtime that would be unacceptable in a business environment. But it is good to know beforehand what you are getting so that one can make that choice. I wish that I could claim that all of my equipment had properly rated switched, but that is not true by a good margin.

Hopefully Bob can expand on the subject as he spends much more time immersed in the field than I ever did, which is why it is so great that he arranged the comparison photos above to really demonstrate the differences.

 

[Michael Mathews]

you might want to check the Grizzly site. I believe they have a 220v paddle switch in their clearance section. I looked for it but couldn't remember where I saw it.

 

[bob vaughan]

Showing these contact size differences is sort of a form of bashing since I’ve had to help my woodworker friends through this type of frustration so many times.

There are clear options to switch upgrades, but those options come at a cost that might not be worth it for the hobbiest woodworker.

Here’s a quick retail ballpark of what industry pays for high quality switches.

$300.00 starter and overload block
$50.00 enclosure
$50.00 overload heaters
$60.00 control buttons

Add wire, plug, connectors, and other things, one can see where the cost quickly approaches the price of a home workshop machine.

A bypass of these starter costs would be to educate yourself on starters and all the subtleties and then buy used components. That’s what I’ve done over the years. Putting a complete starter together for a c-note or less is what I usually strive for.

…and then there’s the issue of where you hang those great big starter boxes.
(yeah, yeah, I’m enjoying how easy it is to post photos with this new forum format)




Delta did this in the 1960s for a while. The box tended to get filled with dust. They later went to putting the box on the outside again.