Could someone answer this

[Mike Ballard]

Hi -

I had PC look at an 89x router motor that generates so much heat it's hard to handle the bit afterward. He didn't know what the problem was (and hadn't seen the problem before). He called today and said he had another in with a different problem but being curious ran it on the bench like he did with mine and saw the same excessive heat generated in the mainshaft. He suspects an armature clearance problem. My motor and this one are about 30,000 units apart so it seems this heating problem isn't new. I've had a 690 for years that never even warmed the bit in the least.

So I have two questions for the group, assuming there must be others here with this motor and that I'm not the only with this 'problem':

1. Does ANYONE with this motor NOT see excessive heat?

1. How do those with the heat change bits when they're really too hot to handle?

I'm a design engineer and I find it incomprehensible that PC would knowingly design a motor generating so much heat the collet/bit can't be handled without gloves but more importantly the metal fatigue of parts rotating at 23k RPM with this kind of sustained heat seems just plain dangerous (not to mention the danger of wood dust/high heat).

I'm just trying to understand how come the couple times I've posted no one has said they do or do not see this kind of heat in this particular motor? Although I think this motor is only a year old, PC routers are too popular for me to be the only one in the group with one.

Mike

[Jim]

I have a PC 7518. I too have noticed that it gets quite hot. Not so hot that I can't remove the bit, but hot enough that it has made me wonder.

Jim web site:

[Swingman]

What's the difference in HP rating, size of motor over the 690? IME, higher heat buildup during use seems to be consistent with the larger size/rating, but even this sounds like it may be only part of the problem with yours..

Don't think I have that particular motor, but a related PC motor/model ... a

7518 that has always exhibited much more heat during use than previous routers I've owned (I own three 690's of various vintages), which I chalked it up to the correspondingly larger rating/size.

Besides the high heat problem you are experiencing, you might also want to watch out for the following:

There have been reports of bits slipping on the 7518. I have always been of the opinion that the heat buildup on the larger 7518 was at least a contributing factor to the bits slipping, mainly due to the difference in heat expansion of the different metals in the collet, bit and shaft.

Carefull use, clean parts, and hardy tightening seem to mitigate the problem ... but it is certainly something to be aware of with these hotter running routers.

Just a FWIW ...

[DonkeyHody]

Mike, I don't have the same model router as yours, but my new PC 7918 is in the shop right now with the same problem. The collet would be too hot to handle after a few minutes of running, whether loaded or not. I suspect the bearing next to the collet is too tight. The 7518 has been around for a long time and has a great reputation as a workhorse, so I don't think it's a design problem with that model. I wonder if they got a bad batch of bearings? Please let us know what you find out, and I'll do the same.

DonkeyHody "Even an old blind hog finds an acorn every now and then."

[Mike Ballard]

The 690 is 1.5 HP but I guess they advertise peak now so I'm guessing this one's > So I have two questions for the group, assuming there must be others here

Besides that being a pretty studly router, does it heat the bits to the point where they're hard to handle?

I could see (for mine) where a little heat might be understandable except for two things: its predecessor never did anything like this and the other thing is that I can run this one without the collet for a minute or so and it starts getting hot (and I mean hot).

I didn't think of that but you're right. I have a little portable router table I put on my workbench meaning when I lean in to use it it's at face level. Makes me damn nervous using this thing - loosening bit, failure from metal fatigue....

Mike

[Mike Ballard]

I talked to the PC factory today (TN) and evidently the hotter-running 89x motor was intentional (which is the info I've been after). PC said the higher heat of this motor is due to tighter tolerance bearings, specifically used to cut down on contamination failures. I haven't seen this myself but he said the far coolor running 690 was prone to warranty failure because the bearings had clearance to allow the tool to run cool but the trade-off was greater contamination. I've had no such trouble with my 690 and have used it for five years with many, many hours on it.

And I'm no one to argue with him but it seems to me that if it really was that kind of a problem, the 690 having been in production for so many years I would have expected later models to run hotter than earlier ones because being such a big problem that the new router required a fix, so too the 690 must've required a fix. But I've never heard of that. So I'm not sure (and didn't think to ask at the time) why this contamination problem he talked about wasn't 'fixed' until the new motor.

None of this is to say I don't have some other problem with my particular motor but am starting to think that I don't. He said they've investigated this issue and that a temp in the range of 140 degrees from using the higher-tolerance bearings in this motor is acceptable. He also said it should begin to run cooler at some point as the motor gets used more and more (but didn't say how much cooler).

I also asked him about bit slippage problems and he said as far as he knows that would not be an issue because of heat from these bearings. The only time he said it was was in actual dimensional problems but certainly (his words) not from a heat differential between the mainshaft/collet/bit shank.

Bottom line is I can only hope they're not explaining away a problem that would be too expensive to fix, needing to recall all 40,000 motors sold so far since the factory guy I took mine too said he saw the same heat on a much older 89x motor.

Mike

PS Man, people in TN talk slow. Half the time I started with another question he was still working on the last one so he probably thought I was some rude guy for continuously interrupting him :-) But it was just hard to know when he was finished talking or just pausing (and he paused a lot!)

[TeamCasa]

I don't and woulod not accept that as an answer. I would insist they send that to me in writting.

Dave

[Rudy Lang]

This I think makes very little sense. Tighter tolerances do not necessarily equate to a tighter fit thereby increasing friction and therefore heat. Tighter tolerances simply mean that the range of acceptable components falls within a tighter margin. Which is wider A) a 6" wide board +/- 1/2" or B) a 6" wide board +/- 1/4"? Now, clamp up a panel using 6 boards from each lot (A & B). Which will be wider? Which lot will more consistently produce panels that are closer to 36" wide? Which lot can not produce a panel greater than 37 1/2" wide?

There may be some accuracy in saying the higher heat of this motor was intentional and a design decision to minimize contamination but to place blame on tighter tolerances is less than accurate +/- a line of BS.

Am I missing something fundamental here?

Rudy

[Morris Dovey]

I don't think so - and your BS detector seems to be well-tuned. The story sounds like a way of avoiding the necessity to admit that they didn't want to live with the cost of a higher quality (and sealed) bearing.

2¢

[bridger]

no what does kind of make sense is that they increased the amperage of the motor without increasing the motor housing size. that makes some sense when related to cooling problems....

[patrick conroy]

Well, not sure if you talked to a CSR or the actual engineer that's on the build team - but, hey - at least you got through to someone who's in a position to know.

Yepper's - took me a loooooooong time to get used to the pace. Had some real fun when I was on a project with a fast-talking-girl-from-Philly and a West-Texas-Odessa-Good-Ol-Boy mechanical engineer. Watching those two trying to communicate was priceless.