BT-3100 Motor Help/Question

[Jack Watts]

Greetings all,

I'm the owner of a BT-3100 table saw which I purchased off of Craigslist about 5 years ago. The saw appeared to be almost unused when I bought it. About 2 months after I bought it, a pex water connection in my ceiling let loose (long story...), pretty much directly above the saw. I wiped down the saw as best I could, then let it sit for about a month. I mention this as it may (or may not) be related...

Here's the issue: the saw will barely cut. I never cut anything with it before the impromptu indoor rain storm, so I don't know if it's related or not? It turns on, it's loud, and it sure seems to be spinning at high RPM's like any table saw. Compounding the issue is that I have a Makita contractor saw as well, so I just haven't invested much time or energy in getting this thing working.

I've used the saw periodically, and it always behaves the same. It's burning 1/2" MDF, to give you an idea of how little power it has. I've run it to a dedicated outlet, and it helped a fraction, but not much. As-is, it's barely useable, but I'd like to get it running, as I really like a lot of the features of this saw! So, my questions:

-this seems like something is wrong with the motor...right??

-is there a test procedure for the motor, and any rebuild parts available? I'm willing to tear into the motor.

-lastly, is there a source for motors besides the $230.00 on I've seen from Sears?

Thanks for reading, and I apologize in advance for the silly questions. I've searched a good bit on the forum but haven't really found the answers--but if they're on here somewhere, don't hesitate to direct me that way.

JW

[cork58]

Does it bog down on crosscuts or ripping with a fence? Have you tried a different blade? Have you cleaned the motors sawdust? In what condition are the belts?

[Jack Watts]

Does it bog down on crosscuts or ripping with a fence? Have you tried a different blade? Have you cleaned the motors sawdust? In what condition are the belts?

Thanks for the quick response! In order:

-it bogs down no matter what, regardless of grain orientation (even on MDF?), with or without the fence

-I flipped it upside down and vacuumed it out. Is there a more involved procedure for cleaning out the motor? FWIW, there's not much visible dust under there, and looking at the underside of things, it looks like there are very few total hours on the saw, but I'll certainly try

-yep on the blade--I tosses a new one on there, no real difference

-hmm....I don't know. I was guessing fine given the total hours on the saw (while old, it's been stored @ room temperature for most of its life. Is there a link to checking the belts though, and what specifically I'd be looking for when I check them?

Some other info that may or may not be helpful; while it seems like the saw is "smoking", it's really just the wood burning (I think). When I just turn the motor on it runs fine w/o any funny smells. Also, it seems totally smooth-running when I flick it on, not at all like my DD Makita, which sounds awful every time I turn it on. It just bogs down as soon as the easiest piece of wood touches the blade.

[Bill in Buena Park]

Jack, you're going to get a lot of good help here, but I don't believe burning the wood during a cut is caused by the motor. Sounds more like a dull blade, or if this is during ripping, maybe your fence is out of alignment. Also assume your Makita experience means you have the blade mounted with the teeth facing the right direction.

How does the saw crosscut, using the SMT?

[Black wallnut]

Do you have the blade mounted in the correct direction? The teeth should be facing you.

[JimD]

The check for the belts is basically to look at them and be sure they look OK. When they go bad, pieces come off and they burn up into globs. You can see them if you pull the throat plate and look on the right of the blade. You might need to pull the blade and/or use a flashlight.

Another thing to check is the brushes. They can be removed just like on a hand held circular saw.

I agree with the backwards blade comments. I've done it on my radial arm, don't remember doing it on the table saw but I might have. No big deal if you did.

Jim

[Ed62]

The backwards blade seems like the most likely to me, especially if it acts the same when ripping and crosscutting.

You might want to get the BT3K FAQ from LCHIEN, by either sending him a PM or following the link on his signature. It has a lot of information for you. There is also a lot of information to be found at the following link http://www.bt3central.com/index.php?...ticles#General BT3 Information .

Welcome to the site. Enjoy yourself.

Ed

[Jack Watts]

Jack, you're going to get a lot of good help here, but I don't believe burning the wood during a cut is caused by the motor. Sounds more like a dull blade, or if this is during ripping, maybe your fence is out of alignment. Also assume your Makita experience means you have the blade mounted with the teeth facing the right direction.

How does the saw crosscut, using the SMT?

I wondered about the blade, which is a Forrest WWII with a million hours on it, but I have pulled it off my contractor saw and it was cutting great. I tossed on a brand new Dewalt all-purpose blade and it was worse....

It's funny you mentioned the blade being backwards. In the odd chance that this saw operated on some physics-defying principle, I tossed the blade in backwards on purpose, just to see what would happen; I pretty much shut down the motor--I immediately turned it off before I damaged it any more. The fence would be another thing, except cutting without the fence freehand it behaves the same.

Here's on other piece of info which may help. When the saw is hooked up to a dedicated outlet, it kinda works, a little. When I run it with a shopvac pulling on the same outlet, that's when it becomes unbearable. It's as if there's some sort of amp draw issue with the motor. Thing is, I'm just not all that well-versed on electric motors. I'd understand it more if it wouldn't turn on at all! It turns on, spins fine, but there's no torque.

I want to stress that I'm not trying to feed 2" maple through this thing and then complaining performance. Really, I'm not that guy! Right now I'm just trying to rip some 3/4" fir baseboard--nothing crazy. The top on my contractor saw has gotten so beaten up from being tossed around that it's just not suitable for finish work, which is why I decided to finally try and get this thing rolling.

[mpc]

Get a small incandescent lamp - 75 or 100 watt bulb. Plug that into the same outlet as your BT and make a test cut. If the lamp dims visibly, the outlet wiring is in dire need of attention. If you have one of those 3-into-1 outlet adapters, plug that into the outlet on the side of the BT, plug the BT's motor into the adapter, and the lamp into the adapter as well. Again, try a test cut. If the lamp dims now (or dims worse) then the BT's power cord, switch, or outlet are poor. Or your extension cord - if you are using one - is waaaayyy undersized.

Many modern outlets allow wire to be either wrapped around screws or just shoved into holes in the backside where it gets pinched. This pinch style connection often isn't as "solid" as the screw posts - at least according to some electricians I recently dealt with.

If the power is solid... then start looking at the BT's motor. With the saw unplugged, open up the back end of the motor and find the brushes. See if the carbon ends look worn at all; they should have pretty stiff springs pushing them into the motor armature. If the springs are soft, or the brushes are worn out so they're shorter than spec, there won't be solid electrical contact with the armature. If they look okay, and there is no obvious sign of binding (can you turn the blade by hand easily?) then the motor itself needs to be rebuilt/replaced. Used motors from somebody parting out their saw can be frequently found on this site.

All this assumes your saw slows down both with the regular fence or when you use the miter fence by itself. If the saw cuts okay with the miter fence only (main rip fence sitting on a shelf someplace) but binds with the rip fence, then odds are the rip fence is miss-aligned to the blade... the back end of the rip fence is closer to the blade than the front end. That squeezes the workpiece into the rear of the saw blade which is a VERY dangerous condition - it leads to the blade snagging the workpiece and kicking it back at you violently. And it also puts a lot of drag force on the blade slowing down the motor.

The BT is designed for a "thin kerf" style blade. It's literally thinner than a stock table saw blade so less wood is getting chopped by the teeth though using a regular blade isn't going to bring the BT to it's knees (after all it can handle fat dado stacks just fine). Using the wrong type of blade for each cut (too many teeth) especially on a rip cut also can slow the saw down. Same with shoving the workpiece too quickly past the blade. All of this is fairly intuitive though; the BT doesn't require "minutes" to make a typical cut. Certainly it should tolerate a similar feed rate as your Makita if the BT is working correctly.

mpc

[Jack Watts]

Thanks for all for the suggestions. I triple-check the power connections, and then decided to pull the motor apart (I found an exploded diagram to help me out). The armature looked good, bearing were fine. The two leads coming from the field coil were severely corroded. I don't see how this is even possible, since the motor seems to be fairly well-sealed (I don't think being dumped on with water for 20 minutes had anything to do with it, but who knows...).

I cleaned the leads, reassembled everything and plugged it back in. All systems go, and I'm ready to start destroying wood with this thing! I'm pretty happy, since the cost of a motor is > the cost of a new (used) saw on CL. As an aside, it's really a buyer's market for used table saws these days! I can only guess that the ground connection on the field coil was must making poor contact, but I'm not too knowledgeable r.e. electric motors.

Overall quick impressions: the sliding miter table is just weird to me, but I think I'll like it, especially for x-cutting big boards. This will probably stop me from pullout out my sliding compound miter saw, which is good because it's really freakin' heavy and inconvenient. It's really smooth, much smoother than my DD Makita. Power-wise, it seems more-than-adequate.

Thanks also for the links. There's some great stuff on here! I was bummed that the SMT got in the way of my outfeed table, but saw some great ideas for putting one together--and I happen to have a hollow core door laying around. I hope to destroy lots of wood in the future w/my new, now-functioning saw.

[leehljp]

Glad to see that it is working for you now. And welcome to the forum. Keep posting!

[toolguy1000]

glad to hear you were able to resolve your motor issues. good luck with the bt3xxx.