My new to me Dewalt MBF RAS

[jteneyck]

Yesterday, I bought this beautiful little MBF for $75.  



Every point of movement was very hard to move, but some WD-40 freed all of them and everything moves beautifully smoothly now.  I still have to pull the motor carriage out and clean the bearings, but I think they are fine, too, just dirty.  All the knobs are there.  The only things missing are the rip rod and blades wrenches.  It looks the original main table on it, too.  Built from 1955 - 1959, IIRC, that suggests to me it never saw much use in those approx. 65 years.  

Ok, now for the motor.  It runs fine but has a strange sound when stopping.  It doesn't sound like a bearing, and the shaft is firm with no play.  It sounds more like something rubbing.  The bearings have never been replaced, so it's clearly time, but changing them is not the easiest job what with having to carefully pull the fan off.  Regardless, I'd like your opinion on what might be making that sound.  Thanks.  

Link to:  Video

John

[fredhargis]

I have no idea what that might be, but those motors are so simple there's almost nothing inside that can rub...unless something broke off or got sucked into it. I'm wondering if it was correctly reassembled when the bearings were replaced.There is a snap ring on the inside of the bearing (arbor side), maybe it's somehow cauding the noise. Regardless, I'm thinking you'll have to open it up. It should be much like you GWI motor, but here's a good pictorial over at OWWM showing the innards. You may have already saw this, but this way you won't have to search for it.

[jteneyck]

I have no idea what that might be, but those motors are so simple there's almost nothing inside that can rub...unless something broke off or got sucked into it. I'm wondering if it was correctly reassembled when the bearings were replaced.There is a snap ring on the inside of the bearing (arbor side), maybe it's somehow cauding the noise. Regardless, I'm thinking you'll have to open it up. It should be much like you GWI motor, but here's a good pictorial over at OWWM showing the innards. You may have already saw this, but this way you won't have to search for it.

Thanks Fred.  I'll check that out.  The bearings have NOT been replaced.  The paint is still on the rod ends and nuts.  

I blew out the fan with compressed air.  Lots of dust, as might be expected.  It ran beautifully the first cycle or two, then the noise came back, but not quite as loud.  I think I'll just let it run for 5 or 10 minutes and then see how it spins down.  I wouldn't be surprised if the saw hasn't been run in years.  I bought it from a guy who clearly knew very little about it; didn't even have the wrenches for it, so ... 

John

[jteneyck]

I have no idea what that might be, but those motors are so simple there's almost nothing inside that can rub...unless something broke off or got sucked into it. I'm wondering if it was correctly reassembled when the bearings were replaced.There is a snap ring on the inside of the bearing (arbor side), maybe it's somehow cauding the noise. Regardless, I'm thinking you'll have to open it up. It should be much like you GWI motor, but here's a good pictorial over at OWWM showing the innards. You may have already saw this, but this way you won't have to search for it.

That's a great pictorial and description, Fred.  Thanks again.  \

John

[Roly]

That's a great pictorial and description, Fred.  Thanks again.  \

John

It should have some sort of blade brake on it,  either manual mechanical or electrical.  I have a feeling that is what you hear.   Roly

[jteneyck]

It should have some sort of blade brake on it,  either manual mechanical or electrical.  I have a feeling that is what you hear.   Roly

Thanks Roly.  My friend has an MBF with that feature.  There's an electrical box up with the switch with whatever system is used to make that happen.  This one doesn't have that, just a simple switch.  But your comment has crossed my mind.  I might open the motor wiring box and have a look to see if there is something beyond the typical point contacts in there.  

John

[jteneyck]

Thanks Roly.  My friend has an MBF with that feature.  There's an electrical box up with the switch with whatever system is used to make that happen.  This one doesn't have that, just a simple switch.  But your comment has crossed my mind.  I might open the motor wiring box and have a look to see if there is something beyond the typical point contacts in there.  

John

Nope, no brake.  

I let it run for at least 5 minutes.  Still making the sound when I turned it off.  It does it once in a while on start up, too, so it must be in the bearings.  But it runs so smoothly that I might just leave it be for now.  

John

[MstrCarpenter]

Is that the one the advertised as a "portable workshop"? I have an 8" that's only "portable" because it has a pair of D handles on each end. Still takes two strong (and/or younger) men to move it.

[Roly]

Nope, no brake.  

I let it run for at least 5 minutes.  Still making the sound when I turned it off.  It does it once in a while on start up, too, so it must be in the bearings.  But it runs so smoothly that I might just leave it be for now.  

John

While it would not be related to the noise, take off the nameplate on top of the motor and see if there is a small  transformer, small capacitor and rectifier.   If so it had dynamic braking which is no longer working.    Roly

[jteneyck]

While it would not be related to the noise, take off the nameplate on top of the motor and see if there is a small  transformer, small capacitor and rectifier.   If so it had dynamic braking which is no longer working.    Roly

Nope, just a coil and the contactor.  

John