50’s Dewalt MBC radial arm saw

[jwmay]

I don’t have the space for such a great saw as Mike is working on. But I hoped there may be some answers among you. I am registered over at the Delphi forums, but it’s not a great interface.
So today I’ve got a simple question, which isn’t necessarily tied to radial saws.

I read in the Delphi forums somewhere that the saw blade should stop spinning within 8 seconds of cutting the power. This was said to prove the motor bearings were good. This doesn’t seem quite right to me. But another thing about the Delphi forum is that most of this old wisdom is ten years old at least. So will anybody here familiar with RAS co-sign on that statement? If yes, can you tell me why?

My little saw doesn’t have a blade brake, and stops in 10 seconds. The shaft rotation feels smooth, and it makes no strange noises.

And here’s a picture. I tried to stylize my rust cover up job, and it doesn’t look as good as I hoped.

 

[markba633csi]

Compared with brand new bearings out of the package yeah, yours probably have a tiny bit of wear. 2 seconds worth
I wouldn't worry about it
Nice vintage saw- older logo
That's what the African/American employees used to say at Disneyland: "There goes de Walt"

 

[jwmay]

Sort of looks better from this angle. Ha!

 

[Liljoebrshooter]

I have virtually that exact saw that was my father's.
From what I remember reading about the saw taking a long time to slow down is the grease and the seals are dried out in the bearings. Not that they are bad just probably crusty and not a lot of lubrication.
For the amount of time it gets in a year, it will probably last the rest of my life.
It probably wouldn't be a huge job to split the motor and replace the bearings in it.
Joe

 

[jwmay]

I assume my bearings are fine. Most of the guys on the RAS forum recommend bearing replacement. It’s not a big job. Ten seconds seems pretty fast to me. But if that seems right here too, then I’ll carry on.
The thing cost pretty much nothing, and apparently has very low resale value. But I’m excited to get it in running condition, and start a wood working project.

 

[jwmay]

Ok, someone want to help me think through this?
I’m trying to set the saw to crosscut at 90 degrees. I’ve managed to adjust it according to internet wisdom. But I cannot get it at a straight 90. Over the the distance of an 8” blade I get .012-.015”.
I tried this at both extremes of travel, with nearly identical results.
I think this means that the issue isn’t in my cross cut travel setting, but in the saw “yaw”. As in the blade itself isn’t hanging parallel to cross cut travel. Does that seem right?

 

[Jake M]

I'm not sure how you're measuring that, but you've got three things you need to have lined up.

Obviously to get the saw to cut dead true on 90 degrees, it's got to be set dead true to 90 degrees.....

The yoke has to be set and locked solid to hold the motor and blade dead nutz parallel to the travel path.

And the bearings.... Those saws are pretty OK, but they've all had a good long live by now. The bearings (and the ways I suppose) can get something on them or in them, so they "bounce along" instead of rolling dead true. That will show up as a cut that may be at any partiuclar angle, but will show up as not being a truly straight line.

Step one in "my way" to set up a radial saw is to find a framing square that you trust and/or you verify to trust it. Put it on the fence, line up ONE tooth on the blade to the edge of that saw, and slide it out, visually watching for a gap.. This will get the arm at 90 degrees. At that time, watch the blade for left/right movement along that travel. Run it in and out a couple of times, still on that same, single tooth. You'll be able to sneak up on it and visually see if this is coming into play. Last, is to square up the yoke so that the blade matches the travel.

The next step is where it gets "messy". You'll want to make some actual cuts, and you're going to have to study any deficiencies, and react from there. There really are no "directions" at that point, you've just got to read the boards. I say it gets messy, because it will usually take a couple of iterations, since every adjustment kind of affects every other.

The last step (doesn't have to be last, but it doesn't affect the others), is to trim the miter to dead nutz 90 as well.

On the motor thing- I think you've got the right conclusion here. One that runs a little longer probably means that the bearings are drying out and the seals (if any of that type) are getting old. The bearings aren't "shot" until they make noise and/or the motor shaft/spindle "wiggles" in the motor housing. They might last for decades in that condition if it's not in production. I wouldn't touch 'em without any symptoms.

Those are very nice saws. A little fiddly to get one back in trim sometimes, maybe, but once you do... Well, my saw is a different brand, it's 50 years newer, and I wish it were 50 years older, when all of the manufacturers took those saws seriously By the time I bought mine, they were ALL DIY grade throw away crap. I'm a little jealous

 

[jwmay]

Just to show you what or how I was measuring. If you look at the photos, you’ll see there’s currently .020” discrepancy. After all the time I’d spent, that’s where it was when I gave up for the day. Lol
The blade has around .003” runout, but it’s dirty and rusty, so I chalked the .003 up to that.

 

[projectnut]

I don’t have the space for such a great saw as Mike is working on. But I hoped there may be some answers among you. I am registered over at the Delphi forums, but it’s not a great interface.
So today I’ve got a simple question, which isn’t necessarily tied to radial saws.

I read in the Delphi forums somewhere that the saw blade should stop spinning within 8 seconds of cutting the power. This was said to prove the motor bearings were good. This doesn’t seem quite right to me. But another thing about the Delphi forum is that most of this old wisdom is ten years old at least. So will anybody here familiar with RAS co-sign on that statement? If yes, can you tell me why?

My little saw doesn’t have a blade brake, and stops in 10 seconds. The shaft rotation feels smooth, and it makes no strange noises.

And here’s a picture. I tried to stylize my rust cover up job, and it doesn’t look as good as I hoped.

I'm not sure I subscribe to the theory that the blade should stop within 8 seconds. I have 2 radial arm saws in the shop(s). One is a 1970's era Dewalt 740, and the other is a 1990's Delta 33-400. The 10" Dewalt has a manual blade brake, and the Delta has an electronic auto brake. I installed new bearings in the Dewalt a couple years ago and the blade still spins longer than 8 seconds after the power is removed. I normally just let it coast to a stop rather than engaging the manual brake. There is nothing in the owner's manual stating the time it should take for the blade to stop spinning.

The Delta is a 14" machine and as mentioned earlier has an electrically activated brake on the fan end of the motor. According to the owner's manual it should take 1 second per inch of blade diameter to stop the blade when properly adjusted. In this case the blade should stop in 14 seconds if the brake is working properly. It's hard to believe a 10" saw with no brake should stop faster than a 14" machine with an automatic brake.

 

[jwmay]

I think this means that the issue isn’t in my cross cut travel setting, but in the saw “yaw”. As in the blade itself isn’t hanging parallel to cross cut travel. Does that seem right?

I’ve found the error. It’s operator error. I was on the right track though. Setting saw travel perpendicular to the table is a framing square and eyeball operation. I was using a test for what’s called “horizontal heel”.
So I’ll set the dial indicator aside for now. Haha