Changing Bearing In Dewalt Miter Saw

 
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Old 06-29-2011, 06:06 PM   #1
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Changing Bearing In Dewalt Miter Saw


I wrecked mine today when cutting some warped framing lumber.

The bearing only costs about $8, but to get it off, I need a puller, and to get it on, I may need an induction heater. These are shop tools I do not own. In short, I need a qualified repair shop, and one is nowhere near me.

What do you do?
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Old 06-29-2011, 06:09 PM   #2
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Re: Changing Bearing In Dewalt Miter Saw


Buy a new saw?

No mechanic around with a puller/press?

Come on North, think about.....

More than one way to skin a cat

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Old 06-29-2011, 06:17 PM   #3
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Re: Changing Bearing In Dewalt Miter Saw


puller is like 10 bucks for a cheapy.

I am sure you have an oven and a freezer, you should be set.
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Old 06-29-2011, 06:23 PM   #4
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Re: Changing Bearing In Dewalt Miter Saw


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puller is like 10 bucks for a cheapy.

I am sure you have an oven and a freezer, you should be set.
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Old 06-29-2011, 06:27 PM   #5
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Re: Changing Bearing In Dewalt Miter Saw


Pull the armature out & take it to the local machine shop & have them press the old one off & the new one on. Cost me $5 & them 5 minutes on my last one.
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Old 06-29-2011, 06:53 PM   #6
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Re: Changing Bearing In Dewalt Miter Saw


Ordered the bearing, watched the YouTube video showing how to score the old one and crack it off with a vise. Or at least the outer race. The balls and keeper come off readily then, but it takes a puller to get the inner race off. I'm sure the new one will need to be heated to go on.

Now for a puller and some heat. This ain't rocket science, but if one has not done it before, it can seem a bit of a challenge.

Gonna ask around to see if some of the auto shop guys know someone willing to do this pull off and replace thing.

Problem is, I live in a small remote village. It is an hour's drive to the nearest WalMart, and there is really nothing happening, machine-shop-wise, where I am. The nearest repair shop for tools like this is over in the next state, a long drive, including an expensive ferry round trip. By the time I go there in my truck and drop it, then do the same a week later to pick it up, I am well into the cost of a new saw.

Last edited by UpNorth; 06-29-2011 at 06:57 PM.
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Old 06-29-2011, 07:06 PM   #7
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Re: Changing Bearing In Dewalt Miter Saw


Yep! I gotta make it my bible!
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Old 06-29-2011, 07:59 PM   #8
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Re: Changing Bearing In Dewalt Miter Saw


Any decent auto shop should be able to do this for you, as long as they are not busy, & compensated. Even a small arbor press should do. That will be your best bet.

You could probably just use an 8" or so C clamp as a press. I've done it that way before, but it depends on the bearing tolerance. Find a deepwell socket, or tubing to press the center race squarely.
As mentioned by others, you can probably cut old bearing off with a dremel, die grinder, or plain old bench grinder. Just be carefull not to nick the armature wires, or comutator. Tape/mask, or cut a plastic bottle to cover & protect the armature. When you get down to the center race, cut on a diagonal ( or do bench grinder) & pop with a screw driver when the cut is close to the shaft. A small nick in the shaft won't hurt much if it does occur. just clean up marks before installing new.
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Last edited by Railman; 06-29-2011 at 08:02 PM.
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Old 06-29-2011, 08:22 PM   #9
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Re: Changing Bearing In Dewalt Miter Saw


You shouldn't need heat...I have never needed heat. They are press fit, but it ain't that tight of a press fit...I am also wondering how cutting bad lumber killed your armature bearing....I am more then willing to be they were already on the way out.
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Old 06-29-2011, 08:29 PM   #10
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Re: Changing Bearing In Dewalt Miter Saw


What ever you do DON'T heat the rotor shaft up......

Heat the bearing up with some MAP gas, or propane if you don't have any with a plumbers torch, Your going to have to come up with some type of sleeve bushing/plate to go behind the bearing to cover the span in-between the jaws of a bench vice. Once the bearing is warmed up and not severely hot (moving the flame point from the torch nozzle around the bearing- the outside race-Only, it will transfer the heat up to the inner race through the steel balls in-between)

Once it's hot, move it into the sleeve pocket , grab a hardened point al and tap the rotor shaft and it should start to move up the shaft for you.


hard to explain without drawing it out.

Anyways
when you get it off, take the rotor and find some room in the freezer for it- leave it in there for 1hr. In the mean time get your torch ready again, along with the new bearing ready to go, once the rotor shaft is ice cold - now your ready to heat up the bearing- out side race again, lightly heat the bearing- once it's fairly hot , grab the rotor shaft out of the freezer , get it clamped up "carefully" in the bench vice with the shaft resting on the bottom of the vice, set the bearing on the top shaft, grab a deep socket (slightly larger size of the inner race) and start to tap the bearing onto the rotor shaft to it's desired position. It should go on fairly easy with little force needed while your tapping it down.

I used this method on my 2-1/4" OD x 28"L spindle shaft-4 bearings, large bearings and it went well

Give it a go. I hope you have some success with your repair...

B,
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Old 06-29-2011, 08:50 PM   #11
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Re: Changing Bearing In Dewalt Miter Saw


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Originally Posted by UpNorth View Post
The balls and keeper come off readily then, but it takes a puller to get the inner race off.......
A cold chisel tapped into the inner race, (at 90 degree angle to the shaft), will expand the race and it will/should come off easily.

Brian has described the rest of it to a "T".

Just don't stop mid-way and take a break, get the shaft cold, the bearing hot.....and go for it.

I have a week end project coming up, involving bearings, that I am considering some dry ice for....
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Old 06-29-2011, 09:00 PM   #12
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Re: Changing Bearing In Dewalt Miter Saw


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Originally Posted by tgeb View Post
A cold chisel tapped into the inner race, (at 90 degree angle to the shaft), will expand the race and it will/should come off easily.

Brian has described the rest of it to a "T".

Just don't stop mid-way and take a break, get the shaft cold, the bearing hot.....and go for it.

I have a week end project coming up, involving bearings, that I am considering some dry ice for....
Yea Tom.- I totally agree, the colder the better- anyone have any liquid nitrogen Good point... colder the better!

B,
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Old 06-29-2011, 09:07 PM   #13
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Re: Changing Bearing In Dewalt Miter Saw


Thanks for the detail.

Here is a screencap showing the bearing on its shaft, and note that it is almost tight to the fan. The vid shows the two step process of removal, the first being to use a Dremel to score the outer race, one nice deep cut and another at 180 across, then a vise is used to break it off. The balls and keeper come out readily then, and a small puller can be tightened onto the inner race for the pull.

I wish the guy had shown fitting the new bearing to the shaft.
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Old 06-29-2011, 09:09 PM   #14
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Re: Changing Bearing In Dewalt Miter Saw


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Problem is, I live in a small remote village. ...the cost of a new saw.
I'd buy a new saw and use the old one for parts. There's something to be said for redundancy in some situations.
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Old 06-30-2011, 08:12 AM   #15
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Re: Changing Bearing In Dewalt Miter Saw


You're making this far more complicated then it is. First buy one of these as they are cheap. Most auto parts stores or Harbor Freight have them.

http://www.google.com/products/catal...ed=0CHcQ8wIwBQ

And do NOT heat anything. The bearings are not on THAT tight. They are a mild friction fit. Once you have the separator clamped tightly underneath the bearing, rest the separator on a vise and use a hammer and punch to knock the end of the armature through. Be ready to catch the armature when it drops off of the bearing so it doesn't hit the floor. Installation is also easy. Open the vise jaws just big enough to clear the armature shaft, place the bearing on the end of the shaft (the bearing is sitting flat on the vise jaws), and use a hammer and drift to hit the armature shaft until the bearing is fully seating. It's that easy really. I have done hundreds, if not thousands this way.

And there is no need to "score" the outer race. On bearings that are too close to the fan just place the bearing in the vise and tighten it until the outer race breaks. They are hardened and you can break them pretty easy this way. Then you can use the separator in the middle of the inner race, where the od is smaller, to remove it just as you do a complete bearing.
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Old 06-30-2011, 09:37 PM   #16
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Re: Changing Bearing In Dewalt Miter Saw


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Originally Posted by UpNorth View Post
Thanks for the detail.

Here is a screencap showing the bearing on its shaft, and note that it is almost tight to the fan. The vid shows the two step process of removal, the first being to use a Dremel to score the outer race, one nice deep cut and another at 180 across, then a vise is used to break it off. The balls and keeper come out readily then, and a small puller can be tightened onto the inner race for the pull.

I wish the guy had shown fitting the new bearing to the shaft.
Use a deep socket to drive the bearing on. It should tap on fairly easy. Use a socket that fits over the shaft, but will rest on the inner race. You want to drive that bearing on by the inner race.
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Old 06-30-2011, 09:38 PM   #17
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Re: Changing Bearing In Dewalt Miter Saw


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I'd buy a new saw and use the old one for parts. There's something to be said for redundancy in some situations.


For what amounts to half hour to an hour of work and a few bucks in parts?
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Old 06-30-2011, 09:39 PM   #18
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Re: Changing Bearing In Dewalt Miter Saw


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You're making this far more complicated then it is.

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Old 07-01-2011, 08:00 PM   #19
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Re: Changing Bearing In Dewalt Miter Saw


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For what amounts to half hour to an hour of work and a few bucks in parts?
It's turning out to be more than 1/2 hour so far.....

I've seen more people waste more time tinkering with things to get/keep them running instead of just buying a new one. What goes thru my brain is, "Just get another one and put it to work, making you money instead of spending so much time and energy on trying to save money". But some guys are just mechanic/tinkerer types and some aren't. I'm not.
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Old 07-02-2011, 02:46 AM   #20
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Re: Changing Bearing In Dewalt Miter Saw


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It's turning out to be more than 1/2 hour so far.....

I've seen more people waste more time tinkering with things to get/keep them running instead of just buying a new one. What goes thru my brain is, "Just get another one and put it to work, making you money instead of spending so much time and energy on trying to save money". But some guys are just mechanic/tinkerer types and some aren't. I'm not.
some people trip over dollars, to save pennies.

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