DeWalt GWI Radial Arm Saw - How I replaced the motor bearings Kerry Trembath June 2020

Disclaimer: I've restored/repaired seven radial arm saws and this is my second time replacing motor bearings. However, I'm not a machinist or mechanic. This is how I did it. It's not the only way and probably not the best way.

Why replace the motor bearings? The DeWalt GWI was manufactured in the 1950s. Perhaps you just brought one home from an estate sale or inherited one from your grandfather. First, congrats because you have one of the finest radial arm saws ever made. Sometimes it's obvious that you need new motor bearings because the motor makes a terrible noise when you turn it on. If that's the case, don't run it anymore until you get a chance to replace those bearings. Usually, people don't notice a terrible noise but they do notice it takes a very long time for the motor to stop after the power is shut off. The motor bearings are sealed and cannot be regreased. Over time, the grease dries up and they spin too feely. If the bearings sound dry and it takes around a minute or more to stop after shutdown, then you need new bearings. A GWI with new bearings will take less than 20 seconds to stop: that's with blade mounted. It'll stop in less than five seconds with no blade.

DIY or not? If you are reading this, you probably want to do this project yourself. You will need some special tools not found in every guy's garage or workshop. If you like buying more tools, it'll give you a good excuse to do so. If not, you can take the project to a local motor repair shop. If you take the motor apart and buy the bearings from them, their charge for removing the old bearings and installing the new should be reasonable. Page 1 of 17

Removing the motor from the saw. It's possible to do the bearing replacement while leaving the motor attached to the saw. I prefer to remove it because the process involves some hammering and I would not want to damage the motor mounts or the yoke. If you are planning to do a complete restoration then you will definitely need to remove the motor.

If your saw is set up in the standard way you'll have a power cord going from the motor into the arm and a second power cord coming out of the arm and ending in a plug. There is a switch in the arm that joins these two segments.

The two pictures below show the power switch: one from outside and one from looking up underneath the arm. Make sure the saw is unplugged. Remove the nut that holds the switch in place and the brackets (one inside and one outside the arm) holding the power cord.

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Pull the switch down and note how the wires are connected. In this one, two white wires on one side, two black wires on the other and the green wire goes around. Put a piece of masking tape on the back side of the switch to help you remember how the wires go. Remove the switch and the power cords.

If you haven't done so already, remove the guard and the blade. Rotate the yoke to out-rip mode. Put a block of wood under the motor to support it as in the picture below.

Remove the two circular plates that cover the motor mounts

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Remove the four socket head cap screws that attach the motor to the yoke.

The motor is now free from the yoke. You can use the elevation handle to raise or lower the yoke and slide the motor out.

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Note the motor plate on this saw. It's possible your motor may be different as DeWalt used more than one motor over the years. Owners sometimes swap motors too. The GWI has a very unique feature: you can choose 120 or 240 volts by flipping a switch. Most saws require some rewiring to make the swap.

Motor Disassembly. Secure your motor to a workbench and get your tools ready. You'll need a heat gun, rubber mallet, sockets, screw drivers, gloves etc. Note in the picture below the end bell with the power cord protruding is hanging out slightly over the end of the block. That makes it easier to separate it from the motor.

Arbor or Blade End Rear or Power cord end

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Remove the four tie rods that go all the way through the motor and hold on the end bells. You'll need a 11/32 socket and a flat head screwdriver

Note this saw had the tie rods installed backwards. The nuts are on the arbor end which interferes with the shaper guard.

The rear end bell has a cup in which the rear motor bearing seats. Warm up the end bell with a heat gun and it will expand away from the bearing. Wiggle the end bell and gently tap to remove it.

The rear end bell is attached to the motor with some delicate wires. Be gentle. Here's a closer look inside. If your saw's power cord needs to be replaced, you'll need to remove that 120/240 toggle switch and do some other steps to get farther into the end bell. Just having it ajar as show here is find if you don't need to replace the power cord. The power cord had already been replaced on this saw.

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Now move around to the blade (arbor) end of the motor. Tap the arbor end bell with a rubber mallet and wiggle it. Separate the arbor end bell and pull the rotor and shaft all the way through.

Remove the cover plate by unscrewing the four screws as shown below. Those four screws go into a ring (called the bearing cap) that sits between the fan and the motor bearing. As you remove the screws observe how those parts relate to one another. On reassembly, getting those four screws back into the bearing cap can be challenging.

As with the rear end bell, the arbor end bell has a cup in which the arbor end motor bearing seats. Warm up the end bell with a heat gun and it will expand away from the bearing. Wiggle the arbor end bell and, if necessary, tap gently to remove it.

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The picture below shows where we are in the process. The rotor and shaft are free of the motor. At this point, you can carry on with removing the bearings yourself or take the section that has the rotor, shaft, fan and two motor bearings down to your local motor repair shop and ask them to order your bearings and optionally install them for you.

Here are the bearings you'll need. rear (power cord) end: 88500 arbor (blade) end: 88504 (standard) or WC88504 (works but is asymmetrical - explained below) double shielded or double sealed: The original bearings were double shielded which means they have metal coverings over the bearings. Double sealed means the covers are rubber. Some say the double sealed are better for woodworking as they do a better job of keeping sawdust out.

If you choose the WC88504 instead of 88504 you have to take care to install it in the proper orientation. On one face the inner race protrudes. That side must face inward towards the motor, not outward towards the blade.

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Removing the old bearings. Clamp the shaft/rotor in a vice or similar and get a pair of snap ring pliers. Remove the snap ring and shim that are in front of the arbor end bearing.

Apply some penetrating oil and let it soak in for a while: take a lunch break or stop for the day. Do this for both bearings to help loosen them from the shaft.

Apply heat to the bearing. If you are lucky, you'll be able to grab the arbor end bearing with a gloved hand and remove it. If not, continue with the next steps to remove it. On a previous project, I watched the guys at the motor repair shop remove bearings with a tool they called a "splitter". After that I bought the Bearing Separator and Puller Set from Harbor Freight pictured below. This GWI project was the first time I used it.

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The two shiny parts are called bearing separators. I used the large one to help remove the arbor end bearing. To understand this process you need to know that it's critical to apply force only on the section of the bearing that's near the shaft. That's called the inner race. In this GWI motor, we also have a fan to deal with and it's also important to apply force only on the section that's right next to the shaft. It's tempting to apply force on the outer edges of the fan because that's much easier to access. If you do that, you'll certainly break the fan and there are no replacement parts short of another used saw.

Ideally you would pull the bearing off and leave the fan alone. However, I don't know of a way to do that on the GWI. The fan and the bearing touch each other and are coaxial. I pulled the fan and bearing off together. I secured the large bearing separator around the shaft as shown in the pictures below. The separator is arranged so that it will only push against the inner section of the fan right next to the shaft.

I used a 20 ton press to push the shaft through the bearing and fan. In the picture below I have the two thick metal plates that come with the press arranged to support the bearing separator. You can see the ram of the press poised above the shaft. When the press is actuated, the ram moves down and pushes the shaft down and through the fan and arbor end bearing. Note the guys at the motor repair shop used a much smaller bench top press for this. I happen to have this big one because I needed it once for a different project. I also heated the bearing with a heat gun so that it would expand and make this easier. I don't think that's actually necessary but I thought less force would be needed that way.

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The picture below shows all the parts from the arbor end laid out. Note the ring with the four holes between the fan and the bearing. That's the bearing cap discussed earlier. It's important to remember to put it back in place after pressing on the fan and before pressing on the bearing.

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In the picture below, I've got the whole bearing separator and puller set up to remove the rear end bearing. This is how it's supposed to work. Unfortunately, it did not work at all. The lead screw diameter is bigger than the shaft diameter, so it's impossible to remove the bearing with it. I found that out when I tried very hard to turn that lead screw and mangled the bearing. No big loss since I wanted to replace it. I included this to hopefully prevent you from making the same mistake.

I used a three jaw puller to remove the rear end bearing. It destroys the bearing because it applies force to the outer race. The lead screw has a smaller diameter, so no problem removing the bearing this time. Here are the old and new bearings: old bearings on top in the picture. I got them from my local motor repair shop for about $50.

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Installing the new bearings. The rear end bearing was very easy. I warmed it up with a heat gun and it dropped right into place. I tapped it with a hammer and socket to make sure it was seated firmly.

Before installing the fan and arbor end bearing, I cleaned up the parts with simple green. Note the micro splines on the shaft. Apparently this is to help ensure the fan doesn't spin on the shaft.

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When you press on the fan or the arbor end bearing you have to apply force only to the section right next to the shaft. To make that possible, I used a piece of common galvanized water pipe that happens to have just the right inside and outside diameter. In the picture below I've got that pipe plus the heat gun ready on the 20 ton press.

I tried heating the fan up first - hoping it would just drop down on the shaft and I could tap it into place. It didn't work out that way so I used the press to push the fan onto the shaft. I had a block of wood between the ram and the top of the pipe. I knew the fan was seated when the wood started making a crunching sound. In the picture below right, the bearing cap is in place. You have to do that before you press on the arbor end bearing.

DONT FORGET THE BEARING CAP

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The picture below shows the arbor end bearing. I used the WC88504 which is asymmetrical. The inner race protrudes on one face and that face has to be oriented in towards the fan. The masking tape is to help with getting it right. If you choose the standard 88504 it's symmetrical so you can't get it wrong.

Below left is a shot of the setup for pressing on the arbor end bearing. As before, I heated the bearing so it would expand and reduce the force needed. Below right is after installing the shim and snap ring.

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Motor Reassembly. Before reassembling the motor, I used a leaf blower to blow out all the dust. I also thoroughly cleaned the arbor end bell and wiped out the cup in the rear end bell.

Start with the arbor end. Heat the end bell to expand it and seat the bearing in the cup. Install the cover plate with the four screws: the screws thread into the bearing cap. This may prove challenging and the end bell will cool off. Once all the screws are in place warm the end bell up again and tighten the screws which will seat the bearing farther into the cup.

Insert the shaft, rotor, arbor end bell assembly through the motor and press the arbor end bell over the motor housing. The rear bearing will now be protruding out the rear and it's ready to engage with the rear end bell.

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Insert the four tie rods, making sure the slotted ends are on the arbor side as shown below left. Heat the rear end bell to expand the bearing cup and then seat it on the rear end bearing. Install the nuts and washers on the rear end of the tie rods. Tighten each of the four nuts a little and then tighten each a little more etc until all the nuts are tight and the end bells are properly secured.

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