Replacing Drive Belt on PM-1054V

[erikmannie]

About a month after I got this variable speed machine, I stalled a 1-1/4” end mill while making a plunge cut in steel sheet. I assume that is where this problem began.

When I first got the milling machine, it’s operation was pretty quiet. After I stalled that big end mill, the machine was noticeably noisier. It still works fine, & I have put at least 300 hours on the machine following the stalled end mill.

I took off the side covers to inspect the belt, and the drive belt, while still operational, should be replaced in order to get back to the original, quieter noise level.

Precision Matthews was very good about supplying me with a quality replacement belt at no charge.

I am a UPS driver, & one of my customers works on heavy equipment (backhoes, excavators, etc.). He is coming out today, and him and I are going to install the new belt together. This is a paid job for him, as it should be, because he has at least 40 years mechanical experience.

After he is gone, I will upload all the pictures that I took, and share what I learned.

Here is the new belt that we will install:

I have seen a couple videos on YouTube of people doing this. The mechanic coming out today has never worked on a knee mill.

 

[Winegrower]

If this is the variable speed model with the Reeves drive, and it’s pretty equivalent to the Bridgeport design, better follow the service manual closely. There are a couple of tricks that make the job much easier.

I did this repair at the railroad museum, and sadly I don’t recall all the tips.

 

[erikmannie]

We just completed the job, and it took us 3 1/2 hours. The headline is that he would not accept payment! I was fully prepared to pay him hundreds of dollars.

The guy is obviously a mechanical wizard. I took a lot of pictures, and I will upload them now.

The old belt was in bad shape!

 

[erikmannie]

Him & I watched 3 YouTube videos so that we knew what we were getting into.

Here is the electrical for the 3HP, 3 phase motor.

 

[erikmannie]

The ***hot tip*** is to use two M6 bolts to compress the spring in the photos below.

The bottom end of motor shaft is stabilized with a bearing that seats in the bottom of the housing.

We used a bearing puller to remove this bearing to expose the shaft.

It is at that point that you use two 35mm long M6 bolts to keep the spring compressed! The spring is held in place by a snap ring on the shaft.

To restate: remove the bottom housing, pull the bearing from the end of the shaft, & then install the 2 bolts to keep the spring in place.

In the photos, those 2 socket head cap screws are M6 bolts that I supplied, and these are removed after the belt replacement task.

 

[erikmannie]

After disconnecting the 4 wires and 4 bolts, we pulled off the motor. It was nice to have 2 people available for this, but I don’t think the motor weighs more than 45-50 pounds.

 

[erikmannie]

Before removing the upper housing, one has to disconnect the panel for the variable speed control. It Is very highly recommended to keep that panel connected to the upper housing. It is attached by a very sturdy chain.

The tricky thing here is that there is a *tilting plate* that needs to be disconnected. On my machine, this tilting plate was an orange/rust color.

The tilting plate is held on by 2 socket head cap screws with bushings on them.

You have to go through the top of the housing to remove these 2 screws. As with the variable speed panel, the tilting plate stays connected to the upper housing.

 

[erikmannie]

Upon reinstallation, this tilting plate is attached to the (aluminum?) casting which you can see in this photo. This casting is on the shaft (the top of the spindle?) between the bearing and the top half of the pulley.

 

[erikmannie]

I didn’t take any more photos after this point.

Once you have removed the motor as well as the upper housing and set them aside, one puts the new belt over the front pulley.

I am pretty sure that it requires 2 people to get the belt around the rear pulley.

In order to get the new belt on to the rear pulley, the motor is installed back and down.

To clarify, when you’re pulling off the motor, you pull up and tilt forward.

So when you reinstall the motor, you do the opposite of this: tilt rearward and drop ‘er in.

***Another huge tip*** is to have the new belt shoved as far back as possible on the front pulley because it is pretty tight getting it around the rear pulley. The way that him and I shoved the belt deep into the front pulley was by lifting the upper pulley and pulling the belt tightly. I would bet that other people have used a dowel to hammer it on even further.

 

[erikmannie]

So at this point is the scary and frustrating part. It will definitely seem like the belt is not going to slip on to the rear pulley. This is the part that takes 2 people.

You start the belt on the rear pulley, and then rotate the pulley around. Him and I had to have the motor oriented in just the right position in order to get this to work.

And “just the right position” was not the final resting place for the motor. You are definitely positioning that motor in such a manner as to get enough space to allow the belt to slip on.

To recap: get the belt started on the pulley, position the motor on the axis that gives you the most room, & then rotate to bottom of the rear pulley to get the belt to slip on.

If you can’t get this to work, you need to (1) shove that belt farther back on the front pulley, or (2) reposition the motor to get some more room, or (3) get a stronger person to rotate the pulley around.