MP40 installing bearings on dry side

[Alazo1]

In regards to putting the bearings on. It seems that this may be the most difficult part in fixing a noisy dry side.

I was watching a video where the guy is trying to put a bearing in. He put one part in the freezer (part would shrink) and the other part in the oven which would expand. This made it easier to insert.

Do you think this would work for the mp40?. Magnet side with shaft in the freezer and bearing in the oven. I suppose the bearing cab dry up if left to heat up too much?.

 

[Alazo1]

Here is the video

 

[All_talk]

The shrink fit you are describing is typically used on parts that have a fairly heavy interference. I wouldn't think the bearing fit in the MP40 would be that tight but I've never had one apart. A little heating and cooling might make assembly a bit easier, but as you said, don't cook the oil out of the bearing. Getting the old bearing off is often the bigger issue.

Easy/successful bearing replacement on anything is often about having/making the right tools. One important note that can be missed is that when installing the new bearing never press or drive the bearing in a way the will transfer the force through the balls/rollers. The races can get dented and the bearing will be noisy and fail prematurely. In the case of the MP40, the bearing presses to the shaft, push the bearing on by the inside race, not the outside race.

 

[Alazo1]

Good info All Talk. I do plan on getting a bearing puller. I tried removing it on the only MP40 that I tried to replace the bearings and broke the magnet.

As for a bearing press, do you have one in mind that will work for this?. I now have 4 mp40's three of them have the old style dry sides. I think it would be worth like you said, having the right tools.

I do have an mp10 dry side that does not work that I will eventually try the hot and cold method with the old bearings to see if that makes it easier.

 

[Alazo1]

duplicate

 

[ScottD]

Good info All Talk. I do plan on getting a bearing puller. I tried removing it on the only MP40 that I tried to replace the bearings and broke the magnet.

As for a bearing press, do you have one in mind that will work for this?. I now have 4 mp40's three of them have the old style dry sides. I think it would be worth like you said, having the right tools.

I do have an mp10 dry side that does not work that I will eventually try the hot and cold method with the old bearings to see if that makes it easier.

I’m not sure what the diameter of the inner race of the bearing is, but if you could find a piece of pipe that would fit over the shaft and bear on the inner race it can be used to gently tap the bearing into place instead of a bearing press. I’ve also used a piece of hard wood or metal that covers the whole bearing with a hole drilled in the center to fit over the shaft to seat a bearing.

 

[All_talk]

A deep socket is usually my first try, but like Scott said, pipe or conduit of the right size will get it done. If it takes more than a light tap of the hammer and you want more control, a suitably size bench vice works as a small press.