ETS 125REQ sander wobble

[Julie]

I just purchased an ETS 125REQ sander. For the first couple uses, about 4 hours of sanding time, it worked perfectly. I could just rest my hand on the top and it would stay in one spot. It took little effort to move it slowly across the surface. I was sanding Baltic birch drawer parts batched and clamped on a bench top.

When I switched to sanding a cabinet that was already assembled and on casters, I started the sander on the top and it started jerking all around. At first I thought it was the cabinet being on casters and easily moved. I laid it down to sand the side and had the same problem. I tried different sandpaper. I did a web search and found out that I should not have been using the CT MIDI at full suction, so I turned it down to min. I tried reducing the speed on the sander. Finally in frustration I removed the sanding pad from the sander to check for anything that was loose. There was a lot of sawdust that I blew out with compressed air. I could not see any problems.

After reassembly, the sander mostly works. It still occasionally starts jumping around and at times I need two hands to control it. Most of the time it just has a consistent wobble/jerk at the same spot of rotation of the pad. I can also hear the motor sound change at the same time as the wobble. If I just hold my hand on the sander so it is staying in the same place it looks like it moves about 10mm for each wobble. The rotational speed of the pad seems to be roughly 120 revolutions per minute, so the sander is jumping about 2 times per second.

In addition, if I lower the speed from 6, the pad frequently stalls. I am not putting any downward pressure on the sander.

I hope that someone has a suggestion for something else for me to try.
The sander was a joy to use for the first couple sessions. Now it is not. In addition to the wobble, I have to always be prepared for the random times when it just goes wild.

 

[Alanbach]

Please give a detailed run down on the sandpaper that you are using.

 

[bobtskutter]

[member=40122]Julie[/member] I also have this problem with my Rotex125 in RO mode.  The machine is OK in Rotex mode but becomes a "possessed animal" in RO mode.

I've been sanding MDF and plywood using Granat 120 and 180.

The work piece is 2' x 4'.  The wild behaviour doesn't happen all the time, sometimes it's "calm" and sometimes its trying to rip my arms off.  I think it's where the workpiece is a little rough and the sanding disk has more to bite on to.  If I try to reduce downwards pressure to a minimum the problem is reduced.  If I just power through it, eventually it all calms down but my arms are finished by that point.

FYI, the Rotex is a two handed machine, I'm not sure you can use an ETS125 two handed.

Bob

 

[peter halle]

In my use it is not unusual for my ETS125 or any of my other Festool sanders to start too act like this as it meets different grain directions dips, thickness variations, etc.  Lowest suction and sometimes lower rotation speed can help.

Peter

 

[Julie]

While I do understand that grain can cause craziness, I would have expected after sanding with multiple grits to have that go away. Maybe I am just naive.

I often use my ETS125 two handed, with one hand holding the vac hose. It is very sensitive to the weight of the hose and in some sanding positions it is required.

After more hours of sanding, I think the only real issue that I have is the wobble that is consistent and that was not there initially.

I am also curious about the rotational speed of the disk that I should expect when set to high speed. I put a sharpie mark on the upper part of my pad to allow me to count rotations. 2 per second is the fastest that I see, but it often slows down. Would anyone be willing to check and report the speed of their sander?

BTW, I have tried both Granat and serious Grit sandpaper. I have tried both new and well used.

After another hour of sanding yesterday, I am adding to this post.

The sander seems to stall frequently unless it is set to 6. Even at 6 it is very sensitive to the amount of pressure. When sanding a horizontal surface I do not put any pressure on the sander and also hold the hose so that it does not add weight to one side. A slight amount of downward pressure on the sander with my hand causes it to stall.

When I encounter a spot that causes the sander to want to go crazy, I lift up slightly so the sander has almost no pressure on the wood and it behaves better.

I have tried some sanding in a vertical position and it is very hard to apply just enough pressure to cause the sander to start rotating, but not too much which causes stalling.

 

[Alanbach]

I have a couple of things to try in addition to what you have already tried.
1. As Peter said, turn down the suction on your dust extractor. I suggest that you turn it down as far it will go.
2. This is a little weird so bear with me. As you approach the sander take your right hand and put it under the hose from left to right. Then bring your hand back to the back of the sander where the hose attaches. This will cause the hose to wrap around your arm and will make it almost impossible for the sander to heel (lean back).
3. Don’t expect this sander to work aggressively in low grits. This is not the sander you want or need when you have to hog off a decent amount of material.
4. Barely use that left hand, almost no downward pressure, just steer.
5. Move across or up and down or my preference is to move across the piece in figure 8’s. Medium speed, not too slow and not too fast.
Let us know if you try these steps and what the results are.

 

[Julie]

I have a couple of things to try in addition to what you have already tried.
1. As Peter said, turn down the suction on your dust extractor. I suggest that you turn it down as far it will go.
2. This is a little weird so bear with me. As you approach the sander take your right hand and put it under the hose from left to right. Then bring your hand back to the back of the sander where the hose attaches. This will cause the hose to wrap around your arm and will make it almost impossible for the sander to heel (lean back).
3. Don’t expect this sander to work aggressively in low grits. This is not the sander you want or need when you have to hog off a decent amount of material.
4. Barely use that left hand, almost no downward pressure, just steer.
5. Move across or up and down or my preference is to move across the piece in figure 8’s. Medium speed, not too slow and not too fast.
Let us know if you try these steps and what the results are.

This is pretty much how I ended up doing it.
I did reach out to Festool and they told me to send in the sander for repair because it should not have a wobble.

 

[Alanbach]

Cool! Let us know when you get it back!