palm sander spins too fast

[dentkota.jy]

On the job site we have 3 orbital hand sanders.  All three of them have been spinning uncontrolably, so fast that you cant lift it and put it back down without leaving spin marks. Does anyone know what causes this and how to fix.  We replaced the bering and bering housing on one with no effect.  Thanks for any help.

[BMack37]

What brand? It must be a known issue if the speed control has stopped working on all of them.

Without ever tearing down and orbital sander...I'm assuming the speed control is controlled by a potentiometer, which is no longer working. It could also be controlled by a transistor which is likely easily(relatively speaking) sourced as the control board.

[dentkota.jy]

All 3 are makitas 5 inch palm sanders.

[BMack37]

Paging Mr @CATERPILLAR 

 

You can pull it apart and check the pot that controls the speed. With the tool unplugged, put a multimeter on resistance mode and test across the outside legs, when you turn the dial the resistance should change.

[CATERPILLAR]

On 9/18/2017 at 11:14 PM, BMack37 said:

Paging Mr @CATERPILLAR 

 

You can pull it apart and check the pot that controls the speed. With the tool unplugged, put a multimeter on resistance mode and test across the outside legs, when you turn the dial the resistance should change.

Lol thanks it could be on some orbital sanders they have a rubber band under the pad that break that could cause that so take off the pad and look at the rubber belt 

[BMack37]

7 hours ago, CATERPILLAR said:

Lol thanks it could be on some orbital sanders they have a rubber band under the pad that break that could cause that so take off the pad and look at the rubber belt 

 

Now I really want to take apart my ROS. Who would have known?

[CATERPILLAR]

10 hours ago, BMack37 said:

 

Now I really want to take apart my ROS. Who would have known?

I'll have to take a picture of one of my junk porter cable sanders and show what it looks like 

[foggymtnbreakdown]

I think that there are 3 possible causes for this spinning.  Cause number one is the bearing.  There are many bearings that can be purchased.  Just getting any new one will not solve the problem.  You need a 6002DDW bearing.  It makes no difference who makes it, but the ones that Makita suggests are made by NSK.  Repair places will try to sell you a 6002DW bearing.  That is not what you want.  The DDW suffix indicates a bearing with 2 light contact seals (the green rings on the NSK bearings).  If you get a bearing with regular contact seals, it will cause the spinning.  The second cause is a worn out brake.  This is a strangely shaped plastic/rubber/polymeric "ring" on the Makitas.  It is put there to stop the spinning.  If it wears out, you will get the spinning.  if you take that brake out, the sander will spin like an angle grinder.  The brake rubs against the back of the Velcro pad.  It is possible that the backside of the pad has worn down.  I can't say that I have resolved a spinning palm sander by replacing the pad, but it is possible.  If you have an old Makita sander like I do, the paperwork that came with it, shows that they upgraded the bearing to the DDW type because of the lighter grease inside.  I believe their reasoning is incorrect.   The bearing upgrade tends to stop the spinning problem, but because of the two light contact seals, not because of the grease inside the bearing.  I have taken the bearings apart, cleaned them in carb cleaner and degreased them.  This did not stop the spinning.

[Jcallesano]

On 12/19/2020 at 2:40 AM, foggymtnbreakdown said:

I think that there are 3 possible causes for this spinning.  Cause number one is the bearing.  There are many bearings that can be purchased.  Just getting any new one will not solve the problem.  You need a 6002DDW bearing.  It makes no difference who makes it, but the ones that Makita suggests are made by NSK.  Repair places will try to sell you a 6002DW bearing.  That is not what you want.  The DDW suffix indicates a bearing with 2 light contact seals (the green rings on the NSK bearings).  If you get a bearing with regular contact seals, it will cause the spinning.  The second cause is a worn out brake.  This is a strangely shaped plastic/rubber/polymeric "ring" on the Makitas.  It is put there to stop the spinning.  If it wears out, you will get the spinning.  if you take that brake out, the sander will spin like an angle grinder.  The brake rubs against the back of the Velcro pad.  It is possible that the backside of the pad has worn down.  I can't say that I have resolved a spinning palm sander by replacing the pad, but it is possible.  If you have an old Makita sander like I do, the paperwork that came with it, shows that they upgraded the bearing to the DDW type because of the lighter grease inside.  I believe their reasoning is incorrect.   The bearing upgrade tends to stop the spinning problem, but because of the two light contact seals, not because of the grease inside the bearing.  I have taken the bearings apart, cleaned them in carb cleaner and degreased them.  This did not stop the spinning.

Hi,

What about Bosch? High speed spinning makes it almost unusable for what I need to do.  I don't have the band and don't see that ring.  Is it just shot? I bought a new one today but haven't opened it yet. 

Thanks