Chances are there is an eccentric cam that engages the sander pad to make it oscillate and it may be loose or broken, causing the wild motion. Remove the pad and check. Might be time to retire the thing. Finishing sanders are relatively inexpensive.

On a side note, I did invest in a Festool 150 sander many years ago since I do lots of woodworking and I have to admit, this thing is indestructible. I have loaned it to friends over the years and it has gotten plenty of use but keeps on going. Hope it outlives me and I can put it in my will to someone!

 

I reseated the cam while reinstalling the base, and it is fairly tight. (I wondered if the problem might have been from it being too tight, so I loosened it slightly, which changed nothing) The sander is less than a year old, so I would hope it's not time to retire it already! Could it be the foam base itself? (Part 39 in the parts breakdown) It seems like there must be some irregularity in how the sander is interfacing with the wood surface, and while the pad doesn't seem too badly damaged, it is a bit beat up.

 

If it is less than one year old, it may still by in warranty.


George

 

Bought a Ryobi refurbished a couple years ago, it did the same thing, only not so violently. Sold it at a yard sale cheap. Did without one until a couple weeks ago - bought two "Hyper Tough" ROS at Walmart for $9.00 each. Put one on the shelf, using the other one, seems to work quite well

 

Looking at a parts diagram I would put my money on the balancer, part no. B04556K

 

Is the pad spinning really fast instead of RO?

I had this happen recently, that was the problem, others above have recommended the fix...

 

shoot summ: It is a finishing sander (square base), not an orbital sander. Here are some pictures of the relevant parts:

Pad: Bottom Side

Base with pad removed: Front Side

Balancer: Top Bottom 1 Bottom 2

Motor spindle with base removed

Base with bearing: Bottom Top

You can see the minor damage to the pad. The balancer seems to be in fine shape; it fits through the bearing and onto the motor spindle tightly and screws on with a central machine screw.

If I don't figure something out this weekend, I will look into the warranty.

 

Regarding the warranty: it only covers problems due to manufacturing defects, not wear and tear. And since the sander definitely didn't have this problem when I first got it, I suspect it's due to wear and tear. If I can't figure it out I might just replace all the parts below the motor spindle, but it would be nice if I could narrow it down.

 

You can buy a new model for about $50 that will give you another 1 year warranty, how much are spending on parts?

 

And he might consider a Ridgid unit.

I bought one in 2013, 3 year warranty, 2016 it died, took it to the store, got a new one.

I mentioned it has the same symptoms as the OP's Makita, just got back from my local HD with another new one since it is under the 3 year warranty still.

Not the ideal situation, but I'm not spending money on parts, or a new sander(yet).

 

Top of mind tells me that some bearing (ball or rod) has got "flatted."
Every time that comes around, in an almost random fashion, the machine jumps.

That happened to the arbor shaft bearing in my 10" Delta power miter saw.
Jamming it with dry apple wood log might have been the cause.
Anyway, it flatted one of the roller bearing rods. I saw it at the shop where I got a $50 refit.

 

shoot summ, how did you bring a 2-year-old (presumably opened) sander back to HD and exchange it? I thought only the manufacturer could honor the warranty.

 

Nope, both times HD replaced it no questions asked, warranty is 3 years. Outside of the replacement warranty I think you have to send it in and they will fix it.

The only "hitch" is I didn't have the bag that came with the sander, so I gladly let them keep the new one that came with it.

Ridgid power tool warranty is actually really good, probably the only reason to buy them IMO, as the tools are just OK. A lot of guys buy their cordless tools for the warranty as I think the batteries have a lifetime warranty.

 

I might just try that with mine; it's well within the 1-year warranty and I did get it from HD. Did you bring a proof of purchase?

 

I think unless it is Rigid you will have to send it in or take it in for warranty. I think HD has an exclusive deal going with Rigid, I might be wrong, but i had problems with s DeWalt angle grinder and it was over 90 days old so I had to take it to them to fix


A sander sure should last more then 3 years, I have a couple old Rockwell 505s that I use regularly plus a Speed Bloc and they still work fine, they don't get quite as much use since I got RO sanders, but the old 505's will sand just as fast as a RO


I still don't see why they quit making the 505 those were workhorses

 

I'll have to look and see if I still have any of my old orbitals, I used them a lot in the past, my hands still get numb thinking about it...

I use the Ridgid a lot, in addition to wood working, I use it to sand walls in prep for painting, not in a commercial sense, but on my own projects, on a couple of houses. I'd say they get way more miles on them than the old orbitals.

I really hoped HD wasn't going to replace it this time, I really want to jump into a Festool sander, looks like I'm going to have to wait.

 

It worked! I have a sander again! To help ensure this doesn't happen again for a long time, what are some tips for maintaining/taking care of my sander? (I now know not to press down too hard)

 

Buy a better sander. I bought the same one from HD. The same situation arose. BTW, it IS an orbital sander. Most are. I haven't seen a straight back and forth sander for 50 years or more. The finishing sanders that HD sells are orbitals.


I bought the Makita in a pinch because it seemed like the best made of the sanders they had and I needed a sander immediately. It got me through the job, but within a month of use, the dust collection ceased working. I cleaned it, blew it out, etc, but very little dust gets drawn up. Now after 6 months, I can barely hold onto it. Fortunately, I was able to get new brushes for my trusty old PC SpeedBlocs and they are up and running again. PC just keeps discontinuing its best tools. The 505, the 330 Speedbloc...go figure.

 

I have a very old Craftsman finishing sander. It has a rectangular bottom that takes either 1/4 sheet or 1/3 sheet. I think it is 1/3. It has two modes: a finishing mode that goes back and forth, and a rotation mode that is not random; the kind that leaves small circles everywhere. I never use that mode. Sanding is slow with it.

About a year ago, I bought a random orbital sander from Harbor Freight. It was inexpensive. I hated it because it had a rectangular dust outlet. The tiny bag that collected sawdust kept coming off enough to leak the sawdust, and I could not find a fitting for dust collection with a shop vac. It vibrated a lot, but also took off a lot of wood quickly. I returned it almost immediately. The dust collection issue was the real problem.

I replaced it with a Ridgid random orbital sander from Home Depot. It cost twice as much as the ROS from Harbor Freight, but it came with a dust fitting that fit a standard shop vac, and also a smaller one concentric with the larger one. The Ridgid ROS comes with a lifetime warranty, if you get through the online registration process.

The Ridgid ROS does not vibrate nearly as much as the Harbor Freight model, so it does not take off wood as quickly, but it works quickly enough for me. I like it.

 

My Makita palm sander is doing the same thing after only 2 years of moderate use. They sure don't make 'em like they used to! Will look into the Rigid ROS at HD.