Hello scottshort,

You are correct. Part number 903373 is the part that is used in the video. Thank you for your suggestion on mentioning part numbers in the videos. I will pass it on.

-WJA

Hello sam801,

If your pad is spinning at a high rate of speed you are correct in replacing the 903373 belt. If the bearing, part number 965119SV, in the pad support is hard to turn or is rough when it turns, now is a great time to replace it.

Hope this helps,
-WJA

Never leave the pad without a piece of sandpaper on it - this will protect the hooks. Also, never use the sander without sandpaper on it. Finally, the pads wear out every so often. You can buy replacement pads at Home Depot. Or right here.

The hook and loop are the best I think. You can change papers and change back if the one you removed isn't worn out. Sandpaper discs are expensive.

Hi Bob,

The piece that came out is item #37, the clutch belt. It keeps the pad from spinning out of control when you lift the sander from the workpiece. It wraps around item #103 and the small pulley on the edge of the sander, item #37B. The clutch belt is part #903373 and is available from http://www.ereplacementparts.com .

I hope this helps with your repair!

-Mark

It sounds like you need part #37 also. Like Mark said, it wraps around #103 and #37b.

Hi Tom,

Check the pad bearing, Item #11A. It may be seized, causing the sander to spin continuously. It is part #803854 and is available from http://www.ereplacementparts.com.

I hope this helps!

-Mark

Hi Robert,

The Type Number is used by the manufacture to indicate that a change was made to the tool in manufacturing. The Type Number will be listed on the same tag as the model and serial number information. If no type number is listed then you are usually safe to assume that your tool is the earliest Type number, usually either Type 0 or Type 1.

All versions of the 333 use the clutch belt and pulley.

I hope that this helps with ordering the correct parts for your repair!

-Mark

Try replacing the bearings, the random orbit belt, the rubber spacers inside the housing that hold the field firmly in place and check the aluminum housing that holds the bottom bearing. This sometimes gets worn inside allowing for a sloppy fit for the bearing. I hope this helps.

I own a custom cabinet shop and have had this same problem over & over again. Break the sander down & check the middle bearing for seizing. I have come to this conclusion, if the sander is used for long periods at a time the bearing heats up. The grease inside the (sealed) bearing thins and seeps out. The bearing seizes so tightly a person would think it is an electrical failure. I made a tool that works along with a press to remove the bearing from shaft. You can then replace it or do as I do 75% of the time. Remove seals from the bearing, clean the bearing with lacquer thinner, repack with a good quality grease and re-insert the seals. Then press the bearing onto the shaft and assemble the sander. If you need to sand for long periods of time purchase another sander to use while the other is cooling down.

Hi Dave,

There are two likely causes. First, the clutch belt, item #37, may have broken. I have seen this belt break and then roll itself up into a ball between the pad and the underside of the sander. Basically acting like a brake.

The second item would be a bad pad bearing, item #11A. A bad bearing will put a great amount of load on your sander and cause it to slow down and act erratic.

I hope this helps!

-Mark

There are 3 bearings in your sander. Although they are "shielded" bearings, they are not airtight. If you disassemble the sander, clean around the bearings, add a little fine oil and spin them by hand and they should loosen up. Also I have let the assembly sit overnight to let the oil soak into the bearing. The bottom is held by a retaining ring and the two smaller ones are a light press fit.

Hi Sonny. The dust collector on your 333 sander definitely shouldn't be popping off from air pressure! Sounds like the press-fit seal that holds the collector in place is failing or broken. I would suspect that the collector adapter is faulty and needs to be replaced. Here's a link:

http://www.ereplacementparts.com/adapter-p-61417.html

Sonny, There are two small 'O' rings that hold the dust collector on firmly. They tend to come off when emptying the dust and if one is not watching the 'O' rings come and you do not notice it. They fit on the neck of the sander.

Hi Harold,

Hook & Loop sanding pads offer many benefits to the woodworker. They offer the ability to change sanding grits quickly. The user may remove and then reattach a sandpaper disc allowing for maximum use and reducing the cost of sandpaper.

The Hook & Loop sandpaper system consists of a sanding pad with fine plastic hooks, which is attached to the sander, and sandpaper discs, which have a looped fabric backing. The loops on the fabric backing are held by the hooks on the sanding pad.

Hook & Loop sanding pads will last through several hundred sandpaper discs with proper use. The most common cause of a Hook & Loop pad to wear out prematurely is excessive pressure being applied to the sanding pad. Only enough pressure should be applied to the sander to keep it on the workpiece and to guide the sander in the desired sanding pattern. Excessive pressure creates heat build up in the sanding pad which will quickly damage or even melt the tiny plastic hooks. Once the hooks are damaged they will no longer hold the fabric backing on the sandpaper effectively and the pad will need to be replaced. When excessive pressure is applied it slows or even stops the random action of the sander causing a large increase in swirl marks left on the workpiece.

Best results and fastest sanding will be achieved by using light sanding pressure and a proper selection of sandpaper grits. Start with the coarsest grit needed to quickly remove any rough wood surfaces or uneven glue joints. Once the surface has been smoothed and leveled you can move through the sanding grits to the desired finish. Never skip more than one sanding grit at a time. Skipping grits requires additional time and effort to remove the scratches left by the previous grit. The finest grit needed depends on the type of finish the project will receive. If a film finish, such as polyurethane or lacquer is to be used then 180 or 220 grit will be sufficient. Film finishes can have problems adhering to surfaces sanded finer than 220 grit. If the project is to receive an oil finish then a 400 or even 600 grit finish may be desired.

Hi Bert,

The clutch belt goes between the fixed pulley, #37b on the parts diagram, and the pad support, #103 on the parts diagram. To install, remove the sanding pad. Remove the old belt or any pieces of if that may be caught in the mechanism. Loop the belt around the fixed pulley. Now wrap the other half around the pad support. Reinstall the sanding pad.

You should now be able to start sanding again!

Good luck with your repair!

-Mark

it still sounds like the bearing under the pad is . take the pad off , where the belt rides the idler pully look 4 a deep groove . if it has 1 loose the screw and turn the idler 180.

No groove in the idler pulley. Completely disassembled the unit, found 3 working bearings, can't find any more. Can't figure out how this thing is supposed to work - what makes the pad spin at a different RPM than the motor? What could be broken to cause the pad to stop spinning?

the lower bearing , belt, pully. if the belt is not tight it will slip.but the lower bearing on your finger , and spin it . if go' s more then 2 times replce it

Ok if I spin the lower bearing (the one that's essentially inside of the pad support piece), the pad support turns less than 360 degrees (I haven't bothered to disassemble the bearing from the pad, that ring will be hard to remove). So there's a bit of friction there, but it does not feel like it's grinding. Sorry I'm a bit of an idiot when it comes to this stuff - is this bearing supposed to spin more easily than this?

i still think the bearing is the problem. i do 5 or 6 of those sander s a week

Hi moehl,

Hook & Loop pads offer the benefit of being able to quickly change sandpaper and being able to reuse sandpaper which offers quite a cost savings. The down side to H&L paper is that the pads do have a shorter service life than PSA (adhesive backed) pads. A H&L pad should last through several hundred pieces of sandpaper.

A H&L pad is covered with thousands of tiny plastic hooks that grip the sand paper. The most common reason for a H&L pad to wear out prematurely is applying downward pressure to the sanding pad while operating the sander. When downward pressure is applied it creates heat within the sanding pad. It doesn't take much heat to cause the tiny hooks on the pad to deform or melt off all together. Another side effect of downward pressure on a random orbital sander is the increase of swirl marks left on the work piece. When excessive pressure is applied the random function, the ability of the pad to rotate while oscillating, is greatly reduced or even stopped.

Best results with a random orbit sander will be achieved when the sander is held lightly, just enough force to control it and move it in the desired sanding pattern. Using the correct schedule of sandpaper will greatly reduce the amount of time needed to finish the sanding on your project. If your project has some very rough wood or if you need to level joints or patches start with a course paper such as a 40 or 60 grit. Once everything has been initially smoothed and leveled then work up through the grits to your desired final finish, never skipping more than one grit. Skipping more than one grit at a time will greatly increase the time and effort to remove the scratches from the previous grit. If you are applying a film finish to your project such as polyurethane or lacquer it won't be necessary to sand beyond 180 or 220 grit. In fact film finishes have a hard time adhering to very hard woods like maple or hickory if the surface has been sanded beyond 220 grit. For an oil finish you may want to sand to 400 or even 600 grit.

We offer both H&L and PSA pads for your Porter Cable 333 sander here at ereplacementparts.com.

The H&L pad is part #13904

The PSA pad is part #13901

I hope this helps with your sanding projects!

-UtahAV
-Mark

You should be able to tap it in and out with a hammer. Nice and easy.

Hey Rob,
You may have a bearing problem..if the pad support bearing locks up it will cause a lot of problems..part# 865119 also the fixed pulley probably has some wear and will need to be rotated or replaced #878884
hope this helps..?
cmoorejack

I think you're right about the belt. When the random orbit belt on those 333 sanders breaks it will cause the RPMs to go up and the pad moves differently. You'll need to remove the sander pad to replace the belt. The "belt" is really just a clear ring and periodically you'll need to replace it. It's Porter-Cable part #903373 and it can be purchased here:

Porter Cable 333 Belt / Ring

Hey riverrainstuments,
Most likely it is the bearing # 20 part # 865119 that is locked up..it is located in the pad support..also check your fixed pulley for wear.#37b .. you can sometimes loosen the screw and then rotate the support for a simple fix..but it sounds like that bearing is the culprit..parts avail at ereplacementparts.com
hope this helps:)
Craig

Inside the housing are 2 plastic studs on either side of the field with a rubber spacer slipped on it. These are supposed to hold the motor firmly in place. These spacers get worn and smashed down allowing the motor to vibrate very roughly to the point of hurting your hand. Try replacing the spacers, make sure motor is snug inside the housing. I had the same problem with a new sander. Although Bosch is a good sander I keep coming back to Porter Cable.