Woodworking Machine Repair FAQ

Mr. Olynik, the shoes in a sander are simple features, but they can certainly cause a lot of problems if they’re improperly adjusted. Part of the problem stems from what they’ve been called throughout the years; some folks call them “hold-down shoes,” “pressure shoes,” or “pressure plates”. This alone is incorrect and suggests an act of pushing wood tight to the conveyor.

Shoes, instead of holding the part tight to the conveyor belt, prevent the part from “popping up” into the sanding head. They serve as a guide, similar to the fence on a table saw; the fence does not push the wood into the blade of the saw but rather holds the wood a fixed distance from the blade.

Yes, something must hold the wood down tight to the conveyor belt, but that is the function of pinch rollers. Pinch rollers push the wood against the conveyor belt and roll with the wood to prevent the wood from getting stuck.

The best way to describe how shoes operate is to picture how a jointer operates: The infeed table determines the amount of material the head will remove. The outfeed table serves strictly as a guide for the existing wood. If the infeed table is set above the cutter head, a trailing snipe will occur. If the outfeed table is set above or below the cutter head, a leading-edge snipe mark will result. Now, to apply this knowledge to a sander, imagine flipping the joiner upside down.

The infeed table becomes the infeed shoe, and the outfeed table becomes the outfeed shoe. If either shoe is too high or too low, snipe will result. The outfeed shoe must be in line with the cut of the sanding head, and the infeed shoe should be set above the sanding head by the amount of material the head will be removing.

More of this subject is written in our “Widebelt Sander Handbook,” which can be purchased as part of our “Comprehensive Sander Kit”.

Thanks for writing. I come across this scenario quite often. It’s very easy to do, and the damage occurs immediately when you try to sand something far too thick for the sandpaper to manage.

There are a few methods to solve this problem:

Replace the drum with a new one if the depth of the scar on the drum is deep.
Remove the drum and bring it to a rubber roller company (found in most phone books under rubber rollers) to have it surface ground if the scar is not too deep or re-vulcanized and balanced if the scar is deep – balancing should be mandatory. Make sure you tell them what speed it is spinning (RPM).

If you're somewhat local, we have a machine we use to grind your drum while it's still in the machine. This saves time and the cost of having to replace the bearings that are usually rusted onto the drum shafts.

You can dress it yourself if you're very diligent about setting up the machine prior to dressing the drum. First, you must make sure the conveyor is parallel with the drum and then dress the conveyor belt using a 60 or 80-grit abrasive. Then, find a piece of MDF that you absolutely trust to be flat and of uniform thickness.

Glue 60 grit abrasive on one side and 120 grit abrasive on the other side. The abrasive should be new. You'll have to find a way to “fool” the machine into starting the drum without sandpaper on.

Then, simply turn the conveyor belt on and keep "sanding" the sandpaper board (coarse side up) with the drum until you're down to the desired thickness. Remove only a few thousandths of an inch per pass, or you risk melting the drum. Seeing a little smoke from the heat created by sanding the rubber is normal. Clean up the coarse 60-grit scratches by turning the board over and sanding the drum a couple of times with the 120-grit.
Again, thanks for writing, and feel free to contact me by phone if you have any more questions.

John, thanks for writing. The shortest piece I will guarantee not to get stuck is determined by the spacing of your pinch rollers. The pinch rollers' function is to hold the part tight to the conveyor belt. As long as at least one pinch roller is pushing down on the part, the part should be able to go through the machine.

Some people can argue that the shoes can be adjusted to hold the part down, but this is not correct. The contacting surface of the shoe does not rotate and, therefore, produces frictional drag as the part tries to pass.

When the part does leave the shoe, it "pops up" and causes a snipe. We've developed some pinch rollers that can be retrofitted into some models of double-head Timesavers sanders where there should have been a pinch roller placed between the two heads. Call us for details if you're interested.

Mike, Parts slipping is usually caused by one of two things: The pinch rollers are improperly adjusted, or The conveyor belt needs dressing. Conveyor belts are made of rubber and, with exposure to air and light, become glazed on the surface. In addition to the natural glazing, the fine dust from sanding also gets embedded into the fine pores of the rubber.

Dressing the conveyor belt is done by installing a course (60 or 80 grit) abrasive belt. Make sure the platen is not being used. Close the machine until the conveyor just starts to get sanded. At this point, it's very important to make sure the sanding head is parallel to the conveyor belt, or the conveyor belt will be sanded unevenly.

I usually take a marker and draw a line from left to right of the conveyor to check for parallel sanding. The dust collector can be on but should be dampered to prevent lifting on the edges. Dressing the conveyor is a matter of sanding approximately .020" to .030" off the surface in .005" increments. You will notice the conveyor belt will get very "grippy" from the exposure of fresh rubber. More information can be found in the "Comprehensive Sander Kit"

Thanks for writing, Ryan. Chatter marks can come from a variety of sources. Most often, they come from the splice on the abrasive belt. Let’s assume the splice is one-half or one-thousandth of an inch thicker than the rest of the belt.

As the splice comes around, the splice is pushed into the wood by the contact drum and penetrates the wood just slightly deeper than the rest of the belt, causing a deeper cut at that point. This results in chatter marks. Platens were developed to help alleviate the dreaded chatter mark. The platen, being wider than the drum, spreads the splice mark over a longer distance.

Also, the platen is softer than the rubber drum; this means the splice isn’t pushed into the wood as deep and hard as the drum would push it. Other sources of chatter can come from:

- An out-of-round and/or out-of-balance drum or idler roll

- Bad bearings on the drum, idler roll, or driver motor

- Looseness in the conveyor drive system.

More of this subject is written in our “Widebelt Sander Handbook,” which can be purchased as part of our “Comprehensive Sander Kit”.

Thanks for writing, Scott. This is a frequently asked question. It is not as dependent on the size of the motor as most people tend to think.

There is no quick and easy, exact answer to this question; however, let’s consider the following variables:

A 36-grit belt can obviously remove more material than a 220-grit belt.
Slower conveyor speeds will allow more time for the abrasive to remove material.
A harder backing (drum durometer) will allow more material to be removed than a softer backing (platen or soft rubber drum.)

Harder species of wood (hickory, oak) take more time to cut than softer woods (pine, soft maple, poplar)
Faster spinning abrasive belts cut faster than slower spinning belts.
Although there are several variables here, I tend to use the following chart to determine how much material can be removed.

GritRemoval 36.060”60.040”80.030”100.020”120.015”150.010”180.005”220.004”

This chart can be used on average conditions.

Average: Sanding oak with a conveyor speed of 25 fpm with a 60-70 durometer drum.

This information is based on both experience and consulting with Ty Lehrke (Timesavers) and Foster Grant with Norton Abrasives (www.NortonAbrasives.com)

More on this subject is written in our “Widebelt Sander Handbook,” which can be purchased as part of our “Comprehensive Sander Kit”.

What's the best kind of machine for me to buy?

We tell everyone the same thing: that there are a lot of good machines out there, but to make sure there is support for the machine - especially after the warranty runs out.

Some questions to ask and verify:

How long will I have to wait for a part to arrive if it isn’t stocked locally by the dealer or by the importer if it’s a foreign-built machine?

Are there service technicians available to contact for either help over the phone or in person if need be?

These are questions that salespeople will often times gloss over with a sugar coating. However, you can imagine what you’ll be thinking when that day does arrive that your machine does need service. You should have a strong sense of security before that day arrives.

We’re always available to provide input regarding brands of machinery we’ve serviced (and haven’t been able to due to the lack of manufacturer support.)