FAQ — Comprehensive Repair

Question 1

What do shoes do, and where do I set them?

Accepted Answer

The shoes in a sander are simple features, but they can certainly cause a lot of problems if they're improperly adjusted. 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 but rather holds the wood a fixed distance from the blade.

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 it 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, and the outfeed table serves strictly as a guide. Now imagine flipping the jointer 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.

Question 2

I damaged my contact drum. How do I deal with it?

Accepted Answer

This scenario comes up quite often. 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 is deep.
• Remove the drum and bring it to a rubber roller company to have it surface ground if the scar is not too deep, or re-vulcanized and balanced if the scar is deep. Make sure you tell them the RPM it spins at.
• 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 replacing bearings that are usually rusted onto the drum shafts.
• You can dress it yourself if you're very diligent about setup. First, make sure the conveyor is parallel with the drum, then dress the conveyor belt using 60 or 80-grit abrasive. Glue 60-grit on one side of a flat 1/4" aluminum plate and 80-grit on the other. Sand the drum with the coarse side, removing only a few thousandths per pass, then clean up with the 80-grit side.

Question 3

What's the shortest piece I can sand?

Accepted Answer

The shortest piece guaranteed not to get stuck is determined by the spacing of your pinch rollers. 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 argue that shoes can hold the part down, but this is not correct — the contacting surface of the shoe does not rotate and therefore produces frictional drag. When the part leaves the shoe, it "pops up" and causes a snipe.

Question 4

What causes my parts to slip on the conveyor belt?

Accepted Answer

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. Fine sanding dust also gets embedded into the pores of the rubber.

Dressing the conveyor belt is done by installing a coarse (60 or 80-grit) abrasive belt with the platen removed. Close the machine until the conveyor just starts to get sanded — at this point make sure the sanding head is parallel to the conveyor belt or it will be sanded unevenly. Remove .005", let the conveyor rotate five times through, remove another .005", etc. Normally a total of .010"-.015" removal is sufficient. The conveyor belt will become very "grippy" from the exposure of fresh rubber.

Question 5

I have a double-head Timesavers sander. Where do chatter marks come from, and how can I eliminate them?

Accepted Answer

Chatter marks can come from a variety of sources. Most often they come from the splice on the abrasive belt — if the splice is even half a thousandth of an inch thicker than the rest of the belt, it gets pushed into the wood slightly deeper, causing a deeper cut at that point.

Platens were developed to help alleviate chatter marks. Being wider than the drum and softer than rubber, the platen spreads the splice mark over a longer distance and doesn't push the splice as deep into the wood.

Other sources of chatter include: an out-of-round or out-of-balance drum or idler roll, bad bearings on the drum, idler roll, or driver motor, and looseness in the conveyor drive system.

Question 6

How much material can I remove per pass?

Accepted Answer

This is not as dependent on motor size as most people think. Key variables include: grit (36-grit removes far more than 220-grit), conveyor speed (slower allows more removal), backing hardness (drum vs. platen), wood species (hickory and oak take more time than pine or poplar), and abrasive belt speed.

Another big factor in determining stock removal is what the grit (particles) are made out of. The most common grit is aluminum oxide. However, I like to use Zirconia in the coarser grits (100-grit or coarser) because of its excellent cutting ability (which translates to "long life").

As a general guide based on sanding oak at 25 fpm with a 70–80 durometer drum:

Grit | Max. Removal
36 | .050"
60 | .040"
80 | .030"
100 | .020"
120 | .015"
150 | .010"
180 | .005"
220 | .003"

Question 7

What's the best machine to buy?

Accepted Answer

There are a lot of good machines out there, but make sure there is support for the machine — especially after the warranty runs out.

Key questions to ask and verify:

• How long will I have to wait for a part if it isn't stocked locally by the dealer or importer?
• Are there service technicians available to help over the phone or in person?

Salespeople will often gloss over these questions, but you can imagine what you'll be thinking when your machine needs 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 brands we haven't been able to service due to lack of manufacturer support.

Frequently Asked Questions