Picking the Correct Cutter System

Dig with Efficiency — Match Your Trencher Chain to Your Attachment and Application

By Tim Passon

At first glance, all trencher chains might look pretty much alike. They all boast round rollers, round pins, bushings and rectangular side plates made of steel. But when it comes to choosing a chain for your compact trencher attachment, not all chains are created equally.

Only a closer examination can reveal the quality construction in a chain. The quality of steel, for instance, will have a direct impact on the hardness achieved during the heat-treat process. Component parts that are broached, instead of stamped, will have a considerably better fit — and subsequently add to chain life. Attachments generally come with either a 34,000- or 50,000-lb tensile strength chains.

Of course, it’s virtually impossible to evaluate the quality of a bare chain just on looks alone. This is not to say the quality “look” of the bare chain is not important, because it is, but what’s even more important is application — choosing the correct cutting system that matches the conditions you plan to trench. Generally the manufacturer has already chosen a chain that will best match the power of the compact trencher attachment, but will it match the application?

It’s best to shop around and ask questions about the chains and their intended applications. Below are some of the most common cutting systems available:

1. Cup Cutter
The cup cutter chain is the original cutting system and has been around since the 1950s. It is still the most efficient way of digging in soft to medium soil.

2. Welded Scorpion or Shark Chain
A welded Scorpion Chain is a great chain in almost any condition with the benefits best felt in hard ground. Sometimes referred to as “the throw away chain” because the cutters will remain productive for the life of the chain.

3. H-Plate
The Welded H Plate chain is effective in hard rocky conditions. The conical style cutters are replaceable. H-Plate is definitely for the toughest ground conditions.

4. Bolt-on Scorpion
The Bolt-on Scorpion is also a great chain in rocky and hard soil. The bolt on feature allows the flexibility to change the width of cut.

5. Bolt-on Alligator
The Bolt-on Alligator is also a great chain in rocky and hard soil. The bolt on feature allows you to change widths and the conical style bits are replaceable. 

As you can see there are quite a variety of cutting systems. In recent years the mixed or combination chains have also become quite popular. The fact is that no matter how well you know your digging conditions, you are bound to encounter unexpected veins of hard ground. By mixing an Alligator or a Scorpion with cup cutters you can be better prepared for those unexpected tough conditions. The carbide will break up the soil and the cup cutters will help assist in the clean out of the trench.

As mentioned earlier, there is not one system that best suits each digging condition. However, if you are in it for the money, regular chain maintenance is a must. When it comes to chain maintenance, Underground Tools Inc. (UTI), manufacturer of a wide range of wear parts and chains for the underground construction industry, recommends the SAVE method. 

1 . Sharp Cutters: There is no substitute for sharp cutters. Anyone who has ever used a chainsaw can appreciate the difference sharp cutters make. When you saw through a log with sharp cutters, you will notice the saw does the work and not you. As the cutters become dull, you do more work than the saw. The same holds true for the trencher attachment. As the cutters dull, the attachment requires more horsepower and you are wearing out your machine just like you would your body. Cutting with dull worn out cutters is by far the greatest expense you will encounter. 

2 . Always put a new sprocket with a new chain: The chain is designed to run on sprockets of the same pitch. As a sprocket wears the teeth become deformed. Consequently, they no longer are the same pitch as the new chain you just installed. This will cause elongation of the chain, which will rob you of service time. Typically a new sprocket will cost less than 10 percent of the price of a chain, but will add 15 to 20 percent to the life of the chain. In addition, new sprockets will enhance machine performance and eliminate extra wear and tear on other components, translating to overall cost savings on the job.

3. V- Pattern: Over the life of a chain, cutters will wear out or break, or maybe a change has been made to the cutting systems width. It’s been said many times before — “No problemo, just take off a couple cutters here and add a wider cut there and you will be good to go.” WRONG! Think about digging a hole through sod in order to plant a tree. Would you use a shovel or would you use a spade? Of course you would use a spade. The same holds true with a trencher.

By indiscriminately replacing worn out cutters or adding cutters here and there, you have changed your system from a spade to a shovel. You are asking for lost productivity and added wear to other components of your machine. The best advice is to do the right thing and disassemble and then reassemble you chain with a proper V-shaped pattern. Typically, it is best to have a cutter slicing in as many places as you can, especially in hard ground. A pattern should graduate from center cut to your desired width in increments of 1 to 2 in., depending on the severity of the ground conditions. Your local dealer should be able to provide you with a pattern outline to assist you in assembling the best V-pattern for your conditions.

4. Experience: Like anything there is no substitute for experience. Experienced operators understand that all conditions are not best suited for all out chain speed. Matching chain speed to ground speed is essential for peak performance and productivity. Cutting angle, speed, depth, ground speed and volume are all performance enhancing opportunities that come with experience. Over tightening of a chain will not only promote wear, but it will also rob your attachment of valuable horsepower. The rule of thumb for chain tension is, while the boom in extended in a horizontal position, adjust the chain to sag approximately a distance equal to the pitch of the chain (pitch is the center of the rivet to the center of rivet on the chain).

In short, choosing and then maintaining the right cutting system for your trencher attachments is of utmost importance. And though many trencher attachment chains look alike, each one is engineered for an individual task. Generally the manufacturer has already chosen a chain that will best match the power of the compact trencher attachment you own, but depending on your various applications, you may need more than one. And with companies like UTI selling chain and cutting systems for the last 30 years, you are guaranteed to find the exact trencher chain to give you added performance while not emptying your pocketbook.

Tim Passon is the co-owner of Underground Tools Inc., St. Paul, Minn.