Keeping the Rock Saw in Working Order

Keeping the teeth in top shape is the key to maintaining productivity.
Keeping the Rock Saw in Working Order
A rock saw attached to a Toro tractor on a job site.

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Depending on the type of conditions you’re digging in, a rock saw may be in your tool arsenal. It’s the attachment you’re putting on the tractor if it’s more than just soft soil that you’re dealing with. Here are some tips that will help keep a rock saw productive on the job site.

1. Properly manage the teeth

From a maintenance standpoint, a rock saw’s teeth are the top item to pay attention to, says Bob Erickson, manager of engineering for Austin, Texas-based River City Manufacturing.

There is no way to completely prevent the teeth from wearing, but how quickly they wear and how productive you are on a job are greatly dependent on exactly how you manage your teeth use.

For one, don’t use teeth that are too large, Erickson says. He recommends a medium-sized carbide tooth — no larger than 5/16 of an inch — for most jobs.

“Whenever a customer has a problem with a saw, it seems that about 90 percent of the time it’s because they’ve installed excessively large teeth that have rounded over. They look more like a ball-peen hammer than pointed teeth,” Erickson says. “When you dig with them, you can’t penetrate and you’re really just trying to beat a hole in the rock.”

That means extra stress on the overall machine with no real progress being made. Smaller teeth may have to be replaced at more regular intervals, but until that time they’ll stay sharp enough to continue penetrating the rock, Erickson says.

Another key consideration is how many teeth to use.

“A lot of people think they’re going to make the saw more aggressive by adding a bunch of teeth, but that’s the wrong way to go about it,” Erickson says. “If you want an aggressive saw, you remove teeth to make sure they are in the cut. It’s fewer points that you’re trying to drag through the ground.”

With too many teeth, the saw won’t be able to penetrate effectively and the teeth will prematurely wear. “You end up sand-papering a hole in the ground,” Erickson says. “It’s just too many points making contact with the ground.”

There’s a middle ground to find, though.

“You can’t just arbitrarily remove teeth because when the machine is really digging hard, the vibration level increases as the number of teeth diminishes,” says Erickson. “There’s a balance to strike as far as how aggressive you can make the saw for maximum productivity, yet not tear the tractor apart.”

There’s no hard timetable on when teeth should be replaced. The best gauge is the machine’s productivity: When you’re no longer able to penetrate the rock, a tooth replacement may be called for.

A saw working in consistent, nonabrasive rock conditions in a quarry may be able to run 24 hours a day for an entire week on a single set of teeth, says Erickson. The opposite extreme may be a utility construction job where beyond the top layer of soil a contractor encounters several variants of hard rock or other abrasive materials, and teeth have to be changed out every few hours.

2. Consider the rock conditions

Carefully monitoring the saw’s productivity and tooth wear against the rock conditions will dictate what size tooth you should go with. “Start out with a carbide in the medium-sized range and see what it does under your conditions,” Erickson says.

Although he sees more issues with contractors using too large of a tooth, there are instances where a larger size may be necessary. For example, there are parts of the country where contractors might encounter sand rock.

“It digs pretty readily, but then it comes apart and becomes almost like sand,” Erickson says. “The particles that are created are horribly abrasive and will really erode teeth. That’s where a larger carbide is good because you’re trying to just prevent wear rather than needing a lot of penetration.”

If tooth consumption is high, generally the suggestion is to go with a larger tooth size, but that isn’t always the best idea. Sometimes high tooth consumption is just the side effect of difficult digging conditions, and a lesser-size tooth is still the better option.

“If you get too big of a tooth and it becomes rounded and blunt, when you get into hard digging you won’t be going anywhere,” Erickson says. “When digging gets hard is when you usually need a smaller, more pointed tooth. Now, tooth consumption might go up because you’re in tough digging, but that’s just the way it is. I don’t know of any tooth that magically has carbide you can’t destroy. Typically there are more problems with too big of a carbide than too small of one.”

3. Watch the material flow

As you’re digging, watch the spoils coming out of the ditch. That will be a top indicator of any problems, Erickson says.

“If that material is flowing out of the ditch as you’re moving along, things are happening, you are cutting. If that flow stops, you know something is wrong,” he says.

Over time, an operator will get a good feel for the machine and the way it vibrates when it’s working properly. That’s another way to key in on any potential issues, Erickson says.

4. Operating tips

One way to avoid excessive tooth wear and overstressing the machine when digging in particularly hard rock is to move the saw in reverse.

“This is assuming you’re using a standard upcutting saw, where the teeth are going from the bottom to the top as you’re moving forward,” Erickson says. “If you back up, the teeth will be coming down on the cut at the rear of the saw. Rock breaks easier when you’re cutting down on the edge of it, especially when it’s really hard cutting. It’s a condition that doesn’t happen on every job, but it’s one trick you can use.”

Also be aware of the way you’re attempting to dig a curve with the machine. “Once it’s running, a saw wants to go straight. The rear of the saw tries to follow the front of the blade,” says Erickson.

That means when the saw is being turned, the front portion is making the cut and the trailing portion is rubbing up against the sides of the ditch as it attempts to follow that exact same straight-line path.

“You can get excessive wear on the sides of blocks and the band,” Erickson says. “It’s better if you can go straight and do a curve in chunks. Pull the saw out, reposition it and go again.

This is less of a problem when you have a wider saw, but for narrow saws it’s tough to cut curves.”

5. Take care of additional routine maintenance

Outside of the teeth, maintenance is fairly routine for rock saws.

“It seems like the teeth are the only potential problem, and there is some truth to that,” Erickson says.

Before a job, do the usual walk-around and make sure there aren’t any machine components that are cracked or showing excessive wear. Most rock saws manufactured today are hydraulically driven, says Erickson, so keep an eye on that hydraulic oil level.

“And do all the normal maintenance that comes with the tractor and is covered in the operator’s manual,” he says. “Really the machine is just a trencher that you removed the trencher from and replaced with a saw.”



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