Using Walk-Behind Saws

When using walk-behind saws, commonly called flat saws, always remember safety first. Read and understand safety precautions and manufacturer’s operating instructions before starting the flat saw. Always wear appropriate personal protection equipment

IMPORTANT: 
For complete safety information, refer to ANSI Safety Code B7.1, available through the American National Standards. Always wear proper safety equipment; wear safety glasses, safety footwear, snug-fitting clothing, hearing and head protection, and respiratory equipment where required.

Walk-Behind Saw Safety Precautions

The following safety precautions must be observed.

1. Before mounting any blade on the saw, the blade should be inspected for any damage that might have occurred during shipment, handling or previous use.
2. The blade shaft collars must be of proper diameter for the size blade being used. The drive pin must be located in the tight collar or the loose pin, and arbor should be cleaned and examined for damage before mounting the blade.
3. The blade must be properly fitted over arbor and drive pin. Drive pin must project through hole in blade and into collar. Do not force the blade onto arbor.
4. Disconnect spark plugs and use the blade shaft lock pin when tightening the blade shaft nut. Tighten the blade shaft nut securely against the outside blade shaft collar. The blade shaft has left hand threads on the right side of the saw and right hand threads on the left side of the saw.
5. The blade guard must always be in place when the saw is running. Always use a proper size blade guard for the size blade being used.
6. The operator should wear safety glasses and appropriate safety equipment at all times.
7. Never leave saw unattended while engine is running.
8. Always secure saw from rolling when not in use.
9. Do not stop the engine on a self-propelled saw while on a grade.
10. When stopping any saw on a grade, the wheels must be chocked.
11. When starting the saw, the operator should stand away from and to the side of the blade.
12. If for any reason the blade stalls in the cut, raise the blade out of the cut and check the outside blade shaft collar and nut for tightness before restarting the engine. Inspect the blade for damage. Use care when resuming a cut. Make certain that the blade is in alignment with the previous cut.
13. During cutting, do not exert excessive side pressure on the handles as a method of steering. Do not force the blade into material by lowering the blade too quickly or by increasing the speed of the saw.
14. Adequate coolant must be used when sawing with wet cutting abrasive or diamond blades. Gravity feed does not supply a sufficient water flow. The water pumps on concrete saws are “booster” pumps only and are not adequate as primary pressure source. An adequate coolant supply is required for wet cutting blades to maintain blade life and cutting efficiency.
15. The blade shaft must be operated within the specified maximum operating speed.
16. Operate engine at proper RPM. Never alter RPM or governor setting.
17. In case of an EMERGENCY “SHUT OFF ENGINE.”

Concrete and Asphalt Sawing Methods

• In concrete and asphalt cutting operations, the usual equipment used are 8, 11, 13, 20, 35, and 65 HP saws.
• Asphalt cutting and the cutting of asphalt overlayed concrete should not be considered the same type operation from a blade recommendation standpoint. In the case of asphalt overlayments, the application involves cutting both asphalt and cured concrete which gives a different abrasive level than the cutting of asphalt alone.
• Generally, the cutting of asphalt overlayed concrete is done at full depth with blades less than 18" in diameter as long as the asphalt is more than 1/3 the total depth of cut. Standard recommended specifications for asphalt overlayed concrete should be employed until the depth of the asphalt reaches 50% of the total cut. At this point, harder blades should be used which would increase the blade life.
• The larger diameter blades, 18" and above, are used in a step cutting method at cutting depths of 2" and 3" in short travel distances of 15' to 20'. This allows the blade to remain in a free cutting condition and does not slow down the cutting operation. Asphalt cutting is primarily performed at full depth. However, if the aggregate used in asphalt is larger than .750 in diameter and/or is quartz or chert aggregate, the cutting operation may have to be modified to a step cutting operation.

Green Concrete Sawing Methods

• Green concrete is cut to control cracking in large concrete pours.
• Usually saws from 8 HP to 65 HP are used for this purpose, depending on the size of the job. The initial sawing of the concrete is done within a 24 hour period at a depth of 1/3 to 1/4 of the total concrete thickness. Generally 12" and 14" blades are used with .125" or .150" widths.
• After the initial cut has been made, the joint may require additional widening for the backing rod and/or sealant. This requires a blade diameter of 12" or 14" in widths up to .500".

Concrete-Deep Sawing Methods

• Generally, deep sawing of cured concrete is done using high horsepower concrete saws and blades above 20" in diameter. 65 HP concrete saws are used in conjunction with 24", 30", and 36" diameter blades to obtain the desired depth of 8" to 14" (this is usually the standard thickness of concrete highways in North America). The blades are usually used at approximately 12,000 surface feet per minute (outside rim speed of the blade).
• The use of these blades is usually dictated by the hardness of the aggregates contained in the concrete. A cutting rate of 4' to 6' per minute is the speed of cut most operators prefer. This cut rate is usually directly related to the depth of cut. In areas with hard aggregate, it is common to make multiple passes of 2" to 3" deep until desired full depth of cut is reached. Softer aggregates can be cut using deeper passes without sacrificing cutting speed.