The Mueller CL-12
Mueller has manufactured the CL-12 since 1958 with no significant design changes. In that time many competing machines have flooded the market, yet none match the capabilities of the venerable CL-12. The features that stand out are:
- Rapid manual advance and retraction
- Automatic Shut off
- Travel and Feed Gauges
- Over-travel protection
- Constant feed rate
- Machine alignment to the tapping valve
- Superior shell cutter design
- Short profile
In operation, the CL-12's features are well thought out from start to finish. When advancing the drill to the face of the pipe, the rapid advance design requires only five turns per inch and always turns easily due to the internals of the machine being in an enclosed oil bath. A mechanical dial indicates the position of the cutter at all times. A second dial, in conjunction with a knob, allows the setting of the needed travel to make the cut for the auto feed. As the machine auto-advances, this second counter will count to zero, culminating in an auto shutoff of the forward advance. If the auto feed is accidentally set to travel further than the machine is capable of, the machine will auto-disengage at the maximum travel, preventing over-travel and machine damage.
While in auto-feed, the CL-12 advances at a ratio of 100 cutter rotations per inch of travel. Precise feed means the cutting teeth are not subjected to undue strain from inconsistent loading. While performing a vertical tap, cutters in other machines can free-fall after the pilot drill breaks through the main, potentially causing broken carbide teeth. The CL-12 will maintain its optimum advance rate regardless of the orientation of the tap.
Cutters are an important concern when choosing a tapping machine. Mueller cutters have progressive teeth which start with a narrow cut and progressively widen the cut with succeeding teeth. This system allows for efficient cutting of a wide path. Wide paths are important for size-on-size taps, because the extra cutting width can be the difference between finishing the cut or getting lost in the top or bottom thickness of the main. If that happens, the coupon will stay attached to the main when the drill retracts. At that point the coupon will be lost, as any efforts to go back after it will result in the coupon being knocked into the main.
As an additional safeguard, Mueller MJ adapters have an alignment ring where they meet the valve. When used with a machined-face true tapping valve, the adapters are self aligning, ensuring even cuts.
Regardless of the tapping machine used, carbide teeth should always be touched up with a honing stone and coated with an approved cutting grease prior to making a tap on iron pipe. The fewer the number of teeth, the less time it takes to prep the cutter. Cutters for other tapping systems can have close to 100 teeth for a 12" cutter, making for tedious maintenance. The 12" Mueller cutter has only 8 carbide teeth and cuts every bit as cleanly as the competition.
Often the greatest challenge of any tap is dealing with all of the other pipes and cables that share the ditch with the tapping machine. When another crew is digging the hole, it is often short on room as well. A machine with a small profile can help in these situations. A common design for cheap tapping machines is the three pole design. In this design, the power drive unit sits behind the boring bar, and the feed screw sits behind the drive unit. These two elements add a fair amount of length to the overall machine. In contrast, the CL-12 mounts the power drive unit on top of the machine, and the feed screw is contained inside the boring bar. This configuration allows a design in which the overall machine length is not much longer than the length of its boring bar.
If you are considering purchasing a tapping machine for wet taps 4-12", there is nothing finer on the market than the Mueller CL-12. The design is robust and the unit will last for decades if properly maintained. If you currently have a CL-12 that is in disrepair and are evaluating your options, we can restore your machine to full working order. The one drawback with the CL-12 has always been the cost of repairs. We can perform these repairs for you with fast turnaround and economical pricing. We have the parts in stock, the experience to know which parts need replacing, and the knowledge to thoroughly test all functions before returning the machine.