CNC Router Shoots Production Through the Roof
Use of a four-axis CNC router dramatically increases gun stock production at California shop.
Ironwood Designs, a San Jose, CA-based designer and manufacturer of wooden gun stocks, has more than tripled since replacing a manual pantograph with a four-axis CNC router.
Made of high-quality hardwoods, Ironwood Designs’ products are purchased by individual gun owners, gun dealers and firearms manufacturers to replace the inexpensive plastic or softwood stocks of many imported military guns such as the FN-FAL and the AK-47. Ironwood Designs also sells a four-piece wooden set that includes the butt stock, pistol grip and an upper and lower hand guard.
For the first step in making a gun stock, Ironwood Designs used a Zuckerman copy lathe to automatically carve a wood block into the desired 3-D profile. The machine cut the block from an over-sized plastic pattern of the gun stock. The pattern and the wood block would spin in tandem while the machine’s cutter carriage and a sander carriage traversed the block, delivering a clean finished piece in 1 to 3 minutes.
This part of the production process, which was handled by an Ironwood Designs employee, needed no improvement. The next step was the problem.
After parts were cut on the Zuckerman machine, they needed further cutting to carve out the inlets where the stock fits into the rifle and areas where parts, such as the swivel and the butt plate, are later attached to the stock. After running the parts through the copy lathe, which was located in the company’s shop, Shuster took them to his home workshop, where he used a manual pantograph to make these additional cuts. The pantograph had four spindles so four parts were cut at once. According to Shuster, it was a back-breaking process that was both slow and inaccurate.
The machine cut with straight flute bits. So although some parts could be done with one pass of the bit, others required three or four bit changes. It took an average of 15 minutes to complete the carving process for four butt stocks. Error was the other problem. Using a pantograph involves manually following a pattern with a stylus. If Shuster’s hand slipped, four parts were damaged at once. He estimates that he had a loss of between 10 and 15 percent due to carving errors. Also, as the pattern eventually wore out, edges of the cuts were less sharp, giving them what Shuster calls a “fuzzy” look. Templates would also get kinks and other irregularities, all of which were transferred to the finished product.
Accuracy and Speed
According to Shuster, the Techno CNC router is capable of carving the cutouts in about one-fifth the time it took to do them by hand. The machine also automatically repositions a part and cuts all sides in one operation, enabling it to run unattended.
Shuster says he required a machine with four-axis capability because cuts are needed on all sides. A four-axis machine has dual spindles, one that holds the part and one that holds the cutter. The cutting program directs the x, y, and z motions of the cutter as well as the positioning of the part. After one side has been cut, the part can be rotated, for example, to allow access to the other side.
“With a four-axis machine, repositioning happens automatically, so the cutting goes faster and it’s completely unattended,” Shuster says. Using the four-axis machine, it now takes Ironwood Designs only 3 minutes to cut four butt stocks, compared to 15 minutes needed with the pantograph.
The CNC router is located in the shop near the Zuckerman copy lathe; one employee runs both machines. “We now produce 100 pieces in four hours. Previously that took us two days,” Shuster says.
The quality of the cuts is also improved. “There is less tearing of the wood because the spindle is spinning at 18,000 rpm,” says Shuster. “Also, if a cut is off by 0.010 inch, I can modify the program and easily fix it.
“Now we can produce factory-quality pieces. You can’t distinguish our stocks from the original military production except that we use a higher grade of wood,” he continues.
New Business Opportunities
Designed in the 1950s, this rifle had been out of production for years. But surplus versions are being imported and new ones are being manufactured in the United States from old military specifications. Ironwood Designs now offers replacement parts to manufacturers, who will resell them as accessories. The parts are also sold to smaller gunsmiths who build FN-FALs for customers, as well as to private owners of the rifle who wish to retrofit it with a nicer wooden stock.
In addition to this new product, for which Shuster anticipates a big demand, Shuster says he plans to use the CNC machine for other projects. For example, plans call for offering replacement stocks for common guns, such as hunting rifles, which will be easier to install than those currently available. Most replacement stocks, he explains, come semi-finished, i.e., the sides are carved but not sanded, so tool marks are visible. This requires the gun owner to fit the rifle to the stock, a process than can take hours of filing. Shuster says he plans to cut these stocks on the CNC machine for a level of accuracy that has been previously unavailable. “My kits will be innovative because they give you drop-in fit,” he says.
“We no longer advertise and yet our volume keeps increasing,” says Shuster. “With the four-axis CNC machine, we’re now able to produce replacement stocks for anyone who wants one.”
Have something to say? Share your thoughts with us in the comments below.