Sawsmith stays the course

Interviewed by Alan Rooks, editorial director of CUTTING TOOL ENGINEERING Magazine. David Otter, president and owner of Tru-Cut Saw Inc., Brunswick, Ohio, has been a master sawsmith for 42 years. He and his brother, Alan, are part of a small global fraternity that still practices the craft. The interview below first appeared in the December 2007 issue of CUTTING TOOL ENGINEERING.

CUTTING TOOL ENGINEERING: How did you become a master sawsmith?

David Otter: I was born in England in 1945 and went into a saw smithing apprenticeship program in Sheffield when I was 15, learning how to level and straighten circular saw blades. I signed an agreement with a company that made me a bound apprentice for 6 years. It was like bloody slave labor, but the company guaranteed to send me to college and give me a trade, and that’s what they did.

CTE: How did you come to the U.S.?

Otter: In 1974, I was recruited by Disston Saw, a U.S. company that was looking for a sawsmith. I stayed for a month and then went back to England. In 1976, I was recruited by a company in Rockford, Ill. I worked for them for 5 years, then realized since I was getting all the headaches and gray hairs anyway I might as well work for myself. I started my own business in 1981 in Brunswick, Ohio. I chose the Cleveland area because it is in the industrial heartland of the U.S.

CTE: What is saw smithing?

Otter: Every circular saw blade requires some type of straightening to create a flat, even plate. Instead of blacksmithing—working with hot metal—sawsmiths hammer cold metal, using hammers with different weights, from 1.5 lbs. up to 15 lbs., on plates with thicknesses from 0.08" to 0.75". We lay the blade horizontally on a round-block steel anvil. On the back of the anvil is a 1" or lower backboard that positions the blade at a 25° to 30° angle. We draw a straight edge across the center of the plate to find the low and high spots, called hollows and lumps. We are looking for the right tension—the amount of flexibility or movement—in the saw blade. We apply mechanical pressure to see if the saw body drops away from the straight edge. If it drops away a little, say 0.0010" to 0.0015", and if you see daylight, that’s the right amount of tension. If it moves more than that, from 0.0020" to 0.0050", the blade is loose and has hollows, meaning there’s too much movement. If it goes the opposite way, into a lump, the blade will twist in use like an airplane propeller. By hammering on the rim of the blade, we can draw and stiffen the plate. If we hammer in the center, near the bore, we loosen it, creating more movement.

CTE: What is the next part of the process?

Otter: After we hammer the blade, we check it against the straight edge and then mount it on a spindle. There, using a dial indicator positioned about 1" from the rim of the blade, we manually rotate the blade it to see if it is deflecting to the right or to the left. If there are any high and low spots, we mark them, take the blade off, tap it and then put it back on the spindle. CTE: What is the ideal plate? Otter: You want a neutral plate that is not too fast (too stiff), and not too loose (not stiff enough). It should have just the slightest amount of movement so that as the saw blade heats up while cutting, it goes from having a little flexibility to stiff neutral.

CTE: How many sawsmiths are there in the world?

Otter: In 1972, Disston did a worldwide survey of master sawsmiths, and at that time, there were 500. There are probably a lot fewer today.

CTE: Can the saw smithing process be mechanized?

Otter: Some of the work can be done with a roller tensioning machine that applies pressure around the rim. We stiffen the plate as much as we can with the machine, but the final work must be done manually. Smithing requires several senses—sound, sight and touch. It’s a skill you develop only through repetition. It’s precise work because we are only moving material a few thousandths. Often we are just peening the surface. For example, the saw smithing process works well on very thin plates, such as disposable, 0.118"-thick blades. We believe we are the only U.S. company manufacturing disposable blades; Japanese companies are exporting about 20,000 to 40,000 disposable blades a month to the U.S. Vendors are making flatter steels by adding chrome and other alloys, and this makes the smithing process easier. We work with a couple of U.S. vendors that do a good job, but we still have to fine-tune the steel before we process the blades.

CTE: Do all saw blade manufacturers use smithing?

Otter: No. Many companies purchase plates in a flat, neutral state, but when you manufacture blades, you generate heat in the body by brazing on the carbide tips, so you get distortion. We smith each blade two or three times. After brazing, we do smithing to stiffen and balance the blade prior to grinding. After grinding, we check the blade and smith it again before coating. When it comes out of the coating chamber, we do a final inspection to check runout and smith it again if necessary. Many shops that are cutting solid bar stock or tubing have to hold ±0.0005" or are cutting the solid material to a specific weight, so they need a nice, true blade.

CTE: Do you smith every blade?

Otter: Yes, and also every blade that comes back in for service. My brother, Alan, and I do all the smithing. My son, Richard, and I agreed that we need another smith. I’m 62 years old, and I’m getting too bloody old for this game. We need to start a training program! The skills we use originated from blacksmithing in places like England and Japan for hard forging of swords, and the tradition has moved on from there. But it still is a dying art. Who wants to pound on circular saw blades all day? There is nothing glamorous about it, but there’s no replacement for it either.