Production roof rafter cutting has a very interesting history that most rough carpenters find enthralling. I was lucky to have lived and worked through it and still remember most of it like it was yesterday. Roof framing has always been a joy.
Production framing in general was started by the US military during WW2. So many housing units were needed in record time that the assembly line method developed in car and aircraft production industry was applied to building (see this amazing video). After the war, home contractors used these same methodologies and processes to handle the immense pent up demand for civilian housing that had been caused by the population shift to California and other parts of the West Coast for wartime production. Prior to these post WW2 days production home building was virtually unheard of as all houses were hand built by a the same crew of men from start to finish, one at a time. When the post WW2 building boom hit the Los Angeles in the early 1950's, this age-old house building method was discarded and carpenters became specialized in just one production assembly task. Contractors began throwing up wholes tracts of houses in record time using the moving assembly line method. It seemed as if one day a field stood empty and the next day it was filled with houses. Tract carpenters were paid by the piece - a price per square foot to do a certain task. For example: 5 cents a square foot to snap, plate and detail; 8 cents to stand walls; 4 cents a square foot to cut rafters; etc (mid-1970's prices). With pay for performance as the incentive, tract carpenters thought up new techniques, found short-cuts, modified existing tools to do something more efficiently, and invented new tools. From these "piece work" days came most of the specialty framing tools we use today (large diameter portable circular saws, dado saws, bolt markers, layout sticks, triangular rafter squares, framing hammers, saw hangers, etc). "Necessity is the mother of invention" as they say.
|Skil 117 "Groover" with 2" wide 7.25" diameter dado set|
By the mid-late 1960s saw shops in the Los Angeles area began to modify the Skil 107 to carry a 3.5-in. dado set in order to fulfill the desires of various framing contractors who wanted a larger birdsmouth notch than the Groover could easily produce. Nate Fletcher, formerly of Nate's Saw Shop (Anaheim, CA) was one of the principal innovators behind this and other saw modifications. Nate modified close to 200 Skil 107s during the Los Angeles building boom days.
|Skil 107 adapted with 3.5" wide 6" diameter dado set|
When the supply of 107s dwindled (these big barrel saws were never very popular on the job as they weighed over 30 lbs), several saw shops around CA began modifying the newer Skil 77 and 87 wormdrive models. Pairis Products (Phelan, CA) made a kit for the 77, while Furber Saw (Martinez, CA) made a kit for the 87. Both kits were available up until the early 1990s.
Because the dado saw required quite an investment, an optional method to gang-cut birdsmouth notches arrived on scene in the early 1960s in the form of the swing-table saw base. It was inexpensive and simple, and favored by most everyone other than the dedicated roof cutter. A swing-table saw base installed on a standard circular saw allowed it to swing well past 45 degrees and get the shallow angle required for the seat-cut. Both Pairis Products and Big Foot Saw (Henderson, NV) currently make models for various saws.
|Swing-table for Skil 127|
|Sidewinder blades for Skil 77 (red paint to repel rust)|
In the late 1980s, the Linear Link saw (Muskegon Tools, North Muskegon, MI) arrived on scene with a self-oiling 14-in. chainsaw bar attached to a Skil 77 motor body. Because it could be tilted sideways, some carpenters used it to make the ridge-cut on racked rafter material but it was very underpowered for these type of cuts and not nearly as precise as the circular saw. Another similar device, the Prazi Beam Cutter (Prazi USA, Plymouth, MA) came along in the mid 1990s. It had the same drawbacks as the competition and worse yet, no provision was made for chain self-oiling. In 1997, Big Foot Saw made available the "Headcutter", an adjustable saw table that attaches to a gas-powered chainsaw. It instantly became the best option available (and still is) for gang-cutting the plumb-cuts on common rafters. It combines a powerful gas motor, a self-oiling chain system, and a large saw foot for making accurate cuts. Fitted with a chisel-tooth ripping chain, it is hard to tell the cut made using the "Headcutter" from one made with a circular saw (the "Headcutter" also works well for precutting bundled I-joists to length or the cutting of structural insulated panels).
|Big Foot Saw "Headcutter" chainsaw base|