While common place today, the standard design of the time still used the old fashioned and almost useless design of relying on a wing nut to tension the blade.
MF 1949 catalog. The No 84 red handle saw, is also a Huxtable design and sometimes referred to as a Buck Rogers tools
MF 1981 catalog, notice they still made the old fashioned wing nut frame
and the model is now 300-01
Design patent D140,810 assigned to Francesco Collura 10 Apr 1945
This is for the overall form, the design. The overall shape, including the lever mechanism is shown. It is very close to the final product, except that the frame does not appear to be adjustable.
The biggest flaw in the hacksaw design of the day, was the inadequate amount of tension that you could exert on the blade. Unlike the similarly designed, albeit more delicate coping saw, where the frame rigidity play a role in tensioning correctly a very narrow blade, the smaller sized and thicker frame of the hacksaw, is more than rigid enough to not be a major factor in tensioning.
Typical tensioning system on hacksaws, still in use today. From an old Union hacksaw
There was also the now typical, adjustable frame hacksaw, held, 8, 10 and 12 in blades, which rely on a pivot point bearing against a pin for rigidity, but they still sport the poor man way of tensioning the blade; the Wing nut
The beauty of a high tension frame permit to easily boost the tension to 600 pounds, or 50,000 Psi, depending on the frame construction.
Lennox Hi-Tension hacksaw, pic from LV site. Note the 2 hands hold on the saw. This hi tension translate in a tautly stretched blade, which means there is hardly, if any, deflection of the blade during the cut. This greatly increase the accuracy of cuts and reduces frustration in the results :-) Cam lever action is the key to this design.
MF ad in Popular Mechanics Oct 1948, announcing the new No 300
Back to Buck, my particular example came from my dad. He was a mechanic, who used mostly Snap-On tools. He bought his No 300 new in the mid to late 60s. I remember cutting a lot of things with it as a kid, some I shouldn't :-)
Dad is a model No 300-01. Shown with a 9 in Starrett blade installed.
Notice I'm using the whole blade.
The square MF logo first appeared in 1964 during the Ingersoll Rand years 1962-82.
There are no longer a patent No showing.
The adjustable frame
If you ever went shopping for metal hacksaw blades, you probably discovered at least two sizes of blades, 10 and 12 inch. The older hacksaw frames took even smaller 8 in blades. Good luck finding these, that's why my Union cast iron frame hacksaw still has no blade :-(
Usually the frame is fixed and would only allowed a specific size blades. Enter the adjustable frame.
As explained earlier, there is a tremendous amount of force exerted on the blade, the frame must be stiff enough to accommodate that. This saw frame accommodate two sizes of blades 10 and 12 in.
Frame extended for 12 in blade. White blade is a Lennox
The tension mechanism
US patent 2,546,660 filed in 1947 assigned to G Wilcox on 27 Mar 1951
The secret to be able to exert tremendous tension easily, resides in the use of a compound lever and a very rigid frame.
As I mentioned earlier mine is a model 300-01, it is a later model bought in the mid to late 60s and the only differences I can spot from looking at on line picture is the blade mounting pins assembly.
On some of the early examples, the patent No 2,546,660 is shown on the frame and the blade holding pins are fixed on the frame (as per the patent). There are also at least two pins that I can see, in order to be able to mount the blade vertical in the frame or angled at 45
On my later model No 300-01, the pins holder are removable and can be turned inside their holders to accommodate any orientation of the blade.
Earlier model with fixed pins. Patent No is also showing on frame. 12 in blade installed
This later model, stamped No 300, still with the patent No, is showing the same new pins attachments as mine 300-01
My Dad's 300-01
Today there is a few Hi-tension frame hacksaw , but they are still making the useless wing nut frame, Guess which one you should own? They do not all provides the same tension range, but if they sport a lever mechanism and a rigid frame, they are of the Hi-tension variety.
As recently as 2013 (Irwin) and 2014 (Milwaukee) that Buck Rogers Patent is still referenced for their own Hi-tension frame hacksaw
Using a hacksaw
If you used one, you figured out that blades can be installed in either directions. I prefer to have the teeth facing forward so that it cut on the push stroke. Just like a file, you should not put pressure on the return stroke, or you will dull the teeth quickly, you have been warned!
If you have sufficient tension on the blade, it should not be deflecting in the cut. If you cannot dial it in, turf your current saw and go get a High Tension Frame , you will never look back. It should go without saying that you should only uses good quality blades, there are lots of garbage blades out there! If your frame as trouble tensioning a 12 in blade, can you fit in a 10 in blade? If so it would help.
You should also uses both hands, one on the handle the other up front on the frame
Looking at my pictures, I should really give this saw a good cleaning. I still uses it every time I need metal cut. It went trough a lot of copper pipes during house renovations projects over the years.
Bob, who remember his dad every time he use this Buck Rogers saw.