hacksaw blade mounting

It's been bugging me for a while guys- why do we mount hacksaw blades with the teeth facing forwards? ie away from the direction of cut.

If you use them "in reverse" ie with teeth cutting on the pull rather than the push stroke then the blade isalways under tension and should cut straighter, in theory anyway. This is how Janpanese pull saws work.

Tried it and it works well for me but maybe I've just been lucky on what I cut- mild steel and aluminium so far.

Is there any long standing reason I've not come accross?

Ian

A lot of folk do it that way, Ian. Apart from anything else, as the blade is under tension the blade can't buckle and get kink or a crack in it, as it very occasionally does when "forward sawing". I do it blade backwards sometimes when trying to cut really straight and close to a line, but I can't get much grunt behind the saw that way, so usually go blade forwards if accuracy isn't much of an issue. It gets through the material quicker

Andy,

I suppose it's a matter of putting the "hack" into hacksaw.

The hacksaw is a rough & ready implement, and cutting on the forward stroke is more "energy efficient".

... Japanese pull-saws are, I agree, excellent for precision woodworking.

... Likewise, the Jeweller's Piercing Saw cuts on the downstroke [i.e. Pull].

If it works for you ... Do it.

MichaelG.

I don't see that pull or push makes any difference to the tension/compression of the hacksaw blade in a normal frame.

For a blade that is not pretensioned, pushing the hacksaw puts the section of blade of the far side of the cut (from the user) into tension and the section closer to the user into compression. Pulling the hacksaw just reverses that situation.

For a pretensioned blade, the pretension is reduced (or perhaps overcome) by the compressive load and increased by the tensile load.

Japanese pull saws AFAIK have the blade attached at only one end which is a whole different situation.

Edited By Sid Herbage on 16/07/2012 23:22:47

Fair comment, Sid

When I said "more energy efficient", I was thinking Ergonomics

... It's much easier to exert downward pressure and push, than downward pressure and pull.

MichaelG.

I always use teeth forward as you can use your weight behind the saw, the pull technique is all muscle power. The most important thing I find with a hacksaw is the frame, I inherited a frame from my grandfather which is an old Eclipse pistol grip type with the frame made of solid flat bar, fitted with an all hard blade this is a pleasure to use, bi metal blades do not seem to cut as true but they certainly have their uses, like cutting conduit in the vice attached to a bender, an all hard blade will last a few strokes, but a bar of steel in a decent solid vice all hard is the way to go for me. As an apprentice I bought an eclipse pistol grip saw with a tubular frame, this is awful, the frame is not rigid enough and the blade seems able to twist too easily, almost no hope of cutting true and square. I have never got on on with the frames with a file type handle but I am sure they have their fans.

Mike

I suppose if the blade is inserted into the frame backwards you can still get the same physical effort into it.

Infact I was tought to use the blade backwards for brass, I keep a frame with the blade fitted backwards just for brass. Give it a try with a nice new blade you will be surprised how well it cuts, more to do with negative rake than tension.

I also use japanese saws most days for work and do like them for finer work but still grab a western style saw for larger stuff. The japanese blades are also far thinner than western blades so would buckle far easier if pushed.

J

Edited By JasonB on 17/07/2012 07:52:13

Blade backwards for coping saws for same reason, particularly through thick material, haven't though about a hack saw.

Excellent point, Mike

I have a rather nice Sandvik frame that I bought nearly 40 years ago. The solid flat top bar makes a big difference. ... It also has pins to hold the blade at 45° in the frame, which can be very useful for awkward cuts.

MichaelG.

I would suggest that a hacksaw blade is still pulled through the work by the front mounting of the frame, although we apply a pushing force to the frame the blade will be held taut by the frame and pulled through the work. Using a hacksaw blade in a pad saw handle is useless with teeth facing forward, but even facing backward the blade has little strength and very little power can be applied to the cut. The importance of the frame being able to maintain tension during the power stroke is critical to blade life, all hard blades shatter and bi metal twist and sawing with a kink in the blade is no fun. If you cannot apply enough power to make the blade cut its life will be short, I find an all hard blade with a bit of lubrication will have a very long life providing you don't break it!

Coping saws and fret saws are definately pulled through the work by the handle end, as the frames are not sustantial enough to resist even the more moderate forces of fretwork and coping saw tasks.

The junior hacksaw frame is not usually substantial enough to resist even the moderate cutting forces used in junior type tasks and there is a real benefit in having teeth facing backwards

Mike

hacksaws are designed to cut on the forward stroke, where the frame is slightly lifted for the return, pull and push dosen't achieve much besides making your arms ache

Nobody mentioned where the swarf goes - over your feet or over the bench.

AFIK the only reason Japanese saws were developed as pull type (and the blade angle) was because the peasants didn't have chairs, benches or vices and so sat on the ground holding the wood with their feet. A near equivalent for us is the draw knife & spoke shave developed in conjunction with the bench they are often used with.

Edited By Bazyle on 17/07/2012 13:08:45

Anyway, when you finally break a blade it is far more elegant to fall fowards on to your vise than stumble backwards and fall in a heap on the floor. But I do keep one of the Eclipse mazak handles to use as a pullsaw with any broken blade bits (There are always some good teeth right at the end that should be used up.)

Bob D

Machine hacksaws generally do cut on the return stroke. I've tried both ways in the past with hand hacksaws and decided that cutting on the push stroke is better for me as I can guide it more accurately to a marked line that way and most of the sawdust goes away from my marks. Colin