Power Hacksaw Doesn't Cut Square.

Whyemier

Whyemier

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Picked up an old 'Jet' Power hack saw two years or so ago. Never did cut square. I could live with .063" or less of travel but I get .125" or more depending on the material diameter. As and example I cut a 1 5/16" dia. Hex bar and the cut was about 3/32" out of square.

What causes this, a worn mechanism? Material holding surface out of square with the blade? A twist in the blade frame? Perhaps I'm expecting too much from this old machine.
 
I have never seen a power hack saw cut square in my entire life! It didn't matter what you tried to correct it, it would still cut out of square.

That what's your lathe or mill is for, to square up the ends. Band saws and chop saws seem to cut more square than any other power tool IMO.
 
Yes, I had thought that could be the the case. I remember the one at the shipyard in Jax. cutting cattywampus all the time. At least the drop they would give me to machine was not square.
 
That and maybe the speed of the cut feed. The one at the skool cuts pretty good, I just take my time with it cutting and have a nice, sharp blade on it. To start it to cut is like dropping a guillotine :eek:
 
Like 4gsr said, never seen one cut perfectly square. I've never seen a horizontal bandsaw that cuts truly square either for that matter. I've seen some that get close, but none are perfect. There are too many variables that can affect how the blade passes through the stock. Additionally they were never meant to cut perfectly square. They rough cut the stock so that it can be trued up on a machine better suited to the purpose, like a lathe or mill.

Now if you've got one that is going really wild, then you need to start looking at a number of things.
Blade - are you using a power hacksaw blade or a hand hacksaw blade? Hand hacksaw blades generally will not take the vertical load of a power hacksaw very well. They tend to twist in an attempt to flip over. Once a blade has been twisted, you can never get them to go back it seems. How sharp is the blade? Dull blades seem to make the crooked cutting problem worse.
Blade frame - the frame usually slides back and forth on a set of ways of some sort. Some saws used a simple piece of straight bar stock, while others used dovetail ways or anything in between. In most cases there are gibs that help the frame to run straight on its mating or guiding surfaces. Make sure those gibs are in proper adjustment if they are present and that they are not worn out. They also need plenty of oil.
Main Frame - Sometimes the pivots on the main frame are worn, allowing the saw frame to come down at a crooked angle.
Crankshaft - Crankshafts that use bronze bearings will run crooked if there is significant wear, causing the saw frame to run cooked as it is pushed back and forth.
Vise - make certain that the vise itself sits square with the blade and its travel.

Look for parts that do not sit square with the rest of the saw. You never know what may have gotten bent on a saw in its past history. Use a known good square too. Estimating what is square never works very well.

One thing that can give you a clue where to look is to determine in which plane the saw is cutting crooked, or if it is a combination of planes.
 
terrywerm said:
Like 4gsr said, never seen one cut perfectly square. I've never seen a horizontal bandsaw that cuts truly square either for that matter. I've seen some that get close, but none are perfect. There are too many variables that can affect how the blade passes through the stock. Additionally they were never meant to cut perfectly square. They rough cut the stock so that it can be trued up on a machine better suited to the purpose, like a lathe or mill.

Now if you've got one that is going really wild, then you need to start looking at a number of things.
Blade - are you using a power hacksaw blade or a hand hacksaw blade? Hand hacksaw blades generally will not take the vertical load of a power hacksaw very well. They tend to twist in an attempt to flip over. Once a blade has been twisted, you can never get them to go back it seems. How sharp is the blade? Dull blades seem to make the crooked cutting problem worse.
Blade frame - the frame usually slides back and forth on a set of ways of some sort. Some saws used a simple piece of straight bar stock, while others used dovetail ways or anything in between. In most cases there are gibs that help the frame to run straight on its mating or guiding surfaces. Make sure those gibs are in proper adjustment if they are present and that they are not worn out. They also need plenty of oil.
Main Frame - Sometimes the pivots on the main frame are worn, allowing the saw frame to come down at a crooked angle.
Crankshaft - Crankshafts that use bronze bearings will run crooked if there is significant wear, causing the saw frame to run cooked as it is pushed back and forth.
Vise - make certain that the vise itself sits square with the blade and its travel.

Look for parts that do not sit square with the rest of the saw. You never know what may have gotten bent on a saw in its past history. Use a known good square too. Estimating what is square never works very well.

One thing that can give you a clue where to look is to determine in which plane the saw is cutting crooked, or if it is a combination of planes.
Click to expand...

I use the power hack saw blades and this one has not seen a lot of use and 'feels' sharp.
I never thought of checking the gibs on the dove tail ways, that's a good suggestion.
Doesn't seem to have much wear or at least not noticeable wear on the crankshaft but then I haven't been looking for that either.
I'll look at the pivots on the main frame if I can determine the points where they are.
The plane is vertical, top is on the mark bottom slews off.

I guess I can live with the cattywampus cuts just don't want to lose anymore material than I need too. Never know when you might need a 1" piece and you end up with a 3/4" cause of an out of square cut. Just need to be more aware.

I thank all of you for the suggestions.
 
Ah - knowing which plane the problem exists in is key. Based on your description the problem is probably not with the saw frame pivots, vise jaws or the crankshaft bearings. They usually cause problems where it cuts crooked from front to back and shows up usually on old saws that have seen a lot of use. Check your gibs and beyond that most of the problem is most likely with the blade itself or the way it is mounted. It may have a very slight tilt to one side that is difficult to detect.
 
Like the guys said lots of variables with a power hacksaw, some of the power hacksaws cut on the push and not the pull, last summer I got an old miller kanuth saw it cuts on the reverse stroke , the guy I got it from had the blade on for pull and wondered why he couldn't get it to cut right , they will eventually cut but it takes a lot longer. All that said there's still something about using them that just seems right like a shaper or a plainer mill , the stroke back and forth . Of course some only want perfection from there machines others just want them to do there job.
 
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