[michialt]

I have a small problem with making cutting 45 degree cuts in just about anything, but especially in Angle. I am using a metal band saw (swinging), and I cannot get this thing to cut a decent consistent 45 no matter how hard I try.

In the past I had always used the saw to make my cuts, then use the grinder to get a "tight" fit. Building a square anything would take an hour or more just to get ready to weld. Now I am working with larger and longer pieces and the grinder is not practical anymore, and a hand grinder isn't working well at all for me.

Last night I was trying to frame up a rectangle made from 2 pieces of Angle welded into a Z, 1 piece of 1x1 and one piece of 2x2 butted together and welded. I got so frustrated I wanted to take a sledge hammer to my saw. I finally tried the weld/fill/grind method, and yes it works, but it looks like crap no matter how much I grind and fill.

The problem seems to be related to the vice on the saw. Part of it is getting a good clamp down on the angle, and part of it feels like the vice is moving on me. I've made 2 or 3 cuts and re-verified the vice was still at 45, and not found anything wrong. I know there will be some variance from the blade, but last nights work was far too out of square to be just the blade. The Z metal creates a 3" cross section, and when fitted square inside 45 is touching, and outside was between 1/8 to as much as 3/8" gap.

I've read a few welders claiming that they prefer a gap that they need to fill, but this is probably even too much for those guys. I personally prefer as tight of a fit as possible because I prefer to fuse weld as much as I can, and keep the filler to a minimum.

I'm curious, how does everyone else handle this problem? Getting a cold saw is out of my budget right now, I've tried using a Miter Saw with a metal grinder like cutoff wheel and melted a cheap 10" miter saw with it. I am leaning towards building a jig that I can use instead of the vice already on it, but I use a lot of angle for my projects, and I cannot picture how to build a jig that will handle cutting Angle Iron at 45 degrees no mater how I need to orient the metal.

[Otto Nobedder]

Don't trust the protractor on the table/vice. Check it against a try-square. How deep is the bandsaw blade? One inch is my preferred minimum. Makes it more rigid, and easier to check with the try-square. Have the top guide no higher than it has to be for each part of this "stepped" cut.

Or is this a horizontal bandsaw? (fixed material, guillotine blade?) Those have their own set of problems, where the best approach is to measure your actual cut angle vs. the angle you set, and adjust the vice to compensate (if you set 45, and get 47, set for 43 to try for 45).

In either case, the tighter you can set the blade tension, the less deflection you'll get.

Be sure your blade speed matches the material and blade TPI, so you're not fighting undue drag, and on the horizontal saw, be sure the feed rate is not excessive.

Lots to consider, and I don't know enough about your setup to be more specific.

Steve S

[MillwrightRWG]

Now this is something I have experience with . I've been there with my not so top of the line band saw 90 deg cuts work great , but vices on these things are very lacking in angle griping capability I've tried forgetting the screw clamp on the saw and useing my bessey clamps but they don't fit well and get in the way of the saw movement .I am a grain elevator millwright in the summer and work out of a service truck we use a lot of 1/4" angle iron 1" to 3" and cut a lot of 45 deg for flange rings a simple chop saw works well with a good blade . I use a makita with makita wheels and the clamp is decent even when clamping with flange down .also the vice backstop will go to 45 in both directions and I have a makita cold cut and the vice sucked on that one to so I cut it off and use my bessey clamp from the bottom. Hey worst case angle grinder 6" cut off wheel and combo square they work well just be careful I have a bit of a wheel stuck in my neck
Good luck
Rwg

[michialt]

I am using a horizontal band saw, and I'm not even able to read the guide so I am using a protractor to set cut angle. I don't think its blade defection causing me problems. I am pretty sure the problem has to do with clamping the angle into the vice. The vice on this thing is pretty crappy.

I've been using wood blocks to help to get a bite on the angle, but theres a lot of flipping things around to get the cuts right.

I wish I could afford a good cold saw for this, but its not quite there yet.

[MillwrightRWG]

Are you cutting aluminum ?

[TamJeff]

Maybe it's the actual swinging part of the bandsaw that is moving when the saw has a load on it? You may have to compensate by setting the material at more or less than 45 to compensate?

[noddybrian]

OK - this may drag on some - but alot of things affect how well a bandsaw cuts.
I'm assuming you have something like this - or similar

bandsaw.jpg (10.34 KiB) Viewed 3712 times

1st up the blade itself- quality & cut vary - try to find a known brand name ( like Starrett ) now how many TPI are you using - no single blade covers all material thickness - rule of thumb is for the material your cutting have not less than 3 teeth in contact and preferably not more than 5 / 6. make sure the tension is correct ( or as best you can judge if there is no gauge for it on your saw ) if it's the above type of saw without hydraulic downfeed adjustment there will be a balance spring - ensure 90% of the frame weight is taken by this - apply only sufficient down weight to allow the blade to cut - only increase it when cutting very wide pieces where the blade TPI if too high - if you can find the more expensive vary pitch type blade this helps- now inspect the guide roller bearings - they are mounted on eccentric bolts that act like a cam to move them closer together to grip the blade & keep it true - any movement here will allow the blade to wander - also the arm these bearing mount to is adjustable to ensure the blade is perfectly upright between the guides - I have a couple of hacksaw blades spot welded together that slip over the blade & stand up about 4" to allow " sighting " of the blade against a square.

Now check the saw frame itself - this type comes on a pressed tin stand that is so weak it moves around & will allow the bottom part of the saw frame to flex ( you'd not think so as it's a casting - but does) so make a new decent strength stand or take it off & put it on a flat surface - now check the swivel pin for play - ream & fit oversize pin if needed - now the vice - they tend to have one side free to swivel & the other side bolted - works pretty well at 90 degrees but not at 45 - only way I found that seems to work is fabricate a quadrant that bolts to the side of the lower saw frame that allows the fitment of an extended vice jaw an extra foot or so longer than the original - mark off the angle you want accurately and fix the other end of the extension to the quadrant - before doing up the machine vice clamp your work to this extension with a "G" clamp - then just pinch up the machine vice - too much pressure tends to make the work slip - now with angle sections as you apply clamping pressure it tends to pull ( or rotate ) it a bit unless you add a block to make up the gap to the height of the other leg.

It helps to identify in which plane the cut is out ( ie vertical or horizontal ) as the cause & cure is not the same for both.
If your not cutting huge quantities of steel the " Evolution " multipurpose chop saws are quite effective - cut pretty accurately & are not unduly expensive.
If you can find a deal on one maybe look for a swivel bandsaw similar to this

swivel bandsaw.jpg (6.46 KiB) Viewed 3712 times

This sort has a fixed machine vice that clamps well and always holds the work at 90 degrees and the saw head swivels to cut the angles- they seem far better & are not hugely expensive.

Hope some of this helps & good luck on the project.

[BAP]

For those interested I have converted most of my vises to air. Anything that moves can not be accurate and may be dangerous. I make most of my actuators from short stroke truck air brake chambers. Shop has lots of air. Simple gate valve turns air on and off. When something starts to move in any conventional screw type vise it likely does not re tighten but continues to move.
With air set at say 160 lbs it is always continuing to tighten. Down side is no mousetrap known to man is more aggressive. Keep anything with feeling well away. bap

[Oddjob83]

I my a vertical slope travel band saw, so gravity and an adjustable counter weight control the cut pressure. first thing i've noticed is angle iron, is not 90 degrees. and as such will always cut funny. when i do have to do a funny cut on the saw, i always adjust my fence and set it to the blade with a speed square and move the saw back and forth till it is always "just" touching. But either way it is always a crap shoot, so I aim wide so I can always fill the gap.

The only time i can get a perfect 90 degree cut is on aluminum angle with a 1' travel radial chop saw, with a negative rake blade and a squirt bottle of coolant for plate over an 1/8 thick. perfect 90 every time and i just use a vice grip to the fence so the material doesn't move. I asked my boss about getting a blade for steel but he said we'd need a lower RPM saw with more horse power, the one i use for aluminum is a makita intended for wood so its too fast.

Since i've given up on miter cuts on steel angle I just lap my joints now anyways.

[jwmacawful]

I have a small problem with making cutting 45 degree cuts in just about anything, but especially in Angle. I am using a metal band saw (swinging), and I cannot get this thing to cut a decent consistent 45 no matter how hard I try.

In the past I had always used the saw to make my cuts, then use the grinder to get a "tight" fit. Building a square anything would take an hour or more just to get ready to weld. Now I am working with larger and longer pieces and the grinder is not practical anymore, and a hand grinder isn't working well at all for me.

Last night I was trying to frame up a rectangle made from 2 pieces of Angle welded into a Z, 1 piece of 1x1 and one piece of 2x2 butted together and welded. I got so frustrated I wanted to take a sledge hammer to my saw. I finally tried the weld/fill/grind method, and yes it works, but it looks like crap no matter how much I grind and fill.

The problem seems to be related to the vice on the saw. Part of it is getting a good clamp down on the angle, and part of it feels like the vice is moving on me. I've made 2 or 3 cuts and re-verified the vice was still at 45, and not found anything wrong. I know there will be some variance from the blade, but last nights work was far too out of square to be just the blade. The Z metal creates a 3" cross section, and when fitted square inside 45 is touching, and outside was between 1/8 to as much as 3/8" gap.

I've read a few welders claiming that they prefer a gap that they need to fill, but this is probably even too much for those guys. I personally prefer as tight of a fit as possible because I prefer to fuse weld as much as I can, and keep the filler to a minimum.

I'm curious, how does everyone else handle this problem? Getting a cold saw is out of my budget right now, I've tried using a Miter Saw with a metal grinder like cutoff wheel and melted a cheap 10" miter saw with it. I am leaning towards building a jig that I can use instead of the vice already on it, but I use a lot of angle for my projects, and I cannot picture how to build a jig that will handle cutting Angle Iron at 45 degrees no mater how I need to orient the metal.

i do this often making gate frames. here's a couple things i do- when using the horizontal band saw is the blade too close to the end of the material? if so the blade will wander and not make a true cut. leave at least 2 inches of waste so the blade is trapped between solid material. if that's not practical then mark it and use hand grinder with a thin cut-off wheel leaving the mark. after tacking i then check it measuring the two long diagonal sides corner to corner. if you believe the vise on the saw is the cause of the problem maybe you can use a c clamp to tighten it to the saw base as an extra precaution against movement. i hope this helps.

[jwmacawful]

one other thought- if the saw has movable blade guides keep them as tight to the width of your material as possible. maybe 1/2 inch either side.

[jwmacawful]

one other thought- if the saw has movable blade guides keep them as tight to the width of your material as possible. maybe 1/2 inch clearance either side. also if the blade is dull or missing too many teeth it makes an accurate cut even harder.