Sawing thick metal

[superc]

So I have one of those 4x6 vertical/horizontal band saws from China.  Currently configured with a 12tpi blade.

I find myself trimming down some 1" and 2" thick slabs I am using part of for a mill project.  Cuts of about 1 foot of length.  Shall we say neither the saw nor I are terribly happy?  On the 1" thick slab the saw motor overheated and tripped a circuit breaker several times before getting through the slab.

Tonight or tomorrow I will begin trimming down the 2" thick slab.  I anticipate more annoyance at the task being displayed by band saw.  I intend to remove about 1/2" off one side (again, a 1 foot long cut) and about 3" off the other side. 

I believe most of the problem is the blade's tpi arrangement.  I have looked but the only other blade size I can find is an 8 tpi.  This may be better, but I am not sure it would be all that much better.  I suspect something like 3 tpi may be much better suited for steel that thick.  What I need to know is does anyone know of a better tpi arrangement made in a size for these Chinese band saws, perhaps something with a variable tpi arrangement? 

A second consideration is blade speed.  The pulley is set for the lowest possible speed, 80 RPM.  Pretty much problem free performance when cutting sheet metal or 1/4" inch plate, but I am open to ideas for slowing the blade down a little when dealing with thicker pieces.

I guess if I had another question it would be how do the rest of you handle making precision cuts in the thicker slabs of steel?

I don't see myself as doing cuts in this thickness of steel often enough to justify the purchase one of the bigger band saws.

[Brass_Machine]

Wow. You should not be having those problems.

I cut through stuff like that a lot without any of those issues. The belt is set in the mid position (if I recall correctly) for me. I also use Bimetal bandsaw blades that I buy from the orange box store. That is the biggest key for these machines... You cannot go with a cheap blade (I am sure you know). Took me awhile to figure that one out as HF is closer than HD. The HF blades, they are are junk. Would take me forever just to chew (seems like it was chewing instead of cutting) aluminum.

Make sure your blade is not binding anywhere as well.

Also, make sure you setup your cut so you are cutting the thinnest cross section:



Eric

[greenie]

I guess if I had another question it would be how do the rest of you handle making precision cuts in the thicker slabs of steel?

Ahh, you do realise that the saw you have, was never intended to make any sort of PRECISION CUTS at all, it was only ever designed to actually hack off a bit of oversized stuff, so you can work it down to the size you require.

Better follow what 'Brass Machine' - Eric has shown you, you will have to watch if the blade decides to wander, as it's cutting down on the thin section. If it does wander off the line, the blade is worn and possibly needs replacing, then stop the cut and roll the bit of metal over and start again on the clean side.

[Lew_Merrick_PE]

SuperC,

1) Check the flatness of the "table area" of your saw.  I have yet to see one that was reasonably flat.  A fly-cutter can fix that in fairly short order.  Similarly, check the squareness of the angle block against which your clamp rests.  I bush the pivot for index square and replace the general hardware screw with a shoulder screw.

2) Check the vertical pivot of your saw.  It is almost certainly neither true nor square to your table.  I have yet to see an inexpensive drop-type saw that did not get measurably better at cutting by re-boring the pivot holes (after, of course, flattening the table) and bushing them such that the saw will "drop" consistently and accurately.

3) Change out the "grease" that comes from China in the worm-reducer drive.  Ditto on the "bushings" in your wheel-drives.

4) Check and "adjust" (i.e. disassemble & shim) the alignment of your drive & idle wheels.

5) Check and adjust the bearing guides that twist your blade for the cut.  I find that I have to "re-manufacture" the interface between the (hexagonal) guide bar or "fixed" support and the bearing guide supports about 40% of the time.

6) Buy good blades!  I have been a Starrett blade snob for many years.  The slightly more expensive blades from Grizzly have given me good service as well.

I have consistently sliced disks off a ø4 inch round bar that are .050 (+/-.005) thick using a Chinese drop-saw that I bought for $20 as scrap because it had been dropped and broken in shipping.  I won a significant sum about a decade ago by taking the time to set everything up tight & true and cut a piece of 4 inch X 6 inch steel bar such that the cut face was flat within .005 inch (FIM) and true to the two index faces within .010 inch (FIM).  Granted, I have to do quite a bit of tune up to make such a cut, but I can and have done so!

[superc]

Thanks.  I guess I should have mentioned I am doing the precision cuts (all of them really) in Vertical mode using the little bolt on table rather than letting gravity handle the cut.  I am not experiencing any wandering of the blade.  A little Dykem, a scratch mark where I wish to cut and a good overhead light.  I just find it really slow going and every now and then the circuit breaker trips around the time the motor gets warm and the blade starts to slow.  Usually somewhere around 6 or 8 inches into the cut.  I let it cool a minute or two, reset and try again and usually get another 4" into the metal before it happens again.  Maybe it is me feeding the metal too fast?

[John Rudd]

I let it cool a minute or two, reset and try again and usually get another 4" into the metal before it happens again.  Maybe it is me feeding the metal too fast?

Try feeding a little slower....
Sounds like the motor is getting hot, the insulation breaking down and causing the breaker to trip, is this a ground fault interrupt type breaker?
How hot is the motor getting ? Is the fan intake clear?

[superc]

Just warm.  Hmm it is the power strip breaker that trips, not the house current breaker.  But that being said, it runs slower and slower, then the breaker trips.  Fan is clear.  Will try something tomorrow.

[Lew_Merrick_PE]

SuperC,

My second though is for you to check the bearings in your idle wheel and the grease in the bushings of your drive wheel system.  Some of the gunk I have cleaned out of the low-cost 4X6 inch bandsaws is truly amazing.  Good grease is a cheap investment.

[stig]

Just warm.  Hmm it is the power strip breaker that trips, not the house current breaker.  But that being said, it runs slower and slower, then the breaker trips.  Fan is clear.  Will try something tomorrow.

it sounds like there is not enough kerf on the blade teeth to allow a clearance to be formed as the cut progresses. This is a common issue with hand saws in wet timber. Years back we would lube the sides of the blade/saw to help it out or add extra kerf with saw sets if it was a hand saw

[Jonny]

So I have one of those 4x6 vertical/horizontal band saws from China.  Currently configured with a 12tpi blade.

I find myself trimming down some 1" and 2" thick slabs I am using part of for a mill project.  Cuts of about 1 foot of length.  I believe most of the problem is the blade's tpi arrangement.

Cant figure all what you saying but essentially your right its the TPI.
General rule of thumb is  minimum 2 or 3 teeth in contact with any width of cut, on the 1" at best you will have 12 teeth rubbing rather than cutting. Need a courser blade and probably some coolant/lubricant.
Blades will wear out far quicker as well.

[lordedmond]

is this one of those that has a right angle drive from the pulley shaft to belt pulley

I had one from a supplier ( green paint ) and it did the same but I was cutting bronze the gear box was hot and I mean hot hot . took the cover plate off the gear box the oil was the colour of brass 

on further inspection the gears had worn away ( note the box was full of oil ) and was jamming up ,it was a worm and wheel drive and very little remained of both


Stuart

[PekkaNF]

I have one 4*6 cheap band saw and I cur routinely 100 mm dia round aluminium and same size cast iron. Biggest pieces of structural steel and key stock I cur regularry is about 20 - 50 thick.

100% agree with Lew Merrick. Few more hard learned pointers
* This size blade hardly ever have low TPI, but that is not a huge problem if you adjust feed and use flood coolant.
* I buy quality blades and tighten them pretty hard. I think most of the people use too slack blade.
* Water emulssion coolant is messy and annoying, but pretty essential when material is thick or swarf has tendency to stick to blade. I ahve used pressurized air to remove swarf from the blade, works too.
* I have build a hydraulic slow decend to controll the drop more closely. Pretty essential on aluminium and thin wall sections.

I change the oil on the screw drive pretty often. it was originally filled with sand, crud and wok oil. Carreer of thsi saw would have been very short unless I cleanned it. Also bearing selas are not very good, and oil seeps out if the arm is left uppright......

My brother bought similar looking saw and gear box side V-belt pulley was assembled wrong way.... Who in right mind would fit the belt in the step pulley arragement and try to make it work. Might be worth of checkking if it looks wonky. Set screw was inside one V and covered with crud...pretty much dropps of after the set screw is removed.

You want to check thet the tooth space is not filled with swarf when blade exitst the billet. You also want to check that blade is pretty clean when it enters into billet.

Motor in my saw is something like 500 to 750 W and it does not heat at all. Even when it is used for hours. In priciple electric motor could get pretty hot if dimenssioning is marginal. Is it possible that the motor is faulty, wiring (startter/switch/capacitor) is faulty or something is binding?

Pekka

[superc]

Regarding flood coolant and these Chinese 4x6 band saws.  <Mine is a ShopForce Model 150-010>  Tried that decades ago when sawing a concrete truck axle (broken) someone had given me.  Very, very bad idea. 

Reason is, the on off switch is not sealed.  On mine (over a decade ago) fluid splashed onto the switch while the axle was being cut and there was a blue flash and until I could come up with a work around, that was that.  The switch box was quite thoroughly cooked. 

Some re-wiring and a different switch arrangement later the saw cam back into use. 

The required (suggested?) gear oil for these things is 140 weight gear oil.  Some use 80-90 weight, but I am dubious about that being heavy enough.  Problem is that stuff is hard to find and a it's total pain to drain that gear box.  I have some, but I try not to do it too often.  Once every 3 - 5 years seems to be about right.

Yes, steel swarf does stick to the blade teeth.  Often after finishing a cut in Vertical mode I leave the blade running for a while.  Totally amazing how much swarf continues to fall out of the saw onto the table. 

I did attempt to make a foot long cut in a 1" steel plate late last night in Horizontal mode.  Bad idea.  First problem is the vise holding the plate is about 3" tall while the plate stood a foot tall.  Can we say, tuning fork? 

Switched it back to Vertical mode and finished the cut.  I am giving consideration to installing one of those quick detachable tables so I don't have to keep fiddling with screws and bolts each time I switch modes, that or simply pick up a second saw and dedicate it to Horizontal mode.

I cut off some 1 1/8" cubes (approx) which I will mill down to home made inch blocks. 

I then decided to do the same thing to some 2" thick stock and started cutting off a 4.5" strip.  Half way through there was a soft 'Bam' and the blade stopped but the motor kept going.

Investigation showed the fan belt had parted.  Sigh.  I got about 24 years of use out of that belt so I guess I shouldn't complain too much.  I'll go buy a new one later on this week.

Now of course what I am wondering is if the belt had begun stretching this year, which would be a possible contributor to the problems I was experiencing as that would reduce the power available to the blade pulley.  I am hoping that after a new fan (pulley?) belt is installed maybe the problems will go away?

[75Plus]

In regards to 140 oil, I have a gallon can of MFA 140 weight transmission oil, that's how the can is marked, that I would like to find a home for. It came with the house when I bought it back in Aug. 1985. Since I haven't found a use for it in almost 29 years I feel confident that I can safely dispose of it. It is yours just for the shipping cost. PM me if you are interested.

Joe

[Lew_Merrick_PE]

Investigation showed the fan belt had parted.  Sigh.  I got about 24 years of use out of that belt so I guess I shouldn't complain too much.  I'll go buy a new one later on this week.

I find that the resin impregnated leather individual link v-belts (I forget the brandname under which they first hit the market -- they are usually red, green, or blue) works best for this type of small pulley/short length application.

[Jonny]

Mines branded as a quick release vice Sealey made in 97 bought 98.
Was out of action for about 11 years but got it going again two years ago, them bearings.

Used to cut 4", 4 1/2" and 5" round, 5 1/2" wouldn't clear the frame. Took ages to cut so buy in cut to length the last 14 years.
With bimetal blades (vari pitch) used to take 20 mins to cut 4" round, 4 1/2" at least 35 mins and it got warm.
Nowadays used for cutting 2x1" takes its time but better than using hack saw or cut off milling.
Ive put the spring on max setting that's it and use coolant by bottle.

Gone are the days when you could buy 3 carbon blades and get one free for £11. If your machines working right you wont be disappointed with the Bimetal blades, they last at least 4 times longer and cut better.

Two standard V belts on mine, no oil in the gear just the original grease.

[PekkaNF]

Regarding flood coolant and these Chinese 4x6 band saws.  <Mine is a ShopForce Model 150-010>  Tried that decades ago when sawing a concrete truck axle (broken) someone had given me.  Very, very bad idea. 

Reason is, the on off switch is not sealed.  On mine (over a decade ago) fluid splashed onto the switch while the axle was being cut and there was a blue flash and until I could come up with a work around, that was that.  The switch box was quite thoroughly cooked. 

There are some variations on this theme.....Mine had a NVR switch on the tray. Big idea was that dropping arm has a flag that activates the switch at the end of travel. Mine had no additional limitswitches. The mount and tray is a joke. I boltted them together and tried as intended a little while. The switch failed and I got replacemet. I made a new stand for the saw and new tray as well.

As you say these parts are not sealed, not even against dust and swarf. One person here got a small fire after letting aluminium, iron and other metallic swarf/dust collect on the saw...loud bang and fire. "Aluminium" probably had some magnesium, or something else exotic happened.

Anyway, whatever cooling/lubrication needs a little attention. And there is electricity on cheap format pretty available. And someone could slip on the coolant, when it runs downstream on the channel under a cut. But I think that the board rules are: use your brain.

I have used some outboard engine gear grease and normal thick gear oil. Haven't seen much difference. I think that there is a funky smelling (hypoid?) oil, that should be avoided if any of the gears is made out of copper metal? Although I was tempted to use that, because I have a helical gear in it, but once I had trouble with it, this EP additive was slightly unhealty on one bronze gear, it turned all black and I was told to avoid hypoid with copper. But that was a long ago. Maybe new oils are different?

Pekka

[mattinker]

This explosive situation is due to mixing Aluminium powder and iron powder to create thermite (used to fill incendiary bombs and weld railway tracks). See link below.

http://ncsp.tamu.edu/reports/DOE2/doe2_0017.htm

Regards, Matthew.

[PekkaNF]

This explosive situation is due to mixing Aluminium powder and iron powder to create thermite (used to fill incendiary bombs and weld railwat tracks). See link below.

http://ncsp.tamu.edu/reports/DOE2/doe2_0017.htm

Regards, Matthew.

"A safety coordinator at the Esso Oil Company plant in Longford, Australia, was using a belt grinder in his home workshop ...."

Now - that is a combination!

Luckily he escaped it alive. The incident I knew was a bit less dramatic. I think that dangers of machining aluminium and other light metals (and specially mixing them with iron metals) are pretty widely taught on the schools, least here. But on home workshop lucily there is less time pressures and therefore easier to keep machines clean.

Pekka

[greenie]

Boy has this lot gone of on a weird tangent, so, might as well add to it, eh. 


Grinding some magnesium alloy plate on a belt grinder and got similar results, sparks followed by a whoosh as the build up of iron particles came alive/disintegrated.

Boss reckoned that was a classic, so, as I milled this mag alloy, he collected the chips, put them into small plastic bags and kept these little bags handy.

He was out the front of the workshop using the gas axe when this 'customer' ( sucker ) walked up to talk to him, he dropped one of these 'little bags of magic' on the ground near the sucker and waved the flame from the gas axe over it, boy oh boy, the reaction from the 'sucker' was a site to see. He went upwards about a foot and his feet were moving before he even hit the ground and he was gone like the wind. 

Moral is, ------ be bloody careful of magnesium alloy.

Oh, Longford has another real claim to fame, this one aint just scuttle butt either ------------.

http://en.wikipedia.org/wiki/Esso_Longford_gas_explosion

[superc]

Yes fine enough aluminum powder is potentially explosive and flammable.  So too is powdered magnesium, lithium or titanium.  Stuff you really, really don't want collecting on the floor of your home workshop as piles of dusty swarf. 

Back in the days when I hung out in shops with big machines and greasy vehicle parts, that place had special fire extinguishers both inside and out just for such fires.  Here in America we call such fires Class D fires.  Thankfully they are rare events.  You need special fire extinguishers based on graphite, or sodium chloride (aka salt and won't your shop just love being soaked with salt), or copper powder (dangerous to inhale) just to have a chance of controlling the blaze. 

Well I found another drawback of the Chinese 4x6 saws.  Non standard (in America anyway) pulley belt size.  Original belt is marked "Rong Zhieng A22 559"  It is not a 1/2 inch belt.  More like a 3/8" belt.  About 23.5" in length.  Sigh.  Picked up a 23"x0.5" belt anyway and a 24" too.  No store I know of around here carries funky metric size belts.  The 24" is worthless, too big.  I'll bring it back for a refund.  The 23" size runs, but the saw is too fast. 

Available options, hang a 30 pound weight off the back of the electric motor and hope the belt stretches, build a brand new pulley housing and motor mount, one designed to use belts made for the US consumer, shop on Ebay for a belt that fits perfectly, add a rheostat to the power line to reduce motor current so the motor runs slower, ignore the blade going way too fast (the blade actually screeches when cutting steel with the 23 inch belt, but it does cut), a combination of all of the above.

[superc]

 

I measured the speed of my saw blade with a 1/2 inch belt.  Yeah that's a little faster than the desired 80 SFM



Can we say 1,100 SFM?   

No wonder the blade screeched when I fed it steel.

Further investigation showed the problem was although the 1/2" belt fit over the pulley edges, it was almost an inch away from where it should be sitting on the pulley centers.  I now did what I should have done in the beginning of the belt issue.  I took measurements.  Center to center of the pulleys at their closest is 7.75".  Outwards closer to 8.5" added the pulley shaft diameter and came out of it with about a 22" belt being needed.  Hmm the original belt remnants have A22 559 marked on them.  Could that be the same as 559mm or 22" and never mind the fact the belt itself measures 23.5"?  Figure some stretching (which also explains why the saw wasn't cutting before the belt finally began disassembling itself).  The belt width is 10mm or 3/8"  The belt depth is .31" or 8mm. 

More research online.  I found it.  The belt size for Asian 4x6 band saws is called SPZ.  10mm wide, 8mm deep.  SPZ 559 or 560 should work just fine.

[MetalMuncher]

Hey SuperC, I got an Enco sale flyer in an order today, and they have Starrett band saw blades on sale. Their blades for our saws go all the way down to 6TPI. ($9.99). Thought you might like to know.

[mattinker]

add a rheostat to the power line to reduce motor current so the motor runs slower,

You need to look into induction AC electric motors, the ones that don't have brushes, the speed depends on the number of cycles , in your case, 60cycles (Hertz) not voltage.

Regards, Matthew

[JohnHaine]

Just for the record, thermite is a mixture of aluminium powder and iron oxide, not iron powder.  When it ignites the Ali burns on the oxygen from the iron oxide and the oxide is reduced to very hot pure iron.