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KiloBravo
02-04-2008, 09:02 PM
Hi,

I was cutting some steel 2" X 5" 3/16" box tube with my HF BandSaw.
http://www.harborfreightusa.com/usa/itemdisplay/displayItem.do?itemid=93762

I had replaced the blade with a Rigid Bi-Metal 10 TPI from Home Depot. It has cut great in the past. All of a sudden it was 2/3 of the way through the tube and just stopped cutting the steel ? I was not using cutting fluid, and the saw was on it's lowest setting 80 rpm. The tube was on it's side so it cut through the 5" side lengthwise. Any clues ? The blade did not catch or break it just seems dull and won't cut any more. Did I screw it up without the fluid ? As far as I know it's just regular steel box tube.

Thanks,
Kevin

pcarpenter
02-04-2008, 09:32 PM
One problem with tubing is that you have suddenly changing needs for different settings on the counterbalance spring or hydraulic damper.

In cutting through the first face, its as though you are cutting solid stock 5 inches wide. As soon as it goes through, you suddenly are just cutting the equivalent of 3/8" stock. At this point it needs more resistance to keep it from falling through the thin material too fast. I've not done it myself, but I have heard of just this sort of situation stripping teeth off. You may want to check for this or for lost set in the teeth.

Since I am a home shop guy, I usually just baybsit mine, applying a little resitance with my hand when the saw wants to drop after its cut through the face, leaving enough down force on the saw normally to deal with the wider face.

10 tpi is pretty coarse, by the way for tubing. I don't remember the specifics, but the rule of thumb is x teeth in the material at all times....again entirely variable with tubing....far fewer are needed when cutting the face than when going through the sides of the tube.

Paul

smiller6912
02-04-2008, 09:53 PM
I think that a 10 pitch saw blade might be to coarse for 3/16 tube. I was taught that you need to keep at least 2-3 teeth on the material. A 10 tpi (.10) blade and 3/16 material (.1875) there is .125 travel of each tooth where it is the only one cutting. This can strip a tooth and may well cause premature dulling. I cut a lot of structural 3/16 tube at work and I always use 14 tpi. (OK, mostly we cut it on the abrasive saw but still...)

Bill Pace
02-04-2008, 10:00 PM
I agree with Pauls prognosis and think it sounds like the change from the long cut to the sides probably got the teeth --- and, that 10tpi wasnt the best choice for that. As he said, if you had been sitting there (babysitting?;)) and eased the transition, would've probably helped.

Try the vari-tooth blades ...say around 10-14 or whatever the mfg offers, the varying spacing between teeth helps cope with the different varieties of metal.

KiloBravo
02-04-2008, 10:09 PM
OK, I doubled checked my spare blade and it is 14 TPI. It says max SFM 7200.
So, should I push against the saw to prevent it from cutting through the sides so fast ? I need to make about 8 cuts and at $10 a blade they get expensive :)

Thanks,
Kevin

TECHSHOP
02-04-2008, 10:16 PM
I think the magic number is "3" teeth in the work.

Another thing that you may have overlooked is that the head is not dropping to complete the cut because it is hanging up on "something" (piece of scrap, guides, rough casting, power cord, etc.)

I may be the only man on Earth to have sawed off the power cord with this type of saw.

Bill Pace
02-04-2008, 10:21 PM
Yeah, 14 will be gooder...just stand there and as the blade drops through to the sides have a little lifting pressure with your fingers to ease it into that faster cut. These cuts are where a hydraulic damper really shines. I dont think cutting fluid would help here.

KiloBravo
02-04-2008, 10:37 PM
I think the magic number is "3" teeth in the work.

Another thing that you may have overlooked is that the head is not dropping to complete the cut because it is hanging up on "something" (piece of scrap, guides, rough casting, power cord, etc.)

I may be the only man on Earth to have sawed off the power cord with this type of saw.

That's OK the reason I have a spare blade is because every time I let my buddy use it he breaks the blade :) Three in a row and still counting.

wierdscience
02-04-2008, 10:51 PM
You have checked to make sure the teeth are heading in the right direction right?

(sorry,don't mean to insult you,but I sell blades and that happens more often than anyone would think,even did it myself once)

Barring that 10tpi is a bit coarse,hydraulic downfeed you can get away with it,spring counterbalance most likely not.

Only other possiblity would be a hard weld seam in the tubing,not too common,but it does happen.

KiloBravo
02-04-2008, 11:40 PM
OK, the teeth are going in the right direction, but I am still an idiot :)

The top arm was hitting the movable vise clamp that holds the work still.
It was just at the right angle that I could not see it when it was down and
it looked fine when I raised it. Duh !

Thanks Guys !

torker
02-05-2008, 08:25 AM
LOL! It can happen to anyone! Darin...good one about the tooth direction. I ummm.. had that happen. The first 10 or so blades I bought for my saw all came the rightsideoutness for mounting right onto the saw. The same company now sends the blades all backwards/inside out. Got caught the first time:D

GKman
02-05-2008, 08:35 AM
If the blade is too coarse for the work (or a section of the work) add a scrap to the cut to regulate the feed.

KiloBravo
02-05-2008, 09:51 AM
If the blade is too coarse for the work (or a section of the work) add a scrap to the cut to regulate the feed.

GKman, good tip. I will have to try that one !

deltaenterprizes
02-05-2008, 10:00 AM
I have done that before also!!!!!!!!!!!!!!!!!!!!!!!

lynnl
02-05-2008, 12:22 PM
If you can rig up a good clamp on the work so it's tilted at an angle you can present an effectively thicker wall to the blade. That can make the difference in a marginal situation.