Hot Rod Forum banner

1 - 20 of 33 Posts

·
Registered
Joined
·
3,925 Posts
Discussion Starter #1
Question for Willys, qctech, or any other owner of a Harbor Freight metal cutting bandsaw. How do you set the torsion on the spring that controls the feed rate of the blade? The directions just say "not too tight", "not too loose". So how do you know what the correct spring pressure is? Maybe if you just gave me the approximate time it takes you to cut a piece of 2X3 rec. tube (cold rolled, .125 wall) or some similar guideline I can go by. I have no idea if I have this thing running at the right pressure.

Dewey
 

·
Hotrodders.com moderator
Joined
·
9,581 Posts
My Take

Dewey

On this it is a bit of an "experiment" if the cut is clean and square you are fine..just start with slow feed rate and then bring it up a bit..if the tool starts to jam or the blade walks out on you then the feed rate needs to be slowed down a bit..

Watch for heating..if the feed rate is too fast the blade will overheat.. Seeing smoke is a good clue..The blade should be cutting not wearing its way through the metal..

Feed rates will vary somewhat depending on the thickness of the metal..When you have made some cuts then you will get the hang of setting a feed rate..

Sam
 

·
Registered
Joined
·
3,925 Posts
Discussion Starter #3
No smoke, no binding, the blade seem to be running true, and it is not that hot after I finish a cut. So actually I'm a little worried it's "wearing" not "cutting" through the metal. I'm cutting 2x3 rec. tubing, .125 wall, and I'm cutting it diagonally at a 30 degree angle. These cuts are taking an average of about 15 minutes each. Does that sound in the ballpark?
 

·
Hotrodders.com moderator
Joined
·
9,581 Posts
Seems a bit slow

You may wish to try balde that is about 14 teeth per inch..may be the blade you have is a bit too fine..???:) Inspect your balde to see if you have good teeth on it..wearing the metal gives a blade that has no teeth left..I do not think that you have too much concern here..I would not as long as I am getting a good cut..:thumbup:
 

·
or Jeff, or Doc, or...
Joined
·
989 Posts
As long as the blade isn't getting hot, your OK. Hot blades indicate too fast of a feed or worn teeth. Kind of a quick test that I use, is spray the blade with a lubricant. If it smokes , your too fast or dull. 14 TPI sounds right for .125. Should cut it in about 1 minute or less. The top and bottom may take the most time, but when it hits the sidewalls, it should drop right through.

Also, look at where the blade is welded. Make sure that the weld is ground flush or slightly ground in. If not, it will make the blade catch, skip and start bouncing. This will end up ripping teeth off and trashing a good blade. Not sure of the quaality of a H/F blade, but I use Noton Bi-metals on my bandsaw. Lasts forever.
 

·
Registered
Joined
·
3,925 Posts
Discussion Starter #7
Whoa, I'm nowhere near one minute. More like 15 minutes. Also, I now have almost NO tension on the spring that controls the rate of the cutting head. I'd actually have to hang some extra weight on the end of the head to get it to apply more pressure at the blade.

Also, I've been checking my more recent cuts and I AM getting some fairly inaccurate cuts. The blade seems to not be dropping at exactly a 90 degree angle to the base of the machine (the vice/bed which holds the stock). As a result, the bottom of the cuts are all about 1/32 to 1/16" shorter than the top of the cut. Since the head is permanently hinged to the base there doesn't appear to be any sort of adjustment for this. Any thoughts?
 

·
Premium Member
Joined
·
8,453 Posts
You MUST lube the blade continuously during a cut, especially on the fairly big stuff that you are doing. I keep a squirt can of 30W near my saw and keep the blade dripping the whole cut. Your description of slow cut rate and blade drift are classic signs of a dull blade. Change it, then lube it.

I have always used HF blades and get reasonable run time out of them but nothing like Beenaway is getting with the name brand ones. I guess I'll try a Norton next time to see if it lasts better.

Point is, a sharp blade with the proper tooth pitch that is well lubed should make quick, accurate cuts for a long time.

Haven't really paid much attention to spring tension. I guess I keep it pretty light. As stated by others above, a sharp blade with aggressive enough teeth will virtually eat its way thru the steel and seem to suck itself thru the thin walls of a tube.
 

·
Hotrodders.com moderator
Joined
·
9,581 Posts
Ok now I;m determined

Cboy,
Run the head of the saw to the top of its travel and set your machinsts square against the blade..

Scribe a mark on the bed of the saw where the machinsts square lands..then lower the head of the saw till the blade contacts the bed and place the machists square again against the blade..the blade should come down and hit exactly on the mark..Do this with a new blade in the saw..if the saw is not coming down straight then I dunno..

Now do a trial run on a piece of scrap..bring the tension on the blade up to a point where you have very little deflection when you push on the side of the blade with your finger..

Having to hang a bit of weight on the head of the saw may be needed to put some downforce on the blade..

Mkake yourself a drip bottle using a hdwre store valve..(little needle valve) and a piece of copper tubing arranged so that you can drip lube on the blade..

Now after doing all this and it still does not work..well dunno what to say here..???
 

·
Registered
Joined
·
3,925 Posts
Discussion Starter #10
I don't think this is a case of "drift" caused by a dull blade. After some more careful inspection, based on OneMoreTime's suggestion, it is clear the blade does not travel at a 90 degree angle to the bed - even when there is nothing being cut. When I put a square on the bed (where the stock is placed) and lift the saw head, I can see that the blade runs out about 1/8th of an inch from the edge of the square at about 5-6 inches above the bed. When the blade is all the way down at the base it touches the edge of the square. As I lift it I can clearly see it running out further and further from the square.

Willys, could you do me a favor and check your saw the same way...lay one edge of a carpenter's square across the bed and the other edge parallel with the blade. Then lift the head up about 6-8 inches. I'm assuming your blade will run true right along the edge of the carpenters square. Since I don't see any way possible that I can adjust how the head (blade) travels in relation to the base, I've got to think there is something amiss with how this particular unit was machined or put together. Let me know if you think there is some adjustment on your saw that I could try to make on mine.

Dewey
 

·
Premium Member
Joined
·
8,453 Posts
Maybe you got a bad one. Mine has a run-out of about the thickness of the blade @ 5" above the bed. My experience is that I get very acceptable squareness in my cuts until my blade starts getting dull when it starts to travel severely in one direction.
 

·
Super Moderator
Joined
·
6,623 Posts
Feed rate is determined by the shape of the swarf or "cuttings", you should have nice "curly cues" or figure 9 shaped chips. Tooth pitch is the most important factor when selecting a blade for a bandsaw, you should have three teeth in contact at all times or you risk breaking teeth off, too many teeth in contact raises the pressure needed to effect a cut and also means they will plug up with chips causing increased friction and possibly chip "welding" in the gullet of the tooth.

Here's a good article for reference.
 

·
Registered
Joined
·
3,925 Posts
Discussion Starter #14
[email][email protected][/email] said:
Mine has a run-out of about the thickness of the blade @ 5" above the bed.
So at least we know the "run out" in my saw is not common to them all. What you are describing sounds like less than 1/32" in 5" of travel. Mine is more on the order of 1/8" in 4 inches of travel. I just don't think this is a "blade" or "sharpness" issue - particularly when the run out is visible with no workpiece even in the machine.

I just got through emailing H.F. Customer Service to describe the problem. We'll see if they have a solution.

BTW, thanks for the heads up regarding constant lubrication of the blade. Nothing at all in the manual about doing that. I'll have to rig up some sort of drip system.
 

·
Super Moderator
Joined
·
6,623 Posts
You need to set the guide blocks closer to the blade, lightly touching is about right. If yours are rollers the same applies.;)
 

·
Registered
Joined
·
3,925 Posts
Discussion Starter #16
4 Jaw Chuck said:
You need to set the guide blocks closer to the blade, lightly touching is about right. If yours are rollers the same applies.;)
I have rollers and I have moved them closer and closer - from lightly touching the blade, to spinning the wheels as the blade runs, to downright tight against the blade. It does not make a difference.

And I have checked each of these tightness settings by placing a square on the bed of the machine and then lifting the head. In each case the roller setting made no difference...the blade showed a run-out of approx 1/8" in a 4" rise of the blade no matter how tight the rollers are set.

Which, in theory, makes sense to me. Yes, I can understand that roller (guide block) settings would have an effect on "wander" and "run-out" when the saw is cutting something, but when there is nothing in the machine, the head should rise and fall perpendicular to the bed. And since the blade is in a fixed position in the head, it too should rise and fall at exactly a 90 degree angle to the bed. But mine does not.

4Jaw, I think your suggestion DOES apply to a machine which has a true head (lifts perpendicular to the base) but has poorly set rollers (blocks) and is cutting a workpiece. This could allow the head to drop "true" but the blade would be pushed or pulled out of true by the pressure of the workpiece.

However, when there is NO work or workpiece to draw the blade out of true...it would raise and fall at exactly 90 degrees to the bed...assuming the head is a true 90 degrees to the bed.

Does my thinking make sense here or am I having one of my usual brain malfunctions?

Dewey
 

·
Premium Member
Joined
·
8,453 Posts
I set my rollers very tight on the blade and the blade tensioner very tight also. Your problem is a manufacturing defect - they drilled the saw pivot hinge out of square. There isn't anything you can do to fix it.
 

·
Registered
Joined
·
3,925 Posts
Discussion Starter #18
Well now I'm totally confused...and have to take back some of the prior theory I was spouting off to 4Jaw Chuck. I just went out to the shop and put a square on the HEAD itself, rather than the blade, as I lifted it. And the head itself seems to be running true, or at the most only about 1/32" of run-out. So how could the blade, which is fixed in the head, show more run-out than the head itself?????

I can't imagine how I could get those rollers any tighter to the blade (and still have the saw run) but maybe I'll try that and a lot of lubrication on a test run or two.
 

·
or Jeff, or Doc, or...
Joined
·
989 Posts
Cboy-
I'm up for the challenge !

OK, first, I would take a piece of sacraficial plate, and somehow clamp it to the clamping area. Make a scored cut, but not all the way through. Lift the saw. Take a small plumb bob, and drop the bob from the blade. It should be adjacent to the cut line. It should also be consistant across the length of the blade.

WAIT !

Is your cut out of square from top to bottom, or left to right? Is the back fence PERPENDICULAR to the cut line? The "zero" on an adjustable fence is close to worthless until its "tuned". Same goes for ANY chop saw, table saw, radial arm, etc.

Once you've established what is out of square, you can add a piece of 3/8" plate to the surface, whether its the bed, or the fence. That plate can be shimmed to square with the blade. Use countersunk screws and thread the cast table/fence.

Reboring the pivot bore, or machining the pivot will be alot tougher.
 

·
Hotrodders.com moderator
Joined
·
9,581 Posts
Guides

cboy said:
Well now I'm totally confused...and have to take back some of the prior theory I was spouting off to 4Jaw Chuck. I just went out to the shop and put a square on the HEAD itself, rather than the blade, as I lifted it. And the head itself seems to be running true, or at the most only about 1/32" of run-out. So how could the blade, which is fixed in the head, show more run-out than the head itself?????

I can't imagine how I could get those rollers any tighter to the blade (and still have the saw run) but maybe I'll try that and a lot of lubrication on a test run or two.
Those guides could be slightly twisted in the head causing the blade to be a bit off and giving an angled cut..I gotta head out today and am going to stop at harbor frieght store..maybe I can see where the problem may lay..

Now we are all determined to get Cboy on the square here..GRinnnn
 
1 - 20 of 33 Posts
Top