question for Portaband users

K

kbog

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Apr 11, 2004
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I am running a Dewalt Portaband with Lennox bi-metal blades. The problem is that I seem to dull the blades REALLY fast in CPM 154. Is there a technique I'm missing here? I will get into the steel with some light pressure, the steels cuts well then its almost like it hits a carbide, nothing. No amount of pressure can get the blade to cut further, almost like it's hung up on the metal. Too much pressure/heat? The blade is not particularly hot after this, just dull. I'm almost wondering if these are really Lennox blades or if I was scammed on Ebay...Literally, 2 inches in and its dull...

Thoughts?

Thanks,

Keith
 
You didn't mention whether or not the steel was hardened. If not, you may a problem with the number of teeth/inch, blade speed, feed rate, heat build up, etc. A lube can help with the latter.
 
When you are cutting make sure to keep on cutting and do not stop. If you stop... the steel bar work hardens and .....no more cuttin! Some times you can jamb the piece into the blade and it will begin cutting again.....and sometimes not!
 
I presume you know to run the saw VERY slowly. On my HF portaband I use the second click setting... not dead slow, but only fast enough to keep the blade moving under pressure.
 
I find that it really helps to break the new blade in. All saw band manufacturers recommend this. My simple way is to begin with a big round or square of mild steel, feeding lightly, gradually increasing pressure as I near the end of the cut. A piece of 1.5" square is good for this. Yes, it will take a while to get through but the fact that you're gently wearing the initial sharpness off of the teeth rather than feeding hard and actually fracturing the points will make your blades last longer.

BTW, that's on my DeWalt portaband, running at about 80 fpm (slow) with 18 tpi bimetal blades. Lennox or Milwaukee usually.
 
Okay, so it is interesting that the combination of posts above all seem to come together into multiple things I am goofing. Working backwards,
I did not break in the blades so I will do that in the future. I am on the fastest setting, so I will slow it down. I am stopping my cut and that's exactly when the trouble starts. My knife profiles are pretty tight on the steel and so I stopped to ensure I was careful not to busdt through a line accidentally. I couldn't get it going again. If I begin a new cut, it gets going again!

This is terrific. Thanks for the assist.
 
Use at least 14 tpi for cutting typical blade steel thicknesses (you should always have at least four blade tips in the material at any moment). Use the the slowest blade speed at first, and then the second speed later . . . if you are a daring guy. I burn't up several new lenox saw blades quickly before I realized that I was running too fast.

Also, don't try to force the blade into cutting sharp curves. This will burn teeth. It is better to waste some raw material or time by making broader curves (or straight cuts), than to burn up saw blades.

Good luck.

Mike L.

Mike L.
 
Be careful when trying to cut a curve. Although the teeth can continue to cut the back edge of the blade will bind and can can the blade to break or just stress the blade. Cut perpendicular slots and this will result in little pieces coming off as you continue with the profile of the blade.
 
This is really very helpful, thank you. I had a wide piece of steel and crammed 3 knives onto it which forced a pretty tight overlap of the blade shapes. This is why I had to stop the cuts, so I didn't touch the knife shapes. Loosening that up a tad will also help me as I will not need to be quite so precise.

Thanks.
 
If you are into the habit of cramming patterns on a plate- you may resort to a very long process- a jewelers' hand-saw... or a scroll saw with a lot (I mean a LOT) of extra blades. There are several places online to get 3mm bandsaw blades made to your porta-band length- but I honestly don't think you would want to pay the price for such a small length of sawblade. The radius of your cuts is determined by the depth of your blade (tooth to rear-edge).

If you are trying to conserve the metal due to cost- get a few 30-minute sessions under your belt with the jewelers' saw frame. takes patience and time- but it can be done. Go slow, wax often, stop and flex your wrists and arms- and get on it!

PT is spot on- thanks for he link- good info too!
KD
 
Piece of advice... steel is cheap. Don't cramp your style by cramming too much on any piece. Give yourself room to work. Leave a little extra metal on the blanks so you can adjust to unexpected changes.
 
Our shop portaband saw had an adjustable hydraulic cylinder that controlled the rate of drop of the saw and the slower the better seemed to be the winning plan. We just set it up and went on to other work while the saw did its thing
 
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