resawing speed gain if upgrading

[Martin Rock]

Hi all

I have lots of 6" to 10" inch wide planks of ash to resaw (from 2" to 1" thick). I have about a total of 450 feet of resawing to do. On my current tawaineese bandsaw 1.5HP with a blade speed of 3500 sfpm, it will take a long long time.

I could get a real good deal on a general 390 (the 20" floor model) bandsaw with a 3hp motor and a blade speed of 4500 fpm.
I am wondering. How much faster I could resaw with the general bandsaw.

I am also wondering If I would gain in the quality of the cut As I cut my own veneer.


thanks Martin

[Jamie Buxton]

A bigger stronger bandsaw will help. But a bigger speed difference may come from the blade you choose. For cutting 10" tall boards, get a low teeth-per-inch blade -- less than 2 tpi. And carbide blades cut cleaner longer. For this kind of thing, I like the Lennox Woodmaster CT.

[Phil Thien]

Some months ago I tried a bimetal blade on my Skil 10" 1/2-HP saw. This saw is tiny compared to your saw. But it is a nice little saw. It can handle up to 7" resaw.

I had previously been using Blade Runner/WoodSlicer blades for resawing. And they worked (and still work) great. But cutting any sort of very hard exotic was hard on the blades, and dulled them quickly.

So I got this MK Morse 1/2" 3-TPI bimetal blade, .025 stock. Installed it on the saw, and it cut slower than I had hoped.

I noticed the kerf was substantially wider than the .025" blade stock would seem to require.

After thinking a while, this was my solution:

Phil Thien's bimetal blade turbocharging technique:

(1) Get a bimetal blade, 1/2" 3-TPI.

(2) Use a steel vise to squeeze the set out of the teeth. Don't worry, they will spring back a bit. I used a drill press vise the first time I did this.

(3) Install the blade on your saw, and then use a round diamond bit in a rotary tool (Dremel-type) to sharpen the teeth. You only have to hold the diamond against the blade for approx. one second on each tooth.

Now go ahead and give it a try, you might be surprised.

Last time I cut some 6" Paduak (which is a pretty hard wood), my blade sliced through it like a hot knife through butter. Minimal feed force was required, and I got a very nice finish. It cut faster and easier than a Blade Runner/WoodSlicer, which is saying quite a bit.

I suggest trying this with an older, USED-UP blade. Don't do it with a new blade and then send me the bill if you don't like the results. I like the results, but YMMV.

[Mike Harrison]

Just put a bigger motor on what you have. I installed a 3 horse motor and a riser on my HF saw a few years ago and it made a big difference. The blade selection mentioned is a very big part of the process. I use a 3 tpi hook or skip tooth blade and d a lot of resawing to make panels.

[Jim Matthews]

I beg to differ, on two of the suggestions above;

The sharper the blade, the cleaner the finish of the cut surfaces. There's more shearing.

More set means less drag against the back of the blade, as the kerf clears a channel wider than the blade.

That said, you may need to keep small shims on hand to keep the offcut clear of the stock. This is one of the rare things an assistant can do better than the operator.

To reiterate an important notion - the gullets are vital to remove sawdust from the cut, if they're filled with sawdust the blade will heat up and the process will slow to a crawl.

[Peter Quinn]

I switched from a PM 14" with a 1 1/2HP motor to an italian MEBER 20" with a 3HP, and it does go quite a bit faster on resaw. With the same blades (timberwolf, 1/2" 3TPI) its gone from a matter of "How slow must I go" almost to "How fast can I push". There is a point where feed speed leads to much lower cut quality, but I have yet to find a feed speed in my comfort range that will bog the machine down much with a sharp blade. The bigger table is handy too. My new saw can certainly tension a much wider blade, and one day I will get one, but the 1/2" blades get the job done for my needs presently, and they are cheaper. I don't think I'd be suggesting a basic steel blade for the volume of resaw you are indicating, and in my research most of the better carbide tipped blades don't really want to spin on wheels much less than 18", and the 14" saws don't really have the power to push a blade with that thick of a kerf anyway. Somewhere in that run on sentence there is an argument or two for getting a bigger saw. I don't imagine you would ever have to remove the set from your blades with a full sized 3HP saw though I can see how that might improve a small under powered saws ability to push through dense material.

[Chris Fournier]

For the quantity and sizes that you have indicated I'd rather pull my own teeth out than resaw all that lumber. I would look for someone with a portable mill to do this work for you. Of course we all pick our own battles!

[Bill ThompsonNM]

I think you would get better cut quality faster with the bigger saw. If you can swing it and it's a good deal never let it be said that this forum discouraged anyone from upgrading equipment!

[Phil Thien]

I beg to differ, on two of the suggestions above;

The sharper the blade, the cleaner the finish of the cut surfaces. There's more shearing.

More set means less drag against the back of the blade, as the kerf clears a channel wider than the blade.

That said, you may need to keep small shims on hand to keep the offcut clear of the stock. This is one of the rare things an assistant can do better than the operator.

To reiterate an important notion - the gullets are vital to remove sawdust from the cut, if they're filled with sawdust the blade will heat up and the process will slow to a crawl.

I'm not sure if this was to my post, but seeing as I was the only one (I think) to mention sharpness and kerf, I'll respond.

Obviously we want blades to be sharp. The sharper, the better. I've found my sharpened blades cut better than brand new blades. I think Duginske even mentioned in one of his books that sharpened blades often cut better than new.

Second, Kerf: As long as the kerf is wide enough for the blade body to pass easily through the cut, your kerf is wide enough. Any wider than that, and your kerf is arguably too wide. You are simply requiring your motor work harder to remove more material with no payoff.

A wider kerf is critical when cutting curves, for resawing it can get in the way.

Finally, gullets. I can't argue with the fact that a wider kerf increases the sawdust carrying capacity of gullets. But this is unnecessary.

If you calculate the volume of the gullet, and use that to compute (using the FPM of the blade, the # of TPI, and the time it takes to cut a board) the volume of sawdust capable of being removed, you'll see that the gullets are capable of carrying many times the dust necessary during resawing.

You may find resawing a 6" wide board that is 4' long produces 2-3 cups of sawdust, but the gullets passing through the board during the process may have had a volume of many times that.

This is why guys with those huge old cast iron saws often just leave a 1/4" or 3/8" blade in place and still find they can resaw very wide boards very quickly. The smaller gullets of their 6-TPI blades does not interfere with resawing in the least.

[george wilson]

Sharpening your blades will make them sharper than new,IF you do it right. I think that blades are heat treated after the teeth are formed,which takes their sharp edges off. This I observe from the fact that new blades have the same color even on the front edges of their teeth.

Back in the 50's and 60's,Sears sold a nice little set of 1/4" dia. rotary files that were all bright. They were so sharp they'd cut my fingerprints. Then,they started selling the same set in a nearly black color. They were duller than my old,used bright files,which I regarded as too dull. I complained to them. They answered that they were nitriding the new files,and they would stay sharp longer. NONSENSE!!! The blasted things burned wood even when new. I think it was a cheap short cut that someone resorted to using. Heat treating AFTER their teeth were ground was the surest way to burn the keen edges right off.

[ian maybury]

I'm no expert, and just getting into band saws - but think that while all these variables matter their exact effect on cutting speed has to be a bit of an it 'all depends' sort of an issue. i.e. that it's probably not going to be the case that exactly the same formula works across all saws. To gain an improvement in a given sitution you've really got to scratch the right itch.

A major source of compromise must be the way that the same basic blade stock/tooth configurations are used across saws that vary very widely in size, applications and speed.

What I seem to be picking up is roughly as follows:

1. Blade speed is fundamental - more speed = more distance cut/tooth/sec
2. Bite taken/tooth or depth of cut and width of cut are fundamental - bigger bite = more cutting speed for a given blade speed, but this with increased width must mean an increased amount of dust/tooth to clear.
3. Thickness to be cut is fundamental - for a given depth and width of cut and speed both the required torque/blade pull and the amount of dust each gullet must carry out of the cut is presumably proportional to this.
4. Type of wood and its cutting characteristics is fundamental - ease of shearing/chopping, friction/adhesion, toughness etc all must matter.
5. Blade choice is also fundamental - but what works best on one wood type at a given speed/feed rate and depth of cut may not be best at others.

Extra blade speed isn't going to be much use if you haven't got the HP (actually torque) to run the blade at that speed, but unless you were experiencing 'bogging' (being forced to reduce the feed force/rate because the motor was losing rpm) more HP probably won't of itself improve the cutting speed. Gearing up to increase the blade speed will be required. It doesn't seem like blade speed should make much difference to dust clearance.

The blade must cut cleanly and properly clear itself - and the latter becomes a much bigger task as the thickness to be cut and the depth of cut increase.

Personal experience and snippets picked up from others writing on the topic suggests that lots of gullet space is important on deep re-sawing, but the issue may be less pronounced on different saws. Skip tooth blades get frequent mention as working well for re-sawing on smaller saws.

Surface finish is no doubt another ball of wax - one containing lots more trade offs against speed. And that's before curve cutting is introduced to the equation.....

ian