Monday, January 12, 2009

Craftsman Bandsaw Tensioning with Flutter

I subscribe to Wood Magazine's email newsletter. The most recent one talked about using bandsaw blade "flutter" to properly set tension. (Article) While I love my Craftsman 10" bandsaw to death, one irritant is the lack of a gauge for blade tension.

So here's my walkthrough of using the flutter technique to adjust my blade tension.

  1. Clean
    This isn't a joke. Every bandsaw that actually gets used is going to have dust built up in some strange places. Start off as clean as possible. I used my shop vac and a brush.
  2. Loosen Bearings
    I opened up the blade bearings as much as possible. With the top set I was actually able to slide the while head back off the blade!
  3. Remove the Insert
    Push the insert up out of the table from underneath. It will get in the way at best, and chewed up by the floppy blade at worst.
  4. Remove the Miter Gauge and Fence
    Get them off the table.
  5. Button Up
    Close the doors and ensure everything is in place. Visually inspect that nothing is loose or could get in the way of a spinning and floppy blade.
  6. Test Run
    Fire it up for a minute to make sure everything is working correctly.
  7. Last Inspection
    Shut it off and do a final visual inspection.
  8. Loosen Blade Tension
    This is where the article linked above comes in. As stated in the article: "With the saw running, slowly release the tension—about 1/2 turn of the tensioning wheel at a time—until the blade starts to flutter, as shown below." Obviously I don't have the pics they do. But the brighter photo I have is the fluttering blade. The thinner one is the properly tensioned blade.
  9. Adjust Blade Tension
    Again, to the article: "Gradually increase tension until the fluttering just stops, then turn the tensionwheel another 1/4 - 1/2 turn tighter." WARNING: That article was written for 14" and larger bandsaws. Our little 10" saws cannot handle tension like those can. Do *not* go more than 1/4 turn. I actually did somewhat less than that on mine. And that's with my higher quality Lenox 3/8" blade.
  10. Reset Bearings
    If everything went well in step 9, you should now reset your bearings. Side bearings: a folded dollar bill's thickness from the blade. Rear bearing: As close as you can get, or the same thickness from the rear of the blade if your adjustment allows (only my bottom bearing can do that).
  11. Test Cuts
    Now is the moment of truth. Make some test cuts! Adjust the saw as you would if you were making the most important cut in the world and cut some wood. Myself, I tested on varying thicknesses of scrap pine and maple, then resawed some 3 1/2" mahogany.
I don't know that the blade is cutting any smoother than with my previous pinkie pressure adjustment. But this "flutter" adjustment seems more reliable and repeatable. After all, your pinkie is going to get stronger the more you use it like this! So your adjustments will get tighter as your finger gets stronger (or looser if you're aging like me).

A couple of notes here.
  • If your bandsaw is vibrating, either your wheels are out of balance (unlikely) or your blade has been tensioned too long without running. This puts some "memory" in the blade so it is like a bump every rotation. Replace the blade and release the tension on the blade when not in use. A good way to do this is by counting the number of turns you loosen the knob, then do the same number of turns to re-tension it.
  • Always, always, ALWAYS work on your saw with it powered off AND unplugged. There are sharp spinny things that would love to grab a finger or sleeve.
  • Don't expect miracles. With proper care and a sharp blade you can get good cuts from this saw. But it's only a 1/3hp motor. It can only do so much.

Wednesday, January 7, 2009

Segmented Turning Stave Thickness Calculator

I spend some time (a lot of time) (too much time) on the Woodnet forums. But I've learned so much from the guys there.

One guy, Joe Fisher, is a regular. A few months ago I bought a hook hollowing tool from him (videos here). I haven't written it up yet because I've only used it a few times and don't have my technique down yet.

Apparently he's also better at JavaScript than I am. He has recently published a calculator to figure out how thick staves need to be at glue-up time to get a desired thickness after turning. It calculates this based on the number of staves you plan to use, and how thick the final turning will be. It even includes a bit of fudge factor because most of us can't turn to super tight tolerances.

I have yet to do a staved turning (and the couple of segmented turnings I've done were laughable) but I've added this site to the ole toolbox.


The BEST pgrade to my Craftsman 10" band saw!

Sorry, no pics. I've been getting lazy with my camera.

Back in January of 08 I posted about buying a Craftsman Band Saw and even then I mentioned the cut quality was kinda crap.

Then a few days later, after much research online and some trial and error I talked about how to tune the thing. Again, I got the cut quality better, but still not perfect.

I used that band saw a lot. For resawing, pen turning, and so on. It's been a workhorse! And the 1/3hp motor hasn't been any kind of limitation either. But the cut quality still left a lot to be desired.

Last October I realized the blade that came with the band saw was pretty tired.

Pooped out.


So I ordered a new one. The one I bought was a 3/8" "flexback" blade from Cyber Woodworking Depot. Total cost including shipping was under $20.

Product number: 80467-FLB5-1790
Manufacturer: Lenox
Description: (70-1/2 in.) 5 ft. 10-1/2 in. x 3/8 in. x .025 x 3TPI, Hook, Wood Cutting, FLEX BACK

This blade is much stiffer and sharper than the stock Craftsman blade ever was. It also (after following my tuning process again) cuts a whole lot nicer! And faster! Resawing 4" cherry while doable, was pretty slow. Even when the blade was still sharp. With this Lenox blade I can't push the wood fast enough to bog it down.

Now, keep in mind that tuning the saw is important to get good results. Just slapping the blade on isn't gonna get you the quality of cut possible after dialing in the weels and guide blocks or bearings. But on a tuned saw, the difference between a crap blade and a quality blade are huge.

Give it a shot. It's only $20 (shipped) and you'll be amazed.