My brother told me to tighten it until the blade breaks. Then back off a bit...
--Paul
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| A bandsaw modification that is important... http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=42047 |
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| Author: | Tai Fu [ Tue Nov 26, 2013 1:42 pm ] |
| Post subject: | A bandsaw modification that is important... |
I do not know what the engineer was thinking when he designed this bandsaw... The tension knob on the bandsaw is just not right... it's small, and once you install a 1" blade you can't turn it hard enough to exert the proper tension on it (which honestly I have no idea what that should be... it seems to cut no different when under extreme tension or under relatively light tension) because that little knob gives limited leverage. But then I had a lightbulb come on in my head... I have a ball mill (it's basically a rock tumbler that have much larger capacity, I built it myself) that is not being used probably forever, and it has a 6" pulley on it to reduce the 1750rpm on the motor to a mere 300rpm... I checked the diameter of the hole in the center of the pulley, and it's just 1.5mm too large. Well no matter, it doesn't need to be accurate, I just need to be able to turn the tension control on my bandsaw... so I removed the old tiny knob and slipped this one on, and lo and behold it works perfectly! Once the bolts have been tightened around the spindle it does not matter if it was slightly too small, it doesn't need to run true anyways. The pulley is now my new tension knob and the little thing in front of it is the original knob. It's odd that someone would make a 18" bandsaw with such tiny tension knob, most other 18" bandsaws have much larger tension knob! It's definitely a love-hate relationship with this bandsaw. When I first got it the saw does not run very smoothly at all, in fact it caused the machine to shake like crazy when it runs... but somehow after using it for a while I discovered its quirk and was able to tune it to be relatively vibration free. It slices through Jumbo guitar width rosewoods with ease (that's about 10" across) , provided the right blade is used. |
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| Author: | dzsmith [ Tue Nov 26, 2013 7:32 pm ] |
| Post subject: | Re: A bandsaw modification that is important... |
Cool Tai Fu, Have you figured out what the correct blade tension should be? My (Sears) owner's manual says to pluck the blade and tighten until it sounds like a musical note, but it does not say which note. Dan |
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| Author: | Paul Eisen [ Tue Nov 26, 2013 8:19 pm ] |
| Post subject: | Re: A bandsaw modification that is important... |
My brother told me to tighten it until the blade breaks. Then back off a bit... --Paul |
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| Author: | Tai Fu [ Tue Nov 26, 2013 8:38 pm ] |
| Post subject: | Re: A bandsaw modification that is important... |
No I haven't figured out what the correct tension is. The problem with plucking them like a guitar string is there are way too many variables. From blade length to blade width, thickness, etc. I read Timberwolf says to back off tension (with the saw running) until the blade flutters, then increase tension until fluttering stops and then increase by another turn or so. Problem is I won't tension a blade with it running because tracking changes as you change the tension, and I don't want the blade popping off the wheel because the tracking changed significantly. |
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| Author: | Tai Fu [ Tue Nov 26, 2013 8:57 pm ] |
| Post subject: | Re: A bandsaw modification that is important... |
There is no view window or anything, unless I make one... There is also no tension gauge on the saw because the saw lacks a spring, but I have read tension gauge is not very helpful... |
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| Author: | Alex Kleon [ Tue Nov 26, 2013 9:01 pm ] |
| Post subject: | Re: A bandsaw modification that is important... |
Tai Fu wrote: No I haven't figured out what the correct tension is. The problem with plucking them like a guitar string is there are way too many variables. From blade length to blade width, thickness, etc. I read Timberwolf says to back off tension (with the saw running) until the blade flutters, then increase tension until fluttering stops and then increase by another turn or so. Problem is I won't tension a blade with it running because tracking changes as you change the tension, and I don't want the blade popping off the wheel because the tracking changed significantly. You need to figure out what the scale length is first. Alex |
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| Author: | murrmac [ Tue Nov 26, 2013 9:27 pm ] |
| Post subject: | Re: A bandsaw modification that is important... |
Maybe if you tell us what the make/model of the bandsaw is ...then you could get some helpful hints ... My only experience is with a Delta 14" bandsaw ...I have experienced nothing like what you are talking about ... Are you sure that your bandsaw is in fact an 18" model ...ie you can saw an 18" wide workpiece between the throat and the blade ? |
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| Author: | murrmac [ Tue Nov 26, 2013 9:27 pm ] |
| Post subject: | Re: A bandsaw modification that is important... |
duplicate post ... |
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| Author: | James Ringelspaugh [ Tue Nov 26, 2013 9:34 pm ] |
| Post subject: | Re: A bandsaw modification that is important... |
Be careful... the larger knob might make it easy for you to over-tension the saw and bend the frame. Depends on the saw of course, but mods like this can have some unintended consequences so please proceed with caution. |
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| Author: | Tai Fu [ Tue Nov 26, 2013 9:38 pm ] |
| Post subject: | Re: A bandsaw modification that is important... |
The wheel is exactly 18" and I can measure 18" from blade to spine. I'm not sure it's even possible to bend the frame of a welded steel 18" bandsaw, maybe if you put a 3" blade that's .090" thick... Unfortunately I have no idea the model/make of the bandsaw. The place I got it from won't say because a lot of these are made for export, so the company won't even tell you who made them. |
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| Author: | James Ringelspaugh [ Tue Nov 26, 2013 9:41 pm ] |
| Post subject: | Re: A bandsaw modification that is important... |
Filippo Morelli wrote: Do you have a view window to see the tracking? It shouldn't move that much. You should be able to make adjustments while running, at least for fine tuning ... Filippo Sorry friend but this is very bad advice IMO... never make tracking or tension adjustments while the saw is running. |
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| Author: | James Ringelspaugh [ Tue Nov 26, 2013 10:46 pm ] |
| Post subject: | Re: A bandsaw modification that is important... |
Because you can take an extra 2 minutes and make tracking and tension adjustments with the saw unplugged. If something goes wrong, you can correct it before your saw is destroyed or you lose a hand. It is almost always a very bad idea to trade safety for convenience. Sorry to be blunt, but in my shop this stuff is non-negotiable... |
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| Author: | Tai Fu [ Tue Nov 26, 2013 11:00 pm ] |
| Post subject: | Re: A bandsaw modification that is important... |
It can be scary for sure... one time I adjusted the tracking with the saw running and the blade popped off even though the adjustment was minor. Turns out it was because the blade popped out of the lower wheel. Only damage is the door got scraped a bit... |
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| Author: | James Ringelspaugh [ Tue Nov 26, 2013 11:24 pm ] |
| Post subject: | Re: A bandsaw modification that is important... |
Filippo Morelli wrote: No worries on the bluntness. I've been doing these minor adjustment for years and have not seen it as any less safe than adjusting the height of my table saw blade while it is running. I never thought that adjusting the wheel for center was any different than the saw running and any number of other things going wrong with it. I was just trying to understand if there was something about that adjustment that was specifically an issue during operation. Filippo A bandsaw is not a table saw, and when tracking goes bad due to over-tensioning or a bad wheel adjustment the band can go off the tires alarmingly fast. And OP is not talking about a little 1/4" blade on a 10" saw... a 1" blade on an 18" saw is a whole different beast. But really, bad practice is bad practice... I'd be surprised if you could find a manual for any bandsaw from the last 50 years that didn't say explicitly 'do not tension or track a blade when the saw is running'. I hate to be a stick in the mud, but safety trumps all other considerations most times... think about how much better a luthier and guitar player you are with 10 fingers instead of 9. |
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| Author: | nyazzip [ Tue Nov 26, 2013 11:42 pm ] |
| Post subject: | Re: A bandsaw modification that is important... |
the instant a bandsaw blade is off the wheels it has little inertia/power, unlike a disc blade....i also have done minor adjustments with a (small) bandsaw running...it seems better for the machine and the blade to be in motion as adjustments are made....that way it can creep into/out of position in tiny increments, rather than being shut off, then yanked into power and having to instantly align..... a table saw, i'd turn that off |
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| Author: | ernie [ Wed Nov 27, 2013 8:45 am ] |
| Post subject: | Re: A bandsaw modification that is important... |
+1 safety first, I have had the blades fly off unexpectedly abt 3 times in 18 years.on an 18 in BS. Adjustments need to be made with the Power OFF , and the blade guard is on the BS for a reason. The BS is the only power tool that I/ve gotten 5 stitches and a trip to the emergency room due to an accidental carelessness. One can never be too careful around power tools. |
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| Author: | Tai Fu [ Wed Nov 27, 2013 8:57 am ] |
| Post subject: | Re: A bandsaw modification that is important... |
Someone said a 1" blade snapping is like a rifle going off... I never had this happen but 1/4" blade snapping is enough to scare me. |
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| Author: | A.Hix [ Wed Nov 27, 2013 11:51 am ] |
| Post subject: | Re: A bandsaw modification that is important... |
James Ringelspaugh wrote: Because you can take an extra 2 minutes and make tracking and tension adjustments with the saw unplugged. If something goes wrong, you can correct it before your saw is destroyed or you lose a hand. It is almost always a very bad idea to trade safety for convenience. Sorry to be blunt, but in my shop this stuff is non-negotiable... 100% agreed. Big band saws are a different animal than hobby/light duty saws. You might not think the blade has much inertia after it breaks as it doesn't have that much mass, but you'd be wrong. I have had 1 1/4" blades break and cut 1/2" deep into my SOLID cast iron table that is 1 1/2" thick! That will freak you out believe me. It does sound like a rifle when they break. Safety #1 always, even when feel comfortable, don't be. Resawing can be really, really dangerous. |
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| Author: | Tai Fu [ Wed Nov 27, 2013 12:03 pm ] |
| Post subject: | Re: A bandsaw modification that is important... |
When a 1/4" blade breaks the energy was enough to permanently kink the blade... you know usually because I did a poor job of brazing them together (I have a coil of 1/4" blades that I am trying to use up before I get anything from Lenox). Needless to say the blade is toast because even if I rebraze them correctly the kink would have ensured that the blade will break from the metal fatigue. It shows when the blade snaps, it had enough inertia to whip the blade really hard against the frame, producing the kink. I always install the guard, close both doors, and lower the guide before turning the saw on after a blade change. This is to protect me if the blade were to slip off the wheel... I don't know what kind of tension a Delta 14" clone can exert but seems any welded frame bandsaws can exert considerably more... at least the lack of a spring on my bandsaw means one less thing to break (and not be limited by a weak spring). I am finding that I don't need as much tension to get the job done as I thought... I ran Woodmaster CT on the saw by cranking the stock knob until I can crank no more (without having to use tools) and it does the job, but I find the saw ran smoother when I really cranked the tension up. The biggest reason my saw shakes when running is because sometimes, the blade doesn't track right so it's moving back and forth (not sideways). I fixed it by detensioning the blade and making sure it sat right on the lower wheel (for some reason playing with tracking settings do not fix this, I had a 1/2" blade jump off the wheel when I tried to correct it) By the way as for bandsaw inserts, my bandsaw came with a metal (probably aluminum or steel) insert. I used to think that was a stupid idea because it might dull the blade, but after hearing your story it made sense... Metal would just dent, not break and wedge stuff between the table. I doubt a birch plywood insert would fit in my saw. The lip is too small for wood to provide much support and there's nothing below to hold the insert in place. |
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| Author: | John Arnold [ Wed Nov 27, 2013 1:00 pm ] |
| Post subject: | Re: A bandsaw modification that is important... |
Quote: I've been doing these minor adjustment for years So have I. I generally don't adjust tension, but I do occasionally adjust the tracking while the saw is running. On some saws, the tracking adjustment is so ticklish that I would not recommend it. But that has not been true with my resaw. The tension adjustment outlined by Suffolk can be done by turning the saw off, adjusting, and running it briefly to test for blade flutter. Once you determine the setting, it is not necessary to do it again...as long as you use similar blades. My resaw (Makita 16" X 2") is sturdy enough that the tracking does not change much (if any) when the blade tension is adjusted. I also have had some scary moments when a thin piece of wood was 'sucked' into the opening in the table. The original insert was lauan plywood, but the slot for the blade had been chewed out too wide. One feature I do like is that the insert is attached to the table with two countersunk screws The oval opening in the table on my saw is pretty small, and I make the inserts out of a thick piece of dogwood that is rabbeted on the back side. The first one I made was QS black locust, which proved to be too brittle. It finally split along a grain line. Dogwood is much tougher, and I cut it with the grain skewed so that the slot for the blade won't weaken it as much. |
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| Author: | Tai Fu [ Wed Nov 27, 2013 1:04 pm ] |
| Post subject: | Re: A bandsaw modification that is important... |
Turning the saw on and off to do the Timberwolf tension adjustment would work if you either have a small 10" or 14" saw where the blade winds down quickly, or a larger saw with foot brake. My saw doesn't have a foot brake and the saw literally takes a whole minute before it comes to a complete stop. |
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| Author: | Tai Fu [ Wed Nov 27, 2013 1:09 pm ] |
| Post subject: | Re: A bandsaw modification that is important... |
Is it possible to retrofit an existing bandsaw for a brake? I hate swapping those big heavy machines because it took some real effort to move them in or out of the building. You know it's a safety issue when a 18" saw has enough inertia after it's turned off to cut 2x4's 10 times! |
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| Author: | Tai Fu [ Wed Nov 27, 2013 1:43 pm ] |
| Post subject: | Re: A bandsaw modification that is important... |
What about using bicycle brakes? |
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| Author: | johnwalkerwaldsmith [ Wed Nov 27, 2013 5:08 pm ] |
| Post subject: | Re: A bandsaw modification that is important... |
Tai Fu wrote: What about using bicycle brakes? Hahah! I would like a picture of that! Not to say it wouldnt work |
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| Author: | Shaw [ Wed Nov 27, 2013 5:52 pm ] |
| Post subject: | Re: A bandsaw modification that is important... |
I like those wood inserts Filippo. I'm going to have to make some. My delta has a metal insert with the larger slot. I had a similar thing happen with a small piece getting sucked down into it..Mike |
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