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Re: Vise Jaw Extensions
On Mon, Feb 14, 2022 at 04:19 PM, Rick Sparber wrote:
These straps deflect enough to not hold well:? I see your point now although I seldom have a problem holding small stock. I have the 3/8 plate on the stationary jaw and just move the other jaw toward the blade. Most the force is on the fixed jaw.? I apologize, I was lazy and didn't completely read your pdf. As a result most my comments were not appropriate. I think the 1-inch is overkill but I also thought you were attaching the stock to the jaws. My bad! Mark |
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Re: Vise Jaw Extensions
On Mon, Feb 14, 2022 at 06:44 AM, Rick Sparber wrote:
You make an important point about the blade rubbing. I'll update the article. I may be confused. I was talking about the attachment you posted. The additional jaws attached to your original jaws looked to be about 1/2" thick but then I read the attachment again and it said 1-inch!!!? If this is the case you lose 2-inch of clamping range. The 1"-inch on the moving jaw limits you further because the moving jaw hits the blade guide. How of earth do you bend 1/4 plate? If we are on the same page and have the same saw (which in both cases we may not) something else would likely break before the 1/4" plate would bend. In fact my original fixed jaw is likely less than 1/4" thick in some places. I used 3/8" just because I had it but I have taken if off a several times to have the full capacity of the vise.? ? I attached two pics. the first shows where the blade guide hits the movable jaw and the second is how I hold small stock. And I totally agree about the gap where the blade goes into the table. I need to fix mine.? Mark ?
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Re: Vise Jaw Extensions
¿ªÔÆÌåÓýHi Rick, A simple & clever way to cut small parts on the band saw! As
usual, nice detail! Not sure about all the criticism that came in. It's not like your
small-part jaws go on there, and more importantly, stay there
after installation. Put it on, cut some small parts, and remove
it. I have a few fixtures for doing 'specialty' tasks, including
for cutting small parts. I bought a small vise, for cutting small parts. Pic attached.
Pretty straight forward. (The v-groove in the vise is handy for
small rounds, as pictured) I built a fixture for making angled cuts with tubing. My Grizz
saw cuts angles, but some angles it won't do. I have another simple fixture, which is just a drilled &
tapped plate, for holding odd shaped items using step clamps. I've
made some shorter jaws, longer jaws, and all sorts of goodies, for
tasks where the stock jaws just won't do it. Again, they are not
made to be on the saw all the time. Nice job Rick! Other Bill On 2/12/2022 4:04 PM, Rick Sparber via
groups.io wrote:
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Re: Vise Jaw Extensions
On Sat, Feb 12, 2022 at 06:04 PM, Rick Sparber wrote:
The jaws on my bandsaw do not extend to the blade. There is also a cutout below the blade to enable the shavings to fall away. This makes it hard to clamp small bits of metal for sawing. These drop-in jaws solve the problem. Thanks for sharing although I have a few observations and concerns. First, 1/4" steel would have been totally adequate on the jaws and you have limited your clamping range. Second, the moving jaw will hit the blade guide when the vise is opened very far. Third, the narrow gap under the stock is a plus! Forth, put the larger plate on the back jaw only for the reason listed above. Fifth, when you cut a 45 degree angle the additional plate will be in the blade path (you can remove it when needed). Sixth, *leave a slight gap between the blade and the back jaw (it looks like you did). *I added a back jaw and trimmed a bit off with the saw. It seemed like a logical approach but it was a bad idea. The steel continues to rub on the side of the blade and will dull the teeth on one side. After maybe 20 cuts the blade will start to wander in the cut.?? ? |
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Re: Band saw blade tension
Hi all
Been thinking and there is a simpler way to tension a 4x6's blade that everyone can do at no cost, all it needs is a cellphone. I've made 30sec audio files of a properly tensioned10-14TPI?blade being plucked every 2-3sec.? The 1st file is the blade tensioned?to 22500psi stress for bimetal, the other to 17500psi? stress for carbon steel blades.
Load the files?on your cell phone.
Tension up the blade until the sounds match when you pluck the?back run of the blade. I used the flesh of my thumb or finger, not the nail, as the nail makes a sound that is harder to match.
It's?better than using an App or formula to?work out a frequency and matching to a pure MIDI tone - this is the actual sound of a?blade, at known tension, set with a calibrated loadcell.
Its a bit hard on your fingers so a couple of painless alternatives, that can be used to re-tension the blade, are given.?? This method also provides a way for anyone to calibrate the cheap Chinese ZTTO TC-1 spoke tension meter,?without needing to compare it to a Park Tool.?
I've written out the methods and posted them to the Files section too, along with the audio files. The 3 files are in a single folder called 'Blade tensioning methods' so that they'll be together- jv |
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Re: Band saw blade tension
Hi George I found the calibration data for the 200kg loadcell Not actually zero intercept?but 3 in 8000 is near enough see graph attached On Sun, Oct 31, 2021 at 9:22 AM George Taylor, IV <gtaylor@...> wrote: John, |
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Re: Band saw blade tension
Hi George S-type load cells?work in both tension and compression and these ones have a 7/16 UNC threaded hole in top and bottom, which I made pivot pin type connections to. The blade is just silver soldered to the connectors. Because I bought the loadcell and the reader as a pair, the loadcell just plugged into the reader. Totally Chinese instructions that I could not decipher and?no amount of pressing and holding buttons?etc could I make it read in Lb's or Kgs though its supposed to.? The reader?reads in units of 20g, Reading of 10,000 units = 200kg. A minor pain in the butt but otherwise its been faultless.?? When I calibrated it against the research grade 500kg loadcell on the tensile tester at the engineering school, the thing calibrated perfectly with slope of 1:1 and intercept of zero, so no need to worry about the accuracy of these $20 loadcells.? Even the $5 Airport luggage weigh scales were as accurate. All loadcells?creep a little if left under load, I found?out too, but if you read it within a minute or two it's stable. Easiest to get off AliExpress see the attached Word doc with some screenshots of searches - jv On Sun, Oct 31, 2021 at 9:22 AM George Taylor, IV <gtaylor@...> wrote: John, |
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Re: Band saw blade tension
Ed -? I tested your method and it's perhaps a little high (depending on if the threads are greased or not) My go-to method for many years was very similar:- Tighten it as hard as a normal person can (not a gorilla?or a wimp) without?any aids (like a rag). but I never knew whether that was correct or?not. I have the gear now, so set up the blade with the load cell and standard tensioning rod&knob?per the picture and tested it.
My problem is that it takes time to get it that tight and it hurts my hand, so I prefer to use other?methods. But if you only tension the?blade once in a blue moon, then it's a pretty good method. James -? It actually?needs to be tighter than '...just not slipping ...' , unless you have the bow weight wound back to where there's?not much weight on the teeth in the cut (i.e. bow weight <5lb). If this works for you, the bow weight will be significantly less than you could apply (8lb max on a 4x6 ) with good tension, so the saw will cut slower than it safely could. Low blade tension and bow weight >5lb sends the blade into a degree of 'elastic lateral torsional?buckling', where the top edge of the blade tips sideways. Then the blade?cuts off angle.The more bow weight, the more it tips. It's elastic so the blade just straightens up without damage?afterwards, often pinging away from the cut face at the end - jv On Sat, Oct 30, 2021 at 9:45 AM n5kzw <n5kzw@...> wrote: The method I use was posted on rec.crafts.metalworking.? First tou tighten the blade as much as you can with your hand, then you throw a shop rag on the tensioning knob and see how much tighter you can get it.? This method has served me well on my HF unit for many years. - Ed |
Mark
John Vreede
