bandsaw blade question

[Simon Magennis]

I have a small "hobby" type bandsaw. The blade is 1790mm - 70.5 inches. The blade delivered with it was 3/8" x 6tpi. The blade has broken so I need to replace it. (I reckon if would be easy to fix but I don't have the means and don't know anyone local who does it). I am in a relatively isolated area in Europe which limits options.

The original was 3/8"x 6tpi. My immediate feeling is just order a direct replacement as being "good enough" for general use. So the question is, is there any reason why a different blade would be better?

I will order a couple of blades. I am a bandsaw newbie so I am still feeling my way. The saw is only for cutting out backs and tops and other small things such as bits of wood for jigs and occasional chunks of plywood or mdf for making soleras or bits and pieces for the house. So there are two requirements: cut reasonably straight when needed and cut guitar type curves in backs and tops and occasionally in mdf/plywood for soleras.

The choice from the original supplier is 4,6,10, 14, 24 tpi
And widths 1/4, 3/8, 1/2 inches.

This is the supplier.
(https://www.axminster.co.uk/bandsaw-bla ... =AWHBS250N)

[Brian Evans]

I bit the bullet and now have several different blades. I use a 1/4" 8 tpi toothed blade when I cut curves, and a 1/2" 4 TPI when I resaw. I use a metal cutting blade when I cut aluminium. When resawing it's important to have not only a wide blade for stability, but also few TPI so the blade can clear sawdust and chips better.

[JC Whitney]

The rule of thumb I was taught for choosing tpi was to always have at least 3 teeth in contact with the material you're cutting, and it's served me well through the years.

[JC Whitney]

If you Google "Highland Woodworking bandsaw_blade_selection_guide.pdf" and choose the first .pdf result it's a very useful guide to blade selection and troubleshooting.

[Peter Wilcox]

The original was 3/8"x 6tpi. My immediate feeling is just order a direct replacement as being "good enough" for general use.

If you're not doing any resawing, this should be fine. (Get a couple so you have another when it dulls or breaks.) If you want to resaw, get a 1/2" by 4tpi too.

[Alan Carruth]

Blade width is actually limited by the strength of the frame of the saw. You can think of it like a string on a guitar; it won't work well if the tension is too low, and a thicker string/wider blade requires more tension to work right. My understanding is that the smaller hobby saws can't carry enough tension for a blade wider than a half inch or so. I have certainly found that my Jet 14" saw with a riser block does better re-sawing with a good 3/8" or 1/2" blade than it does with the wider ones. Mine takes a 103" blade (2616mm), iirc.

The best re-saw blade I've used have a varying tooth count. That is, there will be 1" at 4TPI, and then 1" at 3TPI. When it's cutting the blade can seem to rebound a bit and then jump forward to engage the work again. If the tooth count it always the same it can jump back into the cut in such a way that the teeth are all deeply engaged, which causes a stronger rebound. The saw surges forward into the cut and then bogs down. The cut gets rough, and ends up going more slowly. Varying the tooth count helps prevent that.

[Simon Magennis]

Thanks for all that. Given the shipping cost I was planning to get more than one anyway. Now I have better info to make the choice.

[David King]

Smaller wheels necessitate a thinner blade that can bend around the wheels without developing cracks. Unfortunately there are very few blade stocks that can meet that requirement so you are immediately limited. It's important to find a supplier that can get accurate and consistent results at the weld. A factory weld may just be your best bet. The place with the widest array of blade stocks is Iturra Design in the USA but I'm not sure they'll ship beyond Canada. You can browse a 2005 copy of his catalogue in PDF format here: http://www.businessmarketinginstitute.c ... iturra.pdf
Your best bet since he's never gotten a website together.

[Simon Magennis]

Rather than start a new thread I am adding a question here.

What tpi would be appropriate for cutting perspex/acrylic for making templates?

I assume a finer spacing would be better. As the original 3/8" x 6tpi was back ordered, I went for a 3/8" x 10tpi and a 1/2" x 4tpi. I reckon the 10tpi for perspex, tops and backs with the 4tpi for anything thicker.

[David King]

Simon,
That should work. Heat is the enemy here so if you can slow the blade down or find a way to drizzle alcohol onto the blade at the cut. I use a big shop vacuum to pull the heat away from the cut. A sharp blade is probably the most important factor so it might be wise to set a bade aside just for plastic.

[Simon Magennis]

Thanks David. I will give it a shot in the next couple of days.

The supplier's answer was essentially that they have only ever tested my bandsaw for wood so they would not recommend anything for plastics. When I asked if they had suitable saw for plastic - the same answer. I can understand the cya answer. They specified the heat issue.

As this is the very first time I replaced a blade I spent a lot of time looking at the components - pretty primitive on a cheap machine like this - and went through all the set-up stuff again and looked at a couple of videos to. Very useful. I also came to the conclusion that for most things I will be doing with it, the 10tpi blade is probably a good choice.

[Bob Gramann]

I use a 10 tpi blade to cut acrylic plastic and polycarbonate. When cutting the acrylic, it makes a ridge of melted plastic along the cut that easily comes off when the cut is done. If you’re making something that you will use more than once, you might consider the polycarbonate (aka “Lexan”). It’s a lot easier to machine and a lot less likely to crack. With the polycarbonate, I can clean up the cut with a plane. Nice, thin shavings come off.

[Clay Schaeffer]

For cutting thick stuff with a small bandsaw I like to use a 3 TPI skip tooth blade. The narrow blade has less drag and the skip tooth provides more space for the saw dust the thicker cut generates.

[Simon Magennis]

Thanks Bob, Clay.
Not sure what the "perspex" I have is. I'll check the description.
I will look into a skip blade the next time. There is one available form the supplier but I was not clear if it was useful or not.


Another Q.

Any uses you can think of for a broken (3/8" blade)? I suspect it is just my squirrel self thinking it might be good for something "in the future" - the rational me says "bin it". Its taking up space and nothing comes to mind about when it "might be" useful.

[Mark Fogleman]

Simon if you have a gas torch (propane, butane or map) using a 45% silver solder, paste flux and a diy blade holding jig made out of a short section of angle iron and 2 binder clips will serve you well if you plan to continue in the business. You can buy bulk band saw blade stock and make your own for a few euros each. Here's a good Youtube which details how to do it: https://www.youtube.com/watch?v=QFQASBgKUB8 Here's a good post by my old machine mentor: http://www.owwm.org/viewtopic.php?f=1&t ... ver+solder

[Clay Schaeffer]

"Any uses you can think of for a broken (3/8" blade)? I suspect it is just my squirrel self thinking it might be good for something "in the future" - the rational me says "bin it". Its taking up space and nothing comes to mind about when it "might be" useful."

If you are so inclined you can use it as a blade for a frame (bow) saw.
The 3 TPI skip tooth blades I use are 1/4 inch wide - again the narrow width has less drag.

[Bryan Bear]

I'm glad you said that Clay. I have several wide blades that are too dull but I havn't thrown them out. I keep telling myself I'll sharpen them but I know I won't. It would be nice to make a bow saw or frame saw. Sharpening fewer teeth seems more doable. I could certainly use a bow saw for cutting up the never ending supply of limbs and sticks in the yard. I can make all the neighbors feel less manly when they see me doing it Roy Underhill style <G>

[Mark Fogleman]

A diy Shinto rasp?

[Alan Carruth]

A few years back we had a local luthier's meeting at my shop. Somebody mentioned using a Dremel to sharpen bandsaw blades. They simply held the tool at what looked like the correct angle, and used the side of an abrasive cutoff wheel to touch the front edge of each tooth. I tried it, and it certainly got the saw sharp. The problem was that I couldn't hold the angle well enough to get the teeth to all be the same, so it made a fairly rough cut, and had a lot of drift.

As a stop gap jury rig I made up a bracket that would hold the Dremel at a good angle, and screwed it down to a small piece of plywood. A strip of wood screwed to the bottom runs in the guide slot on the saw table. I drilled and tapped a hole in a piece of Delrin, and screwed that down to the play base in line with the saw cut made when I slid the sled forward. A setscrew in the tapped hole locates off the gullet of the teeth to give a more or less uniform depth.

In use I first unplug the saw motor, and find the weld. If I can't find that I just mark the blade so I'll know when I've hit all the teeth. I run the sled in and set the setscrew so that the wheel barely touches the surface of the tooth in front. A 'dull' saw only has a tiny flat on the tooth, and you don't need to remove much material to make it sharp. I get comfortable on a tall stool and hit each tooth lightly, pulling the blade up with my right hand when the sled is retracted, and running the tool forward until the setscrew hits the bottom of the gullet. On a typical 105" resaw blade the whole process takes about twenty minutes. The blade will end up at least as sharp as new. I can get three or four sharpenings out of a blade. Usually they break, but I've had a couple where the teeth got low enough that the gullet was no longer sufficient to clear properly. You also lose set, of course.

For re-sawing I use a tall fence with an adjustable angle. I have to re-set the for the drift every time I re-saw.

One revelation I had was that you can use this method to sharpen carbide tipped blades if you get a diamond cutoff wheel. This is a real saving. Many of those blades use an alternating angle: left-center-right-center. I've had good luck simply grinding those back to straight across.

There is an issue with certain re-saw blades; the ones that alternate between 3-4 TPI: you can't set up the depth guide on the gullet. On those you'd probably need to use a depth set that guides on the un-filed teeth. This could be built into the base easily enough, and, of course, would work for saws with even tooth spacing as well. For that sort of stop you would probably want to turn the saw backwards by hand while you jointed off the tips of the teeth with a file or diamond stone to get them even.

Some folks object that band saw blades don't cost all that much, so why not just replace them? It takes me about as long to replace a resaw blade as it does to sharpen one, and even with 6-tooth blade, which takes longer to touch up, you're still out the cost of the blade. Besides, it just goes against the grain to throw out something that can be re-used.

The original plan was to try out the idea with a quick and dirty setup, and then go to the Delux version, with easily adjustable angles and so on. The jury-rig worked so well I'm still using it, more than a decade later. I could get a picture and post it, if you'd like, but the idea is simple enough that I hope the description suffices.

[Bryan Bear]

Yet another fantastic post from you Alan. I'll have to try this soon. I've been putting off resawing some boards because my last resaw blade is dull. It sounds like I have little to lose but time. Can you post a picture of your set-up for inspiration?