Real Smooth Shave

Gave the first new bandsaw blade a quick workout today – the 1/2″ 3TPI bimetal blade.

It has a regular tooth set, and slices beautifully.  When resawing, it vastly out-performed my current 1″ carbon resaw blade – it is obviously significantly sharper – not surprising given how easily carbon blades dull off.

So not only it is superbly sharp, because it is bimetal it will hold that edge for longer.  I guess I have found my new “standard” blade – the one that will stay on the bandsaw by default, so whenever I want to do a quick cut without going to the trouble of changing blades, this is the one that is a jack of all trades. So yes, very happy with this first blade, and looking forward to testing the others.

The general rule is to have as few teeth in the cut as possible.  Too many, and the gullets fill and clog and the blade cannot cut well.  Too few teeth, and the cut is rougher than is necessary.  Having a range of blades, sizes, tooth configurations, tooth numbers will mean you will have the best blade for the job.

Straight-faced tooth with deep gullet to remove shavings.

Deep gullet and 10o undercut face which digs in more, and tends to curl the shavings.  Good for harder woods.  I would imagine though, that it is likely to dull off quicker, given there is less material backing the tooth edge up.

Similar to Hook Tooth, but has the teeth at 90o . Chips rather than shaves – good for materials that would otherwise clog up the blade.  Effectively increases the gullet (which clears the formed chips out of the cut), without having to increase the overall tooth size.

Has a combination of teeth closer together for a finer finish, with some teeth having large gullets for chip clearance.

Bandsaw Blades

Just ordered some new bandsaw blades for my 17″ machine.  Done, as always, over the phone.  Bandsaw blades are one of those things you get made to order, not precut and packaged, sitting on a shelf.  I’d rather have a relationship with the supplier, rely on their expertise, and know they are surviving on their reputation, which means they are only as good as the last blade they sell you, so they better sell you a good one!

Blades come in massive continuous rolls, which are then cut to length and welded.

This latest order comes from my original supplier, Henry Bros in NSW, so I am expecting good things. (And no, I don’t get a discount).

I’ve ordered a 3/16″ carbon blade, a 1/2″ bimetal, and my very first 1″ carbide tipped resaw blade.  I’m rather excited to see what that blade can do!

The point about a CT blade is not that they are the sharpest tool in the shed (no, I don’t mean they are dumb!), but they have excellent durability of the cutting surface.  The resaw blade I have at the moment (which came with the saw as part of a deal) is a very basic blade, and from what I can tell is a straight carbon blade.  Which for a blade needing to survive thick, Aussie hard timbers is basically useless after a few short jobs.

A CT blade is meant to be screamingly expensive, and when I priced one for my 14″ Jet bandsaw (which has a 6″ riser block), it was quite a price that I decided not to bother.  Around $80/metre (plus GST) (and I needed 2680mm), it was over $200.  The equivalent bimetal blade cost me about $40 at the time (1.3 TPI). The 14″ Jet can take a maximum 3/4″ blade, and as it turns out, this really pushed the cost up.

This time I decided that it would be really good to get a CT blade for resawing, so steeling myself against price tag shock, I asked how much it would cost for my 3335mm length blade (which is what I need for the 17″).  $38/metre (plus GST) for a 1″ blade.  Means I am up for around $150 inc GST!  Oh yeah, bring on the carbide tips!

Just a bit on blade material, fwiw

A cheap blade is generally a carbon blade.  Carbon steel in other words.  Cheap, initially sharp, but unable to hold an edge for long.  I don’t but carbon blades for anything but the smallest blades (scrollsaw type work), such as 1/8″, 3/16″, 1/4″ (if I have to).  Anything larger than that, don’t waste your money.

As soon as I can I move into bimetal blades.  These are as they sound –  a blade made from two different metals.  The base metal is a carbon blade (spring steel), but where a carbon blade’s shortcomings are the teeth durability, there is a different metal welded to the front of the blade which the teeth are cut out of.  This is often a cobalt high speed steel, so much more suitable for teeth.

And finally, TCT blades.  Not as sharp initially as the others, but significantly longer lasting, so overall they are sharper on average over the life of the blade.  In the case of the 1″ blade, it has cost me about 3x as much as a standard blade.  A worthwhile investment to my mind.

So when the package arrives (it’ll take a couple of days for the blades to be made and shipped), I will be very interested to see how they all perform.  I pity the timber!

When Worlds Collide

Source: NASA/JPL-Caltech

Really, nothing so spectacular actually.

One of my staff is having a baby soon, so came around to ‘the shed’ so we could start working on a cot.  He’s chosen Tasmanian Oak, so bought some lengths, around 170 wide and 45 thick. (mm that is).

We were too busy to stop for photos, sorry about that!

First job was resawing, so I tried the bandsaw, but had a few problems there.  For one, I think my resaw blade needs sharpening – it really struggled.  I know hardwood is, well, hard but this isn’t the worst thing I have been able to put through this blade.

Combined with the blade dullness, is the increase of load that creates on the bandsaw and therefore an increase in power that is drawn.  Problem number 2 then cropped up – kept tripping the circuit breaker.  Now I know that isn’t related to any fault in the tool, just a underrated circuit breaker that trips at 10A (and probably less), without any threshold.  We ended up giving it away, and swapped over to the tablesaw, with the blade at full height, and two passes to split the board.  Even with two passes (flipping the board over) wouldn’t be sufficient to cut that entire width, but all we needed was actually 145mm, so ripped the board down before splitting.  Even the 15A tablesaw was pushed with such a full-depth cut, and even when changed over to a ripping blade, so perhaps the timber was as hard as the machines were saying.

So we properly dressed the timber all round (using the combination of the jointer (planer), thicknesser and tablesaw).  This obviously isn’t your garden variety DAR – the boards are left flat and true, without warp, twist or bend.

After docking the boards to their required length, it was over to the router table, where a 6mm groove was cut near the bottom in each side, so when assembled it can have a captive base.  By the end of the session, we had made the bed section itself (that has the mattress filling the area, with a maximum of 5mm between the mattress and the sides.  The standard allows for double that).

Once all machined, and edges rounded over with the Fastcap 1/8″ roundover plane, it was onto the Domino to make slots for floating tenons.

We ran out of time to sand and finish – job for another day.

This was part 1 of about a 3 part project. Good using the tools for a bit of furniture again.

Completing timber dressing

The boards have been resawn on the bandsaw, and had a side and edge dressed on the jointer.  Next step is the thicknesser.

15" Thicknesser

I have a 15″ thicknesser, with a fixed head and the table rises and falls.  I prefer this style of thicknesser, but it isn’t everyone’s cup of tea.

The other version has a fixed table, so any additional infeed and outfeed support can remain at the same height, and the motor and blades rise and fall.  Winding the height down isn’t a problem – gravity and all that, but increasing the height is a lot more work, especially with the weight of a decently-powered induction motor overhead as well.

On the other hand, my thicknesser has a motor in the cabinet, and rise and fall is only the weight of the table – very smooth, very easy.  Added bonus, as the head doesn’t move, I have my drum sander located on top,  and a very functional arrangement it is, especially as the thicknesser and the drum sander both have the same requirement for infeed and outfeed.

Dressing boards

With the side dressed on the jointer face-down, the boards are fed through.  There is no point rushing the process – a little taken off each pass will still result in a finished product very quickly.

If I had a spiral head, things may be a little different, but I still have a thicknesser head with straight blades, so loading the machine and chipping away needs a little more finessing.

This doesn’t refer to the ‘spiral’ heads that have a bunch of the small square cutters arranged in a spiral around the head, but are still presented to the timber straight on.  This means the loads on the blades and machine are much less, but they are still chipping at the surface.

Instead, there are spiral heads where the small blades each present to the surface at an angle, producing a slicing motion.  This gives the best finish, combined with the benefit of much lower loads on the tool, and excellent waste clearance.

Completed boards

The boards, now complete (and you can see the bookmatching, if I intended to use the timber for that).

In this case, I now have a dressed side, the other side also dressed and parallel to the first side (and the boards are a uniform 10mm thick).

One edge is also flat, and at 90 degrees to both sides.  This side will be very relevant for the next step – the tablesaw.

How a thickness planer works.

From Wikipedia - a diagram of thicknesser operation

An illustration of the operation of a jointer ...

From Wikipedia - compare the above operation to this one which is how a jointer works.

Preparing Timber – Resaw (part b)

Before beginning a resaw, we obviously need the resaw blade fitted and properly set up on the bandsaw.

Opening both top and bottom doors reveals the blade, tension mechanism, drive mechanism (motor is at the back) etc.

Covers open, revealing the wheels

The top wheel is the tensioning wheel, the bottom wheel is the drive wheel.

Tension wheel and gauge

Around the back is a quick-release lever which takes significant load off the blade and bandsaw when not being used, and during blade changes.

Table support pin

The table support pin is removed – there is a cut through the cast iron table so the blade (which is an endless loop) can pass through to the centre of the table. The support pin prevents the two sides from becoming displaced / moving independently of each other.

Completely release blade tension

Once the quick-tension lever is released, the remaining tension is quickly wound out of the bandsaw, leaving the blade loose on the wheel. It can then be carefully removed.

Coil blade for storage

It is very good practice to coil and store the blade. An uncoiled blade is difficult to store, but in one respect at least if you have the space there is a benefit not coiling. The smaller blades (1/4″ etc) have little spring in them, however the large blades (1″ for example) can have a great deal of energy stored in the coiled blade, so care is needed, particularly when uncoiling. Still, space is a precious commodity – I coil all my blades.

Check out my second-ever episode on Stu’s Shed (1 Jul 07!!) for a bit of a video on bandsaw coiling.

Back off guides

Before installing the new blade back off all the guides, especially when fitting a much-larger blade such as the resaw.

Insert new blade

Slide the resaw blade through the slot in the table then fit it over the two wheels. First retension with the quick-tensioning lever, then wind on the tension until the blade is at the required tension (pluck it, and if you get a High C note, it is about right.

only joking!! But you do want decent blade tension , with minimal sideways deflection when pushed).

Side guides alignment

Bring the side guides into position (just behind the teeth gullets)

Side guides clearance

Then adjust the gap – post-it notes make a good feeler gauge. Don’t forget there is a second set of guides below the table. Bring the thrust bearings up behind the blade as well. Again, a Post-it note provides a good clearance. My take on guide bearings is that they need to be almost touching (but don’t rotate) when the bandsaw is on, and the blade is not loaded up (aka cutting).

Sometimes you need to be able to reach a hex bolt, and the short, power end of your allen (hex) key can reach, but there is no room to operate it. The long end can reach, but you can’t generate enough power to turn it.

A trick I picked up while in the Navy is using a ring spanner to get extra power on the short-end of a hex key.

Ring spanner trick

You can generate significant power this way, so you need to be a little careful not to over torsion the hex key.

Once the blade has been changed, it is time to do the resawing. Depending on how accurate you need to be, you can either free-hand it, or use a fence. When free-handing it (especially when following a line drawn on the timber), you will notice you have to feed the work in at an angle to the blade. This is called blade drift. All bandsaws do it, and it is a combination of the blade, blade tension, and the timber. If you are using a fence, you still need to take this into account.

There are many fences available for bandsaws. Some come with the saw, some are aftermarket. My favourite though, are the MagFences from MagSwitch. They use switchable magnets to lock down onto the cast iron table wherever you need it, and at whatever angle to the blade that you want.

Ideal resaw fence (MagSwitch)

The single-roller MagFence has the roller set proud, with the remainder cut away (again, so they don’t get in the way of the drift).

MagFence clearance

My method of using the fence is to lock it down at the distance from the blade that is equal to the thickness of timber (or veneer) you want to produce.

MagFence alignment

The rollers are set to line up with the teeth, and again I choose to line them up with the bottom of the teeth gullet.

Ripping a veneer

Ripping mm (or less) veneers is easy once everything is set up correctly.

Accurate resawing

If you want to split a board down the middle, you can either measure and assume it is accurate (including taking into account the kerf of the blade), or while holding the work against the fence, touch the blade with the timber. Then, flip the board over and touch the blade again. Between these two cuts is the true centre of the board.

This will give you the boards you need. If they are still green, you need to leave them to season. Next, we need to start the machining – joint/plane and thickness.

Addendum:

As Larry has correctly pointed out, I tend to use “bandsaw tracking” when describing the phenomenon of a blade running at an angle to a drawn line (or “track”) on the timber, and “blade tracking” to describe how the blades are running on the bandsaw wheels.

The common terms however are bandsaw “drift” when it cuts at an angle to a given line, and blade “tracking” for how the blade runs on the wheel.

I don’t like the term “drift” – it implies the bandsaw is not working correctly, and it is drifting all over the place instead of cutting straight, but for the sake of clarity, I have amended this article to the common nomenclature.

Way of the Dado

The dado blade – taking a standard sawblade, and deconstructing it into its various elements.  Then taking one of the fundamental variables of a saw blade and making it variable, making it controllable.

Normally, we accept (and suffer) the kerf (the width of cut) of a sawblade.  When you cut a piece of timber, the kerf is wasted timber – it is turned to dust and sucked away.  The thinner the kerf, the less material is wasted, and the less power the saw requires to drive the blade.  But then, the thinner the teeth (more susceptible to damage, and less resharpening opportunity), and the more flexibility of the blade.  It seems the most popular kerf is 3.2mm.

However, there are times when you want to have width to the cut.  If cutting a long slot (a dado, slot or trench depending on your country’s definition), then doing this on the tablesaw is a lot faster, and puts a lot less load on the machine than trying to do it with a router bit.  So the dado blade is one where the alternating top bevel is now on different blades (a left and a right one), and the chipper teeth are on chipper blades that sit between the two outside ones.  By adding additional chipper blades, the kerf of the assembly can be increased, and then finetuned with thin shims.  This obviously cannot be done with router bits, so now the dado blade has two advantages over completing the same job with a router bit.

A router bit can plunge and cut a stopped dado, a dado blade cannot, and there are other instances when using a dado blade is not the method of choice.

But when you want one, they can really do the job quickly, easily, and repeatably.  So long as they are a good quality set.  So far, the dado sets I have used have been a disappointment when it came to testing them, so rather than run through all the potential variables if this set (the CMT 230.524.08 8″ 5/8 bore to suit my specific saw, from Carbatec) can cut a decent trench, it will be the winner – all the others I have tested so far have been rejected.

Here I have assembled a 16mm dado stack, mounted in my tablesaw and already plunged up through a wider insert that I made for my tablesaw from MDF.  The maximum size dado the set can create is 25.4mm (1″), but this is wider than my particular tablesaw can cope with.

The blades are 1/8″ each (and you must use both for all setups) so the minimum dado width is 1/4″  If you use all the chippers and the shims, you get the maximum dado size of 1″.

The chipper blades are 1x 1/16″, 1x 3/32″ and 4x 1/8″

The shims are 2x 0.020″, 2x 0.012″, 2x 0.008″ and 2x 0.004″

I also chose the 5/8″ bore version to match my current setup.  Most of my other blades have a 30mm bore (from memory) and then use an insert to get them to match my saw.  But if I was to try that here, I would be juggling one for each outside blade, then one for each chipper.  Too much stuffing around just to future-proof a dado set.  And I’m not planning on upgrading my tablesaw any time soon (not unless a SawStop Pro or Powermatic  falls into my lap!!!)

My tablesaw is 10″, but I’ve chosen to have an 8″ dado set.  That might seem strange – why not get a dado set that matches the capacity of the saw?

This is actually a very common practice.  A normal blade is only 3mm wide, and if it takes a significant proportion of the saw’s power on the most testing of cuts, what would it mean if you tried to spin up a dado set that could weigh 5 – 8 times as much, and then push that thickness through a block of timber?

So a smaller diameter blade is significantly less weight to spin, and even the splitters are weight-reduced with portions selectively removed to decrease the power required to drive them.  Even so, this set is no-compromise.  The splitters are 4 tooth on a full disk.  Some dado sets have very limited splitters, more like a airplane prop than a blade.  Not sure which I’d prefer, not sure I care (other than 4 teeth are better than 2)

The biggest reason for going for a lower diameter blade?  You don’t need bigger!  This is for dados, not for sawing timber in twain.  And creating a zero-clearance insert is much easier and safer when the blade can be wound down into the table far enough that it fully clears the bottom of the insert.

Not the best photo, but you can clearly see the outside blades have a combination of bevel tooth and chipper, and the chippers in the middle only have chipper teeth.  Also, you can see that the width of the chipper teeth is not important – it is the thickness of the body that determines the full stack width.  So the wider teeth make for overlap, to ensure they fully clear out the slot.

Setup for the dado cut.  The fence is locked down and the timber held against it with the latest featherboard from MagSwitch (the reversible featherboard on the universal base).  The guard and splitter are removed – cannot be used with a dado, or partial depth cut.  A zero-clearance insert is in place (shop made) and the blade set for the depth of slot required.

Setting the dado height, you have to be careful NOT to measure to the height of the bevel teeth – they do cut deeper than the depth of the slot as you will see in the next photo.  You measure to the top of the chipper teeth.

But the final truth is simple: can it cut a decent slot with a flat bottom or not?

Yes, it can.

You can see how the bevel teeth cut a bit deeper at the edges – not ideal (although pretty normal for dado sets).  It ensures there is a sharp, sliced corner rather than a rougher chipped one.  That’s not a bad thing – only matters at all if you are going to see the end of the slot at all (and you can see it is pretty minor even so)

This slot took no time at all – it really demonstrated to me just how useful a dado set is if you have a fair few slots to cut – blows routing them completely out of the water.

So the bottom line.  This CMT dado set is a win (as is the storage case personally – industrial, tough, and functional).

The CMT 230.524.08 8″dado set, from Carbatec.  This has a 5/8″ bore.  For the 30mm version, it is the 230.524.08M

Enter the Dado

What is now a few years ago, I ran a comparison “Battle of the Blades”.  I tried to be very comprehensive with it, and learned a lot about blade construction and the effect of the different variables on the quality of the resulting cut.

I was intending to then conduct a “Battle of the Dado Blades”, but ran into a major problem – none of the dado blades I had to try were worth promoting.  Not one was good enough.  The Linbide Dado set had an unbelievable problem – the chipper blades were a tooth count that was not compatible with the outside blades (such as having 7 teeth, when the outside blade had 24 – can’t remember what the actual count was) which means you are assured of having a tooth of the chipper blade impacting on one of the outside blades, and that means there will be a gap that causes the blade to have a wobble, or at least risking cracking a tooth.  Apparently there were a lot sold, and incredibly I was the only person who had picked up on the error.  The CMT blade could not produce a flat bottom to the dado – one of the chippers was the wrong diameter (by a mm or 2), again, stupid fault in manufacturing.  Couple of others were equally eliminated.

Linbide fixed the design fault (apparently – although I have not seen it to confirm or test since), and CMT withdrew the model I tested.  It has been a long time coming, but there is now a new CMT dado blade available (probably been out for a year or so)

This is a interesting new blade – 8″, 24 tooth, with 4 tooth chipper blades (of various sizes) (Model 230.524.08)

I like the case as well – a good way to store and protect the blades, the chippers and the shims.  Not as elegant as a nice orange case, but then very functional – I find the chippers harder to get out from the foam inside the orange plastic case.

The blades are 1/8″ each (and you must use both for all setups) so the minimum dado width is 1/4″  If you use all the chippers and the shims, you get the maximum dado size of 1″.

The chipper blades are 1x 1/16″, 1x 3/32″ and 4x 1/8″

The shims are 1x 0.020″, 1x 0.012″, 1x 0.008″ and 1x 0.004″

But using different combinations of chippers and shims, you can get a large range of widths.

Now obviously, this is an imperial set (haven’t seen a metric one), and what I am confused about as a general comment on dado blades, is why?  Not why is there only imperial blades – I don’t have a problem with that, but why are they not supplied with (or why is there not an after-market set available) of shims that convert them to metric?

For example, the two outside blades added together come to 6.35mm.  If a 0.15mm shim was included, you would get a metric 6.5mm dado.

It would be easy to include an extra set of shims that allowed each chipper and blade combination to produce a metric set, and some additional shims (such as 0.1mm, 0.2mm, 0.3mm and 0.5mm) for fine adjustments. The existing shims are close enough to this.

Looking forward to putting this set through its paces, and seeing if I can finally get a square bottomed dado!

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