John,
Seeing as how this is a new topic, I thought I’d take the opportunity to ask a couple of questions about tablesaw blades.
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The first question concerns sharpening of TCT teeth. I recently had a blade sharpened via a local sharpening service but wasn’t impressed with the results. The blade was begining to need a bit of extra push to cut the thicker timber pieces but still cut OK. (It has cut lots & lots of hardwood since new). The returned blade seems no sharper to me. In fact, I suspect they may have made it slightly worse as I now get a burnmark or two in addition to needing a firmer push of timber through the blade! A decent sharpening service in Blighty is proving hard to find.
Anyway, the first question is:
if I want to sharpen the TS sawblade myself (all 40 teeth) what part of the tooth is it that I use the diamond file on; and what grit of diamond will do the job? I have 300, 600 and 1200 grit diamond plates of a suitable (small) size….?
A supplementary question:
how many (a range) strokes of the diamond plate is likely to be needed per tooth to increase it’s sharpness, assuming it is not really blunt now but not optimally sharp either?
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A second question-set concerns the use of a thin kerf blade. There are quite a few 250mm (10in) blades on the market now with a kerf of 2.8 or 2.4mm. All my current blades are 3.2mm and the riving knife is 3.0mm to match. A thinner kerf blade might help when cutting thick pieces of the really hard stuff – teak, iroko and similar. The second question-set is:
will I get away with leaving the 3.0mm thick riving knife in if I use a 2.8mm kerf blade?
if not, what kind of steel should I employ to make a new, say, 2.6mm thick riving knife, in order to keep the requisite stiffness/strength in the knife?
With a fully-raised 10″ blade (just over 3″ cutting depth) what is the safe limit for blade/tooth thinness and corresponding riving knife thinness?
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The saw is a European 10″ cabinet saw of 3hp output with no significant runout of the arbor and is vibration-free (enough to allow a coin to remain still and stood on it’s edge). It is a heavy item (around 125 kilos) with a cast iron top. The riving knife is blade-following and I generally set it 1.5mm from the blade.
Thanks in anticipation.
Lataxe
Replies
Lataxe,
Presumably what you are calling a TCT grind is some version of a triple chip tooth grind, where half of the teeth are square tipped and the alternating teeth have three faces on the tip, a short horizontal center and two sloping bevels. These are generally used for cutting veneers and other easily chipped sheet goods such as laminates, they are not the best choice for sawing solid wood.
The geometry of these blades is very precise, in addition to getting the angles right as the teeth are sharpened the height of each three faced tooth is slightly higher than the height of a square edged tooth. As you have discovered, many smaller saw sharpening shops have neither the expertise or the sophisticated equipment needed to do this work properly. I have always used either Ridge Carbide or Forrest to sharpen blades, they have the very expensive grinders needed to do this kind of work. I don't know of any equivalent service in the UK.
I am being called away for a minor emergency, I'll have to finish up later, sorry.
John W.
TLAs
John,
You have been accosted by the three letter acronym (TLA) dawg. :-)
TCT = tungsten carbide tipped; any sawblade that has brazed-on tungsten carbide teeth.
The blade I want to self-resharpen is an ATB = alternate bevel angle of around 10 degrees each way. The teeth are all the same falt-faced items, except for the alternate bevel angle tooth-by-tooth. The sides of the teeth are also slightly bevelled inward from their faces (sp they do not rub on the kerf) and have a slight forward angle of attack. Thus only the top edge of the teeth chisel out a shaving, with the tooth face, sides and rear missing the wood as the teeth travel through the kerf.
So, I'm presuming that resharpening only needs the face of the tooth to be ground off slightly with the diamond file, until a possibly degraded top tooth edge is restored to a nice sharp aris.......? I'm also presuming that the tooth sides and rear do not need to be filed......?
If so, how many diamond file swipes of what diamond grit-grade is likely to take off enough tungsten carbide from the tooth face so that the top cutting edge is restored, assuming it is not visibly degraded yet "microscopically" blunt?
Lataxe, trying to be explicit.
Lataxe have you tried calling round a few local cabinet shops to find out who does their sharpening .I think that it is better to find a service with robotic /cnc grinding than messing arround with 600 grit files yourself.At some point you will probably damage teeth and need brazing ,side grinding etc to sort it .Therefore I would suggest the sharpening thing is a way to source good help for when you need it. I have had tools damaged on occasion by bad operators at good companies .However they usually sort it out at no cost.I seem to remember a company up near Bradford who did sharpening Kieghley might have been in the name but not as the location.I travel both side of the Pond but usually am near Pompy ,indeed as of now. Regards Jako
Lataxe,
For hand sharpening I would do as you suggest: just filing the face of the tooth pushing it back until the rounded over edges of were removed. Although this technique works reasonably well when touching up router bits, I doubt if it would be practical to try to sharpen a 40 tooth blade by hand and expect it to come out cutting as well as a blade that was properly ground on a computer controlled grinder.
If you want to try it, the blade needs to be solidly clamped in some sort of stand so that the face of the tooth is facing up and parallel to the bench top and you will probably have to use a magnifier and excellent lighting to see how the filing is progressing.
I use DMT diamond stones on carbide router bits and the like. I start out using their red files, 600 mesh, 25 micron, followed by their green files, 1200 mesh, 9 micron grit for finishing. I have found that filing with coarser grits can cause the edges of the carbide to chip. With magnification you should be able to see when the first tooth is sharpened and you should then take the same number of strokes on each tooth to keep the teeth as even in size as possible.
lataxe,
some years back the school district that i work for stopped sharpening our carbide anythings. apparently a very toxic gas is a by-product of sharpening carbide and the tool sharpeners took exception to being slowly poisoned. shame, really. they used to happily take care of all my personnal router bits and saw blades. maybe john will clue us in soon....
eef
Gasbogeys
Eef,
The underlying message from all seems to be - find a decent sharpening service with the right equipment to do a proper job. I confess that this is what I would prefer, if only I could find such a service in Blighty.
Your gas-tale is interesting and new to me. Tell us more, specifically the description of the chemical reactions involved using standard formulae. :-)
Lataxe
lataxe,
your nation could, in some circles, be described as "the vanguard of western wood working." were it not for you folks teaching the colonials what's what with wood, well, these americans would be sitting on tree stumps whilst eating off of fallen logs. you brits are ear-deep in wood making traditions and you mean to tell me that in all of anglia you cannot scare up a single carbide sharpening service?!? what, do you guys use disposable blades?
eef
Blade Sharpening
I have difficulty believing there is a shortage of competent sharpening services near by. There are many over here in the colony but the cost of having the royals or any of their competitors actually transporting the blades for a reasonable price will not be.
Some of the manufacturers Ridge or Forrest offer services. There must be someone over there surely. If not, send em over!
We have some good guys right close by.
As for the gas bogeys, I worked for a company that made all kinds of tungsten carbide, tungsten titanium carbide powders primarily for the aerospace market - GE , Rolls, Pratt etc,. Never heard of anything really bad about them although as a metallic dust good respiratory protection was required when handling. I would not be at all surprised to hear that commercial saw sharpeners failed to ensure adequate ventilation and respiratory protection for their workers.
Don
Toxic Gas
Apparently Tungsten Carbide dust can cause respiratory problems, like the other xxx thousand chemicals we can be exposed to.
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