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Reducing kerf of carbide tipped band saw blade on surface grinder?

richard newman

Titanium
Joined
Jul 28, 2006
Location
rochester, ny
I'm wondering if it is possible/practical to reduce the width of a carbide tipped band saw blade using my Boyar Schultz 612 manual grinder.I intend to resaw a quantity of Brazilian Rosewood, old Cuban Mahogany and Gabon Ebony into guitar backs & sides and fingerboards, and the material is so valuable if I can get an additional slice or two it is well worth some effort.

I have some Lenox Tri-Master 1/2" x .025" 3tpi carbide blades, takes a .060 kerf, would like to reduce that to .040" or less. The blade is a triple chip grind, doesn't seem like losing .010" per side should affect it's cutting ability, and I'm not cutting any curves. I'm thinking to make a fixture to hold the blade stock at a slight angle from horizontal to provide clearance and just kiss the carbide.

With a diamond wheel, how much can I take off per pass? Blades are 12' 6", would a wheel hold up for an entire blade or require dressing? What kind of wheel would be best?

I also have some coils of Lenox Diemaster bi-matallic blade stock. I have successfully reduced kerf on that from .050" to .035" squeezing in my Kurt vise, and used that for resawing curly maple, but the exotics are pretty tough even on hss blades, carbide lasts much longer. But if grinding the carbide is impractical, I can fall back on that.
 
Hi Richard:
Are you OK with having no set left on the teeth or were you going to grind each tooth individually with side and back relief but to a narrower width?

A resin bonded diamond wheel will have no trouble doing a run of 432 teeth (3TPI and 12' long)...I have wheels that are 30 years old and still have much of their diamond layer despite being used probably 100 hours per year.
That's a lot of grinding compared to what you want to do.
Carbide is sintered (well sort of...it's actually carbide grains embedded in a cobalt matrix) and that means you can take heavier cuts when you grind it than you can with something like HSS.
You could probably take 0.005" in a creep feed pass if the grinder, the fixture and the braze that holds the teeth on the saw back can hack it.
The best guy on here to tell you what you can get away with grinding dry on a small grinder would probably be Carbide Bob.

If you plunge grind wherever possible you can preserve the geometry of the wheel at the corners well enough to do what you want.
You'd have to figure out a fixture to twist the blade enough to present the side of a single tooth to the wheel at a time.

By contrast if you just knock all the set off the teeth I'd expect it to smoke and burn like crazy in the cut, but I've never tried it so I don't know if that's actually true.
Cheers

Marcus
Implant Mechanix • Design & Innovation > HOME
Vancouver Wire EDM -- Wire EDM Machining
 
Richard -
It has been a while since i ground carbide. Tend to avoid it anymore because of the health hazards.

I'd probably try a wheel around 180g 75%. If you have 220, that would be good. probably not coarser than 150 for a sawblade. In truth, most of my wheels are 100% but my understanding is that 50% or 75% grinds a little cooler.

If the wheel never touches steel, it will last.

Per what Marcus said
You could probably take 0.005" in a creep feed pass .......snip.....If you plunge grind wherever possible you can preserve the geometry of the wheel at the corners well enough to do what you want.

That is a hint that crowding diamonds is not productive.

Per my own thoughts on the subject:
Assuming a wheel at least 6" diameter, i'd consider setting the blade fixture/guide on the surface grinder up so the cut is a hollow grind by means of infeed (lock the table longways) This will make the wheel grind at its coolest & most aggressive; and it removes one axis of tilt in your set up. **If the guide/fixture is also set with tilt top-to-bottom even minutely, it will probably improve the woodcutting, and it will make it possible to sharpen the band just with a face dress, for several cycles.

Using infeed/hollow grind on a surface grinder is tough for a BS blade due to clearance issues with the column.
However, since the back rake is set by the position of the tooth tangent to the wheel, the fixture need not position the band flat to the table. It could be vertical, or somewhere between vertical and flat.

I can't recall if you have a T & C? The set up might be easier on a T & C. But the surface grinder should work. Don't over-do the side rake, just so it exists.

Also, don't forget the poor cue makers when you are planning your rough bust-up of the blanks. Lots of narrow rips, if full thickness, as well as short but fat chunks can be useful to cue & pen makers. :)

**(edited) - actually, the geometry of the front clearance on the tooth, combined with the hollow grind/side clearance, will yield top-to-bottom clearance. So might not be necessary to add any more.

smt
 
Thanks for the replies gents, but I'm beginning to think this might be too crazy, even for me! Also thinking that I'd be seriously altering the triple chip geometry, as I could only grind the flat top raker teeth and not the trapezoidal teeth. Might not cut properly, after all that effort.

I used to get good results with the bi-metal blades, just have to change them out as necessary. An interesting little thought exercise tho...

Stephen - I'd only be resawing the quarter sawn stuff, have way more flat sawn for cues and such. How much do you want? ;-)
 
Richard -
I do need to make a trip up there!

My biggest reservation about grinding the bandsaw teeth is the health hazard in a shop that is not already "well" equipped to deal with the dust. I would grind wet, and use rubber gloves - (the wet stuff can be absorbed through the skin.) If you grind dry, absolutely use a "perfect" vacuum system/filter. If you can smell that carrot smell, the dust is already getting where it should not. Even if you wear a good respirator or supplied air hood (I do, these days) the dust will go all over your shop and settle in your wood supplies to come out as a regular low level dosage for quite a bit of the ongoing future. Even if you and i are entering our dotage, it is not a good legacy to leave for others.

Do they still make stellite BS blades? Those are sharper than carbide, and can be ground with regular AlO wheels.

smt
 
This is unresearched/out of the box a little bit, but how thick are your slices? Thin enough to 'slice' with a knife of some sort? I know veneer is carved off logs in rotation, but is it also done in a linear fashion -- like a "power drawknife"? Sounds like some serious machine and blade rigidity, plus horsepower and workholding challenges. New life for a (modified) stroke sander? High risk, but zero kerf loss. Or have I just confirmed I'm an armchair idiot?

And on edit: upon reflection, it would be a challenge to slice it (where you want) instead of splitting it like a cedar shingle -- which is roughly where you want, but still subject to being steered by grain, wood imperfections, etc.
 
And on edit: upon reflection, it would be a challenge to slice it (where you want) instead of splitting it like a cedar shingle -- which is roughly where you want, but still subject to being steered by grain, wood imperfections, etc.

I'm pretty sure that the veneer peeling is done in rotation is on wet wood. See here for an example (first debarking then veneer peeling). I think this is for plywood not furniture.

Rotary veneer cutting machine;veneer peeling line;veneer stacker;wood debarker; - YouTube

Edit: it turns out that veneer peeling and slicing is usually done to wet wood, and often the wood is first heated, see:
https://www.fpl.fs.fed.us/documnts/fplrp/fplrp228.pdf
 
Last edited:
Yes, veneer slicing/peeling is done on wet wood that has been thoroughly cooked. And it doesn't work very for thicker veneers, lots of micro and not so micro cracks as a result of the veneer peeling off the knife. So, never done for acoustic guitar parts. Too bad, sawing probably ends uo cutting the yield by 50%. Sides and backs often wind up approx 3/32 to 1/8" after sanding.

As to grinding the carbide blades, I hadn't given much thought yet to dealing with the toxic dust. It's pretty clear to me that I really am not equipped to safely handle this, so that definitely puts the lid on this project. Would prefer to die in bed during wild nonagenarian sex.

And I'm pretty sure someone in Europe makes Stellite tipped blades, but I'm just going to use the bi-metallic stock I have and keep it simple.
 
Richard,
I used to sharpen my Lenox trimasters by grinding just the front of the tooth--very successfully. Each grind (I got three or four per blade) reduced the kerf slightly but not to the degree you are looking for. Trimaster blades are NOT set, the clearance is derived from the difference between the thickness of the carbide tooth tip and the band. (similar to a swaged tooth blade) I agree with your conclusion about the bimetal blades. My all around favorite for thin kerfs is a lenox 1/2" 4T Diemaster-2. I improve the performance of this by again grinding the face of each tooth straight across in rip configuration, while reducing the rake to about 7° from the factory 10°. I do this in a simple indexing fixture in a cutter grinder. Factory kerf on this blade is .044-.046, and each grind reduces the kerf by .002 or .003" depending on how heavy a grind you do. Sweet spot is when the blade is cutting about .040-.042" kerf. I've done the same treatment to 3T blades but Lenox 3T Diemaster-2 is only available in .035 thick bands with heavier kerf IIRC it's about .050-.052". For me, the 4T configuration works as well or better than 3T in the harder exotics like you are sawing. To answer your original question, grinding the sides of your trimaser is a bit of a "fools errand"!

Regards
Bob
 
*I think they are not real carbide but electroplated carbide on steel. I had some router bits that were advertised carbide and could be ground with an Ao wheel. If so they would beat up a diamond wheel.
With 3TPI you are looking at 900 teeth to grind so that is not so bad. .025 to .060 gives plenty of clearing with .007 per still thicker than the blade at .045. You could set a vise at 7 or 10* angle to long travel, with a shim under to kick cross-way up 10* for side set, add a finger stop to line up each tooth to a vitrified cup 220 wheel to grind all right teeth and the swing set-up to grind the other side teeth. Ye choose angles that would still clear the blase body (.025) so to better serve (Just miss) the wheel wear.
Having an abrasive wheel dressed you can dress a carbide cup wheel back to a sharp edge. a Crackerjack Mini dresser type. likely 5 seconds per tooth x 900 per side...with using multiple passes.

Wet likely best..and I now wear a mask for grinding..after many years of not doing so.. but mostly had good air systems and care with dust.

likely a 3 or 4-hour job with using down travel on a surface grinder.

*Tipping the blade 7 or 10* and grinding, all the same, is a much faster way, might be tried. Yes likely 1 foot sections.. an AO wheel might work.

*and Bob's suggestion grinding the tooth gullet back is an option.

* and likely it could bend to more narrow, perhaps running it through a roller device.
 
Can you do it with a waterjet? I don't have a clear picture if the thickness you are trying to cut but I have cut a bit of wood with mine and have impressed.
 
*I think they are not real carbide but electroplated carbide on steel. I had some router bits that were advertised carbide and could be ground with an Ao wheel. If so they would beat up a diamond wheel.

Buck - if they had clear brazed on tips, those might have been stellite.
A lot of tipped wood shaper cutters are stellite.
As i mentioned about the saw blades, stellite gets sharper, lasts longer, cuts better in most wood than most carbide. It is also ground with AlO wheels. I used to make woodwhacking cutters with brazed carbide teeth. Have gone over to using Stellite because in every category, it is just "better" and does not require cnc or special shaped diamond wheels to grind profiles such as for mouldings.

smt
 
Bob - I use the exact same blades, 1/2" x .025 4tpi Lenox Diemaster II. Had very good luck with them re-sawing up to 22" wide stock, using a Lenox Micronizer to enhance cut quality and blade life. This was back when I had a 36" Tannewitz direct drive saw. Blade speed was way too fast for what I was doing, needed the M42 and lube to get decent blade life. Now using a Powermatic 20", almost half the speed.

I'm curious, why did you reduce rake to 7 deg from 10 deg? The cut doesn't feel too aggressive to me.

I just tried reducing the kerf of the Diemaster blades by squeezing them in my Kurt vise to .037", worked great Could go down to .032", will try that next time if I can get my Micronizer cleaned out and working again. Back in the 70's & 80's I used to touch up my blades with a hand held Dremel, had mixed results. If I had a T & C grinder I'd be tempted to try that again. But I have several 250' coils I bought cheap on ebay a while ago, so might not be worth the effort.

Sometimes it's hard for me to accept my limitations, I'm really just a woodworker with enuf metalworking equipment and experience to get myself in trouble. And sometime out of it too...

I agree with Stephen re Stellite over carbide for wood. I use Tantung in the same way. But I have to say that the high polish, positive rake inserts for aluminum (ccgt etc) work really great for turning wood.
 
Richard,
Reducing the rake to 7€° makes the cut quality so much better, partially as a result of the reduction in self-feeding tendency.

Bob
 
Richard,
Reducing the rake to 7€° makes the cut quality so much better, partially as a result of the reduction in self-feeding tendency.

Bob

I'm getting a great surface now with the stock geometry, .005" cleanup in wide belt sander to remove all traces. Were you getting resonance with the aggressive cut? I found that having the correct tension on the blade made a huge difference, the scales on most saws are useless, need a tension gauge to get it right. I have to bottom out the spring, and then keep cranking on my Powermatic. The Tannewitz was pretty accurate, what a great saw that was!
 
Richard, why not send it out to one of the companies that resharpens carbide bandsaw blades? Tell them what you want and see if they are equipped to do it?
 








 
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