What’s the type of grind called that will produce a flat bottomed kerf? I’m tooling up to do a series of finger joints and all the blades I have are alternate top bevel (ATB) or triple chip such that I don’t get a true flat bottom on the kerf.
Or am I dreaming?
………..
From Beautiful Skagit Co. Wa.
Dennis
From Beautiful Skagit Co. Wa.
Dennis
Replies
For some reason, chisel tipped comes to mind. So the fingers are going to be really small, right? Not much margin for error that way. Good luck.
You're not dreaming Dennis. You're looking for a rip pattern blade that has flat top grind (FT) teeth. There will usually only be about 24 teeth on the rim of a 10" diameter blade. This leaves large gullets between the teeth able to carry away the curly shavings created by the cutting action of the teeth. As is implicit in the name, this type of sawblade is designed specifically for efficient cutting with the grain. Slainte.
Dennis,
Here's an example of what you need: http://www.freudtools.com/woodworkers/rep/sawblades/Industrial_Series/Ripping/html/Ripping_2.html
Are you making finger joints the exact width of the blade?
Regards,
Bill Arnold - Custom Woodcrafting
Food for Thought: The Ark was built by amateurs; the Titanic by professionals.
I've got a Freud flat tooth ripping blade that leaves a flat bottom kerf. They're pretty aggressive and tend to splinter the ends a bit more...perhaps a higher tooth count would remedy this, but as previously stated a FT grind is typically found on a 24T blade. Most sharpening services should be able to grind any blade you want to a flat tooth.
It's called a flat top grind, you'll find it on ripping blades.
John W.
Thanks for all the quick replies ... Flat bottom kerf = FT (Flat Top) grind ... Duhhhh! Good morning, Dennis (grin)
Yes, the fingers will be a saw-kerf wide. Very small jewelry box for grandaughter. Spalted maple, top tray and a small drawer at the bottom. Not sure if the material will mill well with an agressive low tooth count blade but wll try. Option is to make a little sanding stick and sand the bottoms of the kerfs slightly to get rid of the small ridge. Ain't much but sure does show when the pieces are assembled.
Thanks again.
From Beautiful Skagit Co. Wa.
Dennis
Dennis,
You could have a small diameter blade with a higher tooth count ground to a flat top pattern. A 6 inch, 36 tooth blade would cost far less than a 10 inch blade which would need 60 teeth to be as fine. A smaller diameter blade will also give you a better cut in this situation, but you will still need a zero clearance slot in the fence to help prevent tear out.
Get in touch with Forrest, I'm fairly sure they will make a custom ground blade for about the same cost as a standard grind blade of the same size. They may already stock what you need.
Trying to sand the bottom of the kerfs flat will create more problems than it will solve. This can also be done with a straight bit in a router table, using a jig similar to the fence jig for finger jointing on a table saw.
John W.
The low tooth count shouldn't be a problem, just go slowly. What you need to worry about is chipping out the back. Be sure to use a piece of scrap behind your work as you pass it over the blade.
For fingers that small, why not use a 1/8" bit in a table router? That will give you a flat bottom with a bit that's cheap.Bill Arnold - Custom Woodcrafting
Food for Thought: The Ark was built by amateurs; the Titanic by professionals.
Another way to hide the bottom of the cut it by veneering over the sides and/or front or inlaying something decorative along the line. Since the fingers are as small as they are, you may want to do a test cut with a good, sharp triple chip blade to see if it's acceptable. Otherwise, you could file the bottoms instead of sanding. All you would need to do is barely knock off the fillets in the corners. If you try it and have tearout, you can make them thicker than the finished dimension and remove that with a wide belt sander, jointer, scraper or plane.What about a sliding dovetail for the front and finger joints for the back corners? "I cut this piece four times and it's still too short."Edited 12/6/2004 2:13 pm ET by highfigh
Edited 12/6/2004 2:13 pm ET by highfigh
I ordered one from Forest Saw Blades. Its not in their catalogue but they new exactly what I wanted. Almost no splintering just like Woodworker II.You get out of life what you put into it......minus taxes.
Marv
Dennis,I have a Freud ripping blade for exactly this purpose. Spline miters in the corners of picture frames and boxes to be exact.I have the LM72M008. This is an 8" blade which I use in my 10" table saw. It's less expensive than a 10" blade as I have no need for the full diameter in this application.This is a full width kerf (0.125") blade, 24 tooth, FG, carbide. It cuts absolutely clean, flat bottom kerfs with no splintering or chip out whatsoever. I believe it was about $50.Rich
A ripping blade will tear the crap out of the back of your board.
Another blade that makes a flat bottom is the 50-tooth Combination blade. It has 10 groups of 4 ATB tips and one flat top raker tip. This blade will give a much better cut than a ripping blade.
Dave,
Most combination blades that include flat grind teeth with alternate bevel teeth don't leave a perfectly flat bottomed kerf because the beveled teeth are ground to be slightly higher than the top of the flat teeth. You wind up with a kerf with two small notches and a flat area between them. This is done to reduce tear out from the flat grind teeth.
John W.
What model of blade is it and what did it cost? Speaking of Forrest blades, do any of you use their sharpening service or do it locally? I used theirs and I think it was worth it. What do you do for router bit/shaper cutter sharpening?
"I cut this piece four times and it's still too short."
What model of blade is it and what did it cost? Speaking of Forrest blades, do any of you use their sharpening service or do it locally?
It had no model, I just told the salesman what I wanted (I think the ten inch blade was about $80). Sharpening.....What's that? I bought two Woodworder II blades two years ago and use them on my Grizzly table saw and Makita chop saw. I work on weekends. I've never had to sharpen them! To look at them, I can see no wear! I'm tempted to send them in to be touched up but they may just send them back without doing anything! They outlasted my old blades by 5 times!You get out of life what you put into it......minus taxes.
Marv
I know how it is. I have a Woodworker ll and finally sent it in last fall after 10 years. I think it cost $28 with shipping. When I put it back on and made the first cut, it was a piece of hard maple and I remembered why I bought it. I have an Oldham for cutting particle board, melamine coated PB, MDF and whenever I think there may be metal in the wood. The Oldham is OK, but it took 4 blades to find one with a flat blank so it didn't wobble. First time I handled the Forrest after taking it out of the package, I cut my finger and didn't even know about it till it felt a bit sticky. That was weird.
"I cut this piece four times and it's still too short."
cut my finger and didn't even know about it
I gues my blades must need sharpening because they won't do this.You get out of life what you put into it......minus taxes.
Marv
Yeah, I was pretty surprised to see it bleeding. I didn't even remember checking it to see how sharp it was and this was just holding it in my hands. The first thing I cut was a piece of 2-1/2" thick cherry and cut off a strip less than 1/16" thick. The surface was amazingly smooth. Still is. Definitely worth the money.
"I cut this piece four times and it's still too short."
It is still a better choice than a rip blade, for what he wants to do. The amount of 'tip' is barely noticable with a good quality blade.
Actually, Dave, I tried a triple chip blade and there's an ever so slight divot at the bottom of the kerf that showed.But .... dug a little deeper in my blade cabinet and found a comination blade with a fairly high tooth count and .... flat topped grind! Cut a beautiful flat bottom kerf. But -This blade was way too thin, even for this small box. So tried a trick I read in one of Master Frid's books .... added a thin shim under one side of the blade against the arbor flange. Pretty high pucker factor when I first switched on the saw but - got a nice 3/16" groove as a result. I don't know if this is accepted practice and (for obvious insurance reasons! -haha-) I don't suggest anyone trying it.Box is well on the way to being (half) finished. Thanks for your replies............
From Beautiful Skagit Co. Wa.
Dennis
Yeah, full thickness(1/8") combo is the way to go, what you did with the shim is the same principle as the "dial in" dado blades sold by Sears and others. Not a true flat bottom though, but at 3/16". I doubt you could see the diffrernce.
Systimatic rip blades:
http://www.justsawblades.com/systimatic/rip.htm
Note that they offer a TC grind for ripping, it doesn't produce a flat bottomed dado cut. They do offer a flat top grind on their heavy duty rip blades.
I've used Systimatic blades for about eleven years now, no complaints at all.
I am not sure. But wouldn't a blade from a stackable dado set work?
CircleKid ....One blade was too thin a kerf. I really should have used both the inside and outside blades from my dado stack for these fingers. I'm not quite up to working with such tight tolerances and small detail yet! (grin).Oh-well, grandaughters think everything grampa does is wonderful, don't they?...........
From Beautiful Skagit Co. Wa.
Dennis
OK, got back to focusing on this micro finger joint project and went through my entire arsenal of saw blades. The only one I have that cuts a really, I mean really flat bottom is, of all things, a stock Makita blade that came on an old chop saw I bought years ago. It really does cut a flat bottom kerf.
Charles (from Freud) - I do have the Freud "glue line rip" blade. It leaves a just barely perceptible deeper cut at the bottom center of the kerf. There's one batch of teeth that are ground in what I can best describe as a truncated triangle - that is the two sides slope in a bit. Sorry to be such a dunce but are these what you in the saw blade business refer to as 'raker' teeth? If so, those are the teeth that cut about 1/64" deeper than the rest.
On to bigger and better questions - For Charles again:
I read the ad for the new Freud "Box Joint" blade set in the latest issue of FFW. The question is, can the blades be used individually to cut even smaller joints than they would in combination? If that's the case, do you know what the width of the teeth are on the individual blades? This set will be a must-have for me if they can be used individually and cut a 1/8" or very close to it kerf.
Thanks, Charles.
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