Need 1/8 blade for incremental box joint jig ??

[Benjimin Young]

I had a fun weekend building an increment box joint jig that relies on a threaded rod 16 tpi so 2 turns = 1/8. https://www.youtube.com/watch?v=JYxDXHGRRrk
I am now on a quest to buy a good 8" or 10" 1/8" blade that will prodice a good flat bottom finish but minimize tear out. .125 kerf FTG. I see there are box joint sets that do 1/4" and 3/8" but they are pricy.

Thoughts? Suggestions?

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[John TenEyck]

Why not just use a good quality, full kerf ripping blade? You may have to get it resharpened to be exactly 0.125" width, but that doesn't cost much. This Freud is really close at 0.126" kerf: http://www.freudtools.com/index.php/products/product/LM72M010 You need a backer board to prevent tearout so as long as the blade you choose cuts smoothly it should work fine.

John

[Lee Schierer]

The Freud LU84M010 has 50 teeth arranged in groups of five, each of which includes one flat-top raker tooth for fast, accurate ripping. Each flat tooth is followed by four alternating-top-bevel (ATB) teeth that are particularly well suited to crosscutting, and large gullets between the teeth ensure effective chip clearance. The kerf is .126, which should be ideal for your box joints. Remember a 1/8" finger will not fit in a 1/8" slot, you need a slight amount of clearance.

[Cary Falk]

The Freud LU84M010 has 50 teeth arranged in groups of five, each of which includes one flat-top raker tooth for fast, accurate ripping. Each flat tooth is followed by four alternating-top-bevel (ATB) teeth that are particularly well suited to crosscutting, and large gullets between the teeth ensure effective chip clearance. The kerf is .126, which should be ideal for your box joints. Remember a 1/8" finger will not fit in a 1/8" slot, you need a slight amount of clearance.

All the teeth need to have a FTG or you will get lines from the ATB teeth. Any full kerf FTG will work. You will probably need a backer board because of the lesser number of teeth.

[glenn bradley]

Plenty out there:

20 Tooth -

http://www.carbideprocessors.com/safety-rip-saw-blade-10-dia-20t-130-kerf-5-8-arbor-worlds-best-37376/

24 Tooth -

http://www.carbideprocessors.com/worlds-best-37208-gang-rip-and-straightline-rip-saw-blades/

[glenn bradley]

On the cheaper side:

https://www.amazon.com/Freud-Tooth-PermaShield-Coating-LM72R010/dp/B0000225UD

[scott spencer]

ATB/R and TCG won't leave a truly flat bottom because the non-flat teeth protrude above the flat raker teeth. A flat top grind (FTG) is the only grind that will leave a truly flat kerf. Those are mainly rip blades like the Freud LM72, Infinity 010-024, CMT 210.024.10 in the $50-$60 range. For less money, the Delta Industrial 35-611 (http://www.ebay.com/itm/Delta-10-x-18-FT-Grind-Carbide-Saw-Blade-35-611-/390105614825?hash=item5ad41b49e9:g:GA4AAOSw4SlV7uE F) is made in Germany by Leitz, and should do an admirable job for ~ $30 to your door.

[glenn bradley]

Thanks Scott!!! I corrected the links.

[Dick Mahany]

I have had excellent results with a 40 tooth Forrest WWII blade with their "No. 1 grind" which is a true flat top grind. Cuts super clean. Down side is it is a relatively expensive blade. Leaves a perfectly flat bottom as seen on this Doug Stowe inspired jewelry box.
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[Edwin Santos]

Why not just use a good quality, full kerf ripping blade? You may have to get it resharpened to be exactly 0.125" width, but that doesn't cost much. This Freud is really close at 0.126" kerf: http://www.freudtools.com/index.php/products/product/LM72M010 You need a backer board to prevent tearout so as long as the blade you choose cuts smoothly it should work fine.

John

I just ordered this same blade for a similar purpose as well as for cutting clean shoulders on dovetail joint tail boards (recent FWW article talks about this technique). There is a seller on Ebay selling this blade at a very low price, under $40 new. Like John notes, the kerf is .126. Not sure if .001 makes a difference for you. From what I know about the incremental screw drive jigs, it shouldn't.

[Kevin Groenke]

We have had good luck with this blade for box joints. A backer board eliminates tearout that you will otherwise probably get with any FTG blade.

https://www.amazon.com/Kempston-99312-10-Inch-Industrial-8-Inch/dp/B0013KTUQ6/

[Wayne Jolly]

+1 on the Forrest Custom #1. I bought one at a woodworking show a few years ago ad it is one sweet blade. Very clean cuts with perfectly flat bottom kerfs.


Wayne

[Raymond Seward]

+1 on the Forrest Custom #1. I bought one at a woodworking show a few years ago ad it is one sweet blade. Very clean cuts with perfectly flat bottom kerfs.


Wayne

+2 I use mine a lot. It is price but top notch....actually I have switched to all Forrest blades...I've tried them all but now stick with Forrest

[Alan Schaffter]

Just remember, with an incremental box joint jig, the blade width/kerf created must be a perfect, whole number multiple of the pitch of the leadscrew (typically, a multiple of 1/32" or 1/16" for standard hardware store all-thread.) The tolerance is pretty tight, too, just a couple of thou. If it is off by as little as .003" you won't get a good joint. Also, the all-thread and follower (nut) must fit together well, it is best if they have close tolerance threads, to limit backlash (engineering). Compensating with fractional revolutions of the crank can be a real nightmare to track.

As an unabashed self-promotion- the INCRA I-BOX doesn't have this problem- you set it to the width of the blade kerf, whatever it is (the jig doesn't care), by direct transfer (no calipers or measuring of any kind).

[Benjimin Young]

An update to my quest for a 1/8” kerf FTG finish blade that will work with my newly built 1/16" incremental jig.
First off, thanks to all for the great responses, some great advice there. Here is what I have tried so far and the results. Hopefully, other can learn from my fun.

I have a few different Freud blades but did not have a 1/8” kerf FTG. So when I built the jig I tried the 1/8 kerf ATM Freud blade and got tight joints but as expected bottoms are not clean.,
I concluded that a 1/8 kerf would work but needed to find a FTG, hence this thread.
I took all the great advise and set out to find one but options were limited so I waited for the wood working show.
At the Hamilton wood working show last weekend I spoke with the Freud rep and purchased a Freud LM72R010 FTG heavy duty rip 1/8 kerf 24T 20 hook. I also purchased the Freud SBOX8 two blade set that does 1/4 or 3/8, great price at $99 CND.

Back at my shop several tests with my new 1/8 kerf FTG Freud rip blade produced very disappointing results with very sloppy joints even with just 1/8” keys. Just for fun I checked the slop with a feeler gauge, .011 slop with .012 to .013 just getting tight.

I now suspected my saw so I did a complete check of alignment - vertically over 360 degrees the blade is bang on, over the length of the blade at full height the blade has .003 runout in relation to the table slots.

Then I remembered the first test I did so I repeated it (the Freud 1/8 ATM plywood blade) and it resulted in tight joints again albeit with bad bottoms

Next I setup the new SBOX8 Freud box joint set at 1/4" and got great tight joints.

Conclusion, I am now wondering if a FTG blade designed for ripping is never made to kerf spec tolerance suitable for my purpose, in which case it is luck of the purchase.
Or, is the LM72R010 blade I purchase not made to Freud spec, aka defective ?. I will ask the vendor if I can return it.

So, I will continue to use the Freud BOX joint blade set, very nice, and do box joint 1/4" or larger keys. If I want to do 1/8 keys I may try again for a different 1/8 kerf blade but only if I can return the one I bought at the wood show (budget blown for now ;-).
Happy woodcuttingJ

[glenn bradley]

Conclusion, I am now wondering if a FTG blade designed for ripping is never made to kerf spec tolerance suitable for my purpose, in which case it is luck of the purchase.

I just have Carbide Processors make all my blades to .125" kerf. The cost difference for custom is insignificant and all my jigs and accessories always line up and my fence is always correct. I guess I should have just mentioned that instead of pointing you at links but, I didn't want to sound like an advertisement. No affiliation, just a satisfied customer.

[Bill Adamsen]

... Conclusion, I am now wondering if a FTG blade designed for ripping is never made to kerf spec tolerance suitable for my purpose, in which case it is luck of the purchase.


Why not just use a good quality, full kerf ripping blade? You may have to get it resharpened to be exactly 0.125" width, but that doesn't cost much.

As John mentioned, you'd probably have to get the rip blade resharpened to get an accurate width. Though I am a little surprised it varies. I have had narrow rip blades that oscillate (not sure if that's the right term) and could produce inconsistent results. Not sure if that is something that is fixable, but some folks here seem to be getting satisfactory results.

Thanks for starting the thread because this is something I've had an interest in so I am watching closely.

[Alan Schaffter]

Just remember, to verify the setup of your SBOX8 (or any stacked dado blade), always measure the kerf that it makes. Do not rely on the manufacturer's published sizes (chippers + trimmers + shims)- Forrest grinds theirs slightly undersized. Also, do not attempt to measure the thickness (tip to tip) of the blade stack with calipers, the thickness may vary at different points around the blade and can be very hard to do accurately. And, of course, a slightly warped blade, a single, random carbide tooth that is wider than the others, or arbor runout will all affect the measurement and kerf width.

Of course, all this is totally unnecessary with an I-BOX. While the I-BOX's published range of finger sizes is 1/8" to 3/4", it will actually cut fingers that are slightly wider than 3/4" and thinner than 1/8" though this is not recommended. As an experiment, I enlarged the cutout in a pre-production I-BOX fence and was able to make 1-1/8" super wide fingers with a dado bit! I don't remember the absolute working minimum, but according to the I-BOX engineering drawings, the critical measurement of the pin plates is .090." The finger width must be wider to ensure adequate clearance between the blade and the pin plates, however. Typical thin kerf blades make a kerf somewhere around 3/32" (.09375") so I would think if you don't have runout and feed the stock very carefully, you might be able to use a thin kerf blade with the I-BOX, though, again, this is not recommended, since blade-to-pin plate clearance would be a very slim .00375"!

With respect to flat bottoms, as you know, you can buy flat grind blades. Also, Forrest will re-grind any one of their blades (and other brands?) with flat tops. While the feed rate and resulting production rate may be slower and you'll need a good backer board to prevent blowout and splintering, router bits do a better job making finger joints, if your jig will work on a router table.

[Alan Lightstone]

Personally, I use the same Freud BOX joint blade set with Alan's iBox, and it makes phenomenal joints. The blade has been great, over many usages.

I'd see if you can return the other blade.

[Lee Schierer]

Check out the Freud 10 In. 30 Tooth Glue Line Ripping Saw Blade with 5/8 In. Arbor (LM74R010). According to the specs the teeth are 1/8" and every other tooth is FTG. I doubt you would notice the bevel teeth in between. This blade is ~$63 from Amazon.

[Benjimin Young]

koodos to the vendor!! I returned the 1/8 blade and after a bit of measurement with their calipers they happily took back the blade and gave me a refund. It just goes to show that it pays to buy a brand you can trust and at a reputable vendor.

My Freud box joint blade set continues to work great on my incremental jig, I just have to get better at counting turns LOL. :-)

[Jim Tobias]

Another +1 on the Forrest 1/8" FT. I use it to cut flatbottom splines and it does a perfect job.

Jim