12" Conversion

[Stytooner]

Just thinking about the arbor question....

Wouldn't a fully stacked 8" dado put more strain on the arbor than the added blade tip speed of the 12" blade???

It's biting into a lot of wood and the radial stress has to be maybe 4 fold that of a 10 inch blade ?

I'm not an expert in this area, and am concerned this could be the flaw in my plan...

Thanks!

Dado blades are quite a bit slower at the teeth because they are smaller. They rarely cut very much material either. The outer blades actually does the cutting for the most part and the chippers, well, mostly chip out whats left. Being a smaller blade and cutting shallower depth, a dado would not have the leverage to put much torque on the arbor.
That said, there is much more weight to a fully stacked dado blade, so that in itself does put more stress on an arbor.

It is probably a wash and would work fine, but that is only a guess.
Yes indeed a failed arbor can be life threatening. If one does happen, it can be a very bad day for anyone in the area. Then again, it may get contained within the saw. (Very Lucky) I have only heard a story of an arbor failure once or twice through the years. Don't recall the circumstances or results very well, but I think both were contained in the saw housings.

We had a recent discussion involving a recall on Ridgid R4511's when they first came out. It was for faulty arbors that could perhaps fail.
They did take care of it quickly though.

What about renting one of these?

http://www.ebay.com/itm/Makita-Circular-Beam-Saw-5402A-hand-tools-woodworking-carpenters-construction-/150870279517?pt=LH_DefaultDomain_0&hash=item232091c55d#ht_500wt_1414

[LCHIEN]

Dado blades are quite a bit slower at the teeth because they are smaller. They rarely cut very much material either. The outer blades actually does the cutting for the most part and the chippers, well, mostly chip out whats left. Being a smaller blade and cutting shallower depth, a dado would not have the leverage to put much torque on the arbor.
That said, there is much more weight to a fully stacked dado blade, so that in itself does put more stress on an arbor.

It is probably a wash and would work fine, but that is only a guess.
Yes indeed a failed arbor can be life threatening. If one does happen, it can be a very bad day for anyone in the area. Then again, it may get contained within the saw. (Very Lucky) I have only heard a story of an arbor failure once or twice through the years. Don't recall the circumstances or results very well, but I think both were contained in the saw housings.

We had a recent discussion involving a recall on Ridgid R4511's when they first came out. It was for faulty arbors that could perhaps fail.
They did take care of it quickly though.

What about renting one of these?
http://www.ebay.com/itm/Makita-Circu...#ht_500wt_1414

that's part of the problem, the OP is planning on removing the blade shroud (wont fit), removing the throat plate (won't fit) and cutting slots in the table top. There's less of the saw to protect him.

Having the blade further out on the arbor will increase the moment (F x D) working on the arbor.

[cabinetman]

The saw was designed for a 10" blade. It's not only the tip speed, but the mass that has to spin. In simple terms, the distance from the cutting edge to the arbor is the stresses that saw wasn't designed for.

You might find a local cabinet shop (or lumber yard) with a large table saw, and planer that could do the cutting and dressing. IMO, the wisest (and safest) way to go.

.

[oohhmm]

I've continued on the mods, and have a 12" blade spinning clean on my saw. I was able to save the outer dust shield and only removed the arm for the riving knife to make the room needed for the blade ( + about a square inch of the inner dust deflector). The notch I cut in the table top is but 1/2 " by 1/4" and it clears the blade easily. The depth of cut is now 4 1/4". Photos to be put up soon....

I spoke with a friend who is a mechanical engineer (he designs axles) and posed the changes). He agrees that blade speed is not an issue regardless of the blade diameter. What is relevant is the resistance (or load) encountered by the blade. If a 12" blade is rated to 6000 RPM's it is the arbor speed that matters.

If a 3/4 inch wide dado is set to a 1" depth the resistance on the arbor is the same as a 1/10th inch blade cutting 7.5 inches in depth. the mass of wood is equal. That I am cutting softwood, instead of say, Oak, with the dado only means that the resistance is far less.

The sled is next. I've decided to use 1" 90 degree aluminum for the rails. I'll glue up Kiln dried fir to support the rails. I'll bolt support legs to hold the weight and attach it to the saw with the T bolt system. Again photos to follow..

Over the rails I plan to run the Home Depot butcher block composite pine that is 3/4 inch thick. I will space this with teflon tape and horizontal T-tracks to level the sled to the table top. The T tracks will allow a "fence" to adjust to the width of cut and with a T-track on top of the fence I can use the Kreg clamps to hold the wood at square for the first cut. The fence on the sled will square the reverse cut.

I've invested about $200 total for this and as I have the clamps and T-tracks laying around ( when I'm done I remove what I moved to the 12" saw). There is a local mill here that gave me a quote of $1.50 a board ft to cut my wood down. At 300 board ft that's $450. I will save $250 and the mill would not allow me to "set" the cuts, meaning the loss will be greater than I can do myself. As well the character of the wood and it's edges would be lost to indiscriminate milling. And , I can "mill" the wood as I need it as opposed to all at once...

Coming soon,,, The BT3012 mini mill....

[LCHIEN]

Yup, I'm way out of spec with this and yes safety is my primary concern!

As for the arbor strength. this weekend I pulled the blade from my Dewalt Miter saw I use for chopping up lumber (as in doug fir 2x4's and 4x4's) and found it used an adapter like I was planning on buying - 1" to 5/8". This saw runs at 4000 RPM, is also a 15 amp motor, and unless Ryobi used a lower grade of steel, should have similar strength?

Can you tell me more or point me to the arbor issue Tommy had? Did you mean when you said "but if it does fail, you will likely never know it" that an arbor failure is life threatening and/or seriously dangerous?

The nails and other metal in the wood is easy enough to remove and will be before I run it over the saw (any saw)and I can't get it through my planer until I rip it down to 12"'s


I am indeed fond of all of my members.....

granted the arbor diameter of the miter saw and the Table saw are similar, but the moment is probably much greater on the table saw. This is the distance from the bearing point of support to the point at which the blade is mounted. The MS usually has the bearing just a half inch away from the blade IIRC, and the table saw it may be a couple of inches due to length for dados and for ability to tilt the blade. That gives any off-centering forces over 4 times the moment. The same force acting on the MS blade and the TS blade gives 4 times the torque moment (measured in inch-pounds) trying to break or bend the arbor. Since you propose to hang the blade out further to the left to avoid the motor guide housing, it will be even worse.

Just an engineer's opinion. (but I'm only an electrical engineer)

[cork58]

to bad you don't have a local sawyer that could help.

[sweensdv]

Sometimes we get an idea into our heads and it's full speed ahead with no chance of any other options. IMO, the $200 you already have invested into making your super BT would have been better spent on a used 14" bandsaw. Don't take that as criticism as I like a good Jerry Rig as much as the next guy. On the other hand, a bandsaw would have done what you wanted and so much more in the the long run.

[oohhmm]

I have a great 14" bandsaw and I know my limits with it. I tried it, I wasn't getting the results I wanted.

$50 for the saw, $35 for the blade, $30 for the rails $25 for the sled wood $30 for the wood to support the frame. When I'm done the saw becomes spare parts the blade goes onto my miter saw and the sled becomes a table top in my winery. I'll have "wasted" $60, and most likely I'll find a use for that... Besides I'm having a lot of fun building my "super saw".

I'll send some photos when I'm done, I think it'll all make more sense when it's done.

[oohhmm]

The blade is in it's original position, by taking off the riving arm, it fit and allowed the dust cover to be used. The distance on the BT is about an inch and on my chop about 1/2 inch from bearing to blade stabilizer... Your point is valid, and I go back to the comparison to a dado. I really think this saw will be safe for what I'm doing. Also, with the sled I'll be 18 inches to the right of the blade with a mostly intact saw and 4 inches of wood between me and the blade.

[oohhmm]

It Works!!!!

I'll be posting some photos soon, but, the "mill" works. I used a test piece about 3' long of the 4" redwood. Using the sled I ripped 4" off first just to see how it went. The load seemed fine, no bogging down or stalling and the feed rate was about the same as 2" hardwood. I next took a thin slice of 1/8th " and ended up with a very even slice from leading edge to trailing edge.

Then I cut 3 pieces 1.25" each, again using the sled. I added 2 rulers to the sled (when the photo is up you'll see my rulers) embedded in the sled and covered with acrylic and attached sights made also from acrylic) and just used the rules to set my cut. all three pieces came within .005 of each other with .004 variance across a single board.

Since this stage is but to mill the beams to be ready for work on my table saw, the results are more than just acceptable! AND.... The joints are glue up ready for the work I'm doing with the resulting lumber.

One thing else I did was to use UHMW plastic rails to ride in the aluminum track to avoid binding (and a possible motor burn out). I can propel the sled with a moderate "push" across the length of the track.

Because the dust shroud is intact there is excellent collection and minimal cleanup. The sled mounts and dismounts from the saw with 5-10 minutes of work (mounting to the rails with T-nuts) and it's legs fold up into the rails for easy storage. The total cost with the initial $50 for the BT3000 is under $260 (far less than a saw mill was quoting me, and I can further dimension the wood without losing the 4" thickness, meaning a lot more cuts than those quoted by the mill and a the cost being spread over those cuts...

Thanks for all the thoughts shared by everyone (especially the safety issues) and like I said I'll be putting some photos up in "my photos", so you can see just another example of the versatility of our beloved BT3!!

[oohhmm]

Photos are up

[LCHIEN]

Photos are up

up where???

[oohhmm]

Sorry, in my photos here, I wasn't sure if a link would work ... but try this

http://www.bt3central.com/album.php?albumid=86