Raised Panel router bit with back cutter

[Kuby]

I have a question on the use of a 3 1/2" raised panel router bit with back cutter. The op manual indicates not to use speciality router bits with diameter larger than 2 1/8." I have a Mark 7 and making raised panels on MDF and I have a 3 1/2" raised panel bit with back cutter. Obviously I can't use this bit in "under the table" operation (bc size of insert), but I was going to use it in an "over the table" operation. Before I attempt to use this bit, I am concerned about safety first with this bit on a shopsmith. I guess this is a "no brainer," if the manual stated not to use any bit of this size, I probably should not, and answered my own question, but I am looking for anyone's expertise on this issue. My experience is limited, not a novice, but more towards an intermediate worker. It just seems to me that it is possible to use this 3 1/2/" bit on a Shopsmith "safely", and I am looking for experienced input. Thanks, Kuby

[charlese]

... It just seems to me that it is possible to use this 3 1/2/" bit on a Shopsmith "safely", and I am looking for experienced input. Thanks, Kuby

Why not Call Shopsmith and ask them.?

[sehast]

There are several considerations here. First being above the table just by itself is less safe than below the table but I feel that with the necessary precautions it can be done safely. In my opinion the 2 1/8" warning or restriction is due to the size of the table insert and the limits of the shopsmith router fence. In this case the table insert is not an issue but if the fence is used I think there may be a problem. If a customized fence is used then it should be possible. Check the recommended RPM for the 3 1/2" inch bit but its probably not less than 10,000. Just because it is possible to do does not mean you should do it. A 3 1/2" bit spinning at 10,000 rpm above the table is kind of scary for me. I would have to think a long time about how I would do it safely and ensure no part of my appendages come anywhere close to that bit.

[Kuby]

I called them twice. First time lady stated they don't give advice. Second time lady stated that she meets with a guy from the shop at 130 pm and she never called me back and it's been several days so I gave up on them.

[Gene Howe]

I use a 3 1/2 hp router mounted in a table with the bit buried in the fence with the bearing just kissing the work. And, I use foam covered plaster trowels to guide the panel. Even so, for me, it's scary. What you are proposing just scares the living sh## outta me.
PLEASE don't try it.

[Dccarpenter]

While I haven't used this size bit in a Shopsmith we have used at a commercial shop it in Porter Cable 690 routers and Sears 2 hp routers not infrequently , we just didn't feed too much at a time (two passes I believe). We just used a few 1x blocks with notches as push stick, might have used a feather board but unlikely as it was a bearing guided bit. I know the few times I've done it solo I didn't use a push stick just carful hand placement.

We definitely slowed the routers way down, to about 12500 rpm so not too far off the 10,000 rpm on the Shopsmith.

I wouldn't hesitate in the slightest to run one on a Powerpro (contemplating a speed increaser to do so on my Mark V but I heard on here that they are unreliable so stuck wondering...).

Here are some safety tips, clamp a board on your fence a 32nd or so higher than the thickness of the stock, this will keep it from kicking up. Use a featherboard against the stock, either use a metal bar clamp to attach feather board to fence or through bolt it, it won't go anywhere. Use a push stick for feeding and stand to the side of your feed direction that way even if it overpowered the feather board somehow and shot back it wouldnt harm you. Make your feed nice and smooth , slow but not agonizingly slow just steady.

[benush26]

I think safely is the key concept.
Just for giggles, set up the Mark7 in an overhead position with it set up you think you would use it and with with the bit installed. How much "oops" room do you have? Take the boards and set up the table to see how well or poorly it will handle your largest piece. Is there enough room easily and comfortably?
My guess is no.
I have a Mark 7. I also feel fairly accomplished making things with a router and I would NEVER attempt what you are suggesting. !
Granted, I have router tables and a couple routers, one of which is 3-1/2 HP. So I have the plausible situation of using something other than my Mark 7.
I'm getting too old to believe that taking significant risk is an option. But I'm with Gene completely on this one. I'd be scared to even consider it.
Is it plausible to attempt what you want? Sure. Is it worth the risk? Only you can answer that, however I personally believe the risk is gigantic.
Suggestion.... Do you have a friend or a friend of a friend or even a local high school shop class with the right equipment? There are even co-op woodworking facilities. Maybe explore a few alternatives before deciding the Mark 7 is your method.
The Mark 7 is a very capable machine, but I think there are times when it is best not to push its capabilities past what is safest for the operator.
Just my old fart two cents.

Be well,
Ben

[reible]

In the end this is going to be up to you and how safe you feel about the operation.

First this need not be an above the table operation. For may years people have done what is called a false top. This in the most simple terms is a top that sits on the table that has a cut out to match the size of the bit you are using plus a little.

Next since this has the under cutter you will have to make a pass then move the fence to make a second, third and 4 cut. You can not change the height of the bit.

You will likely have to make a fence with the false top to accommodate this. I can do a quick and dirty sketch to show you the basics of how this would work if you are truly interested in do the project this way. You will have to provide your own details.

Since you can use the false table and get the bit coming from below this is no different then how it would be done on a router table and I would view it as perhaps as safe as a router table.

Perhaps just for completeness I will make a sketch later tonight or tomorrow so we can all learn a possible new idea to some.

Ed

[reible]

I forgot to ask but did you get the dual tilt with the powerpro? If not then you are stuck with this as an above the table operation.

This is a quick sketch of the idea. You might be able to use the movement of the table in and out to do the depth of cut adjustment.

1bb.jpg (108.75 KiB) Viewed 9065 times

You would also need to cover the back of the bit where it might be exposed but this is the general idea.

Ed

[BuckeyeDennis]

I just checked the manual for my big Triton router, that I use undertable on my old-style standalone OPR. It says that if the bit is more than 2-1/2" in diameter, set the speed at 11,000 RPM. It also says you can use the 8,000 RPM setting, if necessary to avoid wood burning. So the PowerPro top speed is right in line with the recommended router speeds.

As for a fence, it seems to me that the Mark 7 (520) fence could be adapted very easily, as it has nice T-slots on both sides, and clamps rock-solidly to the table. I'd glue up a beam about the size of a 4x4, and mill it flat and square. Then I'd cut it in half length-wise, and mount the halves to the side of the fence using T-nuts and recessed bolts. Presto, I've got a jumbo-sized router fence, with adjustable sliding faces, that can completely swallow a 3-1/2" bit. If you glue up a hollow beam for the sliding faces, you can even hook up a dust collector. Depth-of-cut adjustments would be made by moving the fence.

You'd still need Ed's "false top" to space the workpiece such that the router bit clears the table. Simply clamping on a piece of MDF should work fine for that.

Which leaves the question of overtable vs undertable. For the life of me, I can't figure out why it makes any difference, aside from feed direction. Given that the bit has a back cutter, the workpiece is no more "trapped" in one mode than the other. The bit itself is mostly buried in the sliding fence faces, and roughly at the same height above the table in either mode. And what difference does it make which direction the shaft exits the cutter?

As for rigidity, a good undertable router could conceivably have an edge. But I've used the Shopsmith version of the Wagner Safe-T-Planer on my 520, and it handled it with aplomb. I've even used a 6" circle cutter on it (and I did find that a bit scary before I got a speed reducer) but the 520 handled that just fine as well.

Am I missing something?