Is this Safe

3818 Views 23 Replies 9 Participants Last post by OBG65, Feb 13, 2019

OBG65

Discussion Starter · Feb 3, 2019

2

I'm building a router table based on the Pat Warner's design as shown in his "The Router Table CD." I'll have the same type of mortice and tenons to attach the rails to the legs and use the same technique (MDF lifts as in the pictures). My concern is that 4 of the mortices that are on the face of the legs (2 for the top rails and 2 for the bottom rails) are away from the fence, while the other 4 are on the edge. The ones on the edge are ok. It's the ones on the face that is my concern. They will be 1-3/8" away from the fence. The ones closest to the fence are only 1/2" away. Is it safe to cut the ones on the face away from the fence a safe thing to do? I've read about not trapping the work between the fence and the cutter but I'm not sure if it applies only to cutting on the edge of the piece but also to slots. I have his acrylic morticer which I could make the face mortices without a problem.

Thanks for the advice.

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Cherryville Chuck

· #2 · Feb 3, 2019

I'm afraid I can't visualize what you mean Orlando.

OBG65

Discussion Starter · #3 · Feb 3, 2019

Chuck, look at the second picture and look at the mortice on the face of the stick. If you lay the stick flat, the mortice was cut with the majority of the stick against the fence. Is this considered trapping the work between the cutter and the work piece or is it a safe operation.

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Herb Stoops

· #4 · Feb 3, 2019

I am not sure how you are going to make a mortise with that bit, it looks like the bearing is larger diameter than the cutter. If the bearing is removed cutting that much material at one pass is risky too. At times it is OK to feed from left to right if the material is trapped against the fence, because you will be feeding the material against the rotation of the bit. I would use some feather boards too and make incremental cuts.
Herb

OBG65

Discussion Starter · #5 · Feb 3, 2019

Herb, that thing sticking up is a shoulder bolt that prevents the MDF from slipping. The cutter is a 3/8" diameter with a 1-1/4" flute length and is under the stick. The depth of cut is 1-1/4" done in 1/4" increments by removing one of the 1/4" lifts as you go. So in the picture only 1/4" of the bit is exposed since there four 1/4" lifts still in the table.

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Cherryville Chuck

· #6 · Feb 3, 2019

Trapping is when the bit is on the other side of the board from the fence. What can make this dangerous is that with a straight bit there is nothing to control how much wood the bit is feeding into. The board can get pulled by the bit action away from the fence and you lose control. With the bit at least partially behind the fence face depth of cut is controlled. If you are trying to make a slotted mortise into the face of the fence then I would clamp a stop on the fence and hold the end of the board against it and swing the other end of the board into the fence. You'd be able to stay in control that way.

jj777746

· #7 · Feb 3, 2019

@OBG65.Did you mean"trapping the work piece between the cutter & the fence?"Raising the bit in 1/4inch increments as you are doing & taking your time is fine as I see it.

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OBG65

Discussion Starter · #8 · Feb 3, 2019

Chuck, it's not a slotted mortice but one like in the picture.
jj - thanks for the input and advice.

Herb Stoops

· #9 · Feb 4, 2019

OBG65 said:
Herb, that thing sticking up is a shoulder bolt that prevents the MDF from slipping. The cutter is a 3/8" diameter with a 1-1/4" flute length and is under the stick. The depth of cut is 1-1/4" done in 1/4" increments by removing one of the 1/4" lifts as you go. So in the picture only 1/4" of the bit is exposed since there four 1/4" lifts still in the table.

Thanks for clarifying. I have never seen or used that type of operation with removing layers of boards to set depth of cuts.
HErb

OBG65

Discussion Starter · #10 · Feb 4, 2019

Herb Stoops said:
Thanks for clarifying. I have never seen or used that type of operation with removing layers of boards to set depth of cuts.
HErb

My pleasure. It's something I got from Pat Warner's books. His rationale was that instead of making a number of height adjustments (mostly going up) to arrive at your desired depth, you could arrive at your desired depth without making height adjustments by setting the cutter height at the depth you want, having a series of lifts, and remove one at a time. I would surmise that the thickness is arbitrary anywhere from 1/4" - 3/4" and possibly even mix-matching them. He used MDF and in one book I saw them out of acrylic which probably provides more thickness options than MDF, is flatter, and more durable.

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DesertRatTom

· #11 · Feb 4, 2019 (Edited)

Interesting method, that's for sure. The bit height remains set at the depth of cut, but by peeling back layer by layer, only the end of the bit is cutting, which should greatly reduce the stress on the bit. I think I'd want some sort of vertical support on the edges of the removable pieces so they won't shift, but still can be removed. Seems pretty clever to me. I don't really think the piece is trapped using this method, but I would use some sort of push block to feed the piece through, just to play it safe. The bold is an interesting approach to keeping the workpiece lined up, but I'd rather see a custom made featherboard instead. Perhaps the featherboard could be added to the top layer, then remove the next layer down each pass.

This could easily be done with a table saw.

DaninVan

· #12 · Feb 4, 2019

"This could easily be done with a table saw"
-Tom
Yes. My preference.

sreilly

· #13 · Feb 4, 2019

OBG65 said:
My pleasure. It's something I got from Pat Warner's books. His rationale was that instead of making a number of height adjustments (mostly going up) to arrive at your desired depth, you could arrive at your desired depth without making height adjustments by setting the cutter height at the depth you want, having a series of lifts, and remove one at a time. I would surmise that the thickness is arbitrary anywhere from 1/4" - 3/4" and possibly even mix-matching them. He used MDF and in one book I saw them out of acrylic which probably provides more thickness options than MDF, is flatter, and more durable.

I have seen this technique in another instructional video where the instructor took 1/8" pieces of stacked brown board to incrementally increase the depth of cut on each pass bu removing one, make the cut, remove again, and so on till all the boards were removed. This allowed the accuracy of a one time bit height being set without a bunch of adjustments. Actually made very good sense especially for those without router lifts with excellent repeatability. Even with repeatability it makes sense to make one height adjustment and work your way down. I can't locate that video but it's on Fine Woodworking's site and by Bob Van ****.

Cherryville Chuck

· #14 · Feb 4, 2019

There's nothing particularly dangerous about slotting the ends of the boards like you show as long as you can maintain a good grip on the board and keep it tight against the fence. In the interest of extra safety and for accuracy I might clamp a board onto the table that traps the work piece between two fences essentially. That combined with a stop would give identical results every time.

DesertRatTom

· #15 · Feb 4, 2019

2

DaninVan said:
"This could easily be done with a table saw"
-Tom
Yes. My preference.

For 1/4 or less width groove, you could use a 1/8th flat tooth rip blade (GlueLine comes to mind) on the table saw. Line the cutters up to cut one side, flip the piece and then cut the second side.

For wider than 1/4, you could use that Freud blade the cuts either 1/4 or 3/8ths. Same process, just a wider cut. Since it's for cutting box joints, it will cut a flat bottom.

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Cherryville Chuck

· #16 · Feb 4, 2019

He's not cutting a groove Tom. It's the mortise shown in his 2nd picture. It has to have a square end not an arc. If he was making a saddle joint he could stand the board on end and then use that blade or a dado. The picture says it all. His written description is what confused me. It sounded like he was mortising into the face of the board where we couldn't see.

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TenGees

· #17 · Feb 4, 2019

Orlando I recently posted this it could be of help in your situation.

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DesertRatTom

· #18 · Feb 4, 2019

Cherryville Chuck said:
The written description is what confused me.

Thanks, the method seems good and safe to me.

Nickp

· #19 · Feb 4, 2019 (Edited)

OBG65 said:
I'm building a router table based on the Pat Warner's design as shown in his "The Router Table CD." I'll have the same type of mortice and tenons to attach the rails to the legs and use the same technique (MDF lifts as in the pictures). My concern is that 4 of the mortices that are on the face of the legs (2 for the top rails and 2 for the bottom rails) are away from the fence, while the other 4 are on the edge. The ones on the edge are ok. It's the ones on the face that is my concern. They will be 1-3/8" away from the fence. The ones closest to the fence are only 1/2" away. Is it safe to cut the ones on the face away from the fence a safe thing to do? I've read about not trapping the work between the fence and the cutter but I'm not sure if it applies only to cutting on the edge of the piece but also to slots. I have his acrylic morticer which I could make the face mortices without a problem.

Thanks for the advice.

Regardless of how much wood is on the fence side of the bit keep in mind that the side of the cutter away from the fence is pushing the wood away as it cuts while the side of the cutter facing the fence is pulling the wood as it cuts. As you pull the piece back out, you stand the chance of the piece being pulled away from you. As long as you keep this in mind, what you are doing is no different than cutting a stopped slot or anything like it. Sort of like pushing a chain saw into a tree nose first...just keep control...

This is the reason for maintaining control with as many aids as are comfortable. Don't use anything that will get in the way, for example, a featherboard that will not let you lift the piece up and away or back out.

OBG65

Discussion Starter · #20 · Feb 5, 2019

Guys, thanks for all the help and advice. Greatly appreciated.
TenGees, thanks for the link and it is very informative and on point.

Nick what you said is one of the reasons I'm considering doing that cut on a mortice jig.

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