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Assembly/outfeed table design

by JakeK
posted 10-14-2016 03:05 PM


33 replies so far

View JBrow's profile

JBrow

1366 posts in 1061 days


#1 posted 10-16-2016 03:16 AM

JakeK,

If I understand your design, the cabinet will be 96” long and 48” wide with a ¾” sheet of plywood for a bottom. A vertical ¾” plywood spline centered on the bottom running from one end to the other provides center support of the bottom. Drawers would be located on each face of the cabinet (six drawer bays in all). I am guessing that the drawers will be on drawer slides mounted to the drawer bay dividing plywood panels. The leveling castors will afford mobility and can be adjusted to ensure that all four corners of the cabinet will rest firmly on an uneven floor when in stationary mode.

Based on this understanding, yours looks like a good well thought out design. The only potential issue I could foresee is that the bottom could possibly sag a bit putting strain the joinery used to connect the dividers to the bottom and the center spine, especially with drawers loaded down with contents. Any sagging of the front and back faces of the cabinet could add some stress to the long sides of the torsion box. If a face frame is added, support to the bottom and dividers would be added and center castors could be avoided. Otherwise the center supporting leveling castors would add center the support needed and would be a good idea.

I would also think that when shopping for castors, ensuring together they will support up to a 1000 pounds could avoid headaches down the road. I figure that with the weight of the cabinet and torsion box top, drawer contents, and a pile of lumber or a project setting on the top could approach 1000 pounds. Lighter duty castors whose load rating is exceeded can develop a flat spot on the tires. Light duty castors can also make a heavy table difficult to roll around.

If you build the torsion box top so that it features an overhang over the base, workpieces could be clamped to the top. I would think an overhang of perhaps an 1-1/2” would offer sufficient bite for the clamps while still allowing good access to drawer contents.

View Harry's profile

Harry

80 posts in 1321 days


#2 posted 10-16-2016 06:50 AM

I built a table a while back and was going to make removable cabinets but have since decided that the space underneath comes in handy when changing projects. Here is what I ended up with.

-- Harry - Professional amateur

View muleskinner's profile

muleskinner

897 posts in 2578 days


#3 posted 10-16-2016 02:06 PM

I would think if you use a single piece of plywood down the middle for the divider between the front and back, you shouldn’t have any concern over sagging.

-- Visualize whirled peas

View JakeK's profile

JakeK

48 posts in 821 days


#4 posted 10-16-2016 08:32 PM

Thanks for the replies guys. These are the casters i was thinking of using. They would rest on pads when stationary. http://www.woodcraft.com/product/149511/woodriver-machine-leveling-caster-plate-mounted-4-pack.aspx. i’m thinking 6 will be the way to go.

Not sure if you can tell from the pictures, but my design had the 4 short panels as a single panel an the one that goes the long way dado’d into each of those. So in other words there isnt a single long divider going the long way. My thought was for building purposes it’d be easier to have 4 identical panels that go the short way and with glue and screws it’d be just as strong this way. let me know if you disagree.

Harry, i like how you made your torsion box. I was thinking of doing the same thing with lap joints. What did you mean when you said that the underneath was handy when changing projects? My thinking was with drawers down there i could keep the tools for layout and assembly. Nail guns, nails, squares, glue, screws, tape measures, double stick tape, cordless tools, domino/biscuit joiner, hammers, etc. I am a bit worried though about how heavy this thing will be.

I was kind of hoping to get the best of all worlds with this thing and incorporate dog holes and some sort of vice but maybe i’m better off building a separate work bench for those things.

View Harry's profile

Harry

80 posts in 1321 days


#5 posted 10-16-2016 09:30 PM



Harry, i like how you made your torsion box. I was thinking of doing the same thing with lap joints. What did you mean when you said that the underneath was handy when changing projects? My thinking was with drawers down there i could keep the tools for layout and assembly. Nail guns, nails, squares, glue, screws, tape measures, double stick tape, cordless tools, domino/biscuit joiner, hammers, etc. I am a bit worried though about how heavy this thing will be.

I was kind of hoping to get the best of all worlds with this thing and incorporate dog holes and some sort of vice but maybe i m better off building a separate work bench for those things.

- JakeK

Jake, I fully intended to make storage cabinets for my table but I have two reasons why I am not going too. First off, this thing weighs in at right around 700lbs, with cabinets that would put it at 1000 or so. I like having the open room for parts as I am building or whatever underneath in one place. All my tools are on wheels as I tend to jump around to different projects in our studio. When I get back to it, most everything is in one place on or under the table. Works really well for a guy that can make a real mess of the shop. Good luck with your build!

-- Harry - Professional amateur

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JakeK

48 posts in 821 days


#6 posted 10-18-2016 03:44 AM

Harry, on your torsion box, what size did you make the grids? as in each square’s dimensions. Also what method did you use for creating the dado’s in the slats? Did you gang up a bunch and run them through together? Did you use an indexing pin of some sort on a sled or miter gauge?

Are the outside rails of the torsion box also 1/2” MDF or are they 3/4”?

I’m thinking of putting in 3/4” dog holes centered in the grids so I can use the festool or bessey quick clamps to hold things down. Also considering making the cabinet smaller so the torsion box can hang over the edge enough to accommodate a face vise. If I would put in a face vise I would beef up the torsion box in the area where the vise would mount. Anybody have any thoughts about either of those ideas?

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DirtyMike

637 posts in 1043 days


#7 posted 10-18-2016 03:50 AM

109 dollars for casters huh? For an outfeed table?

View JakeK's profile

JakeK

48 posts in 821 days


#8 posted 10-18-2016 04:01 AM

Yeah they’re a bit spendy and i wouldnt buy them to go onto my current outfeed table that is constructed of 2×4’s and CDX plywood but this is more than an outfeed table. This is a rolling cabinet that also serves as an assembly table and outfeed table. I posted this here for feedback so if you know of a cheaper alternative that can support this weight and the wheels wont develop flat spots, i’d be interested.

View Harry's profile

Harry

80 posts in 1321 days


#9 posted 10-18-2016 04:28 AM

Jake, the grids are 6” x 6” and the outer rails were 3/4” just because I had extra. Bottom is the 1/2” MDF that was used to build the box on and the top is 3/4”. I cut the dado’s with a simple jig with an indexing pin attached to my miter gauge. Just did one at a time, real easy. I was thinking of also adding a few dog holes in mine as well. I traced the grid on the bottom so I could find the center of the grids. I think my top hangs over about 4”.

-- Harry - Professional amateur

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daddywoofdawg

1028 posts in 1716 days


#10 posted 10-18-2016 05:21 AM

something I want to put into my next out feed table,is crosscut sled,jig and accessory storage.and a bin to store cut-offs.

View clin's profile

clin

927 posts in 1137 days


#11 posted 10-18-2016 05:43 AM

Concerning the basic design, I think it is sound. If you look at it, with the internal panel running the length and the cross panels, the entire thing is forming a torsion box. The key to that being strong and rigid is the panels being well attached to the “skins” (bottom panel and top pieces).

In this case the bottom is a full skin. The key to it not sagging is making sure the joint between the internal panels and the bottom are very secure. A simple glue in a dado may not be enough. The joint is actually in shear and compression (which is helpful). It’s just my concern that there may not be enough glue surface. If you could glue some addition strips into the corner formed by the internal panel and the bottom. Especially the full length panel, that would help. Effectively making for a much deeper dado. I’m thinking perhaps 1/2” square stock.

It is equally important to have a good joint on that top panel running in the center. As is, I think you would want the top of the table to add support, so you want it to be securely attached to the case in multiple places. That way it will act as a the top skin of the torsion box formed by the case. But in all cases, you need good joints on all the panels.

A face frame is critical too. Since there are not full front and back edges (because of the drawers), the face frame sort of functions like this. So this frame should be as large as possible and very well attached.

Bottom line, generally looks good, just make sure the joints are really solid. And I think adding some extra material to the joints of all the panels would help a lot and not interfere with the overall design.

I don’t think typical cabinet construction is good enough since, typical cabinets are not self supporting over a long span like that.

Also, use the best darn plywood you can get. I’d use Baltic Birch, though that comes in 60”x60” panels, so I’m not sure what the best thing is you can get in 4’x8’ sheets. But you want the best you can get.

-- Clin

View JBrow's profile

JBrow

1366 posts in 1061 days


#12 posted 10-18-2016 01:02 PM

JakeK,

One other thought occurred to me. The assembly/outfeed table could interfere with the travel of sleds and the mitre gauge. While the lifting castors make the table mobile, I suspect moving the table out of the way of the mitre gauge bar would become an unwelcome and frequent chore. Of course slots that align with the table saw mitre slots could be incorporated into the top of the torsion box, but I would think the slots would weaken the assembly table and potentially introduce some unwanted flex in the torsion box top. A thicker top layer of the torsion box or perhaps a two layer torsion box top could solve this problem. A thicker top will affect the height dimension of the supporting lower cabinet.

View tmasondarnell's profile

tmasondarnell

99 posts in 1930 days


#13 posted 10-18-2016 01:37 PM

JakeK

Looks like a good plan.

I do have experience with those castors. At my company, we use them on equipment we manufacture to facilitate move in. They are great, but they are not easy to raise or lower. So f you plan on moving the table around frequently, they would be frustrating.

Good luck

View JakeK's profile

JakeK

48 posts in 821 days


#14 posted 10-18-2016 04:11 PM

Clin, thanks for your response. I haven’t thought of it as a torsion box but that makes sense. I thought about a face frame but i’m wondering how much strength it will really add if the pieces are only 3/4” wide x 3/4” thick. I had originally planned on either edge banding the plywood or just leaving it natural since it is shop furniture.

Regarding the joints, there are several places where plywood is dado’d in on both the front and back side. 1/4” dado on each side only leaves 1/4” of meat in the middle. I’ve never tried doing this before. Do you see this as a weakness? should i make 3 separate cabinets and screw them together instead?

I’m now considering maybe making a rectangular metal tube frame to go between the cabinet and the casters. Maybe that would be the strongest way to go.

View JakeK's profile

JakeK

48 posts in 821 days


#15 posted 10-18-2016 04:16 PM

JBrow, i had considered this. I’m thinking of just putting the outfeed table right below the height of the table saw miter slots so they wont get hit by the miter gauge. That’s how my current crappy outfeed table is. It’s only really there to catch large pieces. I also thought about maybe making a small attached outfeed table, say 8-10” deep that attaches to the back support angle iron on the saw and height wise is just above the outfeed table. That might not be the best idea though, not sure.

I’m not crazy about adding another sheet of MDF to the top of this thing. At some point this thing is going to get unbearably heavy.

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JakeK

48 posts in 821 days


#16 posted 10-18-2016 04:18 PM

tmasondarnell, thanks for your reply. That is good to know about those casters. I wouldnt say i plan to move it frequently, but then again when i do want to move it i dont want it to be a hassle. Do you know of a product that works better?

View clin's profile

clin

927 posts in 1137 days


#17 posted 10-18-2016 05:04 PM



Clin, thanks for your response. I haven t thought of it as a torsion box but that makes sense. I thought about a face frame but i m wondering how much strength it will really add if the pieces are only 3/4” wide x 3/4” thick. I had originally planned on either edge banding the plywood or just leaving it natural since it is shop furniture.

Regarding the joints, there are several places where plywood is dado d in on both the front and back side. 1/4” dado on each side only leaves 1/4” of meat in the middle. I ve never tried doing this before. Do you see this as a weakness? should i make 3 separate cabinets and screw them together instead?

I m now considering maybe making a rectangular metal tube frame to go between the cabinet and the casters. Maybe that would be the strongest way to go.

- JakeK

A face frame adds a lot of strength. The frame has similar properties to the flange on an I beam (the top and bottom parts of an I-beam). A face frame would typically be 1 1/2” wide, it’s not edging on a frameless cabinet. Also, where two cabinets meet, like your two center sections, the frame would be at least 3×3/4 = 2 1/4” wide. If it were made up of three separate cabinets, the combined width of the face frames where two cabinets meet would be 3”.

Let’s say you have a 1 1/2” wide face from on the end of 3/4’ plywood. The faceframe tends to make the panel behave as if it were 1 1/2” thick. Again, similar to the way an I-beam works. As important, it greatly strengthens the edge of the panel. Making it very, very much more rigid. It makes it much hard for it to buckle or bend.

For example, take a simple piece of paper, and it is very flimsy, now fold it at a right angle, it is not very much stiffer than before. Something similar happens here, though not as extreme, but same principle.

I understand you concern about removing too much material, with the back to back dados. If the final assembly is well fit and glued properly, it’s not a problem, though, an 8 ft long piece this large with these thin areas, might be at risk of damage before you get it assembled.

If you did it as six separate cabinets, you would have the advantage that the internal panels would actually become two sheets, assuming you put full 3/4’ thick backs on all the cabinets.

For this to work well, the cabinets have to be joined together very well. Not just a screw here and there like kitchen cabinets. These would need to be bolted together to create a unified assembly.

I do see a lot of advantages to building them separately. It is much easier to work with smaller units. If you bolt them together, you can always separate them later and use the cabinets in a different way.

But, I cannot stress this enough, they need to be attached really well to each other. And I would consider making a frame as a base for the cabinets to set on. I would put a center frame member running the length, as well as the long front and back members. All of these will help carry the tension the bottom of the structure would be under.

Similarly, if you tie the cabinets into the top torsion box very securely, the top will carry compression, and again greatly reduce any tendency to sag.

In the end, there’s no reason a structure this big cannot be very strong and rigid without resorting to steel or 2×4 construction. It’s not a house supporting thousands of pounds. But just like a torsion box, it requires that it be tied together well so that each section supports the other. In other words, relatively flimsy units, tied together properly can make a strong rigid structure. Flimsy units tied together loosely, and you have a flimsy structure.

Finally, I don’t know if you are perhaps shying away from face frames, thinking they are a lot more work. While they are an extra step, they are really easy to make using pocket screws. And they hide a lot of less than perfect issue with the edges of the panels, and you don’t have to edge the panels. So in the end, I don’t think face frames are necessarily much more work, and they add a lot of strength.

In your case, I would consider make separate cases, bolting together and resting on a base frame. But then build one large face frame for the whole thing. While this works against separating them later, if you ever wanted. A unified face frame would add more strength. And then you have no issues aligning face frames. I really like that idea.

You need really straight wood to build a frame that large. Consider making the face frame material from plywood. You can rip nice long straight piece of wood doing this. This is another reason you want really good plywood with no internal voids.

And you will only really see the plywood at the end of the cabinet. You could still edge band or trim the exposed sides if you wanted. All the inner edges would be hidden by the drawers.

-- Clin

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JakeK

48 posts in 821 days


#18 posted 10-18-2016 05:44 PM

Clin, i’m beginning to come around to the idea of 6 separate cabinets bolted together. The construction would be much easier and less cumbersome, although i’d have an added expense of additional plywood. When i was thinking of the face frame, i was thinking it’d be just the width of the plywood so i didnt see it helping at all but if it were wider, that’d make a difference. I was just trying to maximize the area for drawer space. So if the face frame hung over each ‘bay’ by 3/4”, i’d lose 1 1/2” of drawer space, but maybe thats the price you pay for added strength.

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Lazyman

2484 posts in 1528 days


#19 posted 10-18-2016 06:51 PM

My intuition tells me that if you don’t have a face frame or an apron at least supporting the lower shelf, it will eventually sag and possibly even break. I would be afraid to stand on the bottom shelf in the middle. I would compare this more to a truss bridge than a torsion box and you need some pieces on the outside that are oriented vertically to provide the rigidity that you are getting with the sheet down the middle. Truss bridges usually have something like an i-beam that provides that horizontal stiffness between the verticle beams and a face frame, stringer or apron under the bottom shelf would give you that extra support.

Another design concept to consider is to basically build a truss bridge from 2×4s and 1×1s, possibly even including some diagonal or x-shape ties to replace the plywood down the center, and skin it with 1/2” plywood. I think that you will get a lot more strength across that span with beams forming a frame with thinner plywood laid across it to form the horizontal shelves.

My 2 cents.

-- Nathan, TX -- Hire the lazy man. He may not do as much work but that's because he will find a better way.

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JakeK

48 posts in 821 days


#20 posted 10-18-2016 06:58 PM

So you’re basically saying to make a torsion box to set the cabinets on? I may do that, or i may just stick with a metal tubing frame with a sheet of plywood on top for the cabinets to sit on. Although i’m sure a 2×4 torsion box would be much cheaper.

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jimmy J

229 posts in 2520 days


#21 posted 10-18-2016 07:07 PM

You have room for a mobile 4’x8’ horizontal cabinet? WOW!!

View JakeK's profile

JakeK

48 posts in 821 days


#22 posted 10-18-2016 07:10 PM

I have a junker version in my current garage and yeah it takes up a large chunk of my working area. Once my new 28×32 shop is complete i will have some breathing room and wont be tripping over crap all the time.

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jimmy J

229 posts in 2520 days


#23 posted 10-18-2016 07:10 PM

and think about pocket screws here. forget all those daddos.

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JakeK

48 posts in 821 days


#24 posted 10-18-2016 07:15 PM

I like dado’s for alignment purposes but if i make 6 separate cabinets that will be less of an issue.

View Lazyman's profile

Lazyman

2484 posts in 1528 days


#25 posted 10-18-2016 07:42 PM



So you re basically saying to make a torsion box to set the cabinets on? I may do that, or i may just stick with a metal tubing frame with a sheet of plywood on top for the cabinets to sit on. Although i m sure a 2×4 torsion box would be much cheaper.

- JakeK

I guess if you think about it, what you should really model it after is a long dresser. If you put 3 2×4 stretchers across both the bottom and the top oriented so the 4” dimension runs vertically you will get a lot more support in the middle than a 3/4” piece of plywood. With 2×2s to replace the vertical plywood pieces in the middle, it will be even stronger. For the corners, you can use 2×4 as well but you can make a pretty darn strong corner by gluing plywood to form an L. To see what I am talking about, you can look at my small assembly table project here. This type of leg is almost as strong as a 4×4 but with a fraction of the weight. My table is much smaller than yours and doesn’t have the support issue caused by the long span as yours does but I’ll bet I could put a small car’s weight on it.

You will also notice the ingenious method I borrowed from Norm Abrams for making it mobile, though I might not want to lift yours by hand since it will be much heavier with cabinets underneath it. Note that the design of my table was adapted from Norm Abrams who made one just like it the size of yours, including a simplified torsion box for the top. Beef it up a little to support cabinets and you are there.

-- Nathan, TX -- Hire the lazy man. He may not do as much work but that's because he will find a better way.

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JakeK

48 posts in 821 days


#26 posted 10-18-2016 07:46 PM

Funny, i just watched that episode yesterday. He built a clamp rack in the same episode.

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JBrow

1366 posts in 1061 days


#27 posted 10-18-2016 07:48 PM

JakeK,

If you decide to build separate cabinets, 6 cabinets could be built but only 4 cabinets would be required; a pair at each end. A single base on which to set the cabinets as well as a non-load bearing frame to connect the cabinet pairs together at the top would be needed to achieve the overall 8’ long assembly table base and limit the number of castors to four. This would leave an open bay in the center where center drawers could be installed. The torsion box top would be supported by the end cabinets.

For what it is worth, I really like Lazyman’s X-brace skinned with plywood as a center spine idea. It seems like a very strong structure and wonder whether ¼” plywood on each side of the X brace could provide comparable strength to ½” plywood for this application.

View JakeK's profile

JakeK

48 posts in 821 days


#28 posted 10-18-2016 07:59 PM

JBrow, not sure i follow. If i only built 4 cabinets, how would i bolt them together in the middle? I’m having trouble visualizing what you are saying.

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JBrow

1366 posts in 1061 days


#29 posted 10-18-2016 09:42 PM

JakeK,

Sorry for the confusion. The idea is that there are three major components to make up the assembly table base; a single large base where castors would mount and which would act as a platform for the cabinets, 4 separately built cabinets, and an upper connecting frame that hold the cabinets together at the top and provides for center anchor points for the torsion box top.

The sketch attempts to illustrate the idea.

View clin's profile

clin

927 posts in 1137 days


#30 posted 10-18-2016 11:41 PM

I think JBow’s idea is fine, just make sure that top frame is substantial. It will be under compression as the outer cabinets try to fold inwards. There’s a huge amount of available strength IF the top is rigid and not allowed to compress. Then the bottom only need to handle tension and doesn’t need to be a beefy frame to carry the load itself.

Again the actual torsion box top could support the top load, but only if it is secured to the cases in many spots. Not just the typical 4 or 6 screws to keep it form sliding around.

The bottom doesn’t need to act like a shelf with cabinets sitting on it. That would require a very strong base. If the whole thing is an integrated structure, it would be very stiff without having a base that can support the load spanning between the casters. Having said that, I still would build some sort of base frame. I just don’t think it needs to be steel or something like that (not that anyone proposed that).

It really makes no difference how you look at this, I-beam, truss, torsion box. It’s pretty much the same thing. Bottom line is make the pieces carry the load. Top pieces will tend to be in compression and bottom in tension. If you tie this together, like the web of an I-beam, or webs in torsion box, or members of a truss, then it will not sag.

I’m not a fan of pocket screws in this case. I use them for cases, but this is more loading than typical. As I mentioned earlier, I would even reinforce a dado. This can be very strong and stiff, but only if the joints hold. Since it is a one-of-a-kind, I’d definable err on the side of overdoing the joints.

I would make the backs full thickness and insert them in rabbets, or butt joints with pocket screws. That would prevent any possibility of the back of the sections racking. And as mentioned by others, the face frame is going to play a large roll in preventing the front sections from racking. As will tying it all together.


Clin, i m beginning to come around to the idea of 6 separate cabinets bolted together. The construction would be much easier and less cumbersome, although i d have an added expense of additional plywood. When i was thinking of the face frame, i was thinking it d be just the width of the plywood so i didnt see it helping at all but if it were wider, that d make a difference. I was just trying to maximize the area for drawer space. So if the face frame hung over each bay by 3/4”, i d lose 1 1/2” of drawer space, but maybe thats the price you pay for added strength.

- JakeK

You are exactly correct, you lose some usable width of the cabinet. And it is just as you say, you lose some space, gain some strength. Typical engineering trade-off. It’s common to make the face frame extend one plywood thickness past (just as you described). Then you can just use scraps of plywood as spacers to support the drawer slides. That’s simpler than using the brackets. Though drawer boxes need to match well for a proper fit.

If you go with JBrow’s idea and only make 4 cases. Then I would definitely make those front vertical piece 3×3/4” = 2 1/4” wide. Since there is just one thickness of plywood. But that is common built in cabinet construction and I think fine.

-- Clin

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JakeK

48 posts in 821 days


#31 posted 10-19-2016 12:17 AM

JBrow, thanks a ton for making that drawing. i’ll bet you did that about 50x faster than it would’ve taken me to do in sketchup :) Much appreciated.

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JakeK

48 posts in 821 days


#32 posted 10-19-2016 12:19 AM

Clin, understood about the face frame. I will take your advice there. Thanks

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JakeK

48 posts in 821 days


#33 posted 10-19-2016 01:20 AM

I really like the idea of using dog holes for clamping stock to the table while you work on the edge of a board. Anybody have any good ideas for holding a board down to work on the face of a board? say you want a piece of plywood upright so you can run the domino along the face. or maybe you are edge banding plywood with 3/4” hardwood and you want to flush trim it down. You might want to run the router along the edge of the board. I know you can use a face vise to at least grab onto the edge a board sanding vertically, but that might not be enough holding power. I was also thinking you could use kreg clamp track on the side of a torsion box or something along those lines. Kreg also has a ‘clamp vise’ that looks simple to install but kind of cheesy. What do you do in that situation?

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