Adding a Cutting Table to the KRMx01
One of the first upgrades to the KRMx01 is the addition of a cutting table to the machine. A cutting table gives a firm surface that will allow you to clamp your work piece down and at the same time is friendly to your router bit in the event something goes wrong.
If you have the second book in the series, Mr. Simpson suggests the use of SlotWall™ to make the clamping table from. This would be a simple and great solution if I could find the stuff. It seems that the Home Depot stores in my area do not carry it any more, and buying otherwise in multiple full sheets is cost prohibitive for me. My solution is to make my own.
Materials and Tools Required
To make my cutting table (clamp table) I will use a T-Slot cutter I purchased from Amazon. It is a Yonico 14190q T-Slot cutter router bit for 3/8 inch hex bolt heads, 1/4 inch shank. See the image to the left. I purchased two of these in the event that I ruined one somehow. I used a couple of pieces of left over 3/4" MDF for the actual table. Aside from that, I used the screws, countersink and other materials called out in the book.
About Routing the T-Slots
To route the T-Slots, I set the depth of the T-Slot cutter to the maximum depth I could. This ended up being right at about 1/2 inch down. The idea was to leave as much material as I could above the slot to support the bolt head. The side cutter will only allow you to go so deep with the cutter. I simply set it as deep as the cutter would allow. The only drawback I see to making my own and not using the SlotWall™ material is that I have less area to support the bolt than I would have with the SlotWall™ stuff. Because the support is only at the 1/4-20 bolt head is the reason why I wanted to leave as much material above the slot as I could. Whether it ultimately works or not only time will tell. Routing the T-Slots requires some sort of straight edge to run your router along and some patients. Routing is kind of slow and you want to make sure you keep pressure against your straight edge to keep you slots nice a straight. Be sure to clamp your straight edge down.
Sizing the Cutting Table
When sizing the table there are a couple things to keep in mind. 1) What is the cut width and depth? and 2) Do you plan on surfacing the top? In a perfect world, your build was perfect, everything is level, exactly flat, everything perpendicular, etc, etc. Although I live in the real world, it has proven to me over the last 46+ years to be far from perfect. My plan is to make the table as large as I possibly can, but still small enough that the machine can mill the top to make sure the surface is flat. This requires me to get some measurements.
The X-Axis and Y-Axis Min and Max
To find the X-Axis and Y-Axis minimum and maximum cut size I made sure the router was mounted in the machine and had a bit installed. The smaller the better but it really doesn't matter. I used a 1/4" endmill, because that was the last bit I used in the router before taking it off the JGRO Machine. The four images to the left show the process that the list below describes.
- Move the X-Carriage as far to the left as possible. I moved mine to about an eighth inch from the X-Carriage touching the Y-Beam.
- Move the Y-Carriage as close to the front of the machine as possible. I moved mine until the Y-Carriage front bearing was centered over the front bolt holding down the Y-Beam rails. I could have moved it further towards the front of the machine, but this put the bit at about the center of the front row of carriage bolts holding the table top down.
- Lower the Z-Carriage until the router bit is about an inch or so off the table.
- Place a piece of masking tape on the table under the router bit.
- Lower the bit until it is just about touching the tape.
- Place a mark on the tape along the center line of the bit on both the X-Axis and Y-Axis. See the first image above.
- Next raise the Z-Carriage up a few inches and move the X-Carriage as far to the right as possible. (I moved mine to about an eighth inch from the Y-Beam like I done on the left.
- Place a piece of tape and mark as above. See the second image above.
- Move the Z-Carriage up a couple of inches and then move the Y-Axis as far back as you can. (I done this one the same as I done the front. I stopped when the Carriage bearing was about centered on the last Y-Beam rail bolt.
- Place the tape and mark as above. See third image.
- Raise the Z-Axis and move the X-Axis as far left as you can. Again, I stopped when the Carriage was about an eighth inch from the Y-Beam.
- Place the tape and mark it as above. Se the fourth image above.
- Finally, raise the Z-Carriage all the way up and move the X and Y axis until it is about centered in the machine to get it out of the way.
Determining the Size of the Cutting (Clamping) Table
With the four corners marking our maximum travel start taking some measurements. Measure between the center marks on the two front pieces of tape. Mine measured 31-7/8 inches. Next measure between the center marks on the back pieces of tape. Mine measured 31-7/8 inches. (The same as the front. This measurement can be a little different if you didn't get the X-Axis in the same spot as in the front.) Next, measure between the center marks on the tape pieces on the left side. Mine measured 42 inches. Do the same for the pieces on the right side. Again, Mine measured 42 inches.
These numbers represent the largest size area that you could mill the surface of on the machine itself. You could cut a panel this size and use it, but I took it a step further. Next I measured on the left side in the front from the table top edge to the center mark of the front left tape. This is the control point for the left side. Mine measured 4-1/16 inches. You could measure the back as well, but it could be different for a couple of reasons. Where you placed the X-Axis for the last measurement or maybe the table top isn't exactly square. This does not matter because we took the time to make sure the to Y-Beams were parallel with each other. Next measure from the front edge of the table top to the center mark on the left front tape. This is our other control point. Mine measured 3/4 inch.
I am going to cut my T-Slots on 3 inch centers. To make the math a little easier, I am going to shrink the width of my cut table from 31-7/8 inches to 31-1/2 inches. The remaining 3/8 of an inch in width I will split in half and move the control point by that much. The final size of the cut table will be 31.5 x 42 inches. My control point for fastening down the material will be 4.25 inches X, .75 inches Y. (4-1/16 + 3/16 = 4-1/4")
Laying out the T-Slots
Since I plan on laying out my T-Slots on roughly 3 inch centers, I need to do a little calculation to determine where they will be on my cut table. I want them more or less centered in the cutting table. The first approach is to divide 31.5 by 3 giving me 10, but that would only leave 1.5 inches of material (or .75" on each side) to screw down. So I will use one less slot. 9 Slots x 3 inches = 27 inches. 31.5 inches in table width - 27 inches for slots leaves me with 4-1/2 inches left over. 4-1/2 inches / 2 = 2.25 inches. Now I have all the information I need to lay out the center lines of the slots. The first one will be 2.25 inches from the edge and then every 3 inches from there.
How to actually lay out the lines depends on your router base. My Craftsman router happens to have a base that it 6" wide. So I know that I can lay my straight edge 3 inches from my first line and will be cutting the T-Slot on the middle of my slot center line. If your router is different, you will have to find the center line of the router. Take the width of the baseplate and divide by 2. This will be how far you have to place your straight edge from the first line of your T-Slot, then from that spot move it in three inch increments. You get the idea.
Cutting the T-Slots
Here you see the T-Slots cut into the cut table. The bit that I bought worked pretty well. I only had some edges to clean up along the main channel. This was due I think because I set the bit as deep as I could get it and was not cutting well near the top. After cutting al these grooves, I could tell that the MDF was starting to wear on the bit a bit. The last couple of grooves cut fine but there seemed to be an audible change in the cutting sound.
Piloting the Holes
Quite a few screws are required to hold down the cut table to the table top of the machine. Each of these screws has to have a pilot deep enough so that there will be material above the screws that can be milled away when it comes time to plane the top surface true. These are countersunk 3/8 of an inch. With the holes all countersunk the cut table can be fastened to the KRMx01 table top.
Attaching the Cut (Clamping) Table
While I was taking my wife to post operative visit for her shoulder, my son Zachary finished up the cutting table. He attached first the left side according to the book and then the second. These two images show the process along the way. Thanks Zach!
With the cutting table done, the machine can now start cutting some stuff for itself, like clamps, fences and the dragon cable. This concludes the cutting table add-on.