To use the three pins, place the vise on the Fixture Plate and slide it up against the two side pins. This locates the vise on the X-axis and ensures it is square (trammed) to the Fixture Plate. Here’s another advantage of Fixture Plates–they make machining parts that are too big for your machine’s travel easier.

With a fixture plate, bolt fixtures on using the threaded holes in the plate. Why use a Fixture Plate? With G10, you can set the values for any work offset. Let’s say the coordinates of the fixed rear jaw, left front corner, on the left vise in the picture above are X20.0 Y11.733 Z0.0 on that left jaw when you drop it into the proper grid position on the fixture plate. You’ve also got a set of fixed coordinates for the right vise. Run your short g-code program with a couple of G10’s in it, and Bob’s your uncle (not really), the work offsets are set and you’re ready to start running parts. It still fits fine in the PCNC 1100 enclosure. Plus, the larger size means there is room for fixture related stuff to sit outside the work envelope. That can be important when trying to use the full envelope: Now, having made sure the Fixture Plate is in the right place, you can see where the T-Slot Nuts are. Use a tool such as a drift to reach through the Fixture Plate holes and align the T-Slot Nuts with the proper holes. With a fixture plate, you measure the location once, and so long as you always install the fixture in the same holes, you won’t need to measure again.

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For more on machining big parts see this article: [ Tips for Parts That are Too Big for Your CNC Machine ] Fixture Plate G-Code Programming Aluminum and your table’s cast iron will suffer galvanic corrosion together. Hard anodizing the aluminum will help a ton to reduce that. In an example below, I set up a vise on the Fixture Plate and it is properly trammed with no further effort. That means the three locator pins have to be positioned relative to one another with sufficient tolerance for that to happen.

Now the real fun begins. We have to drill about a zillion holes. We will do alternating threaded and smooth bores, all the holes get reamed in at least one if not two sizes, they all get chamfered, and they all get spot drilled. Plus, we need to position these holes as accurately as possible. We can ensure the vise is installed repeatably to the same location and perfectly trammed very easily. Basically, the Fixture Plate locates your vise in the Z direction, so what we need to do is repeatably locate the rectangular base to an exact location and make sure it’s square. Install 3 T-Slot Nuts, one in each slot. Position the top and bottom at the right end of the T-Slot. Slide the middle one as close to center as you can reach.With T-Slots, the T-Slot nuts slide. A fixture can thus be located anywhere. That sounds great except that the fixtures can be anywhere. With a Fixture Plate, your fixtures can’t be located anywhere. They have to go into the grid of available holes. In other words, with a Fixture Plate, fixtures are always at a well-defined location. Aluminum is a great material for many purposes, but I prefer steel for Fixture Plates. The one exception is where weight is a problem. This is more likely an issue for rotary axis tombstones than for Fixture Plates. This is a problem for things like machinist’s vises, where we want the jaws to be parallel to the X-axis travel of the machine. In fact, operators spend time aligning vises with that travel, a process called tramming the vise. But with a fixture plate, the vise can be accurately installed and square, so you skip the tramming step. More time saved! We can make the install go even faster by using a sub-plate that the vise is mounted to. Tosa Tool makes one just for that purpose. Build Your Own Fixture Plate Install 2 T-Slot Nuts in the top and bottom T-Slots on the left. Position them at the end of the T-Slot.

The Thermal Expansion of aluminum is also higher than for steel. We’re looking to Fixture Plates for accuracy and repeatability, but if temperatures change much, aluminum will make that a problem. Especially when we consider the large size of a Fixture Plate, which can magnify the issue. Some vendors tap every single hole on the plate, but having both smooth bore and threaded holes is a better design. When using a Fixture Plate, the holes perform 2 functions:One way to improve on an aluminum plate is to install hardened bushings. Of course this will negate most if not all the cost advantage. One can also choose to install the hardened bushing only on holes that become damaged. Tosa Tool’s Fixture Plates are not the cheapest available, but they’re very economical when you consider how well they’re made and what the alternatives are that include similar features.

You have to consider two things. First is the cost of the material is significant. Second is the accuracy is not that easy to attain, particularly for a plate that will be larger than the travels of your machine. Unless you’re an exceptional machinist, you probably won’t be able to build a plate larger than your machine’s travels that is also accurate enough. to cut precise tenons on parts such as chair spindles as shown in Photo B. It was immediately apparent that it would We can bolt fixtures onto the mill table just fine with T-Slots. So why use a fixture plate at all? There’s a grid of threaded holes there. They’re protected from chips by set screws that you remove when you’re ready to use a particular hole.Vibration is always an issue with machine tools, and aluminum has a much lower damping capacity than steel. I don’t know about you, but that’s just a lot of work. If you enjoy it, great, go for it. But I can’t see you’re going to save an awful lot of money. And if you manage to screw up? Dang, that’s an expensive piece of work material to replace. Like what you read on CNCCookbook? These plates are HEAVY, so take care and get help if need be. One thing to keep in mind when handling heavy components is don’t ever lift them clear. It’s all about tilting and pivoting so that most of the weight is supported by the machine table. Then all you have to do is safely guide the plate to its desired location. Also, be careful not to pinch your skin between Fixture Plate and Table or you’ll be sorry! My money is on the full depth bore. If you do go with a combination bore (threaded and smooth sections), make sure the smooth section is at least 1 diameter in depth so dowel pins are positioned with sufficient accuracy