DFM A2 Steel Dowel Plate 17 Holes MADE IN USA (English 17 Holes)

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Here’s another advantage of Fixture Plates–they make machining parts that are too big for your machine’s travel easier.

Install 2 T-Slot Nuts in the top and bottom T-Slots on the left. Position them at the end of the T-Slot.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! 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. The hole grid on a Tosa Tool Fixture Plate alternates smooth (dowel pin) and threaded holes. The threaded holes take 1/2-13 bolts, and the dowel pin holes are 0.5005″ in diameter and finished smooth. 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. 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:

If you’re like me, you considered building your own Fixture Plate. Seems pretty straightforward, right? I will lay out what you need to know to build a fixture plate, but before doing that, let’s talk about whether it’s worth it. Now that you’ve got a Fixture Plate on your mill, let’s do something useful with it. Consider setting up a vise on the Fixture Plate. We’ll use our normal clamps to mount the vise, except that they’re screwed into the fixture plate instead of T-Slot Nuts. I’m not going to bother showing that because it’s nothing new.

If we make one hole perform both functions, we reduce the tolerance and repeatability with which we can perform the Location function. Imagine dropping a dowel pin down two bores. One is half or even 1/3 as long as the other. Remember, we’re talking 1/2″ diameters in bores that are 3/4 to maybe 0.8″ deep. There’s a chamfer at the top and bottom so we have even less length available. Which bore is going to hold the pin more accurately vertical and in position? 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.

My Tosa Fixture Plate arrived in a nice wooden crate. No cardboard here! It’s a precision component, so I appreciate the extra protection afforded by the crate.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. Installing the Tosa Tool Fixture plate took a grand total of about 20 minutes. Making sure it was set up correctly was easy to do using their key system. Once clamped in place, the dowel pin holes are drilled undersized them reamed to size. Their position is not super-critical, but we should still spot drill and use screw machine-length twist drills. 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. Let’s go a little more in-depth with a particular feature plate. I received a plate from Dan Bye of Tosa Tool for review purposes and installed it on my Tormach PCNC 1100 CNC Mill. Yes, journalists get free product a lot of time, but I’ll tell you the straight 411 about a product anyway. My CNCCookbook business is far more important to me than any review, so I’m not afraid to be critical if need be.