Squaring a block

There are a few ways to do this.

You need to start with the largest surface, and machine it flat with a fly cutter, or end mill, flip the part over, smack it down on some parallels, and machine the other side until those two sides are parallel. I assume in this case, you just used the stock surfaces?

After that is done, choose the next largest surface. Clamp the just machines surfaces into your vice jaws (you are using a high quality, square vice that is indicated in properly, right?) so that the 2nd largest surface is sticking up past the jaws. Use parallels if needed. Machine this surface with fly cutter or endmill, flip, and do the other side. Now, you have 4 surfaces that are square.

Now, you have a choice. If your block is small, and your mill is accurate, and you have good cutters, you can put the 2nd surfaces that you just machined against the vice jaws, with the first surface against parallels and hang the unmachined side past the end of the vise. Now, you can use the side of your cutter to finish the 5th side, and repeat for the final side. If the part is larger, put the 1st side you machined against the vice jaw, and put the 2nd surfaces standing upright in the vice. You can use a square to make sure it is positioned properly, then flycut the next to last surface, flip and repeat.

Note that nylon can be a difficult material to machine accurately. When you remove some material, the remaining material can warp as soon as you remove it from the vise or other restraint. Internal stresses that were balanced by stresses in the removed material cause it to change shape.

Do you mean the sides of the jaws? First thing is to know what your vice does! Is it parallel? Are the jaws perpendicular to the base? Does it pull up the work when you close the vice? When you know that, you can react properly.

Next is to align your vice on the table. The jaws have to be parallel to one axis (mostly the X or Y axis)

That works if you use a dial indicator to align one side of the work that is used as a reference.

Oh, it is the most accurate way even with the worst vice you can get. Setting it up can consume quite some time.

Depending on the shape, side-milling is accurate enough in many cases. So drop it in the vice, close it and while closing it, hammer the piece down.*) This way, it is aligned with the vices bottom. Now if you side-mill the part (that is sticking out), it is perpendicular to 4 sides. Flip it over and mill the other end.

There are ways of clamping work in the vice, especially if you start with something odd-shaped.

You will read more solutions, all will be OK. Pick the one that fits the job and you feel confident with. You'll need parallels and a dial-indicator to get precision and to be able to handle most clamping problems in the vice.

Nick

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Machine the original surface and while keeping it against the solid jaw, by using parallels and/or a precision square, you can machine 5 of the 6 sides square. You may need to use a piece of "soft" round bar between the rough surface(s) and the movable jaw to keep the part solidly against the solid jaw. Randy

None of these books answer the OP's specific question.

Do the two opposite sides like explained and get a grinding vise to hold your parts with a good surface bottomed. turn the vise 90 deg., clamp it in your mill vise and machine one of the bad surfaces. Remove from grinding vise and machine the last surface in your mill vise.

Any body else use an indicator when squaring a block?

Back in the day,,,,,when we made inserts to go in our molds,,,,,we never went to that much trouble when squaring the blocks. If we got within .005", we called it good enough, cause we were going to grind it later anyway. We just used a square to place the block in the jaws.

Do you mean for getting a machined surface vertical rather than using a square? Randy

Yea. I can see the accuracy of that method, it just seems kinda slow.