Building a Micrometer Stand Part 1

These plans were inspired by Useful Machine Shop Tools to Make for Home Shop Machinists by Stan Bray. Unfortunately the plans and instructions in that book are woefully incomplete, often missing key steps and measurements. Furthermore, they use British screw sizes that are not available in the US. So while the book is useful, I think this will help beginners like myself.

Where appropriate I’m including links to my local hardware store. Even if you don’t buy from them, you at least know what to look for.

Micrometer Stand

Micrometer Stand Plans PDF
Micrometer Stand Plans Fusion 360

Conversion Notes

When I originally did my conversions, I did a direct mapping between British BA sizes and US numbered sizes. Then I realized that some numbers sizes such as #5 and #12 don’t actually exist. Yes, you can buy tap and die sets for those sizes and make your own screws. But they are hard to find and not worth the effort. So I went back and only used #4, 6, 8, 10, and 1/4”.

My next mistake was using UNF or fine-threaded screws. In my defense, these are closer to the TPI used by British BA screws. And I already had the necessary taps and dies in my starter set. But UNF screws are hard to come by. Apparently UNC or coarse-threaded is considered the “general purpose” screw design and UNF is only used when vibration is a concern.

Beyond that I had to guess at some measurements. Thankfully the book is printed almost 1:1, so I should be pretty close to the original.

Body

Ideally the body is milled from a single piece of metal. If you don’t have access to a mill, or don’t want to waste the metal, it could be constructed from three pieces that are bolted together.

Milling

Set the part on parallels that are high enough that you won’t cut the vise when cutting the bottom of the U-shape. This doesn’t leave much metal to grab, so center it in the vise and crank it down hard.

Start at one edge and cut thin slices forward and back until you reach the correct depth. I used a 1/2 end mill for this. Lock the X-axis while performing these cuts so the table doesn’t move.

Once the right depth is reached, lock the table height. This is important because you want the bottom to be even all the way across. (Though honestly, nothing touches it so it isn’t really that important.)

Unlock the x-axis, move the cutter over a bit, then relock it. Take off a slice using the the side of the end mill by cranking on the Y-axis handle. Make sure this is a conventional cut, not a climbing cut, or you could yank the part out of the machine.

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Repeat until you’ve reached the other end of the part.

Holes

The holes on the bottom are counter-sunk at 82 degrees to match the US flat-headed machine screws. If you don’t have a counter-sink, it’s not important. There’s enough clearance for pan-headed screws.

The holes on either end are critical. If you accidentally drill one of them off-center, move the other one over by the same amount so that they are lined up with each other. (If I had a long enough drill bit, I would have drilled both holes at the same time. These are called “aircraft” drill bits.)

Cleanup

A belt sander is really useful for rounding over the sharp corners. If you have a narrow strip sander, it can do the inside as well. Otherwise there are always files.

Base

The recommended size is 3” x 1.25” x 1/2” thick. Really it can be any piece of scrap that is wide enough to lend stability to the stand.

Transfer the holes from the base to the body. Transfer punches can help with this. Note that the cheap Harbor Freight set won’t mark steel very well, if at all. But if you are using wood or aluminum then it should be just fine.

If you are 100% perfect in the placement of the holes in the body, the transfer punches aren’t necessary. (But if you are that good, why the hell are you reading my blog?)

The body is supposed to be centered on the base. Unfortunately I drilled one of the holes too big, so I had to move it over a bit. Then I broke a tap and had to move the holes over a second time. Now I have a convenient place to stamp my initials or attach a clamp.\

Slightly counter-sink the holes, it will make starting the tap easier. You may also want to use a slightly larger drill. This will reduce the “thread engagement”, weakening the holding power but also lessening the torque needed to tap it.

image

Support

The support is the piece that actually holds the micrometer. Again this could be constructed from 3 parts but it is better to mill it from a single block.

Milling

Setup is easy since you are cutting parallel to the vise. I’m not sure what the best setup for this is, so I made the top of the part flush with the top of the vise.

Rather than following the plans exactly, I chose an end mill that the was slightly wider than my micrometer and ran it straight down the middle, leaving a shallow slot. Raise the table, then repeat until the correct depth is reached.

While doing this you’ll want to lock the Y axis. This is a pretty easy cut, but there is no sense taking chances that the table will shift.

Holes

The holes on either end are critical. They must be lined up perfectly with each other or the part won’t rotate correctly. Drill them deeper than the plan calls for and you’ll be less likely to break a tap.

Speaking of which, be really careful tapping these holes. The #6 tap is easy to break and you can’t simply move the holes like you did with the base. (So yea, I did have to make a second support. Also, #6 taps are cheap so buy several when you do break it.)

Technically speaking you should use a taper tap to start, then finish the blind holes with a bottoming tap. But again, I drilled the holes deeper than necessary and just used a generic plug tap. Use plenty of tapping fluid, it will help to wash away the chips.

The location of the hole on the side isn’t critical. You can even have multiple if you want to hold things other than a micrometer.

Part 1 Completed

From top to bottom is the support, body, and base. In my next post I’ll talk about machining the custom screws.

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