# Placement of Critical Components

Dave Tutelman -- March 12, 2005

You will learn how to measure the placement of a few critical components:
1. How to measure beam length, and place the beam length rulers properly.
2. How to position the bolts that hold the toggle board.
3. How to align the three sets of bearings so they lie in the same plane.
Bear in mind that the photographs were taken after my NeuFinder 4 was completed. The beam length rulers were already in place, and I was not going to rip them off for the photo session. So it will look a little different from yours when you do these steps, especially the step in 1.2 below.

## 1. Beam length measurement

### 1.1. How to measure beam length

Beam length is defined from the centers of the pivot bolts supporting the rear (left) bearings and the front (right) bearings. But that definition is not easy to measure precisely. So here is a way of measuring the same distance precisely.

The distance from the right edge of the rear bearing block to the right edge of the front bearing block is the same as the defined distance. And it is easy to measure pretty precisely, using the technique shown in the photo above.
• Butt a yardstick against the rear bearing block. Holding it against the block...
• Measure to the right edge of the front bearing block. You are measuring from red line to red line in the photo insets.

### 1.2. Placing the beam length rulers

Before you start, check your measuring tapes against a good ruler, to be sure they were made properly. Believe it or not, some cloth tapes need to be stretched to get to the proper scale. Once you have two good tapes, you can proceed.

Using the method in 1.1 above, set the toggle board for a beam length of 30". Be precise in this measurement; try to get within 1/16", and do not settle for worse than 1/8".

• With the beam length set at a measured 30", mark the backer board where the two indicators are (shown by the blue arrows in the photo).
• If your measuring tapes are still inaccurate and need to be stretched make marks at a few additional beam lengths. You will then have to line up more than one mark when you mount the tapes.
• Mount the two measurement tapes so that the lower tape has its 30" at the rightmost of the marks you just made, and the upper one has its 30" at the other mark. When you have done it right, the tapes will look as they do in the photo.
There are several ways you can mount the tapes. Here are some that have proven successful even before the beta test was completed:
• Contact cement. Lines ruled on the backer board, or even masking tape, can assist putting the cement in the right place and getting the vertical position right.
• Double-sided grip tape. Cut it a little narrower than the measuring tape.

## 2. Placing the toggle board

Start by removing the knobs that hold the toggle board to the T-slot beam. Loosen the T-nuts that hold the toggle board bolts just enough so the bolts can slide in the slots, but not wobble around. Place the toggle board on the bolts through the lower holes, but do not replace the knobs; the toggle board is just resting on the bolts.

 Place the end caps on the T-slot beam. Slide the beam all the way to the left, so the cam-clamp's bolt is up against the beam's end cap, as shown in the picture. Slide the toggle board all the way to the left, so it is almost touching the rotator board, as shown in the picture. The beam length in this position should be 19" or a little less. If it is more than 19", you have exceeded tolerances in placing a number of the holes you drilled. Mark this position on the beam using a marker or pencil through the middle of the unused pair of holes. Release the cam clamps, and carefully slide the beam to the right until the "wand" is clear of the rotator board. While you do this, use your hand as a "clamp" to hold the toggle board in the same position relative to the beam. Carefully lift the toggle board off the bolts, being sure not to move the bolts in the beam slot. Actually, it is no disaster if the bolts move a little in the slot. Remember, you marked their position on the beam. Compare the bolts' position with the marks you made on the beam and, if necessary, slide the bolts in the slot so they line up with the marks. Being careful not to slide it along the beam slot, tighten one of the T-nuts in place. You have now determined the location of the toggle board. The other T-nut should be just tight enough so the bolt tip does not wobble, but not so tight that the bolt cannot slide in the slot. That is because the clearance between the hole in the toggle board and the T-nut "bushing" is quite snug; it is tighter than the tolerance on the spacing between the holes. That means that there is no fixed position for the bolt that will work for both the upper and lower pair of holes. (If you have drilled the holes so accurately that it works for you, then you can tighten both T-nuts.) Hold the sliding bolt's T-nut in position with some sort of thread-locking compound. (Actually I used a bit of contact cement for the purpose. Worked fine, but it took over a day to set up properly.)

## 3. Aligning the bearings

We will align the three sets of bearings, so they all lie in the same vertical plane.

The photo shows three possible positions of a shaft when it is seated in the rear and middle bearings. It can meet the front bearings:
• In the middle, right between the bearings..
• Inboard (toward the backer board).
• Outboard (away from the backer board.
Of course, you want the shaft to meet the front bearings in the middle. So you need to adjust the other bearing sets so they point the shaft in the proper direction. Here's how.