The Stovebolt Site Forums The Shop Area The Tool Chest Precise Frame Measurements

I've been thinking a lot about making precise measurements as I make modifications on my 1-ton frame. Recently my brother showed me a $600 piece of bar stock that had a number of threaded holes in it. The holes are for mounting a caliper to the bar, to make the bar part of a long precise measuring tool.

So after looking at that I was thinking I could make something using the same idea but based on stuff I have laying around.

I have some 10 foot sticks of conduit leftover from a project a few years ago. So I was thinking I'd contrive a way to attach a caliper to one end, and drill a hole on the other to allow mounting a pin to measure from. As long as the caliper is mounted in a way that is stable, and the distance from the stationary point to the drilled hole is known, I should then be able to make accurate measurements of about ten feet without the problems associated with holding both ends of a tape measure and then reading it accurately.

Drilling more holes allows shortening the measurements. Splicing two pieces of conduit would allow extending the reach up to 20 feet.

Since most of my measuring points are holes drilled in the frame, I can use the lathe to turn rod to exactly fit those holes, and either turn some of the rod small enough to fit in the hole drilled in the end of the conduit, or drill a hole in the one piece of rod (on the lathe to ensure its centered) and drop a smaller rod to match the hole in the conduit into.

Does my description make sense? Is there a better way for a guy working alone to make precise measurements up to 20 feet? Is there a commercial product that does the same thing and doesn't cost more than a cheap caliper, a couple sticks of conduit and a little hardware?

i'm not that familuar with what you are replicating, but will the conduit be rigid enough?

Good question. Since much of what I'm measuring is actually comparing one distance to another my first thought is that any flex will cancel out. But in cases where an actual measurement is required that flex would be a problem.

The piece my brother had appeared very rigid.

What if you used something like a very small cable instead? I think any type of small string, twine, etc., may stretch. You could put a small precision crimp piece on one end with a nut to keep it adjustable.

Hmm. A cable of a known length with a loop of some sort on one end, and a caliper fixed to the other. That might work.

The downside is it would need to be pulled tight to overcome the pull of gravity on the middle of the cable.

That is probably the advantage of the conduit over cable, in that it would sag less.

Steve,

I'm not sure you need accuracy more than a standard tape measure would offer. Pulling a tape off of holes, rivets or 'like same' frame locations seems like it would be more than accurate.


Stuart

I was thinking a cable might be better because it would be easier to pull taut, instead of trying to support the sag of the conduit. I also havent done any precise measurements yet...

What if you mounted your measuring device to a piece of threaded black pipe? You could change to shorter/longer pieces of pipe. Could need some extra hands if you went real long.....I haven't done many precise measurements but have used a "story pole" in construction.
Dan

Well Jeff I clamped a stick of conduit horizontal and checked it for sag. It sags...

I also played with my 24 inch caliper and the ten foot stick of conduit and I think I'm going to go that route. The sag will be consistent and most the measurements I'm going to care about its more important both sides be the same than that I hit any particular measurement.

Black pipe might be stiffer, but it would be much heavier and I'd have to buy it while I already have about 40 foot of conduit just leaning against the wall in my shop...

Why not devide this task in two? I used a shorter measuring stick made of stable 3/4" strip of plywood, that could reach the 1/2 way mark of the frame. 1 for the front section to center area and 1 for the rear of the frame to center.
Drill out all necessary hole locations in the stick. Then I compared left to right holes by just flipping the plywood measuring stick left to right on each side. Repeated this on the opposite end of the frame. Fairly accurate and no sag in measurements. Hope this can help.

Forgot to mention. On 1 side Clamp the plywood to the frame and drill out from the back, this should give a pretty accurate hole registration & location.