# Direct Diameter Readout-9x20 Lathe



## RichD (May 9, 2010)

About two years ago, I decided to try out a simple (I mean really simple) idea. It required the following items:
A dial and pointer
Simple Brackets
A Roller and a small pulley
Some construction Twine/string
A plumb-bob

THE DIAL
My lathe is a HF 9x20 so the readout dial reads from 0 to 10" (0 to 9 and back to 0) and is subdivided down to .025". The dial face I drew in Autocad and converted the image into a CDROM labeling format. The dial is as you guessed...a CDROM disc with an adhesive label on it.

THE BRACKETS
I used the two small screws that hold the rubber wiper on the rear ways to hold a small horizontal plate with a small offset to clear the gibscrews on the crosslide. A small pulley (actually a hardware store sliding door roller) is mounted on this plate to convert horizontal string movement into vertical movement. A small piece of angle iron also is attached to this plate.

A piece of flatbar is bolted to the angle iron piece in a vertical orientation. There's a terrible picture attached, but I didn't know I was going to post this, and you guys will get the idea.

THE ROLLER
I wanted the roller to convert the ~5 inches of crosslide movement directly into a circumference of 5 inches. The dial simply converts the single revolution into 10" for you.

5/3.1416=1.5915 so that's the basic diameter I wanted (then, minus the diameter of the twine). Measured the twine as best I could, and took that much more off the diameter.

ADDITIONAL INFO
Now this device is really crude but amazingly simple to make and use. I'm sure the folks on this forum can make a real nice one. On mine the roller is simply drilled radially and threaded 1/4-20 for a crude pointer (a carraige bolt with a sheet metal pointer on the end that comes from behind the dial and folds over the circumference)

The roller has a shoulder on each end to trap the string kind of like a sewing thread spool. It is drilled for a running fit on the single stationary bolt that holds the disc to the front of the vertical flatbar bracket.

An angle piece attaches to a bolt in the crosslide "tee slot". A simple "windlass" is used to fine-tune the readout after taking your first measurement.

The plumb-bob keeps the string tight with a single wrap on the roller.

You can coarse adjust quickly by spinning the pointer with your hand to the approximate spot, then fine tune the pointer with the windlass.

It works great and I routinely can cut right up to within .005" of the finish size by eye.

CONCLUSION:
Looks goofy, but works great. If I made another one, I would either lighten the needle pointer, or make it counter-balanced. It seems to sometimes be sensitive to the weight of the pointer when it's in a horizontal position. I usually just move the pointer to either a straight up or straight down position and use the divisions in that location. I've also thought if the dial rotated instead of the pointer, it would always be in balance.

Regards, and hope this wasn't too boring.
Rich


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## Noitoen (May 9, 2010)

That's not a DRO, it's a ARO (analogue read out) :big: :big: :big:
The dial going around would be easier to read


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## gbritnell (May 9, 2010)

Hi Rich,
I understand your device but I'm confused with your explanation of the dial readings.
The lathe dials on my Atlas/Craftsman and my Logan are also divided by 10 numbers, although different in diameter. For every move of one number I get .010 on the radius. Now in between these whole numbers are 10 small lines which gets me .001 on the radius. You say you have 10 whole numbers and these are subdivided by .025 thousands. How many divisions are between the whole numbers? If you had 10 that would mean that every whole number would be .250 thousands on the radius. I'm not familiar with your lathe but that seems a little off to me. Maybe a little more explanation is necessary.
gbritnell


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## RichD (May 9, 2010)

gbritnell
There's an example to download at the bottom of the post as a wmf file, and a couple of crappy cell phone pics to help...

To make your own from any circle
Basically each inch is divided by 10 to yield .100 and each .1 is divided by 4 to yield .025 divisions.

Inch marks are 360/10=36°
Tenth marks are 36/10=3.6°
.025 marks are 3.6/4=.9°

The correct diameter of the roller does all the conversions for you accurately within one revolution.

Hope this makes sense
Rich 

View attachment dial.wmf


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