Cross slide and compound dials

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whateg0
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Re: Cross slide and compound dials

Post by whateg0 »

Nowadays, a guy could 3d print an indexing wheel with 125 divisions pretty easily, and if made big enough, a thou or 2 of error in a given tooth is insignificant. What I've done in the past for stuff like this is draw up a circle divided into 125 (for example) divisions, or 2.88*, and print it out at a large scale. Mount a stylus on the HS, then manually lock the spindle with some sort of clamping device so that the stylus lines up with one of the printed lines. Here again, if you are off a thou at 5" away from the axis, and cutting a 2" diameter dial, the error is only 0.0002". For some applications, that's not good enough, but for many it is.

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mklotz
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Re: Cross slide and compound dials

Post by mklotz »

A disk with a diameter of 19.894" will have a circumference of 19.894 * pi = 62.5" or, equivalently, 2*62.5 = 125 half-inches. Make a disk of that diameter, wrap a tape measure around it, and you're set to go.

If 19.894 is too big for your purposes, halve the diameter and use every quarter inch mark.

9.947 * pi = 31.25 or 4*31.25 = 125 quarter inches
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johnfreese
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Re: Cross slide and compound dials

Post by johnfreese »

You can do it on a rotary table without index plates. Create a table in Excel giving the angular position for each division.
Mr Ron
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Re: Cross slide and compound dials

Post by Mr Ron »

I found and ordered a 125 tooth gear for $4.50 + shipping. It is only about 2" in diameter, so i will have to come up with a way to transmit tooth position to scribe marks on a dial. It will be too small to do on a lathe, so I will have to come up with a fixture. If you have any ideas, I would like to hear them.
Mr.Ron from South Mississippi
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Harold_V
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Re: Cross slide and compound dials

Post by Harold_V »

Shouldn't be too hard to make a simple fixture that holds the gear and part with their centerlines horizontal. They'd share a common shaft, so they'd turn in unison. A pin in a slide, spring loaded, would index the gear. The pin would have a flattened end, wider than the minor diameter of the gear so it would center the gear the same way with each index.

If you have access to a straight shank pantograph needle, you can cut very nice lines that can be paint filled, making the dial easier to read. An epoxy paint might give greater life, and bead blasting the dial before painting would provide a nice matt surface, reducing glare, making the dial all the easier to read (similar to satin chrome, just not rust resistant).

I've never had to make a dial, so I don't know if there isn't a better way to go.

H
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Mr Ron
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Re: Cross slide and compound dials

Post by Mr Ron »

Harold_V wrote: Sat Apr 21, 2018 3:29 pm Shouldn't be too hard to make a simple fixture that holds the gear and part with their centerlines horizontal. They'd share a common shaft, so they'd turn in unison. A pin in a slide, spring loaded, would index the gear. The pin would have a flattened end, wider than the minor diameter of the gear so it would center the gear the same way with each index.
Thanks Harold. It's a pretty small size gear to work with so I will have to put my magnifier glasses on. I love challenging tasks. Right now, I'm engaged in home repair, so I won't get around to it just yet.
Mr.Ron from South Mississippi
SteveM
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Re: Cross slide and compound dials

Post by SteveM »

Turn a shaft between centers with two shoulders, one for the gear and one for the dial.

Thread the part of the shaft on the diameters so that once you put the gear and the dial on the shaft, they can be clamped with nuts.

You aren't worried about them slipping, as you won't be imparting any turning force on them.

Make something to stick something into a tooth and hold securely. If you google lathe indexing, you will probably get a bunch of good ideas.

Put a pointed tool in the toolpost and put a stop on the carriage to limit the travel.

Use the pointed tool to scratch your 125 lines, then move the stop a bit and extent the line for the five and ten marks (would those be the Woolworth marks?).

Steve
Mr Ron
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Re: Cross slide and compound dials

Post by Mr Ron »

Indexing jig.jpg
Here is my idea for engraving cross feed and compound dials for my lathe. The idea is to clamp the yoke around the lathe spindle which is a 2-1/4-8 threaded spindle. the 125 tooth gear will go onto the arbor which in turn goes into the arbor housing which is held in a 5C collet in the lathe. Thrust bearings will keep the arbor tight, but still free to rotate. A ground scriber in the lathe tool post will scribe the dial blank. A plastic strip will index the gear. If you can think of anything that can improve upon my setup, let me hear it.
SPINDLE YOKE.jpg
SPINDLE YOKE.jpg (10.15 KiB) Viewed 5385 times
P.S. Once the dial is made, how do I go about engraving numbers on the dial? I'm thinking number stamps?
Mr.Ron from South Mississippi
pete
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Re: Cross slide and compound dials

Post by pete »

Number stamps will work of course, you'd need a fixture to hold them the correct distance from the front or rear of the dial and truly vertical. Then there's exactly how much force is required for each different number so the impression depth is the same if that's important to you. I hate sending work out if I can possibly manage it in my own shop, but today and afaik most trophy engraving shops have gone to 3 and 4 axis cnc engravers. No idea about costs, but one of those places will get you any size of numbers and in almost any font you could want and properly cut just like the divisions are. If you just want something that works then the stamps would work well enough. Just be sure there factory marked or you mark them so your certain which way is up. Please don't ask why I say that. :-) I also wouldn't stamp them with the part in the lathe. Your spindle bearings won't like that very much.
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