Finding center

drizzle said:
aaaaaaannnnd how do I calculate what half the diameter is and then mark that location?
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Well, 1/2 the diameter of 1.5 is .75 (Dia/2), you'll have to measure the rod that you are using. Just use the machine dials to move to center, or use a dial indicator to measure the table movement.
 
some of you are the absolute WORST at giving advice. OR maybe I am just stupid? HOW DOES AN EDGE FINDER FIND CENTER???? I'm guessing that people didnt read my entire first post. Ok, the edge finder found the edge..... now what? How does my edge finder tell me what 50% of my diameter is when my machine has no digital read out? Telepathy? Do I turn the lights out for 10 seconds and then back on and I will magically have a pilot hole in the center? Here is what I have..... I have a bare bones JET JDM18 mill (no DRO), I have a machinist vise that is missing the nut thing that locks the jaw, I have a Yuasa dividing head. I have a Brown and Sharpe dial caliper, a starett micrometer which is super small, I havent even looked to see how big that goes. I might have another micrometer in the tool box. I have a Mitutoyo dial test indicator and a good assortment of machinist rulers and squares that were my fathers from when he was building models of chemical plants for Monsanto to make chemicals that are killing us all. Oh, and I have an old school tachometer somewhere but not sure where that is or how to use it..

I'm about ready to just measure a few spots to find center, drill it and call it a day.
 
drizzle said:
some of you are the absolute WORST at giving advice. OR maybe I am just stupid? HOW DOES AN EDGE FINDER FIND CENTER???? I'm guessing that people didnt read my entire first post. Ok, the edge finder found the edge..... now what? How does my edge finder tell me what 50% of my diameter is when my machine has no digital read out? Telepathy? Do I turn the lights out for 10 seconds and then back on and I will magically have a pilot hole in the center? Here is what I have..... I have a bare bones JET JDM18 mill (no DRO), I have a machinist vise that is missing the nut thing that locks the jaw, I have a Yuasa dividing head. I have a Brown and Sharpe dial caliper, a starett micrometer which is super small, I havent even looked to see how big that goes. I might have another micrometer in the tool box. I have a Mitutoyo dial test indicator and a good assortment of machinist rulers and squares that were my fathers from when he was building models of chemical plants for Monsanto to make chemicals that are killing us all. Oh, and I have an old school tachometer somewhere but not sure where that is or how to use it..

I'm about ready to just measure a few spots to find center, drill it and call it a day.
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No need to yell. There have been past many posts on this subject. A little efort on your part would have found them.

In the case of using an edge finder, the edge finder makes a distinct jump when it contacts an edge. At that point, you are half the diameter of the edge finder from the edge. For example, if you get a jump at 1.2" and you're using a 1/2" edge finder the location is either .95" (1.2"-1/2*.5") or 1.45" (1.2"+1/2*.5"). If the edge is the fixed jaw of your vise and you have mounted a 1"shaft in the vise, you probably came to the edge from the shaft side. assuming that the vise is mounted with the fixed jaw parallel to the x axis and the fixed jaw is to the rear, The fixed jaw edge is at .95" and the center of the shaft will be .500" (half the diameter of the shaft) less or .45". As I said before, you have to consider backlash so move the table to something less than .45" and move up to .45"

The process is much easier with a DRO but not impossible using the dial and counting turns.
 
drizzle said:
some of you are the absolute WORST at giving advice. OR maybe I am just stupid? HOW DOES AN EDGE FINDER FIND CENTER???? I'm guessing that people didnt read my entire first post. Ok, the edge finder found the edge..... now what? How does my edge finder tell me what 50% of my diameter is when my machine has no digital read out? Telepathy? Do I turn the lights out for 10 seconds and then back on and I will magically have a pilot hole in the center? Here is what I have..... I have a bare bones JET JDM18 mill (no DRO), I have a machinist vise that is missing the nut thing that locks the jaw, I have a Yuasa dividing head. I have a Brown and Sharpe dial caliper, a starett micrometer which is super small, I havent even looked to see how big that goes. I might have another micrometer in the tool box. I have a Mitutoyo dial test indicator and a good assortment of machinist rulers and squares that were my fathers from when he was building models of chemical plants for Monsanto to make chemicals that are killing us all. Oh, and I have an old school tachometer somewhere but not sure where that is or how to use it..

I'm about ready to just measure a few spots to find center, drill it and call it a day.
Click to expand...

The edge finder locates the edge of the work, but YOU have to do the math to figure out where the center is.

I did machine/tool & die work for 15 years before I ever saw a DRO, they didn't exist. I didn't own one until the mid 90's. I did have an edge finder, and later bought a coaxial indicator. But a rod in a drill chuck or collet works just fine for an edge finder. I still occasionally use that method, I have a 1/4 dia hardened rod with a center point ground on it to act as a center punch. Works great in a drill chuck for a quick punch mark when in the mill.

The machine dials are calibrated in 0.001'' increments, and are normally 0.250'' per revolution. You read the dials and count turns. If you need real precision, you use a dial indicator to measure the table movement.

First I think you need to learn to use your measuring tools, it sounds like you are pretty well equipped from that perspective.

 
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ok that is making more sense. Yeah, I had thought about setting up some cheapy dial indicators on my table to measure the movement of it till I got a decent DRO.
 
P. Waller said:
Someone gave me one of these about 20 years ago, I found it about the most worthless tool that I have ever owned, it went straight into the scrap.
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It is not a precision tool and certainly not intended to deliver positions with a few thousandths accuracy. It is a visual tool and depending on the visual acuity of the user should be able to center better than .01".

For someone with just a drill press and no way for making precision moves or measurements, it will work.
 
Hi Drizzle,

You mentioned in one of your posts that you wanted to find the center the old school way !
I posted a picture of a center finder that can be made very quickly without a mill or any special tools. I'm sure that you have a press drill and can use a rule to scribe a straight line.

The device pictured is simply a short piece of flat bar, the only criteria is that it is at least twice as long as the width or thickness of the material that you want to find the center of. You will also need a few inches of drill rod. Again it is not critical. I made mine using 1/4" diameter rod.

Simply scribe a line roughly in the middle right down the flat bar from one end to the other. Find the middle of that line, its not critical, anywhere within 1/8", 1/4" even 1/2" will do, then mark it with a center punch. Use a divider and put one leg into the punch mark you have just made, open up the dividers and scribe a line about twice the drill rod diameter away from each end. Now mark the point where those two lines cross with the center punch.

Carefully drill three holes ! The ones at the ends should be a good fit for your drill rod, the one in the middle should be a good sliding fit for your center punch. Now cut a couple of pieces of drill rod at least as long as the thickness of the material that you want to find the center of and secure one end each end of the bar. Refer to the picture in my first post and the picture in this post.

Also this picture shows a couple of my other home brew center finders. But more about those later if you want.

10-08-2018-001.JPG
 
Hi Drizzle,

Further to my previous post, assuming that you will make a center finder for use on flat or round bar, this is how to use it.

Place the center finder over the material that you want to find the center of with a pin on either side and rotate it so the pins touch at both sides. At this point you can either use your center punch to scribe a line by sliding the whole thing along or just mark as needed.

I noted in another post you said that you have some "V" blocks. Another poster explained how to use them to find a center for drilling round material. There is another simple way without using a "V" block. But it requires that you are able to hold the work piece in a vise square to the drill table. That method simply uses a rule or other thin flat metal plate balanced on top of the round material. To do this you trap the rule between the work and the drill point and then move the work piece until the rule is level. This method works best using the mill where you can get accurate fine movements.

It helps others to help you if you can post pictures of what you are trying to do.
 
Thanks Baron, I will look into making one. Looks like a fun project
 
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