Edge finder question.

J

John TV

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So just wondering about my technique of using a edge finder. I am new to the milling world and used an edge finder for the first time the other day. I have watched enough YouTube to see it often but it was not as "clear" to me where the edge was as it seemed watching other people. That said, my Rpn was quite slow,300 to 400 or so. Did not have the time to play with rpm speed. Does the edge finder work better with higher rpm? Other techniques you might suggest?


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I typically run them at ~1,000rpm. I've run some a fair bit higher (accidentally...) without issue, but I've also seen them come apart if run too fast.

Some people like to "flick" the tip to throw it farther out of alignment before creeping up on an edge. I don't really think it's necessary, but up to individual preference. If it's visibly far out of alignment, you can watch it change as you close in on your edge, where if it's relatively well aligned (running concentric) to start, you might come in to your edge too fast and be surprised when it "breaks." Play with both and see what you prefer would be my advice.

Good lighting (as everything else in the shop) is pretty critical as well. I've run some machines where you really have to focus to see it jump over because of awkward lighting. If you've got a lamp on the machine, having it somewhat backlit seems to work well for me.
 
Hi John, Guys,

There are many ways to find the edge of ones workpiece. The old fag paper trick is one, small ball race on a mandrel is another, or you could used a rotating laser beam. This last one is actually very useful for finding the center of a hole or rod. I use mine on both the mill and the lathe.
Here are a couple of pictures of mine. Sorry I don't have pictures of my other ones.


01022015-001.jpg 01022015-003.jpg
 
BaronJ where did you get or do you have plans for the laser setup you show. For some reason I have a hard time with the edge finders, Light and not as good at seeing things at times may be to blame on my part. I have tried fast and slow, to fast and it did not like it.
 
Hi Ken, Guys,

The laser edge find that you see is my interpretation of one that I saw on the net a couple of years ago.
However if you want to build one it is very easy to make. A caveat first ! Find a suitable laser, not all lasers are suitable !
Let me explain, The first laser pointer that I tried didn't have a circular beam, the spot was actually a quite lobsided oval and produced a thick line.
Then I picked up this very cheap laser pointer in the local Aldi store.

30012015-005.jpg

As you can see I broke it in half. The top bit is a ball point pen and a pullout pointer. I didn't need that bit. The bit that is needed is in the bottom half. Batteries and all. The button is one of those press and hold to turn the laser on. Testing this one I found that it produced a sharp round spot, ideal for this application. At a distance of 6" to 8" inches I get a bright round spot about 1.5 mm in diameter.
In the first picture of the previous post you can just see the button peeping out the side.

Once you have a suitable laser all you have to do is decide on the angle that you need to get the spot in the right place on the table. If I remember correctly, I used about 15 degrees. Then you need a suitable piece of aluminum plate, about 60 mm square or so and thick enough to drill for a spindle. I used a length of 1/2" inch drill rod. Then using a protractor to set the angle, clamped it in the mill vise and drilled a second hole so the two met at the bottom. The second hole was drilled with the same size drill. It turned out that 1/2" was the right size for the laser body.

At this point I had a square piece of 20 mm thick aluminum plate with two holes though it intersecting at one end. At this point I heated the plate and pressed the spindle into the first drilled hole. Using this spindle as a reference, I milled the two sides at an angle to match the angle of the laser pen body. I machined the non hole side first, so all I had to do was rotate the work 180 degrees to do the other side and machine a slot down that edge to clear the switch button.

01022015-004.jpg 01022015-002.jpg

One of the things that I aimed for when I made this, was symmetry. Though at the speed that you spin it, which isn't very fast, there is no noticeable out of balance. You will also notice that the spindle has deformed the metal in the hole that the laser fits into. This happens to be lucky chance, because it prevents the laser from slipping right through the hole.

I hope that I have given you enough information to go ahead and build one for yourself. If you have any questions just shout out. Being new to this web site I'm not sure exactly how that works, particularly when the notification Email I get informs me that I will not receive any further mail about this thread unless I visit it again. To be honest I'm not exactly thrilled at that !
 
BaronJ said:
Hi Ken, Guys,

The laser edge find that you see is my interpretation of one that I saw on the net a couple of years ago.
However if you want to build one it is very easy to make. A caveat first ! Find a suitable laser, not all lasers are suitable !
Let me explain, The first laser pointer that I tried didn't have a circular beam, the spot was actually a quite lobsided oval and produced a thick line.
Then I picked up this very cheap laser pointer in the local Aldi store.

View attachment 273761

As you can see I broke it in half. The top bit is a ball point pen and a pullout pointer. I didn't need that bit. The bit that is needed is in the bottom half. Batteries and all. The button is one of those press and hold to turn the laser on. Testing this one I found that it produced a sharp round spot, ideal for this application. At a distance of 6" to 8" inches I get a bright round spot about 1.5 mm in diameter.
In the first picture of the previous post you can just see the button peeping out the side.

Once you have a suitable laser all you have to do is decide on the angle that you need to get the spot in the right place on the table. If I remember correctly, I used about 15 degrees. Then you need a suitable piece of aluminum plate, about 60 mm square or so and thick enough to drill for a spindle. I used a length of 1/2" inch drill rod. Then using a protractor to set the angle, clamped it in the mill vise and drilled a second hole so the two met at the bottom. The second hole was drilled with the same size drill. It turned out that 1/2" was the right size for the laser body.

At this point I had a square piece of 20 mm thick aluminum plate with two holes though it intersecting at one end. At this point I heated the plate and pressed the spindle into the first drilled hole. Using this spindle as a reference, I milled the two sides at an angle to match the angle of the laser pen body. I machined the non hole side first, so all I had to do was rotate the work 180 degrees to do the other side and machine a slot down that edge to clear the switch button.

View attachment 273762 View attachment 273763

One of the things that I aimed for when I made this, was symmetry. Though at the speed that you spin it, which isn't very fast, there is no noticeable out of balance. You will also notice that the spindle has deformed the metal in the hole that the laser fits into. This happens to be lucky chance, because it prevents the laser from slipping right through the hole.

I hope that I have given you enough information to go ahead and build one for yourself. If you have any questions just shout out. Being new to this web site I'm not sure exactly how that works, particularly when the notification Email I get informs me that I will not receive any further mail about this thread unless I visit it again. To be honest I'm not exactly thrilled at that !
Click to expand...
I started collecting for this project but have yet to build it, I also picked up some little centrifugal switches so that it turns on when the spindle rotates. they are small capsules. Since starting this I picked up a center finder that has a 60x eyepiece that you look at the part through and it cost not much more than the batteries cast at the swapmeet.
great job on the project still want to make one, it is on the list.
 
Hi Ed, Guys,

Thanks for your post :) You just reminded me, :oops: I forgot to say that I use an elastic band to depress the switch
 
I always use mine at 1500 rpm. If you go too slow it won't flick very sharply.
 
Starrett recommends 800-900 rpm for their edge finders. Seems to work fine for me.
 
Hi Guys,

I found another picture, it also corrects some dimensions that I recalled incorrectly and gives the date I made this.
I didn't realise that it was nearly four years ago.

Center_Finder.jpg
 
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