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View Full Version : How do you use a test dial indicator to find a center



FoxCNC1
03-02-2015, 01:14 AM
I know this may not be the best place to post this question but its the forums I most frequent.
I just bought a test dial indication since I realize I am a point where I want to be more accurate with my projects and I noticed some run out of my tool today which caused it to break. - ekk. lesson learned.
Anyway:

I saw some tormach videos where the guy is using a test dial to find the center of a hole and the center of a block. However the part that doesn't make sense to me if that the dial indicator is on a pivot arm and he seems to be moving it arbitrarily. Wouldn't you want the TIP of the dial to be in line with the spindle?

I am trying to incorporate the dial to find the corner X0,Y0 of a work piece and be able to repeatedly find it a second time in case I have to etop the machine.

Any help is greatly appreciated.

stucapco
03-02-2015, 07:55 PM
Center of a hole, YES, edge or corner of the part, NO! Consider a probe of one one sort or another. Lets assume a half inch solid probe. Find the corners, input the location, allow for the probes radius, IE: in this case (assuming top, right corner), add -.25 to the work offset. Then for repeatability add the radius to positioning. G54 X.25 and a safe Y position. Push the part against it and have a more effective cycle. Am i close? Test dial indication (indicOL?) not for edges.

bhurts
03-02-2015, 08:40 PM
Yes I agree with stucapo. You can use a test indicator for finding the center of a circle id or od. Also to square a vise and check for parallel and perpendicular. For finding the edge of a part get a edge finder. There cheap and accurate.

Ben

stucapco
03-02-2015, 08:57 PM
What bhurts just said. I have no doubt. In the event I need 50 or more of these parts we're going to need a stronger more reliable setup was my point. You will soon find a box of broken edge finders and electronic probes. Want a box? lol, bhurts knows, yeah "all them? broken, MEH!" Assumes many guy's working on this project.

I've never seen it end any other way.

daniellyall
03-02-2015, 10:26 PM
you use test indicators for squiring stuff up finding center of holes is a different tool. get a center finder or a edge probe

stucapco
03-02-2015, 10:38 PM
squirrel's work good too! lol, just having fun, no troll intended.

I love this place! Don't stop. We need this place or at least I do.

Thanks guy's, this is great, I have no one else to talk to about this crap.

Worth it.

Hey, how about a funny machining story thread? I have so many...

FoxCNC1
03-02-2015, 10:45 PM
Guys thank you for the replies.
I am still a little confused as to how the center if found. This is the video I watched and notice how the indicator is an articulated arm. Is it me, or it is the dial offset for the center of the spindle?
Doesn't that matter?

https://www.youtube.com/watch?v=uqLT_fkiTo0

FoxCNC1
03-02-2015, 10:58 PM
here is another video.

https://www.youtube.com/watch?v=PCWctxBseno

stucapco
03-02-2015, 11:02 PM
Yes. That's a hole indicator sweep, finds position relative to an established hole. From this point we can relate it to other positions on the work piece. What I thought was in question was the corner or edge position coordinates to find the work piece. I'n which case this is not what you want. Please stay with us and explain as much as you can. We're here to help, If I understood what your goal was it would take seconds to explain. DON'T GIVE UP! Talk to us.

bhurts
03-02-2015, 11:14 PM
The dial is offset yes. That is what you are needing to reach the edge of the hole from center. When you spin the spindle by hand anything mounted in it will spin around that center regardless of how it's offset. You want the indicator to read the same all the way around in a circle.

Ben

FoxCNC1
03-02-2015, 11:14 PM
I appreciate that. I figured that I could find the corner of a work piece the same way the gentleman on the video found the center of the block.
However, it seem like in every scenario the tip of the dial indicator is offset from underneath the center of the spindle... and this is the part that is confusing me. woun't you want the dials needle to be aligned with the center of the spindle?

FoxCNC1
03-02-2015, 11:17 PM
The dial is offset yes. That is what you are needing to reach the edge of the hole from center. When you spin the spindle by hand anything mounted in it will spin around that center regardless of how it's offset. You want the indicator to read the same all the way around in a circle.

Ben

I think you just answered my question. So the "amount" of offset if irrelevant because in the end when the needle is sweeping the holes or circular part, then spindle will be in the center...

okay, what about the second scenario where he is finding the center of the block. I guess it is the same thing.

daniellyall
03-02-2015, 11:22 PM
the dial indicator is offset by x amount what the operator will know what it is there are better ways of doing but that works

stucapco
03-02-2015, 11:32 PM
Yes, center of spindle. It's absolute relative to the spindle. Now we can move on. Well done guy's!

Side note: get an indicOL, grabs mostly any tool holder, any situation. No need for special setup, what ever's in the spindle will do, quick, easy, cheap. I depend on mine for quick tramming. Soft as butter, just nice.

Luck.

FoxCNC1
03-02-2015, 11:50 PM
ekk.... okay.

FoxCNC1
03-05-2015, 09:18 PM
hi everyone I bought a test dial indicator, I but I am unsure on how to find the center of A small Circle as in the picture below.

do in always need to use a swivel arm? - I just don't see how I would do that with a small 0.25 Circle . if anyone can please guide me that would be great.

I also bought an edgefinder , however the slowest speed I can run my Bosch notes (spindle) is 8,000 Rpms. It Works well, but I did notice a bit of chatter as I start To touch the edges of the workpiece. Is this normal? does spindle and collet runout affect the accuracy and repeatability of finding the same edge / 0.0 Point twice?

I want to be a able to find the same starting point in case i have a need to hit the estop Which usally makes you loose steps.

http://i10.photobucket.com/albums/a146/Profoxcg/20150305_202101_zpswdjtecag.jpg (http://s10.photobucket.com/user/Profoxcg/media/20150305_202101_zpswdjtecag.jpg.html)

stucapco
03-05-2015, 10:23 PM
Get an indicOL.(cheap) your way too rigid there. After throw a dowel in it, tram the OD, easier to see, easier to use. However, what your attempting is "doable".

Your on the right track! Keep it up.

underthetire
03-06-2015, 10:00 AM
A little more money, but a co-ax indicator is quite handy for picking up holes, as long as you don't need closer than .0005.

bhurts
03-06-2015, 03:12 PM
I probably wouldn't run a edge finder at those speeds. If/when it flies apart you could get hurt. As to the arm don't forget it's articulated. It can be adjusted to point straight down or moved offset from center. There are many available options if you have the z travel to use them.

shars.com - Universal Dovetail Indicator Holder (http://www.shars.com/products/view/1976/Universal_Dovetail_Indicator_Holder)

shars.com - 14quot Indicator Holder (http://www.shars.com/products/view/8028/14quot_Indicator_Holder)

shars.com - 14quot Indicator Holder (http://www.shars.com/products/view/8028/14quot_Indicator_Holder)

shars.com - Test Indicator Holder Arm Only (http://www.shars.com/products/view/1456/Test_Indicator_Holder_Arm_Only)


shars.com - Zero Set Universal Attachment (http://www.shars.com/products/view/7839/Zero_Set_Universal_Attachment)

http://www.shars.com/products/view/7544/Zero_Set_Universal_Attachment

Ben

FoxCNC1
03-06-2015, 04:26 PM
At what speeds would you guys run your edge finders? It seems the even water cooled spindles don't run much slower.(6K rpms)

Regarding using the test indicator to find the center, if the key to have it on an articulated arm?
I am trying to grasp the concept of if I need to zero it out once I make contact with an edge.

stucapco
03-06-2015, 06:50 PM
"edge finder at those speeds" WHAT! No no, no. We are on a different page here, No, edge finder does not spin in this case. Please be careful, I don't understand and that's ok. I have been wrong before, lol.

stu

Other than that I use a solid edge finder (a probe) I consider accurate. Tramming or truing up a part, vise or work piece I suggest an indicOL.

Edit: indicOL, https://www.google.com/search?q=indicOL&espv=2&biw=1024&bih=681&tbm=isch&tbo=u&source=univ&sa=X&ei=ej76VLTNOouMgwTIkIGwDQ&ved=0CDEQsAQ

I have several, so nice and easy to use.

stucapco
03-06-2015, 07:12 PM
Its a par 29, the mine fields are out of bounds on the right and chinese communists are out of bounds on the left. M*A*S*H reference.

underthetire
03-06-2015, 10:57 PM
Edge finders work best at 1k rpm. 6k will scatter them all over the place. 10k gets real exciting BTDT.

stucapco
03-06-2015, 11:16 PM
I use solid probes as I work in tool steel and setups need to be quick and reliable. Winding up edge finding probes result in a box of broken parts.

underthetire, lol. 10k gets real exciting! Toss whats left in the damn box after you get it out of the chip conveyor. This is funny in a strange way.

My 2 cents.

FoxCNC1
03-07-2015, 09:56 AM
Guys, but how you get a spindle to run at 1K rpm. is this possible with a "real" spindle controlled by variable speed controllers?

underthetire
03-07-2015, 12:34 PM
Most of the time I use them is in vertical machining centers, so yes 50-14k infinitely variable. That's where I miss typed in MDI 10k instead of 1k. Less than half a second from 0-10k rpm and nothing left of that edge finder. So quick even the beaver tail pucker switch wouldn't have stopped that one.

ger21
03-07-2015, 12:43 PM
Guys, but how you get a spindle to run at 1K rpm. is this possible with a "real" spindle controlled by variable speed controllers?

There are different types of spindles. A spindle on a router can not be spun anywhere close to 1K rpm if you don't want to kill it.
Spindles on mills can spin at very slow speeds.

FoxCNC1
03-07-2015, 01:42 PM
I appreciate the help, but some of gents like to speak in code and its confusing.
I just located the zero of a piece of alum. with a metal edge finder at 8 rpms and it was fine. Unfortunately I do not have a real spindle on my cnc router but that will be my my next upgrade.

ger21
03-07-2015, 02:44 PM
If your finding the edges of aluminum, use some probing routines and a piece of precision ground drill rod chucked in the spindle. Quick and easy.

Look through this thread.
http://www.cnczone.com/forums/mach-wizards-macros-amp-addons/56079-cnc-software.html

FoxCNC1
03-07-2015, 03:47 PM
Hi ger. In reality I need to be able to find the edges of any material I cut.
Just an update, my edge finder broke at 8K rpms =( definitely the tool for a CNC router type machine. I need to invest in something else.

ger21
03-07-2015, 04:21 PM
How about this?

The Makers Guide - Triple Edge Finder - THE MAKERS GUIDE (http://www.themakersguide.com/home/products/triple-edge-finder-2)

Or, you can just hold an aluminum plate or angle against your edge and probe to that.

stucapco
03-07-2015, 07:44 PM
FoxCNC1 "Just an update, my edge finder broke at 8K rpms" LOL! Toss whats left in the box. Hope you won't need a bigger box in 6 mouths.

FoxCNC1
03-07-2015, 07:47 PM
^ every post you have made has been garbage. What the problem you trolling?

stucapco
03-07-2015, 07:51 PM
NO! I will back way off now. NO troll intended. I simply have no one else to talk to about this subject.

FoxCNC1
03-07-2015, 08:04 PM
NO! I will back way off now. NO troll intended. I simply have no one else to talk to about this subject.


Then please contribute information and NOT just make fun of the situation on every post.

stucapco
03-07-2015, 08:07 PM
Agreed.

EBurns
03-10-2015, 05:53 AM
I wanted to know if the same method can be used to find the center of every type of dial indicator. I have bought a dial indicator from NRI parts ( https://www.nriparts.com/tools/measurement-tools/urschel/10753bj-rmt-graduation-0075-in-00005-in-dial-indicator/ ) and I want to use it to find a centre. Can someone tell me if the process will be the same?

bhurts
03-11-2015, 03:43 AM
Sorry you have the wrong type of indicator. What you need is a dial "test" indicator to use the methods mentioned.

https://www.shars.com/product_categories/view/5120901/Dial_Test_Indicator

The link is to the correct type of indicator. Stay away from the .0001 indicator it doesn't have enough travel to be easily effective. Stay with the .0005.

Ben

FoxCNC1
03-11-2015, 08:36 AM
Sorry you have the wrong type of indicator. What you need is a dial "test" indicator to use the methods mentioned.

https://www.shars.com/product_categories/view/5120901/Dial_Test_Indicator

The link is to the correct type of indicator. Stay away from the .0001 indicator it doesn't have enough travel to be easily effective. Stay with the .0005.

Ben


I have to ask: what makes these devices more expensive than the next ? Why is a Mi tu too close to 100 bucks if not more

underthetire
03-11-2015, 11:20 AM
Quality baby, and usually the higher end ones have jeweled movements. I have indicators that range from $200 all the way to $2150. Don't think i even own one that measures less than .0005. My $2150 one gets down to micro-inch or nanometer. Stick with cheap ones for now, the more expensive they get the more it hurts when you accidentally smash one.

FoxCNC1
03-17-2015, 11:34 AM
Thanks. I meant to type MITUTOYO.
that one that a jeweled movement. I already bought it, but I will be very careful with it.