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View Full Version : Embarrassing question ... What the heck are these things called?



Fasttrack
11-06-2012, 11:24 AM
I'm having a total brain fart at the moment. There is an indicator that fits in the spindle of a vertical machine and aids in positioning the work piece. It has a dial and is meant to be used while the machine is running. Basically, you move the table left/right and back/forth until the needle stops moving. I've got an import version and, a few years ago, there was quite the controversy regarding the accuracy and usefulness of these tools.

What the heck is the proper name for it?

chucketn
11-06-2012, 11:25 AM
Coaxial indicator?

Chuck

Mcgyver
11-06-2012, 11:59 AM
as Chuck says. Blake is the bid name brand. Got one recently....probably the single biggest example of "why the heck didn't I buy one 20 years ago" I've had

They wouldn't be as accurate as a 10ths indicator mounted on a rod, but they are pretty darn good and soooo easy to use and quick centre the spindle. As always, its not a Q of right and wrong, it's picking the right tool for the job, taking into acount the pros and cons of each and whats required

Fasttrack
11-06-2012, 12:09 PM
Thanks guys! I've got one and I love it but I wanted to pick one up for my BIL for Christmas. I'm at work so I couldn't even look at mine to remind myself.

gwilson
11-06-2012, 12:28 PM
I wouldn't be without my Blake. Just WAY too handy for quickly centering up holes,punch marks,sides of cylinders,etc..

Black Forest
11-06-2012, 12:59 PM
I don't have a coaxial indicator but I do have a 3D taster that I wouldn't part with for anything. For centering the spindle on a hole or a cylinder or finding the edge it is fast. Now a punch mark I don't think it would work.

dp
11-06-2012, 01:10 PM
Guy Lautard's site is offering ready-made rockers for the coaxial indicator project from his #3 bedside reader.

http://lautard.com/rockerpage.html

JCHannum built one:
http://i320.photobucket.com/albums/nn351/jchannum/P1070407.jpg

There is a long (winded) discussion of the coaxial indicator here http://bbs.homeshopmachinist.net/threads/37241-How-to-use-Coaxial-Indicator and includes far more than anyone likely has a need to know. For some reason this is a controversial instrument. It might be less stressful to argue politics or health care :)

I bought an Asian knockoff of the Blake for about $75 and it is worth every penny which is to say not much. It works but has about 1 of internal error (the dial, while not calibrated in degrees, is measuring the offset angle of the rocker).

Fasttrack
11-06-2012, 01:24 PM
There is a long (winded) discussion of the coaxial indicator here http://bbs.homeshopmachinist.net/threads/37241-How-to-use-Coaxial-Indicator and includes far more than anyone likely has a need to know. For some reason this is a controversial instrument. It might be less stressful to argue politics or health care :)



Hah! That was the thread I was thinking of when I referenced the "controversial topic" in my OP. Glad you dug it up. :D

My import one was quite a bit more than $75 but I've been very pleased. To me, it's like having a 3 jaw chuck on the lathe. You lose a little accuracy but it's super fast. If I really need the accuracy, I've got an Interapid DTI that I use - but for most of what I do, these little knick-knacks are great!

Juergenwt
11-06-2012, 02:14 PM
Trying to remember - I think they were commonly known as "SPINNERS".

bborr01
11-06-2012, 04:23 PM
We had a Blake in our toolroom but the primadonnas were pretty much the only ones that used it. I never tried it, just relied on my trusty Starrett Last Word like I had for years.

Now that I have been doing some commercial work and there is more often pressure for delivery, I decided to get the Blake. I have not used it much yet because I haven't been taking on a lot of work since I got the Blake but I can see that it will save maybe a minute every time I need to indicate a hole and more importantly it saves me from having to bent my neck around to see a last word.

The Blake was an auction find and I spent around $165 for an indicator lot but it included about 15 other indicators from a couple of Swiss made ones in .001 and .0001, a federal or 2, A couple of starrett sets and more. A real score. I thought the Blake needed service because it felt somewhat sticky but when it turns it is free and works like it should. Score one for the good guys.

Brian

beanbag
11-06-2012, 04:46 PM
Remind me again why it's not faster to just put a center finder (conical tip) in the spindle and jam it right into the hole?

Fasttrack
11-06-2012, 06:26 PM
Remind me again why it's not faster to just put a center finder (conical tip) in the spindle and jam it right into the hole?

The coax is the same speed as the wiggler (and some argue that it is more accurate than a wiggler) but the real advantage isn't for small holes but for large ones. In my rotary head mill, I often find myself setting up to enlarge a circle or center a part with a large bearing pocket, etc. An edge finder doesn't work in those situations. Similarly, I use my coax for centering a cylinder in my mill, since it can trace the outside diameter of a part as well as the inside.

loose nut
11-06-2012, 06:52 PM
I don't have a coaxial indicator but I do have a 3D taster that I wouldn't part with for anything. For centering the spindle on a hole or a cylinder or finding the edge it is fast. Now a punch mark I don't think it would work.

I have a co-axial and a 3D taster and for most jobs I go with the taster and like Black Forest I wouldn't part with, ever.

dp
11-06-2012, 06:58 PM
Remind me again why it's not faster to just put a center finder (conical tip) in the spindle and jam it right into the hole?

Depends on the size of the center finder and the size of the hole.

http://www.youtube.com/watch?v=ZfioLDhBNBQ

gwilson
11-07-2012, 07:35 AM
The Starrett Last Word indicator is cute,and I have a few, BUT,it is not sensitive enough for high precision work. Takes too much force to move the tip. If you were using it to center holes,you were not getting as accurate results as the Blake would give.

John Stevenson
11-07-2012, 07:48 PM
http://img.photobucket.com/albums/0903/registered_user/Centring3.jpg

Should have gone to Specsavers. :)

willmac
11-08-2012, 05:40 AM
I have both a Haimer Centro (a good quality coax indicator) and the usual DTI on an arm indicator. The DTI (a tenths indicator) is theoretically capable of finding a centre more accurately than the Centro, but there is no question about which is easiest to use and which gives me the best results - the Centro by a wide margin. The reason is that it allows you to make judgements about centering that are difficult with the DTI. Why is human judgement important? Unless you are working with a ground bore, the surface finish of the feature that you are dialing in has an effect that is noticeable. With a coax you can watch the dial continuously rather than relying on mirrors and a bendy neck. That allows you to mentally separate the off centre swing from the fuzz. If the feature has any axial marking the same applies. If you have ever used a Talyrond or something similar you will have found the same - you get to the sweet spot where you can see that the indicator movement you have left is not periodic with the rotation. This is hard to do whilst swinging a DTI around manually and using a mirror.

John Stevenson
11-08-2012, 07:37 AM
Why back to the OP ?

The question has been answer at least 4 tines already. Are you on yet another trolling expedition or like to see your name in print ?

A.K. Boomer
11-08-2012, 08:07 AM
Iv actually never seen one of those - was trying to imagine what FT was talking about and could not come up with anything that made sense due to him saying you ran the mill while using it.

Then I see a pic of the dang thing and im still not clear as I thought about something of this sort and then wrote it off due to inherent problems,
So - here's my stupid questions, what kind of speed do you run this thing on? would have to be super slow no or the needle would turn into a blur from bouncing back and forth,,,
and what keeps the entire thing from whirling about and going into an out of balance self destructive mode?
do you always have to have one hand on it? Or does it have some kind of steady that mounts to the stationary quill?
Is there an RPM rating on it? I mean I know the entire thing isn't supposed to rotate but what about the measuring internals and function of the gauge itself?


go easy on me - it's my first cup of Joe this morning and im only half way through it...

Fasttrack
11-08-2012, 02:20 PM
Iv actually never seen one of those - was trying to imagine what FT was talking about and could not come up with anything that made sense due to him saying you ran the mill while using it.

Then I see a pic of the dang thing and im still not clear as I thought about something of this sort and then wrote it off due to inherent problems,
So - here's my stupid questions, what kind of speed do you run this thing on? would have to be super slow no or the needle would turn into a blur from bouncing back and forth,,,
and what keeps the entire thing from whirling about and going into an out of balance self destructive mode?
do you always have to have one hand on it? Or does it have some kind of steady that mounts to the stationary quill?
Is there an RPM rating on it? I mean I know the entire thing isn't supposed to rotate but what about the measuring internals and function of the gauge itself?


go easy on me - it's my first cup of Joe this morning and im only half way through it...


Good questions! I've seen the maximum RPM stated in print to be 800 rpm. That seems way too fast for me, though. I run mine at a max of ~ 350 rpm. The slower you go, the better the results in my experience. Typically you eyeball the center and then turn on the mill. The needle whips back and forth pretty quick, but not too fast to see. Basically you just move the table until the motion of the needle is minimized. I don't worry about trying to actually read it. Once the movement of the needle is minimized, then you can start making little tweaks until the needle doesn't move at all. That whole process goes very quickly, actually.

To keep the body of the indicator from spinning, there is a metal rod that screws into the body and is perpendicular to the axis of rotation. This rod is set to rest against something stationary to prevent the body/dial from rotating.

At about the 50 sec mark in the video that DP posted, you can see a thin black rod that is resting against the column of the mill to prevent the body of the indicator from spinning:

http://www.youtube.com/watch?v=ZfioLDhBNBQ

A.K. Boomer
11-08-2012, 02:50 PM
Thanks FT - clears up allot of stuff for me - kinda a crazy contraption but yes could see it being much faster than the typical quill mounted dial and careening ones neck all around the place then getting out the mirror and such...
still - that's got to be one light little responsive dial and tons of gears and wear and tear you would think (not to mention the ball feeler wearing out flat in short order or if not running a mild groove into your work material?)

yes 800 rpms sounds crazy, wonder if they should make them with a reduction gear package - you run your mill on low speed and then it gets reduced way down from that... then they could even lighten the load on the ball feeler and all the stuff related. well - if it works it works and you would know so cool... and thanks for explaining...

willmac
11-08-2012, 02:57 PM
The Haimer Centro uses a stop rod like a telescopic radio aerial. You just pull it out and let it rest against something convenient. As far as speed is concerned, low speeds are fine - in fact with mine I always do the coarse adjustment by turning the spindle by hand until I have got it close, the start the spindle and make the final adjustment looking for the cyclic swing of needle until you get down to the noise. Very fast to use and very accurate. It is also one of those tools that makes you feel good when you take it out of the box. I'm sure you know what I mean.

A.K. Boomer
11-08-2012, 03:12 PM
It must be one of those "need to use to understand" as far as the speed thing goes cuz it sounds chaotic to me.

oh well - long as you keep them away from the two stroke bores I guess :)

Fasttrack
11-08-2012, 04:42 PM
It must be one of those "need to use to understand" as far as the speed thing goes cuz it sounds chaotic to me.

oh well - long as you keep them away from the two stroke bores I guess :)


The needle doesn't really swing that fast. The dial is nothing more than a normal dial indicator that measures the vertical displacement of a rocker, so there really aren't any more gears than there are in a normal dial indicator. The only different part is the rocker mechanism. If the part you are centering is centered on the axis of rotation, the rocker doesn't move. If it isn't centered, it moves the rocker and the indicator indicates the vertical displacement of the mechanism.

I'm doing a crap job explaining this ... but it really isn't that much different than centering with a plain old DI or DTI. Keep in mind that these aren't actually measuring anything - they are just indicators. The distance you are from being centered, as indicated on the dial, is a function of the length and angle of the feeler, so the numbers don't really "mean" anything. You just move the table until the needle stops moving. ;)

A.K. Boomer
11-08-2012, 09:31 PM
Right no more gears but a few more pivot points and such,

but still - working the daylights out of them esp. at first when the bore is off from center no?

their recommended 800 rpm's is whipping that needle back and forth over 13 times per second, and all the gears and other stuff...

not to mention the ball feeler, I mean spend a half minute doing your thing and you have 400 spring loaded passes across your bore, really? do they tell you to use it with lubrication or what? its kinda a strange tool, what happens if a bore is a little oval ? How do you center then if the needle never improves...
I can prove it's oval with a conventional and tell you how much and tell you in what direction - all this can be diagnostic depending on what your working on, sometimes I don't like shortcuts and in this particular instance I think it may be one of them,

But ------- I could see it coming in real handy for certain types of production work though...