What is the correct way to use & function of a coaxial centering indicator?

[ome]

Hi all, how & when to use coaxial center indicator.
I have a new one, just an import, but looks decent.
I have my grizzly mill and a 8 inch rotary table with a center hole.
I also could use a good way to find the center of a hole of a part to be milled.
Any help thanks in advance.
Thanks
jon

 

[marcaap]

I'm a newbie, so instead of telling you something incorrect, I'm attaching a YouTube video of Keith Fenner using a coaxial center indicator. The action starts at 27 minutes and 30 seconds.

http://youtu.be/lWrztk4aBII

Hope this helps until the experienced folks get a chance to chime in
Paul

 

[Philco]

Tom G has a good video showing how to find the center of a hole in a part.
http://m.youtube.com/watch?v=v_tpKP_kJSA
Hope this helps.
This is a video on how to center a rotary table
http://m.youtube.com/watch?v=GjezShYnoEU
I know these videos did not answer your question on how to use the coaxial indicator. I'll try to make an attempt to explain it.Once you get the coax mounted with the proper tip for the hole, do a trial run with the indicator tip above the hole. Start the machine @ low rpm & move the X & Y to get close to center by eye. Once you get close by eye, insert the probe & finish up by moving X & Y until there is no movement in the indicator.
Maybe some of the more experienced coax users will chime in with a better description.

 

[KMoffett]

Google: coaxial center indicator youtube

Ken

 

[flutedchamber]

The slower the RPM, the easier it is to get things perfectly centered, at least until you get accustomed to the tool, then you can raise the speed.

 

[cwolfs69]

The slower the RPM, the easier it is to get things perfectly centered, at least until you get accustomed to the tool, then you can raise the speed.

i actually find that a llittle higher rpm makes it easier for me. the indicator doesnt seem to jump as much and gives a smoother reading.

 

[george wilson]

Just be real careful to not try to start the indicator in a hole that is too far off center,and is beyond the travel of the unit. I saw a broken off Blake(real) unit in a professional machine shop that some ham handed "machinist" had snapped the shaft off of. Ruined the unit. I also only use low speed with my Blake. It gives a more accurate reading,and jars the indicator less. Internals can break on any indicator,and the needle can fall off too. I try to keep wear on the unit as low as possible.

 

[Pacer]

As mentioned, try to center the spindle as near as possible before using the indicator. Since the shaft on the indicator is 3/8" I ground a broken 3/8 end mill to a point and I put this (or anything similar) in the collet and lower the spindle near the hole and "eyeball" the center, you can get surprisingly close this way... Then install the indicator and you should be able to quickly get dialed in.

 

[ome]

Just be real careful to not try to start the indicator in a hole that is too far off center,and is beyond the travel of the unit. I saw a broken off Blake(real) unit in a professional machine shop that some ham handed "machinist" had snapped the shaft off of. Ruined the unit. I also only use low speed with my Blake. It gives a more accurate reading,and jars the indicator less. Internals can break on any indicator,and the needle can fall off too. I try to keep wear on the unit as low as possible.

Thank You very much,
jon