Center finder suggestions for a rookie?

H

heliyardsale

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Looking for advice, something I can use with my Bridgeport and Sherline mill. For big holes I'm guessing a dial gauge on some type of holder that goes in the spindle? How do the Starrett wiggler sets work? How large of a bore can they center?
 
I have just used a DTI in a collet. Center the spindle over the hole by eye, then bring the indicator tip into contact. Rotate the spindle (by hand!!!!), and adjust X/Y until there is no variation. It can get a bit cumbersome reading the dial when it's facing backwards; some people use a small mirror. For larger holes you could make a longer arm to hold the DTI.

Of course, if you have money to burn, or you do this sort of thing enough to justify the price, you could buy a co-axial indicator.

http://www1.mscdirect.com/cgi/NNSRI...re=ItemDetail-_-ResultListing-_-SearchResults
 
There are a couple of other tools for doing the job as well. A couple of them are pretty easy to fabricate yourself. There is the Indicol holder which attaches to the spindle without having to remove your tooling first ...

jpg.indicolmodel250ii.jpg

as well as a couple different designs of a "zero-set". Here's one made by one of our members - http://www.hobby-machinist.com/showthread.php/9655-Zero-It-Indicator-Holder-Finished

ZeroIt_1.jpg

You can also look up a Noga-flex. It's a simple articulated arm that can mount in the spindle using a collet...

312WdVnm1YL._SL500_AA300_.jpg

Lots of options.

-Ron
 
I ditched my indicol & replaced it with one of those Noga NF1018 holders, couldn't be happier. But like Ron mentioned, the indicol allows you to hold an indicator without having to remove the cutting tool from the spindle.

Another option is to use a co-ax indicator. Some like em, some hate em, but they can be ran with the spindle under power & would account for any spindle runout if it was an issue.

Blakes will cost you but there are less expensive imports. I only used an import one a few times a while ago so I'm not sure how they compare to a Blake that I have now. But for us home shop machinists I suspect it'll do just fine.

Fowler & SPI also offer them.


If the bore is large enough, you could also just use a typical edge finder to locate center or a wiggler as you asked about.
 
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