run out on 3 jaw chuck

I bought myself a metric 0-10 mm dial gauge (nothing fancy) so i thought i'd check my chucks run out and the gauge read ... 0.05 = 1.968504 thou 3 times . Thats not bad is it's. The spindle was less it was between 0.0.2/3 . I'm planning borrowing a small hydraulic ram piston from a mate and use it as a test for my tailstock for trueness to the chuck ,he uses it on his lathe and is very confident on how accurate it is .... How trust worthy would the dial gauge be . I have an old Baty dial gauge in a wooden box ,but it feels like the plunger is going through thick oil . I've tried to take the back off to clean it but i can't figure out how to . Any ideas ....

Sean

Sean, try leaving the Baty in a pretty warm place for a day, this will help free up any old congealed oil that has entered the spindle, not aways a good idea to apply oils to the spindle.

Emgee

Hi Sean, Usually 3 screws holds the back plate on. Take the back off your old Batty and sit it in some clean kerro [ do not submerge the dial], let it soak for 24Hrs occasionally operate the plunger then let it dry out until all Kerro has evaporated do not blow it out. This should free things up unless there is mechanical damage.

Do not re lube with oil unless you have watch repair oil.

Set both gauges up to measure a known item and compare readings.

Garth.

Before you pull the back off the dial gauge and possibly upset things, try a couple of drops of petrol on the plunger where it goes in and out. It might just free up the congealed oil on the plunger and do the job. As recommended on an old Mitutoyo dial indicator service sheet I dug up somewhere.

That said, the best test for tailstock "trueness" is to turn a test piece between centres (no chuck) and measure teh taper with a micrometer. That is a test under operating conditions in the "real world". You can save a bit of time by rough turning the test peice to a dumbell shape and then taking a fine cut across the large diameter at each end without altering the cross slide setting.

Also note that tailstocks are often manufactured to sit a thou or two above the true centreline of the headstock spindle to allow for wear on the tailstock base and bed ways over the years.

Think here. It is likely stuff, contaminants, crud, dust, grease, etc that has got into the plunger area. I suggest cleaning that out before dunking the whole lot in anything.

There are no screws on the back ,i wonder does it screw off ? I should add that the gauge is a back plunger style 

sean

Edited By sean logie on 01/12/2016 19:11:20

This might help Sean.

Thanks

I've now uploaded photos of the Baty dial gauge .

Sean

Now you have clarified the type of instrument I would take a guess that access to the internals is through the front.

Remove the clear cover then the indicator needle then the scale gives access to screws holding the front plate on. However unless you are an instrument repair type I would not recommend you do this your self.

.

Looks like thousandths of an inch to me, Sean

**LINK**

http://www.model-engineer.co.uk/albums/member_photo.asp?a=42979&p=708108

MichaelG.

Set it on your bed and turn the lead screw one or more turns, noting the deflection. As long as you know your lead screw thread, or are able to measure same, you can easily work it out for yourself.

Each graduation is .001"

Tony

I agree; like what it says on the dial.

Andrew

You might like to check the run-out on different diameters of bar. If the chuck has been used a lot at one size then this may have affected the scroll, and so you could get very different concentricity at different sizes. There is not much you can do about this, but at least you will be aware that some sizes of stock are likely to be more iffy than others.

In case anyone else doesn't know what kerro is, it is what proper British English speakers call paraffin, and many others call kerosene. And although paraffin, in this sense is a liquid, it is nothing like 'liquid paraffin'. Alternatives to kerro include 'white spirit', and 'turps sub' (=turpentine substitute).

What happened to our glossary, I wonder?

Cheers, Tim

.

I suspect that the [multitudinous] definitions of a handful of terms would fill a book.

... and if web-based it would become Pandora's Box of hyperlinks.

MichaelG.