Colchester chipmaster dual dials

[AdamParticipant @adam]

Hi everyone. I have a Colchester chipmaster I recently acquired and I measured the distant on the slide with respect of the dual metric imperial dial. It says one revolution is 400 thou but it’s actually half that.
Is this normal?

[AdamParticipant @adam]

[Bill Davies 2Participant @billdavies2]

Hi, Adam.

Assuming the cross slide, the dial movement indicates the amount removed on the diameter. Half off radius (actual slide movement) equals amount off diameter.

Bill

[MuzzerParticipant @muzzer]

Yes – it takes 400 thou off the diameter, which is often what you want on a lathe.

Murray

PS – I've never checked on my Bantam but I assume the compound / top slide is different ie direct reading, as it could move at any angle to the axis.

Edited By Muzzer on 24/06/2018 21:55:40

[John MCParticipant @johnmc39344]

My Chipmaster has dual dials, takes 400 thou off diameter. While the imperial dial is accurate the metric is not. If I zero the dial in "thous" then the cross slide will consistently return to the zero position, checked with a DTI, zero on the metric scale is inconsistent. Anyone else noticed that? I tend to use the DRO so not a problem, would be nice if it was accurate on both scales.

My Triumph has dual dials fitted, absolutely consistent in both ranges.

John

[AdamParticipant @adam]

Of course!! It’s diameter!! This is my first real lathe so I’m still learning. I guess we all start from somewhere. Thanks for the responses. No doubt I’ll ask more easy questions later.

[SillyOldDufferModerator @sillyoldduffer]

Posted by Adam on 25/06/2018 10:15:48:
Of course!! It's diameter!! …

No 'of course' about it. Traditionally British lathes measure depth of cut. Measuring diameter (which I find more natural except when cutting threads) is a beastly American innovation circa 1890.

My Chinese mini-lathe dial measured depth, it's big brother measures diameter. Not much consistency in the world of lathes.

Always worth double-checking before using an unfamiliar machine.

Dave

[Ian S CParticipant @iansc]

My Taiwanese Lathe indicates diameter, and I got trapped when I did some work on a mates Myford 7 that indicated DOC. I'll have to check the Menzshed Boxford A, the dial is tiny, and not easy to read.

Ian S C

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