Defective Verniers

I have been making a simple set of drip feed oilers for my Flexispeed to save constantly dripping oil into the headstock bearing oil holes.

The first one went well, with a simple, push-fit lid that pulls off with a satisfying "pop". A while later, I made the second and two ill-fitting lids later, wondered why I could not turn the lid to fit at all.

Having used a dfiferent set of verniers, I decided to check their accuracy, out of curiosity. Using the inside jaws to measure the bore of the oiler, I then measured the corresponding gap on the outside jaws: different, by a fair margin.

No wonder the lid did not fit. I shall consign that pair of verniers to the junk cupboard.

Regards,

James.

Worn internal jaws or sloppy slider adjustment or poor quality?

Or dropped

Something to be aware of: A vernier caliper will probably not give a precision result on a hole diameter due to flats on its measuring face. Colin

Good point, my verniers have sharp edges, the electronic one (seldom used) has an edge about 1mm wide. Never noticed before.

For getting fits just right in small bores, and to avoid the vernier caliper tip flats issues referred to above, a purpose-made custom gauge can be quickly turned up from a scrap of free cutting steel. While making it, the outside measuring jaws of the vernier caliper can be used to get it to the desired accurate diameter. The gauge is then used to check the progress of the boring or lapping ops to get the fit of the bore just right, by frequent testing in the bore. Always stop the machine completely before trying the gauge in the hole. JD

The gauge recommended by Jeff is the best way to go and can be made user friendly by having about 2mm turned to 0.002" undersize so you know when you are "nearly there". Yes, I do think both metric and imperial dimensions can usefully be mixed ! Colin

The "nearly there" step diameter is a smart idea Colin, thanks for mentioning it.

+1 on mixing the units whenever possible! it keeps the inflexible on their toes....

JD

I have both manual & digital "Verniers" (e.g. callipers) and use them all the time - especially for anything quick and 'dirty'.

But for real accuracy when measuring diameters (or bore gauges for instance) I use a micrometer - it's much better practice in my view.

Regards,

IanT

Thank you for all of the replies.

I can confirm that the verniers are old, cheap and, having had a good look at them, worn, with the jaws wobbling a fair bit. They were the first pair that came to hand last night, but I had not realised their condition. I have a digital set (Silverline or similar) and a manual set (Mitutoyo), so shall stick to those in future.

I like the idea the "plug" gauges and can see me using that idea on other things.

Regards,

James.

Ditto except my callipers that I use for quick and dirty measurements are mitutoyo absolutes. I use mic's for anything that matters because they are far more reliable in terms of accuracy.

For measuring bores with callipers the old style that wouldn't measure below a certain size where the internal jaw width had to be subtracted from the reading are much more reliable than thin edges but are sadly not available on run of the mill ones because they aren't really intended for taking very precise readings - especially that way.

John

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Edited By John W1 on 16/09/2015 23:26:53