Thread: Treasures from the shed III

Hi Michael,

Very nice! I'm curious as to how the gear tooth vernier works, do you have any links showing how it works, by that I mean exactly what does it measure?

Regards
Ray

This is a reasonable illustration - you are measuring the tooth thickness at the PCD, so the poorly spelt vertical scale is set to the addendum (a_c in this diagram) and horizontal scale measures the tooth thickness (t_c). As mentioned, there are corrections involved as you are measuring a chord rather than a section of the PCD and so on.

Michael

Originally Posted by Michael G

A few days (weeks?) ago someone mentioned measuring small forces. It may have been in conjunction with indicators and measuring plunger forces - anyway, this is one way to do it. (NB that is a cm scale in both pics) Would have posted this earlier but...*
This is a Correx force gauge, Swiss made. The most common use for these in the past would have been measuring/ checking lift off forces on relays + slip ring contacts. Now that a lot of switching is done digitally there probably isn't as much call for something like this. This one goes from 10 to 100g in either direction and has a maximum force needle for catching instantaneous readings.

P1010670 (Medium).JPG

Not sure I haven't mentioned this one already, but while making up the worm wheel hob it got used, so it gets a mention now. It's a gear tooth vernier - dated prior to 1950 I think (made in the UK). These days digital versions are available but an old vernier scale instrument is a thing of beauty. Finding one was hard, as there are a lot around for 2DP to 20DP but this one is sized for 4DP to 40DP; more my sizes. They are used for measuring tooth thickness. The vertical scale is for setting a moveable stop and the horizontal scale is for measuring the tooth thickness. There are corrections applied to the measurements to allow for gear and tooth size as these will change the reading slightly.

P1010675 (Medium).JPG

Michael

*It was decided that we had to "get away for a few days". Funny how I can't take my shed with me but the books, crosswords and knitting are fine.

You should buy a Taig mill and lathe Michael. How did the knitting go? Make somefing useful?

Dean

Those gear tooth verniers are as rare as rocking horse doo - doo. Measuremax sell a new version for not a lot of money.

https://www.alltools.com.au/shop/ind...er_1-26_Module

They are a really handy device for measuring form tools for Acme or Trapazoidal tooling. Just set the vertical scale to the mean diameter of the tread, and then you can measure the width of the tool. Real handy if you don't have a profile projector.

Regards Phil.

Why pay a Perth price - Gear Tooth Vernier Caliper M1 26 | eBay

I can't work why it has been specified like that - M1 is useful; it's equivalent to a DP of 25.4. M26 would be the equivalent of 0.97DP - that's a seriously large gear. Not as well ranged as it could be for most people who might buy one*. Myford gears are around 22DP (I think); Colchesters 14DP(?) but there's a lot finer out there (metric on the CVA is 32DP).

Michael
*The important thing is not the scale but the jaws - they have to be small enough to get in between the teeth. I would have voted for something like M0.6 to M4.25 as a good range for someone who cuts the occasional gear. I doubt that full time gear manufacturers would have anything as basic