it seems some people don't get...

[bhjones]

the whole concept of an open forum.

Yesterday I made a post asking about the calculation of divisions when creating a vernier scale.

http://bbs.homeshopmachinist.net/showthread.php?t=29789

I made the post thinking I'd get a few ideas, pick up some theory and with any luck I'd learn something. A side benefit to these open discussions is that others can learn a little something while the thread is active or search through the archives later on. It's really a wonderful system.

While this thread was active I received a PM from member DJC informing me I was incorrect. Here is the PM:

####
> Let's say my cross feed dial has 100 divisions total. If I
> was to add a vernier to the system I'd space the divisions
> so that 10 marks on the vernier would fit within 9 marks on
> the dial. That would mean my if my dial has 100 divisions,
> my vernier would need to have it's circumference divided by
> 110 (only needing 10 marks).

I think you need to think again. If 10 marks on the vernier is 9 marks on the dial, 100 marks on the vernier is 90 marks on the dial and 110 marks on the vernier is 99 marks on the dial.

The spacing between each mark on the vernier is 90% of that between the spacing on the main dial. The spacing between the main dial marks is 1/100 of the circumference of the dial, so you need 90% of this i.e. 9/10 x 1/100 = 9/1000. Hence you have to divide your circumference by 1000 and mark every ninth division.
####

I responded back with this:

####
http://www.tpub.com/math1/7e.htm was the document that made it click for me. Perhaps I'm not reading it right.
####

Followed by this reply from DJC:

####
> Perhaps I'm not reading it right.

Well, you are correct in this assertion at least. There is nothing wrong in the link you posted.

It is your post that says dividing the circle into 110 parts will achieve a vernier scale that is incorrect.

Look at the link you posted. When the zero on the vernier scale lines up with the zero on the main scale, the one on the vernier scale is 9/10 of the way along the gap between zero and one on the main scale. If the gap on the main scale is 1/100 (of the circumference), the gap in the vernier scale is 9/10 of this, or 9/10 multiplied by 1/100 which equals 9/1000 as already posted.

If you don't believe me, go and buy George Thomas' "Model Engineer's Workshop Manual" ISBN 9781857610000 and read page 178. For your education, I have scanned the paragraph and it's at http://www.desolation-row.demon.co.uk/vernier.jpg

Now kindly post a correction to your erroneous post on the public forum, so nobody else reads it and makes the same mistake. If you don't correct your own work, I will.
####

Giving his point some thought I think he's right, and I'm glad he pointed it out to me.

I only wish he would have participated in the thread while it was active. I also would like to point out to DJC that my "Work" was not work at all, it was a question looking for an answer. I posted what I thought was a solution but was making a mistake in my thinking. Even then, I was questioning my solutions correctness.

Lastly I'd like to point out that threatening people as you did in your closing statement does no good. In fact it simply makes you look like an A55Hole.

Anyway, thanks for the correction DJC and I hope you take a more active part in the forum, it seems like you have something to offer.

[rotate]

PM = private message.

You should have kept it that way. Revealing the content of the PM and the person's handle, however noble your intent may have been, is not kosher.

[John Stevenson]

Brett,
Nothing suprises me, didn't follow the thread but did notice you had 10 replies and there was 21 replies on how to pronounce it

As if there is one correct pronunciation given different countries, accents and the way each of us dress.

Very easy mistake / misunderstanding to make when you transpose two numbers that are close to one another like 10/9 or 11/10 or 10/11 damn now I'm mixed up.

Anyone who hasn't done it will obviously have a scrap bin smaller than mine and that one only holds about 1 - 1/2 tonnes

.

[aboard_epsilon]

Why go to all the trouble.

DRO's are the present technology

OR

Spend half your life re-inventing the wheel or falling out with people. ...or just go with the flow.

all the best..markj

[tattoomike68]

vernier scales also are use in angular measurement like rotary tables, transits and bevel protractors.

In college I used a beautiful surveyors 1926 transit made in brass and cast iron that would read down to 1/2 a second.

My favorite calipers are vernier, my eyes dont see so well now days so I may gets some digitals.

As far a PM just ignore it, if they were so damn smart they would post thier opinion for all to see and be critiqued by the members.

[bhjones]

John, I just wanted to know how it was done for the sake of knowing. I may try making a vernier for my Craftsman crossfeed as a little mental exercise. I'll need to stock up on material first since I'm sure I'll have to make a few before I get it right.

As far as the "private" part of the PM. It seems if you threaten in a PM you loose all claims to privacy.

[lazlo]

didn't follow the thread but did notice you had 10 replies and there was 21 replies on how to pronounce it

Not so fast John -- Bill Pace posted a separate OT thread about the pronunciation of vernier, and even then it was far more apropos than exploding CD's or universal spreadsheets

[John Stevenson]

Yup I know it was seperate and Bill is a member I respect a lot but it did get 21 hits whilst the OP only got 10.
Don't know about the CD or spreadsheet, didn't read either.
I tend to skim a lot these days, the longer you stay on here the more things tend to get repeated.

.

[lazlo]

I tend to skim a lot these days, the longer you stay on here the more things tend to get repeated.

True that.

[Chipslinger]

I am with you on that one also John.