Member postings for Darren Conway

Hi

If someone buys the lathe for the purpose of using it, it doesn't actually matter if it has been out of the box before. It still appears to be as new.

That sort of money will buy a much more capable lathe here. New Chinese/Taiwanese or alternatively used. I paid about 30% less for a Nardini MS350 lathe in good condition (ex South African University research lab) that will turn 350mm dia, 1m between centres.

It is very difficult to find good used machine tools here. Any light industrial tools have had all their life fully expended. Ones accessible to students have often been abused. There is only a small population here in a small country. It took me over 3 years to find my first lathe (Denford) and about 7 to find the Nardini.

Dazz

Hi

I thought there might be some interest in this.

Back in the 1950's the New Zealand government made it very difficult to import things like lathes. It was really difficult to get foreign currency. Import licensing gave companies monopolies and their prices reflected that. There was no internet to find things.

When someone was able to import a lathe, they made sure they got all the accessories. It was far too difficult and too expensive to go back and get extras. So it is with this lathe.

A lathe like this at that time was so expensive and so difficult to obtain, it was almost too precious to use. As a result there are a reasonable number of good Myford lathes here with plenty of factory accessories.

This one is exceptional because it is still in it's original crate. I can't tell from the photos whether it has been used or not. I don't see any chipped paint. The listing says it is unused.

It is on auction here at this website: **LINK**

See the album for more photos.

The error table relates to the precision of using a turned measured step and the top slide offset to measure the absolute angle of the taper set . The piece of grubby key steel and scrap wood is used for relative measurement of the top slide angle. Both methods are applicable to different applications.

Hi

It's early June and I finally received the magazine with my article. The formula submitted in the article is:

asin(d/D) -asin((d+e)/D)

Where:

e : the measurement error

D : the large radius of the taper

d : the small radius of the taper

The total "Mean Square Error" is simply the square root of the errors squared.

Darren

Hello

The mean square error in the table is simply the square root of the errors squared. Like many things in practical engineering, it is an approximation. In this case it is an approximation of the actual error. The purpose of this table was to illustrate that the angular error is tiny and that is all. If I was writing a math exam or an academic paper, I would have taken a different approach.

I intentionally avoided using or describing detailed statistical techniques in an article focused on practical workshop techniques. It wouldn't matter what error calculation was applied, the estimated error would be small. As it says in the article, the calculation is an estimate of errors, and that is sufficient to illustrate the point.

I am quite flattered that the article has been so closely scrutinized. At least it tells me that some found it worth the time to read. Forums like these are great for sharing knowledge, sounding out ideas and for providing constructive feedback. I hope you all enjoyed the remainder of the article.