Member postings for Jim Gardner

David,

It's reduction of diameter. The error isn't 50% but it is enough to be a problem.

Posting in Beginners questions because I feel like the whole planet knows the answer to this except me.

It is not that often that I have to make a nut or bolt, but today I had to made a 1/2" Whitworth bolt with left handed thread. Obviously I turned the OD to .500, changed the gears in lathe to enable 12 tpi, looked up the thread depth (and Googled it twice) and cut to a depth of 0.055" which is 0.001" under size. The compound was at 29 degrees, depth was measured using a dial gauge. Everything seems to work perfectly.

I took the new bolt out of the lathe and,,,,it wasn't even close to having enough thread depth (at a guess I would say I should have cut another 8 thou. This seems to be the result I get time after time. I do believe I cut to the "correct" depth, but it is never enough. Even my 80 year old engineer mate who has been thread cutting all his life tells me to always go deeper.

Can any body tell me why>

Bizibilder Thank you. I know I will spend an hour checking that against my maths now!

Thanks everyone for the very speedy and informative replies. I may download some tables but Rob Cox put it in a way very easy to understand, so I will probably use maths.

First project will be a 1/2" Whitworth left hand thread bolt. Coincidentally the 5C collet blocks I ordered to make a hex head arrived today, but I am now determined to use the DH.

I have just noticed some replies to this post show on my phone, but not on my laptop.

I posted yesterday about a dividing head I wanted to get back in working order. It needed a part mending and a couple of other bits locating or making. This is now done and it is ready to use.

It was suggested in the replies that for tables, I would need to know the maker because table are specific to the unit.

I had assumed that tables for a DH with 40:1 reduction ratio would work for all dividing heads using the same ratio.

As I have never used one, could someone point me in the right direction for tables please?

Many thanks.

Lets see if the advice Frances gave works for me.

Many thanks for all replies so far.

Unfortunately there is no makers name I can see but I assume reasonably old. As for how big, what is used as a reference for DH size?

Due to its age and not having been used for at least 25 years, and to clean it all up so I can use it, I decided to strip it. Unfortunately I found the "brake" is broken. Without a makers name, how would I go about getting spares?

I have brazed it just now but not sure how strong it will be. Sorry for the almost certain incorrect terminology.

Re the indexing/selector arms, I will try and find a wavy washer first but make a brass one if not.

Yes I do have the handle/pin and 3 plates.

I have photos I would like to post but can't find how to do that despite trying hard.

Thanks again.

Jim.

Hello, I have been using older machinery (Colchester Bantam, Bridgeport Mill) for quite a few years but only to carry out very basic operations. I now find myself both needing and wanting to do more with them -and other equipment I own but have never used- so I am trying to find out and learn what I can.

I have just posted a question about a dividing head on the General forum and I am looking forward to seeing what people think.

Obviously if I can answer anyone else's questions I will.

Jim.

Hello, I am new to the group today so will be heading to the "introduce yourself" page shortly. I find myself here because I am about to use an old dividing head for the first time but immediately ran into a problem.

The brass indexing arms fit over the centre shaft but there is nothing to provide any tension/friction to keep them in place. The shaft has what could be a circlip grove in it approximately 1mm out from touching the arms, so I am assuming there is a brass? washer type piece that presses against the arms to stop them spinning freely.

Could someone tell me what pieces are missing please. I.E brass shim or spring or something I haven't thought of?

Many thanks,

Jim.