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oldtiffie
01-27-2008, 04:37 AM
As I was "on a roll" with copying and posting to Photo-Bucket as of late, I thought I'd cover "screw threads" while I was at it.

There is a lot of information, mis-information and vast numbers of different tables etc. for the screw threads used in a typical HSM shop.

I have an explanation of the profiles and details of screw threads as well as tabulated sizes and drilling and tapping sizes etc.

It is from a metric book which covers both "Imperial/Inch" and "metric".

Conversion factors are:
- mm/25.5 = inch
- inch x 25.4 = mm

For "day to day" conversion use "25" instead of 25.4.

I have inserted the links to the files so that I don't have to "pi$$" some off by so many down-loads of images.

The images on the screen will be a bit poor at first, but just put the mouse cursor/icon onto the image and when the "expand/contract" icon comes up in the bottom right corner of the image and just "click" it and all will be OK.

Down-loading them to your computer will help too.

Perhaps someone will "pdf" and "host" them.

I hope this helps.



http://i200.photobucket.com/albums/aa294/oldtiffie/Screw_threads/Screw_threads1.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/Screw_threads/Screw_threads2.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/Screw_threads/Screw_threads3.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/Screw_threads/Screw_threads4.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/Screw_threads/Screw_threads5.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/Screw_threads/Screw_threads6.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/Screw_threads/Screw_threads7.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/Screw_threads/Screw_threads8.jpg

Walter
01-27-2008, 08:46 AM
I PDF'd them, it can be had Here (http://www.blackrogue.net/Screwthreads.pdf)

Lew Hartswick
01-27-2008, 11:54 AM
I didn't see any mention of helix angle. For grinding single point threads
that is a factor that must be considered.
I did copy the pdf. and will print them out for use at school .
Thanks.
...lew...

Paul Alciatore
01-27-2008, 01:19 PM
Useful information, but you do realise you probably violated a copyright by copying and posting them.

As for the 25 instead of 25.4 conversion factor, that is the same cheat the Chinese mill makers have made on the spindle down feed of their machines. It produces an error of about 0.016" per inch. Not trivial in my opinion but whatever you want. I have made a table of conversions to keep near the mill for more exact work.

oldtiffie
01-27-2008, 05:32 PM
I didn't see any mention of helix angle. For grinding single point threads
that is a factor that must be considered.
I did copy the pdf. and will print them out for use at school .
Thanks.
...lew...

Hi Lew.

I am glad it was of use.

The "helix angle setting" was addressed in the links in my post "Multi-lead threads on the lathe" at thread:
http://bbs.homeshopmachinist.net/showpost.php?p=329771&postcount=14

The specific links are:
http://i200.photobucket.com/albums/aa294/oldtiffie/Thread-cutting_lathe/Thread-cutting16.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/Thread-cutting_lathe/Thread-cutting17.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/Thread-cutting_lathe/Thread-cutting18.jpg


All of these links are in a pdf file as advised at:
http://bbs.homeshopmachinist.net/showpost.php?p=329995&postcount=21

I hope this helps.

oldtiffie
01-28-2008, 02:52 AM
..........................................
.......................................

As for the 25 instead of 25.4 conversion factor, that is the same cheat the Chinese mill makers have made on the spindle down feed of their machines. It produces an error of about 0.016" per inch. Not trivial in my opinion but whatever you want. I have made a table of conversions to keep near the mill for more exact work.

We have no problem here in OZ at all with "metric", "hard/soft conversion", preferred sizes etc.

Lengths of steel are in multiples of 300mm (a "metric foot" if you like), widths, thicknesses and diameters are in multiples of 1, 3, 5, 10, 20, 25, 50 and 100mm

Works fine.

I have 2 Chinese mills, a lathe, T&C grinder, surface grinder etc. and all are metric. The down-feed on my mill is exact - metric modular worm and wheel. I've checked with my DI etc. - no problems.

Many Chinese machines have a metric lead-screw with a "rough" guide/indication to inch measurements.

In Australia, most of us older people have no problems with dual systems.

Most of the younger brigade know nothing but metric.

But all of that is OK.

We can still buy Inch/Imperial metal and nuts, bolts etc - both USA and UK.

Most of the rest of the world other than the USA is metric - or heading there!!.

rantbot
01-28-2008, 07:40 AM
Conversion factors are:
- mm/25.5 = inch
- inch x 25.4 = mm
Might want to fix that "25.5". The conversion factor is exactly 25.4 both ways, of course.

oldtiffie
01-28-2008, 07:46 AM
Might want to fix that "25.5". The conversion factor is exactly 25.4 both ways, of course.

Thanks rantbot.

Done - see post#1
http://bbs.homeshopmachinist.net/showpost.php?p=330011&postcount=1

My silly mistake.

IOWOLF
01-28-2008, 10:31 AM
I have a question,Why do we need 2 threads that are pretty much the Same topic?

Coud it be some Grandstanding?

miker
01-28-2008, 05:03 PM
There are a lot more than two threads!
ISO Metric,BSF, Whitworth, UNC, Trapezoidal, Wormthreads, ACME (where would Wily Coyote be without ACME?), Butress etc.
We need to know about them all for a well rounded education.

Not sure about the threads used to construct Grandstands though! Maybe some one can add that info.

Thanks for going to all the trouble oldtiffe. Much appreciated.

Rgds