Member postings for Dinosaur Engineer

George,

answer is same for screw cutting . To accurately form the top & bottom radi with a hand ground single point tool is a bit problematic. Using a full form carbide tool makes life a lot easier. Most turners would just stone off the hand ground sharp tool tip & round off the top of the thread form tips with a chaser or small file. It is possible to use a tap as a chaser. If you have the 1/4 BSP tap then this is ideal to use as the chaser.

It is permissible to substitute a flat instead of a radius at the top of the threads as this doesn't affect the thread strength to any significant degree.

It would make sense if you haven't had much screwcutting experience to read Martin Cleeve's screwcutting book before starting.

George, you are correct, O.D. is 0.518 for a parallel thread ,

Depth of cut is 0.6403274 divided by 19 = 0.0337.

Top & bottom thread form radius is 0.1373292 divided by 19 = 0.0072

I guess you are cutting this with a die rather than screw cutting on the lathe.

Tried to remove "smiley" from my post without success. ! ?

If you search on Ebay for "slip gauges" you will usually find second hand sets for about £40.They can be made from ceramic or tungsten carbide as well as the usual hardened steel. The big advantage of the carbide or ceramic sets is that these do not go rusty. Sizes can be from 0.020" to 4" on the imperial sets. Normal sets start from 0.100".

The usual sectional size is about 9mm x 35mm but gauges blocks can be square (made by "Precise" ).

Slip gauge prices have reduced a lot over the years. I remember the early sets were over a £1000.

Length standards have not changed much over the last 70 years and slip gauges are still widely used as the reference standard.

A set of slips will last a few lifetimes and will not depreciate in value if they are not abused.

Edited By Dinosaur Engineer on 30/10/2014 13:42:04

Edited By Dinosaur Engineer on 30/10/2014 13:42:35

Edited By Dinosaur Engineer on 30/10/2014 13:44:06

Edited By Neil Wyatt on 30/10/2014 16:38:08

Have now ordered some clock oil. Many thanks for the replies

Just a thought - my question begs the question - when should we clean our micrometers and re- oil ?

John,Many thanks for the reply. I was going to use 3 in 1 oil but wasn't sure if it evaporates in time. I'll give it a try.

I have a set of vintage Reed small tool works micrometers (1940's /50's ?) , 6 in total from 0-1" to 5-6" . I am in the process of cleaning them before checking out the calibration. What's the best lubricant for the spindle threads ?

.I have a good set of OPUS carbide slips to do the calibration.

A work colleague had two pieces of metal about 300mm x 150mm x 80mm . One piece was aluminium alloy and the other pure tungsten.. He would throw the al. piece in the air & catch it and then hide it in in his desk drawer . He would then bring out the tungsten piece and place it on his desk top without any body noticing the switch. Sometimes visitors who saw the al. piece throwing and then seeing the machined tungsten piece on his desk would idly try to lift it up. Their reaction was often hilarious. When the visitor was leaving. the trick would be repeated whilst the visitor could still seeing the throwing action - all good fun !

Any amateur (or professional ) model maker / machinist/engineer will at some stage ,have to read and understand 2D drawings . After all it is one of the most important basic international communication channels between engineers. If a drg. is made to recognisable standards then it can be read by any engineer in any country ( with some translational and eng. standards info as required) . It doesn't matter if it's in english 1st angle or ISO 3rd angle as long as it is correctly identified. Parts can still be made from drgs 100s' of years old.Most drgs I've encounted could be read as long as they are clear and to a recognisable format and is made by someone with a little common sense and have been checked by a professional.

To fail to try and understand drgs will make life quite difficult in this engineering world of ours for anyone in this hobby.

There many books on the subject from the most basic to the most advanced. Perhaps a list of these books could be compiled for the benefit of forum members ?

It's a great shame that technical colleges do not run engineering drawing classes ( & CAD courses) that are affordable.Some of the current CAD course fees seem excessive.I would have thought basic classes in eng. drg. & CAD would have rated more highly than some of the "media" studies that seem to offered by a lot of the current colleges, and these engineering courses should be Government subsidised as part of the support to industry. It could be argued that free engineering courses/ classes would benefit the country . Of course some colleges would have to spend money on new equipment to replace the perfectly servicable equipment that they sold at a fraction of their true worth when they decided they were no longer needed !

I have noticed some poor practice in current ME/MEW drgs where shaft / hole diameters are dimensioned from end views using arrow headed leaders to the circ feature. Where there are a number of shaft stepped diameters and maybe stepped holes it is quite difficult to discern which diameter the dimension refers to.These dimensions may be clear to the contributor when viewed on a 24 inch monitor but are not clear when printed in the magazine. It's quite acceptable to place a dimension across the drg to the relevant diameter rather than extend the dimension outside the item outline in order to make the dimension more clear.

My pet hate on some 3 CAD programmes is that sometimes it's difficult to change some of the 2D semi-automatic drg defaults to make some aspects more clearly defined. There are ways around this but it involves extra work !

The importance of good drgs & CAD models becomes very clear when drgs / files can be sent across the internet and can be immediately viewed & understood & used by the recipient.

It has been mentioned before on this forum that a perfectly good free 2D drawing program can be down loaded from the Solidid Ege website

Edited By Dinosaur Engineer on 23/03/2011 20:16:53