A glossary of ME terms

[Colin Jacobs 1Participant @colinjacobs1]

For us beginners is it possible to have a glossary of terms? ie whats a collett for? what grades of emery do we need to polish metal? Oh you know, all these questions that beginners must wonder what these terms are?

 

 

MTA

 

Colin

 

 

 

 

[Colin Jacobs 1Participant @colinjacobs1]

Whats this?

[BrianParticipant @brian]

What a very good idea Colin, me-thinks this will run and run and run.

 

Brian

[Colin Jacobs 1Participant @colinjacobs1]

So I want to polish my BMS. What grade of emery do I start with and finish with please?

[John CoatesParticipant @johncoates48577]

What a good idea Colin

 

A a newbie I was stumped by collet, reaming, indexing (still no sure about this one, think it means being able to position the workpiece to a known location or rotational position) but having subscribed to MEW for over a year now things are starting to make sense

 

John

 

[Jeff DaymanParticipant @jeffdayman43397]

Colin,

 

For polished mild steel bright finish – Start w 80, then 120, 160, 200, 400, 600 ,800, 1000, 1200, 1600, rubbing compound, polishing compound, jewellers rouge, then wax.

 

For hard tool steels you can go farther, with diamond polish paste C, then diamond B, then diamond A, then wax (and sunglasses). The diamond polishing is effective on hardened tool steels, but the finish will not last on mild steel if in fact you can even achieve polish so don’t bother, for 99.9% of ME work.

 

If you are going to paint the mild steel surface, there is no need to go higher than160 or 200 grit.

 

Collets are work or tool holding fixtures. They are usually cylindrical and have some sort of compliance built in (saw cuts lengthwise or rubber segments are most common) so they can squeeze the workpiece concentric to the collet centre. Usually there is a taper on the outside diameter to help the collet grip, and a thread is often used to pull the collet onto the taper and hold it to grip the work. Collets are usually hardened steel. There are many types of collet for lathes and mills, the common ones being Morse 3 taper, 5C, R-8 and ER. Usually a special chuck is used to hold them although Morse taper ones can be used directly in a matching size MT female spindle on a lathe or mill. When you buy collets you can buy a set of common sizes or individual ones. You can also buy soft ones that can be bored out to suit special jobs, called “emergency” collets. In a lathe collets are great for holding small work concentric to the spindle and they allow good tool access to small work. In mills the R-8 ones are great for holding endmills and other cutters.

 

John, re indexing – your description is very good. I would only add that the three most common indexing methods for ME’s are using a dividing head, using the collet type spin index with dividing plate, and using the bull gear teeth on a lathe to index, in combination with a stop pin or strip. To see pics of the spin index and dividing head use google or try http://www.kbctools.com.

 

JD

[Colin Jacobs 1Participant @colinjacobs1]

Thanks, lets hope the glossary will continue.

 

[DustyParticipant @dusty]

Remember when polishing with abrasive cloth and paper, each change of grade must be at right angles to the previous grade. What you should see is the scratches caused by the previous polishing at right angles to your efforts. When you can no longer see any scratches that is the time to change to a finer grade of cloth/paper. Again at right angles to the way you were working. Polishing round objects is a bit problematic, if you are just polishing and not concerned with maintaining a dimension then just keep the cloth on the move vigorously with the lathe running fairly slow, do not be tempted to dwell as you will polish grooves into the workpiece, you should end up with a figure of eight look to the surface. Change of cloth reverse the lathe. Do not be tempted to start with too coarse a grade of cloth, if it is not coarse enough you will soon see. When polishing do not back the cloth with a file, one slip and you will spend ages removing the file mark. A piece of wood 3/4″ wide x 5/16″ thick and 10″ long, shape the end like a cold chisel, take your cloth and tear it twice the width of your wood, double it over lengthwise and place it over the wood so that one side of the abrasive is against the wood fold the end over the wood so that you have about 2″ you can hold onto. Then start polishing with one of the chisel edges. When the cloth becomes clogged move it to a fresh place.

[Steve GarnettParticipant @stevegarnett62550]

Turns out not to be so easy to find lots of glossaries of terms relating specifically to M.E., but one I found that looks quite helpful is here:

 

Glue-it.com

[TerrydParticipant @terryd72465]

Hi Colin,

 

I’m not trying to dodge the issue but engineering, and by association, model engineering, is a very wide and complex discipline. To try to explain and define all the terms you might come across would fill several volumes. As a beginner I would suggest that as you come across various terms you use Google or Wikipedia as a first enquiry and if you still have problems, then post questions on the forums, and there are many on the internet.

 

As an example, you asked about colletts (sic) the actual spelling is with one ‘t’ i.e. collets. If you use Wikipedia here you will find an excellent explanation with diagrams and pictures, much better than I, or most others on this site, can provide.

 

Further, there are many, very readable , books on the subject available from book stores and libraries as well as magazines which make excellent and entertaining reading.

 

I’m afraid there is no easy substitute for research and reading on the subject. Having said that of course we will do all our best to help but as I said it is a very wide subject. So keep asking.

 

Best regards and good modelling,

 

Terry

[John CoatesParticipant @johncoates48577]

Remembered another one – register – which appears both as a noun (“take a register”) and a verb (“register the workpiece”) in articles and books

 

What’s that mean then? Haven’t been able to fathom it out yet !

 

[KWILParticipant @kwil]

Noticeably absent from all of the above, if you really must polish in the lathe with emery or any other abrasive, cover the slideways or you may end up polishing (wearing away) an item you would rather not change for the worse!

[Ian S CParticipant @iansc]

Don’t use the carborundum cloth dry, put some oil on it. nearly worn out stuff gives a good finish. I find that folding the cloth over a file is the best way when polishing flat areas, we used that method when we were taught filing during trade training in the Air Force back in the 60s.  Ian S C

Edited By Ian S C on 07/03/2011 09:21:39

[DustyParticipant @dusty]

Sorry KWIL

Some things you just take for granted and forget to mention them. But yes covering the bed is a must when polishing in the lathe. I use a J-cloth soaked in oil so the particles stick to it.

[Steve GarnettParticipant @stevegarnett62550]

Posted by John Coates on 07/03/2011 08:45:55:

Remembered another one – register – which appears both as a noun (“take a register”) and a verb (“register the workpiece”) in articles and books

 

What’s that mean then? Haven’t been able to fathom it out yet !

 

 

It means essentially the same thing in both instances – put into its correct place, or the place made for it. In ‘take a register’ it means generally to identify that people are present and correct, and in engineering ‘registering’ means the positioning of a component in its correct and intended place in the whole assembly. It is also used in conjunction with setting up components to be machined, but in this case it refers to the relationship of the component with the machine and its tooling, rather than its final intended position in the finished article. It has a lot in common with the verb ‘align’, as well. So the usage here would be that if something is correctly aligned, it could be said to be ‘in register’.

 

Does it make sense now? I hope so, but sometimes explaining these things in terms others understand isn’t so easy…

Edited By Steve Garnett on 07/03/2011 10:54:19

[John CoatesParticipant @johncoates48577]

Posted by Steve Garnett on 07/03/2011 10:44:03:

 

Does it make sense now? I hope so, but sometimes explaining these things in terms others understand isn’t so easy…

Thanks Steve that does make sense. I tend to find it crops up more in articles in MEW than the Workshop Practice series as I think MEW writers are very experienced and writing for the same knowledge level whereas the WP writers come at it from a more basic perspective aimed at the newbie, particularly in the Coursework books (lathe and milling by Harold Hall)

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