By continuing to use this site, you agree to our use of cookies. Find out more

Member postings for Andrew Johnston

Here is a list of all the postings Andrew Johnston has made in our forums. Click on a thread name to jump to the thread.

<< First < Prev 342 343 344 345 346 347 348 349 350 351 352 Next > Last >>
Thread: Metric vs Imperial - Practical or Traditional?
24/10/2010 23:12:22
Wot? Lager! What's wrong with a good bitter. None of this foreign stuff thank you!
 
Andrew
Thread: Stuart S50
24/10/2010 23:07:56
Actually cast iron works pretty well against itself, unlike most metals which do not like working against themselves.
 
Regards,
 
Andrew
24/10/2010 22:33:44
Hi Chris,
 
'Silver steel' is a high carbon steel that can be hardened and tempered by simple heat treatment processes. I assume it is called silver steel because the finish is normally ground to tight tolerances and has a silvery appearance. It has no connection with stainless steels.
 
Regards,
 
Andrew
Thread: Making lathe tools
24/10/2010 22:27:26
Hi Chris,
 
Welcome to the forum.
 
I'm not familiar with the Axminster Micro but I assume it's a small (micro!) lathe. Your fellow club member is correct in that a round nose tool will often give a better finish. However, what he might not have mentioned is that a round nose to the tool increases the radial cutting forces on the tool and also increases the power required. Unless you have a large, rigid lathe this may well cause exactly the problems you have been seeing. Try a tool with a nice sharp point at the end; It should cut with less chatter and less power required. By all means put a small radius on the tool end, say 0.1 or 0.2mm. This will give a slightly better finish, but not give the problems caused by a larger radius.
 
Regards,
 
Andrew
Thread: MEW-169 Tool-post Grinder Article
23/10/2010 11:55:04
Of course I'm talking nonsense here; the wheel and work rotate in the same direction so that the relative motion at the wheel/work interface is opposed.
 
Clearly I'm not firing on all cylinders (sorry about the pun) this morning. I need more coffee!
 
Regards,
 
Andrew
23/10/2010 11:41:16
Can't say I've ever used a grinder on my current lathe, as I don't want to impair the accuracy with grinding paste. However, I do have a cylindrical grinder in the workshop and the work always rotates in the opposite sense to the grinding wheel. The work obviously has to rotate to achieve roundness, but I'm not sure why it should be in the opposite direction.
 
I can think of two reasons. One, grinding is a pretty crude process at the particle level, lots of negative rake. So the relative surface speed has to be high to heat and soften the chip, which aids the shearing process. Given that, it wouldn't make sense to negate the relative surface speeds obtained by rotating the work and wheel in the same direction. The other reason may be that rotating work and wheel in the same direction is equivalent to 'climb' milling, and the grinding wheel particles may not like the sudden increase in load?
 
Regards,
 
Andrew
Thread: Drill Sharpening Jigs - Advice please.
22/10/2010 22:56:40
Hmmmm, the Tormek looks interesting, but it's not cheap. Does anybody have experience of using one of these devices?
 
Regards,
 
Andrew
Thread: Making Progress
22/10/2010 09:30:30
Hi Sam,
 
Looks great. Posterity will be pleased.
 
I would like to build a simple clock, but I've already got too many unfinished projects! And I'm not sure I have the patience to do all that polishing.
 
Regards,
 
Andrew
Thread: Panasonic dv-700 inverter
20/10/2010 11:25:51
Steve: thanks for elucidating what I should have said in the first place.
 
Regards,
 
Andrew
Thread: Simpler the Better -what do you use?
20/10/2010 10:54:58
Wow, neat video; sad, but I enjoyed watching it!
 
Regards,
 
Andrew
Thread: Panasonic dv-700 inverter
20/10/2010 10:35:59
Is the radio mains powered or battery operated? If battery operated, then the interference will be airborne. If, for the time being, we assume that the inverter has a PFC in the front end, then the motor leads are the most likely to be radiating.
 
In short, try screening the motor leads as a start. Be careful to avoid current loops in the screen.
 
Regards,
 
Andrew
Thread: Continuing Articles
19/10/2010 08:59:12
In the distant past I used EasyCAD; excellent 2D program and very fast. Even better, it pissed off the 'draughtsman' at the company were I was working at the time, as I was faster and more accurate than him. Several computers later I switched to QuickCAD. This was an ok package, but essentially just an electronic drawing board.
 
I now use the 'Expert' version of Alibre; not cheap, but a lot cheaper than Solidworks. Alibre has its limitations, but it has allowed me to design parts and assemblies that would not have been possible in the timescales otherwise. Rather oddly I got on with the 3D capabilities of Alibre with no problems at all. It's odd because professionally I have used ProEngineer and hated it.
 
Elliptical spokes should be fairly simple. Draw a plane at the bottom of the spoke and another plane at the top. On each plane draw an ellipse of the appropriate size. Do a loft between the two sketches and hey presto an elliptical spoke.
 
Regards,
 
Andrew
Thread: End mills in lathe chuck
18/10/2010 21:54:33
Unlikely, if it is done up properly. ER collets need to be done up 'pretty damn tight', to at least two grunts worth.
 
For ER25 collets above about 8mm, a quick search on the internet shows tightening torques between 70 and 90 foot-pounds. Unless you're the proverbial gorilla you're not likely to achieve that with normal spanners!
 
Regards,
 
Andrew
Thread: Scale model Economy hit & miss engine builders wanted
18/10/2010 21:44:57
I'm planning to mount my engine on a piece of jig plate, along with a separate fuel tank and ignition system. There should be room on the plate to mount something for the engine to drive, if I felt so inclined.
 
Regards,
 
Andrew
Thread: Continuing Articles
18/10/2010 20:24:29
Wow, all the old favourites being mentioned! I'd completely forgotten I had a copy of GEB; must get it out later and have a look.
 
Regards,
 
Andrew

Thread: End mills in lathe chuck
18/10/2010 18:43:28
Hi Derrick,
 
TIR = total indicated runout
 
In simple terms, how wobbly the tool is compared to the spindle axis with which it should be concentric.
 
Regards,
 
Andrew
18/10/2010 16:56:12
It has been done, but personally I wouldn't do so, for the following reasons:
 
1) The TIR of a 3 jaw chuck probably isn't that good, and if it is, you shouldn't be using it for milling!
 
2) The milling cutter will be much harder than the chuck jaws, so the grip will not be particularly good
 
3) The jaws will only grip over a small area, compared to a proper milling chuck - see above
 
4) A largish chuck holding a small endmill increases your chances of getting a bonk on the nose or hand when getting close to see what is going on
 
No doubt there are many other reasons too. Use an ER style collet chuck, preferably mounted directly on the lathe spindle nose.
 
Regards,
 
Andrew
 
Edit: Of course there's no reason not to use an end mill in a lathe, just not in a 3 jaw chuck

Edited By Andrew Johnston on 18/10/2010 16:57:34

Thread: Continuing Articles
18/10/2010 15:52:30
Sadly these days, even in Cambridge, you will find the coffee shop, and hence the coffee table, in a bookshop, but sweet FA in terms of books. At least technical books anyway.
 
Regards,
 
Andrew
Thread: Hints and tips
18/10/2010 11:27:10
Hi Martin, welcome to the forum. Could be worse; I'm sure some people would add the result up 17 times! Of course entering it as it is written doesn't work if your calculator uses reverse Polish notation.
 
An OT story: At one company where I worked we convinced one of the secretaries that reverse Polish was an advanced 'position' that didn't even appear in the Karma Sutra......
 
Sorry about lowering the tone and all that......
 
Regards,
 
Andrew

Thread: Continuing Articles
18/10/2010 10:33:48
Hi Nick,
 
Not the item I was thinking of, but nevertheless an excellent example of an item drawing that cannot be made. I suppose from a philosophical point of view, in going from 3D to 2D some information must be lost, and that lost information leads to ambiguity in the 2D representation.
 
I am familiar with the work of Escher. I bought a book of his drawings many years ago, when I was doing my Ph.D. During that period I tried to read and/or buy at least one non-technical book every fortnight or so. Escher's drawings exhibit superb draughtsmanship. As Jim has mentioned some illustrate impossible scenes, but he also played with repeating 3D structures and the morphing of a shape from one form to another across the drawing.
 
Regards,
 
Andrew
<< First < Prev 342 343 344 345 346 347 348 349 350 351 352 Next > Last >>
Magazine Locator

Want the latest issue of Model Engineer or Model Engineers' Workshop? Use our magazine locator links to find your nearest stockist!

Find Model Engineer & Model Engineers' Workshop

Sign up to our Newsletter

Sign up to our newsletter and get a free digital issue.

You can unsubscribe at anytime. View our privacy policy at www.mortons.co.uk/privacy

Latest Forum Posts
Support Our Partners
cowells
Sarik
MERIDIENNE EXHIBITIONS LTD
Shopping Partners
Subscription Offer

Latest "For Sale" Ads
Latest "Wanted" Ads
Get In Touch!

Do you want to contact the Model Engineer and Model Engineers' Workshop team?

You can contact us by phone, mail or email about the magazines including becoming a contributor, submitting reader's letters or making queries about articles. You can also get in touch about this website, advertising or other general issues.

Click THIS LINK for full contact details.

For subscription issues please see THIS LINK.

Digital Back Issues

Social Media online

'Like' us on Facebook
Follow us on Facebook

Follow us on Twitter
 Twitter Logo

Pin us on Pinterest

 

Donate

donate