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Member postings for David Jupp

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

Thread: Lathe Accuracy Problems
10/04/2013 07:39:46

Have you checked for play in the spindle bearings (when at normal operating temperature)?

Thread: UCP Bearings for lathe spindle?
06/04/2013 19:12:00

Unless otherwise stated I'd expect such bearings to support transvers loads, but not be much good with axial loading - so for a lathe they would support the spindle, but may not cope with much end thrust.

Also not sure how you would get a precise alignment with the lathe bed, the self aligning nature is to cope with imprecise mounting - not what you want on a lathe.

Thread: Designs published in ME
05/04/2013 15:20:16

The use of 3D CAD can make some errors much more obvious early on, because the virtual model is assembled from actual sized parts. Checking for interferences becomes a simple exercise (as long as the Designer remembers to do it!), and gaps should be fairly obvious. Since 2D views and dimensions are generated automatically from the 3D model, the scope for simple typographical errors in final drawings is much reduced.

Even with 3D CAD it is still possible to make errors of design or of final presentation which might leave the builder head scratching. It is quite easy to leave a dimension off the drawing!

I should declare that my view on this is likely to be biased, as I earn some of my income from supporting a 3D CAD product.

Thread: Boxford shaper & VFD
04/04/2013 17:01:39

You'll still need the gearing down from the countershaft and pulleys - a more direct drive from a slowed down motor would not be able to provide anything like as much force behind the tool.

Thread: Motor for Chester Champion Mill
28/03/2013 08:23:08

Re internal fan and direction of rotation. Many internal fans in motors are simple centrifugal fans with straight blades - these work equally well in either direction, and force the air in the same direction regardless of rotation direction.

If the motor  has an axial style cooling fan, then the measures suggested above may be worth considering.

Edited By David Jupp on 28/03/2013 08:26:01

Thread: Speedy Boiler
22/03/2013 07:57:11
Posted by craig fowler on 21/03/2013 19:42:40:

I cant see any problems with my design though.

Typically it is all to easy to overlook something in your own work (not that I'm suggesting you have) - that is the main reason for independent verification of designs.

21/03/2013 19:05:28

May be worth noting that in industrial pressure equipment practice, the Design Verification Engineer and the Inspector are likely to different individuals with quite different qualifications/experience.

A Design Verification Engineer can check that the Designer has used a sensible approach or complied with a recognised code. The Inspector will check that the finished item matches the (verified) design. I would not necessarily expect either to be competent to do the job of the other.

Thread: Centec
23/02/2013 19:51:16

Be aware that invertor drives are prone to tripping standard RCD devices - in industry 'delayed action' RCDs are used to avoid this. Your problem might not be realted to incompatibility between motor and invertor.

Edited By David Jupp on 23/02/2013 19:51:46

Thread: Drawing mechanisms
23/02/2013 16:29:56

Any 3D CAD package that supports assemblies will easily handle linkages and interferences - gears are much less commonly supported, but may be able to be 'fiddled', depending upon exactly what you want to check for.

If just checking a basic concept, rather than taking the design through to real parts, there have been packages that allow you to do this with 2D sketches - though I'm struggling to find anything on the web at present.

Thread: Adverts obliterate text
14/02/2013 15:44:43

I was seeing that almost every visit when using IE8, having switched to Chrome I think I've only sen it happen once (and not so severely).

Theere seems to be something a bit odd with the site.

Thread: Which software?
05/02/2013 12:19:24

First I'll declare a bias - I have a connection with Mintronics (the major UK reseller of Alibre).

As Andrew mentioned, using 3D CAD is very different from 2D, and it can take a while to get used to it. Whatever system you look at, do work through any tutorials provided - I mean actually work through, not just watch. I also suggest you check out the on-line user forum for any system you consider - you'll get lots of free help from a good forum.

I believe there is good information on Mintronics and Alibre web sites about capabilities for each version of Alibre - but feel free to call if you have questions.

I suspect you will find free 3D CAD systems will fall into the 'disappointing limitations' box, but you don't have to spend a fortune to get pretty good functionality.

Thread: Bearings
28/01/2013 08:48:43

Bearing manufacturers web sites typically give information on fitting bearings - including housing / shaft dimensions.

In some cases you may want slightly different dimensions for each bearing (axial movement allowed at one bearing to allow for shaft thermal expansion).

If you accidentally cut too much material away, there are 'bearing fit' adhesives available that can save the day (widely used in industry beacuse quicker/cheaper than close tolerance machining).

Thread: Reproducing a thread for a tool
24/01/2013 12:30:03

If information like country of origin, industry, rough manufacture date is available - it may well be possible to make some intelligent assumptions on likely thread series, then with pitch gauges and calipers identify the specific thread. Of course if the thread is a 'special' or a particularly unusual one then the methods mentioned by others above will come into their own.

Thread: Milling Machines
20/01/2013 19:25:16
Posted by Donald Wittmann on 20/01/2013 18:41:48:

David, Thanks for clearing that up. I think that 1 that would have to be adhered to [in Europe] would be the CE standard. I would think they would all meet that, It's just that I was curious about the mechanical standards.



CE is not a standard - the CE mark is supposed to indicate that the equipment complies with all relevant EU Directives (low volatage, machinery, EMC,...). These typically relate to basic EU wide 'safety' requirements and are rarely anything to do with performance or capability of the equipment.

Edited By David Jupp on 20/01/2013 19:26:04

20/01/2013 16:59:37


Few standards (for anything) are compulsory in any legal sense - though of course if the manufacturer claims the product complies with a particular standard then it should do so. Being for hobby use doesn't make any difference.

Thread: pillar drill column
16/01/2013 19:27:07

There will be a HUGE difference in stiffness between scaffold tube and 2 3/4" steel tube (especially if you get ally scaffold tube). They didn't use a column of that diameter originally just for fun.

Thread: Hardening Stainless Steel
16/01/2013 19:21:25

Was not suggesting work hardening as a method to use (it explains why so many drills get broken in stainless) - just pointing out that 300 series steels will not harden by quenching.

If you want to harden stainless, it has to be from the correct family - if it is strongly magnetic you have a good chance it is. If weakly magnetic it's probably only workhardened austenic steel so will not quench harden.

16/01/2013 18:44:42

I can't see some of the posts becuase they are obsucred by the advertising (this seems to happen irregularly on this site) so apologies if this is off beam...

There are different types of stainless (ferritic, austenic & martensitic)

300 series are probably most common - these are austenitic, they work harden like crazy - but do not quench & temper

martensitic, can be quenched and tempered - think surgical blades

ferritic - I don't have much information to hand at present !

So some stainless grades can be quench hardened, but many can only be work hardened. You can sometimes (but not totally reliably) identify austentic steels as being non-magnetic (work hardening can tip them into being magnetic...).

Thread: Cool down a mini-mill motor.
14/01/2013 13:14:30
Posted by Michael Gilligan on 13/01/2013 15:04:45:


As a convenient point of reference [remembered from using laboratory glassware]

If you can just hold the palm of your hand on the motor, without pulling away ... it's probably around 70°C.


I'd suggest that the surface temperature probably isn't as high as that if you can hold your hand in place. Maybe with glassware you 'get away with it' because glass is not a fantastic conductor of heat, with metal object I certainly would not want to put my hand on anything very much above 50 C.

Thread: Which Stainless Steel?
02/01/2013 15:39:48

All 300 series (1.4404 equivalent to 316L ) will work harden. 400 series have different microstructure, less prone to work hardening, but not as widely available (and could be hardened by heat treatment anyway)

Use tapping drills on the larger side, and use a tapping compound.

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