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Member postings for Steve Withnell

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

Thread: Where have all the Mondeo's gone
08/04/2018 21:06:28
Posted by SillyOldDuffer on 08/04/2018 20:25:12:
Posted by KWIL on 08/04/2018 14:51:28:

False status.

My dad's job once involved sharing an office with a succession of interesting characters en-route to new challenges. One of these chaps answered an ad in the local paper for a second-hand car and was invited round to take a look.

When he got to the address, it turned out to be a minor stately home in large grounds near Bath, where he met the owner - one Arnold Weinstock. Remember him? His obituary describes him as Britain's premier post second world war industrialist. At the time he was making huge profits with GEC.

What car was the super-rich industrial magnate selling in the local rag? He drove a very ordinary Ford Cortina.

Dave

And he only had one house - how times change!

Thread: Help choosing a smartphone
01/03/2018 11:30:22
Posted by Otley on 27/02/2018 11:51:45:

I’m looking for advice on how to proceed from anyone of a similar outlook to myself. What physical size phone have others gone with? 16Gb or 32Gb or more – or less? SIM only or pay as you go? How much to spend? Etc. Any advice welcomed!

Thank you.

Just been through this myself. I've seperated the problem into two parts - the phone and the service contract. Three are charging me £12 a month for 12GB of data + unlimited text and calls. So stopped using the house phone for outbound calls. See how much you spend on outbound calls to get the overall cost difference. I 've had the phone for a couple months or so and no matter how hard I use the phone, I haven't managed to use 5GB in a month, so 12GB is equivalent to "unlimited" in my case!

Next problem is then the phone itself. Samsung are fantastic phones, my wife has had them for along time. However, the latest Samsung is £750!!! Not happening. We now have three different Motorola phones in the family and all are good. They are built by Lenovo who have a good reputation. Two of the three were bought as special offers from Carphone Warehouse, service is great and they are easy to deal with. The third was bought from an online outfit offering the phone Moto X4 as the sharpest price, but rapidly turned into a nightmare which took weeks to sort out.

Reading your post, sounds like the X4 (with its 3 cameras and all metal case) is too big and heavy - albeit fantastic value for money. Take a look at a Motorola G5Plus, still big but lighter and it will give you a starting point. It's the right sort of processor and memory capacity to provide at least say 3 years usage before obsolence kills it.

https://www.carphonewarehouse.com/motorola/moto-g5-plus.html#!colour=grey&capacity=32GB&dealType=sf

Whatever phone you go for, do check/challenge the processor as this will determine longevity and the satisfaction you get from using it. Just like driving an underpowered car is a constant source of frustration.


Not having had my own smartphone before, I've been amazed at the huge volume of free and useful applications in the playstore.

Steve

Thread: When is 9mm not 9mm?
04/01/2018 17:46:39

Another combination to watch for is 1/4" and 6mm in brass and copper round bars. The last two suppliers I've used off eBay don't differentiate between the two sizes...When I asked why they had shipped 1/4inch instead of 6mm, it was because they had 1/4inch in stock...

Thread: Private Messages
02/01/2018 18:36:29

Mystery solved! I thought my account had been hacked when all these PM's started turning up...

Happy New Year!

Steve

Thread: Myford ML10 headstock bearing play
01/01/2018 10:15:04

The runout on my first lathe was nearly 0.1" and would still make perfectly good parts! Really bad runout will still deliver round parts From a novice point of view (which I will always be at this game), knowing how your machines perform is more important than seeking perfection (which you will never achieve) in them.

Don't buy a collet chuck to make the runout go away - most turned parts are produced in either a 3 or 4 jaw chuck with only a few specialist jobs needing a collet chuck. I have all three - but 75% of jobs are done in the three jaw. 20% are maybe done in the 4-Jaw. A few are done on the face plate. Doesn't leave a lot of jobs that NEED a collet chuck.

I'm definitely with Jim and Hopper on this one.

A more important check might be to see if it is actually turning parallel, rather than taper and work on reducing any taper. This is easy to do - just stick 100mm of 25mm steel bar in the chuck and take a light skim over it's length and see it the start and end diameters are the same. If not - someone in the group who knows the ML10 better than me will advise next steps!

Happy New Year

Steve

Thread: Using a fly cutter
30/12/2017 13:20:33

My first lesson using a flycutter was that the typical ones sold on eBay don't have anywhere near enough rigidity or mass for anything only the lightest of work. I 'made' one one by bolting 25mm square bar (with a piece of 10mm silver steel as a cutter) to the 250mm face plate on my lathe and used that to face off some large chunks off ally. I don't think the finish would have been as good on the mill.

Regards

Steve

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Thread: What's the strangest project you've ever seen in an old ME or MEW?
20/12/2017 17:57:25
Posted by not done it yet on 19/12/2017 07:29:49:

more like an overgrown shotgun cartridge.

Not 'overgrown' at all. A normal gauge cartridge. Admittedly rather bigger than a .410, but they just used the size for the job. It was an 8 gauge. Some wildfowling shotguns used a 4 gauge cartridge. I suppose most out there only think of the most common shotgun size - the 12 bore.

You can work out the diameter using the standard density for lead and 4/3 Pi r^3. Without checking, a 12 gauge is about 0.718". More like a cannon shell case than a bullet, I suppose.

Edited By not done it yet on 19/12/2017 07:33:51

Pretty sure the old Field Marshall was a 12 bore sized cartridge...Dad had one for a short time, think it went for scrap!

Steve

Steve

Thread: Which lathe
22/11/2017 19:31:20

Get a C3 and start turning! My critieria for my lathe was it had to be the heaviest I could find that would fit on the bench and be new Chinese. Makes perfectly good stuff. Mind you, I don't get tool room jobs from NASA that often

Crazy decision making criteria, but no regrets at all and it's done a quite few jobs now over the ten years I've had it.

Steve

Thread: Metalworking files - Guidance required please
12/11/2017 10:29:47

I wouldn't buy a set to be honest. I do have a set and pretty much 95% of the time just use the flat No.2. I don't think I've ever used the rat tail. An exception is the CK branded needle files, I use most of them, though again, the round file doesn't get used much.

Steve

Thread: Lathe unwanted taper
12/11/2017 10:24:17
Posted by ChrisB on 09/11/2017 10:40:24:

Thanks for all the replies, I spent most of this morning in the workshop adjusting bench feet and doing some test cuts on the lathe, also knocked out a spirit level out of some scrap I had around and a test tube - surprisingly it turned out much more accurate than a normal level,

Bit of a tangent - when I was a kid 10 or 11, Grandad asked me if I had a testube I didn't want. I gave him one to make a level - he knocked a hole in the end of the tube and fastened it to a long length of hose pipe. By filling the pipe at one end until water appeared in the test tube he could establish a level over a long distance.

Steve

Thread: How long does it take you to make stuff?
12/11/2017 10:06:49

Years, but I get there in the end...

The very best work I've seen is about infinite patience and the worst was rushed. So long as you are enjoying the process, how long it takes doesn't really matter?

Steve

Thread: Spurious Accuracy
03/11/2017 18:30:13

Oh well, I'd better ditch my '10ths' clock then...

Thread: Which milling cutters first?
02/11/2017 21:51:29

One answer would be "Milling: A Complete Course", by Harold Hall. 10mm end mills would get you started quite nicely.

Steve

Thread: Milling - How to get a good finishing cut?
30/10/2017 20:16:25
Posted by Marcus Bowman on 29/10/2017 23:34:07:

If it was me, I would use a polished, uncoated single-flute carbide cutter with an aggressive geometry designed specifically for machining aluminium. If possible, I would avoid using long small diameter cutters,

Speeds and feeds are pretty important. Spindle speed shold be basded on around 100metres/minute, so a 3mm cutter should be turning at somewhere around 10,000rpm. I'm guessing you are not running your spindle at that speed. A 10mm cutter should spin at around 3000rpm, which is achievable on many small mills, so that's a good go-to size for starters. Won't work for tight corners, of course, but ,as JasonB says, you may be able to deal with those by drilling, or by machining separately.

Rough out, leaving 0.2mm to finish. Climb cut the finishing cut. High speed, but a slower linear feed may help.

I have had decent results with a long series 2 flute cutter on 50mm deep finishing cuts, but it was a 10mm cutter, not a 3mm matchstick. Roughing at 3000rpm, and up to 500mm/min, taking cuts of 15, 15 and 20mm down the face, finisihing with a single climb cut pass at full depth, 3000rpm and 120mm/min. Material was grade 6082 (HE30).

Marcus

Cheers Marcus. I've been asked to make another one of these, so I'll work out the machining as above. I've seen a few single flute cutters around from China, but may stick to a decent slot drill. My mill is flat out at 2,000, so will have to make do at that too!

29/10/2017 21:21:11

All done - next step is to see if it performs!. I ended up polishing the sides with the flat of a file, I still had some noticeable ripples in the walls. More practice is probably in order.

p1010078.jpg

p1010082.jpg

27/10/2017 18:56:31
Posted by not done it yet on 27/10/2017 16:49:29:

As i see it, if the depth is crucial, is the ally plate a good constant thickness or has it been faced off? No real problem if youogo slightly too deep - just face again? Another ploy, if the surface finish in the bottom of the cut is needed to be a polished surface, would be to fabricate with a through slot and affix a flat back plate?

My technique is to machine out the cavity a little too deep than skim the top to size, so the bottom of the cavity is parallel to the top of the walls. I could machine a through slot, but I'd still be left with the key issue of getting a nice finish to the side walls and I'd have 16 holes to drill and tap rather than 8 and two lids to make! So all trade offs as ever.

Steve

Edited By Steve Withnell on 27/10/2017 18:58:14

27/10/2017 18:52:35
Posted by Muzzer on 27/10/2017 18:27:03:

When I worked in microwaves, the duplexers, loads, waveguides etc were made of copper, brass etc that could be silver plated. It was also pretty handy for brazing the bits together. To my understanding, the purpose of the plating is to improve the contact resistance between components which presumably isn't ideal with aluminium. Similarly, when I used aluminium for high current busbars, it was necessary to use special conductive grease (copper bearing, IIRC) to get a good contact. Don't you need a good contact anywhere, or is the cavity free floating electrically?

For (my) reference, I see the skin depth of sliver at 3.4GHz(?) is about 1um and aluminium about 1.5um whereas the layer of aluminium oxide is only 10nm or so, apparently.

Murray

Hi Murray,

I'm using stainless screws through the case into copper rods. It's all about skin effect so the stainless screw is literally a mechnical fixing and irrelevant to performance. The bottom of the copper rods, I chamfer towards the tapped hole so that the edges bite into the aluminium. Instead of conductive grease, I'm using gold leaf as a gasket to ensure a good seal. This is the other reason for needing a nice flat finish to the walls of the case.

27/10/2017 16:01:44
Posted by Sam Stones on 26/10/2017 22:25:30:

Hi Steve,

Sounds like 'Plumber's radio' to me (wave guides and cavities?)wink 2.

Climb milling; slow feed; plenty of turps.

Regards,

Sam

Interdigital Digita Filters - I've made a few at 1.3GHz and this is the first I've attempted for 3.4GHz. I thought with less metal to remove it would be easier, but I've also a lot less 'elbow room' with this one. I shall break out some turps! (I've been working with Parafin and Neatcut, but the Neatcut ends up in sticky mess).

27/10/2017 15:56:32
Posted by Andrew Johnston on 26/10/2017 22:23:18:

A CNC mill, climb mill, and use a 3mm cutter so you don't get chatter in the corners. thumbs up

Failing that I'd leave about 10 thou or so on width and length and climb mill full depth. The depth can be set accurately using the knee, or quill, depending upon the mill type.

If 22mm is a quarter wavelength why is the 15mm depth the critical dimension?

Andrew

Thanks Andrew.

I keep avoiding sending Ketan a wedge for a KX1, which would be ideal for this application The 22mm is not critical because the resonators are tunable. The depth of the case affects the impedance and bandwidth of the filter (etc). The cleaner the finish the better the overall performance.

26/10/2017 22:12:46

I've milled a cavity in some Aluminium plate 22mm wide x 56mm long and 15mm deep. The corner radius is 2mm. I need to take a couple of finishing cuts, whats the best technique to get very best finish? Clue - 22mm is a quarter wavelength

I've obviously got a long series 4mm cutter, which is a standard helix carbide type and the only other cutter I have is a 5mm high helix version (which would obviously leave a bit of cleaning up for the corner radius. The depth of the cavity is the critical dimension.

Steve

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