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Member postings for richardandtracy

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

Thread: Mail order ban on bladed products
11/07/2018 20:50:18

Thinking of weapons being everywhere...

I got very close to being refused entry to Alaska in 1987 going along the Alaska Highway. I had been interviewed by the twerp in the booth for 20 minutes while I was getting hotter and hotter in a one piece motorcycle suit. The twerp asked me if I had any dangerous weapons, to which I said 'No'. He immediately told me I had, as he could see my log splitting axe on the back of my bike. I returned with 'If that's a dangerous weapon, the I have lots more on the bike. Starting with the bike itself which I can run people over with, the hammer & spanners to beat them with, the petrol to burn them with, the water bottle to drown them with, the medicines to poison them with, the kitchen knives to carve them with, and most dangerous of all, I have a brain bigger than the size of a pea.'. The twerp stomped off to get his signature rescinded from the 5 day entry visa he'd already approved - but his boss didn't permit it to be rescinded.

Then once going to the continent, the security checks at Dover, I was asked to get out of the van and empty my pockets. They saw my penknife and asked if I had any other knives on the van. 'Yes.', said I, 'It's a motorhome, and it has kitchen knives, four of them.' They gave up.

Regards

Richard.

Thread: great youtub
08/07/2018 09:39:40

Wouldn't mind his mill.

The idea is entirely scalable, and is a good one.

Jason, the jaws are held on with two screws that look to be one size smaller than the main clamp. The vertical clamp load, neglecting friction, could then shear the two jaw screws. As the area of the jaw screws is about 20% greater than the clamp screw, it's theoretically possible to shear the screws when clamping down. In practice, because friction exists, this won't be likely. I agree a key would be useful, I wouldn't argue against it - based purely on all the un-necessary brochure machining already being put on the clamps, so adding a key would be a negligible increase in machining time. But the key is not strictly needed.

Regards

Richard.

Thread: Carbide PCB drills and router bit sources
07/07/2018 20:47:03

The 1.5mm router bits are useful for very tiny milling. Even did a pen decal logo into wax on my CNC router with a 0.3 mm cutter. Got all mine from various e-bay sellers at £5 to £7 for 10, so not pricy even if they take a month to arrive.

Regards

Richard.

Thread: painting Galvanised Steel
06/07/2018 22:27:38

On the farm we let galvanised metal weather bare for 6 months, then the oxidised surface held the paint quite well.

Regards

Richard.

Thread: a new skill
05/07/2018 20:58:27

Building in cob, or welding, or blacksmithing, or sand casting. Those are the skills I'd like most. I'd also like to do slightly less rustic brickwork and plastering. Finally, silver/gold smithing. Then glasswork, enamelling, stone cutting. Oh heck, just 'making anything really well' would do me.

Regards

Richard

Thread: cold saw
05/07/2018 20:51:41

Yeah, but not sure I'd like to live there.

Regards

Richard

Thread: Am I getting an irritable old git?
01/07/2018 21:28:18

To directly answer the question, yes, you are.

Not that I regard it as a problem, feeling the same way myself.

Regards,

Richard.

Thread: Is this true..?
30/06/2018 18:12:14

Just been reminded of a question one of our old draughtsmen asked in 1988.

'Do you want it made of Metal or Aluminium?'

Thought it may raise a chuckle.

Regards

Richard.

Thread: Teaching a 17 year old how to use a lathe
30/06/2018 17:22:27

The fastest way to teach safety with a machine tool is with a pork or lamb chop. Get the youngster to feed it into the spinning machinery and see what happens. Then ask the difference between the chop and fingers. They get the message loud and clear. Did something like it with my daughters and the 10" mitre saw I have in the workshop, but used frankfurters. Actually managed to put them off touching the tool for years.

Regards

Richard.

Thread: Is this true..?
30/06/2018 17:15:59

Andrew, that latter can happen. As a stress engineer I always work to the minimum specification strength (S in aerospace terms). In practice the material is rarely this weak. I've seen aluminium with an 'S' strength of 295 N/mm^2 have a test certificate strength of 420N/mm^2, which is around the Aerospace 'B' value band for the alloy where you are 90% confident that 95% of samples will exceed that strength.

Regards

Richard.

29/06/2018 21:11:59

Do you ever fly in an aeroplane? If so, why?

Regards

Richard.

Thread: Lidar Build Video
29/06/2018 20:20:40

Liked the cat comment at the end. They always have to have the last word...

That is a pretty impressive bit of kit. What are your plans for it?

Regards

Richard.

Thread: WM18 CNC Mill Conversion
29/06/2018 16:13:05

16mm dia x 5mm pitch x 700mm long ballscrew cost me £35 from China. Thread efficiency 85% compared to 35%, equivalent to more than doubling the motor torque while also almost eliminating backlash. Makes sense to do it.

It also makes sense to do it yourself - then you know the machine inside-out, which will help if there are problems later.

Regards

Richard.

Thread: Is this true..?
29/06/2018 16:06:12

As a full time stress engineer for a number of years, I will number among the sort-of camp. If the materials are similar, and the tapped hole is of a material not less than 60% the strength of the screw, it is true. Steel fasteners into alumium or brass are more difficult. Steel fasteners into wire thread inserts in aluminium or brass are more difficult still. A good rule of thumb for steel into 6082-T6 is 3D engagement makes the screw break first for grade 12.9 or weaker. Wire thread inserts make the 3D reduce to 2.5D.

Regards

Richard.

Thread: Rollers and benders
27/06/2018 20:36:11

For the bender, if you want it for thin metal, look up the David Gingery book on the Camden Miniature Steam Services book (my tablet won't paste links in this forum, sorry). I have a copy and can recommend the design as clear, concise and eminently practical. The only down side is that, as it's American, the sizes are imperial.

Regards

Richard.

Thread: Body filler on brass?
27/06/2018 15:42:04

It's on a tender & doesn't get hot? If so, and it's painted.. how about car body filler like P38?

Regards,

Richard.

Thread: Hot rail tracks
26/06/2018 22:04:52

Why does hot track not slow or delay the bullet trains in Japan? They have a very similar maritime climate.

Is it just because Network Rail is incompetent?

Regards

Richard.

Thread: TAP AND DIE SET
26/06/2018 22:00:04

I have Lyndon ones for my most used sizes - M6 & M10. They work well.

I have carbon steel ones for odd sizes the are not often used, like M10 x0.75., or 7BA (don't often make cap jewels for Parker51 fountain pens, so HSS is not justified).

For really wacky sizes, like M7.4 x 0.45, or M12 x 0.8 triple start, they are only available in high quality HSS.

I had a cheap 'carbon steel' set from the late 1980's, and 3 of the 8 sizes were plain wrong pitch. A set of LH taps bought last year very cheap from a Chinese e-bay seller turned out to be a high quality RH set, so I kept them and felt I had a bargain even though I didn't have the LH taps I was hoping for.

Regards

Richard.

Thread: homemade anvil.
26/06/2018 21:45:28

I have a 25 lb anvil I bought through Northern Tools about 14 years ago, a Chinese one. When I moved house & drilled attachment holes in it for my current bench 13 years ago, I found it was cast iron. This was the same time as I found my Chinese repro Victorian fireplace was cast steel. Both used exactly the wrong material. Hrrumph.

However, the anvil has not shattered in the use I've put it to, and would say any hefty lump of steel you can get to use as one will be worth the effort.

Regards

Richard.

Thread: proxxon KT70 CNC ?
24/06/2018 06:31:35

I have no experience of the Proxxon, but I am in the slow process of doing a 3 axis lathe conversion to do a similar job of engraving the outside of pens.

The Nema 17 motors use in the Proxxon conversion are tiny, with very little torque. I would strongly advise that you check the torque requirements of the machine you are to convert. The torque needed to apply an axial force with a leadscrew is roughly as follows (from 'Ondrives':

Torque (N.m ) = Axial force (N ) x Pitch (mm ) / (2000 x PI( ) x thread efficiency )

Where: thread efficiency = 0.35 for conventional threads and 0.85 for ball leadscrews and PI( ) = 3.1415

The axial loads you will need to consider are:

  1. Table friction, both 'stiction' and the smaller dynamic friction.
  2. Required acceleration of the table
  3. Cutting forces ( these will be tiny compared to the acceleration loads )

It is close on to impossible to guess the friction and stiction loads, so a spring balance pulling the table with the leadscrew removed is needed. You might just be able to calculate the torque by applying a load to a lever attached to the leadscrew drive handle and hanging a weight off.

OK that's one minor technical bit considered. The most important bit is being completely clear in your mind what you want to do. Is it just to create spirals? Or any type of engraving? How fast? How capable. It is an easy field to waste money in, as I have. I wanted to engrave and cut threads for pens, so bought a 4 axis gantry machine, and discovered the zeroing and repeatability of the gantry was such that the thread cutting was insufficiently concentric. For the engraving, it was adequate. But.. The multi start thread cutting on a conventional lathe is close to beyond me as I need up to 5 starts at really wierd pitches, which is one reason why I wanted the CNC. So, one answer is to convert a lathe, which is now what I am slowly doing.

Hope this sets you thinking

Regards

Richard.

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