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Member postings for Muzzer

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

Thread: More reliable connectors
06/02/2015 10:22:37

Bootlace ferrules make for a neat installation, prevent strands of wire getting where they shouldn't and stop the screws of some connectors from damaging the strands. They are a great idea if you have some, although sometimes the plastic barrel can get in the way if you are inserting more than one into a single connector. I see that CPC also stock them. And Maplin.

Another means of terminating stranded wires is the pin crimp or flat blade crimp if you prefer the red/blue/yellow system.

On the subject of stranded wires and compression terminals, don't ever be tempted to tidy up stranded wires by solder tinning them before inserting them into screw terminals. It all looks neat and tidy when you finish the job but unfortunately, solder is prone to "cold flow", whereby the solder flows due to the applied pressure over weeks or months. The result is a loose connection, no matter how hard you originally tightened it. This in turn can lead to intermittent connections and more importantly, the risk of fire if the wiring is passing high voltage and current.

As this is a well-recognised problem, it's now unusual to see tinned wires in new products. However, I have seen one or two in recent years. They should be cut off and reterminated.

Murray

Thread: Mist coolant
05/02/2015 16:55:07

The Mercans seem to use it quite a bit, as they seem more likely to have air lines in their (work) shops. Also known as Minimum Quantity Lubrication (MQL), AFIK. The clue's in the name - it delivers lubrication of the cutting edge but no significant cooling. The small air jet also clears the swarf, so the surface finish benefits on both accounts.

I tend to use flood coolant if anything and even then it's primarily for preventing the work piece and tool from overheating (ie to protect the tool) or for parting. For machining aluminium, I use WD40 and a brush which really isn't ideal, especially for milling - probably a situation where a mist / MQL system would be helpful.

I've been considering getting a mini compressor for this purpose but I'd want to convince myself it was fairly quiet - anyone got any recommendations for small, quiet compressors?

Murray

Examples here

Edited By Muzzer on 05/02/2015 17:02:56

Thread: Parting Off MEW225
05/02/2015 14:12:47

You're not worrying about it enough!

05/02/2015 13:08:43

We love taking simplistic views of problems. When we talk about the tool "springing", we are actually referring to the movement of the point of the tool relative to the point on the work piece where it acts. In between them is a whole series of slides, screws, bodies, joints etc - as well as the workpiece itself. The whole system is a combination of linear (sprung) and non-linear (backlash etc) elements, often with quite different characteristics in different directions.

There have been many PhDs written about judder alone and that involves just part of the same system (a lot of judder is down to the stiffness or spring constant of that whole system).

Try applying a small force, then a large force, between these points in each of the 6 main directions and measure the resulting movements. Then imagine trying to control the path of the tool in the workpiece under significant load. On some machines this will be fraught, particularly where poorly set up.

Murray

05/02/2015 11:01:51

I'm sure there are several factors at play and some setups will involve some but not so much others. I don't think it's helpful to champion one factor as the common mechanism. In the absence of any methodical, evidence-based tests nobody's going to be able to do much more than trade opinions.

Overcoming backlash or compliance by introducing springiness may have been found to be moderately successful in some cases but ideally we'd be identifying the troublesome behaviour objectively and actively - and then figuring out how to tackle it.

In may case, I started by assuming it must be possible to achieve consistent and safe parting on my machine and went about it methodically, making it achievable by minimising spring, overhang, backlash, judder etc (by using the DTI we spend so much time talking about).

Getting the speeds and feeds correct to avoid judder is another factor (helped by lubrication) that has to be tackled - any machine will judder with the right combination of speed and load, yet this is something you don't want happening when you are in the middle of a critical operation like this. If you trigger judder on a poorly set up parting tool, you are most likely asking for trouble. It's a thin line between judder and this "dig in" we speak of.

Murray

Thread: A Word of Warning
05/02/2015 10:07:35

I've had 2 of these Xmas cracker workmate things for years, bought from different high street DIY shops. One has the MDF top and the other is made of "engineered"(?) bamboo. The MDF is battered and fibrous, the bamboo is scratched but otherwise almost as new. They both cost the same handful of peanuts (a tenner?). Look out for the bamboo ones - it's an excellent material, being tough, springy and non-porous and I seriously doubt you would be able to snap it in the same way as MDF.

Murray

Thread: A better lathe ....
04/02/2015 10:31:56

Although I'm more of a tool / machine maker than a model maker, I wouldn't dream of attempting to design a lathe myself when there are so many excellent industrial products out there already, available for less than it would cost to make one. Like most MEs, I have only a very superficial understanding of any of the design considerations and decades (centuries almost) of experience.

Even then, I would struggle to design something that I couldn't realistically expect to see made either - and I'm not vain enough to believe anybody would do so. Most machine tools rely on heavy cast iron to provide the basic rigidity and core framework - this isn't something any of us could sensibly attempt, even if we understood how to design it. I suspect you'd have a very short list of entries....

Call me a coward but I'm happy to have a bun fight and vote for a favourite lathe, though!

Murray

Thread: What did you do today (2015)
04/02/2015 10:05:44

Paul - nice work. Are the walls of the firebox usually as heavy as this - is it to scale? Looks like steel plate rather than sheet, so shouldn't be a problem getting nice welds or passing the pressure test surely!

Don't drop it on your toes!

Murray

04/02/2015 10:00:47

Interesting video showing use of Solidworks > Sprutcam > Tormach CNC mill to make a small bracket.

Good example of why CNC isn't just for "mass production", whatever that means in our context. Could be done manually but would involve a lot more setting up and handle twiddling. He could have been a fair bit more aggressive with speeds and feeds but as he says, he likes to play safe.

Murray

03/02/2015 22:45:48

Les, Linux has supported multi core processors for many years (almost 20), so there's no need for any significant change. Assuming that the Broadcom device functions are already supported / implemented already, I doubt there's anything extra required to make the most of the new model.

The main impediment to implementing a full-blown CNC controller will be the requirement for additional, fast I/O. I'm sure / hope it won't be long before someone makes it available...

Murray

03/02/2015 21:24:59

I have bought quite a few things from this place although there are several other stockists in the UK as well as Farnell/CPC and RS. They stock cases, breakout boards, accessories etc as well as the RPis themselves.

Although they appear to have stock of the 2 currently, they are saying that orders are delayed 1-2 days due to "extreme demand". I notice that the RPi website went down today too, presumably due to overload. Seems to be back up again now.

Murray

Thread: A better lathe ....
03/02/2015 17:22:16

I'm not convinced I'd be looking at the likes of the Metalmaster or any of these all-in-ones. Apart from not wishing to spend half my life endlessly reconfiguring the thing between operations, there are many compromises that make them jack of all trades and master of none, starting with rigidity.

If we I posed the "Desert Island Disks" question ie "you are only allowed one machine tool, so what will it be", then perhaps I might be persuaded. Until then, I'd have a lathe for turning, a mill for milling etc etc. And if cost were truly ruled out as a factor, I'd be ringing an industrial architect to plan the new factory!

For "old metal", perhaps it would be a Hardinge, although I've never given the question any serious thought. There are some absolutely superlative modern machine tools around nowadays that cost the same as a small house - CNC controlled, mostly.

Murray

03/02/2015 11:05:32

Never had to get rid of a car due to the electronics needing repair. Mostly it's due to prangs, emissions and MOT failures these days. What make are you talking about?

Thread: digital calipers
02/02/2015 23:37:01

How can you use a rotary encoder to measure a linear distance with "absolute accuracy"? At some level you need to convert the linear distance into a rotary movement. We might call that a rack and pinion. Then you are back to where you started ie the rack has a temperature coefficient. Am I missing something?

Without resorting to exotic optical / laser methods, there are ways to reduce the temperature dependency. Low temp co materials and subsequent compensation to account for the temperature of the instrument for instance.

I think most of us would have the sense to realise that if we are measuring a part when it is hot, it will be smaller when it isn't. If the critical characteristic is defined at that lower temperature, we need to account for the dimensional change due to the temperature shift. I suppose you could say that IS rocket science.

Not all calipers have acceptable accuracy with temperature and that's one characteristic that clearly differentiates different brands. However, there are clearly some very cheap calipers that are actually pretty good and present a compelling performance vs cost outcome. I'd rather identify and obtain one of those than blindly cough up loads of dosh for a Mutitoyo each time I need a new measurement tool. That would be a more valuable outcome for all of us here, rather than trading opinions.

Murray

Thread: What did you do today (2015)
02/02/2015 18:23:40

New version of the Raspberry Pi is unveiled. Nice piece of kit for £23. Cortex A7 (ARM) quad core processor 900MHz /1GB RAM.

Joy of joys. As it will be almost as powerful as a proper PC (six times as powerful as the last version), "the Raspberry Pi 2-compatible version of Windows 10 will be available free of charge to makers". Should also be pretty good for machine control, assuming you run Linux of course....

Murray

Thread: Holding a ring on a lathe.
02/02/2015 18:11:53

The OP says "both sides need to be faced and chamfered internally and externally." That presumably requires both internal and external work holding.

I imagined soft jaws to do the facing, boring and internal chamfering, followed by an expanding arbor to complete the external chamfering (and turn the outside surface, presumably).

Thread: What did you do today (2015)
01/02/2015 19:40:49

Indeed. And if you think that's too virtual, the chain / belt function in 3D CAD is very useful for designing "real" belt sizes into your machine before you even have pulleys and bits of string in front of you. I did this in Solidworks and found the timing belt fitted perfectly when it arrived - handy really, given that I'd made the rest of the parts by then. Avoided having to provide Norma's great adjustment slots everywhere, which seemed like a bodge to me.

Murray

01/02/2015 15:21:46

If you get stuck, you should be able to estimate the required length using a belt length calculator. Something like this. You need to know the section (size) of course but that isn't difficult to figure out.

I bought some timing belts, taperlock pulleys and vee belts from these boys in Hampshire and they seemed pretty reasonable.

Murray

30/01/2015 20:04:44

I think you said you are using Sprutcam. That seems to cost about £950+vat according to my enquiry recently. How do you find it? Would be interesting to hear how you find it. I see there is a 30-day trial so you can try before you buy.

I have HSMXpress which is free for 2.5D milling but unfortunately only works with either Solidworks or Autodesk Inventor. I'm only starting out with it at the moment...

Thread: Mirror, Mirror on the box
30/01/2015 19:59:43

In one of his recent TV programs, Guy Martin said that as a commercial vehicle mechanic, he is expected to provide and maintain all his own tools. Sounds as if that is the norm in that line of work. Don't expect many apprentices these days could afford to do this.

Murray

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