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Member postings for mgnbuk

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

Thread: Face Knurling...
13/04/2021 09:44:22

Two reasons were identified.

Rather more than those two reasons in that case, Dave.

The steel used was that used for building ships at the time - what changed with Liberty ships was that the original (British) design was for "traditional" rivited construction & the Americans redesigned them to be all welded to allow construction of subassemblies and speed construction. With the riveted construction, if a plate cracked the run of the crack was limited to the plate concerned. With the welded construction the cracks ran through welds and ajoining plates. Add in to that poor quality welding perfomed by poorly trained, unskilled, welders (it seems that many if not most cracks started in poor welds or weld preps - that would appear to be the case in the example you quoted), the lack of knowledge at the time of the effect of welding the type of steel used & design shortcomings that put welded joints in stress raising positions due to the prefabricated construction were as much to blame as the material used. One "workaround" used to alleviate the problem was to rivet (not weld) a substantial steel plate belt around the ships below deck height.

I find the whole mobilisation & mass production of war materiel in the US during the war fascinating & I doubt that such feats could be accomplished today. The whole shipbuilding program was an amazing feat - largely starting from scratch, rethinking building techniques & many hard lessons were learned that laid the foundations for what we largely take for granted today. Interestingly, the only remaining part of one of the larger Liberty ship builders, Kaiser, is the company healthcare scheme set up at the time.

Nigel B.

Thread: Oddball inverter
12/04/2021 09:10:32

I don't think you get to set parameters like current with these devices

I have yet to come across an inverter that does not require the input of the basic motor parameters (voltage, FL current, frequency & base speed ) - these seem to be the basic minima to get up and running ? FL current would be particularly important in your case of operating a drive with a motor a long way below the drive capability.

No experience of a Cowells, but are they not plain bearing spindles so maybe higher drag than rolling element bearings ?

Nigel B.

Thread: Face Knurling...
12/04/2021 09:02:43

Stainless steel spokes are original equipment on my RE Interceptor 650 and my wife's Moto Guzzi V7 Special & I rebuilt one of my MZs wheels many years ago with a set of stainless spokes from Central Wheel Components (at one time the supplier of Triumph's spoked wheels). MZ OE spokes were chromed steel.

I recall many years ago there being an on-going spat in the letters pages of the original Motorcycle Sport magazine between two suppliers of stainless aftermarket wheel spindles getting increasingly vitriolic WRT the "correct" grade of SS to use in such an application. Always stuck with OE parts for tcritical parts, but note that at least some wheel and swing arm spindles (BMW & MZ come to mind ) appear to be hard chromed.

Nigel B.

Thread: Replacing a Canon printer with a Brother Laser?
05/04/2021 13:26:10

I bought a Brother mono laser printer (not 3-in-1) when it was on a Bank Holiday offer from PC World (less than £60 with a newspaper coupon IIRC ).

It was fast to start up, fast to print & decent quality. The "starter" toner cartridge didn't last long & a replacement was almost as much as the printer. This didn't get used up, as another part that the toner cartridge mounted on died, giving longitudinal lines down the page & this part cost more than the printer did, so it went for recyling and was not replaced. I don't think I had much over 2 years use out of it, so not really a bargain.

So back to an inexpensive Canon 3-in-1 inkjet for me - Canon because the print head is built in to the cartridge & they don't seem to be plagued by the terminal print head blockages that afflict Epson printers. Yes genuine cartridges are pricier as you buy the print head every time, but I use less than a pair a year & it always prints fine regardless of how long it is left between prints.

Work tried moving from a Brother 3-in-1 A3 inket to a Brother colour laser printer as business increased & the initial inket unit died - again great while it lasted, but then the main pcb failed just after it had had a full set of cartridges fitted (over £100 + Vat there) &as it was out of warranty it was scrapped. We run 2 of the Brother A3 inkjets now, using pattern cartridges, they last over 5 years in a busy office environment before dying and are a lot cheaper to buy than the laser. Duplex printing machines, with auto document feed on the scanner & two paper trays that we keep set as one on A3 and the other on A4. Better photo reproduction from the inkjets than from the colour laser, if that matters to you.

Nigel B.

Thread: Boxford Model C leadscrew half-nuts
03/04/2021 14:11:32

NDIY - that's a really interesting suggestion.

Interesting, but probably not practical. Unlike a Myford, which moves the half nuts vertically to engage & disengage the screw, a Boxford/ Southbend arrangement pivots the two halves :

boxford a apron.jpg

So the "shim" to allow re-tapping would not be parallel & the engagement mechanism may not have sufficient travel to engage the screw after the modification.

Nigel B.

03/04/2021 12:52:29

What material are the half nuts ?

Cast iron IIRC

Nigel B.

03/04/2021 12:00:20

The original part was made from a single casting that was split after being drilled & tapped for the leadscrew - would it not be easier to make a complete replacement along similar lines than try to add a threaded insert ?

Nigel B

Thread: CNC - What's the Problem?
02/04/2021 18:36:15

Commercial CNC setups have some very sophisticated tool changing capabilities, difficult to replicate at any reasonable cost. what proportion of hobby lathes have a capstan turret? How may of them could be automated?

Toolchangers are not compulsory on CNC machines - 3 of the lathes at work have manual toolposts ( 2 x Multifix & one Capto). When a toolchange is required, the program halts & a lamp flashes to alert the operator. Pressing a "tool change complete" button restarts the program. Obviously requires the operator to fit the correct tool ( a comment in the program can be added as a prompt) , but that hasn't been a problem so far. 4 of the CNC milling machines don't have ATCs either - lack of an ATC really isn't the end of the world !

They are not CE marked

As we are no longer a member the EU, CE marking is no longer required - but UKCA marking is. Whether or not there is any practical difference yet (other than the required marking being attached) is another matter !

Nigel B.

01/04/2021 14:21:36

How I would love to go back to using SolidWorks if only there was a cheaper 'lite' version

How cheap is cheap ?

Solidworks Education Premium is a membership benefit at the Experimental Aircraft Association - membership is from $40 year. Personal, not-for-profit, use only though, if that is a consideration.

Nigel B.

01/04/2021 10:11:14

Nigel, how do your operators know what the part looks like

Paper drawings as part of the works order. These may have been sent to us as a CAD prepared drawing or as a hand drawn sketch. Quite often the CAD prepared drawings are the most difficult to follow, have basic dimensions missing or are dimensioned in bizzare ways. Some simple parts are just a written description i.e a cylinder x O/D by y long or a plate x by y by z thick.

Most of our milling machines have Heidenhain conversational controls, which don't use G code (they have the option to do so if required). The lathes are 50:50 conversational Heidenhain and conventional Fanuc & my current work project is to retrofit a conversational Fagor control to a Gildemeister lathe (cheaper than a Heidenhain - this particular lathe doesn't warrant the extra cost). The conversational turning controls use cycles similar to Mach 3 "Wizards" to build up a program, though they can also run conventional G code. & can convert a cycle generated program into G code.

For Nigel K - I understand that FreeCad also has a CAM "workbench" to prepare toolpaths from the part you have designed. I have not explored this feature yet - it could be a useful tool for when I get my Triac back together, as I intend to use it initially with a GRBL controller which does not support tool radius compensation.

Nigel B.

01/04/2021 08:34:18

Hobby CNC machines are very cheap compared to industrial equipment, but I would suggest that most hobby users will require far more support than an industrial user who would have more of an idea how to use what they have purchased . Support costs money - the hobby user has spent (for a hobby) a relatively large amount of money and expects support, but the margins on the hobby machine are most likely insufficient to provide the level of support that (generalising here !) an untrained and inexperienced hobby user may expect. Add in a whole additional layer of equipment for the supplier to have to learn how to support & stock (relatively expensive) spare parts for, there doesn't seem to be much of a business case to support offering this type of machine into the hobby market IMO. As a derivation of the old joke woudl have it : How do you make a small fortune selling hobby CNC machine tools ? Start wih a large one ....

There seems to be a misconception that a deep knowledge of CAD is a pre-requiste to operate a CNC machine. While it does depend upon what you wish to achieve, a great deal of industrial use is simply programmed at the machine "long hand". At my current employment in a machine shop that specialises in producing graphite components, we have 7 CNC milling machines / machining centres & 6 CNC lathes - and no CAD / CAM facilities. The operators program everything at the machines. It should be said that we don't do 3D machining on the mills & some of the setups can get challenging, but for the most part CAD or CAM would not help with those anyway. With industrial CNCs we do have full tool offset capabilities that may be be missing from the hobby controls & may complicate some operations if not available.

Nigel B.

Edited By mgnbuk on 01/04/2021 08:35:13

Thread: Gluing Aluminium
30/03/2021 16:33:09

I use polyurathane adhesive sealant to attach aluminium plates to cover holes in electrical cabinets at work & have also used it to mount plastic parts to painted aluminium and GRP surfaces. Many motorhomes and caravans are glued together with this stuff - it grips very well (getting a glued part off is a real battle ! ) & doesn't cure totally hard, having a small amount of flexibility.

I think the stuff I am using at present is a Henkel product, but Sika also do an extensive range + there are other manufacturers . Only downside is that the tubes "go off" after opening however you try to seal them.

Nigel B.

Thread: Are we being listened to on the phone
26/03/2021 16:03:59

Mrs B and I came to the conclusion that we were being "listend to" by mobile phones some time ago - too many occurences of being "served" adverts about things we had been talking about for these to be a random occurence.

The price you pay for using Google, Android phone etc.

Nigel B.

Thread: Low head Cap Screws
26/03/2021 13:39:02

Not sure what you mean by "larger sockets" ?

Looking at the the table of dimensions in the link supplied, the DIN screw sockets seem to be one size smaller than would be expected for a "normal" SHCS - an M5 "normal" socket is 4mm AF, where theDIN head M5 screw is shown as 3mm AF in the chart. The other sizes are the same.

Usual "rule of thumb" for a "normal" SHCS is the hex size is one down on the thread size & for button heads and CSK screws two sizes down. i.e a "normal" M6 SHCS is 5mm hex and an M6 buttonhead / CSK is 4mm hex. The DIN screws seem to follow the buttonhead / CSK format.

Nigel B.

Thread: New car - or is it a wheeled computer?
26/03/2021 13:24:30

Another who struggles with some of the dubious "features" added to modern cars here.

My Hyundai i30 has the abominable "auto stop" feature that you have to remember to turn off after every start, or it will stop the engine at the most inopportune moments - positively dangerous at junctions, as it takes what seems like an age to start the engine, deceide which gear it wants to engage (DCT auto) and finally decides to move. Otherwise it has been OK - reasonable mid-50s mpg enocomy, annual (20K miles) servicing, 5 years warranty (not needed anything yet). I tend to go for "one up from basic" spec. to get aircon, central locking & electric windows but stay with reasonably sized higher profile tyres for a more comfortable ride - really don't see the point of 18" diameter ultra low profile tyres on a family car - and fewer "features".

Peter has been luckier than I was with a Toyota Avensis - mine started eating wheel bearings at around 80K & the CVT gearbox developed a whine (no gearbox spares available - £4.5K for a new gearbox, sir ) the main dealer was exasperatingly difficult to deal with to get them sorted under Toyota's almost impossible to access "warranty" & it went rapidly under something of a cloud. The Kia Carens that replaced it was a far more reliable car.

You can't just blame the dealers for diagnostics issues - cars with problems now have to be hooked up online for the manufacturer technicians to interrogate them remotely. I had this with a Ford Transit based motorhome that went into limp mode on the way home from picking it up. The dealer could do nothing without the manufacturer technician's say so after checking the van remotely. Long story short it required 4 new injectors with 32 miles on the clock ! 6 weeks delay to get the "back order" parts to fix it - I shifted that after 6 months (awful vehicle in many respects - very much not one of my better choices ! ) & I later found out that the second owner had to have 4 new injectors fitted again the next year. A colleague at work with a BMW 3 series plug-in hybrid had the on-board battery charger fail - it couldn't be changed by the dealer until it had been checked online by a technician in Munich. He was glad it was still under warranty, as the charger apparently cost £3K.

In many ways life was simpler with points ignition, screw adjustable tappets and carburretors - but then again with my last few cars (mainly Hyundai or Kia) I have done no more than put fuel in for a year / 20,000 miles between services - not even needed an oil top-up.

Nigel B.

ps. Re : 10% ethanol - the reports in various car magazines suggest that there will not be any totally ethanol free fuel available after the change (by September). Some stations that sell more than a certain quantity of fuel will have the "Premium" grade available that will be 5% as at present. I.e. a lower ethanol content, but no longer ethanol free. A pointless sop to tree-huggers IMO that will do nothing for the environment.

Edited By mgnbuk on 26/03/2021 13:30:10

Thread: There may be a delay in some deliveries ...
25/03/2021 08:48:50

a ship of that size becomes a wonderful "sail" to a mere breeze of 30mph.

It has been reported that there was a sandstorm at the time of the incident & apparently it was the wind that caused the ship too deviate from it's course more quickly than they could correct it.

Also being reported by the salvage company appointed to refloat the vessel that it could take several days to sort things out.

Nigel B.

Thread: CNC - Easy as pressing a button - Not
21/03/2021 17:43:04

One did make me laugh I'm afraid - the machine that looked normal, except the enclosure contained noting but orange flame...

Not sure that the operator would have been laughing along with you, Neil. Quite possibly a metal fire - very difficult to extinguish.

At my previous employment we got the repair work for the aftermath of a metal fire on a CNC milling machine. The machine was drilling titanium hubs, using neat cutting oil & there was a fume extracation hose above the working area. A bit of swarf got trapped between the drill body & the part that got glowing hot - no probem whilst submerged in oil an no air present, but when the drill retracted it set the titanium swarf and cutting oil alight. The flames were drawn into the fume ducting, which also caught fire & dropped, burning, onto the machine hydraulic pack. This also caught fire. The main electrical trunking carrying the wiring between machine and control cabinets ran behind the hydraulic tank - this burned through. Apparently the fire was very difficult to extinguish due to the combination of oil and burning metal. The machine ended up being repainted, rewired, had to have a new hydraulic pack and pipework and a replacement cabinet, control system and drives (electronic units damaged due to the wiring harness burning through & shorting while under power) .

There are specialist automatic fire suppression systems available for machines that are at risk of metal fires.

Nigel B.

21/03/2021 17:11:14

I often found myself wondering whether these wonderful modern machines incorporate clutches or other fail-safe provision.

I have come across very few mechanical overload devices - one that comes to mind was on Herbert AL series slant bed lathes that were designed to allow the Z axis ballscrew to move axially in the event of a collision. There was a limit switch on the end of the screw which stopped the machine if the screw was displaced.

Modern (meaning most makes from the last 20 years, maybe more) controls have multiple monitoring functions which will stop the machine if a). they have been correctly configured and b). the event occurs slowly enough that the monitoring has time to intervene before too much damage is done. But such monitoring is far from infallable & it is often a difficult balance between setting up for maximum protection and setting trip thresholds high enough to prevent nuisanace tripping in normal operation.

Nigel B.

Thread: High speed grease!!!!
21/03/2021 15:08:10

In an application that calls for Klúber high speed bearing grease (NBU 15 IIRC) at work I use this equivalent from a British supplier. IIRC the last 400 g cartridge I bought last year was around £30 - a lot less than the Klúber product. This is a very soft white grease.

I used to use Klúber at the last employment, but they were local then (just outside Halifax) & I just collected from them when required. Fastest spindles we did then were for a Marwin router that ran to 12,000 rpm - weighed quantities of grease inserted into the bearings with a syringe, then careful running in by building up the revs over a couple of days while monitoring the spindle temperature. Not just a case of shoving a good finger full of grease into the bearings and straight up to full speed !

Nigel B.

Edited By mgnbuk on 21/03/2021 15:08:59

Thread: CNC - Easy as pressing a button - Not
21/03/2021 11:13:22

Lathes seem to have bigger "bangs" than mills - more energy in the rotating bits at a guess.

I was working one bay over from a medium sized CNC chucking lathe in an oil tool plant where the programmer had failed to put a spindle speed limit in a new program. The part was a long steel tube 8" or so diameter, extended well beyond the headstock and supported on a two point roller steady in the aisle. Being an "oil country" lathe it had chucks at each end of the spindle & the exposed tube was covered with a tubular guard to prevent contact with it. While facing the tube in CSS mode, with no spindle speed limit the revs went very high as the tool approached centre, the tube bent 90 degrees throwing the tubular guard down the shop & levering the 12 tonne machine of the floor & turning it 90 degrees to the aisle. Fortunately no injuries, but a very shaken operator.

At the firm I started my apprenticeship with they had a 4 axis (twin saddle) Churchill vertical bed lathe (one of the machines I was set on to learn how to maintain). One of the older apprentices was running the lathe & was on a piece work bonus - I was giving him a hand loading it while he checked the part just removed to get the parts count up. The parts were stainless castings for ball valves & the two saddles were programmed to cut on both the inside and outside of a flange at the same time. Every so often there would be a clatter as the loads on the component from dulled inserts got too much & the flange twisted off to rattle down into the swarf conveyor. After one of these "clatters" there was also a loud hissing noise - the valve component was fine, but all the top slide keep strip screws had stripped & the whole top slide and turret assembly was just hanging on the bent ballscrew - the hissing was from the ruptured hydraulic and coolant flexible hoses. Took a couple of weeks to sort that out !

A former colleague - who I found out after he left in a hurry was referrd to as "Clanger" by the others - left scars on most of the milling machine tables, scrapped a Renishaw probe and (the cause of his "urgent return to Poland on personal business" ) a crash involving a Gildemeister lathe turret running hard into the tailstock barrel. The next user of the machine reported that the turret wouldn't index - which didn't prove too difficult to sort out - but then the hydraulically operated tailstock barrel seized. Long story short, the 100 mm diameter hardened steel barrel was bent. It had to be ground undersize to get the bend out, hard chromed oversize then reground to size & finally have the 5MT taper reground. All because he would not check his programs before hitting the "Go" button & didn't have the feed and rapid overrides set low while proving out a new program.

Nigel B.

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