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Member postings for SillyOldDuffer

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

Thread: How can I make an accurate 90 grind using a diamond whetstone?
27/10/2021 16:46:30
Posted by John Smith 47 on 27/10/2021 11:55:54:
...

A) Amount of material to remove

... I would guess between 1 and 2 mm would be a reasonable amount to have to remove. ...


B) Machining
I'll have another got at using my Proxxon MF70...


C) Using a whetstone

> whetstones are for refining an already created edge, not roughing them out from a blank.

...

I have tried sticking them a number of them together with double-sided tape. ...

FYI, the reason why I do need such accuracy is because the magnetic pull between two mating surfaces which have been magnetised is dramatically affected by the closeness of the fit.

i.e. If the surfaces do fit together well, then the magnetic pull will increase dramatically and both a much smaller, cheaper, lighter magnet can be used, together with smaller/cheaper/lighter steels...


D) Dykem
Is there anything special about Dykem's layout blue? ...

A and C. Removing 1 to 2mm of steel is a job for a file or grinding wheel not a whetstone. Whetstones are used to apply a finishing polish rather than remove metal in bulk. Extremely slow and liable to clog. Might be OK to make one or two, but not 64!

This is an example where it pays to make items in bulk rather than one at a time. I suggest:

  1. Superglue ten to twenty strips together into a solid laminated block.
  2. Put the block in a vice and file one side flat. Finish can be improved with a finer file or emery paper rather than a whetstone. Do not expect instant success from filing: it's a skill that needs practice. However, poor filing will tend to damage the outer pair of strips and these can be sacrificed. i.e to get ten good ones, be happy to ruin two.
  3. Turn the block over, make sure the filed bottom is flat on the parallels, and repeat.
  4. Boil the block in a pan of water to separate them and clean up any remaining glue with Nail Varnish Remover

I think the alleged need for accuracy is muddling prototyping with production engineering. At this stage the goal is to prove the concept works, not to produce the final product. In the prototype, it seems unlikely that it's necessary to use a cheaper magnet and cheaper steels. Instead, why not use powerful Neodymium magnets in the prototype specifically so you don't have to produce high-accuracy components.

Refining prototypes for production raise a different set of problems that could and should put off until later. Don't bog down due to unnecessary finesse or unwise cost cutting during prototyping. The prototype only needs to be good enough to show the idea works, and it doesn't matter if the first one was expensive and time-consuming to make.

Normally I'd say a mill would do the job, but the Proxxon only takes tiny cutters and isn't ideal for flatting large surfaces. However, not too difficult to use the Proxxon to make a fly-cutter, and use it to make the 64.

D. Dykem quickly covers large areas of metal and sticks well to it without being difficult to clean off. Takes a few seconds to dry and isn't fussy about dirty surfaces. Doesn't smell much and can be removed with acetone, methylated spirits and probably water - more work. Felt-tips are a good alternative for small areas of metal, though the cheaper ones don't cover or show scratch marks as well as the real thing. Felt tips are more expensive than Dykem or Engineering Blue when a lot of colour is needed. I usually use felt-tips.

Dave

Thread: Lathe Drilling
27/10/2021 10:43:02

I'm baffled by this one because SquarePeg seems to have done everything right.

My chief suspect is tailstock misalignment because a gross error - the 11/32" (8.73mm) drill cutting 9.5mm diameter over a 10mm depth - was reduced by adjusting the tailstock.

If the drill-chuck is clean and straight I'd look carefully at the method being used to align the tailstock. Possibly it seems correct but somehow sets the tailstock wrongly. The evidence of the drill suggests the tailstock isn't aligned with the spindle's axis.

Odd...

Dave

Thread: Guided bus lane
27/10/2021 10:17:42

Posted by Bill Dawes on 26/10/2021 21:39:21:

...we were aware it was a bus lane, red tarmac with bus lane writtem on road but I thought going through that bit of a few metres up to the traffic lights at the main road seemed the lesser of two evils, caught in a bus lane or go back down the wrong way of a one way street.

Bill D.

Bill gets my sympathy - he's describing a chain of circumstances of the sort that lead to accidents. Bill misses a sign and gets into trouble looking for a car park entrance in a strange town, one of the few in the UK that happens to have a guided bus lane.  He was temporarily distracted.

In this case upsetting rather than serious, but such mistakes can be catastrophic. Many crashes caused by airline pilots losing 'situational awareness' and they're trained to deal with emergencies! It's a big problem.

There but for the grace of god go I...

Dave

Edited By SillyOldDuffer on 27/10/2021 10:18:42

Thread: Ferrous, facing, HSS tool geometry
26/10/2021 15:17:02
Posted by Ramon Wilson on 25/10/2021 12:05:14:
Posted by SillyOldDuffer on 25/10/2021 11:50:31:

Having made sure the lathe is OK, grind several more HSS tools. Be careful not to overheat the tip - if HSS goes blue, that section is ruined and has to be ground off to get to a undamaged bit. Plunge cooling over hot HSS is likely to crack it.

Dave

Have to disagree with you there Dave - HSS will hold its hardness at much higher temperatures than that. Carbon steel yes but not HSS. ...

You can push HSS well beyond 'blue' before any degradation of the edge will occur - something that regularly happens when machining En24t for example.

...

Tug

I didn't explain at all well! Whether blue heat matters or not isn't clear cut, and I suggest there's a reason.

Blue indicates HSS got to within one or two hundred degrees C of the point where the steel is damaged and it's true that's not too hot. However, if an HSS blank is heated to blue heat by grinding there's a good chance the sharp tip got considerably hotter than the shank body. If so the edge and metal immediately behind it are done for.

I tend to give advice based on my own cack-handedness! Watching a guy sharpen HSS at an exhibition I noticed he was much faster and cooler than me. In comparison, it can take me several attempts to get the right shape on HSS and in the process I heat the blank up considerably. If I turn the end blue, there's a good chance it got too hot!

Chaps with a steady hand and good eye find grinding easy. It's beginners and clumsy SODs who mess up! The cure is practice, practice, practice...

Dave

Thread: Mysterious Russian Emails
26/10/2021 13:01:03

Possibly the code-like characters are to get past Spam filters and entice humans.

As empty content is a little suspicious and might get an email blocked, they may be putting random characters into the text to fool the machine.

More. One way of detecting spam is to score suspicious words in the text, sending email to the spam folder whenever some total is exceeded. Spam word examples: dollars, prize, earn, guaranteed, promise, free, bonus, money, extra, promotion, deal, special etc, and phrases like 'once in a lifetime'.

Reading random characters, a computer spam filter won't find any words that add to the spam score, and the weirdness might intrigue a human enough to follow the link.

Dave

Thread: pdf's increasingly flagged as 'dangerous'
26/10/2021 10:17:37
Posted by Frances IoM on 26/10/2021 09:07:27:
most I think are because they are http rather than the latest https - for those on landlines it is highly unlikely that the link will be tampered with (ie be insecure) but for those using mobile phones via base stations in cafes etc that will not be the case - Firefox has become much more link security conscious recently

All true but I hope no-one assumes landlines are safe!

HTTP is a clear signal to hackers that a website is vulnerable. HTTP indicates laziness, incompetence or shortage of cash, leading to outdated software and a history of poor maintenance. Hackers take close interest in such sites because they often have multiple security weaknesses that can be used to deliver a wide variety of nastiness to end users. Although landline links can't be tampered with the source could already be compromised.

PDFs are just one of many web content containers that can be got at by the bad guys. Firefox are warning that the whole website could be untrustworthy. Who owns the website and why is it still using HTTP?

Good security relies on vigilant users as well as technology. My advice, don't ignore warnings unless the risk is understood. In particular never spend money or give private details to an HTTP website.

Dave

Thread: Microwave Oven
25/10/2021 17:01:03
Posted by peak4 on 25/10/2021 16:09:12:

Other engineering folk might find the HV transformer useful to make a spot welder.



Bill

But beware! A Microwave Oven Transformer is the most dangerous electrical item in the home. Bad enough they step-up mains voltage to a couple of kilovolts, but the design of the core means there's virtually no limit to the amount of current they can deliver. They cause severe shock and horrible burns. Old Sparky stuff - victims have been known to catch fire...

This image is from a YouTube Video intended to highlight the risks. About 5:30 minutes in:

movarc.jpg

Despite approaching these beasts with extreme caution there have been a number of nasty accidents in the Tesla Coil community.

The answer is simple: don't plug it in until the High Tension winding has been removed!!!

Dave

Thread: 2D and 3D Cad Software Recommendations
25/10/2021 16:31:36
Posted by Tony Jeffree on 25/10/2021 16:09:03:

Answering my own question here...I've downloaded FreeCAD and so far it seems somewhat simpler to use from the GUI point of view than Fusion 360 - especially since the limits were placed on free use of Fusion - so I am going to persevere with it and see if the initial promise continues.

I wrote a Getting Started in FreeCAD thread in 2019.

I use QCAD-Pro for all 2D work and Fusion360 when Joints and Assemblies are required.

FreeCAD is good for single parts which suits what I do - like 3D printing. On the downside, it's a bit experimental guv and has a plethora of features, like Ship Architecture, I'm unlikely to use. (I'd prefer the developers to prioritise the Part and Part Design Workbenches rather than the others!) There are also a multitude of useful but not immediately obvious add-ons hidden away. See the Macro Add-ons button and Tools->Add-on Manager.

Dave

Edited By SillyOldDuffer on 25/10/2021 16:32:20

Thread: Ferrous, facing, HSS tool geometry
25/10/2021 11:50:31

Posted by choochoo_baloo on 25/10/2021 02:16:43:

...

All of this, is to ask: is the generic HSS to blame (cheap bundle from RDG) ie should I upgrade to a better quality HSS blank? Admittedly I'd assumed that on hobby machines at least, HSS was much of a muchness.

...

The HSS might be to blame, but there's a long, long list of other possibilities. Rather than jump to conclusions about 'quality', I prefer to isolate causes methodically.

When things go wrong, it could be due to the Tool, Material or Operator. Perhaps all three.

Operators are major suspects. Beginners often have hazy ideas about tools and materials, and are quite likely to leap into the deep end by tackling jobs an expert would approach cautiously. They might believe a clapped-out second-hand lathe is in perfect working order or have stripped and re-assembled a good one incorrectly. Might have fitted a QCTP before confirming the lathe cuts OK with a plain tool-post, and not realised the QCTP is wonky. Possibly, the HSS got too hot during grinding and was cracked by cooling too abruptly in water.

Not all materials machine well. Some are easy, others all but impossible. It pays the beginner to start with straightforward materials, and tackle awkward customers later. Silver-steel is a little difficult.

Tool problems are another complication. Choochoo's HSS is only one part of the system. If everything else about the lathe set-up is OK, and the HSS fails again, then maybe the HSS is unsuitable. Or perhaps not: often assumed there are two sorts of HSS, 'quality' and 'rubbish'. Actually there are seven different types of HSS, and not understanding which is which opens the door to trouble. Though ordinary M2 cuts metal OK for me, it's not as suitable for lathe tooling as M42. Possibly Choochoo's HSS is for wood-working... )

Be nice if all my workshop problems were due to poor quality tools and materials. It's not true. Starting out as a self-taught learner I had failures galore, but get much better results today. No magic or special gear - the big difference is I've learned a lot! (And still have a long way to go.)

If I was Choochoo, I'd start by practising on leaded Mild-steel with the HSS tools mounted in a conventional tool-post. If there's trouble, check the lathe for untoward movements.

Having made sure the lathe is OK, grind several more HSS tools. Be careful not to overheat the tip - if HSS goes blue, that section is ruined and has to be ground off to get to a undamaged bit. Plunge cooling over hot HSS is likely to crack it.

If the suspect HSS cuts leaded mild-steel OK from the ordinary tool-post, try the Silver Steel. If silver-steel cuts OK switch to the QCTP and confirm that's good too. It will be necessary to experiment with feed-rate, RPM, and depth-of-cut for best results. Dump the HSS only when confident it's been nailed as the cause - guilty beyond reasonable doubt. The investigation has extra value if it flushes out other problems. Persist, and all will be well.

Dave

Thread: Collets for Myford tailstock
25/10/2021 10:10:59
Posted by JasonB on 23/10/2021 15:51:42:

Dave, you don't clamp the tailstock to the bed so the tap pulls it along. You then either need to stop the spindle at the right time or loosen the keyless chuck. I tend to just turn the chuck by hand while gently pushing the tailstock towards the work, might be different if I had a batch to do but mostly it's just one or two.

Thanks Jason, I shall give it a try. Still concerned about what happens to the swarf though.

Ages since I last snapped a tap, perhaps today!

smiley

Dave

Thread: Saving the Planet or is it ?
24/10/2021 19:26:10
Posted by Samsaranda on 24/10/2021 18:30:30:

...

I think the establishment will have a hard job selling heat pumps instead of gas boilers, how long till this pipe dream crashes and burns and we continue with gas boilers. Dave W

Heat Pumps may be a pipe dream, but gas boilers are becoming a nightmare! Since January the wholesale price of gas has quadrupled, bankrupting no less than 12 UK energy companies whose Fixed Tariff contracts prevented them from passing the increase on to customers. So far variable tariff customers have been protected by the government price cap, but this will be increased soon.

Wholesale prices have risen before winter demand kicks in and is a worldwide phenomenon. In future we can expect to pay more for gas. People will dump gas boilers when they become more expensive than the alternatives.

I wonder what we'll be paying for gas this time next year? Nothing changes minds like a big bill!

Dave

Thread: CAD program that can import PDF for scaling
24/10/2021 17:29:22
Posted by blowlamp on 24/10/2021 16:27:44:
Posted by SillyOldDuffer on 24/10/2021 15:23:05:
Posted by blowlamp on 24/10/2021 14:13:09:

MoI will import a PDF vector file directly with all curves remaining editable.

...

I'm with Jeff Dayman on this because PDF has so many limitations. ...

Much depends on how the PDF was produced in the first place. A 'text' PDF might contain character text which can easily be Word Processed, or a bitmap image of the same text that can't be edited at all.

If a technical drawing in a PDF was captured as a bitmap then a meaningful DXF can't be extracted from it.

If the technical drawing was captured in vector format, it is possible to create a DXF but as Jeff explains it's highly likely that drawing information will be missing and mangled. Internal drawing features like layers (containing construction lines), blocks, dimensions, snaps, scale, units, poly-lines, and splines etc have to be recreated manually.

...

Dave

I can assure you that if the PDF is a vector file, then the curves can be edited and scaled in MoI.

Martin.

The problem is PDF not MOI. I don't doubt MOI will read vectors, but they're only useful up to a point. MOI can only work with what's in the PDF, which may be superficial. Put a paper plan into a scanner, select PDF as output. and see how well MOI converts the result. Or not!

A 3D-cad package's file format can produce an SVG and the SVG can happily be converted into gcode. However. information is lost at each stage making it hard to reverse the process. gcode can't be converted back into the original SVG, and SVG can't be converted back into the original CAD format. PDFs are the same: what's extracted from them is more-or-less lacking compared with the original. PDFs lose information compared with a real DXF.

Nothing wrong with PDFs for their intended purpose, but they're not a good way of transferring technical drawings between CAD packages. Hurrah if it works, but don't expect much.

Dave

24/10/2021 15:23:05
Posted by blowlamp on 24/10/2021 14:13:09:

MoI will import a PDF vector file directly with all curves remaining editable.

...

I'm with Jeff Dayman on this because PDF has so many limitations. May help to understand that PDF is a container format for rendering documents, not a good way of recording technical drawings.

Much depends on how the PDF was produced in the first place. A 'text' PDF might contain character text which can easily be Word Processed, or a bitmap image of the same text that can't be edited at all.

If a technical drawing in a PDF was captured as a bitmap then a meaningful DXF can't be extracted from it.

If the technical drawing was captured in vector format, it is possible to create a DXF but as Jeff explains it's highly likely that drawing information will be missing and mangled. Internal drawing features like layers (containing construction lines), blocks, dimensions, snaps, scale, units, poly-lines, and splines etc have to be recreated manually.

However, I think it's worth trying a PDF conversion because it might save time, but don't expect much of it. Simple drawings convert well enough, but a complex drawing probably needs so much work it's better to do the whole job manually.

Most CAD packages don't read PDF files making it necessary to convert to DXF yourself. I think this is because PDF conversions are so haphazard that CAD vendors don't support it because disappointed users would flood their help desks with impossible to fix problems!

Nearly all 2D CAD packages can import drawings in any format as an image and store it on a separate layer so it can be traced over. Tracing allows the operator to correct for perspective and other errors. It also produces a genuine CAD file that converts cleanly to other formats without losing information, and rescaled as necessary.

Dave

Thread: Correct Drill Bit For 3/8 UNC Tap
24/10/2021 11:08:51
Posted by Alain Foote on 23/10/2021 21:53:30:

14.75 mm is the tapping size for 3/8” British Standard Pipe Thread which is 19 tpi. As previously mentioned the tapping drill for 3/8” UNC is much smaller at around 5/16”.

Ah yes! Watch out for pipe.

BSP is weird because 3/8" refers to the inside diameter of the pipe, not the outside diameter.

In contrast, fasteners always refer to the outside diameter as in 3/8" UNC, Whitworth, BSF etc, but note that the exact tapping drill size depends on the thread form and pitch too. Although there are formula, the easiest way to find tap drill diameters is to look them up in a table.

I recommend buying a copy of Tubal Cain's Model Engineer's Handbook. In addition to the usual tables, the discussion section on %thread engagement is well worth reading. Although I also have heavy references like Machinery's, I usually start with Tubal Cain because he targets small workshop needs so well, often with pertinent advice.

Dave

23/10/2021 20:53:47

14.75 doesn't sound right.

This tap chart suggests 5/16" which is 7.94mm. I'd round that up to 8mm, or even a bit bigger. (Tap drill sizes given in tables are for a tight fit, which puts a lot of strain on the tap. In home workshops it's common to drill a little bigger than recommended because it makes life easy for the tap in exchange for a moderate reduction in strength. Don't do it if the fastening has to be full-strength.)

Dave

Thread: Collets for Myford tailstock
23/10/2021 15:27:26

Could some kind person explain how power tapping is done in the lathe when the tap is held firm in the tailstock, whether in a collet or a drill chuck?

On the lathe I tap by hand with a T-wrench kept straight by a spring-loaded plunger held in a drill-chuck. As the tap goes in, the plunger extends, allowing movement where needed. It's also possible to eject chips by going backwards.

When power-tapping, is the tailstock left loose so it's pulled along as the tap goes in, or does the operator drill in by spinning the wheel? Also, how are the chips dealt with? Does the method require spiral taps rather than ordinary ones? I'm having difficulty visualising how it works without breakages!

Although it feels like I've owned a lathe forever, I've never tried power tapping with one. Blast it, I'm still a beginner!

Dave

Thread: Myford ml7 "parting off"and "max working size"
22/10/2021 22:02:11
Posted by von dutch on 22/10/2021 17:28:21:

Plus I agree I don't think I ever once used power feed to part off in my apprenticeship or was shown .

Parting-off by hand is a required apprentice skill because not all lathes have self-act.

Doesn't mean manual is the best or only way to do it. Use the facility if it's available because machines are steadier than humans, especially unskilled ones.

CNC machines always part off automatically ...

Dave

Thread: Ferrous, facing, HSS tool geometry
22/10/2021 18:14:46

Sparey's "The Amateur's Lathe" is my bible when it comes to HSS.

One of my older books, can't find the stupid thing, tabulates a full page of different tool shapes for roughing, finishing and other purposes. I suspect the variety of shapes date from the Carbon Steel era: in comparison HSS is very forgiving.

Writing in 1950, Sparey said "many tools of old-fashioned shape have become redundant. " Of knives vs round for steel, he says "They are much to be preferred to the round-nosed tool usually recommended for amateur use on steel, as these invariably produce chatter. A good knife tool will do 80% of amateur turning."

With a knife, Sparey suggests finish is achieved by setting the tool almost parallel to the work to produce a rubbing action in conjunction with slow turning speed, fine-feed, and plenty of lubricant. Works for me.

Be interested to read what others think, but I mostly use the same HSS tool for roughing and finishing steel. Admittedly I don't do exhibition work but it doesn't seem necessary to fuss with different tool profiles. Sharp is better than rounded and it is necessary to experiment with feed-rate and depth of cut

Dave

Thread: Help with a broken Sieg Super X3
22/10/2021 13:18:27
Posted by Andrew Johnston on 21/10/2021 21:37:20:
Posted by JasonB on 21/10/2021 20:47:07:

I'm not sure if you can test the Brushless motors in the same way as the Brushed.........

I'm fairly sure it isn't possible. ...

Andrew

Just to confirm it isn't possible to test a Brushless DC Motor with a battery. Brushless motors are more like three-phase AC motors than the ordinary DC types. The electronic controller pulses the coils in sequence to produce a rotating magnetic field. As the pulse lengths and spacings applied to each winding are timed accurately, it's unlikely dabbing wires with a battery will prove anything. Testing the windings for continuity with a multimeter might usefully detect a duff winding, but that's about all that can be done. Unless someone knows different!

Brushless DC motors have many advantages over other types of electric motor, but they won't work without an electronic controller.

Dave

Thread: Myford ml7 "parting off"and "max working size"
22/10/2021 12:47:01

Parting off is difficult because there is so much to go wrong. Higher than normal cutting pressures are applied and the cutter is liable to dip and dig in if there is any flex in the tool or tool-post, or if the saddle can shift, even slightly. Motor and belts are pushed hard, perhaps causing stalls and slippage because the cut requires more power than normal.

Also necessary for the tool to be at a right angle, for lubrication and cooling to be applied, and for swarf to be cleared out of the slot. Cuts have to be applied steadily at just the right rate by the operator because dig-ins and tool-blunting rubbing are likely unless you get the feed spot on.

All these problems multiply with increasing diameter.

Much easier to part-off on a heavy powerful lathe in good condition than a small bendy worn or maladjusted machine. Myfords aren't particularly rigid or powerful and need all the help they can get!

  • Avoid parting off difficult materials especially in large diameters. Many Aluminium alloys are 'difficult' because swarf tends to weld to the cutter and blunt it. Any metals that work-harden, such as stainless-steels, are 'difficult'. Necessary to get the feed-rate 'just-so' before parting off. It comes with experience.
  • Do everything possible to tighten up the lathe - adjust gibs, lock the saddle, minimise tool over-hang etc.
  • Don't mount the parting tool in the top-slide, or even worse, a QCTP. Instead, buy or make a solid rear-mounted tool post, heavier the better. Top-slides and tool-posts are relatively bendy and they put a lever action on the saddle. A 'Gibraltar' tool-post being a short stubby lump mounted directly on the saddle transfers cutting forces straight down and is less likely to twist the saddle on the ways.
  • If power cross-feed is available, use it. Power cross-feed is considerably steadier than a human operator.

My mini-lathe was so fiddly at parting off I preferred to saw and tidy up. My WM280 has no such limitations. With power cross-feed it parts-off OK from it's 4-way tool-post, and is almost fool-proof parting with the rear tool-post provided everything is snugged up. If there's going to be trouble it's parting off large diameters, like your 2"...

Dave

Edited By SillyOldDuffer on 22/10/2021 12:47:48

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