How can I make an accurate 90° grind using a diamond whetstone?

[Howard LewisParticipant @howardlewis46836]

Departing from the immediate subject of how to produce edges square to a face.

Layout out Blue, sometimes called Spirit Blue, is a very runny prussian blue painted onto work, so that scribed lines are more easily visible.

(NOT to be confused with the blue used when scraping surfaces flat, often referred to as the trade version sold as "Micrometer" blue.

Both are very difficult to remove if you get them on your fingers or hands!

It looks a s if you have to do the job by fitting. Mark out, Saw, File, File and Emery, and then hone/ scrape using a square . It sounds as if you are aiming for a virtually air tight fit.

Not a quick job, but lacking machining to do the majority of the work, about the only way to do the job.,

Howard

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Nicholas Wheeler 1 on 27/10/2021 10:35:50:

[…]

You keep writing you want to grind the edge with your whetstone, and I think that's what is causing some of the problems; whetstones are for refining an already created edge, not roughing them out from a blank.

.

Fair comment, Nicholas

But may I refer you to my post timestamped

04/09/2021 08:52:13

on this previous thread: **LINK**

https://www.model-engineer.co.uk/forums/postings.asp?th=174528&p=2p

MichaelG.

[John Smith 47Participant @johnsmith47]

Posted by Nicholas Wheeler 1 on 27/10/2021 10:35:50:

How much material do you need to remove to produce your edge? That, and how many parts are needed would be the biggest factors in deciding what tool I would use to do the job. Your small production run of 64 instantly elevates it to a machine job for me. 64 parts is not a small run for a home shop! And I wouldn't have finalised the design until I had proven methods for producing all of the parts

 

You keep writing you want to grind the edge with your whetstone, and I think that's what is causing some of the problems; whetstones are for refining an already created edge, not roughing them out from a blank.

 

A) Amount of material to remove

The amount of material I need to remove, depends purely on the skill and accuracy of my cutting the steel sheet by hand, but I would guess between 1 and 2 mm would be a reasonable amount to have to remove. Although if I have my (heavy beast of a) disk sander out could quickly reduce that to 0.5 to 1mm to remove.

To get clear, yes clearly I would not make x64 parts before 'finalising' the design (as best one ever can in these situations).

[Obviously if I am making larger numbers and if the design seems finalised, then I would consider getting someone to laser-cut them, but typically there would be a £60 to 100 setup cost plus 5 to 10 days of delay to factor in… and even then I would still need to get them cleaned-up/resurfaced/deburred and filleted to make sure that they aren't to sharp. ]

B) Machining
I'll have another got at using my Proxxon MF70 after my new parallel steels arrive.

C) Using a whetstone

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

Yes exactly. It's just that I want to keep the face on each cut edge at exactly the correct angle (in this case 90° whilst I refine its surface, and a long a narrow (1mm) surface that is rather tricky.

Btw, yes I have tried sticking them a number of them together with double-sided tape. This definitely helps maintain accuracy but it's rather time consuming to add the tape, accurately stick them together, remove, clean up etc… (plus I keep running out of d/s 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.Yes, I have some Kapton tape somewhere. Good suggestion. Although as I recall it bonds almost too well. What would you normally use to remove it – Isopropanol/Acetone? (I have both).

D) Dykem
Is there anything special about Dykem's layout blue? At c. £15/bottle it's not exactly cheap. Mind you a Jumbo Edding 850 Permanent Marker Pen is c. £9.25, and probably contains a lot less fluid…
– How long does it take to dry?
– How do you remove it?
– How bad are the solvent smells?

 

Thank you for all your thoughts

More later.

K

 

 

 

 

Edited By John Smith 47 on 27/10/2021 12:53:32

[Howard LewisParticipant @howardlewis46836]

You are unlikely to be particularly aware of the smell of the solvents.

Marking and Layout Blue are very difficult to remove from fingers and hands. A pumice stone will remove most but may leave some in the bottom of you finger prints, that will have to wear out!

For small areas, a chisel edge felt tip is adequate, but, easily rubbed off in my experience.

being depressive, am not sure that you have the means of achieving what you want.

Sounds to me as if you need to farm the job out to someone with a surface grinder.

Howard.

[BazParticipant @baz89810]

Howard I told him this when he asked about the sixty four pieces he wanted with a knife edge or some such machined on them. I don’t think he appreciated my advice then and I doubt if he will now. I think I shall be ignoring his posts in future.

[John Smith 47Participant @johnsmith47]

Posted by Baz on 27/10/2021 14:36:48:

Howard I told him this when he asked about the sixty four pieces he wanted with a knife edge or some such machined on them. I don’t think he appreciated my advice then and I doubt if he will now. I think I shall be ignoring his posts in future.

Baz if your advice is "give up & go home" frankly that is pretty offensive in a forum like this.

When are you going to learn that just because someone is asking lots of fundamental questions doesn't mean a damned thing. The reason that I am here is primarily to learn from others, plus contribute where I can – which is somewhat limited given the level of expertise evident in this forum. But just because I don't mentions specific advice does not mean I'm not listening hard to it. Either way obviously I can't follow everyone's advice, not least because quite often it conflicts.

And since you are casting aspersions, I might add that I have already made more than the 64 pieces of the previous design – over 100 in fact. They were all ground to to within 1° and 0.1mm of accuracy and they all worked brilliantly.

But if giving advice pertaining to the accuracy that I require with the resources at my disposal is beyond you, or you find anything else about this thread problematic, then yes please do not visit here nor any of my other threads again.

Edited By John Smith 47 on 27/10/2021 15:55:15

[Nick WheelerParticipant @nickwheeler]

After looking at your sketches and tolerances, I suggest that you're concentrating on the wrong edge!

I would cut the 32mm lengths slightly overlong – no more than 34mm – from accurately prepared 6mm wide strip.

They would be fitted into this slotted brass coloured block, which is 30mm long, and made from however is easiest; milled from solid, bolted/welded/soldered/glued/pinned together from 3 parts.

The black clamp is a simple T-shape, deep enough to compress say 10 parts together when it's clamped in a vice.

The shiny component is one of the parts.

Clamp the whole thing in an accurately trammed vice, mill one end then step over to the other end and mill to size. No grinding needed, just a little deburring.

[JasonBModerator @jasonb]

All very well Nicholas but how does he accurately prepare the 6mm strips and as he does not have a mill upto doing 6mm sidecuts then what to do about machining the ends or making the tee section?

Edited By JasonB on 27/10/2021 16:54:54

[SillyOldDufferModerator @sillyoldduffer]

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

[JasonBModerator @jasonb]

Posted by SillyOldDuffer on 27/10/2021 16:46:30:

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.

Rather you than me Dave, I don't fancy a flycutter on the 1/8" max collet capacity of the proxxon particularly at the 5000rpm minimum speed

Luckily there are no large flat surfaces as the parts are being cut from 1mm thick materail so just the 4 sides.

If the Proxxon is upto it then I would use a 3mm or 1/8" cutter eg max possible and first holding the sawn blank vertically in a vice mill along one long edge. Then flip it over and with the use of a thin flex parallel mill the opposite long edge down to the required 6mm.

You now have an accurate 6mm x 1mm section with ragged ends which can be machined by holding it flat in the vice with one end poking out and cutting with the side of the same cutter. Do one end then swap it round to do the other bringing the length down to 32mm. 

Edited By JasonB on 27/10/2021 17:05:30

[Michael GilliganParticipant @michaelgilligan61133]

Posted by SillyOldDuffer on 27/10/2021 16:46:30:

[…]

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.
[…]

.

One last try, if you will permit me, Dave

When [approaching two months ago], I suggested that John should use diamond ‘hones’ I was specific in stating that he would need to have the appropriate grade[s] for the work … The coarsest Eze-Lap is stated to be suitable for putting an edge on spades, etc. … It is not a whetstone !

The reason that I suggested this is that it is entirely consistent with the limitations of John’s ‘kitchen table’ workshop.

The general approach that he has recently outlined [using a commercial vee-block as his jig] would suffice for working on individual pieces … provided that the appropriate grades of diamond hone are used.

Filing a stacked block sounds reasonable enough … IF you have a decent vice, firmly mounted on a good solid bench.

MichaelG.

[Nick WheelerParticipant @nickwheeler]

Posted by JasonB on 27/10/2021 16:45:41:

All very well Nicholas but how does he accurately prepare the 6mm strips and as he does not have a mill upto doing 6mm sidecuts then what to do about machining the ends or making the tee section?

Edited By JasonB on 27/10/2021 16:54:54

That's more proof that he's not ready to produce the gadget yet. Which has been mentioned several times, in different ways but apparently isn't a useful lesson.

[Jon LawesParticipant @jonlawes51698]

What is this for? Is it a commercial enterprise?

[Anonymous]

Posted by Jon Lawes on 27/10/2021 20:32:47:

Is it a commercial enterprise?

In an early post, IIRC, the OP was talking about building a prototype of a gadget for use in an office. I assume this is the same project, so it could be said to be commercial, although the approach seems to be anything but.

Andrew

[Jon LawesParticipant @jonlawes51698]

I don't have anything useful to add in this instance (I seldom do), but I if the OP isn't being up front with what they are using it for it seems a bit of a cheek to be supporting their own profit with the goodwill of a hobbyist forum. Does anyone fancy popping over to take on my night shift for me?

[John Smith 47Participant @johnsmith47]

Posted by Jon Lawes on 27/10/2021 20:32:47:

What is this for? Is it a commercial enterprise?

I guess that's a reasonable question, since this is a 'hobbyist' forum.

Look, I'm not remotely 'commercial' because I'm doing this project with VERY little money.

I am working in my own shared rented home… and (compared to other members of this forum) I freely admit to definitely being a 'workshop novice'. I am working with very limited funds, and without a dedicated workshop space. I am developing an inventive (patent pending) concept for a novel product. I have only strictly limited personal funds… and raising funds is difficult & extremely expensive as I do not yet have a proven track-record at doing this. So I don't have much money.

Nonetheless my concepts have been well received and I now have introductions to senior management at several of the largest manufacturers in the world of office suppliers/stationery sector, but I MUST have credible prototypes, and I need to make them on a shoestring budget. No, I am not planning to do any actual 'manufacturing' myself, but in line with modern "Lean Startup" thinking, I need to 'iterate' and do quick turnaround physical testing of concepts on users. But… I don't have much money. The intent is to generate "looks like, works like" models of the proposed product with which I can prove that the product(s) can, in principle at least, be manufactured in both A. small and B. in larger scale/mass production, and thereby make a compelling proposition to target licensees. But… did I mention that I don't have much money?

Yes, the intent is to become 'commercial' some day… however the funding is emphatically at the 'hobbyist' level!

 

Edited By John Smith 47 on 28/10/2021 01:14:32

[John HaineParticipant @johnhaine32865]

John, this has been an interesting if frustrating saga, both for you I'm sure and also the many people who have tried to help you. The big stumbling block has always come down to the fact that you want to do things that would be trivial with the right machinery but extremely hard with what you have access to. So here is a suggestion: find out if there is a "Makespace" reasonably close to you that has the right sort of machinery and join it. Or maybe an evening class, or a model engineer that will let you use their machines (under supervision) and help you with the tricky bits. Otherwise you will continue to stumble in the dark and get increasingly frustrated.

I appreciate that you want to do things under the radar to protect your ideas – you say "patent pending". Does that mean you have filed the patent application; or has it been examined so you know the scope of protection; or do you just have an intention to file? If you have at least filed and lodged claims then you do have a modicum of protection, but would no doubt still want to keep reasonably quiet about what you're trying to do. But you must appreciate that when you say things like "an angle must be exactly 45 degrees", or "an edge must be exactly square", if these are impediments to manufacture and people ask why and make suggestions, you might make faster progress if you can open up a bit.

[Ian PParticipant @ianp]

+1

[Rod RenshawParticipant @rodrenshaw28584]

+2 for John H – who clearly has a lot more patience than I have. And +! for Baz, I find these threads have an aweful fascination but I think I have had enough now.

Rod

[Nick WheelerParticipant @nickwheeler]

The more you write about this, the more you prove how far over your head you actually are:

Novel and inventive, no equipment, no money and no experience at any of the processes involved make it very easy to dive into the wrong rabbit hole and dig enthusiastically.

Your insistence on precision finishes from what should be easy parts: if I was going to have 32x6x1mm steel parts(I'm inferring yours are a plate for the magnet to grab), they would be designed to be usable straight of the guillotine from commercial 6×1 strip.

Same thing for the tight tolerances: a watertight box needs the lid to fit accurately to work. An attached steel strip shouldn't. Or if it does, constrain it with other features like ribs moulded into the case.

Credible prototypes prove that the concept works, and illustrate the final aesthetics if they matter. One cobbled together on the kitchen table out of cardboard, string, hot-glue and a Stanley blade painted with £1 gloss black is credible.

That's also how you iterate the prototypes, quickly moving from the glue, through different materials etc, to a production part. Low production and mass produced in the millions parts are going to be very different, even if they do exactly the same job.

You're not iterating, but stalled. I suspect you know this, and have managed the next step which is to ask for help. The bad news, is that often the best advice is to bin your favourite parts of the design and redo them. Which is extremely difficult to take!

I hope that at some point you show us what this thing is.

[duncan webster 1Participant @duncanwebster1]

In production engineering, exactly has no meaning. If parts have to be square, and the right width, thickness and length to some very close tolerance (and made from unubtainium) they will be expensive, not what you want for a bit of office equipment. You can get better than a thou with a file, and some patience. I'd have made 4 to sensible tolerances in the time it has taken me to read this thread.

[John Smith 47Participant @johnsmith47]

John H
On the face of it your Makespace is a good one. Yes, I had been using them, however as you know it is crucial that I am not seen to disclose what I am doing in any public form or further patent claims & sub-claims will not be possible. Either way I have not been using them since the Covid-19 pandemic and with 1 million people infected with Covid right now, now is not the time to start.

Yes I have done multiple prior art searches and yes, I have filed patent claims.
But do I REALLY have to answer all your invasive questions?

Look is it too much to ask for you folks to just confine yourself to answering the simple questions that I have raised?

Why does everyone keep trying to re-design my product for me?

PLEASE just let me dig my own grave, if that's what you think I'm doing… but please can everyone keep their self-righteous egos out of my designs.

If, unprompted, you do choose to make design suggestions, that's up to you and in general I am grateful but the down-side is absolutely no way can I go into details about the reasons for my design decisions. So if that's frustrating please do NOT make design suggestions.

Nicholas Wheeler
Sorry Nick offensive as your personal attacks are, you simply have no idea what you are talking about and it would take too long to correct you. Yes I have done a lot of outsourcing where appropriate.

No, straight of the guillotine bends the plate. It curls on one side and rounds the edge on the other. We all know this. So why am I wasting my breath?
You don't sound like you have much if any experience of fine tolerance and strong magnets. Because if you did you would know that in practice, unbelievably small machining errors can easily cause a x2 change in magnet pull.

Final words
Okay that's it. No more person attacks, please. And no more re-design suggestions, please. If you don't enjoy reading threads that I have started… if you still want to make your personal attacks, if you still want to offer what is completely unsolicited re-design advice PLEASE GO AWAY.

Please can we all just stick to the materials, tools, technology and techniques… and stick to the topics in the actual question!

[John HaineParticipant @johnhaine32865]

I give up. Some people just can't be helped.

[John Smith 47Participant @johnsmith47]

Posted by John Haine on 28/10/2021 15:54:40:

I give up. Some people just can't be helped.

There we agree.

[Nick WheelerParticipant @nickwheeler]

Posted by John Smith 47 on 28/10/2021 16:14:23:

Posted by John Haine on 28/10/2021 15:54:40:

I give up. Some people just can't be helped.

There we agree.

Yes.

I still hope to see whatever is causing you so much hassle.

[Author]

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