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

1&2, no, and no idea respectively
I use Motorex 645 Protect and Shine, now rebranded as this and available from many motorcycling outlets.
https://www.demon-tweeks.com/uk/motorex-moto-protect-500ml-bic7300615/

3, many folk do use Dykem, though I've never tried it>
Traditional layout fluid would have been a strong copper sulphate solution, with a few drops of acid added.
I've been known to use that, I gave a bottle on the bench, but normally use an Edding 850 marker pen with a large chisel tip. They do the job well, are available in several colours, and can be refilled.
https://www.ebay.co.uk/itm/162513287647

I think I'd re-visit the filing guide idea from the video.
The workpiece you have is already almost to size, and quite thin, so really just needs finishing off.
If you were to hold it in a similar jig and wrap your diamond stone with two lengths of insulating tape, such that the tape slides on the side of the jig, rather than the diamond surface, it wouldn't wear either the jig or the stone.
The same could be done with a file, if you used it for draw filing, rather than cross filing as shown in the video.
Maybe even use a couple of spare bits of your workpiece material to make sleeves to protect the file.
With a bit of thought in the dimensions of the jig design, and material thickness, you should be able to get a repeatable parallel dimension of your workpiece, just by turning over the jig and filing on the other side.

Bill

Having now seen your sketch the veritas type Jig won't be good for getting a true rectangle, really only good for getting the sides at right angles to the face. The suggestion of just changing the axle and roller was to save you actually having to make anything too complicated

A mill would be the ideal tool be it a Proxxon or the U3 with milling attachment.

Your biggest problem with making any jigs is that they really need as much if not more work and accuracy than making the rectangular parts so it's a bit chicken and egg. Without some investment in both time and money I'm not sure if it's worth suggesting anything else.

.

If you are taking that approach [which, in the absence of infinite skill and/or the appropriate tools, seems reasonable] … May I suggest that you buy some Kapton tape in a variety of widths.

It’s readily, and cheaply, available on ebay, but there’s no point posting a link.

MichaelG.

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Ref. https://en.wikipedia.org/wiki/Kapton

Edited By Michael Gilligan on 27/10/2021 08:29:36

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.

Edited By Nicholas Wheeler 1 on 27/10/2021 10:36:10

Edited By Nicholas Wheeler 1 on 27/10/2021 10:42:18

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

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Fair comment, Nicholas

But may I refer you to my post timestamped

on this previous thread: **LINK**

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

MichaelG.

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

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.

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

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.

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

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

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

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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.

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.

What is this for? 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

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?

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