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

Hello

This is probably a bit mad but....

...Can anyone suggest any good tips for how to use a diamond whetstone to grind an accurate 'square' (i.e. 90° )  edge to a small piece of steel?

At present my steels are 6mm x 32mm x 1mm (but this may change by quite a lot).

I have worked out how to grind remarkably accurate 45° chamfers (better than 1° ) by using a Veritas honing guide, not unlike this thing:



However, I can't get it to grind much beyond 50 to 55°, let alone 90° !

Any suggestions?

e.g. Do any wheeled 90° guides exist?
(If not maybe one could make one with the help of a small 4-wheeled kids toy, no... ?!)

Fwiw, when I need a more accurate, cleaner finish than a hand file, I often use a diamond stone. But I find that it always requires quite a lot of skill to create a true 90° face when either filing by hand or using a diamond stone... 

J

Edited By John Smith 47 on 26/10/2021 19:23:49

Edited By John Smith 47 on 26/10/2021 19:28:35

Are you trying to do a 90 degree end - i.e. square across from long side to short side, or a 90 degree included angle at some angle to the long side?

Picture (simple sketch) would probably resolve the ambiguity.

Look up “Filing rest” with a pair of rollers.

Dave

I need it to be square to both at once.

Edited By John Smith 47 on 26/10/2021 19:31:05

A four wheeled toy won’t work. A four wheeled design with a parallelogram movement allowing the blade to be free to move downwards as the wheels move apart with downward pressure. Don’t recall seeing anything similar.

? That’s as illuminating as a blown 10w bulb.

A sketch would be simple, but I think you are attempting to face the end of the bar to it’s long axis?

In which case a lathe will just do that, and a roller filing jig will also with appropriate fixture to hold the plate.

Dave

It's mind numbingly simple.

I am cutting piece of c. 1.2mm thick steel sheet by hand using a hacksaw, hand file & diamond whetstone. The resulting dimensions are 1.2 x 6 x 32mm (although the design may change)
I have no lathe. I need all edges of the resulting block to be as close to 90° as possible.

OK, ok.... I'll generate a sketch.

Pull the axle out of your current jig and replace with a longer one so you can mount two larger wheels sufficient to increase the angle it can grind to 90deg.

Edited By JasonB on 26/10/2021 20:27:32

I foresee two problems with Jason's suggestion. One is the requirement to have a slot in the stone, and secondly how will the user know the edge is at exactly 90 degrees (angle changes as the steel is ground away.

Ian P

I'll ignore the first and as for the second if it's the way Brian has got "remarkably accurate" 45deg angles then the change of angle as the blade or workpiece wears is obviously not an issue to him.

Four wheel chariot could hold the 'steels' at 90 degrees.

How many do you need to make John?

If its (say) 10 then slightly oversize blanks could be temporarily laminated together with adhesive under pressure and the resulting block could be filed by hand to exact size by checking frequently with micrometer.

OK here is my 3D sketch

Here's my part:

And here's a face that I want to be at either at 90° (or parallel) to all other faces.


(Although I reserve the right to wish to grind any of the faces!)

EDIT:

Wait, it is also important that all of the sides - particularly the long ones are as close to being parallel as possible. So a tolerance of say 0.2mm would be fine.

So my sketch should look more like this:

In the first instance I only need to make four such pieces. 

If successful, then later I may need to so a short production run of say x64 of them.
 

> and the resulting block could be filed by hand to exact size 
The problem I find with filing is that try as one might it's incredibly hard to not at least very slightly round the edges.

OP

Edited By John Smith 47 on 26/10/2021 21:16:03

Edited By John Smith 47 on 26/10/2021 21:19:23

2 or 3 angle plates and a pair of rollers. Set the whole lot on a flat surface. Adjust the rail to give required size, push up against angle plate to give squareness.

Sketch appears to be at 90 degrees to the intention.

Dave

The earlier 45 degree and 90 degree angles and accurate sizing could have been achieved using the Unimat 3 lathe only which was dealt with in the earlier postings. The 90 degree setting in either axis with accurate sizing and repeatability should be achievable using your Proxxon milling machine with suitable jigs or stops, simples!

Robert Butler

Jason, the main problem with your design is my current hone has a roller rather than a pair of removable wheels. Also I can't just cheerfully destroy it because I am still using it to cut 45 deg chamfers!

I still say a 4-wheeler toy with nice hard plastic wheels & zero suspension could be made to work. You would need to push hard down too keep the wheels on the ground. Maybe really solid a little toy railway carriage...(?!) with a vertical cut through the centre of it. Of course one would need to take care not to accidentally grind any of the wheels....

OR maybe quite a large toy whose wheels straddle the diamond hone without actually touching it? Of course it would need to be held low to minimise vibrations. 

But there MUST be better way.


[Meanwhile I'm still trying to work out what a "roller filing jig" is & whether they exist for flat files...]

Edited By John Smith 47 on 26/10/2021 21:37:50

This:

is a roller filing jig for a lathe.

the 2 rollers guide the file in a linear manner. Traditionally they are used with a head stock division plate to file squares and other polygons onto the end of round stock.

Squint a bit and refer to my sketch and you will see how to make such a thing.

However Robert is correct - use a machine to do the job

Dave

Re filing guides, I was watching this video earlier; the whole thing is quite interesting, but the bit from 2:20 in might be applicable to your requirements. If I've done this correctly, it might even start in the right place.
Something like this gizmo, a square, and a micrometer, should get you excellent accuracy.

Robert Butler - even though
A. I don't really know how to use a lathe and
B. I don't have much shelf space for kit
C. It only has a very small milling table
D. It doesn't have a dovetail pillar
E. I am told that it is better at lathing than milling and does flex somewhat when milling.
F. It would be second hand and be of unknown levels of previous use
G. And come with no tech support of any sort

Yes, I am still regretting letting that Unimat 3 slip through my hands. It was certainly looked like a bargain.

Re machining, yes, fair point. I shall have another got at milling my steel with the little Proxxon, possibly tomorrow. Fwiw, I'll also need to work out how to clamp something with the changed (now much longer and thinner) dimensions. However I have ordered some parallel steels which should arrive tomorrow which should at least help me keep the edges parallel!

Nonetheless, there is always quite a lot of hassle setting things up in order to mill accurately... and in the finish always seems to be much rougher than with grinding. So if there was a good way of filing accurately that would still be interesting.

Dave - I still don't completely understand how the roller guides area held in place correctly. I mean how would one use when your part is in a vice? I would need to get get rollers aligned exactly correct relative to the part...

IF you had a lathe with a large enough headstock bore, (Probably 5 MT to pass 32 mm ) the plate could be gripped in a four jaw chuck and faced

In this way, if the side faces of the plate were square to each other, which i would expect ground flat stock to be, the facing operation would produce end faces square to the rest of the material.

But it looks as if that is an impossible situation for you. This not something that you are going do on your own, without a lot of very careful, and time consuming FITTING work

Where are you located ?

Maybe someone near you could help?

Howard

As a source for carbide, as per my previous video link, may I suggest paint scraper blades such as these.

https://harrisbrushes.com/product/protection-and-preparation/ultimate-super-scraper-blades/

You can pick them up for about £7 a pair off ebay for 65mm ones

Bill

Thanks, I enjoyed that video - almost rather meditative...

But no way am I letting carbide go anywhere near my highly treasured hand files! I don't have any old ones. And I'm not sure I much want to buy some new ones just to trash on some carbide. In principle rollers sound much more sensible, no?

Fwiw, I am located in Oxfordshire.

Questions:
1. Have any of you good folks tried the "Boeshield T-9" corrosion protector that he raves about?

2. What is that black pen he his using for his rough measurements? I need to find something better than my fine black Sharpie marker pens which keep drying out. FWIW, sometimes I have used a fine white pen which I find works better that black in some lighting conditions.

3. I have never come across Layout Blue. Who often & when would you use it? It looks like a really good idea for making scriber lines 'pop' (which unless it is a mirror finish I find really hard to see). Is there a reason why it has to be blue, or is that just a convention? I like the idea of a brush in the cap (no paintbrush to clear) Is Dykem's Steel Blue Layout Fluid the best?

But all of which is rather a long way from my original question:
Machinery not withstanding, is there really no good way to make an accurate 90° grind using a diamond whetstone?

[If all else fails I was thinking of possibly using the side of a large V-bock to which I had stuck a layer of protective, low friction film/paper (e.g. waxed paper?) to create a vertical surface, and then running my steels up and down the side of it as I grind one edge of the steel... ]

Edited By John Smith 47 on 27/10/2021 00:42:09