Simple grinding rest.

[James Hall 3Participant @jameshall3]

Anyone have experience of this rest?

[James Hall 3Participant @jameshall3]

I'm a fairly new machinist but have come to the point where I want to grind myself some (10mm) HSS tool bits.

Many years of wood turning have taught me that I'm rotten at any form of freehand sharpening – for those I now have an excellent belt machine.

I have the Harold Hall book on Tool and Cutter Sharpening (Workshop Practice Series 38) which gives a design for a simple sharpening rest to go with my bench grinder.

As a rest it might be simple, but making it would, nevertheless, entail quite an expenditure in time and material so I'm wondering if anyone has made/used this design and how effective it is. As usual help/comments/advice from the 'old hands' would be much appreciated.

[martin haysomParticipant @martinhaysom48469]

yes i have made it. it works, i am happy with the results

[derek hall 1Participant @derekhall1]

I made the simple grinding rest and I have to say was dissappointed with it.

The grinding rest itself was easy to make but it was such a faff to mount and set it up to work on a grinder, the instructions on how to build it were ok but details were light on how to use it. Pictures were poor in the book and it was not obvious how to set the rest up even to grind simple HSS lathe tools. It seemed that so much of the rest gets in the way of the actual grinding process and there is a requirement to keep adjusting the rest to try and present the tool at the required angle which became very frustrating and time consuming.

in some attempts the HSS tool had to protrude so far from its holder it was not thought to be a safe practice to be honest.

Most HSS lathe tool angles are not required to be accurate for general machining, most of the time I have gone back to freehand grinding.

Regards

Derek

[MikeKParticipant @mikek40713]

I have the simple rest mostly built, but (of course) not used…as I've gotten away with hand grinding bits pretty well. For what it's worth, I'll point on that Mr. Hall has some pages on his website referencing the simple grinding rest.

Simple rest: **LINK**

Improved mounting: **LINK**

Mike

[HuubParticipant @huub]

I do not grind tools by hand (only for rough grinding). I made this tool grinder that uses holders. I made different holders for different angles. I can stack the holders to combine Horizontal and Vertical angles. I regrind a tool in just a few seconds. I takes more time to replace an insert.

The "diamond" disk is driven by a low torque Nema17 stepper. When ever I use to much force, the stepper will stall, preventing damage to the disk.

[BazyleParticipant @bazyle]

Looks like a good system Huub.
Another easy one is to think of the periphery of a circular grinding wheel. If the top of the tool is exactly on centre the contact point will be at 90 degrees. But if you raise it up a bit the curvature means it will be at an angle. A bit of calculation, or drawing will let you know the height/angle combinations. Then all you need is a block of wiid and some thin strips to pack it up.

[HuubParticipant @huub]

Posted by Bazyle on 19/03/2022 22:36:16:

Looks like a good system Huub.
Another easy one is to think of the periphery of a circular grinding wheel. If the top of the tool is exactly on centre the contact point will be at 90 degrees. But if you raise it up a bit the curvature means it will be at an angle. A bit of calculation, or drawing will let you know the height/angle combinations. Then all you need is a block of wiid and some thin strips to pack it up.

You are right about that.

I want to be sure I always use the same angle. That way, there is very little grinding needed. That saves time and tool life.

I have counted my "angle blocks", there are 2 vertical blocks and 6 horizontal blocks. For inner turning tools, the 2 vertical blocks are stacked for a greater clearance angle.

More complicated grinding (mills, drills, taps, rotary broaches, slitting disks, etc) I do on the small CNC lathe.

[HopperParticipant @hopper]

I am unsure about those grinding rests designed to rest tools on the side of a conventional grinding wheel. Every manufacturer says this is dangerous to do and every workplace and tech college I know of forbids it for safety reasons. And so do all the mainstream professional machining books I have seen.

It is only in model engineering related publications that I have ever seen recommendations to grind on the side of the wheel. Even in old books by respected lifelong machinists like LH Sparey and co.

Why is that?

[Paul LousickParticipant @paullousick59116]

Grinding on the side of stone wheels is not recommended as too much wear can weaken the wheel but the wheel in the photo above is an aluminium (aka aluminum in some countries) disc with diamond particles adhered to its side.

Edited By Paul Lousick on 20/03/2022 07:12:03

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Hopper on 20/03/2022 06:14:41:

.

[…] Every manufacturer says this is dangerous to do …

It is only in model engineering related publications that I have ever seen recommendations …

Why is that?

.

I think it’s because the authors “presume to know better”

They ‘know’ that the Manufacturers, and the Safety Officers need to cater for some idiot who might keep pushing a tool into the side of a wheel … but ‘of course’ they would never do that.

MichaelG.

.

Edit:__ Paul posted whilst I was typing.

His comment about Huub’s delightful little machine is valid, but doesn’t actually address Hopper’s observation.

[quote] I am unsure about those grinding rests designed to rest tools on the side of a conventional grinding wheel. [/quote]

Edited By Michael Gilligan on 20/03/2022 07:22:50

[Paul LousickParticipant @paullousick59116]

I have been known to lightly sharpen a cutter on the side of a normal wheel because of the tool shape that I was sharpening but I would imagine that any sharp grooves that were left in the side of a wheel would be a stress raiser and a starting point for a crack which could cause part of the wheel to come loose.

[HopperParticipant @hopper]

Posted by Paul Lousick on 20/03/2022 07:21:45:

I have been known to lightly sharpen a cutter on the side of a normal wheel because of the tool shape that I was sharpening but I would imagine that any sharp grooves that were left in the side of a wheel would be a stress raiser and a starting point for a crack which could cause part of the wheel to come loose.

Yes I have been known to cheat and use the side of the wheel at home since seeing it as common practice in ME books too. But I would never have done it at work for fear of the foreman kicking my backside until my nose bled. Or fear of getting laughed out of the workshop by my colleagues. But already I can see and feel the damage done to the side of the wheel and how that could over time "neck" the wheel down and let chunks of the wider rim break out under centrifugal/petal force.

As a matter of course, I still always stand well to one side of the grinder until it has run well and truly up to speed, just in case. Those training films I saw as a teenager showing the fatal damage a 12" x 2" wheel exploding can do must have made an impression, even though my 6" grinder is a baby by comparison. Still would not like to cop a face full, or a crotch full.

I think maybe the best option would be to set up a proper cup wheel that is designed to be used on the flat "side" face on one end of your conventional bench grinder. Or use Huub's excellent idea above with the flat diamond wheel and angle blocks. Very nice. The stepper motor to drive it seems very 21st Century to this prehistoric Luddite and very innovative. Never seen that done before. But I suppose the disc could be substituted for the grinding wheel on a bench grinder and used on the "side" without risk.

Edited By Hopper on 20/03/2022 08:20:47

[Michael GilliganParticipant @michaelgilligan61133]

It is interesting to note that the Current HSE Guidance is much less dogmatic than the old Regulations:

**LINK**

https://www.hse.gov.uk/pubns/books/hsg17.htm

… Well worth downloading ^^^
.

.

MichaelG.

[HopperParticipant @hopper]

I dont know, Michael. It still labels it as dangerous and allows only for the side of the wheel to "lightly touch a face adjoining the surface to be ground". So not grinding on the side of the wheel, just allowing it to touch a shoulder lightly in order to grind full up to it on the outer diameter of the wheel. More exceptions and whytofores and wherefores than an insurance contract.

Must have a squiz at the full document when I get a chance. Always interesting to see the latest take on these things.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Hopper on 20/03/2022 09:11:24:

I dont know, Michael. It still labels it as dangerous and allows only for the side of the wheel to "lightly touch a face adjoining the surface to be ground". […]

.

Agreed … but the encouraging thing is that HSE seems to now be informing/educating the user, instead of just imposing regulations.

Methinks that the aforementioned Model Engineers would claim that their designs were only intended for ‘light touch’ sharpening, rather than aggressive grinding.

MichaelG.

[Mike HurleyParticipant @mikehurley60381]

I made the simple rest as one of my earliest 'projects' many years back. I found it very difficult to set up correctly, as the 'ball' design' – while giving a lot of versatility – also made it difficult to set the table at a correct angle – as when you adjust front to back at the angle you want, sods law means that the side to side angle moves also, so you re-adjust that etc etc ad infinitum! I virtually gave up using it, although in a flash of inspiration I modified it to get rid of the ball altogether and it now works fine, even easily allowing me to accurately sharpen the ends of milling cutters.

In your case, when 'beginning' you would probably gain a lot from a simple set up ( something like 'Huub' suggested earlier). You also indicate your lack of previous success free hand grinding: practice makes perfect!

I might add though that actually building the grinding rest was a good exercise in general machining ideal for learning several useful skills.

all the best, Mike

[Andrew TinsleyParticipant @andrewtinsley63637]

I second Mike's comments. I never did get the hang of accurately adjusting the jig. However I tohught it was just my ham fisted methods. But it looks as though others may have had the same problem.

Andrew.

[James Hall 3Participant @jameshall3]

Some interesting observations here – for which thanks – in particular I had wondered about the 'fiddlyness' of setting up and the part of the plastic ball. I shall have to ponder, weighing this against other designs that I might come across.

In fairness to Mr Hall I should point out that (while he obviously favours cup wheels – beyond my means) he does NOT advocate grinding on the side of the wheel but its CORNER which, presumably, counts as being on its periphery – my concern here would be not one of safety but rapid consumption of wheels.

[James Hall 3Participant @jameshall3]

That looks like a very ingenious system Huub – can I ask what the disk is?

[Paul LousickParticipant @paullousick59116]

James,

Do a search on ebay for diamond grinding disk. They are available in lots of different shapes for not too much money. Most are designed for attaching to an angle grinder.

[HuubParticipant @huub]

The disk is a cheap "diamond" grinding disk. A link to the dutch supplier (article 7944) Grinding disk

It gives a good finish even when running (dry) at 800 RPM. For hobby use, in this setup, it will last for years.

[James Hall 3Participant @jameshall3]

Thanks Huub and Paul.

As I don't speak Dutch I'm not sure of the grit size on those discs so it would be helpful to know that.

I'm more and more persuaded to go for Huub's solution, the main problem being finding a suitable motor to power it.

[SillyOldDufferModerator @sillyoldduffer]

Posted by James Hall 3 on 21/03/2022 14:57:11:

Thanks Huub and Paul.

As I don't speak Dutch I'm not sure of the grit size on those discs so it would be helpful to know that.

…

No need to understand Dutch, K240 is the grit size.

HBM discs are available in the UK too.

Dave

[HuubParticipant @huub]

Posted by James Hall 3 on 21/03/2022 14:57:11:

I'm more and more persuaded to go for Huub's solution, the main problem being finding a suitable motor to power it.

I have mounted the disk on a 2 trust bearing axis so the disk is running true without play.
The back of the axis has a hex hole that fits the nut on the dremel.
After a wile, I changed the dremel for the stepper motor that run's very quit.
I threaded the mounting hole of the disk.

The housing fits the dremel thread on one side and the threading of the grinder at the other side.

I choose for trust bearings because the load is only axial.

The parts (without housing)

The parts mounted (without housing)

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