Bench grinder wheels for HSS lathe tools

[Gene PavlovskyParticipant @genepavlovsky]

[Gene PavlovskyParticipant @genepavlovsky]

There are already several topics about this, but I'd still like to ask.

I've bought a "new old stock" Elektra Beckum bench grinder made in 1998. It came with grey aluminum oxide wheels, size 200x25x20, 36P and 60N grit.

I've since bought a Hobbymat lathe and want to grind my own HSS tools. After researching the topic, I've found two resources that give detailed information on grinding wheels (see links at the end of the post). Both of these recommend 60 grit, or two wheels with 46 and 80. Besides that, they mention that the wheel should be relatively soft (one resource recommends I or J, the other H).

I've checked various grinding wheel suppliers mentioned in this forum, and also on a German forum (zerspanungsbude, which I have to read with the help of Google Translate), and there doesn't seem to be a good choice of wheel hardness. E.g. I pick the type of the wheel – white aluminium oxide, size of the wheel – 200x25xWhatever (it seems that all the wheels include several reducer rings to fit different size grinder arbors?), and grit 60, and that's it. Depending on the wheel manufacturer it will come in one particular hardness. Many of them are M or L – way too hard, according to the info I found. The softest I found are from Pferd or Tyrolit, available in hardness K (still somewhat too hard).

So, the question is: is the information in the two resources I've found regarding wheel hardness incorrect, or not as important as they say? The suppliers of the white aluminum oxide wheels say they are specifically meant for grinding HSS tools. Should I not worry about it and buy a Pferd wheel? Or if the advice makes sense, where would I find an I or J hardness wheel of the size I need?

Alternatively, I've read about people (especially woodturners) preferring CBN wheels. I don't have a wood lathe yet, but I do plan to build a treadle lathe one day. Does the expensive CBN wheel make sense for grinding metal lathe tools in a small hobby workshop? If yes, which brand/grit wheel would you recommend?

Thanks!

–Gene

Links:

https://www.practicalmachinist.com/vb/general-archive/grinding-hss-bits-88849/#post193291

https://www.chaski.org/homemachinist/viewtopic.php?f=44&t=75985

 

Edited By Gene Pavlovsky on 26/01/2020 12:09:11

[not done it yetParticipant @notdoneityet]

You have them. Try them and see for yourself. The experience will stand you in good stead for your next purchase of wheels.🙂

[BazyleParticipant @bazyle]

Standard wheels are perfectly adequate provided they have not been misused in the past and on a new grinder would be fine. Look carefully at the surface to see if it has been used for grinding wood, aluminium or mild steel. All no-no's. They clog the wheel, cause it to overheat when you use it and that leads to expansion of the surface which causes stresses that can make the wheel shatter. If it is just a bit old and picked up general dust you can trim the surface with a diamond sort of flat on a stick thing sold on ebay. Don't bother with a single diamond on this sort of grinder, those are for a tool and cutter grinders.
If the wheel is still 'square' ie sides to working face then it has potential. If it has been used so much that the corners have long gone or the middle has a groove in it then it is life expired.

White oxide, friable, soft etc are for professionals and tool and cutter grinders, not freehand sorting out basic tools.

[Gene PavlovskyParticipant @genepavlovsky]

The wheels are absolutely new and don't have any wear. I've removed them to hang them on a string and see what sound they make when tapped by a handle of a screwdriver, they sounded ok to me (although it would be nice to have a sample of how a bad wheel sounds like). They didn't sound like "fine china" to me, which one forum post suggested a sound (pun) wheel should sound like.

I do have a diamond dresser (two, actually). What is the problem using the bench grinder with mild steel? I know aluminum can glaze the wheel (and I have experienced it with my Dremel), but I haven't heard about mild steel doing that. If I do it and the wheel gets glazed, I can always clean it up with the diamond dresser, can't I?

I will certainly use the existing wheels first, as suggested, before ordering anything, however I would still like to know, for my education, the answers to my questions.

[David George 1Participant @davidgeorge1]

This is the information from the Norton web site. As to the sound of a damaged wheel you can hear the crack just like a cracked plate, it dosnt sound right. If you do find a damaged wheel destroy it so no one can use it but they are a rarity as I have only once in 50 years as an engineer found one, but have destroid a few after major crash like trying to past a job under a surface grinder wheel with insufficient clearance ( big bang ).

The Norton bench and pedestal wheels line consists of all wheel diameters and arbor sizes, abrasive types and grit sizes. Our offering answers all metal removal, deburring, shaping and sharpening needs: white aluminum oxide for high-speed tool steels, brown aluminum oxide for carbon steel, and silicon carbide for non-ferrous metals and carbide tooling.

https://www.nortonabrasives.com/en-gb/product/wheels-bench-3sg

Have a look here.

David

[Gene PavlovskyParticipant @genepavlovsky]

Thanks David.

Norton was the manufacturer listed in first link I posted. The link suggested Norton's 38A 60J8VBE, 32A 60J8VBE, or 5SG 60JVS. Searching for these codes gives very few results, mainly in USA.

I'm having a hard time understanding the part numbers on Norton's website. E.g. the 3SG wheels (the link you posted) are listed as available in 2 Diameter, 15 Diameter, 18 Diameter. Everything in the table is in millimeters, but I'm having a hard time picturing 2 mm diameter bench grinder wheel with a 31.75 mm bore hole! Just what in the world is a 2x13x31.75 mm wheel?

I'd like to know which wheels you guys are buying when you need a new one, and from which suppliers, and how are they working for you, for grinding HSS lathe tools?

[IanTParticipant @iant]

I'd like to know which wheels you guys are buying when you need a new one, and from which suppliers, and how are they working for you, for grinding HSS lathe tools?

Nothing that special Gene. The last one I purchased was from Machine Mart – similar to this;

https://www.machine mart.co.uk/p/6-150mm-fine-grinding-wheel/

It's all you need for HSS tooling once you have decent tool rests (e.g. tables) fitted to the grinder. I also replaced the cheap eye guards with some half decent sized ones.

One other point – you will need to be able to clean your wheels.- I used to use a diamond point but recently purchased a silicon carbide wheel dresser that was very inexpensive and seems to work well (easier to apply too).

So purchase a good quality 'fine' wheel – but as importantly – provide good support for the tool and maintain the wheels cutting surface.

Regards,

IanT

[Gene PavlovskyParticipant @genepavlovsky]

Ian,

I'm waiting for a delivery of Veritas grinder rest, that will come in handy for woodworking plane irons and chisels as well. Are decent eye guards sold somewhere, or did you make your own? The ones provided with my grinder are thin plastic, I will try them out of course.

[DalboyParticipant @dalboy]

For my HSS tools I use a grey 60grit wheel for major reshaping and a white 120grit for refining. Like many metals a pot of water to keep the steel cool helps(not that I need to tell many on here).

The advantage of the CBN that woodturners use is that the outer diameter stays constant and give the grind that slight curve to the tool surface that is being ground. Normally most will buy the larger 8" grinder over the 6" to help reduce that curve. They do ring when in use

 

Something worth noting is that not all grinders are suitable for the CBN wheel

Edited By Derek Lane on 27/01/2020 10:23:52

[Mike PooleParticipant @mikepoole82104]

Apart from selecting the type grit size and bond of a wheel I feel that choosing a reputable manufacturer will help to get a wheel that works properly. I would prefer to walk away from a wheel that has no name on it or one from an unknown name. Unfortunately a top brand will cost more but should deliver the expected performance. I feel that there is a big difference between a top brand and a no name, you may get lucky but why risk buying a poor wheel as it is likely to last quite a long time before you need to replace it.

Mike

[Tony Pratt 1Participant @tonypratt1]

I use Abtec for my work grinding wheels, give the site a look. Or Cromwell tools, in my opinion get a named brand.

Tony

[VicParticipant @vic]

Posted by Derek Lane on 27/01/2020 10:22:41:

Something worth noting is that not all grinders are suitable for the CBN wheel.

Any particular reasons? I’m not interested in using a CBN wheel at the moment but may consider it a some point in the future.

[BazyleParticipant @bazyle]

The point about mild steel is that it is relatively soft and gummy compared to a tool steel. So it is like sandpapering gloss paint – the grit gets bunged up by stuff sticking to it instead of flying free.
The 'soft' grits mentioned are not soft like a biscuit but like sandstone compared to granite. The idea is that if the strength is just right (relying on the skill of the manufacturer) then a blunted stone particle on the surface will be knocked off revealing a new grain so the wheel 'cuts' better for longer. Important for production and professionals but not essential for a hobbyist.

[DalboyParticipant @dalboy]

Posted by Vic on 27/01/2020 11:22:38:

Posted by Derek Lane on 27/01/2020 10:22:41:

Something worth noting is that not all grinders are suitable for the CBN wheel.

Any particular reasons? I’m not interested in using a CBN wheel at the moment but may consider it a some point in the future.

Because of the weight of them. Using them on some machines have been known also to invalidate the warrantee.

[IanTParticipant @iant]

Posted by Gene Pavlovsky on 27/01/2020 09:45:40:

Ian,

I'm waiting for a delivery of Veritas grinder rest, that will come in handy for woodworking plane irons and chisels as well. Are decent eye guards sold somewhere, or did you make your own? The ones provided with my grinder are thin plastic, I will try them out of course.

My guards are commercial items Gene but I don't think I have the boxes now – so cannot tell you the make. I had to make adaptors to fit them to the grinder though. They are considerably thicker and larger than the rather flimsy, thin plastic things that were originally supplied with my grinder.

Whilst I'm personally happy with the Machine Mart wheels, I certainly won't argue with anyone buying branded wheels, which will be about twice the price – they are still not that expensive. I wouldn't want to get 'no-name' off eBay but I feel MM sell enough of these wheels that I'm not going to worry about it.

Of course, even a branded wheel will not protect anyone from incorrect installation and usage.

Regards,

IanT

[Mike PooleParticipant @mikepoole82104]

The guards on a grinder should not be relied on as a substitute for proper safety glasses. I find the guards more of an irritation and they are usually flipped up out of the way. Never ever forget the glasses though. A friend was grinding a very small drill that got launched and pierced the lens of his safety glasses and stuck there. I doubt a naked eyeball would have offered much resistance. A change of underwear and some new glasses and he was unscathed.

Mike

[Mick B1Participant @mickb1]

I buy cheap bench grinders and use them with the wheels they come with until they start to vibrate from worn bearings, when I replace with a new cheap grinder. After about 40 years, I'm still on my third one and have never changed a wheel. Dressing stones work up to a point, but a single diamond on a stick is good for finishing with if you can manage a straight and square enough run – if you're any good at woodturning you should have no problem.

IMO the important thing is not the quality of the wheel or the grinder, but the user having put the time in to gain the skills. Get on with that and you'll soon be able to grind any shape tool within its geometric capabilities. Learning to grind drills offhand is a good start.

[David George 1Participant @davidgeorge1]

Hi I have a single point diamond with a nut on the stem so I can follow the rest to get a nice straight finnish on the wheel.

David

[Gene PavlovskyParticipant @genepavlovsky]

Thanks everyone for the comments. Yes safety glasses are a must and I do take safety quite seriously.

I also think that no matter how amazing you are at freehand grinding, it is better to use some simple jig when dressing the wheel, to make sure that the job is done perfectly. A jig can be easily made out of a block of wood with a close-fit hole for the shank of the dresser (or a screw to fix the shank in position).

For this thread I'd like to focus on your preferred grinding wheel manufacturers, grades, hardnesses and bonds.

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