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HSS tool sharpening

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Roger King 119/11/2019 13:39:51
24 forum posts
2 photos

I'm a bit nervous about asking this question, as every search I've done on this and other forums has so many different answers I usually give up and turn the telly on...

What should I use to sharpen HSS tools in my Myford? I have a decent Bosch bench grinder which currently has two grey wheels, a fine and a coarse. I am using the lathe for car modification and restoration, so pretty much the only material I work is either steel or (rarely) aluminium. I still need the grinder to be able to grind and rough finish parts without changing wheels.

I've seen CBN wheels, but not sure how good they are for general use, and they are very expensive. Should I just be looking for a fine grey wheel, and a pink one for sharpening? If I get white, pink, green, blue or whatever can I still trim parts on those, or would that wreck them for tool sharpening?

I need to keep it simple....

Old School19/11/2019 13:49:49
263 forum posts
8 photos

The the wheels on the grinder will be fine for HSS, the coarse one for roughing to shape and the fine one for finishing.

Martin Kyte19/11/2019 13:51:25
1511 forum posts
24 photos

Leave it as it is for the time being and by a small fine diamond stone, credit card type would do, and use this for honing the edges once you have shaped the tool. knife tools are simple in shape and very forgiving in terms of geometry. You should be able to refine the cutting edge and generate a small radius by hand just using the stone.

The wheels that normally come with bech grinders are a little on the corse side for tool grinding without some kind of second process to get rid of the ridges.

regards Martin

Edited By Martin Kyte on 19/11/2019 13:51:54

David George 119/11/2019 13:52:21
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969 forum posts
313 photos

If it was me I would have another grinder with white or blue aloxite wheels of two different grade probably 60 grit and 150 grit to finish on to grind HSS tools.

David

ega19/11/2019 13:59:33
1335 forum posts
109 photos

The general run of bench grinders have inadequate tool rests for our purposes - flimsy and limited in adjustment - and it may help to make or buy something better.

not done it yet19/11/2019 14:13:15
3556 forum posts
15 photos
Posted by Martin Kyte on 19/11/2019 13:51:25:

Leave it as it is for the time being and by a small fine diamond stone, credit card type would do, and use this for honing the edges once you have shaped the tool. knife tools are simple in shape and very forgiving in terms of geometry. You should be able to refine the cutting edge and generate a small radius by hand just using the stone.

The wheels that normally come with bech grinders are a little on the corse side for tool grinding without some kind of second process to get rid of the ridges.

regards Martin

As above. ‘Sharpening’ would only need the fine wheel, even if the tool were considerably blunted. Often simply hand stoning and/or honing the cutting edge is sufficient.

Metalwork is much like woodwork, where tool sharpening is concerned - little and often is better than major reshaping.

Edited By not done it yet on 19/11/2019 14:13:54

Dave Halford19/11/2019 14:36:21
489 forum posts
4 photos

Your current use of the grinder would imply the existing stones will need dressing and it is wise not to want to swap wheels about.

Proper tool grinding wheels can be softer to stay sharp and reduce clogging, read the specs carefully, wheel colours seem to vary depending on who made them.

Should you not be using an angle grinder for your rough trimming?

Bazyle19/11/2019 17:59:00
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4790 forum posts
187 photos

Posted by Roger King 1 on 19/11/2019 13:39:51:

. I still need the grinder to be able to grind and rough finish parts without changing wheels.

Does this mean you are using the grinder for non-sharpening activities? They will get clogged if used on mild steel. A belt sander is better for this.

If you do think you need a better tool rest just get a block of solid non wobbly wood up to centre height, perhaps with a sheet metal or paxolin top to give a smooth running surface. Then the curve of the wheel gives a curve with a suitable clearance angle, or maybe pack it up 1/8 if it doesn't look sharp enough. No need to get over fancy.

Roger King 119/11/2019 19:05:09
24 forum posts
2 photos

The tool rests on my current grinder are pretty substantial, I think they're OK.

I have a full range of grinders to hand with various discs installed for working on the large parts - 1mm cutter, grinding wheel, flat flap wheel, plastic paint-remover etc. but for small brackets and braces etc. an angle grinder's too big.

I think I'll try a pink/white aluminium oxide for fine and see where I go from there. Must get a diamond stone, too.

Thanks all!

Derek Lane19/11/2019 20:22:27
avatar
235 forum posts
56 photos

I use a record power grinder with a course grey wheel one side and a wide white wheel on the other. I use the white wheel a lot for sharpening HSS tools these normally only need a very quick touch up.

CBN wheels are better suited to slow running grinders and are great for HSS tools and cutters

Howard Lewis19/11/2019 20:24:57
2440 forum posts
2 photos

If you change the wheels on your bench grinder, DO use the paper washers on each side of mthe wheel!

Then dress them,so that they run true, to minimise vibration.

The mangles quoted for clearance, and rake angles do not have to be correct within a minute. A degree or so either way is unlikely be a disaster.

honing the tool with a diamond should really "do the business" If you choose to put a small radius on nthe edge, it will improve surface finish, BUT dot modify the edge so that the lower part of it rubs before mthe mcutting edge. That way leads to problems!

The cutting edge must be on the centreline of the lathe. NOT above it! Make yourself a Centre Height Gauge. It will aid tool setting, save time and frustration and give better results.

Personally, I am a great enthusiast for Tangential turning tools. Once ground, with the sharpening jig, they are easy to set to centre height with the gauge, and are an absolute doddle to sharpen. There is only one face to grind on the HSS toolbit. At least two designs have been publicised in MEW over the years (Although both really require some milling to be done ). Alternatively, and more expensively, you can buy the Eccentric Engineering ones, which come with a sharpening jig.

Whatever you use, when grinding, do not overheat the the tool tip. The blue may look pretty, but it will probably mean that the edge is soft. Better to give it a rest to cool slowly rather than quench in cold water, and risk micro cracking.

HTH

Howard

Lee Rogers20/11/2019 12:07:30
avatar
6 forum posts

All of the above regarding the tool rest stability /size, dressing the wheels as needed My 2Ps worth buy a high magnification glass or jewelers loup, it will sharpen your skills as well as your tools.

Pete Rimmer20/11/2019 12:11:51
470 forum posts
19 photos

Most problems I see people having with grinding lathe tools is down to using a blunt wheel. The first time you use a blunt wheel after it has just been dressed will really open your eyes to the need for it.

Roger King 120/11/2019 12:16:11
24 forum posts
2 photos
Posted by Lee Rogers on 20/11/2019 12:07:30:

All of the above regarding the tool rest stability /size, dressing the wheels as needed My 2Ps worth buy a high magnification glass or jewelers loup, it will sharpen your skills as well as your tools.

As a retired dentist, for close-up work I wear the surgical loupes I used to wear all day long. They cost enough, might as well get my money's worth. At least I don't have to keep the work area sterile. So much for retirement...

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