Proper tool grinding?

[AjohnwParticipant @ajohnw51620]

There is a lot of confusion about getting hss hot when grinding it. The cutting edge is very fine so if some goes blue the actual edge is likely to have become a lot hotter. People seem to forget that it's tempered after hardening to improve the grain structure. Overheating it isn't a case of spoiling the hardness but it is likely to spoil the temper.

http://www.totalmateria.com/page.aspx?ID=CheckArticle&LN=EN&site=kts&NM=57

John

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Edited By Ajohnw on 06/08/2016 15:07:42

[Russell EberhardtParticipant @russelleberhardt48058]

Getting back to the original question, I have built H.H.s grinding rest (the original one in his "Milling a complete course" book). I rarely use it for grinding lathe tools other than for screw cutting. I usually find off hand grinding quicker and sufficiently accurate. However it is used for end mills, slitting saws and for four facet drill grinding which it does well.

Russell

[BazyleParticipant @bazyle]

BTW when people talk of 'off hand grinding' do they mean holding the tool in mid air or just using the dinky as supplied rest as a fulcrum to get rough angles but not having a more sophisticated method of setting angles and ensuring the tool stays aligned as it is ground? I'm taking it that a Clarkson or Quorn etc is a stage beyond what we are considering in this thread.

[EugeneParticipant @eugene]

Could anyone comment on whether this is a good course of action for an ambitious beginner to precision tool grinding?

Yes. I've done just that recently and found Harold's simple jig a very useful tool.

As a raw beginner I found off hand grinding dispiriting and tedious; it took a long time to produce something that wasn't any good. Harold's jig has moved me on from there.

You should be aware that there is a big difference in time and effort between sharpening an already formed tool and shaping one from the blank. I use a thin blade angle grinder to rough out a blank before sharpening it with the simple grinding rest with very good results.

Thus far I've only made lathe and shaper tools from either HSS or silver steel; no drill sharpening or milling cutter sharpening, so I can't comment on those aspects.

The construction of the jig was a bit of a challenge for me, I'd never done anything like it before, but it taught me a lot. The dovetail slide was the most difficult part but I managed it in the end; I've since seen another version with just a simple box type clamp and it works equally well. I don't have a mill, just a milling slide for the lathe … my tip would be to go the box clamp route.

On a seventy year old half horse lathe, using a knife tool formed with the angle grinder and sharpened with the jig, I can take quarter inch cuts off diameter with no problems … good enough for me.

In short go for it.

Eug

Edited By Eugene on 06/08/2016 19:26:20

[EugeneParticipant @eugene]

BTW when people talk of 'off hand grinding' do they mean holding the tool in mid air or just using the dinky as supplied rest as a fulcrum to get rough angles but not having a more sophisticated method of setting angles and ensuring the tool stays aligned as it is ground?

Bazyle, for me as a novice, off hand using the "dinky" rest (I have other nouns available) was just as hopeless as the air shot. Harold's rest has been a big step forward.

Eug

Edited By Eugene on 06/08/2016 19:28:23

[AjohnwParticipant @ajohnw51620]

Posted by Bazyle on 06/08/2016 15:43:47:

BTW when people talk of 'off hand grinding' do they mean holding the tool in mid air or just using the dinky as supplied rest as a fulcrum to get rough angles but not having a more sophisticated method of setting angles and ensuring the tool stays aligned as it is ground? I'm taking it that a Clarkson or Quorn etc is a stage beyond what we are considering in this thread.

I use the tool rest on the grinder and angle the tool bit to get the angle I want. I may do tiny touch ups on the side of the wheel free hand but more often that not some part of the tool bit will be on the rest.

It's also possible to make a new rest or sometimes set the one that on them high and still nearly touching the wheel so that the angle needed is ground with the bit flat on the rest. Personally for that I would set it at a height where the centre of the tool was at the tangent angle needed. The top of the tool will be a bit more acute and the bottom at a bit of a lesser angle.

What one usually get with a tool grinder is an accurately running grinding spindle that has no vibration once the wheel is dressed and various jigs mostly for sharpening things. It may also be possible to draw the edge been sharpened across the wheel rather than just plunging it in which will give a better finish. Cuts are literally thou's. The same can be done off hand grinding but it's not so easy to do.

I've already described the sort of tool grinder that is used on lathe tools – an adustable ramp maybe with a guide and a motor with the wheel on the end of it. Often flood cooled and may even have a wheel on them that is more intended for lapping them. There may be adaptations for a more conventional tool grinder. I've never seen one. I have seen several of the ramp type including the wooden one I mentioned.

John

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Edited By Ajohnw on 06/08/2016 20:09:48

[NJHParticipant @njh]

I find this little sander useful to just touch up a tool from time to time. With the QCTP it takes only a few seconds to do.

Norman

[Boiler BriParticipant @boilerbri]

Gents,

I made a tool out of hss yesterday to put a small groove in the face of the end cover on the piston valves on the 5" brittania that I am re building. There was no gasket or anything between the faces when I dismantled it.

The groove only needed to be 1.5 mm wide and about the same depth, as I did not have a parting tool so small I ground a piece of 8mm hss up. First I used the hand grinder with a slitting disk in to cut away the bulk of the metal. To keep it cool I I used a rag soaked in water and kept smothering it between cutting steps.

When the shape was something like I off hand ground it on a fine when on the 6" bench grinder. Slowly.

To put the fine finish on I used a face sander like Normans. This I have had for years, I made it for sanding model boat frames to shape when I was about 21. It is the best tool I have. Anyway the finish it puts on is ideal for tooling.

I learned this technique from a chap no longer with us, and he made parts for Kent introl valves by the hundreds using hand ground tools before tipped tools came out.

I suppose there is no politically correct way of doing things only ways that work for you and you have good results from. Some chaps can just naturally do things and are good at it while others worry and stress over whether they are doing it correctly? Human nature I suppose.

Bri

Edited By Boiler Bri on 07/08/2016 05:13:46

[AjohnwParticipant @ajohnw51620]

I described the wooden ramp version because it would be very easy to make even from steel. The other aspect is that a decent 2,800 rpm motor is likely to run a lot more smoothly than some off hand grinders and the wheel can be mounted correctly on home made parts. While a decent motor and wheel may cost it's probably going to work out a lot cheaper than a true running well balanced industrial off hand grinder. All of the usual jigs could be used with it and very probably give much better results. It should even be possible to make a jig to dress wheels correctly. The run out on new wheels on some off hand grinders is disgusting. I have an 8" Nutool grinder I bought years ago and it runs so smoothly it doesn't even need bolting down even when it's new undressed wheels were fitted. It seems to be hard to find reasonably priced grinders that good now.

John

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[Howard LewisParticipant @howardlewis46836]

The average bench grinder is O K for grinding lathe tools, but is probably a bit sloppy for accurate grinding of smaller drills. As an Apprentice, my Turning instructor taught us to grind drills, but usually larger than an Inch. He did say that smaller drills were more difficult.

Harold Hall's grinding rest must be an improvement, since it removes a lot of the flex present in many bench grinder rests, AND adds precision.

Making a Worden is not THAT difficult. Even I managed it; and extra accessories for it. Others have made it even more versatile.

A useful bit of kit, not only for lathe Tools, but also for Drills and Slitting Saws. Have yet to pluck up courage to sharpen End Mills or Slot Drills, but the day will come!.

The Worden makes a super job of toolbits for Tangential turning tools. And Four Facet ground drills are a joy to use.

With a diamond wheel, Carbide tools can be resharpened.  

Howard

 

 

Edited By Howard Lewis on 08/08/2016 22:44:45

[AjohnwParticipant @ajohnw51620]

It wasn't a spelling mistake when I used the term WOODEN RAMP Howard, Just in case anyone thought it was.

Personally I would use MDF though. Even if I used metal for the ramp and jigs I would still be inclined to use MDF for the rest.

The biggest problem with making grinders including the Worden and others is that ideally it needs an IP44 or other more or less sealed motor as grinding dusts doesn't mix well with motors.

Green grit wheels also make a decent job of sharpening carbide. Even reshaping them.

John

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Edited By Ajohnw on 08/08/2016 23:08:00

[Speedy Builder5Participant @speedybuilder5]

I came across this Southbend link which may be of interest to some of you. Just bear in mind that some of the HSS tool holders present the tool at a fixed rake angle.
**LINK**
BobH

[mark smith 20Participant @marksmith20]

Posted by Speedy Builder5 on 24/01/2017 09:20:58:

I came across this Southbend link which may be of interest to some of you. Just bear in mind that some of the HSS tool holders present the tool at a fixed rake angle.
**LINK**
BobH

Southbend bend made a useful tool bit grinding jig block ,which could probably be easily made, square broached holes in the collets would be the most difficult part.But it can be used with a normal swivelling grinder rest.

[Martin KyteParticipant @martinkyte99762]

You are ALL wrong regarding Off Hand Grinding.

It's when you saunter up to the grinding wheel with a fag on and nonchalantly put an edge on the tool whilst only half paying attention. Sort of Sergeant Wilson style.

:0)

Martin

[not done it yetParticipant @notdoneityet]

square broached holes in the collets would be the most difficult part.

Check out u-toob by clickspring, where he demonstrates making square broaches look so easy.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by not done it yet on 24/01/2017 11:14:13:

square broached holes in the collets would be the most difficult part.

Check out u-toob by clickspring, where he demonstrates making square broaches look so easy.

.

… or follow GHT's approach [Universal Pillar Tool] and use  'cut and cover'.

MichaelG.

Edited By Michael Gilligan on 24/01/2017 14:25:18

[John ReeseParticipant @johnreese12848]

When I am grinding a new tool from a blank I usually rough out the shape on a belt sander (1" x 42&quot using a coarse belt. I use a wooden push stick so my fingers don't get burned. That lets me get to near the net shape quickly before I go to the bench grinder.

As others have said exact angles are not necessary. The commonly used angles are a compromise between free cutting and a durable edge. Zero rake for cutting brass is an exception. The only time exact angles are needed is when making a tool for threading.

I recently made up a couple tangential tool holders. The cutter for that is about the simplest to make, just grind the end at about 30 deg. from perpendicular measured along the diagonal of the bit. If you are picky you can check the angle with a threading (fishtail) gauge. Actually just eyeballing it adequate.

The reason I made two tangential holders: I was not paying attention and I made a left hand tool which was hot very useful, so I had to make the right hand tool. Of course, I was not working from drawings.

[thaiguzziParticipant @thaiguzzi]

Posted by mark smith 20 on 24/01/2017 10:48:32:

Posted by Speedy Builder5 on 24/01/2017 09:20:58:

I came across this Southbend link which may be of interest to some of you. Just bear in mind that some of the HSS tool holders present the tool at a fixed rake angle.
**LINK**
BobH

Southbend bend made a useful tool bit grinding jig block ,which could probably be easily made, square broached holes in the collets would be the most difficult part.But it can be used with a normal swivelling grinder rest.

Now that is very neat and very simple. I like it. A bonus is you're not getting hot fingers…

[MalcBParticipant @malcb52554]

Posted by John Reese on 05/08/2016 03:44:16:

Freehand grinding will get you any shape tool you are likely ever need. The typical bench grinder has two faults: the work rest is inadequate and the wheels supplied are ill suited to grinding high speed steel. Those limitations acn be corrected quite easily. A work rest similar to the Veritas will make it much easier to use. Friable aluminum oxide wheels do a much better job on high sped steel than those supplied with the grinder. In the US the friable aluminum oxide wheels for bench grinders is listed tn the catalogs catering to woodworkers.

Agree 100% with this.

I was originally a toolroom turner by trade and all my HSS tool grinding was done freehand. The exceptions being high precision form tools that were done by others on the optical grinders.

The big difference twixt then and now is the quality of bench and pedestal grinders available.

Use of correct stones for both roughing and finishing is essential.

Grinding rests in earleir days were far more substantial and to a degree some were adjustable. The rests on modern day grinders in the main need binning and replacing, in some cases can be downright dangerous because they are like tinplate. More substantial or modified ones are called for.

As mentioned Axminister do the Veritas which would improve things considerably, but they also do a similar made one ( copy? ) that is cheaper and even has a bit more base positional adjustment. I personally would say you will not need anyting more for HSS turning tools unless special forms are required but that a different game.

As also mentioned about stones, I too also had 5 or 6 white fine Arkansas stones, 1:2 and 3/4" square, some with grooves and also a couple of rads.

The media is so powerful now both Youtube and googling can satisfy a tremendous amount of learning. Then there also books, but as others have stated, don't feel blinded by science. Rake and clearance angles are not too critical, so as long as are in the right direction i.e. Positive or negative to match materials where needed.

If however you feel like a multi adjustable rest would give you an ideal project and a good amount of satisfaction then by all means go for it. Personally, I reckon the ones like the HH are total overkill for just lathe tools but…………….

I have said before, its all about enjoyment and not endurance.

[mark smith 20Participant @marksmith20]

Posted by thaiguzzi on 28/01/2017 06:33:16:

Posted by mark smith 20 on 24/01/2017 10:48:32:

Posted by Speedy Builder5 on 24/01/2017 09:20:58:

I came across this Southbend link which may be of interest to some of you. Just bear in mind that some of the HSS tool holders present the tool at a fixed rake angle.
**LINK**
BobH

Southbend bend made a useful tool bit grinding jig block ,which could probably be easily made, square broached holes in the collets would be the most difficult part.But it can be used with a normal swivelling grinder rest.

Now that is very neat and very simple. I like it. A bonus is you're not getting hot fingers…

Heres someones drawing for it.

[Anonymous]

Posted by MalcB on 28/01/2017 08:53:15:

Agree 100% with this.

I was originally a toolroom turner by trade and all my HSS tool grinding was done freehand. The exceptions being high precision form tools that were done by others on the optical grinders.

+1

It's one of the great model engineering myths that HSS tool grinding is difficult, and requires all sorts of complicated jigs and guides.

Over 95% of my HSS tool grinding is done freehand. If I need an accurate angle, or radius, I can either use the T&C grinder or mill the profile before adding reliefs freehand.

Andrew

[Ian S CParticipant @iansc]

Most people can sharpen a pencil, sharpening a lathe tool is no more difficult, some can't get the hang of sharpening drill bits because there you need to get it right.

Ian S C

[John ReeseParticipant @johnreese12848]

Don't get too carried away with grinding exact angles. Most tool angles are compromises between keenness and a durable edge. Too much clearance makes a fragile tool while too little don't cut. Aim for somewhere in between.

Exact angles are only needed on threading tools.

Tools for brass should have zero rake, other angles are not critical.

Always hone after grinding and to touch up a tool that is beginning to dull.

How to Run a Lathe by South Bend is available online free from several sources. It includes grinding tools as well as general lathe techniques.

[Author]

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