Poor finish with my finishing tool.

[simonl]

Hi all,

I have been looking to make a couple of cylindrical squares. It has been on my "to do" list for a while. I recently replaced the headstock bearings with good quality ones and also re-aligned the head to my satisfaction. It now turns parallel to within 0.0001" (sorry about mixing metric and imperial, 0.0001" micrometer is my most accurate one I have!) over a length of 100mm which I am very happy with. The one thing that still escapes me is the correct grinding of a finishing tool in HSS. I have had a go and the finish is not what I would call high class. I have tried several speeds and for simplicity have kept the feed rate the lowest possible but still I get score marks and lines. The steel is just a piece of mild bright steel held in a 3 jaw.. It's about 38mm diameter and I have been using speeds of approx 400, 600 and 800rpm with little effect on finish I have the tool dead on centre height. I therefore tend to think that my tool grinding skills are not up to it. I have achieved a beautiful finish with my indexable tools (with heavier cuts and still maintain parallel accuracy) but I want to master the art of making my own finishing tool in HSS.

Below are some pics of the workpiece finish and the tool I have used. Any feedback would be much appreciated. Oh and I'm not using any coolant either.

Cheers,

Simon

[Stustoys]

Hi Simon,
From the look of your pictures you have no(or not much) Back Rake and your Side Rake appears to be reversed.


Stuart
p.s. My theory on those marks is where the tool stops cutting and just rubs for a turn or so before it starts cutting again. Have you tried increasing the feed?

p.p.s My chart says you should be doing about 240rpm

Tool bit - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Tool_bit)

[Dave J]

I Simon,
You don't have enough rake from right to left across the tool and it actually looks like it is opposite to whats needed.
I don't grind any back rake in my tools as I find it's not needed.
Here is a good chart on grinding, what you need to copy is the right handed tool
http://dale.chatham.org/Interests/MetalWorking/HowToGrindLatheTools.pdf
Once you have it to shape it is easy to touch up.

Dave

[pipeclay]

Try slowing it down,try a cutting oil,put a little more nose radius and definately increase your top rake,one of those pictures depending on camera angle appears to be negative rake and not positive.
Keep the feed rate low.
If you continue to cut it dry it could be a slow progress to what you desire.

[simonl]

Hi Simon,
From the look of your pictures you have no(or not much) Back Rake and your Side Rake appears to be reversed.


Stuart
p.s. My theory on those marks is where the tool stops cutting and just rubs for a turn or so before it starts cutting again. Have you tried increasing the feed?

p.p.s My chart says you should be doing about 240rpm

Tool bit - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Tool_bit)

Hi Stuart,

Several people have said I have incorrect rake angle. So it's not supposed to slope down towards the cutting edge but up similar the the front rake angle (if there is one)? :doh:

If that is the case then yes my rake angle is incorrect! I also think you are correct in that when I was cutting it did seem interrupted and would stop cutting for small periods of time. It must be rubbing instead of cutting like you said.

Cheers mate!

Simon

[Steamwhisperer]

Hi Simon
If you grind up a shear tool you can get a mirror finish with HSS

Phil

[simonl]

Try slowing it down,try a cutting oil,put a little more nose radius and definately increase your top rake,one of those pictures depending on camera angle appears to be negative rake and not positive.
Keep the feed rate low.
If you continue to cut it dry it could be a slow progress to what you desire.

Hi pipeclay,

Yes I think you and stuart hit the nail on the head with the side rake. I didn't know it was supposed to slope UP towards the cutting edge across the tool as well as front to back.

I have been following a project that makes a set of cylindrical parrallels in Workshop series by Harold Hall called "Lathe work a complete course" he does not use any coolant and his photos show a very good finish. Then again he also states that your cylinder should be no more than 0.0002mm out of parrallel over 100mm. I have managed 0.1 thou (0.00025mm) which I think is probably as good as I or my lathe will get! I think.

Cheers,

Simon

[RayG]

Hi pipeclay,

Then again he also states that your cylinder should be no more than 0.0002mm out of parrallel over 100mm. I have managed 0.1 thou (0.00025mm) which I think is probably as good as I or my lathe will get! I think.



Wow!... are you sure about those numbers... i'd be pretty happy with 0.01mm parallel

0.0002mm that's 0.2 microns!

Regards
Ray

[Dave J]

I made a set up a while back and could not feel any difference with the mic from one end to the other. These where machined with HSS.

http://www.woodworkforums.com/attachment.php?attachmentid=191926&stc=1&d=1324452031

Dave

[Michael G]

Simon, you need to watch those modelling books from the UK as they usually use free cutting material for their steel turning work. The normal bright mild steel we commonly buy does not finish as easily, so you are already putting yourself at a disadvantage if you do a direct comparison.

Michael

[.RC.]

You could try with cast iron... Like mine...

[lather]

Dave, are those made from mild steel.

[simonl]

Wow!... are you sure about those numbers... i'd be pretty happy with 0.01mm parallel

0.0002mm that's 0.2 microns!
Regards
Ray

Hi Ray,

yes you have picked me up on that one! Stupid zero's.... :B

I was one order of magnitude out. I meant to say 0.002mm as in 2 microns. Personally I don't have the capacity to measure numbers this low as I only have a 0.01mm and a 0.0001" micrometer. So, if I want the best accuracy I have to use my imperial one at this stage. Even if I did have a true micrometer as in one that measures microns, surely it would still have an uncertainty of +/- 0.001mm.

Still, I'm happy with the accuracy of my machine in terms of turning parallel.

Cheers,

Simon

[simonl]

I made a set up a while back and could not feel any difference with the mic from one end to the other. These where machined with HSS.

http://www.woodworkforums.com/attachment.php?attachmentid=191926&stc=1&d=1324452031

Dave

Nice finish Dave you show pony! :U

Are they made from hollow tube?

Cheers,

Simon

[simonl]

Hi Simon
If you grind up a shear tool you can get a mirror finish with HSS

Phil

Man I can't even get a finishing tool right at this stage and now your telling me to make a what? A shear tool? :doh:

What does that look like? throw me a bone!

[lather]

simon, i've been at it for over a year now, tried numerous tip variations, speeds, and still cant get a finish any where near the look that dave posted, the only time they have come close is when sanding and buffing.

[toolman49]

G'Day,
I can only agree withe previous comments, from the photos the tool looks like a left hander, designed to cut away from the headstock.
And for what it's worth, I as a pimply youth (many, many moons ago) I was taught to support the work with a centre any time the length of cut exceeded 3 times the diameter.
Regards,
Martin

[Dave J]

Lather and Simon,
Just standard mild steel black tube I had laying around. To get that sort of finish you need to hone the tool well with a oil stone. I never used any emery cloth on those as it would put out it's accuracy. You can also see you oil covering them to save them from rust. I oil them up and keep them in a plastic bag or they will rust in my shed.

Simon, if you follow that link to the right handed tool I posted you should get good results from it. It is good to see your trying to use HSS, as it's a cheap way of machining and once you get used to grinding them you will wonder what all the fuss was.

If you print those pages out and take them down the shed, you can then just copy the shapes off them while your grinding.

Dave

[lather]

Will make a tool out of 1/2 "HSS, and give it a try, have been using the diamond holder, which now seems to have troubles holding it's center height when performing deep cuts, even though the tool is tight.

[Dave J]

I have never used a diamond tool holder because the HSS sticks seem to work good enough for me. I can machine off 3mm (6mm on diameter) no problems, but I find mild steel likes the a bit of side rake to leave a nice finish compared to other steels. When I was cutting those cylinder squares the shavings where like hair thin or thinner on the final passes.

Dave

[pipeclay]

Would that be a head hair or pubic hair.

[pipeclay]

G'Day,
I can only agree withe previous comments, from the photos the tool looks like a left hander, designed to cut away from the headstock.
And for what it's worth, I as a pimply youth (many, many moons ago) I was taught to support the work with a centre any time the length of cut exceeded 3 times the diameter.
Regards,
Martin

That would be depending on the diameter wouldnt it?

[Dave J]

LOL, not sure I have never measured a pubic hair, is there a difference?

Dave

[pipeclay]

Theres a couple of thou in it.

[Stustoys]

Hi Simon,
Toolman brings up a good point. We've all assumed you are cutting towards the chuck and not away from it?

I tried vertical shear bits but didnt have much luck on very fine DOC. Strange as they work great on the shaper. Maybe you'll do better
Vertical Shear Bit (http://www.gadgetbuilder.com/VerticalShearBit.html)

38*3=114mm

Stuart

[simonl]

G'Day,
I can only agree withe previous comments, from the photos the tool looks like a left hander, designed to cut away from the headstock.
And for what it's worth, I as a pimply youth (many, many moons ago) I was taught to support the work with a centre any time the length of cut exceeded 3 times the diameter.
Regards,
Martin

Hi Martin,

The workpiece started off as 50mm and it was only extending out by about 150 so I'm not being too naughty. Also I thought that by doing very light cuts you can get away with a little more. There can't be too much flex if you look at how close the diameters are at each end....

Besides, my tailstock is nowhere near aligned accurately enough (height wise) to be used without compromising the intended accuracy.

G'day Dave,

Thanks for the links I will have a look and most likely print off and laminate and take back to the man cave.

Lather,

No offence but I take some comfort in knowing I'm not the only one struggling with this. I guess it's not an apprenticeship for nothing.

Michael,

You mean they are using free machining steel? The bastards! I'm doing my head in on this! Oh well, the process has allowed me to pick up on some things I am doing wrong in terms of tool grinding. For me, I feel if I can achieve a mirror finish with HSS on mild steel then I can achieve anything! It's like Mr. miyagi in the Karate Kid catching flies with chopsticks! :D

Cheers,

Simon

[Dave J]

LOL, it's no as hard as catching flies with chop sticks.

Dave

[Steamwhisperer]

I tried vertical shear bits but didnt have much luck on very fine DOC. Strange as they work great on the shaper. Maybe you'll do better
Vertical Shear Bit (http://www.gadgetbuilder.com/VerticalShearBit.html)


hi Stuart
Thanks for throwing that bone for me

Phil

[krisfarm]

Hi Simonl,
I had a similar problem achieving a good finish on that horrible black bar. It is much easier on the leaded steels.You can still get a good finish on the black bar by doing the following.
1.Supporting the work in a centre irrespective of the amount sticking out from the chuck.
2. You must have a razor sharp tool, the shape of the tool is not that critical as with a finishing depth of cut of .002"-.003" you only have the radius nose doing the cutting.
3. Turn at very low speed 50 rpm and the lowest feed you can.
4 Use coolant.
I have tried a large number of different tool styles,shear tools, diamond tools, double angled tools and all are capable of a good finish if you do the above steps. Not all that Black bar is the same quality.
Bob

[simonl]

Thanks Bob & Phil.

There have been lots of replies on this thread for me. Lot of things for me to try differently to what I am doing now.

Thanks

Simon

[lather]

Thanks for the info Dave, Bob,
the best finish i had was on the slowest speed, and a slow feed, took forever on a 300mm shaft, thought i was doing something wrong due to seeing videos in which the lathes ran much faster.
noticed that extra material was being removed, when reducing rpm, even after 3 passes on the higher rpm.
for accurate jobs, ran it between centers for the finishing passes.
although it was smooth, it never had a chrome like finish as Dave's photo, unless it's an illusion caused by the oil.

Simon l,
no offense taken, will post tomorrow about using the 1/2' HSS tool, perhaps it will make a difference compared to the tangential holder.

[simonl]

Good luck lather. I will re-grind my tool today and see if I can get a better finish. I might run out of time though as my son finishes school at 1:30 today :((

Saturday leaving for a 5 day camping trip. Lathe won't fit in the car:roll:

Simon

[Kody]

Have a Bo-peep here. I wrote a lot of info about this very same thing not all that long ago.
http://www.woodworkforums.com/search.php?searchid=7430941

Read all the posts and replies that I wrote and you will find all the info that you need. Rather than me re-posting the info, it will be faster if you simply look around these earlier postings. There is heaps of info. Search under the name of "Kody".

Kody

[19brendan81]

Lather and Simon,

I will put up pics tonight on this thread of a tool my uncle came round and fixed for me yesterday. I had attempted it using all the info I could get from the web and he took one look at it and said it wouldnt cut steel. He ground on WAAAAAY more back and side rake than I had been using, and now it cuts like a dream.

Lather your definately not the only one struggling with HSS...I think its one part of this sport which you really need to be shown in person. If you cant get something to work i'll send you this tool so you can try to copy it. he reccomended using half inch square HSS for tools. It takes longer to grind up, but its stronger, can hang out of the toolpost further and is easier to grind as you can see more and measure angles easier.

Re the shear tool - i had a quick play with it but had no luck. The edge would burn out pretty well instantly. Will try it again another time with less cutting depth (achievable now I have a DRO) and flood coolant.

[pipeclay]

To try and eliminate a lot of the brain strain,read the books as they are a theoretical guide,and then bring your own judgements into play.If you were to try and emulate what the books are telling you,you will be chaseing your ar s.

[Bryan]

Have a Bo-peep here. I wrote a lot of info about this very same thing not all that long ago.
http://www.woodworkforums.com/search.php?searchid=7430941

Kody

Kody, on my browser your search link returns


Sorry - no matches. Please try some different terms.

[19brendan81]

OK,

Here are a few pics of the cutting tool I referred to above, and some photos of it in action.

The first few are of the tool from several angles. The once called "right side" which strangely enough is a photo of the right side of the tool shows how much side and back rake is on the tool. If your clever with maths you could probably figure out the side rake angle knowing the dimensions of the tool (1/2 inc square) and estimating how much has been ground away at the back (looks like nearly half to me)

The others are of the tool in action. I havent done any honing on this tool...its straight off the grinder. The photo called "redbar" is a close up of the finish I got when I first used the tool on some mild steel I have (that is painted red). This was a feed of .056 per revolution and a cut of .1mm. The black spots and smears are grease from my fingers, the finish on the right of the bar is more indicative of what it was all like til i put my grubby mits on it.

The other shots are of me cutting a piece of black bar that I have had for years which is hands down the worst material I have ever had to cut, so the finish isnt as good as I got with the redbar, still...with a bit of honing and playing around I can probably get it to improve.

The one called 'roughing' is a 1mm DOC for 2mm off the diameter. The tool slices this off, and I am sure it could easily take a cut two or three times this deep.
The one called 'finish' was when I used a feed of .056 and a cut of about .10mm
The one called 'fine feed' shows the finish after a feed of .087 and a cut of .25mm, this is the best finish I got however there are still a couple of lines here and there...i'll keep working on it.

Whilst I have sung the praises of Carbide in other threads, I should point out that im a huge fan of HSS. In addition to its cost and versatility it has some massive benefits over carbide that really make it worthwhile. Namely, the swarf comes off cool so you dont need to worry about burns when you are wearing safety thongs. Also, the slicing action doesnt deflect stock as much as using carbide does, so its great on slender pieces. Thirdly you can take much smaller cuts with it whilst maintaining a good finish... which really helps when creeping up on a diameter.

[Dave J]

I do away with the back rake, this way as the tool gets sharpened the height doesn't change. I also cut those cylinder squares dry, like most all of my turning.

Dave

[19brendan81]

Can you stick up a photo of such a tool Dave?

historically I havent used coolant much, except for boring, and if I do its out of a spray bottle. Now my new lathe has a pump and nozzle i'll probably start using it a bit more.

[pipeclay]

Is that coolant at the right mix,it looks a bit weak?

[morrisman]

Your 1/2" tool geometry looks OK to me , but you need more of a radius on the tip . 2mm radius is ideal . When setting up for cutting , rotate the top slide around until the radius of the tip on the tool is just kissing the workpiece . In other words, dont have the tool shank at 90 degrees to the work , but move it around so the tip radius is on the work piece . . Use a slow feed and experiment with spindle speeds . make sure the tool is at centre height MIKE

[Dave J]

I am going down the shed soon so I will grab a photo. I never really looked at it, but the coolant does look a bit watery to me as well, now that Pipeclay mentions it.

Dave

[pipeclay]

Your 1/2" tool geometry looks OK to me , but you need more of a radius on the tip . 2mm radius is ideal . When setting up for cutting , rotate the top slide around until the radius of the tip on the tool is just kissing the workpiece . In other words, dont have the tool shank at 90 degrees to the work , but move it around so the tip radius is on the work piece . . Use a slow feed and experiment with spindle speeds . make sure the tool is at centre height MIKE

Can you explain what you mean,from my understanding a radious is the same were ever it touches the OD.

[morrisman]

this crap drawing may help you MIKE

[Bryan]

I think he means side clearance (that's what I call it - could be wrong). See pic. Reducing this angle can certainly improve finish.

[morrisman]

Can you explain what you mean,from my understanding a radious is the same were ever it touches the OD.

Yes that is true PC .. OK I didnt explain it well . If the radius is large and mostly ground onto the front edge , rather than the side , then rotating the tip around will present the radiused edge facing the work piece . Harold Hall suggests this method . MIKE

[Dave J]

Can you stick up a photo of such a tool Dave?

historically I havent used coolant much, except for boring, and if I do its out of a spray bottle. Now my new lathe has a pump and nozzle i'll probably start using it a bit more.

Here you go Brendan, this works good on mild steel for me.
http://www.woodworkforums.com/attachment.php?attachmentid=192084&stc=1&d=1324540221

Here it is taking 2mm deep cut
http://www.woodworkforums.com/attachment.php?attachmentid=192085&stc=1&d=1324540221

And this one a 0.05mm cut
http://www.woodworkforums.com/attachment.php?attachmentid=192086&stc=1&d=1324540221

The tool could do with a hone as I have used it a bit.

Dave

[Dave J]

I forgot to add that I grind the 3 faces, then hone them with a oil stone and put the nose radius on with the oil stone not the grinder. A few rubs around the nose give you what you need.

Dave

[morrisman]

Dave , That looks like a knife tool ... we are all going to try that from now on :2tsup:

[Dave J]

Knife tool, not sure I have heard of that one. I just played with different grinds and this one seems to work the best on mild steel.
Although I don't recommend it, you will see I have miles of over hang on this bit of scrap, but the tool seem to slice the steel off and not want to grab into the work. I only had it that far out because I didn't want to chuck up the rusted area.
Those cuts where done at 200 rpm and the bar is about 35mm round (would have to check).

Dave

Edit,
I don't own any of these books you guys talk about, is there reference to a tool like this?

[morrisman]

I don't own any of these books you guys talk about, is there reference to a tool like this?

Yes there certainly is ..in HH's books, he uses knife tools quite a lot . MIKE

[RayG]

Hi Mike,

I don't know what Harold Hall calls a Knife Tool? But... "That's not a knife!" ... (apologies to Mick Dundee)

http://www.neme-s.org/shapers/columns/shaper_column_41_files/bits02.gif

Style AR – Right Hand for turning to square shoulder. Used for general machining operations such as turning, boring, and chamfering.
Style AL – Left Hand for turning to square shoulder. Used for general machining operations such as turning, boring, and chamfering.
Style BR – Right Hand 15º Lead Angle for turning when no square shoulder is needed. Used for general machining operations such as turning, boring, and chamfering.
Style BL – Left Hand 15º Lead Angle for facing when no square shoulder is needed. Used for general machining operations such as turning, boring, and chamfering.
Style C – Square Nose for chamfering. A perfect general purpose tool of great utility for chamfering, facing, and turning. Tool can also be used to make special form tools.
Style D – Pointed Nose - 80º Included Angle used for undercutting and O.D. and I.D. chamfering.
Style E – Threading Tool. Standard 60º included angle for universal threading, V-Grooving, chamfering, turning, boring, and facing.
Style ER – 60º Offset Threading Tool. Tip is offset from the shank. For threading and V-Grooving to a shoulder.
Style EL – 60º Offset Threading Tool. Tip is offset from the shank. For threading and V-Grooving to a shoulder.


This is a knife...
http://www.neme-s.org/shapers/columns/shaper_column_41_files/bits04a.gif


Hope that helps...



Regards
Ray

[Dave J]

Thanks Ray, maybe in Mikes book it has a tool similar to mine that he has named a knife tool. That one you posted looks like what they call a shear tool.
This shape is my standard work horse as most of what I do is in mild steel. I usually sharpen that other end as a left hand so it's only a matter of turning the tool around.

If anyones having trouble grinding this tool I could do a step by step process to help out.

Dave

[morrisman]

This is a scan from HH's book .he calls it a knife tool . Almost identical to DAVES. BTW HH doesn't use any back rake for his turning tools . As it says the rake is sideways , across , but not back MIKE

[Dave J]

Hi Mike,
I don't put a flat on the end of mine, I just put a small radius with the oil stone.But other than that it's similar.

Dave

Edit
I notice he calls his a finishing tool, mine is used for both roughing and finishing and works well both ways.

[simonl]

This is a scan from HH's book .he calls it a knife tool . Almost identical to DAVES. BTW HH doesn't use any back rake for his turning tools . As it says the rake is sideways , across , but not back MIKE

That's one of the books I have. That tool is described as a finishing tool, in this case used to make the final finish on the cylindrical squares I'm going to do..... once I get this finishing tool down pat. I think with all the info here I should be right. In theory!

I do have to take into account the Simon retard factor though! :doh:

Simon

[Dave J]

The tool I posted above is the same type I used to finish my cylinder squares. You need to pay attention to the honing to get a great finish, like I said earlier you are only shaving off hair like material on the final pass. For roughing you can use it strait off the grinder and it will a reasonably good finish, but always give it a bit of a hone.

Dave

[RayG]

Hi Simon
If you grind up a shear tool you can get a mirror finish with HSS

Phil

Hi Phil,

Nice one, I had a bit of a play with a shear tool, and works like a dream, weird shavings, beautiful finish :2tsup:

Regards
Ray

PS. Thanks Stuart for the bone.. I mean link... http://www.gadgetbuilder.com/VerticalShearBit.html

[Stustoys]

PS. Thanks Stuart for the bone..

Looks like I might have to give it another try. In the vertical shear bits defence I did just try the one off the shaper, the angles might have been less than perfect and I know it was touchy on the shaper to set up.

Stuart

[lather]

Wow, this thread has grown, performed a few tests today, but did not grind down the 1/2 inch bar, as these are worth a bit, have plenty of 5/16 HSS with no holder.

tested using my home made circular saw carbide tool, and the diamond tangential holder.
ignore the rough sections, kept it as is for an easier reference of the finishing cuts.
fig a/b show the finish.
section 1 is the carbide tool at 170 rpm and the feed about 20 percent off the slowest feed.
section 2 is hss run towards the tailstock, 70 rpm and the slowest feed
section 3 is hss run towards the chuck. 70 rpm and the slowest feed
section 4 is the carbide tool at 70 rpm and the slowest feed.
the depth of cut on all were 0.05mm.
noticed when cutting 0.05mm deep the cuts were not constant, was o.k at 0.1mm deep.

At 300 rpm and a feed rate 20% from the slowest setting, the carbide tool gives a better finish than the hss on the slowest speeds.

honed the hss with a new diamond sharpening stone with a shallow radius, and honed a round edge on the carbide tip.
fig-c/d show the carbide tool, and circular saw the tips came from.
The tool looks like crap, but works great, even works on broken rough cuts.

Dave, could you possibly post the angles of the tool, the finish looks great, what was the feed rate?
will definitely be grinding the 1/2 inch now.

Brendon, will try to copy Dave's tool first, if no success will take up the offer.

[Dave J]

Hi,
I only go by eye when I grind them so I had to measure them. Looking from the top it has a 15 deg angle, then a 80 deg tip. The side clearance is 9 deg and the front clearance is 20 deg (though some of mine have a bit more so not critical) and side rake of 18 deg with a feed of 0.001mm or 0.026 inch for finishing at 200 rpm on that 35mm bar.
I usually use 5/16 tool bits as it saves grinding.

Dave

[lather]

Thanks dave, is the 5/16 on its own strong enough for deep cuts.

[Dave J]

That one I posted up was only 1/4 tool and taking 2mm deep cuts and I would have no problem pushing it deeper. This tool sort of shears it off, not putting a lot of strain on the tool. So the 5/16 tool is plenty.

Dave

[Dave J]

I forgot to mention that I use a left handed version of this tool for facing and it works great as well.

Dave

[lather]

dave, just read your response about not using back rake, which also allows the tool to be continually sharpened with out loosing height.
the back rake angle is the main reason i never bothered to use hss without the angled holder.
have a curio about the side cutting edge, due to not using back rake, does that edge point slightly downwards towards the tip when grinding the side cutting edge angle, due to the tool tip now being in a lower section of the side rake slope,
or when grinding, should the side cutting edge angle be ground before the side rake.

[simonl]

I have a draw full of HSS tools that I inherited from the old man. They are mostly 1/2 inch. I have some others that are about 16mm as well. These are what I use and have become used to using. I would not be used to using anything smaller. In fact I find it easier to grind larger tool bits even though there is more material to grind away, they are easier to hold.

Simon

[19brendan81]

Cheers for posting that Dave. I'll make one and see how it goes.

Re the coolant question from a couple of pages back - thats actually mixed stronger than reccomended. The bottle says to mix 5% coolant with 95% water and its mixed closer to 10% and 90%

Re the radius - I often screw up this bit, and my hone isnt appropriate for lathe bits (its one of those diamond ones full of holes - unsuitable for anything under 25mm wide)...so i'll probably play more with a radius when I get a decent oil stone.

Brendan

[pipeclay]

When you rub your fingers under the coolant stream are they slippery or do they feel slightly dry.
Not knowing the brand or type of coolant you are using does make it hard to comment,but normally Solubile Oil when mixed looks a lot like milk.

[19brendan81]

This stuff is green, and tends to stay that way when in use. It went milky when it picked up oil that was in the swarf tray from when I overfilled my spindle.

I'll stick up the details in a couple of weeks...going on hols now.

[Dave J]

dave, just read your response about not using back rake, which also allows the tool to be continually sharpened with out loosing height.
the back rake angle is the main reason i never bothered to use hss without the angled holder.
have a curio about the side cutting edge, due to not using back rake, does that edge point slightly downwards towards the tip when grinding the side cutting edge angle, due to the tool tip now being in a lower section of the side rake slope,
or when grinding, should the side cutting edge angle be ground before the side rake.

Hi,
I grind the side clearance, then the tip angle/front clearance and then the side rake last. When I grind the side rake I have the wheel square to the front edge.

Dave

[lather]

Dave, thanks for the tips, this has definitely been the best help of all the info that i read on the net.
Just tested on a 40mm bar, without honing or a radius.
it worked great.
the cuts were smooth and didn't get the scratchy surface probably due to the tool trying to dig in.
even a light cut at 300 rpm had a much better finish compared to the the diamond tool holders finish run at the slowest speed.
will sharpen another tool, to use one for finishing and the other for deep cuts.
I understand now that the manuals are to be used as a rough guide, "A very rough guide" considering there is no back rake on this tool.
Rough to me is a few degrees here or there.

Cheers,
Merry Christmas to all.

will have more fun today,my poor mans dro arrived, the next tool project will be a universal tool platform for sharpening the HSS on the grinder.
my home made drill sharpener works great, it,s roughly based on the Tormek_DBS-22_Drill_Bit_Sharpening_Attachment.

[morrisman]

these are sold pre ground LATHE CUTTING TOOL SET 8pc PRO GROUND 5/16" Sq HSS | eBay (http://www.ebay.com/itm/LATHE-CUTTING-TOOL-SET-8pc-PRO-GROUND-5-16-Sq-HSS-/110736601929?pt=LH_DefaultDomain_15&hash=item19c86a7349)

[simonl]

Thanks to all who contributed to the thread. Glad to see many people have benefited from everyones ideas as I have. I look forward to applying the new information I have gained from you guys in the new year. Can't wait to spend some quality time grinding up a kick ar..se finishing tool.

I'm going camping for 5 days from tomorrow so I will catch up with you all in the new year.

Have a safe Christmas to all.

Cheers,

[Dave J]

Dave, thanks for the tips, this has definitely been the best help of all the info that i read on the net.
Just tested on a 40mm bar, without honing or a radius.
it worked great.
the cuts were smooth and didn't get the scratchy surface probably due to the tool trying to dig in.
even a light cut at 300 rpm had a much better finish compared to the the diamond tool holders finish run at the slowest speed.
will sharpen another tool, to use one for finishing and the other for deep cuts.
I understand now that the manuals are to be used as a rough guide, "A very rough guide" considering there is no back rake on this tool.
Rough to me is a few degrees here or there.

Cheers,
Merry Christmas to all.

will have more fun today,my poor mans dro arrived, the next tool project will be a universal tool platform for sharpening the HSS on the grinder.
my home made drill sharpener works great, it,s roughly based on the Tormek_DBS-22_Drill_Bit_Sharpening_Attachment.

No problem and thanks, great to hear your getting good results and is working good for you.:2tsup: Sometimes what works for one person doesn't always work for another. I have been using this type of tool for around 20 years and it worked good for taking big cuts on the Hercus as well, with out straining it too much.
I up the speed for finishing cuts but just did that test at 200rpm as the lathe was set on that. The only thing you have to watch using it dry at higher speeds is the tool getting hot and the edge going off before finishing the cut, but coolant even sprayed on by hand will help that.
Now your using this tool you can now see how I got the finish on those cylinder squares.

That DRO will make life easy, don't forget to post up about the install etc. With this tool you will now be able to do finer cuts than the DRO can read.

Dave

[Dave J]

Thanks to all who contributed to the thread. Glad to see many people have benefited from everyones ideas as I have. I look forward to applying the new information I have gained from you guys in the new year. Can't wait to spend some quality time grinding up a kick ar..se finishing tool.

I'm going camping for 5 days from tomorrow so I will catch up with you all in the new year.

Have a safe Christmas to all.

Cheers,

I hope you have a great time and will catch up with you in the new year.:2tsup:

Dave

[lather]

here are some pics of the tool, notice that there is no back rake as Dave's tool.

a little tricky trying to cut the side rake without loosing height off the cutting tool.

[.RC.]

I get totally confused bythe terms back rake, side rake, upside down rake etc...

I prefer to use the terms... Cutting edge angle, front clearance angle, side clearance angle, angle on inclination..

Clearance angles are just that, for clearance... Cutting edge angle varies for the material.... MS is around 7-10 degrees.... Angle of inclination is the angle the tool angles back when you look along the cutting edge....The very common square HSS holders have this set at around 15 degrees..

[Dave J]

Lather,
The tool looks good :2tsup: and it looks like you have a have a good eye and steady hand when grinding.

RC,
Just following on the names that are common to every one and have been for many years. If we stick to this, then when people go looking for more info on it, it's all the same terminology.

Dave

[.RC.]

Dave just going by my tafe book I wonder if the terms side rake and top rake etc are US terms as the tafe book only mentions normal rake which the wedge cutting angle. Normal rake angles are

0 for brass
8-10 for cast iron
10-15 for mild steel
20-25 for copper and aluminium.

Clearanc eangles to be 3-8 degrees... more for aluminium..

Then you have the approach angle andnose radius.

Carbide inserts are different in that they have positive and negative inserts. From what i understand allnthis means is negative inserts have 0 clearance built into the insert and theholder holds them down at a angle. While positive inserts have the clearance angle built in... negative inserts can be double sided and have stronger edges but require more hp for a given cut and are not as good at getting a good surface finish.

[lather]

dave, wish i had that steady a hand, used a platform on the grinder which can be tilted which saves a lot of hassle.
for the last edge or side rake, set the platform to the correct angle, then placed another platform on top and angled it until the cutting edge was horizontal to the grinder.

[Bryan]

I would love to see a consensus on names for tool angles. Every source I see seems different. And every discussion I've seen just gets confusing and resorts to pictures.

[Dave J]

I just checked and it sounds like we have the same book with the normal rake and those numbers, is it a 3 volume set? I was just referencing mine to the South Bend link I gave to save confusion and is what I call it as well.
Just looking in that book I see they call back rake inclination and the side rake normal rake.

Dave

[lather]

Bryan, your right about that, found this on wiki, when trying to figure out the angles to grind when trying to replicate the angles Dave posted.

File:Tool Bit Geometry.JPG - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/File:Tool_Bit_Geometry.JPG)
makes sense to me.

[Dave J]

I would love to see a consensus on names for tool angles. Every source I see seems different. And every discussion I've seen just gets confusing and resorts to pictures.

I think it is easier to think of it as back rake and side rake, as that describes exactly what it is in simple terms.

Dave

[Dave J]

Give it time and practice you will be able to do it free hand, though jigs do get you spot on the first time. Doesn't really matter which way you do it as long as you get good results in the end.

Dave


dave, wish i had that steady a hand, used a platform on the grinder which can be tilted which saves a lot of hassle.
for the last edge or side rake, set the platform to the correct angle, then placed another platform on top and angled it until the cutting edge was horizontal to the grinder.

[jhovel]

..."as that describes exactly what it is in simple terms."

only if you are used to those simple terms.
To me 'rake' implies at best the angle of the teeth on a garder implement. I'm used to the terms cutting angle or clearance angle. "back rake angle" is only barely meaningful to me. I would consider that more relevant to the angle of the tool holder than the tool edge though.....

A consistent set of tems would be very helpful.

Joe

[Steamwhisperer]

There might be some confusion in that with cutting tools there is only negative rake and positive rake. Rake is an inclination not an angle. Everything else is cutting and clearance angles.

Phil

[Dave J]

..."as that describes exactly what it is in simple terms."

only if you are used to those simple terms.
To me 'rake' implies at best the angle of the teeth on a garder implement. I'm used to the terms cutting angle or clearance angle. "back rake angle" is only barely meaningful to me. I would consider that more relevant to the angle of the tool holder than the tool edge though.....

A consistent set of tems would be very helpful.

Joe

Hi Joe,
If you follow that link I posted on page one it shows what I call standard terms, and I find most people on the forums also use these terms to describe a tool.

Dave