finish when turning

[goldstar31]

withequipment and measuring equipment its not difficult apart from failing eyesite and shakes
Merry Xmas

Happily I'm on eyes that my late wife bought as my Christmas and Birthday presents. No cure for deafness and a wheezy pair of bellows, I'm afraid.

At least, I still have enough puff left to wish you and everyone here a very Merry Christmas. May 2017 bring you all lots of workshop enjoyment.

 

[Wizard69]

Hi Norm,



thanks for reply. My concern would be actually sharpening the tool by hand, and losing any specific cutting angle.

Sooner or later you will need to grind and hone a HSS tool. I really see no way around this as even if you use indexable tooling eventually something comes up that needs a special tool.

In other words grinding your own tools is a basic skill in a machine shop. As for loosing a cutting angle how would you do that? If you cant judge the angle buy a protractor or other angle standards.

I realise we are in the machining world, but having to sharpen a new tool, is that common practise,

Yes it is. For one things like drill bits leave the factory with a general purpose grind and it might not be suitable for your intended work. HSS tool blanks of course are seldom ground to a cutting edge at all.

have I naively expected too much.

Maybe! Lets face it every body is new to this at sometime unless they grew up in a machine shop. However we really don't know what is wrong here. Posting a video or a few pictures might help.

As I cut, I take only a very light pass all the time, probably nerves thinking I am going to jam the lathe! I have a very very fine polishing stone, maybe use that?

Most indexable tooling is not sharpenable!

For HSS tooling you need a grinder and a variety of stones to grind and then hone the cutting edge.

Hopper, yes hobby lathe, Ill try some hss bits that I have, thanks!



Paul

By the way even though you need to learn to sharpen HSS tools indexable carbide can be very useful in a small lathe. The trick is to buy the right tooling.

Now all of this being said you need to have your lathe setup properly. If the lathe is new it should be disassembled, cleaned and lubricated. Reassembly should verify that all parts are properly fitted, gibbs adjusted and so forth. A close inspection of the tool post should be made. After all of that the cutting edge of the tool must be on center.

One other thing here proper spindle speed and chip load is a must! Your post has me thinking you might be having an issue here. Different tool geometries require different depth of cuts to work properly. When looking up tool geometries on line id suggest using grinds advised for finish work.

 

[goldstar31]

Wizard69 is pretty much 'on the ball' so perhaps I can leave you to digest the information he gives!

Honing is where most newcomers express difficulty and if you do need experience, I would suggest that a jig might avoid rounding corners- which spoils things.

I would therefore commend you to a simple book like Ian Bradley's Shaping Machine and Lathe Tools book by MAP.

It is as old as tea, some of it is pretty dated and you may have to buy it second hand. Mine is 1976 and falling to bits but it gives a simple jig which ensures 110% results.

Martin Cleeve in his Screwcutting in the Lathe book describes how he approached things. Nothing wrong in that whilst some of the ol(ish) ornamental turning books and articles describe something called a Goniostat or Goneotat which really old turners could hone so well that they could turn ivory and ebony as well as exotic hardwoods. All this dates back to Maudsley and Holapffel days.
You MIGHT get other suggestions but some of the work that these old people performed was truly mind blowing.

Cheers

Norman

 

[joco-nz]

This is quite achievable and seems to be now forgotten and better. It is possible to get that 'barely perceptical swarf' which the old timers like Cleeve published.


Years ago, the late Jim Early and I tried to republish and were threatened with legal action by the then new owners of Model Engineer.

And a Merry Christmas to all our readers:wall:

​

Norm - can you remember the issue(s) the relevant articles were published in Model Engineer? I think I now have access to some of those very early issues through a club. Still under copy right no doubt but I would be interested in reading the articles.

Cheers,
James.

 

[kiwi2]

Hi Paul,
If you want a really good finish on the lathe I would suggest you buy a diamond cutting tool from Eccentric Engineering. Sharpening the HSS tools is easy using the holder which comes with it. There is only one angle to worry about. Using square tool bits gives a good finish but if you use a round one for the finishing cut it will give a mirror finish. It works well for wood as well.
Regards,
Alan C.

 

[goldstar31]

I have a copy- somewhere and I've just come home from Christmas visit to family.

As far as the index goes, it is in Volume 115 and Issue 2882 and called
'Setting a Lathe to one ten thousandth'

Come back - if I can help further

Cleeve was an extremely talented writer. Not always accepted- like me





None of your blokes know another Antarctic Auster 7from 1949? If I can get travel insurance which is extortionate for an old fart of nearing 87, I guess that I'll be in North Island in November.

Regards

Norman

 

[BillWood]

Hi Paul,
It works well for wood as well.
Regards,
Alan C.

Hello,

Could you elaborate on using tangential bits to cut wood please ?
Do you put a rounded corner on them ?
Do you turn the bit around 90 degrees and use it as a shear tool ?

Bill

 

[pmdevlin]

Hi all
many thanks for all the replies. Here is where I am at. Sharpening my own tools, well I was thinking if the cutting angle wasn't perfect I had ruined the tool. I have found some hss tools, and had a go, and was pleasantly surprised that the finish was better. On close inspection (these all came from a deceased friends collection) he had been making specific tooling no doubt for specific jobs. Can these be continually changed by me if I want to, maybe a silly question but do they lose strength?

Back to the indexable set I have, well now I realise they are cheap. A set of 5, £30 from the Northern engineering show would probably mean not that great now I have started looking around?
I intend to go to Doncaster this year, so will pick up some tools there, and some books, cant beat a good read.

What would I like to achieve? well my machining really is basic things for model boats and planes, simple fittings etc that cant be bought, searchlights, handles and the like, its much nicer to make you own, and because of scratched finishes I then spend ages with wet/dry and polishing cloths. I will post a video and some pics.

Machine is a Chester conquest, I am second owner, although when I got it some 6 years ago it had not been used. I have been deliberating what to do with it, over time (and not much use) the backlash and as I call it slop has increased, parting takes two cuts to stop it kicking back, and the cross slide has excessive play that I cant seem to get rid of. Chester at Deeside is half hour away, I have attempted to contact them twice since Christmas, they still have not replied, with the intention of asking do they do any courses, like Axminster do (in Warrington) or offer any sort of service/set up training.

So, its sort machine out, and touch/buy

http://www.thedoncastershow.com/

I'm on a budget, I use 6mm tooling, can I have a shopping list suggestion please, I cut brass and cheap ally, occasionally plastics, machine will be sorted by then!

Many thanks for all replies and suggestions, pics to follow

Paul

 

[kiwi2]

Hi Bill,
The normal diamond tool holder uses a 1/4" square section piece of tool steel. (First photo).
I replaced it with a piece of 1/4" round tool steel ground to the same angle as the square tool using the guide. (Second photo).
The orientation of the tool to the work is shown in the third photo.
An example of the finish quality is shown in the fourth photo. A log of wood was machined across its end grain. What is shown is the finish achieved by the tool - it hasn't been sanded.
Regards,
Alan C.

 

[BillWood]

Hey Kiwi2 thanks for the details on the wood finish.

And now a question please, relevant to the OP's initial question

A concept I've bumped into a few times and never really understood is relationship between tip radius, feed rate and depth of cut for final finish.

I've sometimes seen things like this written in books and internet and my broad understanding is that the intention is to cut a "flat" mirror finish as opposed to a " corrugated threaded " finish.

"Make sure the tip radius is slightly greater ? than the depth of cut and greater ? than the feed rate" (Am guessing that this makes it impossible to cut a "thread")

As a relative newb my best finishes are always obtained by using a shear tool, or by using a knife tool set round to rub, or a tangential with a rounded nose - I have never been able to get a conventional round nose finishing tool to give me as good a finish as these other methods. Am sure that both the OP and myself and maybe others would benefit if somebody could point to a good book or website or maybe say a few words that would help to understand relationship between doc/feed rate/tip radius on a hss round nosed finishing tool. Sometimes I get my knife tool ground just right and can get a wonderful finish when set round to almost rub and like it says in the old Sparey/Westbury/Mason books can do 90% of my cutting with just the one knife tool.

Thanks

Bill

 

[goldstar31]

Whilst I agree with most of your remarks, whatever you do on a lathe cuts a thread- of sorts. The only time that one doesn't is when the lathe is converted to a shaper.

However, however, a shaper tool and lathe tool take on the same configuration. Read ' Ian Bradley' if you doubt me.

As for rounded noses, you are actually lengthening the cutting edge - which theoretically should require more horsepower.

Having 'cantered over the course' myself, you should also read Martin Cleeve on the subject where he removes then thousands of an inch. Unquestionably, I do not have all the answers but the question of chip breaking tools comes in. Your excellent referees never got there as I doubt few had the tooling to do it. Further, this mental difficulty of separating wood from metal seems to persist.

For an earlier generation, the same tools were used to cut wood and metal. If you read Holzapffel- and many more, they cut not only wood, metal and stone to machine bone and ivory.

For my part, I used to cut lignum vitae with metal cutting lathe tools. The turnings were virtually brown grease and went to polish the result.

I hope my comments add to your interesting and well thought out discussion

Norm