mini lathe tools

As you may know i have just purchased my Cowells 90 lathe, i was thinking of grinding some 5mm hss bar stock i got free, but im new to this and was thinking of buying some ready made tools the carbide inserts not the cemented type as i beleive these are not good, then later on having a go at grinding my own, just after some opinions .

regards john

I think one of the best books about manual lathe use is still the book first published by South Bend `How to run a Lathe`. The boxford version is in the link below. . From page 19 there is a chapter on grinding lathe tools. Some may disagree of tool profiles etc... but most do work well for grinding your own carbon (not much used nowadays)and HSS tool steel blanks.

I use a Southbend and a small Pultra (about the size of the cowell) and still nearly always use exclusively HSS toolbits that ive ground myself from square or round blanks,along the lines of whats in the book.

**LINK**

Edited By mark smith 20 on 08/09/2017 16:49:18

Southbend version here

http://campkahler.com/files/How_to_Run_a_Lathe_SB_1of2.pdf

Edited By mark smith 20 on 08/09/2017 16:53:00

I would read the advice on tooling given in your other thread.

That's what I did. As a rank beginner I found grinding HSS from scratch too difficult. Carbide inserts are initially expensive, but you don't have to sharpen them. That eliminates a possible source of learner error. It's easier to blunt HSS by overheating it than carbide and a beginner may not realise when HSS needs resharpening. Also, if you happen to break an insert, you can replace it without having to reset the tool height, that can save lots of time.

For me the cemented carbide type are neither fish nor fowl. Their advantage is cheapness compared with inserts and the ability to work hotter and faster than HSS. Apart from that, they have the disadvantages of both HSS (has to be reground) and Carbide (may crack). In practice I switch happily between HSS and indexed tips and never use the cemented set I own.

Many people swear by HSS, others prefer carbide. I mostly use carbide inserts, but there are plenty of times when I think HSS is 'better'. A great deal depends on what you're using the lathe for and what sort of lathe it is. Carbide doesn't give it's best on a slow lathe doing small diameter work. Your Cowell's is quite quick, so I think you'll be happy with inserts. HSS will be useful when you want to take very fine cuts with a sharp tool, and it sometimes produces a better finish.

After you've used the lathe on your metals of interest you will soon develop a much better feel for what suits you. I don't think you will regret starting with carbide inserts; they'll occasionally be useful even if you end up a committed HSS fan. Don't be too intimidated by theoretical complexities: the best way to find out is to get on with it and use the lathe. Use known metal rather than scrap. A lot of scrap (and some DIY store metal) is truly horrible - don't blame the lathe or yourself if odd lumps of metal behave badly! Getting the very best from a lathe will take time to learn, but they are quite forgiving while you learn the ropes.

Dave

I would recommend beginners to start with a set of pre-ground HSS tools.

These are quite forgiving, relatively inexpensive, can be resharpened if you get it wrong, and will act as a guide when you come to grind your own.

The basic knife tool is one you can grind yourself that is good for 90% of conventional turning and suits small lathes.

Carbide takes some experimenting and experience to give good results, it helps to have some experience with HSS before attempting the higher speeds, depths of cut and feeds you will probably want to use with carbide.

Neil

Anyone downloading the Southbend book and using the advice contained therein for grinding tool bits - should note that the ones shown (at least in my copy) are intended for use in angled tool-holders e.g. where the tool is held at an angle to the shank (rather than parallel to it). The Southbend tools do not therefore have much back-rake shown (as this is provided by the tool-holder) - just side rake...

And of course if you use an angled tool-holder for turning brass - the tool has to be ground with negative back rake...

Regards,

IanT

Many years ago I took a shop class. We were not allowed to use a lathe until we had ground our own tool bits. It is not difficult if you have a proper tool rest in the grinder. I do not understand why many are reluctant to do it.

just had a little go of grinding some hss, made sure the tool was dead centre to the work in the tool post and ive got to say felt quite happy with the results, done some facing off and trimming off a 20mm round bar aluminium, looked to me to have a nice finish, the thing i did notice was the little pip in the centre when i faced off, i could not get that out? i think i will still get a ready made set, but im going to keep having a go at the grinding hss as i did get it free and its not often i get anything free so may as well use it, ive got to say what a great forum everybody trying to help , i realy appreciate it,

regards john

The tool is slightly too low in the tool-post. Try cutting a shim out of an Aluminium Coke Can and putting it under the tool. Or a few shims as necessary to get the height spot on.

Edited By SillyOldDuffer on 08/09/2017 20:13:43

The centre pip is because your tool is not on the centre line, takes practice but you'll get there.

The cowels is a small lathe and carbide insert tooling is not what i would recommend for it .

The only time i would use carbide on a lathe of that size would be if i were machining cast iron and i would use the brazed on tip type that i have sharpened .

HSS tooling will serve you well and don't be scared of sharpening it , the angles are only a guideline and as long as you are close to the mark they will work fine .

buy yourself a diamond lap , knife sharpener or a honing stone as a HSS tool that has been lapped or honed will cut better and leave a better finish

There are a few videos on youtube about sharpening lathe tools , one of the best channels is thatlazymachinists and the host Marc is a retired toolmaker turned teacher . I can just about guarantee you will find something usefull on his channel !

Ian

I am happy to hear your good experience with grinding your own tools. Good for you.

You can get away with some funny looking tools if the ones a friend of mine uses are anything to go by, I did grind up some for him of a more conventional type, but he still used his tools and the finish of the work was just as good.

Ian S C