HSS vs TCT

Carbide and HSS both have their place.

I would reccomend getting a few 1/4 inch (or smaller) HSS bits and tool holders to suit. Once you learn to grind a decent tool out of HSS, you will always have the ability to make your tools work for you, instead of having to work around your tools. Save the carbides for the miserable hard materials.

There are many different carbide tools out there. The brazed tip tools are somewhat useful, but really need to be touched up prior to use, and I found them to be very expensive whilst going through the "learning curve", as they usually had a life measured in minutes. The only ones I now will buy are the threading tools, which I use only for making my own internal threading tools of carbon steel.

The carbide toolholders that take replaceable tips are a better deal, if good ones are bought, and tips appropriate to the work done are used. There is a stunning variety of geometries, materials, tip radii, and coatings available, and it is worth a look at an actual catalog to learn what one can about the choices.

Grinding carbide is usually done with a green wheel (specific material name escapes me right now) but they usually leave a fairly coarse edge. This can be cleaned up with a diamond wheel, or a diamond hand lap, to great advantage (Eze-Lap is one brand).

Cheers Trevor Jones

I would suggest to take the hard road of learning to grind your HSS. If you have a good book and accept that it will take some hours of playing around, trying and failing, you will have a lot of knowledge for later. Carbide inserts make you stupid. :-)

I have only one tool holder with carbide inserts that I use often. The rest is mostly HSS. When I started lathe work, I also thought that tools with carbide tips help me, but most of them just broke. :-)

Get a set of preground HSS tools, a benchtop grinder with a white wheel, a wheeldresser, a diamond file (I have a combo 600 / 1200 grit from DMT), some free machining bar stock and learn. It really is worth it! If you don't want to invest in a diamond file, grinding sticks (often available as sets) are OK. They only are much slower.

And to add to the diamond file: I recently bough a ceramic "file" (file is quite wrong, it is just a stick and has a smooth surface. grade was extra fine). It is really incredible how fast you can polish a diamond-filed surface!

Nick

Not much fun when you have 90 of the damn things to make and Mary bloody Poppins is making rude noises in your tabhole.

A bit of history on these tools. Some years ago one of my customer who makes on site boring and facing machines for the oil industry remarked that every machine went out with 4 tipped tools and inserts but came back with none.

They had either been pinched or just lost, the problem was these tools whilst seeming simple were costing £60 to £70 each without inserts. I got some original tools and had special tapered tooling made for the pockets and made jigs to hold these and made some blanks up. They were then professionally hardened and blacked.

These were then ordered in quantities of 20 per profile to go with the machines.

Armed with this experience I then looked for a simple holder to take a cheap tip and made two sizes, one is a 5/8" square shank to take the popular and cheap TPUN16 triangular tip which is used on all my own machines and the smaller 12mm square one with the TPUN11 tip that Mary [ or in truth Ower Gert ] offers on Ebay.

They are cheap in comparison to the branded makes like Hertel but they are well made. The tips do fit the pockets accurately and do not damage unused tips and edges like some that just have a slab sided shape.

We have also though of offering the larger 5/8" shanked tools on Ebay as well and may do a few to test the water. I use these all the while on 4 different lathes.

.

-- Regards,

John Stevenson Nottingham, England.

Visit the new Model Engineering adverts page at:-

Ed Hi, from my experience I must say "possibly", I have struggled for years with TCT tools and have never really been successful with them. I find that they are far too easily chipped and a bind to sharpen. I changed to HSS and tipped tooling and have not used TCT since.

I find HSS much easier to use and to shape for that special job, and much easier to "touch up" for that important final cut. If like me you tend to "creep up" on the finished size then HSS is the only way to go. I started with a set of the pre-ground ones but soon learnt that the normal square HSS pieces were easy to shape for the basic tools and I could get a much keener edge which would remove the final "dust cut". For roughing cuts I now use tipped tooling and change to HSS to finish if needed.

Just ask for a "green grit wheel", I think I got my last 6" one from Machine Mart, seemed OK but as I've said haven't used it much lately.

I've tried a range of tipped tools (mostly 10-12mm sq) from various suppliers, ranging from =A370 - =A310 and they all work OK as long as your machine has a high enough top speed particularly for small diameter work. I recently bought a couple of 12mm tools from Mary (ower Gert?) and found them to be excellent. The tips (nice and cheap) work well for me (Myford/Boxford lathes) and the tools have a "proper" sized holding screw. I will certainly get the larger variety for my large lathe if John decides to sell them. I use mostly mild steel and am still in that "accessory making" stage. I haven't found getting a good finish a problem as long as I keep the speed/feed up and keep one tool for roughing and the other for finishing. I don't like using the oil based cutting fluids with tipped tools as it seems to make the tool rub rather than cut particularly on light cuts.

Best regards

Keith

... and now an explanation why you get seemingly contradicting answers: For carbide, you need a heavy stable lathe.

Nick

Cheers for all the replies!

So, I need a green wheel to sharpen the TCT (got 'em, might as well sharpen 'em), some proper HSS bits and a white wheel to grind them, a diamond file to polish them off & possibly some sort of ceramic stick for final finishing. And a lot of practise.

Then keep the TCT for ripping metal and the HSS for nice* jobs? My lathe is a Southbend 9", so not particularly big or heavy.

I think I got some 5/8ths TCT from Hulcot steam rally, fits well in the toolpost. Are you looking at chucking any of your replaceable tipped holders on ebay soon John? (That is, I got some TCT and I think it's

5/8ths but I'd get a better measurement in metric.)

One thing about HHs bookes: at the beginning of 'Lathe Work' he mentions a fully adjustable grinding fixture as being essential workshop equipment, but then gives instructions for making one at the end of the next book 'Milling - complete course'. Er, how do I get from here (start of Lathes) to there (end of Milling) without one?

Esp. as I don't even have a milling machine!! And, and, sharpening milling cutters, doesn't that lead to having to build a Quorn??

*nice > wrote:

Just to confuse matters further, I've got an old set of Myford carbon steel tools which still get used for finishing. They were the set I bought with my new ML10 way back in Ted Heath's three day week time and they still get used on occasions in preference to HSS and inserts.

Jim.

You need tools to build tools. Often enough, you need to make another tool to make a tool. :-)

Hand grinding is well enough for the beginning. Doesn't Hemingway Kits offer a nice grining fixture for lathe bits?

Nick

You don't need to spend much time at this game to realise the phrase "fully tooled" on lathe adverts is a bit of a stretch.

Fully tooled I thnk means enough tooling to start something but not necessarily enough to finish anything!!!

Steve

Isn't "fully tooled" like "a bit pregnant"?

Those here who are "fully tooled" (no pun intended with this example) will raise their hands.

Nick

In message , snipped-for-privacy@gmail.com writes

[snip]

How about...

... usual disclaimer.

Read the last chapter first.

.

-- Regards,

John Stevenson Nottingham, England.

Visit the new Model Engineering adverts page at:-

Ahh, thanks John, pointing me in the right direction. But no mention of kippers?

Jim, do the carbon tools give a better finish than the HSS then? Don't they need to be sharpened more often?

Thanks for the link & suggestion of the Hemmingway grinder guys, but seriously, I don't intend to pay that much for my next car!

I've seen a pic of a metal template that is made with the fr> On 30 Aug 2006 08:25:13 -0700, snipped-for-privacy@gmail.com wrote: >

I use a protractor (seldomn) or such a template for grinding (and aligning) tools for thread cutting.

Nick

I tend to use them for finishing and I don't push them hard. You do need to keep them sharp but that means just using a small hand stone on them on a regular basis.

I don't know that they give a better finish than HSS.but on a my smaller size lathe, they give me an option which is easier to use in some setups.

Also, making carbon steel tools from silver steel rod is a quick way of making your own specialist tools - like form tools - where you can turn up the shape in the lathe, then harden them for use.

Jim.

The sherline site has a very good idiots guide to freehand grinding:

I just freehand my lathe tools on an offhand grinder. once you get the basic idea (pointy and sharp) then it only takes a minute. I havent done much threading (only 2 pieces), but I offhand ground the threading tool to 'pretty close' then used an existing tap to guide me into the final shape, using a diamond file, which also gives a nice finish. I have 3 carbide tools, a tiny boring bar, made using a tct tip off a circular saw blade, and a lh and rh tool from the same saw. (it was 50p brand new, got 24 tips from it :) I know they are probably the 'wrong' grade but works for me. I only use them in Cast iron. YMMV.

Dave

Ed, I second what Dave has said, just grind them freehand you will soon get the hang of it. The angles do not have to be within a couple of minutes or anything in fact you will soon change them slightly depending on how the material cuts. A couple of pieces of 3/8" HSS will only cost a few pounds grind them up and see how they work, if they don't cut try again. It really is cheap training and once you have mastered the technique you will never be without the right tool again.

I don't believe there is a "best" tool that will produce a superb finish on all occaisions and I've found that by experimenting with speeds/feeds/depth of cut etc you can make most types of tool do a reasonable job. I did at the outset spend a lot of money trying all sorts of "magic" tools, it didn't help my turning at all just kept the tool dealers in caviar. Of course if you are sharpening end mills etc then a decent tool grinder is essential, for normal lathe tools I find an off-hand grinder and a couple of hours invested in practise sorts out most problems. A fine diamond file or stone allows me to dress the edge of a finishing tool when necessary. To rough things out with heavy cuts I use tipped tools to stop me having to sharpen regularly, it's really for my convienience not for the quality of the cut.

Best regards

Keith

This is very much my experience too -

It doesn't take long to get the hang of off-hand grinding HSS tool bits. As Keith says, just a few hours and you can get on top of it.

I've been working some ally bar in the lathe and needed a really top dollar finish - the tool I used? A re-ground letter stamp! Just ground to a small radius round nose and then honed. It chattered with a "heavy" cut but a very light cut and it produced a mirror finish. The only reason I bought some carbide tipped tools was I had a few pulleys to cut from Cast iron bar and HSS runs out of steam too quickly on the roughing cuts. I've also discovered that you still need to revert to HSS for finishing cuts.

You also need to make sure that that everything is a rigid as possible, parting off usually exposes weaknesses in the set up.

Getting a good finish is just practice and experiment. Use known "good" materials to remove at least one variable. I have access to some scrap materials (ie the corroded and grotty) and its typically unusable. Harold Hall recommends free-cutting steels for many components, because they are easier for novices like me to work with.

Nothing like getting stuck into a piece of aluminium bar and finding there was a cylinder jacket hidden inside!

Steve

Like this:

The sleeve was roughed out with a carbide tip tool and finished with home ground HSS from blanks. The bore is a different story and the gents here have kindly given me a few pointers to sort that.

The cylinder jacket is done with HSS tooling except the waste where I ground up the letter punch.

Steve