Tungsten Carbide Tipped Lathe Tools

There are still several sources for the holders that use the two obtuse corners from a CCMT or CCGT insert. I use them quite a lot particularly for roughing or heavy cuts as these two corners seem a bit more durable. Glanze (Chronos) APT do them and I think JBCutting still have them on their e-bay shop will all do reasonably priced holders.

Depending on insert type some triangular ones give 6 usable edges as the neutral ones can be flipped upside down.

My take on indexable was as I said eariler the insert can be indexed around in it's pocket . Industry does not just have one toolpost holder so they don't go swapping holders they simply change out an insert when worn and know the new one will go back in the same position so no changes to setup.

"Insert" probably comes from them being inserted into a pocket in the holder.

PS I DO get on OK with Brazed tips

I sometimes use carbide inserts on my lathe and I don’t run them any faster than some of my HSS tools. Some of the bigger inserts do appear to be quite blunt compared to HSS and it seems they do need higher speed and pressure to cut. I don’t use this type of insert on my hobby lathe. Most of the inserts I use are of the sharp polished variety which work very well on small lathes.

Carbide inserts have two big advantages over HSS lathe tools, both of which make cutting metal cheaper.

Carbide is harder and more heat resistant than HSS. Cutting edges last longer and at the same time can safely generate a lot of heat during the cut that softens the metal so more metal is removed per kilowatt. This alone justifies carbide.

Secondly, carbide inserts are accurately moulded to shapes race-tuned for peak cutting efficiency; this saving big money in a production environment. And because inserts of a given type are identical they can be swapped in the tool-holder without resetting it, reducing downtime and labour costs. Further, as each insert comes with 2, 3 or 4 cutting points and edges, 'n' failed edges are quickly fixed by simply reindexing the insert. No skill is involved.

In comparison using HSS is liable to bankrupt the company! Or would if it weren't for the dreaded Account-Ant. He or she makes short shrift of HSS fans by taking into all the costs into account. True HSS blanks are cheap but then:

• A skilled man has to sharpen HSS, and he costs £££ per hour in training, pay, rates, tax, pension contributions, holidays, overtime, heat, light, and toilet facilities, plus management and admin overheads.
• A decent grinder is needed, not a cheapo hobby job, plus consumables, The grinder takes up space, uses electricity, and has to be checked periodically. Maybe the operator has to be trained to use it, because grinding tools wrongly wastes power and might spoil the finish. More £.
• Once an HSS tool has been ground, it has to be set correctly on the lathe. This takes time, because hand grinding always disturbs the centre height. Unlike an insert, the whole tool is removed, so resetting it involves fiddling with shims etc. This wastes so much time that most HSS shops fit a QCTP and buy several cartridges for it. More £.
• In action, HSS pushed hard doesn't last long, and it has to be touched up frequently. The machine has to stop work whilst the cutter is sorted out. For a business this money down the drain, worse if the operator grinds his own cutters!

Time and money are much less critical in a home workshop, where the general purpose nature of HSS pays off, especially for form tools. I find HSS tolerates mistakes better than carbide too, generally getting a decent finish no matter what. However, the indexability of inserts is very convenient. I think an ordinary 4-way tool-post with a set of pre-shimmed carbide insert tool holders is nearly as quick as a QCTP, and wins in the long run because carbide edges lasts a lot longer than HSS, and can be rotated.

As always much depends on what the workshop is doing and why. I prefer carbide inserts most of the time, but not when HSS is better suited. Agood reason for staying loyal to HSS is owning a classic lathe - they're often too slow to get the best out of carbide. Although not as rigid or powerful as they should be, Far Eastern hobby lathes usually have high enough RPM to get results. Without stopping to do any grinding.

Dave

SoD states: ... failed edges are quickly fixed by simply reindexing the insert. No skill is involved.

Not necessarily. It is much too easy to drop the tiny screw, and it falls, inevitably, into the swarf it has just generated. And the tiny screws look exactly like the scrolls of metal in the swarf. Exactly ...

Cheers, Tim

Having done that once I now change my tips over a tobacco tin lid or similar.

Tony

Been there, done that! It's why most of us keep spare screws! 😄

Luckily for me most of my turning with larger inserts which are indexed after loosening a screw, & not removing it completely.

Cheers.

Stew.