non-standard insert?

A few years ago I was starting to get together stuff for my mini lathe. I bought a set of 3/8inch shank indexable tools with triangular inserts. I'm not even sure what the inserts were meant for but I recently found that they work very well on Rebar steel without wearing out too fast. So that could be the answer to that unknown.

Sometimes they work really well but HSS or braised carbide tips sometimes,do better. I saw a YouTube video which helped me to do much better than I thought possible by tiffling my carbide tips (green stone etc)

The inserts are triangular with 0.4inch / 10mm length.

The tools were pretty cheap and they don't owe me anything but it may be worth replacing the inserts if I could get hold of them. I can only find 11mm inserts from my usual sources so it may be better just to cut my losses.

Does anyone know of a source of imperial(?) triangular inserts or should I must bin the tools as they wear out or break?

Supplementary is where to get good value metric indexable turning tools.

How does the toolholder looks, pos, neutral, negative-?

One can add a shim(s)(Determine thickness to change angle at insert tip when cutting) to rear of toolholder temporarly and tighten to see if it cuts better at a steeper angle, I did that and then increased the angle from 5-7 degrees and cut toolholder in mill to achieve that for toolholder.

If they dont have a centre hole and flat topped TPUN, if they have a chipbreaker ridge TPMR.

Sizes should be all metric

Edited By Dave Halford on 18/02/2023 21:00:53

I've got a box of triangular inserts TPUN 16 03 08 415.i don't think these are what you are looking for, but if anyone can use them I'm open to offers.

A good offer - for some lucky machinist but mine have a hole in them. They must be something like T??T1002. Much smaller.

It looks like I'll have to just use up what cutting points I've got and get something that can be sustainable. I have a boring tool and managed to replace the inserts. I didn't;t believe it till the new inserts fitted and cut as they should.

I guess a tool with a reliable supply of inserts will be pricy and I'll just have to suck that up. The whole business of indexable seems a bit arcane for the beginner.

It's somewhat arcane full stop due to the sheer number of variations developed to cover the full variety of use cases.

That's the reason that industrial customers expect the likes of Sandvik-Comorant, Mitsubishi, Kennametal and Kyrocera to maintain significant technical sales departments and teams of demonstrators to support their customers if they want to retain their business.

Milling inserts seem to be especially bad as non-standard and proprietary inserts are much more common.

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This said, if you take care to purchase tooling which takes widely used and available inserts, it shouldn't work out expensive.

Especially if you get something for which generic inserts are available from the likes of APT, rather than being tied to a Branded supplier.

How are you measuring that 10mm?

The sizing of inserts is measured by a theoretical pointed triangle but tip radius will reduce the physical measured length from corner to corner, so if they have a large corner radius they could actually be 11mm.

Anything on the sides of the holders as the codes on them should give a good indication of not only shape but fixing method, angle, etc

Good morning all.

I had this issue with a large left handed boring bar that I acquired with a job lot of QCTP holders I bought. It lounged on the shelf for several years.

Then I decided to make a whopping great fly cutter for my mill for which the boring bar would be ideal. There was one insert on the tool. I spoke to Barry at Gloster tooling and from the measurements he correctly identified it. So it may be worth speaking to any good supplier like Gloster or APT and see if they can help.

Carbide inserts are a blinking minefield! Quite often they're measured by the size of the theoretical inscribed circle that would fit within the insert. For example CNMG turning inserts could be described like this; CNMG 120408. The 12 being the inscribed circle. The 04 being the thickness, and the 08 being the tip radius.

Having had a hefty lathe for many years I had pretty much got the hang of turning inserts, and then I bought my mill. Whooo Boy! It was a whole new ball game! aka minefield!

Cheers.

Stewart.

Great!!! `Thanks. That's what I needed. I was using the between jaws of a calliper but, allowing around 0.5mm for radius gives a convincing 11mm. I will go ahead and order some from the vast number of 11mm available.

Here's another example of the inadequacy of this website - it seems to be impossible to quote more than one posting at a time. WHYYYY?

Exactly so. Industry have to optimise cutting in a way totally foreign to my workshop, where good results are got from slow traditional methods and experimental fumbling. Production machines do the same job repeatedly, and it's well worth fitting them with the ideal insert for the job because a 1% saving on a £1M production run is £10000!

Home workshops are much more general purpose and fitting a specialist carbide insert to our equipment is likely to be counter-productive. The insert is probably designed to cut a particular material at a higher RPM, feed-rate and depth of cut than a small manual lathe can manage. There's a high chance of a mismatch between what we cut and what the insert is race-tuned to do.

Fortunately, there's an easy way out for beginners. Proceed to the ArcEuroTrade website and look at the limited range of inserts they sell to hobbyists. (Other suppliers available.) The range are a good match for general-purpose work on hobby machines. A further trick is to use the sharp type for Non-ferrous metals on steel. It happens that the edge optimised for high-speed industrial cutting of Aluminium is also well suited to cutting steel at hobby rates.

I bought a set of carbide tooling with my big lathe and was very disappointed in them at first. Turns out they're very good for heavy cutting in steel, but poor at taking light cuts. As most of my machining involves light to moderate cuts, I only use the set for roughing out. Most of the time smaller sharper inserts are a much better match to what I do.

Not sure it's a good idea for beginners to wander the internet looking for cheap carbide inserts. Yes there are bargains, but it's easy to buy the wrong sort. Proprietary inserts requiring special holders,, inserts that fit obsolete holders, and above all inserts designed for a narrow range of specialist industrial cutting that won't work well on a mini-lathe! Bargains are easier to spot when the buyer knows what to look for!

Dave

May I suggest another reference source?

Greenwood Tools, now closed, yet the website is still available (I've just checked). Up near the rhs of the top line, will be found Technical Information. This then gives information about carbide inserts including cutting & turning speeds. It also gives some information about grades of Carbide, but be aware that it then refers to Greenwoods own designation.

Good luck,

Peter G. Shaw

p.s. I ended up going to APT for the few inserts I use. I have to say that I prefer HSS, or even High Carbon steel, but then I'm a Luddite!!!

Edited By Peter G. Shaw on 19/02/2023 11:12:28

Another possible source of tip would be JB Cutting Tools

The codinbg for the insertsd should tell you a little aboutbthge inserts.

If it includes an M the insert is moulded and will not be nrazor sharp (Slightly blunt, when industry run at high speeds the localise heat soften the workpiece. The inserts for non ferround include a G, signifying ground.

The final figure will state the radius on the tip, probably 04 or 08.

Howard

The triangle I bought has dimension 11mm and works fine. Cheers for the discussion guys.