Round indexable tips.

What are these round indexable tips for ? I don't think I have seen them before today. Photo #6 :

https://www.ebay.com.au/itm/Lathe-Turning-Boring-Bar-Holder-Carbide-Inserts-Wrench-Tool-Cutting-CNC-Machine/183526040156?hash=item2abb01225c:m:m9AhxvNRZPMTTvWQ4OUWqwQ:rk:8f:0

Why did that link not work for me ?

Edited By Brian John on 27/01/2019 04:31:48

Hi Brian,

I have seen milling tools with round inserts, something like this, and profiling lathe tools.

Thor

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Welcome back, Brian ... It's been a while

The link needs to be inserted via this icon:

**LINK**

MichaelG.

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P.S. ... Just for info. this shortened form of the URL would also work:

https://www.ebay.com.au/itm/Lathe-Turning-Boring-Bar-Holder-Carbide-Inserts-Wrench-Tool-Cutting-CNC-Machine/183526040156

https://www.ebay.com.au/itm/Lathe-Turning-Boring-Bar-Holder-Carbide-Inserts-Wrench-Tool-Cutting-CNC-Machine/183526040156

... because everything from the ? onwards is just ebay tracking how you reached the page.

Edited By Michael Gilligan on 27/01/2019 07:11:27

I keep thinking about buying one of these, but my son is talking of changing lathes and I don't want to buy too small a tool.

Round tools can produce a much smoother finish, especially if the feed rate is so high that a normal tool produces a visible thread (as on a mini lathe). I used to use a round toolbit (HSS - it was 40 years ago) in a tangential holder to produce tensometer test bars as the round tool didn't produce stress raisers. Think of it just as a tool with a very large nose radius.

Brian G

They are also sharper than a lot of standard carbide inserts. Here's one being used on aluminium alloy.

youtube

Martin C

As Thor said it’s a profiling tool. You can get the standard gold inserts for steel or the polished silver ones for plastics and light alloys. The polished inserts are now commonly seen on Woodturning tools for hollowing.

Mostly mine does profiles, but I've found round tips work well for ordinary cutting too - unless you need to work up to a sharp shoulder! One advantage of round tips is that worn inserts can be rotated slightly to present a fresh cutting edge, potentially giving them a longer life compared with the tips of two, three or four cornered inserts.

Dave

I have little experience with these round 'inserts' so far, but I have had good finish up to now. I wonder if that could be because the round insets are very finely finished - I would say ground on the OD, perhaps. The actual finish of the triangular (etc) versions seems to be straight from the sintering press. Any thoughts?

And they do seem to be popular with wood turners.

Regards - Tim

The 6mm polished inserts work very well on wood:

**LINK**

I've had one of these holders for several years and seldom use it, the radius is too big for most of the fillets I want so it just sits in the draw.

I do use the rounded MRMN inserts quite a lot with a 2mm dia end and for something a little larger tend to reach for the cranked brazed tip tooling with a 3-4mm dia on the end as I have not got round to buying a holder for larger MRMN and MGMN inserts

I have a little fly cutter with round inserts. Seems to work ok if I go easy with it but when I have finished rebuilding my mill gearbox I plan on making a bigger fly cutter with Hss cutter. I gave a few plans for them so just need to pick one and go for it.

I use them for profiling:

In this case the taper and ends of connecting rods:

For smaller work I use straight inserts with a rounded end, similar to those mentioned by JasonB:

To avoid chatter use an insert with a slightly smaller diameter than the fillet to be formed.

Andrew

Edited By Andrew Johnston on 27/01/2019 20:01:44

I also use the 6mm Glanze tooling. Made a great job on a barstock flywheel. Needs a very rigid setup to a avoid chatter. Big advantage is being able to cut in both directions.

?

The default fine feed on a mini lathe is 4 thou, you shouldn't be getting a visible thread when finish turning with one.

Neil

The round insert is the strongest insert shape available. Many years ago I had to turn down some 6" and 8" dia. percussion drilling bits. It was an interrupted cut in alloy steel. Round inserts were the only insert that gave reasonable tool life. The lathe was an old Lehmann 20" x 120" lathe. For hobby and model engineering I doubt the round inserts are of much use except for profiling. On smaller lathes the large tool contact is likely to induce chatter.

To be honest Neil, a rocking motion of the saddle probably didn't help much with the finish! Whilst curing that I discovered where the screws I kept finding in the drip tray and splashback were coming from... Since then a combination of having fitted a carriage lock and only making small components that didn't require more than the compound's travel have meant that I haven't had cause to use the feed on the few occasions on which I have had sufficient mobility to use the lathe.

Brian

Brian