Small Ground (GT) Inserts?

All, a couple of years ago I was advised to try using ground GT inserts to get a decent finish on something or other (I think it was the stainless or silver steel valve rod on the Stuart 10V). Since then I've found that they give an excellent finish on most small components, in a range of materials from stainless steel to aluminium.

I have an ArcEuro square tool holder ( ARC SSDC-N 45° Turning Tool Holders - Arc Euro Trade , which I use for chamfering, but the standard insert (SCMT060204) seems a bit "blunt" for making very small cuts on small diameter work.

I'd like to use ground inserts in this tool, but Arc only seem to supply them in 9.525mm side lengths ( SCGT Square Uncoated Carbide Inserts - Arc Euro Trade , but I need 6.35mm length.

A Google search doesn't give any results for what I assume is the correct designation: SCGT 06(T)304.

Any ideas?

Thanks.

Does not seem to be much about in SCGT060204, most seem to start with the larger 09 size

Yes, I can't find anything at all. It's a shame because it would be great for smaller workpieces.

I guess I could get the larger holder, but that kind of defeats the object.

As with other folk above, I've had a good look around, including Chinese sites and failed to find SCGT060204 anywhere, so I guess either you need to move to a larger holder, which as you say defeats the object.
On the other hand, you could buy a replacement holder and go for the diamond shaped inserts at the smaller size, as CCGT060204 are readily available; I've just bought a box.

Last comment relates to your SCGT06T304 assumption above.
I'm not sure it's correct; the T3 part refers to the thickness
02=2.38mm
T3=2.78mm
03=3.18mm
T3=3.97mm
04=4.76mm

I'm not sure that XXXX06T304 would be common in any shape; I think all my 06 sized ones are 02 thickness.

Bill

Most small parts I just run a fine file against the corner of the rotating work to remove any burrs. I do have a 6mm HSS tool that lives in it's own QCTP holder that gets used if I need a larger chamfer, just ground 45deg on each side to meet at a 90deg point.

Thanks Bill, yes that's why I put the "T" in brackets. Either way, there's nothing out there.

I do have the diamond shaped GT inserts, which I've put in my L/H, R/H and straight holders. They are my "go-to" tools for most materials these days. I just thought It would be nice to have a 45 degree chamfer tool in the same series though, since I already have the holder.

Yes, I often do the same, but for getting things consistent (e.g. the small chamfers on the P.R. eccentric fitted bolts), I try to use a tool not a file. I'm not yet skilled enough to get really consistent results that way, and where there are multiple pieces close together, inconsistent features can look a bit naff.

I wonder if the left-hand turning tool with the diamond insert gives 45 degrees for chamfering when set perpendicular to the bed?

I'm not at home at the moment, but that might be an option, albeit making the tool holder more likely to hit the chuck at small workpiece projections.

You nee dto set it at an aggle for a 45deg chamfer as the shape is 55deg on your DCGT inserts

I'd have thought this application cries out for a suitably ground HSS tool, say from a 6mm square blank. Low cost, effective and no need buy an additional insert tool-holder.

Exactly what I use but a larger HSS blank to suit my tool post.

Tony

And me. But mine is double ended so it drops in both sides of the QCTP. That way one tool can be fed along , or across, the axis of the lathe and deburr bores and any other edge created, saving on tool holders

If you do want to go the insert route then Glanze (Chronos) do a similar holder for the CC*T inserts that will give you almost a 45deg chamfer on either side

The problem with the insert ones is you can't get a decent internal chamfer on anything much less than 25mm dia without the holder/insert rubbing, with HSS you can grind clearance on the side that gets used for internal cuts

You really need to invest in another shape of insert and holders. For small ones, I would recommend DCGT 07 size inserts which are available in different nose radii and holders to suit them and the correct size holders for your lathe.

Oldmart how do they do 45deg chamfers without swinging the tool post around which is what the OP wants. His main tools of choice for general turning are already DCGT 07

In his orignal post, he says his current inserts are SCMT060204 . The 04 at the end is the corner radius, which he considers too blunt.

An SCGT060204 will have an identical corner radius. The only difference is one is ground finish, the other sintered/moulded/pressed (the third letter of the insert description is the tolerance).

Hence, it is perhaps no wonder you cannot find them as they would offer no advantage.

It is possible to find SCGT060202, which have a slightly smaller corner radius.

I think the "bluntness" referred to by the OP is the cutting edge of the SCMT insert, not the nose radius. SCGT inserts, primarily for non-ferrous metals, are considerably sharper on the cutting edge.

Correct.

Yes I understood it was the "sharpness" of the edge all along as it was me who first suggested to Doc that he try the **GT inserts and one only has to look at his other threads to see they are almost exclusively what is being used. They are ideal for small fine parts on lightweight machines. So in this case the inserts being sort do offer an advantage

As the tool is being used mainly for cutting chamfers the tip radius in this case is irrelevant as it's the edge being used

Tip radius is more to suit the part, again with the small parts being made a 0.2mm tip radius leaves the smallest internal fillets when turning to a shoulder and required the least relief of a mating holes edge. The other tip radii can be made good use of when a larger internal fillet is needed such as shown yesterday in my "Progress" thread

Although the SCGT0202 and 04 can "be found" on google I could not see a source that was easy to buy from in the UK and preferably in less than a box full at commercial prices.

Edited By JasonB on 30/03/2023 07:38:36

Jason, yes, once I’ve found something that works, I’ll stick with it. As you know I find HSS tool grinding a massive pain in the arse, and will only do it as a last, last resort.

I don’t use the GT inserts for fly cutting, but for most other things they seem to give a good finish and I find them nice to use so…why not? I know the experts might disagree on where and when they should be used, but there we go.