For Andre - Indexable Inserts

[Anorak Bob]

Andre asked me what inserts I use.

BT

[Stustoys]

Hi BT,
I give up, whats the screw on the side of the thread cutting holder for?(I feel a :doh:moment coming on)
Also does anyone know the reason why the carbide backing piece helps?

Stuart

[Anorak Bob]

You know Stu, I was looking at that same screw last night thinking the same thing. I had better pull it apart and find out.

[pipeclay]

The screw holds the shim/seat.
The shim/seat gives support to the cutting tip.

[Stustoys]

The screw holds the shim/seat.

Well :doh:. See I knew it was coming lol


The shim/seat gives support to the cutting tip.
Yeah but I dont get how. After all the area of steel below the seat is the same, though it isnt as deep as you have to cut more away to fit the seat.(although the seat on this holder does extend a little further towards the cutting tip than the holder does, I've seen others that were flush).

Thanks

Stuart

[Jekyll and Hyde]

Well :doh:. See I knew it was coming lol


Yeah but I dont get how. After all the area of steel below the seat is the same, though it isnt as deep as you have to cut more away to fit the seat.(although the seat on this holder does extend a little further towards the cutting tip than the holder does, I've seen others that were flush).

Thanks

Stuart

I think the idea is that the shim isn't brittle like the insert, so by having it run out close to the tip it helps to stop the tip fracturing in a cut, but the seat is replaceable in a crash, rather than having to throw the whole tool like you might if the toolholder itself supported the cutting tip... The seat being made of a different type of material to the holder probably holds a clue in some way.....

The seat on mine ends only a little past the end of the holder :D Don't know whether it came like that with the lathe, or whether I broke it. Either way, doesn't seem to matter too much that the tip isn't fully supported, still threads pretty tough steel without issue. One day I'll remember to track down a replacement seat...

As far as a flush seat goes, that doesn't make much sense to me, unless it just allows for thicker inserts by swapping it with another?

[Anorak Bob]

The screw pushes the anvil sideways into the socket. Ease of manufacture would be the main reason for this design I would think. Simplest way of providing tip support. I had a look at the threading tool holders pictured in my Kennametal and Seco catalogues. Exactly the same.

[Stustoys]

Hi BT,
Thanks, They certainly give more support to the tip than any other the other tool holders I have seen. Do you know if they you can get different seats for different thread profiles?

Stuart

[Anorak Bob]

Kennametal refer to Seco's anvil as a shim. It appears that for one size of insert the one shim that suits that size will cover all thread forms. Kennametal have that many variations that it becomes mind boggling. If you are real keen I can post a few page photo so you can share in the confusion.

[welder]

Thanks for that I am trying hunt down some quality holders and inserts for my lathe and I understand the mind boggling selection the book we have at work is as thick as a phone book :oo:

[Stustoys]

Thanks for the offer BT but inserts confused me more than enough now without adding to it. I'm unlikely to have a tool holder that needs shim anytime soon.

Stuart

[Anorak Bob]

The Kennametal inserts are suitable for gutless machines and can cope with interrupted cuts. They are High Positive. Have a delve into Kennametal's labyrinth on line.:U

[Dave J]

Thanks for the extra pictures Bob,:2tsup:

Dave

[eskimo]

also some tool holders have different thickness shims to allow for different thickness inserts

[jack620]

Bob,
Is the box with the thread cutting inserts the blue one in the third picture? I want to make sure I have the correct part number.
Chris

[pipeclay]

If you are cutting Imperial threads you will require a different tip.
You may require a different tip if your cutting a bigger or smaller pitch range,same goes with TPI.

[jack620]

Pete, I assume you were talking to me. My lathe is metric so I guess I'd start with a 60 degree tip. That would also allow me to cut UNC and UNF too wouldn't it? Am I right in thinking it's only BSW that requires 55 degrees?

[pipeclay]

Yes but depending on the pitch you will need different tips.
Any 60 degree thread form can be cut with the correct Pitch/TPI tip.
Same applies to 55 degree thread forms.

[Anorak Bob]

Bob,
Is the box with the thread cutting inserts the blue one in the third picture? I want to make sure I have the correct part number.
Chris


Chris,

The part number on the box is for a 60 degree insert. I have both 55 and 60. Those two cover most thread forms. Watch out for BA which is 47.5 degrees. Then there are ACME, square and buttress threads to keep you on your toes. Kennametal and I imagine others offer ACME inserts. Square and buttress would most probably be grind your own.

Bob.

[Log]

Pete, I assume you were talking to me. My lathe is metric so I guess I'd start with a 60 degree tip. That would also allow me to cut UNC and UNF too wouldn't it? Am I right in thinking it's only BSW that requires 55 degrees?

Just a bit more on what pipeclay said.

The threading insert shown in Anorak Bob's pic:2tsup: is a full form thread cutting insert, you will need a different insert for each pitch thread that you want to cut. A full form insert will have the correct geometry for only one pitch.

If on the other hand you get a simple V profile insert then the insert will cover a range of threads. The Sandvik catalogue indicates one insert covers 28 - 14 TPI. and another one covers 14 - 8 TPI in the Whitworth range. In the metric/Unified threads one insert covers 1 - 2mm pitch/24 -12 TPI and another one covers 1.5mm - 3mm pitch/16 - 8 TPI.

The simple V form of course doesn't cut the crest of the thread like the full form inserts do.

Just putting this here for anyone who doesn't know.

Cheers.

[jack620]

Thanks Bob, Pete & Log. As usual it's far more complicated than I thought.
I think I'll go for a selection of V form inserts. More research required.

Chris