[Newbie] Hammer Effect On Cutting Tool When Rough Cutting.

[faavs730222]

Hi I took the discs back to the engineering shop. They cut the ID to 100mm. I am now busy with the OD. I fixed the disc in the 3 jaw chuck. I am running above 38rpm, because i am using a carbide tool. Because the OD was cut very rough, the workpiece have a hammer effect on the crossslide an tool. I am not sure how to approach the work. The OD differ up to 5mm at places and the biggest cut I can take is about 1mm. The rough disc.The OD and ID finished. The Carbide Tool I am using.


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[TomS]

Hi I took the discs back to the engineering shop. They cut the ID to 100mm. I am now busy with the OD. I fixed the disc in the 3 jaw chuck. I am running above 38rpm, because i am using a carbide tool. Because the OD was cut very rough, the workpiece have a hammer effect on the crossslide an tool. I am not sure how to approach the work. The OD differ up to 5mm at places and the biggest cut I can take is about 1mm. The rough disc.The OD and ID finished. The Carbide Tool I am using.


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If your lathe has the horsepower try taking a cut where the tip of your tool cuts below the torch cut surface. Adjust the feed rate as necessary.

As you have found out torch cutting hardens the surface and leaves an irregular surface that takes a toll on tool bits, especially carbide. Getting under the hardness and rough surface helps to preserve the tip of your insert.

Tom S.

 

[RJSakowski]

If I am machining an O/A torch-cut workpieces, I grind the edge back to where there is fresh material and the slag is removed. An O/A torch will carburize the steel and the quick cooling leaves it in a very hard state. Cutting with a plasma torch doesn't have that effect on mild steel but medium to high carbon steel may exhibit hardness at the cut edge due to the intrinsic carbon content and the rapid cooling.

 

[Martin W]

High speed steel cutting tools may be your friend in this case. At least until you can get a full cut.
Cheers
Martin

 

[faavs730222]

High speed steel cutting tools may be your friend in this case. At least until you can get a full cut.
Cheers
Martin

Hi, I am using the Index able Carbide bit (Shown in the picture). At first I was running the Work piece at about 380rpm with a feed rate of 0.13mm/r. I got a lot of "Chatter" actually it sounded more like hammer blows.

Do you suggest I take the speed down to about 45rpm, and decrease the feed rate also and try for a DOC of about 2mm? Or should I take very fine cuts?

 

[Downunder Bob]

What is the OD? try the biggest HSS tool you can set up make everything as rigid as possible set your cutting speed at or below the correct speed for the dia. take the heaviest cut possible. If the tool still burns or abrades go even slower, but use a good feed, finish is not important here. Once you get under the hardened oxy cut surface you can switch back to the carbide insert for finishing.

 

[Tony Wells]

Approximately how much oversized are your blanks?