Chatter in groove cutting

[Nogoingback]

304

304 will work harden if the tool rubs or isn't cutting well. Mr Whoopee's suggestion of boring would allow
smaller cuts but with with positive cutting that would help avoid work hardening.

Kevin's suggestion of making a plinth is also very worthwhile. Most of the small machines benefit from
the extra rigidity.

 

[phelop]

304 will work harden if the tool rubs or isn't cutting well. Mr Whoopee's suggestion of boring would allow
smaller cuts but with with positive cutting that would help avoid work hardening.

Kevin's suggestion of making a plinth is also very worthwhile. Most of the small machines benefit from
the extra rigidity.

I will try to use carbide insert maybe. I look to find one that it can cut the groove and then, move to the side to get de right widht. I make some test to build this part:

 

[Nogoingback]

I would be inclined to drill close to the ID first, clean up with a boring bar and finish wth a reamer. Then get a tool in there to cut the grooves. I don't think carbide will do you any good on a light lathe like that: HSS wiould work well for you.

 

[Flyinfool]

You cutter is either very dull and/or has the wrong relief angle ground on it. the face of the tool is rubbing before the cutting edge makes contact. Try sharpening the tool and make sure it is exactly on center.

 

[MrWhoopee]

Ah, now that we see the drawing, boring is out. As previously mentioned, a narrower, sharper tool. Carbide won't help, it will probably be worse. 303 or 416 stainless would make a HUGE difference.

 

[mikey]

I agree with UlmaDoc and Mark - your tool is not sharp and the geometry is off, plus you're probably working with work hardened material.

If you look at the tip of the tool, you can see that there is very little relief under the cutting edge. It looks like there is maybe a few degrees there but not enough. This will result in rubbing (no cutting) and heat build up with resultant work hardening.



The corners of the tool are also rounded and the cutting edge is crumbling. If this is a HSS tool then you can correct all of this easily. My suggestion is to grind a 7 degree relief under the cutting edge and clean up the sides so your corners are sharp, then hone the top flat.

I hope the work piece you showed in the picture is a practice piece because that chattered up section is going to be hard to cut through. With a good tool it is possible to cut through it. Bring the tool into contact and turn the work by hand, gently pushing the tool into the cut. A sharp tool will cut through the hardened layer this way. When you get through that layer the tool will begin to cut freely. At that point, you can turn on power.

If you are going to do this often, buy a solid carbide grooving tool from Micro 100 in the width you need. Forget inserted carbide for this job; the tip will just snap off.

 

[phelop]

I agree with UlmaDoc and Mark - your tool is not sharp and the geometry is off, plus you're probably working with work hardened material.

If you look at the tip of the tool, you can see that there is very little relief under the cutting edge. It looks like there is maybe a few degrees there but not enough. This will result in rubbing (no cutting) and heat build up with resultant work hardening.

View attachment 345761

The corners of the tool are also rounded and the cutting edge is crumbling. If this is a HSS tool then you can correct all of this easily. My suggestion is to grind a 7 degree relief under the cutting edge and clean up the sides so your corners are sharp, then hone the top flat.

I hope the work piece you showed in the picture is a practice piece because that chattered up section is going to be hard to cut through. With a good tool it is possible to cut through it. Bring the tool into contact and turn the work by hand, gently pushing the tool into the cut. A sharp tool will cut through the hardened layer this way. When you get through that layer the tool will begin to cut freely. At that point, you can turn on power.

If you are going to do this often, buy a solid carbide grooving tool from Micro 100 in the width you need. Forget inserted carbide for this job; the tip will just snap off.

Yes, is a practice part, the tool that I have is actually a micro 100. (.125 groove ), I will follow you'r advice and look for different stanless steel.

Thanks

 

[phelop]

Ah, now that we see the drawing, boring is out. As previously mentioned, a narrower, sharper tool. Carbide won't help, it will probably be worse. 303 or 416 stainless would make a HUGE difference.

I need to weld this part on mild steel, so I need good weldable stainless steel.

Regards

 

[john.oliver35]

You have gotten good advice here about sharpening. I can't tell for certain how much of the 'crumbling' that Mikey sees is the actual tool or particles on the tool. Note: You can tun up the edge a little bit on these carbide cutters with a small fine diamond card. I would put the card/stone on the table and move the baring bar in for something small like this.

Inserted carbide likely won't help. As frustrating as it may seem, sharpening and setup are likely the keys here. This is advice from someone who just tried to fix an internal threading problem by buying a carbide insert bar. This made things a lot worse a the speeds rigidity of my little lathe. Listening to Mikey and others here to keep working on the HSS solved my problem.

Also, you sometimes see advice to put the tool tip either right on center, or error a thou or two low. For this type of inside boring you would want to do the opposite and error a thou or two high so that flex in the tool lightens the cut rather than causing it to dig in.

 

[MrWhoopee]

I need to weld this part on mild steel, so I need good weldable stainless steel.

One piece at a time the important info is revealed. Sketch of welded assembly?