Carbide and Ceramic Inserts...

[Murray Kish]

Been looking on the Sherline site and the various tool bits, etc. From my readings, I have the perception that the carbide insert tools are far more efficient at cutting, and likely an adventure I'd be willing to try.

However, they are not really that cheap, and I have a few questions:

- What's the difference between the carbide-tipped tools (ie. brazed on?) and those that you can screw in the little triangular or diamond shaped tool tip?

- There are so many different types available? What is the most common, and/or when would I need the others? On Sherline's site there are:
55 degree (and holder)
80 degree (and holder)
35 degree??
ceramic?
negative rake??

- I think you also need a special tool-post to hold these, but I'm not quite sure on that one....(will they fit into my regular-issue rocker toolpost that came with my lathe?)

Murray

[MPWR]

I haven't used insert cutters. Mostly because I haven't felt the need to upgrade- for the machining i do, HSS and brazed tip does fine. My understanding is that insert cutters become more valuable if you are cutting harder materials, such as steel and 'exotics'. I'm sure they cut aluminum beautifully, but they aren't the only things that will.

Brazed carbide tipped cutters are a good option. I get mine at Harbor Freight. They're, uh, pretty economical, and do the job well. The 60 deg cutter is of course perfect for cutting threads, but it's also become one of my favorite 'detail bits'.

If the the concern of whether your tool post will hold the insert holders is holding you back, don't let it. Tool posts are very easy to make yourself, to hold whatever you need. Sure, Sherline would be happy to sell you a black anodized one- but I wouldn't guess that they sell alot.

Anyone else have experience with inserts?

[lam90]

Originally Posted by Murray Kish

Been looking on the Sherline site and the various tool bits, etc. From my readings, I have the perception that the carbide insert tools are far more efficient at cutting, and likely an adventure I'd be willing to try.

However, they are not really that cheap, and I have a few questions:

- What's the difference between the carbide-tipped tools (ie. brazed on?) and those that you can screw in the little triangular or diamond shaped tool tip?

This is possibly the easiest of the question that you have asked. Brazed carbide tip tools have only one cutting edge per tool. You damage the cutting edge and you replace the tool and you will damage the edge sometime.

Those with the screw in little triangle or diamond shaped tool tips(more commonly referred to as indexable inserts) have more cutting edges per tool and they are replaceable. If the tip has a negative rake then the indexable insert can be turned over as well as rotated giving you twice the number of cutting edges. If it has a positive rake then it can not be turned over so you have only the three or four edges to work with.

- There are so many different types available? What is the most common, and/or when would I need the others? On Sherline's site there are:
55 degree (and holder)
80 degree (and holder)
35 degree??
ceramic?
negative rake??

Well, the most common type is carbide tools with the triangle shaped indexable inserts. If you are going to buy your first set look for those that come with positive rake they will cut more smoothly then those with a negative rake. Also look for sets which you can buy High Speed Steel (HSS) inserts as well as carbide inserts.

At the speeds and feeds that most of us home shop machinists use, high speed steel will provide a better surface finish than carbide inserts. In other words, you can do better work with high speed steel. For roughing cuts, use carbide. For finish cuts, use high speed steel. Because these tools are indexable, you can simply change the insert, and resume cutting at the same tool position. Last tip is look for tips that are ground not just cast. Ground inserts will have a finer finish and therefore cut more smoothly.

- I think you also need a special tool-post to hold these, but I'm not quite sure on that one....(will they fit into my regular-issue rocker toolpost that came with my lathe?)

I really don’t know anything about this question so I won’t even try to give an answer of this.

Best regards,

Larry