What are the advantages/disadvantages of using larger indexable tool holders?

[pcortes]

I'm not a professional. I've been using an 8x12 lathe for about 10 years, but I just bought a 13x40 lathe and I'm in the process of buying tooling. It came with a 200 series Aloris clone and I want to buy some indexable tool holders. My first thought was to buy the biggest tools that would fit in the holders, because they would presumably be more rigid, but then I started to wonder if there would be any downside. Obviously a larger boring bar wouldn't fit into smaller bores, but are there any disadvantages to larger tools when turning outside diameters?

Thanks for you help.

 

[Clive603]

Obvious disadvantage with larger tool-holders is access when turning stepped components such as bobbin shapes with large ends and smaller centre section.

When doing smaller between centres work a large tool may hit the centre before the job is down to size. Especially with revolving centres. Half centre or interchangeable centre sets with extended point inserts are work arounds but the interchangeable breed aren't exceptionally accurate and half centres sacrifice support for access.

If using smaller tools in larger QC holders make up some sharp edged L fillers to bring the smaller toolholder central under the clamp bolts when tool and filler are firmly pushed to the back of the slot. Sensible to make the bottom of the filler the right thickness to compensate for the difference in tool tip height to tool shank base so that you don't need to futz with toolholder heights when switching insert tools.

[I've always thought that QC systems are a very expensive way of using insert tooling. As the tip to holder base dimension is accurately held a simple slotted block would do just fine and be more rigid to boot. Just needs a quick release clamp and an accurate indexing system underneath so whole block can be changed out complete with tooling. I have about 4 concept sketches for such based around 2 slot blocks that I shall never get round to making.]

Clive

 

[eKretz]

If they fit, there is no disadvantage, only added rigidity. And don't forget you can always use a smaller tool shank in a larger quick change holder. That doesn't work in reverse.

 

[Bill D]

Smaller toolholders tend to use smaller inserts. Smaller inserts tend to be cheaper to buy. Many only use the corners so the rest is wasted.
Check insert price before buying any toolholder. common ones cost less then custom only one maker source inserts.
Bill D

 

[pcortes]

Thanks for your help!

 

[Gordon Heaton]

Clive603 describes the disadvantage. I encounter the problem most often when threading smaller diameter parts. I use laydown inserts in a 1" shank holder and it is bulky enough to interfere with the live center before the cutter contacts the work. And that's with a 1/2" diameter center point. So, for threading at least, I'd adapt a smaller tool to the system.

 

[edwin dirnbeck]

ONE INCH SQUARE tool holder on ebay,over 1200 listings. Almost every style carbide has most listings for 1 inch shank.Most medium cnc lathes have ONE INCH SQUARE SHANKS .Edwin Dirnbeck