Making hollowing tools

[Phil Pascoe]

Unless of course you offset the cutter as Chipmunk has done. It's two tools instead of one I suppose, but if you're using carbide cutters, the main cost is the cutter rather than the rest of the tool.
Your last paragraph sums up what I was getting at - if hex bar were used, would it be a worthwhile compromise? I suppose logically the cost of making the tool is small enough to justify making all combinations of bars and cutters, then keeping the ones that suit best.

 

[CHJ]

I still don't see the need for hex or square bar. Round is much more controllable for getting a better finish. Almost every hollowing tool on the market is round.

Some confusion here on use of the different shaft forms methinks.

Round tool shaft does give angular flexibility for use with tips intended for shear cutting/scraping as a finishing cut, and shielded or ring cutters needing angle of attack adjusting in use.

Square tool shafts come into their own if you use the tips much as I do the majority of the time in plain Boring mode for rapid removal of internal waste and external rough truing and shaping of a blank.

Used for this type of cut external or internal, a square shaft is ideal for tool stability.

 

[finneyb]

Lyle Jamieson a US turner, wood sculptor etc has an article for building your own hollowing rig, if you want to go deeper than say 5". https://www.lylejamieson.com/tools/tool_howto.asp

Site is worth a look around also

Brian

 

[duncanh]

No confusion at all. With a round bar you can control how aggressive a cut you take, whether it be roughing/boring or shear cutting/scraping. A lot of my hollowing is done from start to finish with the Munro tool (because I can take large cuts for roughing and tiny cuts for finishing) but I also use flat cutters (which can also be used as shear scrapers) and toothpick style cutters (either from Sorby or home made from HSS).
If you use a round bar you can vary the cutting angle and roll into the cut, helping to avoid catches. This is particularly useful when inside a closed form where you can't see the cutting tip. Also, if you've done most of the hollowing with a flat scraper on a round bar it's simply a matter of loosening the bolt, rotating it slightly on the tool to then use it as a shear scraper.
Maybe it's just because that's how I first started hollowing, but I've never seen the need to buy square stock when round serves me perfectly well.

The only time I use a square shaft tool is when I rough out a large well out of round log using a 1m long square bar with a square carbide tip.
I have a couple of Sorby tools (RS200? and cranked version) but hardly use them for hollowing anymore (although that's partly because I tend to make larger forms beyond their reach).

I still don't see the need for hex or square bar. Round is much more controllable for getting a better finish. Almost every hollowing tool on the market is round.

Some confusion here on use of the different shaft forms methinks.

Round tool shaft does give angular flexibility for use with tips intended for shear cutting/scraping as a finishing cut, and shielded or ring cutters needing angle of attack adjusting in use.

Square tool shafts come into their own if you use the tips much as I do the majority of the time in plain Boring mode for rapid removal of internal waste and external rough truing and shaping of a blank.

Used for this type of cut external or internal, a square shaft is ideal for tool stability.

 

[graduate_owner]

Another really useful guide. Thanks guys.

K

 

[chipmunk]

Well I have a bit of a confession to make. I have since tried Simon Hope's little 6mm round TCT cutters and have become a real convert.

Simon's are circular TCT positive rake uncoated indexable tooling tips intended for Aluminium mounted with an M2.5 torx screw on a short section of 6mm bar which can be held in the end of a hollowing bar like these.

I bought a bent tip from Simon and then knocked up some straight tipped versions based upon a slightly different cutter tip from APT which woodpig had suggested (https://www.ukworkshop.co.uk/forums/post989253.html#p989253). To make these you need a 6mm end-mill to create a flat bottomed seat centrally in the 6mm rod and then drill and tap an M2.5 hole right through on the same centre. Finally saw, file or machine away the end of the rod to expose the cutting edge. A flat on the 6mm rod makes it easier to mount and unmount without binding in a 6mm hole in your boring/hollowing bar.
I can mount these in some hollowing bars I've made for my Monster knock-off hollowing rig (http://i1298.photobucket.com/albums/ag49/jonathanagibbs/IMG_20150818_194154894_zpssxq3uond.jpg) or a short wooden handle and I also have a couple of mild steel flat stock holders with a 6mm mounting hole so I can use them directly in the Big Brother shaft in place of the HSS tips.

Here are the APT parts references (http://www.shop-apt.co.uk/carbide-tips-hobby-use/pack-of-2-rcgt-0602mo-alu-ak10-carbide-tips.html) and a sharpening gadget comprising a 6mm rod threaded at the end M2.5 so that a diamond file can sharpen the cutter easily as it rotates under power.

HTH
Jon

 

[woodpig]

They don't get much easier to make than these:

http://www.fromthetree.co.uk/hollowing-tools.html

Inexpensive to make as well.