Thread: Deep hollowing tools???

Would be interested in the answer to this as well. Same problem.

-Scott

You looked at making Oland tools?

I've no idea whether Hughie is still making/selling his versions but it could be worth your while asking...

This really is a can-of-worms issue. In deep hollowing terms 350mm is very deep and needs some serious consideration.

Most commercially available deep hollowers use a scraping action which is the most aggressive way of taking wood off. Consequently you should have only a small cutter doing the work. I would suggest anything over 6mm is too big and would recommend a cutter width of about 3-4mm.

A lot of d/h are now using a system that 'captures' the shaft of the tool so that the forces on the operators end are reduced and manageable. Vermac make such a tool as an example. However they are still using scrapers and, another important consideration, reasonably thick shafts. I'm not sure on the physics of all this but the increase in forces on the tool as it hangs further and further over the tool rest must be exponential so the increase in shaft size to cope with this (and avoid chatter) must be similar.

The Rolly Munroe and Woodcut deep hollowers are the only d/h I know of that use a cutiing/slicing action. This will help considerably in reducing chatter. Recently at the Sydney Wood Show I saw a turner hollowing a 450mm (approx) deep vase with the Woodcut tool and a very long handle (approx 1000mm). This worked very well.

Another aid is a tool rest that can be poked into the opening of the vase reducing the amount of overhang on the tool rest. I think this style of tool rest is called an Irons Tool Rest.

I saw the Canadian Brian McEvoy demonstrate at Turnfest his deep hollowing tool which had a 50mm thick solid bar that was about 2metres long as the main shaft, reduced in size where the cutter was positioned. The only problem with this tool is that it needed a very elaborate system to prevent the torque forces on the shaft. However it is a very effective system if your serious about deep hollowing.

So, to reduce chatter when deeeeeeep hollowing you need to have a small cutter and a thick shaft or a tool that cuts/slices the wood off. And a bloody long handle!

You have 2 options for this depth of hollow forme
Rolly Munro mini with the 5/8" bar, this uses the larger bar but with the mini cutters

The other option is the Pro-Forme Flexi from Woodcut

Both do a great job.

If going any deeper then there is larger versions of both tools

I've no idea whether Hughie is still making/selling his versions but it could be worth your while asking

Yep got a few in stock right through the range I 've got foam covered stainless handle 500mm long that will take the Junior and Senior with out a hassle. With the Ripsnorter I find that given more serious nature its better the individual turner makes his own.

As to deep hollowing look at supporting the tool inside the hollow vessel as far as you able. This greatly lessen any vibration and cut down on the weight and heavy bar requirements.

On a good day with a hand-held scraper 3/8 thick I can get down to 100mm before control goes out the window (ADDED: see note below). Talking about end-grain hollowing and just working a small part of the edge.

I like the Woodcut Proforme cutting head a lot but the std shaft is only 5/8 and just not long enough. (My first attempt at fitting a head to my own 5/8 shaft can be seen here . Not that difficult.)

So I moved up to a 3/4 shaft. See Hughie's comment in that thread.

Brendan and Skew have it though; the longer the overhang the smaller the cut you can take so folk often end up with small scrapers or Oland-type tips.

For 25 cm or more in my book you need the shaft held for you. There are articulated arms out there (see Elbo or Vicmarc) and captive rigs (see Vermec and many others).

There are other variables too, partic. the density and grain regularity of what you're trying to hollow. Knotty woods will make life hard; dense woods will make life long.

Just to add, Vermec are now making a capped ring cutter. Dunno their std shaft size though.

HTH.

PS: this is with pencil jars where you have to stay on the centre line

I would love to get a captured hollowing rig set up but the dollars are rather big. In the meantime I get by with the big handle on a McJings bar that can take any sort of cutter you can fit on. I have done 6'' deep no problem and reckon it would do a bit more. I use a forstner bit and brill to depth then widen out the hole. The deeper I go the smaller cutter I use.
Regards
John

Good jigger John.

What's the shaft diam?

Tip deflection varies with the cube of the overhang length, not exponential. Stiffness (the denominator) varies with the square of the shaft thickness (rectangular) and linear with the width; or the fourth power of the diameter (round shaft). So, for best reduction of chatter, use the shortest possible overhang, and the largest possible shaft thickness.

Minimizing the cutter size will also reduce chatter. I use 1/8" cutters in my DIY Oland tools with 1/2-inch round shafts. Deepest I've gone was about 8" without adventure in magnolia. For off-axis cutting, I use a vise-grip pliers on the shaft as a handle to help resist torque. Almost catch-proof too, but not idiot-proof.

Cheers,
Joe

HSS, unlike Jim's comment. you have more than 2 options. There are numerous tools available on the market.
You don't mention how wide the opening is? And how large the diameter is? Also, is it freehand or gated.
We can only assume that you are stopping the lathe ( all the time) to clear the shavings/chips?

If the opening is extremely small,( relative to the depth) then your options are limited. As the rules that Joe mentions very much come into play. I usually work on a 8-10 rule. For very small openings 8-10 times the shaft diameter for depth. Using a very small tip, compared to shaft diam.

As the opening size widens, then have you considered using a hollowing gate?To extend the tool support further into the piece.
You might find that scraper type tools produce chips rather than shavings. this can be a good thing as they don't clog up as much and restrict the tool.
We need more info to answer your questions.

Yes, if your opening is big enough you can swivel in an Iron's tool gate. This buys you a bit more depth but it's primary purpose is to steady the tool laterally.

Click

Firstly, thanks for all the advice. Over the last couple of days I've been looking up all your recommendations on you tube and have a fair idea of what's on the market.

Attached are some photos of the tools I've alrerady made.

To answer some of you're questions, I am turning wet cherry end grain, off-axis, freehand (although I've tried using the tool post and carriage on my lathe to hold various tools). My opening is usually about 50mm and the diam varies between 70 and 120. This opening size means I cna't really get a toolrest inside (especially as my tool rest is quite large).

On certain shapes I cut from both ends and re join the ends to create the vessel. And yes, I am stopping the lathe regularly to clear the chips.

I usually start my boring a hole using a spade or auger bit held in the tail stock. I then use a large file (serations ground off and end sharpened) to widen the hole. I then change to scrapers to achieve the final shape. I need a good finish off the tool as the wood is green and can not be sanded.

I definately need to reduce the size of my cutting tip.

I'll have to check out the M42 steel as recommended by hughie, so far I've just used M2 bought of ebay (chinese).

I like the idea of the slicing action from the woodcut and rolly munro tools. I viewed a number of 'hook' tools that used the same cutting action and they looked to cut very nicely. I will also have to look into an irons gate or captive ring.

In regards to articulated arms, they look good but I'd want to test one out first for ease of movement and rigidity before investing. I saw an demo of a Kobra system on you tube that looked pretty good.

Using a lateral handle to reduce the effect of torqu is also a good innovation. to deal with this at the moment I tilt/roll the tool over to the left to about 45 or 60 degrees sometimes. This reduces the aggressiveness of thge cut but also the efficiency.

Joe Greiner, I'm a little confused by your formulas, are you able to show an example?

Anyway, check out the photos!

Photo 1- 4140 high tensile steel bars (12mm-25mm) and M2 HSS tips (silver soldered)

Photo 2- close up of HSS tips (note large surface area-good upto around 100mm)

Photo 3- old files, serrations ground off and sharpened (long square section file [fa right] is used for widening inital spade bit hole. Others are used for finishing.

Photo 4- close up of file tips (note wide surface area. Only the long square section file with a small tip is good at depth but still catches sometimes due to short handle).

Photo 5- 2 files yet to be converted into scrapers [far left] (I've got high hopes for the rigidity of the triangular section file)

PandN scraper [3rd from left] ok at shallow depth

Small boring bar and small HSS tip [3rd fromn right] (excellent when used in tool rest but limited in freedom of movement and depth

12mmx55mm spring steel DIY boring bar [2nd from right] good when used in tool post but does deflect beyond 200mm deep, limited in freedom of movement due to being held in tool post

15mmx50mm steel bar (grade unknown) with HSS tip [far right]. Works excellent in tool post on the outside of a piece but the cutter holder is too bulky to fit inside a vessel.

Photo 6- photo of lathe to show carriage. Note the american style tool post laying down on the box at the back of the lathe. this tool post slides into the top of the carriage and the top screw fastens the boring bar. The carriage has lateral and longitudinal movement and can be rotated and locked into a specific angle.

I hope you find these images of interest.

Cheers,

John.

Originally Posted by HSS

............In regards to articulated arms, they look good but I'd want to test one out first for ease of movement and rigidity before investing. ........

By the look of the tools you've made I'm guessing you're not scared to muck around with a bit of steel so why not put an articulated rig together yourself like I did. It has some benefits over the commercial varieties and cost SFA to make. I use the Woodcut Proforme on it most of the time but also have a couple of scraper tips I can attach to it for cleaning up. Link to the rig on my website

Yes.

And with green timber the capped cutting tools are somewhat prone to clogging. Promforme less so than Munro.

The Martel hook tool would be better but that's one that cutting blind with would be living dangerously or require a lot of practice.

If you were in Melb. you'd be welcome to come around and try the Proforme on the end of a Vicmarc hollowing tool rest. That rig is bearing mounted and there's so little resistance to movement it feels weird when you're coming from hand-gripped tools.

And as an aside, Chinese M2 can vary quite a bit in quality. Something of a lottery.

Another option I don't think has been mentioned is the Kelton deep hollowers. Scrapers in action, hand or rig mounted. They were my introduction to deep hollowing and worked well; come in a range of shapes and sizes.

kelton Industries Large Hollower Sets