Deep hollowing tools???

[HSS]

I'm after some advice on deep hollowing tools.

Over the last few months I've been trialling various ways of making large scrapers for hollowing a long way over the tool rest (up to about 350mm). My biggest issue has been chatter any deeper than about 100-250mm depending on the tool I'm using.

I've tried the conventional PandN 30mm scraper, old files (5mm thick), 4140 high tensile steel bar (12-35mm diameter) with silver-soldered HSS tips and most recently spring steel flat bar (50x12mm used on end).

I have not had the opportunity to ever use commercially available hollowing systems but how do you guys rate these? I also have not tried forged high carbon tools or hook tools. I will post some photos of my attempts over the next few days.

The chatter is just something I can't seem to get rid of!

[Scott]

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

-Scott

[Skew ChiDAMN!!]

You looked at making Oland tools?

I've no idea whether Hughie is still making/selling his versions (http://www.woodworkforums.com/f8/upgrade-solid-rough-out-tool-85943) but it could be worth your while asking...

[brendan stemp]

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!

[Jim Carroll]

You have 2 options for this depth of hollow forme
Rolly Munro mini with the 5/8" ba (http://www.cws.au.com/shop/item/rolly-munro-hybrid-hollowing-tool)r, this uses the larger bar but with the mini cutters

The other option is the Pro-Forme Flexi (http://www.cws.au.com/shop/item/woodcut-pro-forme-flexi) from Woodcut

Both do a great job.

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

[hughie]

I've no idea whether Hughie is still making/selling his versions (http://www.woodworkforums.com/f8/upgrade-solid-rough-out-tool-85943) 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.

[rsser]

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 (http://www.woodworkforums.com/blogs/rsser/knocking-up-some-tools-84/) . 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

[orraloon]

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

[rsser]

Good jigger John.

What's the shaft diam?

[joe greiner]

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

[INVENTOR]

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.

[rsser]

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 (http://www.cws.au.com/shop/item/woodcut-shepid-irons-toolgate)

[HSS]

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.

[TTIT]

............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.:2tsup: Link to the rig on my website (http://www.ttit.id.au/gadgets/hollower.htm)

[rsser]

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 (http://www.kelton.co.nz/hollower_sets_large.html)

[Ozkaban]

Interesting thread, though I've never tried deep hollowing.

That is one serious looking lathe there. I'm having trouble working out the scale of it, but what is the bed height/length?

Cheers,
Dave

[rsser]

Just as an observation on your tipped tools HSS, you'll get better control the closer the cutting point is to the shaft centreline. You could look at bending a swan neck in one or two of these as well.

And your rectangular scraper (2nd last pic) used narrow side upward, is rather like the Kelton designs.

[hughie]

Yes.

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


Agreed it seems any covered tool has this problem . Although I am doing my darnest to get around the problem.


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

Yep, but very easy to make and if you practice on open bowls first it will be of great help.



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


Found this myself and gave away most of my Chinese M2. Poor HSS is a pet hate of mine.

[RETIRED]

Interesting thread, though I've never tried deep hollowing.

That is one serious looking lathe there. I'm having trouble working out the scale of it, but what is the bed height/length?

Cheers,
DaveWadkin, drool.:D

[Pat]

HSS, could we have more pics of your lathe and some specs?

Any lathe that makes drool, must be good :2tsup:

[Sawdust Maker]

HSS, could we have more pics of your lathe and some specs?

Any lathe that makes drool, must be good :2tsup:

ditto:)
or at least having a closer look at

[Tim the Timber Turner]

Any lathe that makes drool, must be good :2tsup:

:no:Naa that's not right.:no:

:no:You don't need a lathe.:no:

A bit of chocky cake will do.:2tsup:

Cheers

Tim:)

[INVENTOR]

HSS if I read it correctly you have reasonable size opening given that you are only doing 120 diam. which means you don't really need to angle the tool very much and you should be able to overcome the tool twisting action with either 1. an auxiliary handle or 2. use a gated hollowing system
But you do need
1. very small tip tools
2. have the tool rest as close to the opening as possible and/or use a hollowing gate.

From what you have said the pieces are more like 'vases', deep but not very wide. Think of turning inside no different than outside ( in regards to tool tip size) Most turning tools actually only cut on a very small contact area.

My best advice is to have a look at the Kelton web site, as they are one manufacturer that makes hollowers, in various sizes, and a gated hollowing system (that uses the hollowers and a hollowing gate for freehand use. Their ER handles also have a auxiliary side handle.

If you are thinking of using Tungsten tip tools (aluminium style cutters) (like Vermec and others) they can be very 'grabby' unless they are angled correctly and/or guarded, but then they clog. So, scraper type tips are often the best. IMO

By the way, on that lathe you should be able to turn ANYTHING!!! you just need the the right tools.

[orraloon]

Ern,
Mcjings sell the tool unhandled as a ''flat holder and cutter''. It is half round with a flat side. The flat side gives it stability against wanting to torque when hollowing. The half round side makes it good for sheer scrapeing. They have a selection of cutters to fit and I also had some others at home. The others came from a much more expensive tool but work better on this one. At a rough guess the overall shaft diameter is 19mm but I have not measured it.
Regards
John

[joe greiner]

G'day, HSS.

For a cantilever beam of length L, with concentrated load (P) at the tip, the tip deflection is

d = P * L^3 / 3*E*I

E = Modulus of Elasticity (varies with material, ~30,000,000 psi for steel)
I = Moment of Inertia (depends on shape)

For a rectangular bar of width B and depth D,
I = B * D^3 / 12

For a circular bar of diameter D,
I = Pi * D^4 / 64

Cheers,
Joe

[Cliff Rogers]

Good thread. :2tsup:

[NeilS]

I have used the rig below to hollow to 350mm. It's a Munro head on a Hughie 22mm shaft + side handle to resist rotation.

I find I have to go above a 3/4" shaft for that depth/overhang.

The Munro head does tend to clog on green wood. As others have suggested, the Proforme head (Jim stocks them) has a better shaving escape topology for green wood.

I really like hook tools (the type you make yourself from cement nails (http://aroundthewoods.com/hooktool.shtml)) for deep hollowing green end grain. The shavings readily escape the cutter, there being no gate. They are not HSS, so get blunt, but I make and sharpen them in batches and just swap in a new hook when the current one gets blunt. You can also modify the profile to suit yourself. If I was better at tempering them I would stay with them, but I seem to end up making too many of them that are too soft or too brittle. A metal worker would have no problems getting that right.

Some people also re-profile old drills and the like to use as the cutters for deep hollowing.

If you are heading into deep hollowing territory check out this thread (http://www.sawmillcreek.org/showthread.php?141578-Cherry-Log-Vase-Creation-Process&highlight=).

HSS - You are welcome to try the hollower below if you would like to give it a go...

174763....174762

or Hughie's Rip Snorter (I think it has a 1" shaft), if that takes your fancy.

174761
.

[cookie48]

Looking at some of those tools it is a wonder some of you gents do not just go out and get a 25pounder and blow the middle out of the trees you are turning. Honestly tho I have never tried deep turning, but it will happen one day I hope.

[HSS]

Well firstly, sorry about the late response to all your comments, I just haven't got myself organised enough to reply.

Attached are some photos of my lathe and workshop for those that requested it. It's a Wadkin RU 18 (sold to me as an RU 15 but I'm pretty sure it's an 18 as it has an 18'' swing over the bed)

The entire bed winds out on a rack and pinion, increasing the length between centres from approx 2.5m to 3.5m ish. This also creates a gap between the headstock and the bed allowing turning up to 1800 diameter between centres. Outboard turning max's out at just over 2000 diameter. The banjo weighs about 20kg, the free standing tool rest is about 150kg (currently being used as a heavy duty lamp stand), one of the face plates needs 2 people to lift it off the ground (visible behind the lathe). All up it weighs around 1500kg.

It's got a 3hp english electric motor and is geared rather than belt driven. It has 9 gears (100-1900rpm). The major draw backs are that all but the two highest gears are fairly slow, there is no variable speed and the gearbox is pretty noisy at high speed. Also, there is a carriage and tool post which is really invaluable for the work I do. The only problem is when doing short spindle turning, it gets pretty crowded around the headstock, with the banjo, carriage, tailstock and hand tools, all of which are inherently oversized and bulky. It's in mint condition but does require a fair bit of TLC (Inox, oil and grease) to keep the rust at bay and all the moving parts moving how they should.

Anyhow, back to the deep hollowing tools:

I like the look of your deep hollowing jig TTIT, awesome job! I'll think about doing something similar and might look at incorporating my carriage or tailstock somehow. I have a problem with some off-the-shelf accessories due to the 18in swing.

Cheers for the tips about capped tools and the kelton scrapers. I was looking favourabley at the woodcut hollower but I might have to settle for scrapers. After I made those tools I realised how much control you loose due to the torque inherent in having your cutting edge out from the centreline of the shaft (especially on round bar). I tried to counter this by milling a 12mm flat on the underside of the bars but it isn't enough sometimes. I didn't want to take more than 12mm off as I would loose too much meat.

Cheers for the formulas Joe, I'll try and apply these to what I'm doing. I'd like to be a bit more scientific about things!

Neil, I'd love to try out those tools and see how you're set up if that's ok. I'm down in Hindmarsh but I can come up anytime that suits you if that's alright. Likewise, if you're interested in what I'm up to you're welcome to check out the new workshop.

I'll definately try making my own hook tools but tempering I need to work on also, I've only done it once.

Cheers for all the responses,

John.

[Cliff Rogers]

Nice shed. :2tsup:

[RETIRED]

I don't think I had better visit as you would have a real rust problem from all the drool.:D

We had the same problem moving the big rests on smaller jobs so we built a sub bed to fit on the main one and just use our normal banjos.

[NeilS]

Neil, I'd love to try out those tools and see how you're set up if that's ok. I'm down in Hindmarsh but I can come up anytime that suits you if that's alright. Likewise, if you're interested in what I'm up to you're welcome to check out the new workshop.



PM sent.
.

[Sawdust Maker]

Nice shed. :2tsup:

That would be one of the biggest understatements I think I've seen on the forum :2tsup:
but :whs:

[HSS]

Nice solution . I'm also thinking it's probably worth buying a normal lathe with variable speed to do all those smaller jobs on a more manageable platform.

By the way, the workshop isn't all mine, I share it with 3 mates. We've each got our own area from which to run our businesses. We all purchased a few pieces of machinery and pitched in doing the wiring, lighting etc. It meant we could afford good quality gear as we didn't have to buy it all individually. It's all second hand but in good nick and heavy duty.

I attached the handle of my hammer drill to one of the scrapers I was having trouble with and it works a treat. The cutting edge was overhanging a long way from the centreline (noted by Ern) and I just couldn't stop it catching and chattering uncontrollably. By using the additional handle and changing the angle of the tool I'm able to get a much better finish (so far about 150mm over the tool rest).

[RETIRED]

Another lathe is the best solution.

You can also use Vise grips for a handle as well.

[INVENTOR]

HSS, if you like the option of using a side handle ( which I have been using for many years, when working freehand) you will absolutely love using a good quality hollowing rig. While free hand can have some advantages, using a jig is so,so much nicer.
Problem with most (not all) rigs is they are too limited in the way they hold the tools. Grub screws damage shafts and eventually your tool shafts look like the dog with TC teeth has chewed them.

When hollowing freehand on a fixed head lathe you really need to be standing on the otherside of the lathe bed ( with appropriately positioned stop switches etc) BUT with a hollowing rig you can stand in the usual spot and even fit a laser to help tell the thickness.

BUT this is still dependent on the right cutting tools.
I hope this helps:U

PS great set up!

[rsser]

In terms of reducing twisting torque, I mentioned modifying your shaft to make a swan neck, to keep the cutting edge on the main shaft centreline.

You can see what this this might look like if you follow Jim's links on p.1 of the thread.

This is good for oval or acorn shaped hollow forms when you need the 'kink' to clear a narrow entrance.

Inventor is right; grub screws are tedious and can do some damage. The Munro hollower handle however has a phenolic knob which is quick and convenient, and helps you orient your tool so that when hollowing blind you know where your cutting edge is. Obviously this wouldn't be hard to replicate.

Best of luck.

[INVENTOR]

Having the usual bend/s in the shaft and the tip in line with the shaft work, up to a point. When you are hollowing on the sidewalls and under the very top of more of a 'square' or sphere shaped piece then it pretty much goes out the window. As you can't keep the tool rest and tool at the appropriate position/angle.
The answer is some sort of torque arresting.
I have found that when doing 'serious' hollowing ( deep and/or wide in burl etc) you need a lot of purchase on the tool shaft to prevent it from moving in the handle. One screw is not ideal. The best system I have found is the one Kelton uses the ER collets. Particularly now they are using the ER32 on their hollowing rig. A good collet system is the way to go. Compared to grub screws and even drill chucks etc. ( we all know how drill bit shafts look after the drill spins in the chuck)

Like most things it depends on how much you are doing and how serious you are.