Recess Cut

[DIY DAN]

Just been reading an article and it refers to "...mounting a blank on the lathe using a recess cut with a 48 mm Forstner bit."

I'm not familiar with this type of mounting. Can anyone tell me how it works?

DIY DAN

[wood hacker]

Not sure Dan but I would imagine that the are referring to cutting the recess and then holding the blank on a scroll chuck in expansion mode.

cheers
WH

[Skew ChiDAMN!!]

Not sure Dan but I would imagine that the are referring to cutting the recess and then holding the blank on a scroll chuck in expansion mode.

:o

I sincerely hope not!

A recess should be slightly dovetailed to match the jaws when used in expansion mode, to maximise the grip. (This (http://eddiemackinnon.me.uk/turningwood/woodworking/multistar.jpg) diagram will sorta show what I mean.)

The hole from a forstner bit really ain't suitable for this! However, with a deeper hole you can use a doover like the one I've used in this thread: http://www.woodworkforums.com/f8/i-wondering-35261/#post364246

[oldiephred]

I find that if the jaw faces are pressed against the bottom of the recess, the forstner bit hole will suffice on most projects. Some chuck jaws have serrated edges rather than tapered so a hole with parallel sides is very acceptable for them. Softer woods allow the dovetail jaws to grip the sides of parallel holes quite well.

[Sturdee]

However, with a deeper hole you can use a doover like the one I've used in this thread: http://www.woodworkforums.com/f8/i-wondering-35261/#post364246

They are now made and sold by Pops Shed as the Con Chuck. (http://www.popsshed.com.au/Sub_Categories.aspx?cid=42)


Peter.

[artme]

Hello!! The old chestnut.!!

I always do my bowls using the chuck in expansion mode in a VERTICAL sided recess.

Properly done with absolutely vertical walls, an absolutely flat bottom and a decidedly clean and square corner you should have no trouble. The other proviso is that the diametre of th recess must be within a cigarette paper's thickness of the diametre of the closed chuck jaws.

I have a friend with an eneneering background who taught me this method. I have had one failure only and this was due to carelessness on my part.

[corbs]

I mount mine on a tennon in compression mode then clean up the base when I'm finished:)

[oldiephred]

The other proviso is that the diametre of th recess must be within a cigarette paper's thickness of the diametre of the closed chuck jaws.

Not sure why this is important. IMHO the recess dia should be as close as possible to a chuck opening dia. that will result in max. chuck.workpiece contact. This might be fully closed or some other setting depending on the chuck?

[rsser]

Yes, I'm with Sturdee; the only app I'd use a Forstner bit for is as per the Conchuck, ie. top of a natural edge bowl and expand Shark or Spigot jaws into the hole in order first to work the outside.

[artme]

The other proviso is that the diametre of th recess must be within a cigarette paper's thickness of the diametre of the closed chuck jaws.

Not sure why this is important. IMHO the recess dia should be as close as possible to a chuck opening dia. that will result in max. chuck.workpiece contact. This might be fully closed or some other setting depending on the chuck?


Not so Oldie. The only time any chuck I have used have a close to perfect circle is when the jaws are closed. It there fore makes sense to set your recessto the size of the closed chuck jaws.

[Manuka Jock]

Yes, I'm with Sturdee; the only app I'd use a Forstner bit for is as per the Conchuck, ie. top of a natural edge bowl and expand Shark or Spigot jaws into the hole in order first to work the outside.
Yep , and bring up the tailstock just for good measure .

[orraloon]

The expansion chuck by Bruce Leadbetter works with a shallow recess and comes with its own cutter. I use it more than the nova as it is so easy to do the recess. It is also a shallower recess than required for the nova jaws so saves a bit of wood also. I think Record lathes used to have something similar.
Regards
John

[rsser]

FWIW I'm not a fan of Nova jaws in general; most are rounded over slightly on the outside of the face and the Spigot jaws are chamfered on the outside, so for expansion purposes you're losing contact area.

This issue has been thoroughly thrashed out in an earlier thread, and folk have made chuck expansion mounts work for them in a variety of ways.

IMO still the best way is to use quality dovetail jaws, match the recess angle to the dovetail angle and so you have a keyed fit, not a plain pressure fit.

...

MJ, we tested the Conchuck not so long ago on a hefty lump of Elm, unsupported by the tailstock (cost it overhung the bed on the swivel head) and it held well. So Con (and Skew) are on the ball with this. That said, it has limitations with a nat edge bowl, as do shark jaws cos you can't reposition the lump the align the high points or the low points.

[joe greiner]

Please think about it for a second or two. The hole can't be the same as the fully compressed jaws, or it would be impossible to insert into the hole. AFAICT, the "normal" way of making jaws is to turn round, and then slit into four parts. The width of the cutter establishes the "perfect" diameter, and enables further compression for insertion. I suppose that could be the thickness of a cigarette paper at the periphery, but not the gap in the jaws - more like 1-2 mm for the slitter. Measure your jaws with dial or vernier calipers, across opposing corners and across opposing middles, and adjust the opening until both measurements are the same, to find the correct setting for complete contact; which may or may not be 48mm - YMMV.

And I think it's generally better to seat the workpiece at the shoulders instead of the tips of the jaws, because the shoulders are larger. If the hole is slightly deeper, the tips can more easily (and gently) penetrate the wood.

Aside from all that, I'm with artme.

Cheers,
Joe

[NeilS]

I used the Forstner bit method for many years. It works quite well. More recently I've swung back to using faceplates and rings, not because the Forstner method wasn't working for me, I just find screwing a faceplate or ring on and off quicker.

Robo Hippy, who probably turns more bowls in a year than anyone else on this forum, uses and prefers the Forstner bit method. See his comments in this (http://www.woodworkforums.com/f8/how-do-you-like-mount-118701/) thread.
.

[RETIRED]

Joe. The face of the jaws is the main "register" in woodturning chucks.

It is to ensure that you have the most support for the piece with little "leverage" effect.

[joe greiner]

Joe. The face of the jaws is the main "register" in woodturning chucks.

It is to ensure that you have the most support for the piece with little "leverage" effect.
True enough for compression mode on a tenon. For expansion, I'm not so sure. If the outside isn't flat and parallel to the bottom of the hole, shallow would be better, and I stand corrected. However, if they are parallel, the outside shoulders (nomenclature?) provides more support, i.e. a larger radius.

Cheers,
Joe

[oldiephred]

Don't want to overly dwell on this issue but maybe my thoughts were misunderstood. If one cares to look at the Barracuda2 lathe chuck system site it can be seen that the jaw design is not tapered. I have one of these and find it excellent for recesses where it is not easy to get the right taper. The dovetail type are only as good as the ability to make an angle that matches the chuck jaws. Will now back out of this informative discussion.

[Manuka Jock]

MJ, we tested the Conchuck not so long ago on a hefty lump of Elm, unsupported by the tailstock (cost it overhung the bed on the swivel head) and it held well. So Con (and Skew) are on the ball with this. That said, it has limitations with a nat edge bowl, as do shark jaws cos you can't reposition the lump the align the high points or the low points.

Ern,
I made no mention of a conchuck , you did .
You also spoke of shark and spigot jaws . It is with those , being used in expansion mode in recesses made with forstner bits that I advocate the use of tailstock support for irregular blanks etc. , when possible .
That is what the thread is about is it not .

[Skew ChiDAMN!!]

They are now made and sold by Pops Shed as the Con Chuck. (http://www.popsshed.com.au/Sub_Categories.aspx?cid=42)

Thanks, Peter. I've had mine literally for years, having bought them off Con. I lost his contact details (and forgot his name) so it's good to know they're still available. :2tsup:


Ern,
You also spoke of shark and spigot jaws . It is with those , being used in expansion mode in recesses made with forstner bits that I advocate the use of tailstock support for irregular blanks etc. , when possible .

He also specified a 48mm forstner bit, which to my mind more or less rules out spigot jaws; they're usually a much smaller dia.

Shark jaws would work, but whenever I've had a piece of wood which needs their grip, it also needs to be tightened pretty heavily... which is something I dislike doing in expansion mode. Any natural fault in the wood and... "KERPLUNK" :doh:

Personally, I'm of the school of thought that expansion mode is usually a "second best" form of mounting. Different horses for different courses, I guess. :shrug:

[rsser]

Andy, not sure what you mean by spigot jaws. Have assumed just the Nova equivalent of the Shark Jaws.

My small set of Shark Jaws are 45mm OD so they'd work fine in a 48mm hole. In the past I've just drilled 2" with Forstner bit.

But, they only extend 27mm so to avoid the jaw mount flanges fouling a wave or bit of bark in a natural edge top a bench chisel has to come out to chip away some bark and sapwood in order to get the jaws well in and the faces against the hole bottom.

This is where the ConChuck works better. No flanges so just drill, insert and tighten. And there's a decent length to hold.

So have we heard again from the original poster or have we scared him off? ;-}

There's two kinds of mounting we've been talking about, bowl blank top and bowl bottom once the outside's been shaped. Bit of difference there.

[Manuka Jock]

Personally, I'm of the school of thought that expansion mode is usually a "second best" form of mounting. Different horses for different courses, I guess. :shrug:
I'm of that mind too .
For me , expansion modes , and woodworm screws , with the tailstock brought into play there too , are for holding 'natural' blanks untill a tenon has been cut for jaws used in compression mode .
And even then if the chunk is way out of balance I used the tailstock there too .
Outboard , I use faceplates with long screws in the first stage .

[Skew ChiDAMN!!]

Andy, not sure what you mean by spigot jaws. Have assumed just the Nova equivalent of the Shark Jaws.

Sorry, I had a bit of a brain fart there. :doh: I was actually thinking of pin jaws, not spigot. :B

[rsser]

Ah, k, that explains it. So many widgets, so many names, so little time ;-}

Re expanding dovetail jaws into a bowl bottom recess, it's worked fine for pro turners like Terry Martin and Richard Raffan. Even recesses of just a few mm deep on wide pieces.

It's been my std method and since getting quality dovetail jaws & chuck I've never had a failure.

It does impose design and aesthetic limitations though which were canvassed in the earlier thread on this.

Where those don't apply there's an efficiency bonus .... you can shape and finish a bowl or platter outside and don't have to remount to clean up a foot.

Only if you accept the design limitation of a spigot foot closely matched to near closed jaws in compression mode can you get the same bonus with a clamp mount.

[ravna]

So have we heard again from the original poster or have we scared him off? ;-}

.
Yeah...he's gone very quiet, which is sad because he was/is a newbie looking for info and not here to start a hissing comp. Interesting to note a lot of posters preface their arguments with 'I always'....well I always stand up to pee, but then I only represent about 50% of the population....however, on to the real question....I have read and re-read the posts and find everyone jumping in to say 'i always use this or that, and it's the only way to go'...OK fine, whatever works for you ,go with it, but don't shove it down our throats as THE WAY.
I always (sic) used to use a faceplate and then went on to use a pin chuck but had too many failures....but I think the point everyone is missing (and feel free to shoot) is that the guy was trying to find out how to mount a blank prior to turning the outside and a foot....be it an internal dovetail recess or an external spigot, and in this case I have to go with Ern and the ConChuck although until now I had never heard of it.
The poor guy is probably running off into the woods now yelling 'all woodturners are wankers'.

Cheers
John M

[Manuka Jock]

Yeah...he's gone very quiet, which is sad because he was/is a newbie looking for info and not here to start a hissing comp. Interesting to note a lot of posters preface their arguments with 'I always'....well I always stand up to pee, but then I only represent about 50% of the population....however, on to the real question....I have read and re-read the posts and find everyone jumping in to say 'i always use this or that, and it's the only way to go'...OK fine, whatever works for you ,go with it, but don't shove it down our throats as THE WAY.
I always (sic) used to use a faceplate and then went on to use a pin chuck but had too many failures....but I think the point everyone is missing (and feel free to shoot) is that the guy was trying to find out how to mount a blank prior to turning the outside and a foot....be it an internal dovetail recess or an external spigot, and in this case I have to go with Ern and the ConChuck although until now I had never heard of it.
The poor guy is probably running off into the woods now yelling 'all woodturners are wankers'.

Cheers
John M

???

[rsser]

Yes John M, quite right.

As they say opinions are like ar*seholes; everyone has one. Everyone's works for them but mostly we don't provide enough contextual info that would help to explain why.

And there are a great many variables in the work of producing a piece of woodturning.

Oddly, expert turners are often the hardest to learn from, cos they're in the realm of 'unconscious competence' and while they can describe what they do, they may struggle to explain why they do it that way.

But to be fair to the forum, the original post was not that clear about the context either. There's a skill, and some courtesy, in explaining with this medium of communication what it is you are wanting to know or what kind of help you need with what you're struggling with.

[RETIRED]

Yeah...he's gone very quiet, which is sad because he was/is a newbie looking for info and not here to start a hissing comp. Interesting to note a lot of posters preface their arguments with 'I always'....well I always stand up to pee, but then I only represent about 50% of the population....however, on to the real question....I have read and re-read the posts and find everyone jumping in to say 'i always use this or that, and it's the only way to go'...OK fine, whatever works for you ,go with it, but don't shove it down our throats as THE WAY.
I always (sic) used to use a faceplate and then went on to use a pin chuck but had too many failures....but I think the point everyone is missing (and feel free to shoot) is that the guy was trying to find out how to mount a blank prior to turning the outside and a foot....be it an internal dovetail recess or an external spigot, and in this case I have to go with Ern and the ConChuck although until now I had never heard of it.
The poor guy is probably running off into the woods now yelling 'all woodturners are wankers'.

Cheers
John MActually DIY Dan has been here longer than you.:wink: He only gets on occasionally.

[ravna]

Yeah, I realise that ...it was not meant to denigrate....I made the fatal mistake of

assuming something...I.E. he was maybe new to turning.

As Ern said, 'there's a lot of skill and courtesy required' when offering replies or opinions to

questions, no matter how they are couched.

Cheers

John M

[rsser]

Well if he's been reading these posts and decided not to jump in and clarify his problem, I take that amiss.

Good forums are a kind of conversation, and that implies reciprocity, however minor that might be.

When someone posts a query, gets some replies but doesn't come back with at least an acknowledgement, they get added to my ignore list. Example: Hen on turning plates.

So yeah, I'm getting old and grumpy in my reactions to minor discourtesies.

Of course the web is for the most part anonymous and distant and I can see why folk would go fishing and not bother with the obligations entailed in even minor social interactions.

[RETIRED]

Give him a go. It was posted 2 days ago and he is probably digesting all the info.:cool:

[robo hippy]

Lots of info to digest.

I thought every one knew that all woodturners are some what wankers.

The forstner bit recess does work well, and I have done thousands of bowls that way (turning time is way down now ever since Arthur (itis) stopped in for a visit, and didn't leave. If you are nervous about a forstner bit recess, you can use the tailstock which will make sure the bowl blank doesn't leave the chuck, and then remove it when it is time to make a tenon or recess for the bottom of the bowl. Like any recess or tenon, you do not want the bowl to bottom out on the face of the chuck. Recess diameter holds best if it is within 1/8 inch or so of the chuck jaw diameter (for a 2 inch closed jaw measure, you want 2 1/8 inch diameter recess). You can get away with a bit more, but not for heavy roughing or coring cuts.

robo hippy

[artme]

I don't use a Forstner bit to cut my recess - I don't have one.:no:

I use a parting tool and a scraper or skew.

[old pete]

Hi DIY Dan,

Just read the first post from Artme and forget the rest. I think it is OK however to cut the recess up to two or three mm greater in dia. than the fully contracted dia. of the scroll chuck.

Cheers Old Pete

[Manuka Jock]

I don't use a Forstner bit to cut my recess - I don't have one.:no:

I use a prting tool and a scraper or skew.
Art ,
do you use a steel hammer or a wooden mallet with your chisels when you carve out the recess ? :D


Seriously , my take on the query in the opening post is that it is regarding the initial mounting of a blank on lathe, and therefore a drill and bit , either in a press or handheld would be used to cut the recess.

[rsser]

, fair 'nuff.

He's a low user of the forum (178 posts in 4 years).

Assuming he accepted the default forum settings he may have read Woodhacker's post (a good one IMO), felt it didn't address his concern and not tuned into the thread.

Or he may have gone on holiday after posting his query.

He's not on my ignore list.

....

As for creating a recess in the bowl bottom with a saw-tooth bit, it's not my cuppa tea.

My 2" bit has a point 6mm higher than the rim.

So assuming a recess depth of 4mm, if I wanted to turn that point mark away and leave some thickness at the bottom of the bowl there'd have to be at least half an inch between the bowl bottom and base which with my kind of bowls would be fugly.

[artme]

Art ,
do you use a steel hammer or a wooden mallet with your chisels when you carve out the recess ? :D


Seriously , my take on the query in the opening post is that it is regarding the initial mounting of a blank on lathe, and therefore a drill and bit , either in a press or handheld would be used to cut the recess.

Steam hammer and cold chisel MJ. Just love the hiss of steam!:q

Take your point mate, but my post was in relation to Skew's post.

Seems this will forever be a "point of discussion" amongst turners.:wink:

[rsser]

For anyone with the stamina left to explore the issues about bowl bottom expansion mounting, here's the earlier thread. Click (http://www.woodworkforums.com/f8/aust-wood-review-article-bowl-mounting-114344/)

[DIY DAN]

, fair 'nuff.

He's a low user of the forum (178 posts in 4 years).

Assuming he accepted the default forum settings he may have read Woodhacker's post (a good one IMO), felt it didn't address his concern and not tuned into the thread.

Or he may have gone on holiday after posting his query.

He's not on my ignore list.

....
Quite right rsser. I've been away for a couple of days. Didn't expect 36 replies though. I've gone through them all and learned a bit, (despite the jargon).
I'm not an experienced turner, but have done quite a bit of it, although still got a long way to go. Being up in Blackheath it's hard to get all the latest gadgets for turning, so I'll probably have more questions in the future.
Thanks to everyone for the info.

DIY DAN

[Alastair]

G'day all,

Thought I would weigh into this one belatedly.
Not going to belabour the eternal arguments regarding expansion/contraction dovetail vs parallel etc, but just some bits, which seem not to have been cleared up.

Most of the modern chucks, (Nova, Vicmark, and the various clones) have their "perfect circle" diameter, roughly in the middle of the opening range, BOTH FOR EXPANSION AND CONTRACTION. eg, old time original Nova has expansion 50-60mm, as I recall, with perfect circle 55mm. Figures for contraction are ~45mm - 55mm, PC 50mm.
Obviously targeting PC for most secure hold in either mode.

Regarding depth, in expansion, the face of the jaws MUST register on the bottom of the recess. In fact recess should never be deeper than jaws for proper registration, and should be dovetailed. Can be much shallower, see below.

In contraction onto a tenon, tenon should be parallel, and as long as poss, but not so as to "bottom out". Jaws should register against a shoulder on the tenon. This gives wider diameter registration, and hence a longer "lever" for stability. I don't doubt that apart from accurate registration, the differences are small, and probably only really matter when you are using regular jaws to do a job more suited to power or shark jaws, which I am often guilty of!

Most of this from chuck specs, with a bit of personal exp thrown in.

Regarding Forstner recesses, I find that in all but 1 instance, they hold no advantage, and several disadvantages:
Multiple operations, whether on tailstock, or drillpress.
Slightly less secure hold, unless you get deformation in soft timber.
Bottom of recess has dimple, and requires futher work anyway, unless you intend to turn it off.
Exception is green turnings, after drying, when the recess "ovals" out., and you can't get the jaws to fit in. In general, I just make the original recess oversize, and grip well enough in the oval recess, to allow me to remount and reverse for returning.

Regarding depth of recess, I am one who uses them as a feature of the base. As such, I make them as shallow as possible, and finish to the same standard as the piece.
In sound timber, I will seldom exceed a 2-3mm recess, up to maybe 10", and rarely get up to 5mm, even for pieces up to 24". I have had major problems only twice, both on heavily spalted timber. I have occaionally had pieces let go, but only after disastrous digins, which trashed the piece anyway. Solution is to pay attention when turning!

Finally a pearl of wisdom I have found out the hard way........

If you are using the old style Nova in compression, and doing interrupted turning, (eg rounding down irregular blanks on Glaser screw, winged bowls, natural edge, etc), be aware that the tap-tapping of the interrupted cut acts like a rattle gun, and loosens the scroll, when in compression. Frequently, when I find I'm making a mess of shaping the outside of a bowl, I stop the lathe to find the Glaser screw has sneakily become loose in the jaws, and the blank is no longer running true.

In expansion of course, it only serves to tighten the grip.:D

regards

[NeilS]

Bottom of recess has dimple, and requires further work anyway, unless you intend to turn it off.


Alastair, most of us who have used the Forstner method have applied it to the top of the blank (the side that is hollowed out) and not the foot.
.

[artme]

Good post Alastair!!:2tsup::2tsup::)

[rsser]

Thanks Alastair; good info.

FWIW, the getting close to a circle in either expansion or clamp mode has never been a priority for me but can see if you didn't want to remount after clamping then it's useful.

With my small and medium VM100 Shark Jaws the ID appears to be closest to a circle just a bit wider than fully closed.

So presumably they were machined first as a collar/flange unit and then cut into quarters.

Another tip that may be useful to newbies is to check tightness as you go with any green or soft woods, esp in clamp mode. Cos fibre compression can increase as you turn, then you wonder whether you've lost any skill that you ever had, then the piece gets levered out of the chuck and your confidence takes a dive.

[robo hippy]

I would not use the forstner bit for the bottom of the bowl recess. Just not accurate enough. On a drill press, especially if the bit is getting a bit dull, it will tend to drift a bit. If you are using a freshly sharpened bit, in a jacobs chuck (tailstock mount) at slow speeds, you could be fairly accurate, but you would have to mount the blank on a face plate or some thing, which would defeat the whole purpose of saving time.

I have also found over the years that grain alignment on your chuck, in flat grain/bowl orientation makes a difference. You want the grain to be at a 45 degree angle to the chuck jaws. You do not want one set of jaws to be on the end grain, and the other to be on the side grain. Very little compression on the end grain, and a lot on the side grain, especially if the wood is green. Of course, as said before, if the wood is really wet, it doesn't hurt to check your grip as you turn, and tighten up again as needed.

robo hippy

[Alastair]

Alastair, most of us who have used the Forstner method have applied it to the top of the blank (the side that is hollowed out) and not the foot.
.

Makes sense now, Neil:-

Didn't think of that, since I have always used Glaser screw for primary mount For NE, mount between centres @ slow speed, adjust orientation, and turn a small flat surface, before removing and drilling hole for Glaser.

regards.