How do you like to mount?

[Frank&Earnest]

Unless its large size makes it necessary, I do not like screwing the blank, either to a faceplate or a screw chuck, the main reason being the limitations imposed on the blank because of the need to remove the deep holes of the screws. My preferred method so far was to drill a recess with a Forstner bit (first photo) and mount on the chuck in expansion mode. It never gave me any trouble but it may be a less safe option than a tenon and some people hate this method with a passion, as it emerged in another thread.

Last weekend I saw Tim Skilton cut a groove inside a bowl to reverse mount, and that gave me the idea of drilling a groove around a tenon instead of a recess. This has three advantages: much easier to cut with a hole saw than with a Forstner bit; makes the haters of expansion mounting happy ; and if the tenon fails, the recess for using the expansion mode is still there.

So I made the jig you see below using a 2.5" and a 2" hole saw stacked (the whole set cost me only 12 bucks at the last show, IIRC) which produces a groove wide enough to fit the thickness of the jaws and a tenon of the most effective diametre (about 47mm for the standard jaws of the Supernova 2, but they are all about the same, I think). The other dimension to optimise is the length of the tenon, which has to be equal to the depth of the jaws minus a small clearance to ensure that the blank sits evenly on top of the jaws. In this case about 9mm. This is achieved by removing the central drill and replacing it with a centring point/depth gouge fashioned by sharpening a rod of the appropriate diametre and epoxying a collar around it. After paring off the waste between the cuts the blank is ready for mounting.

Stacking the saws implies that the internal cut is slightly deeper than the outside cut, which does not seem to be a problem. Of course with any drilling method it pays to check with a level that the hole is orthogonal to the surface, which might require sitting an irregular blank on a couple of wedges before drilling.

[Harry72]

Not a bad idea Frank, you'd need a fair amount of torque running two cups at the same time.

Personally I just glue on a block of jarrah with a tennon precut or a block of jarrah with my lathe sized thread tapped into it(Beall Tools tap for nova lathes)

[mkypenturner]

if its under 10 " round and 2" thick i just stick it against the chuck and bring tail stock up and tighten and turn about 1200 rpm and turn a tenon to suit the chuck

[tea lady]

But you've still got the little hole in the middle. Just put it on the screw chuck and be done with it. You don't have to have it going the full depth of the screw. Put a shim of ply on the screw first and face it off flat then screw the blank on. I've only had softer woods strip their thread.

[hughie]

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Just put it on the screw chuck and be done with it. You don't have to have it going the full depth of the screw. Put a shim of ply on the screw first and face it off flat then screw the blank on. I've only had softer woods strip their thread.

Yep thats the way I do it, except my shim is a piece of stainless 3mm plate. I find such a backing plate give support to the screw and prevents any side movement and weakening the screw grip.

[Frank&Earnest]

But you've still got the little hole in the middle. Just put it on the screw chuck and be done with it. You don't have to have it going the full depth of the screw. Put a shim of ply on the screw first and face it off flat then screw the blank on. I've only had softer woods strip their thread.

The hole in the middle is only a couple of mm deeper than the tenon, just enough for the point to protrude into the centre punch when starting the cut. That makes it 11-12 mm total, not enough for holding a decent size unbalanced blank with a single screw. Which was the point, but as I premised it is a matter of preference.

If the choice is between drilling methods I think I could reasonably argue that this is intrinsically the best one, but of course the comparison with any other methods requires the consideration of a lot more variables.

[tea lady]

But You still have to turn all that stuff off the base. Just use a screw chuck or if the blank is really too misshapen screw it to a face plate. Personally I haven't got a drill press, just a hand held drill and I would not be able to drill double holes with a hole cutting saw. And if I manage one, I certainly wouldn't manage a whole stack of them fo ra day's work. You just have a hole with vertical sides anyway, not a true tenon with an undercut dovetail. It will just pop off the first catch or even big decent cut you take. But if it works for you, that's fine. There are many ways to skin a cat.

I have had great success recently mounting my bowl blanks between centers and turning the outside shape including a foot to grip in the chuck in compression mode. This works really well for deep bowls. And for quite misshappen wobbly ones too. Haven't tried it with flatter platter shapes. I also imagine it would be quite easy to cut a slot that way to tak a chuck in expansion mode too, with undercut dovetail and all. Now I have Cole Jaws it a simple matter to make a nice bottom afterwards. This method is really fast. Requires no pre-drilling, and minimal marking of the centers. And I have never had one fly around the shed. (Except if you count that spalted one that was mostly air anyway. )

[Frank&Earnest]

Yes, making the tenon between centres is the easiest solution, the problem I had with it is that big unbalanced blanks keep slipping because the spurs eat the timber away. Also, it needs to be cut away afterwards, it can not be used as the foot unless the bowl is very small, which would make this mount irrelevant anyway. As a minimum this groove allows me to hold the blank between centres better than the spurs, but it would have to be a really big catch to dislodge a properly fitting "vertical" tenon anyway. Or "vertical" recess in expansion mode, for that matters. I am not into turning as an extreme sport.

[oldiephred]

check with a level that the hole is orthogonal to the surface

Don't mean to show my less than average brightness nor to be critical but please explain "orthogonal" and how to check it with a level

[NeilS]

Some production bowl turners (eg Robo Hippy) prefer to cut a recess in the blank for mounting, others like Raffan prefer to use a screw chucks (and shim on shallow blanks as TL and Hughie have described). Some of us continue to use faceplates, while others fiddle around with mounting between centres. Each to their own, but it's always good to have our orthodoxy challenged.

.... I do not like screwing the blank, either to a faceplate or a screw chuck, the main reason being the limitations imposed on the blank because of the need to remove the deep holes of the screws. .

On shallow blanks use shorter, but fatter, screws, and more of them.
Galvo hex headed screws work quite well.
Regular wood screws are too thin and prone to snapping.
May need to drill out faceplate holes to accommodate the thicker gauge screws.
If needed, drill a few extra screw holes in faceplate to increase grip.
Countersink screw holes on blank side to accommodate lifted wood fibre.

Haven't done it myself, but chiseling out the wood between the two hole saw cuts looks like it would be time consuming. Getting the bottom of the rebate flat to evenly seat the jaws would be a challenge, at least for me.... An adaptation of an adjustable hole saw cutter like this might speed up the job. If the top of the blank is flat, power routing is another option.... and a dovetail bit could be used to create the correct dovetail angle. Hmm... this is starting to sound like flat wood work to me...

.....

[tea lady]

If the top of the blank is flat, power routing is another option.... and a dovetail bit could be used to create the correct dovetail angle. Hmm... this is starting to sound like flat wood work to me...

.....

a dovetail bit could be used to create the correct dovetail angle. Now there's a good idea. Could be useful on a big flat platter blank.

[brendan stemp]

Thanks for sharing your idea with us F&E. It certainly has merit but I'm with Tea Lady on this one. A screw chuck is just sooooooo easy. One hole drilled, simple. I have turned up to 500mm using a screw chuck. And I have never had any problems with getting rid of the hole that is made for it.

[Frank&Earnest]

Thanks for sharing your idea with us F&E. It certainly has merit but I'm with Tea Lady on this one. A screw chuck is just sooooooo easy. One hole drilled, simple. I have turned up to 500mm using a screw chuck. And I have never had any problems with getting rid of the hole that is made for it.

I have no doubt that the screw chuck is the easiest solution and works well with deep bowls. Part of the issue will always be what one is more comfortable with, for example I am comfortable with paring the waste, Neil is not (excellent idea the circle cutter Neil, thanks, must try it- it could be more effective than my jig). My limited experience does not allow me to assert with confidence what works better with what, my empirical argument is only that on any blank more than 10" wide and less than 4" thick the depth of the hole necessary to hold it securely is, for my taste, limiting too much my design options.

[Frank&Earnest]

check with a level that the hole is orthogonal to the surface

Don't mean to show my less than average brightness nor to be critical but please explain "orthogonal" and how to check it with a level

Sorry mate, did not want to be a p***k, it's just what one is used to. I meant that the hole has to be at 90 degrees with the top surface of the blank, and because the bottom for example of a half log is round, you have to sit it on the drill press table on some wedges and check with a spirit level that it is reasonably flat.

[Frank&Earnest]

Neil,
by "Galvo hex headed screws work quite well." do you mean the short ones for colorbond fences with the metal cutting point? The roofing ones that go into timber battens are 40-50 mm long, a bit too long IMHO. Or you had something else in mind?

(screwing all those screws in and out seems to me more time consuming than my paring, though... )

It always catches me. Have you noticed that if there is not a space between and ")" the software decides that you meant to put in the icon for ROFL?