Square edged bowl and Cole jaws

[sploo]

I saw Dennis Edwards' square edged bowl video (https://www.youtube.com/watch?v=76CcpwJR5x4) and thought I'd have a go with some pine scrap.

The two halves of the stock below (A and B) are separate; the idea being that you cut the 1/2 circle arcs at 45 degrees, usually on the bandsaw:

For various reasons I instead decided to use my jigsaw. Not a great idea, as a jigsaw is to fine woodworking as a rusty penknife is to heart surgery.

The main problems are that the ring widths need to be the same size as the stock thickness. My stock was only 15mm thick, you lose the width of the blade kerf, and the wandering of the jigsaw meant inaccuracies in the cut. You can see how far "off" the rings are:

Because of those problems I knew I'd need to remove a lot of material to get the rings smooth - meaning the risk of really thin walls. Somehow it all held together (despite a lot of grain tearing). The red hue on the second image is the light bleeding through!

Despite all that, the end result wasn't bad, so I probably should have stopped there - but the idea was to try the square top, so on it went:

Somehow, it all stayed together; albeit the inside surface isn't remotely a flat 45 degree slope. I couldn't risk removing any more material:

Roughly cut off from the waste block to which it was glued, it's... interesting I guess:

To clean up the foot I decided it was time to make some cole jaws. I used 6mm bolts in the rubber door stops, and tapped each (5mm drilled) hole in the MDF. I stabilised the threads with superglue. The plates themselves have Axminster's wood jaw plates (http://www.axminster.co.uk/150mm-wood-jaw-plates-910405) screwed on. Bonus marks for spotting the subtle error in the last image:

It seemed to hold the bowl pretty well:

How thin? Thin:

 

[NazNomad]

... almost too thin in one place? :-D

That looks great.

"A jigsaw is to fine woodworking as a rusty penknife is to heart surgery" - Well, in an emergency, you might be pleased someone has their rusty penknife with them. Better than dying, I suppose?


Seems as though you're not missing that 'thump thump thump' sound in the slightest. :-D

 

[Phil Pascoe]

An added foot, maybe, for some stability? I think it would look better with the corners "Drooped" rather than flat - imho, that's all.

 

[sploo]

... almost too thin in one place? :-D

That looks great.

"A jigsaw is to fine woodworking as a rusty penknife is to heart surgery" - Well, in an emergency, you might be pleased someone has their rusty penknife with them. Better than dying, I suppose?


Seems as though you're not missing that 'thump thump thump' sound in the slightest. :-D

Just a bit! (too thin)

The camera hides a multitude of sins - there are plenty of marks, uneven cutting, and on one side a "gash" where I overcut that ring - but just didn't have enough material left to turn it out.

The jigsaw really is the tool of a traveller, but I was too lazy to change my bandsaw blade for a thin one, and I've currently got a problem with the table tilting mechanism - hence the use of the aforementioned caveman tool.

Given the above, the only thing I'm disappointed with is the fact there was a lot of tear out (and I was keeping my gouge razor sharp throughout). I tend to only see it when I use cheap and nasty pine - which is for learning pieces, so I won't worry too much.

No thumps on this new lathe - other than when I get a catch :wink:

An added foot, maybe, for some stability? I think it would look better with the corners "Drooped" rather than flat - imho, that's all.

I was copying the design in the YouTube link above - but actually it sits quite nicely. The idea is that it will have perfectly flat 45 degree walls - though the original in the video was larger, so the base was ultimately a bigger diameter.

It wouldn't be possible to do the drooped corners with this "economy bowl" technique - as everything comes out of one sheet; so there's no material available to create the drooped corners (unless I cut the droops from the single sheet that forms the top, which would be possible I guess - but it wouldn't overhang the bowl as it couldn't droop by more than the single sheet thickness).

EDIT: typo

 

[Duncan A]

To clean up the foot I decided it was time to make some cole jaws. I used 6mm bolts in the rubber door stops, and tapped each (5mm drilled) hole in the MDF. I stabilised the threads with superglue.

I made some Cole jaw extension plates out of an old HDF tabletop (stronger than MDF) but I used insert nuts from Screwfix rather than tapping out the HDF: http://www.screwfix.com/p/insert-nuts-t ... pack/59937.
I inserted them from the back of the plates so that the metal flange didn't come into contact with the workpiece.
This gives a very secure thread that should last for a long time.

Nice bowl by the way.

Duncan

 

[graduate_owner]

I like the Cole jaws too

K

 

[sploo]

To clean up the foot I decided it was time to make some cole jaws. I used 6mm bolts in the rubber door stops, and tapped each (5mm drilled) hole in the MDF. I stabilised the threads with superglue.

I made some Cole jaw extension plates out of an old HDF tabletop (stronger than MDF) but I used insert nuts from Screwfix rather than tapping out the HDF: http://www.screwfix.com/p/insert-nuts-t ... pack/59937.
I inserted them from the back of the plates so that the metal flange didn't come into contact with the workpiece.
This gives a very secure thread that should last for a long time.

Nice bowl by the way.

Duncan

I do have the threaded inserts, but if I recall correctly there are 88 holes in the design above - which would be quite a few to screw in! They can also chew up MDF quite badly - and I do find they occasionally wander off line when inserting them. I start them off using the drill press (not running, just for alignment) but doing 88 that way would have been really tedious.

I think the tapped threads in the MDF should be OK (as long as I don't accidentally overtighten a bolt). The superglue works surprisingly well - I just squeeze some in, then use a drill driver to quickly wind a bolt in and back out to ensure it covers the whole tapped thread.

 

[Duncan A]

I'll certainly give the superglue a go when doing quick one-offs; it sounds very useful.

 

[Dalboy]

A great exercise. I have made various jigs and use tee nuts

As for the jig saw there is nothing wrong with using one if used for the right job, I use one on a regular basis if only to rough cut shapes before running a router bit around it when making multiple parts.

 

[sploo]

A great exercise. I have made various jigs and use tee nuts

As for the jig saw there is nothing wrong with using one if used for the right job, I use one on a regular basis if only to rough cut shapes before running a router bit around it when making multiple parts.

I do use tee nuts, but for something like Cole jaws I'd be worried about them working free and turning into projectiles - even if glued in.

The jigsaw certainly has its place, but it is definitely a rough cutting tool!

 

[Dalboy]

A great exercise. I have made various jigs and use tee nuts

As for the jig saw there is nothing wrong with using one if used for the right job, I use one on a regular basis if only to rough cut shapes before running a router bit around it when making multiple parts.

I do use tee nuts, but for something like Cole jaws I'd be worried about them working free and turning into projectiles - even if glued in.

The jigsaw certainly has its place, but it is definitely a rough cutting tool!

They will not come free if a thin 1/4" piece of material is put over the top of the nuts preventing them from coming out

 

[selectortone]

I do use tee nuts, but for something like Cole jaws I'd be worried about them working free and turning into projectiles - even if glued in.

Made these last year, use them all the time - still going strong and no hint of the t-nuts working loose. Only wish I'd made them a bit bigger, they will only take up to a 10" bowl. The buttons are inverted rubber instrument case feet I found on ebay - £2.50 for ten (always the big spender me...) :

 

[Phil Pascoe]

These are quite good value if you need any -
http://www.ebay.co.uk/itm/NOVA-Cole-Jaw ... Swo6lWH5eD

 

[sploo]

I do use tee nuts, but for something like Cole jaws I'd be worried about them working free and turning into projectiles - even if glued in.

Made these last year, use them all the time - still going strong and no hint of the t-nuts working loose. Only wish I'd made them a bit bigger, they will only take up to a 10" bowl. The buttons are inverted rubber instrument case feet I found on ebay - £2.50 for ten (always the big spender me...) :

Looks good. I would keep an eye on those t-nuts though; I have had them work loose on other jigs.

 

[selectortone]

.I would keep an eye on those t-nuts though; I have had them work loose on other jigs.

Thanks - I'll keep an eye on them. Yours look great.