Templates for bowls feet using Vicmarc chucks.

[artful bodger]

Recently purchased various sets of jaws for my vm100 and vm120 chucks.
Maybe it is just me?, however I find the measurements they give you in the booklet for when the chuck is at a perfect circle rather ambiguous.
DSCF5612.jpg For instance the 33mm in the picture is given where the foot hits the body of the bowl (black arrow). That makes a fairly awkward place to measure precisely. If I was me, I'd much prefer to measure across the base of the foot (green arrow) with a simple ruler.
As I hope to make lots of various sized bowls I decided to make some templates for future use to make things a bit simpler.
This is the result, a mock foot that best fits each set of jaws. There are 2 mock feet on each bit of wood.
DSCF5620.jpgDSCF5619.jpg DSCF5618.jpgEach foot is marked to show which jaws it suits.

DSCF5607.jpgNot all the jaws have the same angle on them and some are deeper than others.
DSCF5610.jpgAlso checked each one to make sure it was the optimum fit to avoid bruising on the feet.
The aim of the project was to have these templates/mock feet, readily available and handy when turning a bowl. Sometimes an apparently nice big bowl blank can disappoint with unseen defects and thus reduce in estimated size, the foot size generally follows suit. I am hoping having these will reduce going to the booklet and trying to figure out which set of jaws and what the exact foot size will be. Also as an aid when making a run of various sized bowls.
Hope that all makes sense.

[Woodturnerjosh]

That's a fantastic idea!
With regards to the angles, do you find that all the dovetail jaws are the same but different to all the shark jaws? Or was there a variance between all of them?

Cheers

Josh

[artful bodger]

Noticed the larger jaw I had for VM120 had an angle of 10 degrees compared to the smaller VM 100 jaws which seemed to be closer to 7.5 degrees. Putting my head on the chopping block here but that is what my protractor said.

[smiife]

Hi AB ,
It seems after my recent disaster that the tenon
shape , angle and excact measurement is of great
Importance , i have certainly been trying to get a good
better fit than before.............
So a pattern for a tenon is a great idea.....
How do you use them on say a bottom of a bowl
with a tenon ?

[artful bodger]

They are really only for working out what size to make the foot/tennon. The vicmarc jaws seem to be made to hold a foot of a specific size with little room for error. So far I have 8 possible sizes the foot can be. So when turning a foot I have these 8 mock feet that can be held back to back with the bottom of the bowl so the best of the 8 sizes can be chosen to suit the bowl.
I hope that it will make it easier than referring to the vicmarc booklet, then reading a dimension that is ambiguous to make the foot. These templates have the correct size of the bottom of the foot marked on them (shown by green arrow in the original post). I suppose now that I have made them and know what each individual size is, it might just be as easy to write the sizes on the wall behind the lathe with the correct angle. However without making them in the first place the correct size of where the green arrow points is not as certain.
I was giving it a bit more thought today and realised it would be an even better idea to have had a small nail/brad in the dead centre of each template. That way when you are about to turn the foot of your bowl you could make a small hole in the centre of the base of spinning bowl with a pair of dividers, bradawl etc. Then locate the nail from the base of the template into the hole to quickly mark the exact size you need. If the foot looks too small just pick up the next one and mark that, or vice versa to go smaller.
Hope that makes sense Smife, would no doubt be easier to show you what I mean in the workshop with everything in front of us to see.

[smiife]

Hi AB , now you have me thinking ..........
What about a piece of mdf/ply with the female fit....
If you know what i mean , the excact fit to slip
over the jaws or in the jaws , while cutting the
tenon /recess you could test fit as you go!

[Woodturnerjosh]

I'll have to check mine to see how much they vary now!
I do have a pointed scraper ground to the angle of the standard Vicmarc dovetail jaws for my VM120's so as long the face that the jaw buts up against is at 90 degrees to the axis I know the angle is correct. I haven't checked if that angle is the same on my shark jaws and VM100 jaws though.

I love the idea of using a pin in the middle too!

[artful bodger]

I suppose my main issue in all of this is the dimensions of a perfect circle Vicmarc give you in the booklet for all the various jaws. They give the dimension at the easiest part of the jaws to measure. However the easiest part of the jaws to measure just happens to be the hardest part of the foot/tennon to measure. That bit where the foot meets the bowl (black arrow in original post). I am not trying to heap pooh on Vicmarc, so far I am really happy with the chucks I have purchased. However each set of jaws has pretty strict limitations/tollerances to the size of the ideal foot that will fit those particular jaws in the clamp mode.
I have noticed Powderpost on this forum putting up a few threads on his glue chucks and it is great to see. Truth of the matter is you can turn fantastic bowls without any fancy purchased chuck.
Friction chucks have always been my chuck of choice for bowls however you have to go steady on the hollowing out as they have a square foot.
The following picture shows a bunch of bowls that were all turned on the 1 friction chuck (a scrap bit of wood). All the outside shapes were turned first, making the feet/tennons whatever size looked good at the time. Then all the bowls had the insides turned out going from the smallest footed one to the largest.
I do like the holding power of the Vicmarc numbers though with the angled feet.
camphor chair059.jpg

[Mobyturns]

The "perfect circle" dimension is the position that the jaw blanks were milled at before cutting into the four quadrant jaws. It is perhaps the optimal position for woods that don't crush easily but not necessarily the best position for softer woods as there would be very little adjustment range to allow for crushing. At the optimal "perfect circle" position there is minimal marring of the surface to be clamped in the jaws. However the design of bowls these days usually means that the tenon or recess is typically removed so it is not an issue.

Vicmarc ( & nova etc) jaws & chucks will provide a reasonably wide range of adjustment and still provide a secure hold. The important issue is not remove the scroll stop pins or to use the jaws at near maximum extension as it stresses the scroll in the chuck and does cause the leading edge of the scroll to break.

[artful bodger]

"However the design of bowls these days usually means that the tenon or recess is typically removed so it is not an issue..

Says who?.
It is a free world and I actually prefer a foot on a bowl. They are there for a reason. Look at your crockery in the cupboard at home, plates bowls etc and you will usually find they have a foot.
When making bowls for sale though a gallery or other 3rd party price suddenly becomes an issue. For the gallery because they generally double the price the maker asks and for the turner because they know how long the bowl took to make and want to make a quid as well. With this in mind it is my opinion that it is silly to re-chuck a bowl that has already had the outside and inside shape turned, to re-turn the outside shape. Just adds extra time to a piece if you can make the foot a part of the design in the first place.

[powderpost]

I have noticed Powderpost on this forum putting up a few threads on his glue chucks and it is great to see. Truth of the matter is you can turn fantastic bowls without any fancy purchased chuck.
Friction chucks have always been my chuck of choice for bowls however you have to go steady on the hollowing out as they have a square foot.

Agreed... I have been using the glue chuck method for a long time and not "lost" a bowl since I stopped using paper in the glue chuck. Some time back I did a large bowl about 400mm diameter and about 225mm deep. It was featured on the board a while back. THe glue joint was about 8mm wide and it held without any movement what ever. I used a bowl saver to cut out a block large enough to make another two bowls. That was a fair test of the security of a glue chuck. I would not have trusted any scroll chuck to do the same job. Cleaning up of the foot was done using a friction chuck.

Jim

[Woodturnerjosh]

Agreed... I have been using the glue chuck method for a long time and not "lost" a bowl since I stopped using paper in the glue chuck. Some time back I did a large bowl about 400mm diameter and about 225mm deep. It was featured on the board a while back. THe glue joint was about 8mm wide and it held without any movement what ever. I used a bowl saver to cut out a block large enough to make another two bowls. That was a fair test of the security of a glue chuck. I would not have trusted any scroll chuck to do the same job. Cleaning up of the foot was done using a friction chuck.

Jim

With the right size jaws and a properly shaped tenon, you could do that very safely with a scroll chuck. I've turned a bowl a little over 500mm diameter and 250mm deep held in a scroll chuck. It was cored out while held in the chuck and weighed about 40kgs when turning started (green timber).

Josh

[powderpost]

With the right size jaws and a properly shaped tenon, you could do that very safely with a scroll chuck. I've turned a bowl a little over 500mm diameter and 250mm deep held in a scroll chuck. It was cored out while held in the chuck and weighed about 40kgs when turning started (green timber).

Josh

The point of my comment is that the whole drama of "correct" holes and angle of dovetails can be avoided entirely. Well shaped bowls can be turned without the cost of unnecessary chucks. My reference to the large bowl was illustrate the strength of a glue chuck.

Jim

[Mobyturns]

Says who?.
It is a free world and I actually prefer a foot on a bowl. They are there for a reason. Look at your crockery in the cupboard at home, plates bowls etc and you will usually find they have a foot.
When making bowls for sale though a gallery or other 3rd party price suddenly becomes an issue. For the gallery because they generally double the price the maker asks and for the turner because they know how long the bowl took to make and want to make a quid as well. With this in mind it is my opinion that it is silly to re-chuck a bowl that has already had the outside and inside shape turned, to re-turn the outside shape. Just adds extra time to a piece if you can make the foot a part of the design in the first place.

Fashions, come and go. I have no preference one way or the other - but I do prefer to see a nice form with a well proportioned base and I don't like seeing poorly finished bases of bowls that have seen a linisher or a rough sanding job, or have obvious chuck marks in the recess or on the tenon.

No arguments from me about the time is money debate if you are a production turner - efficiency wins out.

The major problem with turners and scroll chucks is that they won't use large enough jaws on the chuck to suit the size of the project.

[hughie]

Fashions, come and go. I have no preference one way or the other - but I do prefer to see a nice form with a well proportioned base and I don't like seeing poorly finished bases of bowls that have seen a linisher or a rough sanding job, or have obvious chuck marks in the recess or on the tenon.

No arguments from me about the time is money debate if you are a production turner - efficiency wins out.

The major problem with turners and scroll chucks is that they won't use large enough jaws on the chuck to suit the size of the project.

This view point to have a foot or not has been raised here many times and it will continue to be raised . It is one of the varying eternal viewpoints, we have quite a few in wood turning