Wall thickness caliper recommendations

[Tim Boger]

I'm gearing up to start making thin wall (1/16 to 3/16) hollow spheres 1.5 to 5 inch diameters, I'll also be piercing them as well.

What measuring device would you recommend ? There's plenty of info out there and a lot of it I've read, just tapping this valuable resource.

Thanks,
Tim

[Roger Chandler]

I am also wondering about another caliper. I have looked a couple of times at the Guage-T, I think was created by Keith Tompkins. Anyone have any experience with that particular measuring tool?

[John K Jordan]

What measuring device would you recommend ?

Many things will work, I like this kind of caliper (found a picture with Google, I know nothing about abmtools). I usually don't care about the measurement but just want a quick idea. I have calipers similar to these in several sizes, one very small made from brass. Would be pretty easy to make with some sheet brass.

332379

JKJ

[Bob Bergstrom]

The gauge T is great for measuring multiple area on a bowl quickly. It has a long reach to measure the bottom thickness. The calibrations are 1/16" and color coated. It does not work well on small closed forms. Not cheap, but I use mine a lot. I would suggest regular calipers set to 1/4" to measure spheres wall thickness. Just push one leg against the inner wall and measure the gap on the outside.

[Sid Matheny]

I use the iGaging digital outside calipers.

332387

[Brice Rogers]

I use an aluminum scissor type for the walls and lips but find that for some shapes it can't quite get in the right position and only goes in around 3 inches. So then I revert to my 10 cent gauge - - it is a piece of ~1/8 inch stiff steel wire bent into kind of an almost closed "C". I have two. One is bent so that there is a 1" gap and the other is bent to have a 1/2" gap. I just move it around the piece to see if the wall thickness is uniform. I visually look to see that the gap between the wood and the end of the "C" stays approximately constant. If I find a shape that it doesn't measure well, then I guess that I could invest another 10 cents. I suppose that copper-coated gas welding rod could work well also.

A local woodturner, Mike Jackofsky sells his own tools (hollow pro tools). (I am not promoting his tools and don't have any pecuniary interest). This one works well for measuring bottom thickness and side wall thickness. It may have limitations at the opening lip.
http://www.mikejackofsky.com/CaliperBlock.jpg

[John Keeton]

The gauge T is great for measuring multiple area on a bowl quickly. It has a long reach to measure the bottom thickness. The calibrations are 1/16" and color coated. It does not work well on small closed forms. Not cheap, but I use mine a lot. I would suggest regular calipers set to 1/4" to measure spheres wall thickness. Just push one leg against the inner wall and measure the gap on the outside.


Here is a pic and link (http://www.packardwoodworks.com/Merchant2/merchant.mvc?Screen=CTGY&Category_Code=meas-wallthic) to the one I think Bob has referenced. I still use the old style scissor gauge, but this looks pretty slick!http://www.packardwoodworks.com/Merchant2/graphics/00000001/132101-img.jpg

[Thom Sturgill]

The Veritas deep calipers are my favorites.
332421

Use the screw adjustment to make the tips contact then pull the calliper open and remove them. When you release the tension they return to where you had adjusted and you can see exactly what the thickness was. The shape seems to work well also. Sold by Lee Valley and Packard.

[Bob Bergstrom]

Here is a pic and link (http://www.packardwoodworks.com/Merchant2/merchant.mvc?Screen=CTGY&Category_Code=meas-wallthic) to the one I think Bob has referenced. I still use the old style scissor gauge, but this looks pretty slick!http://www.packardwoodworks.com/Merchant2/graphics/00000001/132101-img.jpg


Yes, I've been using this gauge with open form bowls for about 4 years. I liked it so much I talked the club into buying one for the workshop. It is precise and fast. Slide it back and forth and watch the gauge move. I rarely use the figure 8 ones. They always seem to have a gap when closed. I've tried filing and bending, but not happy with them.

[Robert Hayward]

Home made for less than a dollar not counting the aircraft grade plywood borrowed from my RC airplane building. The thickness numbers are almost worn off, but still readable in person.


332428

[David Delo]

Tim,

Just to clarify, are you planning on hollowing the sphere thru a hole in the tailstock side and then covering the hole with either a base or finial? Or are you going to leave a tenon on each end and split the sphere in half and glue back together after hollowing? If your planning on splitting them, I think you can use your fingers to gauge thickness thin enough to pierce the wood with the size of half spheres you would be working with.

[Tim Boger]

Thanks to all that have offered feedback, I really appreciate your help!


Hi Dave,

Here is the process I have planned, turn a blank into a cylinder the lay out the center and end marks of the sphere ... use the Vermec Sphere Jig and turn a sphere.

With a tenon on both ends I'll use a thin parting tool and cut it in half .... at this point I will again use the Vermec Jig to hollow the interior of each half then glue the halves together.

The caliper I think will be useful and fun to use is the igage 332473Sid suggested it.

I'm waiting for a hollowing video from Vermec, the sphere making I have figured out, it's simple and works great. The hollowing I'm not clear on yet

Tim



Tim,

Just to clarify, are you planning on hollowing the sphere thru a hole in the tailstock side and then covering the hole with either a base or finial? Or are you going to leave a tenon on each end and split the sphere in half and glue back together after hollowing? If your planning on splitting them, I think you can use your fingers to gauge thickness thin enough to pierce the wood with the size of half spheres you would be working with.

[Dwight Rutherford]

Another option would be to make a template that is 1/16" or 3/16"" smaller than the outside diameter of your sphere. Use this for your guide for hollowing. Manila folders work well and one can get a lot of templates for very little cost.
May not be an issue but if you turn the sphere with a jig, when it is split in half, the kerf caused by the parting tool will result in no longer having a perfect sphere.

[Tim Boger]

Hey Dwight ... I hadn't thought about the two halves not being a perfect sphere after being parted in half. Perhaps the parting should take place a couple of passes before the cutting edge takes away the center pencil line.

Good catch, thanks.



Another option would be to make a template that is 1/16" or 3/16"" smaller than the outside diameter of your sphere. Use this for your guide for hollowing. Manila folders work well and one can get a lot of templates for very little cost.
May not be an issue but if you turn the sphere with a jig, when it is split in half, the kerf caused by the parting tool will result in no longer having a perfect sphere.

[Tim Boger]

Hi Thom ... I really like the look of these calipers.
Tim



The Veritas deep calipers are my favorites.
332421

Use the screw adjustment to make the tips contact then pull the calliper open and remove them. When you release the tension they return to where you had adjusted and you can see exactly what the thickness was. The shape seems to work well also. Sold by Lee Valley and Packard.

[Tim Boger]

Home made for less than a dollar not counting the aircraft grade plywood borrowed from my RC airplane building. The thickness numbers are almost worn off, but still readable in person.


332428

Nicely done Robert.
Tim

[David Delo]

Thanks to all that have offered feedback, I really appreciate your help!


Hi Dave,

Here is the process I have planned, turn a blank into a cylinder the lay out the center and end marks of the sphere ... use the Vermec Sphere Jig and turn a sphere.

With a tenon on both ends I'll use a thin parting tool and cut it in half .... at this point I will again use the Vermec Jig to hollow the interior of each half then glue the halves together.

The caliper I think will be useful and fun to use is the igage 332473Sid suggested it.

I'm waiting for a hollowing video from Vermec, the sphere making I have figured out, it's simple and works great. The hollowing I'm not clear on yet

Tim

I thought that might be what you were thinking process-wise because I've been thinking of doing the same thing with either the same species for each half or even different species for the two halves. I'm just a weekend warrior wacker hacker but I still don't think a fancy-dancey calipers is absolutely necessary to accomplish this. Yes, I think it's necessary to get as thin as possible depending on what/which piercing equipment you have but the OD is going to be defined at the point you part the 2 halves. IMO all you need is to do is get close within a few thousands for the 2 halves to glue them back together. Dwight just suggested a very quick low cost solution. Hey, far be it from me to suggest not buying a store bought solution but just don't see it as critical for this single application. You want to use it for other HF's & applications.......fine, go for it.