Same Pattern, Different Weights

[ThisIsMyFirstRodeo]

Hey all,

Is there a semi-reliable method for altering a template for different weights, besides trial-and-error (i.e. 2-3oz vs 5-6oz)? I know many times a slight variation in final dimensions is trivial, but I’m trying to make some can koozies, which obviously need the same final dimensions.

Thank you all, and may you never burn your bacon!

— AZR

[DieselTech]

Yes there is a formula for patterns & different leather weights. I just cant remember where I had seen it. It was a YouTube video I had watched. 

[Digit]

The length of a strip of paper that goes around a can is equal to the circumference of that can.

Extrapolate to something thicker like leather: recalculate the circumference. Start from the diameter of the can and add twice the thickness of your leather; multiply by pi and you have your circumference (circumference = 2 * radius * pi = diameter * pi).

Example: lets take a 66mm diameter can. Measure the actual thickness of your 2-3oz leather; for ease of calculation I'll go with 2.5oz (=1 mm); (66mm + 2 * 1mm) * pi = 213.6mm
If the actual thickness of your leather is 5oz (=2mm), the calculation becomes (66mm + 2 * 2mm) * pi = 219.9mm

[JLSleather]

This is simpler than many people make it seem.  HOW MANY of us have made belts for somebody who INSISTED they were giving the correct size, only to find out that the belt cant be the same size as the pants.  Ever try to put a 2" pipe around a 2" pipe... ?  Yeah, like that.

So everything has a thickness.  Take that pipe example.  Say you have a 2" inside diameter.  THen you have different wall thickness or "schedule" of pipe, and the thicker the wall the larger the outside diameter and the distance around it.

Lack the time right now to get too involved, but basically, if you use the same pattern you're (with almost all patterns) measuring the OUTSIDE of the finished goods.  Taking the example of a can from above, you might have a pattern for a 6/7 oz leather.  Lets say for ease of mathalizin', it's exactly 6.5oz.   So youre leather cut piece will measure about .101" thick on the "inside" and the "outside".  But wrap that piece around the can, and the OUTSIDE will be short because the outside radius needs to be longer than the inside.

SO THEN, changing the leather thickness will change the DIFFERENCE between teh ID and the OD of the formed piece.  Leather "ounces" are measured in 1/64ths of an inch. So IF you had cut a slight angle on the ends of the piece of 6.5oz so that it fit flush, then changing the leather to .. say 4.5oz would cause the INSIDE of the koozie case to be 1/16" LARGER.
Doing the math:
OUTSIDE is still the same from the pattern.  INSIDE is then 2 oz thinner per side, for a total of 4 oz less leather, = 1/16" larger I.D.

I sometimes get this with holster patterns. SAYS right on the pattern what weight leather to use, but I'll sometimes get a message from somebody madder'n a wet cat 😠 cuz the "?@!! GUN DONT FIT .... then later admit that he/she used a pattern that said 7/8 oz leather but they used 9/10 oz leather (or other way around).

[chuck123wapati]

I don't see the need to even bother with thinking about it. First off, leather stretches; it's not like a board or metal, so a couple mms dont matter much, at least for what I make. I sand that much off getting the edges clean. Second, I don't usually use the same pattern for extremely diferent leather thicknesses. Like 2 oz vs 10 oz, really, what you make with 2oz leather that you would want to make in 10 oz leather or vice versa?  It's not worth doing the math IMO, for close leather weights at least I've never had a problem.

[JLSleather]

9 minutes ago, chuck123wapati said:

It's not worth doing the math IMO, for close leather weights

True - easiest way to guarantee it will fit would be to cut a strip of the leather you want to use, trim in place, and there's the width you need.

OTHER HAND, it's smart to do the math if you're ordering any quantity of leather, to avoid unnecessary expense on leather that doesn't work for what you want.

That said, STohlman did a "dice cup" in one of his "leather cases" books, virtually the same as a "koozie", so a guy might just look that up and have a pretty good idea what to use/do.

[ThisIsMyFirstRodeo]

11 hours ago, JLSleather said:

True - easiest way to guarantee it will fit would be to cut a strip of the leather you want to use, trim in place, and there's the width you need.

OTHER HAND, it's smart to do the math if you're ordering any quantity of leather, to avoid unnecessary expense on leather that doesn't work for what you want.

That said, STohlman did a "dice cup" in one of his "leather cases" books, virtually the same as a "koozie", so a guy might just look that up and have a pretty good idea what to use/do.

I have that book at my work table actually. it’s vol 2 I think 

[Bert03241]

I suck at Math, so I'll just use Chucks method