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The Ultimate Guide To Choosing The Right Thread Size For Hand Stitching Leather

Updated: Mar 14


Right, you’ve probably got to grips with the basic saddle stitch, which was probably as confusing as learning to pat your head and rub your belly, but with thread.


So with that essential skill out the way, you’ve now come to ask ‘phase 2’ type questions, such as ‘What size thread should I use when hand stitching leather?’.


These questions are a good sign you’re improving and thinking beyond the basics of leathercraft. Well done to you!


As leathercraft enthusiasts, we know having the right materials can make all the difference when it comes to creating beautiful, durable fine leather goods.

And one of the most important elements in the process is what leather thread you end up using.

Barbour linen thread 18/3

But with so many options available, it can be a bit overwhelming to determine which size and type is right for your project.


In this guide, I'll answer your questions about hand stitching leather thread sizes, including:


What size thread to hand sew leather?

What's the best thread to stitch leather?

What size pricking iron for hand stitching leather?

What size needle for hand stitching leather?


So let's get started.


The size of the thread you use for hand stitching leather will depend on the thickness of the leather and the type of stitch you're using.


Obviously, a thicker thread is best for thicker leather, as it will be able to handle the tension and stress of the stitch.


Not only that, but thick leather is more often seen on projects that will be under increased loads, requiring stronger thread. Luggage, handles and a plethora of leather outdoor gear for example.


On the flip side, thick thread, however strong, is not appropriate for smaller, more delicate leather goods. Items such as wallets and watch straps.

Thick thread not only looks untidy on small items, but also causes thin leather to pucker when pulled in with adequate tension.


Saddle stitching a leather case with linen thread
Saddle stitching a leather case with thick thread, from the video course 'The Bloomsbury Attaché Case'

A good rule of thumb is to divide the thickness of the leather (in millimetres) by 7, which will give you a rough idea of the thread thickness to work with.

There is more to it than that, and I’ll share more in a bit. But for now, let’s keep things simple.


Example 1: You’re stitching together two pieces of 2.5mm leather with a total thickness of 5mm. Let’s say this will be for a large bag.


5mm divided by 7 = 0.714

The nearest thread size made by most brands is either 0.7mm or 0.75mm.


Now, if you're working with thinner leather, a lighter weight thread may be appropriate. So let’s try that again.


Example 2: You’re stitching together two pieces of 1.5mm leather with a total thickness of 3mm, let’s say this will be for a small card holder.


3mm divided by 7 = 0.428

The nearest thread size made by most brands is either 0.4mm or 0.45mm.


However, when your leather gets very thick or thin, the math explained above will tell you to start using impractical thread thicknesses. This is where you will need to use your judgment.


For example, a 15mm trunk handle or large knife sheath will have you using thread that’s over 2mm thick! The last time I saw thread that thick, it was attached to an anchor..


leather trunk handle with burnished polished edges made from vegetable tanned leather
A trunk handle requires thicker thread. Photo from the video course 'Techniques Of The Trunk Handle'

A 1.5mm edge on a slim wallet? The math would give you a thread thickness of almost 0.2mm! Again impractical.


So, as you can see, dividing your leather thickness by 7 to arrive at a recommended thread size, only works for average leather thicknesses ranging from 2.5mm to 6mm.


So, for very thick leather projects, a maximum thread thickness of 1mm should be all you need. Anything above this (outside of specialist applications) is unnecessary.


For very thin leather projects, I would not recommend linen thread below 0.4mm and polyester below 0.3mm. Otherwise you may come across durability issues.


What pricking iron size should I use?


This is where things get a little more ‘it depends’. Mostly it depends on personal taste, but I’m guessing you’d like some hard numbers to work from, so you have some foundation on which to form an opinion of your own.

A large leather pricking iron next to a small pricking iron above saddle stitched leather
6 stitches per inch (SPI) next to 12 stitches per inch

So here’s a cheat guide to get you started:


Small leather goods such as card slips, bi-fold wallets, key fobs and watch straps

= 2.7 to 3mm irons.

a saddle stitched card holder resting on a pair of leather gloves
Photo from a 'Pattern Project' called 'The Impossible Card Slip'

Medium leather goods such as clutches, long wallets, solid leather boxes and glasses cases = 3mm to 3.38mm irons.

a hand stitched glasses case rests on a book by louis vuitton
Photo taken from the video course 'How To Make A Glasses Case'

Medium / large leather goods such as handbags, briefcases, belts and duffle bags

= 3.38 to 3.85mm irons.

Hand made leather weekender duffle bag with english bridle and chrome tanned leather saddle stitched

Large and oversize leather goods such as luggage, attaché cases, trunks and rifle cases

= 3.85mm irons and above.

a case lock for an attaché case next to a leather pricking iron

What thread to stitch leather?


There are several types of thread that can be used to stitch leather, including waxed linen, polyester, and nylon. However, the best type of thread to use for traditional hand stitched leather is waxed linen.

advanced hand stitched pieces of vegetable tanned leather
Photo from the video course 'Techniques Of Hand Stitching: Advanced Skills'

Of course, if you aren’t motivated by tradition or heritage, the best thread is whatever quality thread you can get hold of from a well respected brand. Cotton however should be avoided.


Waxed linen is a natural fibre that's treated with wax to make it more durable and resistant to moisture. It's also strong and pliable, making it ideal for hand stitching leather. This type of thread will provide a clean, professional look to your leather goods and will hold up well over time.


What size needle for hand stitching leather?


Photo from the video course: 'How To Make A mini Doctors Bag'. Shown is a mini post handle.

The size of the needle you use for hand stitching leather will depend on the thickness of the leather and the size of the thread you're using. A good rule of thumb is to use a needle that's the same thickness, or slightly thicker than your thread.


For example, if you're using 0.6mm thread, you might consider using a size 004 saddler’s harness needle by John James, as that needle has a thickness of 0.86mm.


However, if you are using thread between 0.8 and 1mm, you may find it easier to stitch with a 002 sized needle with it’s 1mm thickness.


These needles are strong and sturdy enough to handle thicker leather and a single pack can last for years.


If you haven't already, don't forget to grab your FREE copy of my short saddle stitching tutorial.

Click HERE now, and get your copy instantly sent to your inbox. Get yourself a coffee and let's get started!

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