Cutting A Sole To A Specific Thickness

Good morning fellow shoe nerds of the world. And what a wonderful morning it is, the sun is out, gentle breeze, a balmy 20 degrees. Perfect for an informative blog post on cutting your sole to a specific thickness. Contain your excitement people and read on!

When we teach students in our handsewn shoemaking class about attaching the sole, we simply give them a welt and a piece of soling leather and, at the critical moment, we get them to cut the sole roughly to size and glue it on with rubber solution prior to stitching it. This method works fine if you are making shoes for yourself or for friends/relatives, but if you are making shoes for a customer, you have to agree a thickness for the sole (a combination of welt and sole). This is what bespoke means, bespoken, spoken about, agreed between craftsman and client.

Now this presents a challenge to the shoemaker. How do you make sure the sole is the same thickness all the way round? Well, here is how you do it.

There are some general points to bear in mind when you are doing this. A critical sole thickness seems to be 3/16" (5mm). This is a thin sole and very rarely do I make a sole any thinner than this (except on ladies shoes) but the principle applies nonetheless. When you stitch a sole, the thickness you skive to before you stitch it can change once the stitching is finished. And, unfortunately, the thickness can increase or decrease, depending on the thickness you aim for. Quite why this happens I am not sure. It definitely has something to do with the thickness of the thread; the density of stitches; the shape of the hole the stitching awl makes; and the way you finish the edges. There is conjecture about this and I welcome comments, but I am more concerned with results than reasons.

This is where the 5mm threshold comes in. If you stitch at 5mm, the sole thickness before and after stitching will remain the same. If you stitch at more than 5mm, the sole will be thinner after you stitch than before. And if you stitch at less than 5mm (not recommended, try cutting a channel in 2.5mm of sole leather!), the sole will be thicker after you stitch than before. This is significant.

People have said to me that you can buy sole leather and welts so that they will be exactly the thickness you need. This is true. However, leather is an organic product and when you buy a sole bend, it might not be the same thickness all the way through, which will affect your edges - there is nothing worse than wobbly edges, after all!
Also, if you use a thicker piece of sole leather and skive it at the edges, you will have a thicker, more long lasting sole at the part where the customer walks. This means the sole will last longer and you will have a happier client. This is especially the case on thinner, dressier soles.

So, enough of theory, here is how to achieve perfect, even edges of a desired thickness.

You have welted your shoe; put in a shank; and put in cork filler on the forepart.

You have also trimmed the welt (evenly with a very sharp knife) and are ready to attach the sole.

The sole must be mellow (soaked in water for at least an hour and then dried to about 80% dry). This way it is easier to work.

Place the shoe on the sole and carefully draw around the welt and the heel. Try to make sure the shoe does not move. It helps if you tilt it at the front and lay it flat for the joint. The inside waist can prove difficult, and sometime I use the tip of an awl to trace the line of the welt and then fill it in with pen after. Especially on shoes with a very pulled in waist.
Give your self plenty of room round the heel, you will cut off all the excess later.

When you have made a final check that the lines are correct, cut to within about 1mm of the line. You can be rough about this at this point.

Now you need an iron to hammer the sole on. I use an old clothes iron with a flat surface. I also use a London hammer which I have ground flat on the grinding machine. This avoids making dents on the sole surface.
hammer the inside part of the sole up to about 1/2" (12mm) from the edge. Hammer all of the heel area. This is an important step because it compresses the sole leather and makes it harder and more durable. If you don't do it, the customer will be back before you know it for a resole. And they won't be happy!

At this stage I like to put the shoe back on the sole to check the line has not changed. Depending on the nature of the sole, the hammering can make it spread out a bit and you may need to remake your pen line.

Unfortunately, fellow shoemakers, time has got the better of me and I must stop here and make my way to Gieves and Hawkes to make some shoes and see a client at 11.

I will continue with this next week, bringing another invaluable photo essay to a conclusion. So, until that time, have a great week, and happy shoemaking!