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DIY The perfect leather craft knife - build along tutorial

Updated: Dec 22, 2020

The Craftsman's Craft Knife




One of the most used, if not THE most used tool in every leather craftsman’s arsenal.

It is the essential instrument that starts every leather project we make.


But what makes a good craft knife capable of covering most of the tasks that we encounter in our pursuit of perfection?


It is true that there is no such thing as the ‘best’ tool for every job. Not only is the ‘best’ highly subjective, but as your demands change, so do the tools we need.


I will give you my thoughts on what makes, shall we say, the ‘ideal’ craft knife.

This is also the design brief that I had when I went in search for a more suitable knife, a few weeks ago.

Of course, the very fact that this blog post exists indicates that I wasn't successful in finding one to buy!


Brief:


Ergonomic: The knife should sit comfortably in the hand so that extended use or use on heavier hides doesn’t cause hand fatigue or excessive pressure points.


Weight: A heavier knife tends to be more stable in the hand and provides a smoother experience, essential when cutting out from patterns, or even making patterns.


Blade lock: Even so called ‘locking’ blades from NT Cutter, Olfa and Stanley, can experience slipping when pulling through thick leather or pattern card. This feature is an absolute must. Where the blade is set, it should stay.


Snap off blade: This is a very subjective choice. But I find that as much as I enjoy sharpening blades (I do!), stopping to sharpen a blade every so often ruins my flow and distracts my attention away from what I am doing.

Not so bad if I’m working on a small project, but a large bag? With a snap-off we are back to razor sharp again in a few seconds.


9mm blade size: The 9mm snap-off blade size is ideal, as this allows for a knife slim enough to be held like a pen with the handle extending over the thumb. This maximises control and puts your fingers (pinkie and ring) against the work surface to anchor your hand at 90 degrees giving better right angle cuts. For more information on this please see video course 'Techniques Of The Blade'.


To further lord the benefits of the snap-off blade, one of the main issues with one-piece blades such as the one supplied with the L’Indispensible knife, is that the point begins to wear after time.

Sure, you can sharpen or strop the blade back to a hair popping edge, but the very tip begins to round out eventually, meaning that it doesn’t sink into the leather as fast as it did when the blade was first profiled.

Using steel with higher edge retention properties only slows this effect.


A snap-off on the other hand - 'snap' and the point is back.


The build


Now you may be imagining that I am going to tell you to go and but some raw brass blanks to start milling into shape.


Not quite, I don’t have that much time to do it myself! So instead we are going to hack this part by purchasing a leather trim knife from eBay and patiently waiting for it to be sent.




I don’t really care that it comes from China, solid brass is solid brass even if it came from Mars (wouldn’t that be something!).


Most of the hardware from this knife can be thrown away, in fact as a trim knife it’s horrible. The blade wanders something terrible, but that’s fine, we’ll take it from here.


With the handle stripped bare, we are going to get some coarse sandpaper, i’m using 120 grit here, and we are going to sand the sides of the handle to that it is nice and flat.

The epoxy that we will be using later now has something to adhere to as well.


Nice and flat with a rough surface - perfect

Next we are going to take some material that we can use to make the ‘scales’ of the knife handle. These are going to be what covers up the voids in the handle, plus we can shape them exactly how we like them.


What to use? I’ve used 2mm thick Vulcanised fibreboard here. This is not ideal as it can be hard to find, though I have seen some pieces for sale on eBay for knife makers.


I purchased more square metres of VFB than I care to mention, thinking that it was going to be the cats whiskers for reinforcing attache briefcases, it is not. There, I just saved you about a grand. Minimum orders eh?



You can use what you like here - Hardwood such as walnut or beech, 2mm MDF or hardboard, micarta (good choice) or even aluminium.


But hey, you’re the one holding a knife, so you can use what you like, just don’t take my tools.


Cut the scales so that they are a few mm’s larger than the handle width ways and length ways.


Drill a 4mm hole where it matches to the handle

IMPORTANT:


Now, you see the part on the brass handle where the screw goes in at the front?

We are going to drill a 4mm hole at the front of one of the scales so that you can place a grub screw/set screw onto the handle to secure the blade later on.


Now that’s done, it’s time to adhere (glue) them to the brass handle.


Sand the side of the scale that you are going to adhere, then wipe down the scale as well as the brass handle with acetone or alcohol, so that no debris or fingerprints compromise the bond.


Wear clean gloves from here on in.


Mix up a good quality two part epoxy, use one that takes longer to bond.

5 minute epoxies usually have less strength than slow setting epoxies. But 5 minute still works well.


If using a slow set, take advantage of the longer cure time and mix the two parts as per instructions for a good 2 minutes. 5 minutes is better.


Mix up 2x as much as you think you’ll need.


Every molecule of part A should be sitting next to part B.

Get this correct now, or scales can potentially pop off if your blade falls on a hard floor (always put walkway carpets down around your work space - your awl, pricking irons and skiving knives will thank me when the inevitable always happens. Carpets are cheap, tools are not - except this one obviously, but you're paying in effort!).


Apply a thin layer of epoxy to the side of the scales that you sanded and cleaned. Then apply a layer to each side of the handle that you also sanded and cleaned.

Avoid the 'more is better' attitude here, otherwise you can get a big blob of epoxy inside that will stop you feeding a blade into the knife later on.


Make sure that the side of the scale with the 4mm hole, matches perfectly with the threaded hole at the front of the knife handle.


Watch your fingers here and do not touch the surfaces to be bonded with your gloves - you’re wearing gloves right?


Now carefully apply the scales to the handle, there is going to be some squeeze out of epoxy, so have some shop towel to hand.


Use several small or medium sized clamps to apply pressure along its length.

Check that the scales overhang the handle along the length and the ends.


Got patience?


Now it’s time to place the whole thing somewhere warm for at least 24 hrs (48 is better).

Make sure that you place something underneath the knife in case there are any drips.

Epoxy does not cure well in cold environments, so place in an airing cupboard, boiler room or move to Dubai.


One last time before you walk away, check that the hole in the knife scale at the front, lines up with the hole at the front of the blade where the screw goes - very important!


Matching up the blade retention screw hole

Looking for something to do for two whole days while you wait?


Well, if you would like to learn how to use your new knife to it’s full potential, now would be a great time to check out the Leathercraft Masterclass video courses.


30 full courses and counting.

Focusing on giving you the fundamental skills such as hand stitching, skiving and edge finishing, all the way to full project courses such as luxury watch straps, card wallets, raised belts and attache cases.


There is also a NEW course teaching you luxury bag making, so there is going to be something to interest you.


New to leathercraft? Overwhelmed with where and how to begin?


Simply start with video #1, and progress through the courses as your knowledge grows, that's how we’ve designed it for you.


Start your journey today and click the image below to view the guide.



Now, it’s day three and you are staring at your knife like a ravenous wolf! It’s ok, go ahead, pick it up and remove the clips


Right, let’s make you a new knife shall we?


So ideally you need a vice or something which will hold the knife as you remove excess material from the scales so that they are level with the brass handle.


No vice? Use two blocks of wood and clamp them together with some decent pressure. If you place something of equal thickness to the knife at the bottom of the blocks, you will get a more secure hold.


Now you can either use a sanding block or a small wood plane to remove excess material until all sides are level.



If using a plane, stop around half a mm before you get down to the brass and finish by placing sand paper flat on the table and working the knife handle back and forth until you start sanding the brass. Stop when everything is level and looking clean.


TIP: If you have chosen wood as a scale material, make sure the plane blade is extremely sharp and aim to shave in the direction of the grain, not against the grain - if it’s not perfectly straight in line with the knife. Otherwise you can lift up the grain and well, it’s not good.


Shaping the handle


You can have some creative freedom here . I’ve opted for a taper towards the bottom of the knife handle for comfort. This is done by running a plane blade along its length while tilted towards the bottom. Only a few strokes are needed and make sure the plane is only taking off the shallowest of shaves.


The tapered profile is starting to take shape

Finish with medium grit sand paper face up on the table to even out any inconsistencies. Don’t forget to sand around corners by hand as well as the ends so that you don’t have any sharp corners.



Then work down in grit size to 400, 600, 800 and 1000 until you start getting the kind of polish you want to achieve.

A final buffing with appropriate compound on a polishing wheel or Dremel is optional. I like the Dialux brand of polishes.


Starting to smooth out here using 600 grit sandpaper

But remember, while a high polish looks very nice, it’s not that tactile to hold in the hand, plus any scratches stand out.


This is a tool after all, so function first, no compromises. Your leatherwork should always take first place in a beauty contest against your tools. Otherwise, something it not quite right!


Lastly, seal any porous material that you have used for the scales. Wood, or hardboard for example will do well with a polyurethane sealer. Two coats minimum with a light sanding in between.


Gloss varnish is always tougher, so if you want a smooth matte finish, simply take an abrasive green scouring pad (yes the one you do the dishes with, or at least people with a broken dishwasher) and rub over the surface for the desired effect.


A quick little screw


You'll notice that the original trim knife came with a brass locking screw that you can finger tighten. Well mine was taken by the workshop gods, so I had to use a stainless steel M3 (metric 3mm machine thread) screw and cut it to fit.


Anyway, take you brass locking screw, and screw it into the knife with a blade inside the knife.

Apply tape to the threads that are still exposed, and use this to mark where you need to cut the screw.


The idea is that we want the top of the locking screw to sit flush or just under the surface of the knife.

This is where your middle finger rests, so you don't want an irritating screw ruining your cutting experience. Aim for a smooth comfortable screw.


Carefully place it into a vice and trim to length. You can use a hacksaw, a Dremel tool, or if you have no orders pending, a file.


Use leather or board in the jaws to protect the screw

To finish off the screw head, use any of the above tools to make a slot for your screwdriver to fit into. A 1-1.5mm depth is good.


Have a small flat headed screwdriver handy to check depth and width.


You can polish your little screw head too:


Now, we want a nice clean screw, so wipe it down with alcohol or acetone. A toothbrush is good, just not one you use. Then insert it into the knife with a fresh blade.


Et voila!





Click for spare blades


Thank you for reading, don't forget to subscribe on YouTube for more reviews and course previews coming up.


Philip

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