This Instructable documents how to make a leather grip to fit a handgun, or similarly shaped object. The addition of a leather grip serves a number of purposes:

It changes the texture of the grip, and can provide a more or less aggressive gripping surface
It increases the diameter of the grip, so it can better fit to the user's hand
It will absorb shock and vibration

There is a basic pattern provided, basic instructions on altering the pattern in paper to fit a given grip (which will involve some trial and error). Once the pattern is complete, it can be transferred to leather, cut, trimmed, and sewn in place.

A few considerations before starting:

As leather is a porous material, and will hold moisture, this is only recommended for use on polymer framed handguns, where the grip will not come in contact with any metal.
Make sure when developing the pattern that there are no controls in the way. This type of grip is NOT suited for any firearm with a grip safety, as it may disable that safety, and care must be taken that the grip does not interfere with the magazine release or magazine seating.
I used chrome tanned garment or upholstery leather. The chromed tanned leather should be very durable, but thin vegetable tanned leather may also be used. The advantage of vegetable tanned leather is that it may be carved and/or dyed.
I placed the smooth side out, since I wanted a less aggressive grip, and the pebbled surface of the leather I was using was sufficient. The leather could also be used rough side out, which will provide much more grip, but it will also trap oil and sweat more readily, leading to discoloration.

The tools and materials needed for this project are:

A piece of leather (for the small frame auto used, a 3" by 6" piece was sufficient)
Paper suitable for use as a pattern
Pencil
Scissors that will cut paper
Glue stick
Razor knife
A punch or awl to make holes for stitching (a nail filed to a sharp point will work)
A leather needle (these are dull, for use on pre-punched holes)
Waxed thread suitable for sewing leather

Step 1: Step 1: Scale the Pattern

Start by printing or drawing the pattern in the given image on a sheet of paper. From that, you can expand or contract the dimensions as needed to fit your grip. Note that this grip puts the stitching on the left side of the grip, which keeps them out of the way for a right handed person. Mirror the pattern to make a left handed version.

The slightly concave areas at the narrow end correspond to the trigger guard and the front of the magazine well, so measure the distance needed, and increase or decrease the height of the pattern to fit. The distance from the point at the left of the pattern to the ends of the "V" shaped dart on the right should correspond to the largest diameter around the grip. Adjust the width of the pattern to fit. With these two adjustments, you should be close enough to start fitting, so cut out your pattern, and see how it fits the grip.

Step 2: Step 2: Adjust the Pattern

Wrap the pattern around the grip, so that it looks like the pattern in the picture. You want the paper to fit as snugly as possible around the grip, with the edges just meeting together, and a minimum of wrinkling around the dart. Don't worry about the wrinkling, because unlike the paper, the leather will stretch and minimize the amount of wrinkle in the final grip. Check also on the position of the edges; you want the stitching to be just past where your fingers contact the grip, so the stitches don't rub. If the pattern is too large, mark the overlapping areas and trim them down; if the pattern is to small, then note the areas where it is too small, and cut out a new pattern to fit.

Make sure that you mark the inside of the pattern, so that you will cut your leather with the correct side out. It is easy to get the pattern turned around or flipped over.
When the paper pattern is transferred to the leather, there will actually be gaps where the edges meet, because the thicker leather won't reach quite as far as the paper. That's a good thing, because we want about a quarter of an inch of space between the edges, so that when we sew the grip on, it will stretch the leather. This helps the grip conform to the curved surface of the pistol grip, and holds it securely in place.

Once you have the pattern cut to fit, use the glue stick to attach it, with the "Inside" marking up, onto the inside surface of the leather.

Step 3: Step 3: Cut and Trim the Leather

Carefully cut along the pattern with the razor knife. I recommend using a straight edge, such as a metal ruler, to make the straight cuts. The concavity at the trigger guard and magazine well can be cut with the razor, or with sandpaper.

Wrap the leather around the grip, and check for fit. In the photos, I have placed a strip of white paper under the leather and taped it down with clear tape to clearly show the amount of gap. As originally cut, the gap was slightly too small, and the bottom right portion of the leather did not sit parallel to the bottom left side. The dart also overlapped a bit, when it the edges should just meet. After trimming right side of the leather and the widening the dart slightly, the leather wraps around like it should, with the edges of the dart meeting and laying flat, and the left and right sides showing a consistent quarter inch gap.

Step 4: Step 4: Punch and Sew

As you fit the leather around the grip, note how the edges meet, and how they will need to be sewn together. In this case, I had space for four holes above the dart, three holes below, and three along each side of the dart. I used my four hole chisel (shown) on the edges where I could, and a single hole chisel (not shown) to do the three hole sides. Put the holes a bit more than an eighth of an inch in from the edges, and make sure before you start sewing that all holes go completely through the leather.

Start out at the top with a loose stitch, and leave about an inch of thread to tie on to at the end. I chose to go straight across on the bottom, and diagonally on the top. Since the lacing goes top to bottom, then back up again, that will give me "X" shapes on the top of the leather when I'm done.
Once you get to the dart, you'll need to sew with a tight stitch. Work up and down the dart, bringing the edges firmly together, and then continue down to the bottom of the grip with a loose stitch.
Now adjust the grip to make sure it's in the correct position, and tighten up the stitches you've made so far, working from the dart out. Be careful not to get things too tight, because with only one direction of stitching, the diagonal stitches will try to pull the edges out of alignment.
Now work back up from the bottom to the top, skipping the dart, and tightening things up further as you go. Going up, the stitches should balance out the diagonal stitches from the top, so the edges should stay square as you tighten then up.
When you reach the top, pull both ends of the thread firmly, and tie them off with a square knot, and trim. The waxed thread should hold the knot tight.

That finishes up the basic leather grip. However, there are many other things that could be done to customize the grip...

Step 5: Ideas for a More Elaborate Grip

Once you've mastered the basics of making a leather grip, there are many options for improving upon it. Here are some ideas:

Embroider a pattern on the leather so that it appears on the side opposite the stitching
Add stitches along the front of the grip, to provide the feel of finger grooves
Add a layer of felt under the leather to provide a palm swell

Step 6: Making a Grip for a Revolver

This is a .38 Special revolver with a Crimson Trace laser grip. It was difficult to use the laser sight, because the activation button was in an awkward location, and required a tight squeeze to activate it. When positioning the hand to use the laser, the revolver tended to point high. The leather grip is was added in a successful attempt to remedy these issues.
The same pattern was used, with some additional trimming to the right edge (shown with pencil marks) and along the "V". The assembly steps are the same as those used for the pistol, except for the addition of two additional thicknesses of leather glued into the leather grip so that they laid across the front, adding bulk and changing the grip shape. Since the laser activation button is located under the grip, care was taken to ensure that the grip was not too tight in that location, and that the button was not under enough pressure to active the laser. To help with that, the stitching was started in the middle of the grip, not the top, and so the final knot is located across from the dart.
The end result is much easier to use. The thick layer of leather over the laser activation button requires a minimum of pressure to activate, and the revolver now points perfectly. The grip will need to be cut off and sewn back on when the batteries need replacing, but sewing only takes a few minutes, and after the grip has been in place for several days, it stretches to fit the curves and is much easier to sew.