How to space stitching holes evenly, even at corners

To space stitching holes evenly and still get a hole on every corner, treat each side between two corners as its own seam. Measure it along the stitch line, divide by your iron's spacing and round to a whole number of stitches. Then either adjust the spacing very slightly so the stitches fill the side exactly, or keep your iron's spacing and share the small difference over the last few stitches before the corner.

The example throughout is a side 92 mm long on the stitch line, pricked with a 3.85 mm iron (about 6.6 stitches per inch).

Why stitching holes go wrong at corners

A pricking iron has a fixed spacing, called the pitch: the distance from the centre of one hole to the centre of the next. A side of your pattern is almost never an exact number of pitches long. Walk a 3.85 mm iron down a 92 mm side and you get 23 full stitches, 88.55 mm, with 3.45 mm left over before the corner.

That leftover has to go somewhere. If you ignore it, one of three things happens:

• The last hole lands short of the corner, so the thread cuts across the corner instead of turning on it.
• You squeeze in a final stitch that is visibly shorter than the rest.
• You carry on round the corner and the holes on the next side start in the wrong place, so the error grows all the way round the piece.

Small errors add up too. Each strike can land a fraction of a millimetre off, and over 20 strikes that becomes a millimetre or two, right where the side meets the corner.

Measure along the stitch line

Measure the length you will actually stitch: the stitch line, a few millimetres in from the edge. On wallets and card holders it's often 3 to 4 mm in; on bags and belts it's usually further.

On a rectangle the stitch line is shorter than the edge by twice the inset. A piece 100 mm wide with the stitch line 4 mm in has a stitch line 92 mm long between the corners. On a rounded corner the stitch line follows a smaller curve than the edge, so it's shorter there too.

Work out the number of stitches

Divide the length by the pitch:

92 mm ÷ 3.85 mm = 23.9 stitches

You can't have 0.9 of a stitch, so round to the nearest whole number: 24 stitches. On a side with a hole at each end, the number of holes is one more than the number of stitches, so this side gets 25 holes, two of them on the corners. On a closed loop, such as a coaster stitched all the way round, holes and stitches are the same number.

Here are a few more sides with the same 3.85 mm iron:

Stitch line	Length ÷ pitch	Stitches	Even spacing	Change
62 mm	16.1	16	3.875 mm	+0.6%
75 mm	19.5	19	3.947 mm	+2.5%
92 mm	23.9	24	3.833 mm	−0.4%
100 mm	26.0	26	3.846 mm	−0.1%

The worst case is a side that comes out close to half a stitch, like the 75 mm side. Even then the change is about 2.5%: 0.1 mm per stitch, which nobody will see.

The stitch hole spacing calculator does this sum for any length and iron, in millimetres or inches.

Two ways to deal with the leftover

Even spacing: adjust every stitch a little

Space all 24 stitches equally: 92 ÷ 24 = 3.833 mm, just 0.017 mm tighter than the iron. Every stitch on the side is the same, and there's a hole exactly on both corners.

Your iron can't change its spacing, so mark the holes first with wing dividers: set them to the spacing, step from corner to corner, and adjust them until the last step lands on the corner mark. Then prick on the marks, with a 2-prong iron where the long one won't sit on them. When the difference is as small as 0.017 mm, skip the dividers: prick as normal, and the 0.4 mm it adds up to disappears in the last few presses.

Even spacing suits pieces where each side is stitched on its own and looks best uniform: card holders, wallet exteriors, coasters.

Fixed spacing: keep the iron's pitch and share the difference

Keep the iron's 3.85 mm all the way, and fix only the end of the side. Take the 92 mm example. 23 full stitches reach 88.55 mm. You can either:

• add a 24th stitch of 3.45 mm, which is 0.4 mm (about 10%) short, or
• stop at 23 stitches and stretch the last one by 3.45 mm, which is far too long.

Adding a stitch is the better choice. Then spread the 0.4 mm over the last four stitches instead of one: each becomes 3.75 mm, about 2.6% short, and the run still lands on the corner. The 62 mm side works the other way: 16 full stitches leave 0.4 mm over, so the last four stitches each grow by 0.1 mm to 3.95 mm.

Fixed spacing is the choice when two edges must match hole for hole. Prick both from the same starting point with the same iron and the holes pair up until the very end. For edges of different lengths, read how to make gusset stitch holes line up.

Rounded corners and curves

A rounded corner is part of the run, so include it when you measure. A 90° corner on a stitch line of radius r adds a quarter circle, π × r ÷ 2, to the length. A 10 mm corner radius with the stitch line 4 mm in gives a 6 mm stitch-line radius and 9.42 mm of curve: about two and a half stitches of a 3.85 mm iron.

On a tight curve, prick with a 2-prong iron so both prongs sit on the line. A long, straight iron can't follow a curve, and its outer prongs wander off the line. If the corner radius is small, put one hole at the middle of the curve. Gentle curves, such as the sweep of a bag flap, need no hole forced anywhere: let the stitches run through them.

Pricking it by hand, step by step

1. Scribe the stitch line with wing dividers or an edge groover.
2. Mark every corner of the stitch line with an awl.
3. Measure each side on the stitch line and work out its stitches and spacing.
4. Put the first prong of the iron on a corner mark and strike. For each next strike, put the first prong back in the last hole.
5. Stop about five stitches before the next corner. Lay the iron on the line without striking and see where the prongs fall.
6. Close the gap over those last few stitches with a 2-prong iron, adjusting each press by a hair, so the last hole sits on the corner mark.

Plan the strikes before you start. A 6-prong iron with one prong in the last hole adds 5 stitches per strike, so 24 stitches is one strike of 5, three more of 5, and four single presses of a 2-prong iron at the end.

Common mistakes

• Measuring the cut edge. It's longer than the stitch line, so you plan too many stitches.
• A printed pattern at the wrong size. Printed at 96% by a "Fit to page" setting, a 3.85 mm spacing comes out at 3.70 mm and the printed holes drift away from your iron by nearly a whole stitch over 24 stitches. See how to print a leather pattern at actual size.
• Putting the whole leftover into one stitch. Spread it over three to five stitches instead.
• Starting the next side from a hole instead of the corner mark. Each side should start fresh from its corner, so errors don't carry round the piece.

How PatinaCAD does it

PatinaCAD lays out stitching holes that match your pricking irons and does this arithmetic for you. Choose your iron in the side panel, then click the stitch line with the Stitching tool. Diamond, French, flat and round irons from 3 to 5 mm are built in, and you can add the pricking irons on your bench with their exact spacing. Before you commit, the status bar shows the number of holes and their spacing. With Auto pitch, the 92 mm side above gets 25 holes at 3.833 mm.

• Fixed pitch (the default) keeps your iron's spacing. Before each corner it puts a hole on the corner and shares the odd length over the last few stitches, none more than 10% off the pitch when the side is long enough.
• Auto pitch gives each side the spacing closest to your iron that fits it exactly, like the even spacing above.
• Number of holes puts exactly the number of holes you ask for.

Each side between two corners is worked out on its own, so every corner gets its hole. The user guide's stitching chapter explains every option, and the pricking iron size chart converts any iron between millimetres and stitches per inch.

Quick answers

Should I start at a corner or in the middle? Start at a corner. Corners are where a misplaced hole shows most, so fix them first and adjust between them.

Does a small difference in spacing show? A change of a few hundredths of a millimetre per stitch can't be seen. A single stitch 10% shorter than its neighbours, right next to a corner, is much easier to spot.