DU 405: Jean Machines — The Top 10 Tools Needed to Make a Pair

Summary

It takes approximately ten machines to make a pair of jeans properly. Each one does one thing — one stitch type, one operation — and does it fast, with precision, for decades without complaint. That's not a limitation. That's a master of engineering. That's greatness. This article introduces every machine in the kit: what it does, what it's used for, and why it exists. It reminds us that the single most important thing is to begin, and makes the case that the analog world has something to teach us about focus, depth — and the value of doing one thing extraordinarily well.

Q&A

How many machines does it take to make a pair of jeans?

Approximately ten. Each industrial sewing machine does one thing — one stitch type, one operation — and does it fast, with precision, for decades. The ten machines used in jeans construction are: single needle lockstitch, double needle lockstitch, overlock (serger), coverstitch, bar tack, buttonhole machine, waistband machine, felling machine, kick press, and industrial iron. A beginner can start with just one machine and an iron. The full kit comes with time.

What is the difference between a lockstitch and a chain stitch?

A lockstitch uses two threads — an upper thread through the needle and a lower thread on a bobbin — that lock together inside the fabric on each stitch. It is strong, flat, and nearly identical on both sides. A chain stitch uses two threads, but it does not use a bobbin; the bottom thread is fed through a "looper" and runs continuously. Chain stitch allows slight give and is used on the bottom of the waistband for this reason — the stretch accommodates the body's movement where a rigid lockstitch would not.

What is a flat-felled seam and which machine makes it?

A flat-felled seam (also called a lap seam) folds two pieces of fabric over themselves and stitches them flat, encasing the raw seam allowance inside the fold. The result is clean on both faces with no exposed edges and no fraying possible. It's made by the felling machine — also called a lap seam machine — and is used for the yoke-to-back-panel seam and the center back seam, which is the most technically demanding operation in jeans construction.

What is tension and why does it matter?

Tension refers to the resistance applied to thread as it feeds through the machine, and the pressure applied to the fabric by the presser foot. There are three types: top thread tension (moderate resistance — like a dog that doesn't want to go for a walk), bottom thread tension (light resistance — like a dog that does), and presser foot tension (the downward pressure on the fabric as it feeds). Getting tension wrong means uneven stitches, puckered fabric, or thread that breaks. It's the thing every beginner ignores and every experienced maker checks first.

What is a bar tack and where is it used?

A bar tack is a dense cluster of stitches — 28 or 42 — fired by a specialized lockstitch machine in approximately two seconds. The result is a tight block of thread that reinforces a single point under stress. Bar tacks are used wherever force concentrates on a pair of jeans: belt loops at the waistband, pocket corners, the fly base, and the keystone. FITTED Underground uses a 42-stitch machine rather than a 28-stitch — more thread, more reinforcement, negligible difference in time.

Test Your Knowledge

Click each answer to reveal whether it's correct.

1. Which machine is described as the one no jeans workshop can operate without?

A. The felling machine

❌ Incorrect. The felling machine is essential for flat-felled seams, but it's the single needle lockstitch that's described as the one machine no jeans workshop can operate without — the workhorse with the widest range of applications.

B. The single needle lockstitch

✓ Correct. The single needle lockstitch is the workhorse of jeans construction — used for front pockets, keystone, rear pockets, and the top of the waistband. It has the widest range of applications of any machine in the workshop and is the one no jeans maker can do without.

C. The waistband machine

❌ Incorrect. The waistband machine is critical for one specific operation, but the single needle lockstitch is the machine described as indispensable to any jeans workshop.

D. The industrial iron

❌ Incorrect. The iron is described as indispensable — "what separates a workshop from a sweatshop" — but the machine described as the one no jeans workshop can operate without is the single needle lockstitch.

2. What distinguishes a cut-after buttonhole machine from a cut-before machine?

A. Cut-after machines are faster and used for mass production

❌ Incorrect. The distinction is about sequence and strength, not speed. Cut-after machines sew the reinforced keyhole shape first, then cut the opening — producing a stronger buttonhole because the stitching holds the fabric before any cutting occurs.

B. Cut-after machines sew first, then cut — producing a stronger buttonhole because the stitching holds the fabric before any cutting occurs; this is the standard for denim

✓ Correct. Cut-after machines sew the reinforced keyhole shape first, then cut the opening. This produces a stronger buttonhole because the stitching holds the fabric in place before any cutting occurs. It does leave some cut threads visible at the opening — not defects, but relics of a time when strength mattered more than a refined finish. Cut-after is the standard for denim.

C. Cut-after machines produce a cleaner finish with no visible threads at the opening

❌ Incorrect. It's the opposite — cut-after machines leave some cut threads visible at the buttonhole opening. These aren't defects; they're the result of cutting after the stitching is complete, which prioritizes strength over a refined finish.

D. Cut-after machines use a heavier thread weight for additional reinforcement

❌ Incorrect. The distinction between cut-before and cut-after is about the sequence of sewing and cutting, not thread weight. Thread weight is a separate variable — FITTED Underground uses Tex 80 or heavier for buttonholes regardless of machine type.

3. What is the correct way to dial in presser foot tension?

A. Set it to the maximum recommended by the machine manual, then reduce if the fabric puckers

❌ Incorrect. The article recommends the opposite: start loose — back the tension off more than you think you need — then slowly increase until the fabric feeds smoothly and straight. Trust what you feel more than what the manual says.

B. Back it off more than you think you need, then slowly increase until the fabric feeds smoothly and straight — trust what you feel more than what the manual says

✓ Correct. The best way to dial in presser foot tension: start loose, then tighten incrementally. Too much tension warps the fabric, pulling it out of alignment. Too little and the fabric won't feed consistently — it fishtails, like a car losing traction in the rain. Start loose. Tighten incrementally. Trust what you feel.

C. Match it exactly to the top thread tension for a balanced stitch

❌ Incorrect. Presser foot tension and thread tension are separate variables that serve different purposes. Matching them to each other is not the correct approach — each needs to be set independently based on what the fabric needs.

D. Keep it consistent across all fabric weights — tension should never change between projects

❌ Incorrect. Tension needs to be adjusted for different fabric weights and operations. A setting that works for a single layer of denim will be wrong for sixteen layers at the center back yoke intersection. The advice is to start loose and adjust incrementally based on how the fabric feeds.

4. Which machine is described as a "nice-to-have, not a need-to-have" for a beginner?

A. The overlock machine

❌ Incorrect. The overlock is a core construction machine used for inseam closure, side seams, and fly construction. The machine described as a nice-to-have is the double needle lockstitch.

B. The double needle lockstitch

✓ Correct. A skilled maker can achieve the same result as a double needle lockstitch with two passes on a single needle machine. The double needle becomes genuinely valuable in a production environment — where running the same seam twice on different machines adds up to significant time savings over a run — but it's not essential to start.

C. The kick press

❌ Incorrect. The kick press is required for attaching rivets and buttons — every rivet and button on every pair of jeans passes through it. The machine described as a nice-to-have is the double needle lockstitch.

D. The bar tack machine

❌ Incorrect. The bar tack machine reinforces every stress point on a pair of jeans — belt loops, pocket corners, fly base, keystone. It's a core machine. The double needle lockstitch is the one described as a nice-to-have rather than a need-to-have.

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By Eric Steffen
Founder / Maker
FITTED Underground

Lesson from the Analog World

Before we dive into the machines themselves, here's an ode to the analog:

Industrial sewing machines — many of them designed in the first half of the twentieth century, built from cast iron and steel, running on mechanical principles that haven't changed in a hundred years — do one thing. They do it very well. They do it at great speeds. But don't ask them to do two things, because the answer will be no.

The one thing that they, the do incredibly well. And that is enough.

The digital world is racing toward machines that do everything. Industrial sewing is beginning to follow, with computerized machines that can be programmed for multiple operations and adjusted with a touchscreen. Some of that is genuinely useful. But the older machines at the heart of serious jeans production remain stubbornly, magnificently analog. They don't multitask. They don't update. They don't need to.

The one thing that they do, they'll do for another hundred years — if you take care of them.

There's a lesson in that — about focus, about depth. About the value of doing one thing extraordinarily well rather than many things adequately. It's not a coincidence that the industry built on these machines produces some of the most enduring garments ever made.

Getting Started — You Don't Need Much

Onwards to the machines...

I often receive emails from makers early in their denim journey with a simple question — What machines do I need to begin? The answer: None. Don't believe me? Just ask Keruk Denim, an Italian maker living in Japan who makes hand-stitched jeans without any sewing machines. Just a needle and thread. So if you have a home sewing machine and an iron, you're on your way.

In fact, what's more important than having all the right machines when you're starting out is having the right thread. For a quality pair, you'll need Tex 80 thread or above. We typically use tex 105 and 120. Make sure you have the correct needle size (size 19/120), and you're good to go. To quote the German writer Johann Wolfgang von Goethe said:

Whatever you can do, or dream you can, begin it. Boldness has genius, power, and magic in it.

A single needle lockstitch machine can handle more than most people realize. Standard stitches, yes — but also advanced applications: felling seams, stitching bias tape to close exposed edges, topstitching. The one thing it can't do easily is a machine buttonhole, which you can learn to make by hand. So if you have a single needle machine, you're on your way.

When Hobby Becomes Passion

With that said, if the interest holds then at some point you'll want to make the jump from home machine to an industrial one. The reason is simple: denim is thick. Sewing through multiple layers of 13oz or 14oz selvedge (I'm looking at you, felled seams) gets chunky. A home machine may groan where an industrial machine will sing. They're build for this. Get a good one — and you'll never need another one your whole life.

When I left finance to start FITTED Underground in 2014, I wondered "Why don't bespoke tailors make jeans?" 

The answer: it take s a lot of industrial machines to make a pair of jeans the traditional way.

A lot machines means a lot of space to keep them; knowledge to maintain them; and years to master them. Jeans are their own beast. A tailor needs to learn new machines, new processes, new techniques. Most tailors, quite reasonably, look at that mountain and decide not to climb it.

But I looked at it, and never looked away. I thought it would take six months to become genuinely great at making jeans. It took more like six years.

Denim was my mountain to climb. And in the end, the difficulty was the point — hard things are worth doing because of what they teach you about yourself.

The Full Kit: Ten Machines to Make a Pair of Jeans

If you're ready to go down the rabbit hole, here's what's waiting for you at the bottom: It takes approximately ten machines to make a pair of jeans properly.

Each industrial machine does one thing — one stitch type, one operation — and does it fast, with precision, for decades without complaint. That is beginning to change with newer "smart" industrial machines that offer multi-functionality. But the older machines the industry was built on — those marvels of engineering from the early twentieth century — were designed for one purpose and one purpose only. Ask them to do something else, and they will simply say no. Ask them to do what they were designed to do, and they'll create a thing of beauty — at speed.

With no further adieu, here are the ten machines you'd need to make a classic pair of jeans:

1. Single Needle Lockstitch

Photo / video TBU

What it does: A lockstitch uses two threads — an upper thread fed through the needle and a lower thread wound on a bobbin beneath the needle plate. As the needle pierces the fabric, it carries the upper thread down through the material. A rotating hook catches that thread and loops it around the lower bobbin thread. When the needle withdraws, both threads lock together inside the fabric — creating a stitch that is strong, flat, and nearly identical on both sides. It is the most common mechanical stitch in the world.

What it's used for: Front pockets, keystone, rear pockets, top of waistband. This is the workhorse of jeans construction — the machine you'll spend the most time at and the one that has the widest range of applications.

Notes: Vintage machines like older Singers are beloved for their build quality and longevity, but any reliable industrial single needle with a backtack function will serve you well. As production volume increases, an auto-cut feature — which trims the thread automatically at the end of each seam — saves meaningful time. This is the one machine no jeans workshop can operate without.

Also, for production environments, a double needle lockstitch is a useful addition — two needles, two simultaneous lockstitches, two parallel rows of thread in a single pass — but a skilled maker can achieve the same result with two passes on a single needle machine.

2. Chainstitch

Photo / video TBU

What it does: A chain stitch uses two threads, but it does not use a bobbin; the bottom thread is fed through a "looper" and runs continuously. Chain stitch allows slight give and is used on the bottom of the waistband for this reason — the stretch accommodates the body's movement where a rigid lockstitch would not.

What it's used for: Chainstitch hems are important in the denim world because of the roping effect they are able to achieve. Historically made with a Union Special 43200G, roping can actually be made by most chainstitch machines, so long as you use a folder or have a skilled operator.

Notes: A chainstitch runs, so undoing one is as easy as finding where the stitch begins.

3. Overlock

Photo / video TBU

What it does: An overlock machine (also called a serger) closes unfinished seam edges by looping thread around the raw edge of the fabric, preventing fraying. Unlike a lockstitch, which sews through the fabric, an overlock wraps around it.

What it's used for: Inseam closure, side seams without selvedge, fly construction. Any raw edge that needs to be finished and secured.

Notes: We run two overlock machines at FITTED Underground. The first is a 5-thread overlock with a safety stitch — an additional chain stitch sewn alongside the overlock that adds structural reinforcement. The second is a shell stitch machine, which produces a more decorative, scalloped overlock finish. The shell stitch is the one that catches the eye on the interior of a well-finished pair of jeans.

4. Coverstitch

Photo / video TBU

What it does: A coverstitch machine produces a zigzag pattern stitch that binds two pieces of fabric together cleanly on both faces. Because the stitch has built-in stretch, it's also the standard machine for hemming knit fabrics — including t-shirts — where a rigid stitch would pop under tension.

What it's used for: Closing belt loops — folding the belt loop strip and joining the edges in a single pass. 

5. Bar Tack

Photo / video TBU

What it does: A bar tack machine is a specialized lockstitch machine that creates a dense cluster of stitches — 28 or 42 — in approximately two seconds. The result is a tight, concentrated block of thread that reinforces a single point under stress.

What it's used for: Securing belt loops at the waistband, and any other point on the jean that takes repeated stress — pocket corners, fly base, keystone. Wherever force concentrates, a bar tack or rivet will be found there.

Notes: We have a slight preference for the 42-stitch machine over the 28-stitch. More stitches mean more reinforcement. The difference in time is negligible — we're talking fractions of a second. 

6. Buttonhole Machine

Photo / video TBU

What it does: Creates and reinforces the buttonhole — stitching a dense perimeter around the opening that will withstand thousands of fastenings over years of wear.

What it's used for: The waistband and fly buttonholes. The most stressed single point on a jean — opened and closed every time the jeans go on or come off, for years.

Notes: There are two types of buttonhole machines: cut-before and cut-after. Cut-after machines — standard for denim — sew the reinforced keyhole shape first, then cut the opening. This sequence produces a stronger buttonhole because the stitching holds the fabric in place before any cutting occurs. It does leave some cut threads visible at the opening. These aren't defects. They're relics of a time when strength mattered more than a refined finish.

7. Waistband Machine

Photo / video TBU

What it does: A chain stitch machine — typically capable of running up to four needles simultaneously — that attaches the waistband to the pant body. A folder attachment folds and aligns the waistband as it feeds into the machine. A puller behind the needles draws the fabric through the folder smoothly and consistently.

What it's used for: Attaching the waistband. One of the most technically demanding operations in jeans construction — getting the fold consistent, the tension right, and the stitch even across the full circumference of the waistband requires both a well-set-up machine and a skilled operator.

Notes: We covered the construction detail of this operation in DU 403 — chain stitch on the bottom of the waistband, lock stitch on top. The chain allows slight stretch; the lock stitch holds the top edge flat against the skin. The folder and puller make that combination possible at any consistent level of quality.

8. Felling Machine

Photo / video TBU

What it does: The felling machine — also known as a lap seam machine — folds two pieces of fabric over themselves and stitches them flat, encasing the raw seam allowance inside the fold. The result is the flat-felled seam: clean on both faces, no exposed edges, no fraying possible.

What it's used for: Securing the yoke to the back panel and running the center back seam. Sometimes used for the inseam as well. The center back is the most technically demanding application — a flat-felled seam along the J-curve of the center back, through the yoke intersection, at up to sixteen layers of fabric. We covered what that means in practice in DU 403.

9. Kick Press

Photo / video TBU

What it does: A foot-operated lever press. You position the hardware — rivet, button, tack — and kick the lever with your foot to drive the press down with consistent, controlled force.

What it's used for: Attaching rivets and buttons. Every rivet on every pair of jeans passes through a kick press. Every button. Fast, precise, mechanical. No electricity required.

10. Industrial Iron

Photo / video TBU

What it does: Produces prodigious amounts of steam — far beyond what any home iron can generate — at consistent pressure and temperature.

What it's used for: Preparing pattern pieces before sewing — pressing seam allowances, flattening edges, creasing waistband fabric before it goes through the folder. And finishing the garment after sewing — the final press that sets every seam and gives the jean its shape before it leaves the workshop.

Notes: The iron is not glamorous. It is indispensable. A pair of jeans that hasn't been properly pressed looks unfinished regardless of how well it was sewn. The iron is what separates a workshop from a sweatshop.

Tension, Tension, Tension

An final note before we leave our machines behind: Before any machine will sew correctly, it has to be set up correctly. And the most important variable in any machine setup — the one that causes the most problems for beginners and the one that experienced makers check first when something goes wrong — is tension.

There are three types of tension to understand:

Top thread tension — the resistance applied to the upper thread as it feeds from the spool through the machine and down to the needle. Think of it like a small dog that doesn't want to go for a walk. There should be some resistance — enough to keep the thread taut and controlled — but not so much that the thread is fighting you.

Bottom thread tension — the resistance on the lower thread wound in the bobbin. This one should be much lighter — like a dog that does want to go for a walk. Easy, willing, minimal drag.

Presser foot tension — the downward pressure the presser foot applies to the fabric as it feeds through the machine. Too much pressure and you'll warp the fabric, pulling it out of alignment as it moves. Too little and the fabric won't feed consistently — it fishtails, like a car losing traction in the rain, skipping and sliding rather than moving in a straight line.

The best way to dial in presser foot tension: back it off more than you think you need to, then slowly increase it until the fabric feeds smoothly and straight. Start loose. Tighten incrementally. Trust what you feel more than what the manual says.

Tension is the thing every beginner ignores and every experienced maker checks first. Get it right, and the machine disappears. Get it wrong, and nothing else matters.

What Comes Next

DU 405 covers the machines. DU 501 steps back from the workshop and into the community — the people who wear, collect, and gather around raw denim, and what it looks like when that community comes together. That's DU 501: The Raw Denim Community.

← Previous: DU 404 — The Evolution of the Craft  |  Next: DU 501 — The Raw Denim Community →

Core Curriculum

Complete the core curriculum by reading these essential classes.

• DU 101 — What is Raw Denim?
• DU 102 — What is Selvedge Denim?
• DU 104 — Denim Weight Explained
• DU 201 — How to Buy Your First Pair of Raw Denim Jeans
• DU 204 — How Much to Spend on Raw Denim
• How It Works — FITTED Underground

Eric Steffen is the founder of FITTED Underground, a custom jeans and raw denim workshop at 108 Bayard Street in Williamsburg, Brooklyn. He has been making jeans by hand since 2014. Denim University is his attempt to share everything he's learned — about the history, the craft, and the culture behind the world's most enduring garment.