What Size Serving Thread Do You Need for a Peep Sight?

The Short Version

• Use wrapping cord (serving thread) with a thickness between 0.014 and 0.020 inches, with 0.015 inches serving as the most versatile size for compound bows.
• Threads thicker than 0.020 inches ride high on string strands and slide under vibration, while threads thinner than 0.014 inches can cut bowstring fibers like cheese wire.
• Always wrap above and below the peep sight (string aiming ring) to close the string split, then finish with a locked wrap through the outer perimeter groove.
• Never substitute household sewing thread, monofilament fishing line, or dental floss, as these materials stretch, snap, or slice through high-tension bowstrings.

Standard Thread Sizes and What the Numbers Mean

Wrapping cord for bowstrings is sized by its outer diameter, measured in decimal fractions of an inch. When you browse spools of cord, you see numbers like 0.014, 0.015, 0.018, or 0.021. These numbers tell you how thick the strand is when pulled straight. While a few thousandths of an inch sounds tiny, that tiny difference changes how the thread grips your bowstring.

For tying in a peep sight, 0.015 inches is the sweet spot for nearly every modern compound bow. Modern bowstrings are built from slick synthetic polyethylene strands. A 0.015-inch thread is narrow enough to settle into the natural valleys between those strands. When you pull the cord tight, it bites into the groove, creates high friction, and stays locked in place without shifting.

A cord sized at 0.014 inches works equally well, especially on smaller strings with fewer strands or peep sights with shallow channels. It packs very tightly, creates clean knots, and leaves no excess bulk on the string. This smaller profile helps keep your bowstring light, which prevents unnecessary loss of arrow speed.

Sizes between 0.018 and 0.020 inches work best for heavy-duty ties on thick, high-strand-count strings or peep sights with wide, deep outer grooves. These thicker threads offer high tensile strength and will not break when you haul back on your knots. However, they create thicker knots that take up more space along the string.

Avoid anything larger than 0.021 inches for peep installation. Heavy cords in the 0.025 to 0.030 range exist for building center servings where your arrow nock snaps on. If you try to use that heavy center-serving cord on a peep sight, the knots will be too bulky to sit flush inside the sight housing.

What Happens When You Pick the Wrong Thread Thickness

Using the wrong thickness causes two major problems: your sight slips out of alignment, or you cause permanent damage to your expensive bowstring. Understanding these risks will save you hours of tuning frustration at the archery range.

When you use wrapping cord that is too thick, the thread cannot wedge itself down between the individual strands of the bowstring. Instead, it rides high across the peaks of the fibers like a rope laid over logs. Because it cannot bite into the string structure, it relies entirely on surface friction against slick string wax.

Every time you pull the trigger on your release aid, violent shockwaves travel up and down the bowstring. Under that sudden whip of vibration, a thick thread quickly rattles loose. The peep sight will slide upward or downward along the string. A peep sight that moves up or down by even one sixteenth of an inch will move your arrow impact by several inches at twenty yards. If you are practicing how to use a bow sight, an unstable peep makes grouping your arrows impossible.

When you use wrapping cord that is too thin, the danger shifts from slippage to physical string damage. Cord below 0.012 inches acts like a fine wire. Bowstrings are drawn under sixty or seventy pounds of peak tension, pulling the string strands taut against the peep sight housing. If you tie down those strands with razor-thin thread, the high pressure forces the thin thread to slice across the softer string fibers.

Over dozens of shots, that sawing action shreds the outer strands of your bowstring. A cut strand weakens the entire harness, eventually requiring a complete string replacement. Thin cords also snap easily while you tie your finishing knots, forcing you to cut everything off and start over.

Step-by-Step Instructions to Tie and Lock Your Peep Sight

Tying in a peep sight takes patience, steady hand tension, and about fifteen minutes. Follow these six steps to lock your sight securely so it never budges in the field.

1. Relieve bowstring tension. Place your bow in a bow string clamping tool (bow press) to relax the string tension safely. If you do not have a press, you can use a plastic-coated string separator tool to spread the strands gently without scoring the fibers. Never use metal screwdrivers, keys, or pocketknives to separate bowstring strands.
2. Divide the string bundle evenly. Modern compound bowstrings consist of 20 to 24 individual strands, often split into two distinct colors. Divide the strands exactly in half. If your string has 24 strands, separate 12 to the left and 12 to the right. An uneven split forces the peep sight to twist sideways during your draw cycle.
3. Insert the string aiming ring. Slide the peep sight between the two separated bundles. Align the side channels so the string bundles seat smoothly in the grooves. Ensure the sight housing angles upward toward your eye at full draw. If you shoot a shorter axle-to-axle bow, such as a setup configured with a bow sight for Mathews bows, check that the sight angle matches your steep string angle.
4. Tie the lower and upper wedges. Cut a 15-inch piece of 0.015-inch wrapping cord. Start about one half inch above the top of the peep sight. Tie a secure constrictor knot or double overhand knot, then wrap tightly downward toward the sight. Lay each wrap flush against the previous wrap without overlapping. Once you reach the top edge of the peep housing, tie off the wrap with three alternating half-hitches. Repeat this entire wrapping process one half inch below the peep sight, wrapping upward toward the bottom of the sight. These two wedges pinch the string bundles together and prevent the peep from moving vertically.
5. Wrap the outer perimeter channel. Cut a 20-inch piece of wrapping cord. Wrap the cord directly into the circular groove running around the outside of the peep sight housing. Make three complete passes around the groove, pulling each pass firmly to lock the string bundles tight against the metal frame.
6. Lock, trim, and burn the tag ends. Finish the perimeter wrap by tying four alternating half-hitch knots behind the sight housing. Pull the knots snug with flat-nosed pliers. Snip the excess cord with sharp scissors, leaving about one eighth of an inch of exposed tag end. Carefully touch the flame of a lighter to the tag end to melt it into a rounded bead. Keep the flame moving and never allow the open heat to touch your actual bowstring fibers. The melted bead acts as a mechanical stopper that prevents the knot from pulling through.

Makeshift Materials You Should Never Put on a Bowstring

Online archery forums are full of suggestions for cheap, everyday items to tie in a peep sight. While these materials might work for an emergency shot in a survival situation, they create severe reliability problems on a compound bow.

• Dental floss: Floss is made of nylon or PTFE coated in slick wax. It feels like bowstring material, but it has high elasticity. Under the heat and vibration of regular shooting, floss stretches within twenty shots. Once it stretches, your peep sight will slide freely up and down the string.
• Monofilament fishing line: Fishing line is slick, stiff, and has zero surface grip. It cannot bite into the string fibers, causing it to slide under bow recoil. Monofilament also has hard, sharp edges under high tension that can cut right through soft polyethylene bowstring strands.
• Household sewing thread: Standard cotton or polyester sewing thread has very low tensile strength. It snaps the moment you pull a knot tight enough to secure a sight. Cotton also absorbs water from rain or morning dew, causing the thread to rot, weaken, and unravel while hunting.
• Superglue: Some archers coat their tying knots with liquid superglue to keep them from coming undone. Cyanoacrylate glue hardens into a rigid, brittle plastic. When the bowstring flexes during the shot, that hard plastic cracks and creates sharp, glass-like crystals that chew straight into your bowstring strands.

Safety Checks Before You Draw and Shoot

Before pulling your bow back to full draw, run through a few basic safety checks. A loose peep sight can shoot out of the string at high speed during release, creating a serious eye hazard.

Start with a close visual check under bright lighting. Look at the bowstring fibers right where they exit the top and bottom of the peep sight. The strands should look smooth and neat. If you notice fuzzy, severed, or pinched strands spilling out from beneath your wrapping cord, stop immediately. Frayed fibers mean the string has taken damage and must be evaluated by a technician.

Next, perform the thumb pressure check. Hold the bow firmly by the riser with one hand. Place your thumb directly on the metal peep sight housing and push upward toward the top cam with moderate hand force. Then push downward toward the bottom cam. A properly tied peep sight will not budge even a fraction of a millimeter. If the sight slips along the string under thumb pressure, your wrapping cord is either too thick or your knot tension is too loose. Cut the wraps away and start over.

Finally, draw the bow back in a safe direction with an arrow nocked, pointing at a target butt. Check your sight picture at full draw. The string aiming ring should sit perfectly circular to your eye without tilting to the left or right. If the aperture looks like an oval or sits sideways, the string strands were divided unevenly, or the string has developed twist.

If you see broken strands, if the sight refuses to rotate square to your eye, or if you do not own a proper bow string clamping tool to relieve string tension, do not force the installation. Take your bow to a local archery pro shop. An experienced technician has the specialized clamping tools and string jigs needed to fix alignment issues safely.

Helpful Tools to Make Peep Tying Easier

Working with fine cords under high tension can be tough on your fingers. A few basic accessories can make tying your peep sight much cleaner and faster.

A tension spool tool (serving jig) is one of the most useful accessories you can keep in your bow tuning kit. This handheld metal and plastic tool holds your spool of wrapping cord securely. It uses an adjustable tension knob so you can dial in the exact resistance you want. As you wind the cord around the bowstring, the tension spool tool keeps every wrap consistently tight without cutting into your fingers. Look for a tool made with durable metal rollers and smooth thread guides to prevent the cord from fraying as it leaves the spool.

Another helpful item is a string separator tool. This small wedge slides between your bowstring strands and turns sideways to hold them apart. It creates a clean working pocket so you can drop your peep sight directly into place without needing three hands. Choose a separator with a smooth, protective coating on the tip so it never snags or scratches the individual string fibers.

When shopping for wrapping cord, look for spools labeled as high-strength polyethylene or braided Dyneema in the 0.014 to 0.016-inch range. A good quality wrapping cord will have a light wax coating that helps the thread hold tight knots while resisting water and field dirt. Keeping a reliable sight setup is just as critical as choosing a dependable bow sight for treestand hunting, where cold weather and rough conditions will quickly expose weak knots.

1

- QI HUO JU - Archery Bow String Serving Thread

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  9.0
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Key specs2

Thread Diameter

0.015-inch 3-strand cord

Tension Tool Build

The 2.9-inch serving jig combines metal and ABS plastic to help you wrap cord tightly around the string without slipping.

Pros & cons32

Pros

• Includes 0.015-inch polyethylene thread that matches the ideal thickness for tying peep sights
• Features a 2.9-inch metal and ABS spool jig to maintain firm wrapping tension on string strands
• Generous spool length provides roughly 120 yards of three-strand wrapping cord

Cons

• Manufacturer specifies no product warranty coverage
• Does not include a bowstring separator tool to help part string strands

2

- QI HUO JU - Archery Bow String Serving Thread

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• ARS Mark

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  9.0
• Brand
  - QI HUO JU -

Key specs2

Spool Compatibility

The tension jig features a removable spool design, allowing you to reload new thread spools whenever you finish the included cord.

Thread Material

Water-resistant polyethylene

Pros & cons32

Pros

• Polyethylene 0.015-inch thread diameter fits compound bow peep sight grooves without excess bulk
• Serving jig allows easy tension adjustment to keep wraps tight during installation
• Spool can be detached and replaced once the included wrapping cord runs out

Cons

• Listing provides no warranty coverage from the manufacturer
• Separator tool is not included, requiring separate tools to part bowstring strands

3

VTurboWay Peep Sight Installer, Bow String Separator Tool, Archery Accessories,

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  8.8
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  VTurboWay

Key specs2

Tool Purpose

Designed specifically to separate bowstring fibers without requiring a bow press for basic peep positioning.

Included Hardware

Single separator tool only

Pros & cons32

Pros

• Slips directly between bowstring strands to make inserting peep sights simple
• Bright red color makes the tool easy to locate on a workbench or in a field pack
• Compact profile fits easily into pocket or small archery maintenance pouch

Cons

• Tool only, so wrapping thread and peep sights must be purchased separately
• Manufacturer listing omits exact metal or plastic material composition

4

Truglo Centra Peep Pro Durable Lightweight Effective Versatile Easily Attached

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  8.8
• Brand
  TRUGLO

Key specs2

Aperture Diameter

1/8-inch fixed opening

Alignment Design

The angled aluminum frame aligns with your line of sight at full draw, while the matte finish cuts down on field reflections.

Pros & cons32

Pros

• CNC-machined aluminum body provides rugged durability in outdoor hunting conditions
• Angled peep housing design promotes consistent alignment at full compound bow draw
• Matte black finish cuts down on unwanted glare while sighting your target

Cons

• Thread is not included, so you must supply your own wrapping cord to lock it in place
• Fixed 1/8-inch aperture size cannot be changed without replacing the entire sight

5

SOPOGER Archery 37/45 Hooed Degree Peep Sight Kit 6X 8X

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  8.6
• Brand
  SOPOGER

Key specs2

Aperture Options

• 1/8-inch aperture insert
• 3/32-inch aperture insert
• 1/16-inch aperture insert
• 3/64-inch and 1/32-inch inserts

Included Optics

Comes with a 4X or 6X clarifier lens to sharpen your view when aiming through a magnified scope housing.

Pros & cons32

Pros

• Hooded aluminum housing shields internal lenses and cuts out overhead light interference
• Includes five interchangeable aperture sizes ranging from 1/32 inch up to 1/8 inch
• Bundles a clarifier lens and bow serving string for peep installation

Cons

• Thread diameter is not specified on the listing and requires buyer verification
• Multiple small interchangeable lens pieces require careful handling during setup

6

- QI HUO JU - Archery Bow String Separator Tool

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  8.4
• Brand
  - QI HUO JU -

Key specs2

Separator Construction

Electroplated aluminum alloy

Kit Contents

Pairs a string splitter tool with 0.015-inch polyethylene serving cord, giving you both the separator and the wrap to tie your peep.

Pros & cons32

Pros

• Combines an electroplated aluminum string splitter with a full 120-yard spool of thread
• Provides 0.015-inch three-strand cord, matching the standard thickness for tying peep sights
• Protective tool coating helps reduce friction and strand wear when parting bowstring fibers

Cons

• Does not include a tension serving jig for mechanical cord wrapping
• Carries no manufacturer warranty coverage

7

SPG Archery Peep Sight, 1/4" 3/16" Aluminum Peep Sight or

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  8.4
• Brand
  SPG

Key specs2

Peep Sizes Included

• 1/4-inch aluminum peep sight
• 3/16-inch aluminum peep sight
• Dedicated string splitter tool

Groove Design

Radial exterior grooves seat bowstring strands neatly, helping the sight stay centered once tied.

Pros & cons32

Pros

• Includes two aluminum peep sights in 1/4-inch and 3/16-inch diameters
• Built-in radial grooves guide bowstring strands securely around the peep body
• Comes with a string splitter tool featuring a non-abrasive protective coating

Cons

• Does not include serving thread, so you will need to buy wrapping cord separately
• Convex interior design cannot accommodate clarifier lenses or custom screw-in apertures

8

- QI HUO JU - Archery Peep Sight Tubing, 1/4"

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  8.0
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  - QI HUO JU -

Key specs2

Alignment Style

Uses flexible rubber tubing connected to the bow cable to automatically rotate the peep straight toward your eye at full draw.

Sight Sizes

1/4-inch and 3/16-inch apertures

Pros & cons32

Pros

• Tubing design pulls the peep straight into alignment at full draw
• Includes both 1/4-inch and 3/16-inch tube peep options alongside a separator tool
• Separator tool allows strand parting without relying on a full bow shop press

Cons

• Serving thread is not included in the package and must be purchased separately
• Alignment tubing can dry out, stretch, or snap over prolonged outdoor shooting sessions

9

FENJANER Archery Tubing 3/16 Peep Sight, Bow String Separator Tool,

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  7.8
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  FENJANER

Key specs2

All-In-One Package

• 3/16-inch tubing peep sight
• Bowstring strand separator tool
• Spool of bowstring serving thread

Tubing Function

The attached tubing pulls the sight square on every draw cycle, preventing sight rotation issues on older or twisting strings.

Pros & cons32

Pros

• Complete starter setup with 3/16-inch tube peep sight, separator tool, and serving thread
• Rubber alignment tubing ensures the sight faces directly toward the eye when anchored
• Bowstring separator helps you slip the sight into the string core cleanly

Cons

• Serving thread diameter and spool length are not specified by the manufacturer
• Alignment tubing adds slight forward drag and requires routine inspection for wear

10

FENJANER Archery Tubing 3/16 Peep Sight, Bow String Separator Tool,

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  7.8
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  FENJANER

Key specs2

Target Aperture

3/16-inch hunting aperture

Listing Note

Verify whether one or two peep bodies are included upon receipt, as the packaging summary and title show conflicting quantities.

Pros & cons32

Pros

• Bundles a 3/16-inch peep sight, string separator tool, and tying cord in one purchase
• Tubing alignment eliminates peep rotation issues on strings without balanced twist
• Separator tool provides enough clearance to insert the peep without unstringing

Cons

• Listing title mentions two peep sights while package contents list one unit, needing verification
• Thread thickness is omitted from specs, so check diameter before tying deep grooves

Last update on 2026-10-02 / Affiliate links / Images, Product Titles, and Product Highlights from Amazon Product Advertising API

FAQs

Can I tie in a peep sight without a bow press?

You can tie the outer knots and perimeter wraps without a bow string clamping tool if the peep sight is already sitting between the string strands. However, you should never try to force a peep sight into a fully tensioned bowstring using bare fingers or sharp tools. Use a dedicated plastic string separator tool to spread the strands safely, or take the bow to a shop with a press.

How much wrapping cord do I need to tie a peep sight?

You will need about three feet of wrapping cord in total for a complete installation. Cut one 15-inch piece to tie the wedge above the sight, another 15-inch piece to tie the wedge below the sight, and a 20-inch piece for the outer channel wraps. Having extra length makes it much easier to hold tension while tying your finishing knots.

How do I know if my peep sight is sliding?

Check your arrow groups at your standard sight-in distance. If your arrows begin hitting consistently high or low without any changes to your sight pins, your peep sight may have shifted along the string. You can mark the string directly above and below the peep with a silver metallic marker to give yourself a quick visual reference for any movement.

Should I tie above and below the peep sight or just around the groove?

You should always tie above, below, and around the center groove for maximum safety. Tying only the center groove leaves the top and bottom wedges open, which allows the sight to slide under string vibration. Wrapping above and below pinches the string bundles together, locking the sight firmly in place for thousands of shots.