The Authority in Precision Thread Depth Gaging | Leitech US
Directly Measure Thread Size and Depth
One Gage ... Two Measurements (COMBI=Size+Depth) ... Zero Guessing

The Authority in Precision Thread Depth Gaging | Leitech US
One Gage ... Two Measurements (COMBI=Size+Depth) ... Zero Guessing

Leitech COMBI Gages are the precision standard for thread depth inspection
in automotive, aerospace, medical, and industrial manufacturing.
Milwaukee, WI — serving North America since 1989.
As the GO member verifies functional thread size, the telescoping sleeve delivers a direct numerical depth reading — simultaneously. No counting turns. No secondary tools. No estimation.

THE PROBLEM:
Traditional thread depth inspection is a bottleneck. Machinists check size with a standard plug gage, then estimate depth by counting turns, eyeballing depth steps, or reaching for a secondary depth mic. The result: inconsistent data, operator fatigue, and zero traceability for the modern quality lab.
THE SOLUTION:
Leitech COMBI Gages. One insertion verifies functional thread size AND delivers a direct numerical depth reading — simultaneously. No estimation. No second tool. No guesswork.
THE SYSTEM DELIVERS:




Built for aerospace, medical, and defense components where depth tolerance is a compliance requirement, not just a quality preference. 0.1mm / 0.005" resolution with a unique locking device that freezes the depth reading — so you capture the value in a confined space and read it once the tool is removed. Calibrated to FED-STD-H28. NIST-traceable from day one. When "close enough" means a failed audit, this is the instrument.
0.01mm / 0.0005" LCD readout. RS232 and wireless output. Direct integration into your SPC system — no manual entry, no transcription errors, no paper logs. Eliminates parallax error and operator subjectivity. Toggles between metric and inch instantly. Built for Industry 4.0 shops that need a complete digital audit trail for every threaded hole. This is thread depth inspection for the modern quality lab.
Standardized motorized torque. Every insertion. Every shift. Every operator. No variability. Built for high-volume production lines where manual gaging creates fatigue, inconsistency, and GR&R problems. The DMG combines the speed of power-driven thread gaging with the precision of a calibrated Leitech instrument. Size and depth. Simultaneously. At production speed.

The instrument that started it all. 0.5mm / 0.025" resolution. Spring-loaded telescoping sleeve. Direct numerical depth reading the moment the GO member enters the hole. Replaces entire sets of fixed-depth gages. One tool covers variable depths across multiple parts and multiple thread sizes. No turn-counting. No depth mics. No estimation. This is the gage that changed how manufacturers think about thread depth inspection.
The best demo is in your hands. Ask us about a free demo gage in your exact thread size — we'll send it to you. No obligation.
In precision manufacturing, a thread that is "close enough" is a failure. Here are the questions every Quality Engineer, Machinist, and Metrologist needs answered.

The Leitech COMBI system — every precision thread depth inspection challenge, solved.
The Leitech COMBI Gage performs both measurements with one tool. As the GO member verifies functional thread size, the telescoping sleeve rests against the part face and delivers a direct numerical depth reading — simultaneously. No turn-counting. No secondary tools. No estimation.
Functional thread depth is the actual usable thread available for fastener engagement, measured from the first full thread ridge. It is not the same as the physical depth of the drilled hole. Insufficient functional depth causes fasteners to bottom out before achieving full engagement — a critical failure point in aerospace, automotive, and medical assemblies.
Blind holes are where traditional methods fail most. Counting turns is an estimate. Depth mics require removing the part. The Leitech COMBI telescoping sleeve automatically contacts the part face as the GO member enters the thread — giving you a repeatable, NIST-traceable depth reading without removing the part or switching tools.
NIST-traceable means your measurement can be traced back through an unbroken chain of calibrations to national standards. Every Leitech instrument is calibrated per ANSI/ASME B1 and FED-STD-H28 from the first full thread ridge — making your depth data audit-ready for compliance.
Fixed-depth step gages require one tool per depth requirement — which means dozens of gages, dozens of calibration cycles, and a cluttered gage lab. One Leitech COMBI measures any depth within its range for that thread size. Worldwide manufacturers have reduced gage inventory by up to 72% after standardizing on Leitech.
Yes. The Leitech Cylindrical COMBI provides the same simultaneous size-and-depth measurement for reamed bores, drilled holes, and precision cylindrical features. Same one-operation principle — functional diameter verified, actual depth read, in a single operation.
Indefinitely. When the GO thread member wears, you replace the member — not the handle. The depth-reading handle stays in service permanently. Using the Leitech Calibration Master or Setting Discs, the scale is reset and the gage is renewed in minutes. This renewable design reduces long-term tool costs by up to 60% compared to replacing entire gages.
The Leitech COMBI system measures functional size and actual depth simultaneously — for both threaded and cylindrical features. Threaded holes: Tapped blind holes, bottoming threads, STI/Helicoil inserts, NPT and pipe threads, metric and unified inch threads in any standard. Cylindrical holes: Reamed bores, drilled holes, precision cylindrical features — same one-operation principle, same direct numerical depth reading.
If it's a precision hole in a machined part, Leitech measures it.
Size and depth. One check. Done.

The Old Way:

The Leitech way: one COMBI gage.
Checks every depth of that size — directly, numerically, traceably. Same thread size. Variable depths. One tool.

The result: a leaner gage inventory, lower calibration overhead, and zero redundant tooling waste.

Simultaneous Size and Depth Measurement: Threaded or Cylindrical Holes
As the GO thread member enters the feature, the internal telescoping measuring sleeve automatically rests against the part face, providing a direct numerical depth reading. This single-operation approach eliminates the need for separate depth micrometers or the unreliable practice of counting turns or eyeballing depth steps.


The Variable-Depth Advantage:
Whether inspecting threaded features or cylindrical bores, the Leitech COMBI ensures a perfect assembly fit every time. By verifying functional size and actual depth simultaneously in one fluid motion, you eliminate the need for separate depth micrometers and the unreliable "counting of turns."
Experience a leaner Gage Lab. Because one Leitech COMBI measures variable depths for its specific size, a single tool can replace an entire set of traditional fixed-step gages. This drastically reduces calibration overhead and ensures you always have the right tool for any part depth on the print.
Elevate your process with the Digi-COMBI and DMG-Motorized series. These Industry 4.0 solutions offer high-resolution LCD displays and wireless data transfer, allowing you to capture actual numerical values for real-time SPC logging and 100% digital traceability.


















Q: What is the most efficient way to measure functional thread depth?
A: The Leitech COMBI Gage performs a functional size check and delivers a direct numerical depth reading in a single operation, eliminating the need for separate depth micrometers or unreliable turn-counting methods.
Q: How do you inspect and verify the depth of a tapped blind hole or bottoming thread?
A: The Leitech COMBI utilizes a precision telescoping sleeve that automatically rests against the part face as the GO member enters the thread. This provides a repeatable, traceable measurement of functional thread engagement depth for the fastener, preventing assembly failure and bottoming-out.
Q: What is "functional thread depth" and why does it matter?
A: Functional thread depth is the actual usable thread available for fastener engagement, measured from the first full thread ridge. Unlike nominal depth (which only measures to the bottom of the hole), functional depth ensures assembly safety and prevents fastener bottoming-out failures.
Q: Can I use Leitech gages for cylindrical holes?
A: Yes. System Leitech provides the same "Size + Depth" efficiency for cylindrical features as it does for threads. Our Cylindrical COMBI Gages verify the functional diameter of reamed, bored, or drilled holes while simultaneously capturing a direct numerical depth reading.
Q: How does Leitech reduce gage inventory costs?
A: Unlike fixed-step gages that only check one depth, the COMBI's telescoping sleeve measures variable depths directly. One tool replaces an entire set of fixed gages for that thread size.
Q: How much faster is Leitech compared to traditional methods?
A: By combining size and depth verification into one operation, Leitech reduces inspection time by approximately 50% compared to using separate gages or counting turns.
Q: What tool is used to measure thread depth?
A: The most efficient and accurate tool for measuring functional thread depth is the Leitech COMBI Thread Depth Gage. Unlike traditional methods that require separate gages or unreliable "turn counting," the Leitech System performs a functional size check and delivers a direct numerical depth reading in a single operation. This "One Tool, Dual Measurement" approach is the global industry standard for precision manufacturing.
Q: How do you check the depth of a thread accurately?
A: To check thread depth accurately, you must measure the functional thread engagement rather than just the nominal hole depth. Using a Leitech COMBI gage, the internal telescoping sleeve automatically rests against the part face as the "GO" member enters the thread. This provides a repeatable, NIST-traceable measurement of the usable thread available for fastener engagement, eliminating "operator feel" and parallax error.
Q: What is the rule for thread depth in precision machining?
A: The fundamental rule for thread depth is ensuring enough functional engagement to meet the load requirements of the fastener without bottoming out. According to ISO 1502 and ASME B1.2 standards, this must be measured from the first full thread. Leitech gages are engineered specifically to this rule, with the measuring scale calibrated to the first full thread ridge (held to a strict 0.5 pitch tolerance) for absolute compliance.
Q: Is the Leitech COMBI system compliant with FED-STD-H28?
A: Yes. The Leitech system provides full conformance to FED-STD-H28, Section 6A. The crest of the first full thread on Leitech GO members is held to a strict 0.5 pitch tolerance (+0 / -0.06 pitch) from the front face.
Q: What is the difference between "functional depth" and "nominal depth"?
A: Functional depth measures the actual usable thread available for a fastener to engage, accounting for the thread lead-in. Nominal depth simply measures to the bottom of the hole. Leitech gages are calibrated to provide functional depth—the measurement that matters for assembly integrity.
Q: How do I eliminate "operator feel" variability in thread gaging?
A: The Digital Motorized Gauge (DMG-COMBI) uses a motorized handle to apply standardized, consistent torque for every measurement, completely removing operator variability from the inspection process.
Q: How much time can be saved using a Leitech COMBI gage?
A: On average, the System Leitech reduces inspection time by 45% to 50%. By consolidating size verification and depth measurement into one single step, shops reclaim significant machine capacity and reduce labor costs in high-volume production environments like Automotive and Aerospace.
Q: Can one Leitech gage replace multiple fixed-limit gages?
A: Yes. Because the Leitech COMBI features a variable telescoping scale, one single tool can measure any depth within its range for that specific thread size. This allows manufacturers to reduce their gage inventory by up to 72%, as they no longer need to stock multiple "step gages" for different part numbers.
Q: How do I calibrate a Leitech COMBI Gage?
A: Calibration is performed using the Leitech Calibration Master to establish a precise, pitch-based Calibration Length (X). By adjusting the telescoping measuring sleeve to this traceable constant, Quality Manufacturing Managers ensure 100% measurement accuracy. This repeatable process guarantees that your thread depth data remains compliant with ISO/IATF and FED-STD-H28 international standards.
Q: Can I integrate Leitech gages into an automated SPC system?
A: Yes. The Digi-COMBI and motorized DMG-COMBI are engineered for Industry 4.0 integration, featuring RS232 and wireless data output for real-time SPC (Statistical Process Control). By transmitting actual numerical depth values directly to your quality software, these gages eliminate manual data entry errors and provide the 100% traceability required in modern, high-precision manufacturing.
Q: Can one Leitech gage measure different thread depths of the same size?
A: Absolutely. This is the core of Leitech Inventory Efficiency. Unlike traditional fixed-step gages that only verify one pre-set dimension, a single Standard COMBI Gage utilizes a telescoping sleeve to provide a direct numerical reading of any depth within its range. This allows Gage Labs to replace an entire set of several gages with one universal tool, significantly reducing calibration costs.
Q: Can Leitech gages be used in automated robotic inspection cells?
A: Yes, the DMG-COMBI (Digital Motorized Gage) is specifically designed for robotic automation. It features variable speed settings and wireless data transmission, but its greatest advantage is standardized motorized torque. By eliminating "operator feel" and providing consistent measurement force, the DMG-COMBI ensures maximum GR&R (Gage Repeatability and Reproducibility) in 24/7 automated production environments.
Q: Are Leitech thread gages repairable or renewable?
A: Yes. Unlike standard gages that must be scrapped when the "GO" end wears down, the System Leitech features Replaceable Inserts. Using our specialized Removal Sleeves, a worn insert can be swapped out in seconds, essentially renewing the tool at a fraction of the cost of a full replacement. This "Renewable" design is what makes Leitech the most cost-effective long-term solution for Tier 1 suppliers.
Q: Does Leitech offer solutions for non-threaded holes? A: Absolutely. The Cylindrical COMBI Gage provides the same "Size + Depth" efficiency for reamed, bored, or drilled holes. It allows for the simultaneous verification of hole diameter and functional depth, ensuring total quality control for every precision-machined feature.
A threaded or cylindrical hole that does not break through the part. Accurate depth measurement is critical here to prevent fasteners from bottoming out before achieving full engagement.
The actual usable length of thread that can accept a fastener, measured from the first full thread ridge. Unlike nominal depth, this ensures sufficient engagement to meet load requirements.
Dual-purpose measurement for non-threaded features like reamed bores or precision-drilled holes. System Leitech provides the same one-operation efficiency for these features as it does for threads.ads.
The specific reference point for Leitech depth measurement. A telescoping sleeve rests on the part face to provide a direct reading of this dimension while the GO member simultaneously verifies pitch diameter size.
The precise distance from the front face of the thread member to the zero-point on the measuring sleeve. This value ensures the gage conforms to FED-STD-H28 and international standards.
Inconsistency in results caused by different individuals applying varying force. The DMG-COMBI eliminates this variable through motorized, standardized measurement force.
Unlike "Go/No-Go" gages that provide only a binary pass/fail result, Leitech delivers a direct numerical reading. This data allows for precise CNC tool-offset adjustments based on quality audit-ready data.
Specialized extraction tools used to quickly and safely remove worn inserts from the Leitech handle. This allows you to renew the tool indefinitely, minimizing physical waste.
The verification that a threaded feature will accept its mating part. A Leitech "GO" member verifies size while the integrated sleeve simultaneously measures depth in one fluid motion.
A core benefit where a single variable-depth COMBI gage replaces a set of numerous traditional fixed-step gages. This significantly reduces Gage Lab overhead and calibration costs.
The elimination of operator subjectivity—such as "counting turns"—in thread inspection. Leitech provides a repeatable, data-driven process that ensures every feature meets exact engineer specifications.
Tool Longevity (Sustainable Metrology)

Stop guess and start measuring! From the standard workhorse to motorized automation, there is a Leitech COMBI solution designed to bring 100% metrological certainty to your shop floor.
Contact us today for a quote or a live demo of the COMBI system.
Authorized Master Distributor and Technical Support for the USA, Canada, Mexico and Puerto Rico.
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