The Leitech COMBI Calibration Master
The fastest, most foolproof way to calibrate your Standard or Hi-Resolution COMBI Gage. Dial in your thread pitch — the correct calibration length sets automatically. No calipers. No gage blocks. No guesswork.
Custom Leitech Gage Solutions — Your Problem Is Our Business
Standard gages solve standard problems. But precision manufacturing rarely stays standard.
Angled holes. Counterbores. Minimal clearances. Arc-formed bottoms. Hard-to-reach features. Deep blind holes in tight spaces. If your application has a thread or cylindrical feature that needs size and depth verification — and a standard gage won't reach it — Leitech can solve it.
Send us a sketch, a drawing, or a 3D model. Describe your challenge. Within days, we develop the solution.
Wear Shoe for Angled Measurements
The Leitech Wear Shoe allows accurate depth measurement on angled or radial surfaces — the sleeve references the correct datum regardless of surface geometry.
The Leitech Ball Measure System
Designed specifically for arc-formed or radiused bottom holes where a flat reference surface doesn't exist. The ball contacts the arc and provides a consistent, repeatable depth reference.
Special Wear Bushings
Designed for areas with minimal clearances. Multiple bushing profiles available to access confined features that standard sleeves cannot reach.
Measure Angled Holes
Oversize Wear Bushings
For applications requiring a larger reference surface or additional wear protection in high-cycle environments.
Special Wear Bushings
Designed for areas with minimal clearances. Multiple bushing profiles available to access confined features that standard sleeves cannot reach.
CUSTOM CAPABILITIES
Cylindrical COMBI Gages The same simultaneous size-and-depth principle applied to reamed bores, drilled holes, and precision cylindrical features. Core holes, plain bores, counterbores — verified for size and depth in one check.
Special Coatings Chrome, TiAlN, and DLC coatings for extended wear life in abrasive materials. TiAlN provides up to 10x wear life in aluminum and cast iron — the most common upgrade for automotive production environments.
Left-Hand Threads Available on request for any standard or custom size.
NPT and Pipe Threads Standard and custom configurations for pipe thread depth and engagement verification.
STI / Helicoil Threads Purpose-built members for thread insert inspection — verifying size and depth of STI threaded holes in one operation.
Contact us with your drawing, sketch, or description — we'll get back to you with a solution.
The Leitech Customized Concept: we cover the development costs. You pay only for the final solution. Tell us your problem. We'll build the gage. From a single tool to thousands — we have the flexibility and capability to deliver a precision solution in a manageable timeframe at an acceptable cost.
Why Turn-Counting Fails — And What to Do Instead
Ask a machinist how they check thread depth and there's a good chance the answer is "I count turns." It's fast, it requires no special tools, and it's been done that way for decades. It's also inaccurate, untraceable, and doesn't measure what actually matters.
Here's why:
Most thread depth specifications are called out from the part face — which typically includes the chamfer depth as part of the total functional engagement length. When you count turns, you're starting from whenever the gage first contacts thread — which may or may not correspond to the part face. The reference point is inconsistent, operator-dependent, and unverifiable.
The Leitech telescoping sleeve solves this by resting directly on the part face — flat or angled — giving you a direct reading from exactly the reference point the print calls out.
For applications requiring measurement from inside a counterbore or chamfer — at the precise location where full thread engagement begins — Leitech can modify the gage to measure from that exact datum. You get the actual length of thread engagement, from wherever your design requires it to start.
If a design requires measurement from a specific location, we build the gage for that location.
Then there's operator variability. One inspector counts 10.5 turns. Another counts 11. On a 1.5mm pitch thread, that's 0.75mm of difference — enough to fail an aerospace assembly or cause a fastener to bottom out in a medical device. And when an auditor asks for documented, traceable depth data? "I counted the turns" doesn't pass an ISO 1502 or AS9100 audit. There is no data. There is no traceability. There is no record.
The Leitech COMBI Gage solves all three problems simultaneously. The telescoping sleeve contacts the part face — not the chamfer — and delivers a direct numerical reading of functional thread engagement from the first full thread ridge. Every time. Every operator. Fully traceable.
Turn-counting is an estimate. Leitech is a measurement.
The Numbers Don't Lie: Real Results from the Manufacturing Floor.
45% Faster Inspection
A North American automotive supplier inspecting a complex V12 engine block — 99 threaded holes — reduced inspection time from 71 minutes to 39 minutes after switching to Leitech Standard COMBI Gages. Same operator. Same parts. One tool instead of two.
72% Less Gage Inventory
A precision machining facility covering a 16-valve cylinder head with 103 threaded holes replaced an entire drawer of fixed-depth gages with 7 Leitech Standard COMBI Gages. Fewer tools. Lower calibration costs. A leaner gage lab.
17% Machine Hours Reclaimed
Shops that tap 15-40% deeper than the blueprint requires — just "to be safe" — are wasting spindle time and tap life on every single hole. Precision depth monitoring at the machine eliminates over-tapping. One U.S. production facility calculated they were threading 374 meters of unnecessary depth per year on a 1,000-holes-per-day operation. That's real money.
These aren't projections.
They're what happens when estimation gets replaced by measurement.
Thread Depth Inspection Terms — Know What You're Measuring
Leitech and Quality Control
Leitech and Quality Control
Leitech and Quality Control
Precision manufacturing has its own language. Here are the terms that matter most when it comes to thread depth inspection — defined clearly, no engineering degree required.
Calibration Master or Setting Disc. Ensures the gage conforms to FED-STD-H28 and delivers traceable depth readings. Pitch Diameter The theoretical diameter of a thread where the width of the thread ridge equals the width of the groove. The primary dimension checked by the GO member — confirming the thread will accept its mating fastener.
Telescoping Sleeve The precision depth-measuring element of the Leitech COMBI handle. Spring-loaded, it contacts the part face as the GO member enters the thread — delivering a direct numerical depth reading simultaneously with size verification
Have a term you don't see here? Ask the Gage Guys. 414-333-6310 | tony@leitech.com .
Measurement Terms
Leitech and Quality Control
Leitech and Quality Control
Functional Thread Depth The measured distance from a specified datum point — typically the part face — to the end of useful thread engagement. This is the number your print calls out. This is what the Leitech COMBI Gage measures directly.
Thread Engagement The length of fully-formed, usable thread available for a fastener to grip. Starts at the first full thread ridge and ends at the last fully formed thread before runout begins. This is what holds your assembly together.
First Full Thread Ridge The reference point for all Leitech depth measurements. Per FED-STD-H28 and ISO 1502, thread depth must be measured from the first fully formed thread — not the chamfer, not the part face alone. Leitech GO members are manufactured to a strict 0.5 pitch tolerance from this reference point.
Calibration Length (X) The precise distance from the front face of the Leitech thread member to the zero-point on the measuring sleeve. Established using the Leitech
Gage Terms
Leitech and Quality Control
Data and Quality Terms
Go / No-Go Gaging The industry standard method for thread size verification. The GO member must enter the threaded hole freely to full depth — confirming the thread is not undersized. The NoGo member must not enter more than two turns — confirming the thread is not oversized. Leitech COMBI Gages perform both checks while simultaneously measuring depth.
Taperlock Design The method by which Leitech thread members attach to the handle. A tapered shank seats securely in the handle and can be removed using the Leitech Member Removal Sleeve when replacement is needed.
Member Removal Sleeve A specialized extraction tool used to safely remove worn Leitech thread members from the handle. Green for GO members, red for NoGo members. Allows renewal of the gage member while keeping the precision handle in service.
Functional Thread Size Verification that a threaded feature will accept its mating part to the correct pitch diameter. The Leitech GO member verifies functional size while the telescoping sleeve simultaneously measures depth.
Data and Quality Terms
Standards and Thread Types
Data and Quality Terms
Gage R&R (Repeatability and Reproducibility) A statistical measure of how much variation in your measurement results comes from the gage and the operator versus the actual part. The Leitech telescoping sleeve delivers the same reading every time — dramatically improving GR&R versus turn-counting or caliper methods.
NIST-Traceable A measurement that can be traced through an unbroken chain of calibrations to national standards. Required for aerospace, defense, and medical device quality audits. Every Leitech instrument is calibrated to FED-STD-H28 and ISO 1502.
SPC (Statistical Process Control) A method of quality control using statistical analysis of measurement data to monitor and control a manufacturing process. The Leitech Digi-COMBI and DMG output actual numerical depth values directly to SPC software via RS232 or wireless connection.
Process Terms
Standards and Thread Types
Standards and Thread Types
Blind Hole A threaded or cylindrical hole that does not break through the part. Accurate depth measurement is critical — fasteners must not bottom out before achieving full engagement.
Bottoming Thread / Bottoming Tap A tap ground with minimal chamfer, used to cut threads as close to the bottom of a blind hole as possible. Common in applications requiring maximum thread engagement in limited depth.
Over-Tapping The practice of tapping 15-40% deeper than the blueprint requires as a "safety margin." Wastes tap life, increases cycle time, and can weaken parts. Eliminated by real-time depth monitoring with a Leitech COMBI Gage.
Counterbore A cylindrical flat-bottomed hole that enlarges a portion of an existing hole. Thread depth measurement from inside a counterbore requires a modified Leitech gage configured to reference the correct datum — the precise location where full thread engagement begins.
Standards and Thread Types
Standards and Thread Types
Standards and Thread Types
UNC / UNF / UNEF (Unified Inch Threads) The most common thread standards in North American manufacturing. UNC (coarse), UNF (fine), and UNEF (extra fine) — all available in Classes 2B and 3B. Leitech COMBI Gages cover the full range from #2-56 through 1-5/16".
Metric / ISO Threads The international standard for metric threads, specified by ISO 6H tolerance. Leitech COMBI Gages cover M2 through M33 — the full range of metric thread sizes used in European and global manufacturing specifications.
JIS (Japanese Industrial Standard) Thread standard used in Japanese manufacturing and by Japanese-owned facilities and suppliers worldwide. Leitech COMBI Gages are available for JIS thread inspection — covering automotive, electronics, and industrial applications from Japanese OEMs and their North American suppliers.
NPT (National Pipe Taper) A US standard for tapered pipe threads used in fluid and gas connections. Leitech COMBI Gages are available for NPT and NPTF inspection, with 1-pitch and 4-step lines incorporated as standard features.
STI / Helicoil Thread A thread form used with helical wire thread inserts. Common in aluminum and soft material applications where thread reinforcement is required. Leitech produces COMBI Gages specifically for STI thread inspection.
Left-Hand Threads Available on request for any standard thread size and type. If your application requires left-hand thread verification with simultaneous depth measurement — Leitech can build it.
The Original. The Standard. The Future.
The authority in precision thread depth gaging for over 30 years, Leitech has been more than just a tool manufacturer—we are the architects of the thread depth gaging category. When we introduced the original COMBI system, we transformed inspection from a manual 'guesswork' process into a repeatable, NIST-traceable science.
Our History
In the early days of precision manufacturing, thread depth inspection was a guessing game. Machinists counted turns. Inspectors eyeballed depth steps. Quality labs accepted estimation as standard practice.
Then Leif Larsen of Leitech Instruments in Gilleleje, Denmark had a simple idea: what if one gage could verify thread size AND measure functional depth — simultaneously, in a single check, with a direct numerical reading?
That idea became the Leitech COMBI Gage. And it changed thread depth inspection forever. Leitech-US has been bringing that Danish innovation to North American manufacturers since 1989. Tony Thorson and Mike Thorson have spent decades introducing engineers, machinists, quality managers, and metrologists to a better way — one demo gage at a time.
Over 5,000 companies across the US, Canada, Mexico, and Puerto Rico have standardized on Leitech thread depth gages. From small precision machine shops to the largest automotive and aerospace manufacturers in North America — the reaction is almost always the same:
"Why didn't I know about this sooner?"
Where We're Going
Manufacturing is in the middle of a renaissance. Industry 4.0, smart factories, wireless data, automated inspection, AI-driven quality systems — the shop floor of tomorrow looks nothing like the shop floor of yesterday.
Leitech is ready for it.
The Digi-COMBI's wireless SPC output feeds directly into modern quality management systems. The DMG's standardized motorized torque integrates into automated inspection cells. And the core COMBI principle — simultaneous size and depth in one check — is more valuable in a data-driven manufacturing environment than ever before. Every thread.
Every hole. Every measurement. Traceable, digital, certain.
That's not just where Leitech is going. That's where precision manufacturing is going.
We're just already there.