Frequently Asked Questions

Why should I get GearCalculators.com Software?

You could spend a lot of time looking around the internet, plus a lot of money joining a standards organization like AGMA, ISO, BSI or DIN, plus get a math and CS degree and still not get the powerful and useful calculators. When designing gears there are many things to consider like ratios, sizes, strength, lubrication, cutting tools, machine setup, inspection, and more. No one piece of software brings it all together like GearCalculators.com. Did you go to college and wonder why you only had 1 lecture on gears? GearCalculators are what the tools, knowledge and information would look like if it was a 2 year class on only gears.

Does GearCalculators.com show English and Metric Units?

Yes, all the calculators have dual output. The generators are written in Module. But you can easily convert to Pitch and the numbers are correct. Remember the conversion is simple: Module = 25.4/Pitch And Pitch = 25.4/Module

What are other professions that could benefit from GCS?

If you want to win F-1, your transmission needs to hit all the shift points-just right. Horologists and Space Navigators could use a little help with the ratio calculations – quickly please. Gear manufacturers could probably get their equipment to make higher quality gears with better finish -and- in less time. STEM teachers can build better higher quality students, they are curious-give them the knowledge. Inventors can design something extraordinary that is enabled by the combination of tools inside GCS. Solar Energy installations track the sun, most use a geared system to accomplish the movement. And there are many more. There is a person in a garage somewhere that is going to want this.

How did GearCalculators.com get started?

Our business was started on an optimistic fall day in October 2019. We have seen COVID, upturns, downturns, failures and successes. We started what has turned into GearCalculators.com out of necessity. We started from scratch, knowing nearly nothing about gears. Every time we hit a hurdle we would make an Excel Spreadsheet, then a calculator, and finally software. Then we would read, research, check standards, find other gear manufacturers and tune the calculators so that they were as useful as possible. But that was only part of the journey, we made gears with every tool we had and did a proper inspection. And these inexpensive and powerful inspection calculators are in our software. This allowed us to close the loop back to design. And then we repeated this loop every time we made gears and improved on the system. It got started because we needed to produce quality gears to make our living. Every tool is built to make our day easier at our desks and on the shop floor. The numbers are tested by mathematicians and engineers, the gears don't lie and are tested on the granite between NIST calibrated micrometers. The bigger test is done by our customers, who have all turned into repeat customers. There is creative mental effort and real physical sweat involved in our product development.

Who and what helped you the most?

Many very nice and intelligent people are in the gear business, the list is very long. Their advice and pointers have led the way. Our fantastic customers are also a huge driving force. They want high quality gears, they don't care how. The reality of due-dates, quality and quantity of product, payroll, rent, electricity and more force us to work efficiently. Gearcalculators is behind our ongoing success. We can't make every gear, but we can certainly help many others start making gears more confidently.

What are the new calculators we have not seen before on your website?

Feeds and Speeds for Hobbing: There is very little information on this important topic, not to mention a way to keep and record all of your recipes. There are recommended starting points for full manufacturing speeds, Scallop feed limits, hob material information, and a large selection of gear materials to choose from. Ratio Calculators: Given any ratio, determine the four change gears a,b,c,d (2-Stage). Limit these answers to the change gears available with your machine. Tolerance inputs guide the way to practical solutions. We did not solve NP-Complete, but we sure did optimize it to save you time. Go ahead and buy that old machine that makes the part you need and not worry about change gear calculation again. Profile Shift allows the designer to make a standard gear into a slightly larger or smaller gear. It is found on many of the calculators but is readily understood if you play with any one of our gear generators (.DXF, .STL, .SVG) that will draw the involute outline. If you can design it, you can now draw it, mill-hob-shape it, 3D print it, AND measure it. Carbide Worm Cutting Tool: Making a worm can be done on a lathe. The shape of the carbide depends on the pressure angle, pitch, module, circular pitch or TPI. With these inputs the carbide geometry such as tip flat, depth of cut and flank angles can be determined. Use your machine shop carbide grinder to make the cutter and you are set. The method works for both Manual and CNC lathes, Module, Pitch and Circular Pitch. Undercut Flag: This alerts the user to the small tooth pinion problem of undercut gears. Prime Flag: This alerts the user for every gear design if it is prime or not. Utility Calculators: Hardness converter, Shaft and Keyway standards (inch and metric), links to gear related NASA information and more.

What are the most exciting new calculators we have not seen before on your website?

Profile Shift: Profile Shift is a method to design more efficient gears with lower friction. It does not take special cutters or machinery and can be achieved with standard hobbing machines. The concepts are simple and lead to superior performance.

Does Gear Shop ERP provide a digital "Traveler"?

YES. The traveler can be viewed, and data input from IOS and other devices in the shop digitally. As long as you have WiFi, you can enter data right at the machine, CMM, inspection station etc.

Why so much focus on older manual gear manufacturing equipment?

The first CNC hobbing machine was shown at EMO in 1975, showing that CNC was slow to occur. This means that every gear made prior to 1975 was made on a manual machine with change gears. These machines are usually built to last, and can be rebuilt if required. Many of our calculator users have manual machines. Many of our new calculators like Feeds and Speeds, Profile Shift, Worm Carbide and others are helpful regardless of the type of machine you have Manual or CNC. Think about it, we went to the Moon in 1969 and the gears needed were built on manual hobbing and shaping machines.

Who is your most famous user?

You are. But if Archimedes was still alive, he would probably have a copy of GearCalculators.com So would the person that made the Antikythera Mechanism.

How are Pitch and Module related to each other, and what are their common units?

Yes. Module = 25.4/Pitch Module is in Millimeters (mm) Pitch is in Inches (in) but the variable is inverse of inches so the units are 1/inch

How are Pitch and Circular Pitch related to each other?

Circular Pitch = π/Pitch While the pitch can be easily converted, the tooth proportions, and other parameters do not convert normal machine hardware bolts to involute gear profiles.

Why don't gears follow thread nomenclature?

Good question and it has to do with history and math. But they can be converted to each other in a simple way, Threads per Inch = 1/Circular Pitch

Most of your calculators allow any number to be used for Pressure Angle, but there are really only 14.5°, 20°, 22.5° and a few others. Why?

True - those are some of the standards. But designers can design with non-standard custom parameter if it means extra performance, in the form of less weight, or increased strength. These designs are not standard in that they will require custom cutting tools, but they still are involute gears and all the good properties of gears still applies. The auto industry is consistently designing custom gears, usually to increase mileage. Here custom means they are still standard gears, but in a size that is not commonly made and stocked. So if you are willing to get custom hobs made and pay/wait for them, you will be rewarded. What parameters can be altered to ANY PRACTICAL NUMBER? Pressure Angle and Pitch/Module in particular will get you very specific design results.

Reference Profile: Which reference profile should I choose if I don't have a drawing convention specified?

Default to ISO 53 Profile A. It covers approximately 70 percent of new cylindrical involute gear designs and is the international standard for general and heavy engineering. If you are working in DP convention (1/inch), use AGMA 1003 Full-depth 20° instead — it produces geometrically equivalent results.

Reference Profile: My drawing specifies DIN 867. What do I select?

DIN 867:1986 is geometrically equivalent to ISO 53. The DIN 867 entry showing 1.25 / 0.38 / 1.0 maps to ISO 53 Profile A; the entry showing 1.25 / 0.30 / 1.0 maps to ISO 53 Profile B. The calculator treats them as aliases. You may select either label; the resulting tooth file is identical.

Reference Profile: My drawing specifies "ANSI B6.1 20° full-depth." What do I select?

ISO 53 Profile A in module convention, or AGMA 1003 Full-depth 20° in DP convention. ANSI B6.1-1968 is a withdrawn historical standard whose proportions match modern ISO 53 Profile A and AGMA 1003 20° full-depth at coarse pitch. The geometry is identical; only the unit convention and label differ.

Reference Profile: My module is 0.5 mm. Should I use ISO 53 or DIN 58400?

DIN 58400 Variant A (mn 0.1 to 0.6) is the appropriate choice for instrument, small-motor, and consumer-mechanism applications at that module. ISO 53 will technically generate valid geometry, but its proportions are not optimized for the small-z behavior typical at that scale. If your drawing or application is North American fine-pitch, use AGMA 1003 instead — but note that AGMA 1003 and DIN 58400 are not geometrically interchangeable. Note that DIN 58400 was withdrawn by DIN in 2016 with no formal successor; it remains the de-facto reference and is still widely used on legacy drawings, but for engineers wanting current standards-body coverage, see VDI 2731 (Micro gears — Basic principles).

Reference Profile: I have a vintage automotive transmission gear that won't mesh correctly with current full-depth cutters. What's going on?

Pre-1960s automotive transmissions and many older agricultural PTO drives used Fellows stub-tooth geometry, with addendum coefficient h*aP = 0.8 instead of the standard 1.0. The teeth are visibly shorter than full-depth teeth at the same pitch. Select "Fellows Stub (historical)" under the AGMA 1003 family group. The calculator displays a "no current standard" note next to this preset because Fellows stub is not contained in any current ISO, DIN, or active AGMA publication — it persists as a de-facto restoration reference.

Reference Profile: What pressure angles are supported?

The calculator supports 14.5°, 20°, and 25° pressure angles. ISO 53 and DIN 58400 are 20°-only by standard. AGMA 1003 supports all three. 20° is the modern default and covers the vast majority of applications. 14.5° appears in U.S. fine-pitch legacy drawings and pre-1950s designs; the figure was defined by Robert Willis (Principles of Mechanism, Cambridge, 1841) and propagated through American industry via Brown & Sharpe's gear-cutter catalogs. 25° is used for high-strength applications and where low tooth counts (z < 17) must avoid undercut without large profile shift.

Reference Profile: Can I do helical gears?

Yes. The reference profile defines the normal section of the basic rack. Helix angle is set at the gear-builder layer of the calculator pipeline, where it combines with the tooth file (which is itself helix-agnostic) to produce the helical gear body. All reference profiles work for both spur and helical gears.

Reference Profile: What about profile shift (also called addendum modification, x or X)?

Profile shift is a tooth-level parameter and is set in the tooth-builder layer. It applies to any reference profile and is supported as standard input (positive or negative). The calculator validates against undercut and tip-thinning limits and warns if the chosen x value violates them for the given tooth count and reference profile.

Reference Profile: Can I do internal gears?

Internal cylindrical gears with the same reference-profile families are supported in the gear-builder layer. The reference profile is the same; only the tooth-body construction differs (teeth pointing inward from the root cylinder).

Reference Profile: What about splines?

Splines are handled in the Evolvent Design ANSI B92.1 calculator (U.S. involute splines) and the ISO 4156 calculator (international involute splines). The cylindrical-gear calculator is for power-transmission gear bodies, not shaft-to-hub couplings.

Reference Profile: What about tolerances and quality grades (ISO 1328, AGMA 2015, AGMA Q-grades)?

Quality grade selection is a pair-level concern (it drives runout allocation, mounting tolerance, and backlash budget for a mating pair) and is handled in the pair-builder layer of the calculator, separate from the reference profile. Both ISO 1328 / AGMA 2015 grades and legacy AGMA 2000 Q-grades are supported, with cross-reference.

Reference Profile: Why are there four ISO 53 profiles A, B, C, and D?

ISO 53 specifies four basic rack profiles that share the same addendum (h*aP = 1.000) and pressure angle (αP = 20°) but differ in fillet radius and dedendum chamfer. Profile A has the largest fillet (ρ*fP = 0.380, lowest root stress); Profile B uses a standard fillet (0.300); Profile C has the smallest fillet (0.250, for tight-pitch tooling); Profile D has a deeper dedendum with chamfer for high-strength applications. Profile A is the recommended default for most general-purpose designs.

Reference Profile: What's the difference between topping and non-topping in DIN 58400?

A topping tool cuts both the tooth flanks and the tip (outside diameter) of the gear in a single operation. A non-topping tool cuts only the flanks; the tip is left at the diameter to which the blank was turned before cutting. Topping is more common in production fine-mechanics manufacturing because it eliminates a turning operation and tightens tolerance on the OD. Non-topping is used when the OD must be finished before tooth cutting (e.g., for assembly or fitment reasons).

Reference Profile: Is the calculator's ISO 53 implementation traceable to KISSsoft, GearTrax, or other commercial software?

No. The calculator's geometry is implemented directly from the source standards (ISO 53:1998, AGMA 1003-H07, DIN 58400:1984) and is independent of any commercial gear-design software. KISSsoft and similar tools may be used as cross-reference for sanity checking, but they are not the design authority. Where commercial software conventions diverge from the standards, the calculator follows the standards.