In case you didn't know it, a calculator similar to this comes free with Microsoft Windows®. Just click on the "START" button, select "ALL PROGRAMS," then go to ACCESSORIES > CALCULATOR to bring it up. You use it just like a pocket calculator.

Sherline Gear Tooth and Thread Calculators

Joe Martin has developed a couple of calculators to help you with gear and thread calculations. They are in the form of Microsoft Excel* spreadsheets. Click on any of the links below to open these programs.




This Excel calculator will calculate the various dimensions needed to produce a helical gear. If the helical angle is set to "0" it will give you standard spur gear dimensions. I put it together primarily to calculate the amount of A-axis rotation needed to cut a helical gear using CNC. If you enable the Macro the program will generate the g-code that was written for a Sherline cnc mill. It may or may not work with other cnc machines. The Macro was written in 2005 using Excel 2002. On some newer computers it sometimes puts two lines on one line or leaves off the "n" and possibly the first number at the beginning of a line, but you can correct those errors by editing them yourself in Wordpad.

Instructions for use:

    1) When opening the program, select "Enable Macros" if asked.

    2) Enter the appropriate numbers for your desired gear in the pink cells of the chart

    3) Hit the [Enter] key after entering your new numbers

    4) Click on the "Create G-Code" box in the grey instructions cell

    5) Click "OK" in the box that says "End."

    6) If the g-code window in Wordpad loads behind the Excel window, you may have to minimize the Excel window in order to view it.

    7) Review the G-code to make sure all the lines begin with the letter "n" and the proper number. (Edit in Wordpad if necessary.)


This calculator is similar to the one above except it does not contain the macro needed to calculate helical gears.

*NOTE: You can get a viewer to open these programs even if you don't have Excel; however, the formulas and functions may not work. To get a free viewer, CLICK HERE.


(Microsoft ® Excel or Excel Viewer required to open and use. See above link.)

Enter a number in the appropriate box and hit [Enter]. Convert weights between kilograms, grams, miligrams, micrograms, pounds and ounces.

More Calculators

CONVERSIONS! This link from Machine Tools Online offers a number of handy conversion calculators for dimensions, time, money and more, or for dimensional conversions between systems, see

MORE CONVERSIONS for just about everything from fluids to currency:

MORE FREE CALCULATORS, formulas, conversions, cost of name it. See Cleave Books' Specialist Calculators page at

   Here's an interesting site with lots of handy software for the shop that has one major attraction...IT'S ALL FREE! Marvin Klotz has put up a page called "Home Shop Freeware - Tools for People Who Build Things" that includes a wealth of programs at for your use. It's worth looking over the list to see if there is anything that could help you solve a problem. I'll bet you find something you'll download. It's cool stuff and the price is right.

Frederik Rombach has come up with a neat little program that will help you calculate spindle speed/FPM for a number of material and cutter size combinations for the lathe, mill and drill press. CLICK HERE to download his small (348 kb) .exe program. Select the material from the top menu and enter the known values of cutter size and so on in the boxes. It's as easy as that. This program will run on any Windows-based computer with a Windows 98 or newer OS.

The Machinist's Friend® is a valuable utility program for Machine Shop Owners, Machinist, CNC Programmers, Metalworkers, Students, Engineers, or anyone else who needs to solve Trigonometry calculations. Also a great utility tool for cad or cad-cam users. This user friendly program is not only quick and easy to learn and use, but it aids machinists and other users who need accurate calculations of measurements for making machined parts. This is a program written by a machinist for machinists and is a must have for your electronic reference library.

(The above is quoted from their web site, 6/03. The site gives lots of examples and screen shots of how the program solves various problems like speeds/feed rates, bolt circles and chord lengths.)

Need a quick way to do trig calculations? See Just fill in the sides or angles you know and it does the rest.

 This link to CNC information comes from Robert Adams. He offers a tutorial on using a CAD program to help create a tool path at There are also links to software for the home shop machinist to convert a .dxf CAD drawing to a G-Code program. The whole package of software programming tools can be purchased for $29.95. The home page is at Bob's address or telephone are on his webpage. (Rev. 5/12/05)

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