Gear train calculations for engineer's lathes.
• A 'change gear calculator'.
• Free online program.
• Calculates gear trains for any screw thread.
• Using the gear wheels that you own.
• Metric or imperial threads.
• Metric or imperial lathes.
• Metric/imperial conversion gears.
• Suggest a new gear to add to your set (Step 9)
• Extensive help file, & video tutorials(below).
• Red button to search the HELP file (Step 11).
• Gearboxes for various lathes are included.
• Custom gearboxes can be added (Step 10).
• Ask to have your lathe with a gearbox added.
• Calculate Feed rates, worm gears.
• Extra Apps:
• Thread specifications and tapping drill sizes.
• Create tables of cutting speeds.
• Taper turning calculations.
• Charts for hardness of materials.
• Color charts for hardening & tempering.
• Polygon Cutter gear ratios.
• Polygon cutter simulation.
• Hexagon or polygon dimensions calculator
• Electronic Leadscrew Calculations.
NO ADVERTISING,
NO COOKIES,
NO FEES
NO LOGIN
JUST VOLUNTARY PAYPAL DONATIONS
NEW ADDITION (May 2025)
• FORUM for comments, questions & suggestions
CHANGES (July 2026)
• 403 ERROR
Some web servers may occasionally display:
403 - You do not have permission to access this site.
This is not a security problem with RTGT.
It occurs when the web server rejects an unusually
long URL containing your current program settings.
I am redesigning the URL format for Version 40
to eliminate this problem.
Meanwhile, there is a work-around:
Start a new session by running the program again
and re-enter only the settings needed
for your current calculation.
Each different option you explore adds more
information to the URL, making it longer.
• Version 39 is seeing major upgrades internally.
and should be online in the coming weeks.
• Step 1 now has two steps to easily find your lathe.
• Step 1C has also been added for minilathe users.
• Step 3B added to enter gear ratios for feed rates.
CHANGES (2025)
• The program can recommend a new gear (Step 9).
• Filter out gears too large to fit your lathe (step 8).
• This intro can be displayed in multiple languages.
• Use compound pairs in the list of change gears.
• Calculate the dimensions of any polygon eg hexagon.
• HELP button to search the help file.
• Please contact me if you have any problems.
• Or just say Hi! I like to hear from users!
Need Help?: AED Lewis at g mail dot com
QUICK START GUIDE
• Enter your own data in steps 1 - 5 then RUN .
• Step 1 : Choose the brand of your lathe .
• Step 2 : has been divided into 3 easy steps:
• Step 2A: Design your gear train .
• Step 2B: Automatic Compound Gears on / off .
• Step 2C: Enter the gears you own .
• Step 3 : Choose what you want to calculate .
• Step 4 : Enter % error you can accept .
• Step 5 : use ONE pitch entry method below .
• Step 5A Enter the pitch or TPI, then RUN .
• Step 5B Make table of multiple thread sizes .
• Step 5C Look up standard threads(eg UNF).
• Step 6 : Click RUN to execute the program .
• return to menu . Alter any items . RUN again .
• Review the buttons below Step 6 RUN .
Title: Drilling and tapping a hole at 120º with a 4 jaw chuck on an engineers metal lathe (Boxford) Length: 12:11
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