Understanding gear trains, feed rates, metric and imperial threads in an engineers metal lathe.
Vložit
- čas přidán 29. 11. 2019
- WATCH THE NEW VERSION BELOW:
• Understanding Gear Tra...
Since this video was so popular I have produced a NEW version in 2023 called 'Understanding Gear Trains for Engineer's Lathes', with better graphics and production.
This video explains how to calculate gear ratios in the gear train of a small engineers' lathe and includes the thread cutting and power feed gearbox that drives the lead screw. Certain gears in the gear train, known as 'change gears' can be switched to produce different lead screw speeds.
This video includes the use of a compound gear for converting a lathe with an English Imperial lead screw (eg 8 threads per inch) to metric, and also shows how to calculate power feed rates for the cross slide and longitudinal movement of the carriage. It is all explained using sketches on a whiteboard and basic arithmetic.
To cut metric threads with an imperial lathe you need a compound gear described here. The standard compound gear has a 127 tooth gear connected to a 100 tooth gear and this gives the most accurate metric conversion (127/100 x 2=2.54 cm/inch), but there are alternative combinations with small errors including 80 to 63 teeth, 47 to 37, and 56 to 44 teeth.
I have devised a simple method for calculating the threads and feeds using the gearbox and change gears. This is described in the comments attached to the video. Check it out!
If you need to calculate the gears required to cut a particular thread, try my free online computer program, but this video will give you a better understanding of how these calculations are done.
The online program:
RideTheGearTrain.com
• Mini Lathes-Tutorial-1...
• Tutorial 1B for users ...
• Tutorial for RideTheGe...
Playlist:
czcams.com/users/evanecentpla...
Boxford Users Group:
groups.io/g/BoxfordLathe-User...
Patreon:
Consider supporting this channel on Patreon: / evanecent
SOME LINKS
See the Playlist for engineers lathe.
• Introduction to "How t...
/ evan-e-cent
• Stainless Steel Wine B...
• Understanding the scre...
• History of the screw c...
• Understanding the Poly...
• Metric Imperial Conver...
• Understanding Gear Tra...
• Soft Jaw Self Centerin...
• Tangye Engine #1
• Grinding & Milling Att...
• Spindle Clamp -If you ...
• Making an ER32 collet ...
• Need a T-Nut for your ...
• Decorative Bolts for S...
• Demonstration of Atmos...
• Animations of Beam Eng...
• Stamper batteries used...
• Tutorial for RideTheGe...
• Tutorial 1B for users ...
• Mini Lathes-Tutorial-1...
• Making a hexagonal die...
• How to produce cams on...
• Cutting Keyways on a l...
• Designing a cam for a ...
• A cheap surface plate ...
• How to turn a metric t...
• How to use a ball turn...
• Make a ball turning at...
• Restoration of old gol...
• Art in Stainless Steel
• Restoring an electric ...
• A Small bronze bell pr...
• Machining a Modificati...
• Assembling the lathe h...
• Motor Speed Control El...
• Super T Link Belt to d...
• Motor Replacement Boxf...
• Indexing to mark punch...
• Milling a slot with th...
• Pressure Mounting disc...
• Milling a curve using ...
• Chuck offset posts wit...
• Mount thin discs with ...
• Stamper Batteries-How ...
• Stamper Batteries Abri...
• Pouring white metal Ba...
• A left-hand internal a...
• A left-hand internal a...
• Living with backlash i...
• Backlash- A simple top...
• A flaring tool to use ...
• Chuck dismantling & as...
• Quick change tool pos...
• Annealing copper discs...
• Hero's steam engine li...
• Make a rear mounted cu...
• Milling attachment for...
• Making a lathe indexin...
• Turning a taper by the...
• History of Steam Engin...
• Four Jaw Chuck and Dia...
• Steam Indicator Use an...
• How to wire a reversin...
• Lathe head reassembly ...
• Overhaul of the lathe ... - Věda a technologie
Your videos are by far the best about Lathes I have seen on CZcams and your gear train calculator is incredible, thank you.
Thank you ! Actually I made a new version which I think is much better. I put the link in the show notes (above) with the heading WATCH THIS NEW VERSION. I hope you like that one even more!
Bom trabalho, sua máquina é muito parecido com outro fabricante do Brasil , de nome SANCHES BLANES, torno mecânico muito estável, confiável é uma máquina duradoura.
Since making this video I devised a relatively simple method for calculating threads per inch (TPI) for imperial threads, or pitch (P) for metric threads on an imperial Boxford lathe. I have assigned the following numbers to the lever positions on the gearbox. Multiply these together to get the gear ratio of the gear box F. This is the number of threads per inch using a stud gear with 20 teeth and lead screw gear with 56 teeth (standard setup):
SUMMARY:
F is the gearbox factor (gear ratio) which is the value assigned to the lettered lever multiplied by the value assigned to the numbered lever on the gear box.
LETTERED LEVER VALUES
A B C D E
1 2 4 8 16
NUMBERED LEVER VALUES
1 2 3 4 5 6 7 8
8 9 10 11 11.5 12 13 14
For imperial setup with a standard 20 tooth stud gear the threads per inch is F. The standard lead screw gear has 56 teeth and usually it is not necessary to change it.
If you use a different stud gear:
TPI = F x 20 / T
T=teeth on stud gear
F= Letter value x Number value
P=Pitch
TPI =Threads per Inch
P = 1 / TPI so
P = T / 20F
METRIC Conversion
(Using the compound conversion gear and lead screw gear):
P = T / F
F = T / P
Review the above letter and numbered values to find a combination that matches T/P where T is the number of teeth on one of the gears you have available.
Power Feeds:
Transverse feed = P /10
Longitudinal Feed = 3 x Transverse feed = 0.3 P
i try to understand but .........how could I read all these?
@@sotiristheodoropoulos7750 How can I help? My video isn't great. I had problems with fluorescent lights reflecting off the white board.
The basic principle is like this:
If you have a gear with 100 teeth driving a smaller gear with 50 teeth the small one will have to turn twice to make 100 teeth go past, while the big gear only has to turn once for 100 teeth. So the smaller gear goes twice as fast as the big gear.
If you use my online computer program mentioned in the next comment you may not need to understand the detail.
@Evan Lewis
Dear friend, you helped me a lot.
I did not know where to look for, but with your excellent videos and your mail I can say now that I have understood largely to extent the operation of gear box
However, according to the table that is on my lathe gearbox (I attach the table to you)
If i want to make an imperial thread- as you wrote to me- with 10 threads per inch you find it in column 5 and row A so you set the gearbox levers to A but I thing is A3 according to the table on my lathe gearbox.
so the first lever (letters) On A and the second lever (numeral) in number 3.
what happens? I have mistaken? I have not understood well?
Yours sincerely
Theodoropoulos sotiris
Thank you mr evans thank you.
You help me a lot .
I will try all theses.
You have 'open invitation ' for Athens
You help me again
Online Free Computer Program to Calculate Gear Trains for Screw Cutting: I have used the equations described here to write an online computer program to help engineers work out the best gear train for cutting threads. It was originally designed for owners of South Bend clone lathes such as Boxford, but there are many others. see RideTheGearTrain.com . I have also made CZcams videos about the program and how it works. It appears later in this playlist.
Sir , I have gear stud 20 & any 80 , 63 , and ls 56 . can it make to matrik . I look table diagram gear . what is standar for make drat matrik.
Does the rpm affect too ?
I am have lathe tipe A boxford 4 1/2inc presision with gearbox . I want to make matrik but the gear that I have 20 , 40 ,80 . what should i do and what gear do i need add. Thanks
YES YOU CAN CUT METRIC THREADS WITH THE 63 TOOTH GEAR.
NO THE RPM DOES NOT AFFECT IT. (You set RPM with the pulleys and back gear).
I know English is not your first language and this may be difficult for you to read. Please contact me by email if you need help. See my email in my online computer program 'Quick Start Guide': I suggest you use my online program called RideTheGearTrain dot com. It does not cost anything. I will set up the program for your lathe and send you a link (URL) with all the data for your lathe.
You can make up a gear train like this and cut any metric thread:
20 tooth stud gear driving the 80 tooth gear.
The 80 tooth gear is connected to the 63 tooth gear as a compound pair - both on the same shaft.
The 63 tooth gear then drives the 56 tooth gear which is on the "leadscrew gearbox input shaft' which I call LSG. Then use the program to find out what gearbox setting to use.
Later, you can still cut imperial threads by using this compound pair as an idler. Use the 80 tooth idler. The 63 tooth gear may still be connected to the 80 tooth gear but does not mesh with any other gear for imperial inch threads.
I just ran 'RideTheGearTrain' and asked for a 1mm pitch thread. It told me a much simpler gear train:
20 tooth stud gear
driving the 80 tooth idler gear (not compound)
63 tooth LSG gear (on the leadscrew gearbox.)
Set the gearbox to B5 for a 1 mm thread.
How to use my online program called RideTheGearTrain dot com. It does not cost anything.
In step 1 the program asks what lathe you have:
Step 1: Scroll down to 'Lathes with gearboxes' and you will find 'Norton Imperial'. Your Boxford A lathe will have the Norton Imperial gearbox. It is the same as my lathe. Click the red button so it turns green. Then click the 'RETURN' button on the screen.
In Step 2 select 'One compound gear' and enter your list of gears. In your case it may be easiest to put all your gears in the list of 'change gears' and choose 'automatic', then ignore the compound gears.
In Step 3 Select 'Metric Thread'.
In Step 4 you choose how much error you are willing to accept. Usually 0.5% is OK but you could go up to 2%.
In step 5A you enter the pitch of the thread in mm.
In Step 6 click RUN and it will tell you many different ways you can set up the gear train and gearbox to cut that thread.
Click DRAW and it will show a drawing (a scale diagram) of the gear train.
The main gear you have has 63 teeth. Two times 63 is 126 which is nearly the same as the 127 tooth gear used for metric on an imperial (inch) lathe. 127 times two is 254 and there are 25.4 mm in one inch! So it is common to use this 63 tooth gear for metric.
You may need to make a compound pair of gears by connecting two gears together so that they spin on the same shaft. One of the gears must be the 63 tooth gear. The second gear usually has 100 teeth, but you can use any other gear. These two gears are usually joined together eg using a key or rivets etc so that they turn together. If you only have the 80 tooth gear this will work, but if it is an idler gear on the Boxford it has the wrong size hole in the center. The hole is bigger than the 7/16" hole with a keyway that the other gears have. It is designed to spin freely on a bush. You may have to make a bush that allows you to join 2 gears.
Thanks You
you are welcome!
Thanks sie
Dear friend
Thank you for immediate response
Im teacher in athens ,Greece andI assure you your presentation was excelent but initially my knowledges as mechanic ( i am teaching electric in technical school,the lathe is my Hoby) and second my English language are my problems.
I bought a boxford class A 8TPI two years of ago in bad condition .today after reconstruction looks like as new.
I am tryig to learn tread in metric system but it is difficult for me to understand the numeral table on lathe on norton box.for example
what does mean two numbers in every divisions ?
what position i need to put levers on norton box?
Sorry I don't speak Greek and I hope this is not too long for you to read. Since you are in Athens, you might be interested in my web page about Heron of Alexandria's Steam Engine, but it has nothing to do with lathes. www.HeroStreamEngine.com.
I don't know whether the label on your gearbox is original or changed. The original one was copper. I will assume it is original. Since your lathe has a lead screw with 8 threads per inch it is designed for English or American (Imperial) threads with threads per inch.
If you want metric threads you have to ignore the whole table on the gearbox and find special tables for metric threads (see below). Sometimes special tables are stuck on the cover that goes over the gear train.
You should review my thread cutting program. Have you looked at that? www.HeroSteamEngine.com/RideTheGearTrain and click "Instructions and Information". This includes a video and at 9 minutes it has photos showing how the gear train is put together. My speech is probably too fast! But it is also described in text. Scroll down through the text to find the heading
"Converting Imperial lathes to cut metric threads".
and
"More about compound gears".
This includes the same photos as the video. If you go down further you will find a photo of an aluminum table of numbers. This is what you need for metric threads. The heading on the table is "N.Z. Dept. of Education Metric Conversion". which means "New Zealand Department of Education Metric Conversion".
To change your imperial lathe to metric it is best to use a special "compound gear" in the gear train. This is two gears joined together. The number of teeth on these gears can vary. The best is a 127 tooth gear connected to a 100 tooth gear. You can also use an 80 tooth gear driving a 63 tooth gear as shown in the photos. When you use these gears the lathe behaves like a metric lathe with a lead screw pitch of 2.5mm.
Even if you do not have these special compound gears it might be possible to make metric threads. It depends on what gears you have.
With the compound gears or without them, I would recommend using my program (RideTheGearTrain) to find out what gears to use. If the exact gears are not available it is often possible to use gears that give approximately the correct pitch (nearly correct). In the program you can say how much error you can accept. If you are happy with 0.5% error it will tell you what gears to use and how much error they make, up to 0.5%.
I will try to explain the copper imperial table on the gearbox anyway: The top number on the 'numeral table' (on the gearbox) shows "Threads per Inch" for cutting English or American threads. We call these "Imperial threads". You can ignore or skip the bottom number. Don't worry about it! It is not used for thread cutting.
Power feed has nothing to do with thread cutting and you can ignore it. However you may be interested in power feed. That is when the lathe automatically moves the tool for you.
(I explain the bottom number here :The bottom number on the table is for power feed in thousandths of an inch per turn of the chuck (one thousandth is 0.001 inches). The number shown on the table is for the cross slide (which goes across the lathe bed). You can also use power feed along the bed (longitudinal) and the speed is cross feed rate divided by 0.3.)
If you want to make an imperial thread with 10 threads per inch you find it in column 5 and row A so you set the gearbox levers to A 5. However you also have to look at the first column that tells you the stud gear has to have 20 teeth.
I recently added some text in the description of the You Tube Video (#2) about the knobs and levers on the Boxford lathe. This describes how to use the knobs on the front of the carriage or "apron".
@@Evan-e-cent
Dear friend, you helped me a lot.
I did not know where to look for, but with your excellent videos and your mail I can say now that I have understood largely to extent the operation of gear box
However, according to the table that is on my lathe gearbox (I attach the table to you)
If i want to make an imperial thread- as you wrote to me- with 10 threads per inch you find it in column 5 and row A so you set the gearbox levers to A but I thing is A3 according to the table on my lathe gearbox.
so the first lever (letters) On A and the second lever (numeral) in number 3.
what happens? I have mistaken? I have not understood well?
Yours sincerely
Theodoropoulos sotiris
@@sotiristheodoropoulos7750 You are CORRECT it is A3. I misread the table and got it wrong!
If you are making imperial threads you do not need the compound gears. Instead it has an 'idler wheel' that does not change the gear ratio. The idler gear usually has 80 teeth but it doesn't matter how many teeth it has. It just acts as a spacer to fill the gap between gears.
The copper table also says the STUD great should have 20 teeth.
It does not mention the last gear (on the back of the gearbox) but that has 56 teeth.
Oh, one thing I forgot to say: It is best to check the thread pitch after setting up the gear box. Get a bit of scrap bar and cut a shallow thread and measure the pitch. Do this before trying to cut a thread on any important part. This is an easy way of finding out whether you have the correct gear set-up.
Thank you, Mr Lewis
It important your proposal
If it is possible could I have your mail address?
In addition, I want the table for conversion from imperial to metric it this you have in your video.
yours sincerely
Theodoropoulos Sotiris
Athens-Greece
If you look on www.HeroSteamEngine.com/RideTheGearTrain you will find my email address near the top of every page. In the instructions at that site you will also find the aluminum metric table I described above. Just scroll through all the text until you see the aluminum.
Excellent work sir. I will send you an email maybe you can help me with my lathe. Thanks