Threading for beginners

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Finally gathered up all the basic stuff to start threading, I think... Threading wires, micrometer, thread pitch gauge (U.S) , fish tail gauge, and some tap and dies.

I have watched a lot of videos and read a lot of stuff but this is still a bit intimidating. Equations to figure out size and charts with all kinds of numbers for outer and inner diameters, tool angles...etc

Not sure I understand what the charts on my lathe are telling me exactly as to speed of lathe and gear selection, etc..
Or what kind of threads will it cut as is no change gear..lol
What tool in the arsenal should I choose?

I need some practice and understanding of how to make a matching set of threads, i.e. internal and external fitting threads for a tool height check tool.

Will post progress pics along the way to hopefully help others new to threading.



I have never been able to decipher those charts on the import mills either!

Don’t overthink the treading too much, when you first start you will make mistakes! Get some stock and do lots of practice cuts, get familiar with how your machine acts and keep at it for awhile before you actually cut threads on a part you spent hours machining and ruin it!

I’ve been cutting threads for several years and I still screw it up sometimes! I finally bought a set of thread wires recently, but still haven’t used them.

When practicing just try to get the threads to fit in a nut without too much slop at first also remember to take small depth cuts with each pass.

Perfection comes with experience!

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I think I have the same brand thread wires.

The paper that comes with them has a typo on it (unless they have changed it but that seems unlikely)

I did copy one from another brand.



The photos of the lathe showing the charts on it appear to only show feed per revolution in both imperial and metric. There should be additional charts that show threading combinations. The layout of the gear train appears to show that the lathe is capable of changing gears to achieve different rates of advance of the lead screw per revolution. What make and model lathe is it? Did you get the lathe new? Did it come with any additional change gears? Do you have a manual for use of the lathe?
All the information you need to change thread pitch is in those charts.

In image # 4197 the lower part of the chart (white) is for threads per inch.
The upper part of the chart (blue) shows the gears and locations for them to produce the pitches listed below .

Image #4193 shows a simplified map of your lathe's gear train. Your lathe will also have a means of adjusting the gear train to accommodate different diameters of gears.

It's a dirty job, bring an nice rag out.
In school machine shop, the teacher showed us how to grind a tool to fit the fishtail gage, how to set it up in the lathe, using the fishtail gage and how to set the tool on center using the point of the tailstock center; we learned how to set up the QC for the thread we wanted to cut, and just went at it, using only a appropriate nut to gage the fit. I hardly ever use thread wires, they are a pain in the butt! If a thread is fussy for fit, I use a thread micrometer, they are much easier to use than wires, and can be bought used for not a terrible amount of money. Do not waste your cash on insert threading tools, they break way too easily, I use HSS tools made by Aloris, they are sharpened only on top and last a very long time.
Weiss WBL250f Lathe , Picked it up new from Dro Pro's has all the change gears and manuals. Just not real clear after reading 5 times on the threading section.

Thought some of you could help me out step by step tutorial on threading.
I have plenty of 1/2" to 1/4" steel and some 1/4" aluminum up to 3/8" aluminum stock.

Let me know an easy size to practice , I will get the gears changed till I get it..lol
Starting with aluminum seems best so let me know a set of size dimensions and I will start setting up...

Many thanks, my intent is to do a picture step by step thread so others can follow later how to start threading.. Tools, angles, formulas..etc
Weiss WBL250f Lathe , Picked it up new from Dro Pro's has all the change gears and manuals. Just not real clear after reading 5 times on the threading section.

Thought some of you could help me out step by step tutorial on threading.
I have plenty of 1/2" to 1/4" steel and some 1/4" aluminum up to 3/8" aluminum stock.

Let me know an easy size to practice , I will get the gears changed till I get it..lol
Starting with aluminum seems best so let me know a set of size dimensions and I will start setting up...

Many thanks, my intent is to do a picture step by step thread so others can follow later how to start threading.. Tools, angles, formulas..etc

In the left chart above, the diagram of the gears at the top right shows the nomenclature for the gear train. To the left of it, at the top box in blue, on the left, the number pattern corresponds with the the numbers in the boxes to the right. The numbers below show the feed rate in decimal inch per revolution of the spindle for achieving various cutting rates while turning stock, fine and coarse. You place the gears with the correct numbers of teeth in the positions indicated, and with the lathe lever moved to the correct A, B, or C cutting position.

In the right chart above, the patterns in the blue boxes at the top correspond to the same gearing setup as in the left chart top left. The setup is done the same as for threading in the left chart, but gives you the number of threads per inch choices shown below. There should be a lever on the lathe marked A, B, and C. It is moved to the position required to achieve the feed or threads per inch you desire.

When threading, make a very light scratch pass for the first traverse across the work. Then check to see if the thread is correct before proceeding.
I would start practicing on aluminum with a common thread type. Say, 1/4-20. It's all over the place, easy to locally get some nuts to use for test fitting, etc.. Look up the OD, turn down to that, then swap to the threading tool and set your gears up. Take a scratch pass and use a thread gauge to make sure you got the gears right. If you're satisfied, do your cuts till you can fit the nut on.

Try with the compound at 29.5, and at zero just feeding in the crossfeed.

You can calculate the depth of cut, but really, just get close and take light passes till it fits. If you need to have a "class" fit, use a thread mic or wires.

For the gears, your chart looks like mine. Find 20, it's under the "A" row. Look up and that's the gear train you need. "H" indicates a spacer. The bottom one "L" is the leadscrew input. The top is the spindle. So, you need this from the top..

A spacer and a 70T. 70T at the bottom of the stack.
A 30T and 50T. 50T at the bottom mating with the 70T.
A 60T and a spacer, 60T mating with the 30T.

On my lathe, they are all on a single rail that pivots. It's easier to start from the leadscrew side for me, so put that one on. Then put the 30/50 stack on, mating up the gears and leaving a little space. The documentation with my lathe recommends a piece of paper meshed into the gears to set the spacing. Snug that up then install the top spacer/70 meshing the same way. The 70 mates to the spindle.

A/B/C is a gearbox lever. Set it to "A", rotating the spindle as you go and you will feel it drop in. Same with direction and feed/thread if your lathe has those.

Now with the lathe on, you should be able to engage the half-nut lever and see the carriage move. You're ready for the scratch pass.

Also check out Joe Pieczynski on youtube. https://www.youtube.com/channel/UCpp6lgdc_XO_FZYJppaFa5w/videos He has some threading videos that work well for me. I really like the reverse rotation away from the spindle method.
All right looks like some great much needed info here!!

I think this will get me going, I can start the gearing swap and look up the diameters.

I will then need to start the tool set up, what tool in my arsenal and the angle of attack.

The gear's mesh should not fit tightly together and also should not fit too loosely. I stick a piece of an ordinary sheet of paper between the gears, push them together tightly, tighten down the gear positioning bolt or nut, and then turn the gears to run the paper out. That makes it easy, quick, and repeatable. Clean the gears and put some grease or oil on them before proceeding with the threading.
Started changing the gears and got everything apart and 2/3rds back together. Now the top gear and axle wont cinch down without the gear freezing=too tight wont turn, or the nut turns with the gear.
I have swapped axles with middle set and no change there, flipped the gear over, etc

Thinking the new arrangement for the top is some how a different thickness now.
Any ideas?
It might be. Do your gear bolts have a castelated nut on the end? I had to loosen a set screw on the side of that and turn the nut about 1/2 turn to get it to sit properly when using a spacer.

The stack of washers, gears and spacers has to sit evenly as well. Mine can get slightly off causing a similar issue.

The first few times you change the gear set, it's tedious. You get used to it though. I try to save all my threading for the end, so I'm not constantly swapping them around.
PVC..will see if I have any..lol I have a bit of aluminum rod to practice with but I will check and see.

Yes , I think the nuts have a set screw in the end. I was wondering if it was adjustable for this issue, will try again tonight.

Thanks for all the tips and tricks!!
You can get PVC and ABS pipe fittings for pretty cheap at the big box home stores. Play with some of that stuff, and then aluminum, before playing with steel or expensive metals.
A stick of 1/2" PVC is crazy cheap and works great. And you have 8ft of it. It's great for testing gear settings etc.. The down side is you can't use an off the shelf nut to test fits. But it's a great way to practice the basics, engaging the half-nuts on time etc.. If you time it wrong, you can get some really bizarre results. :)
Have you tried adjusting the axle spacing on the middle gear sets as described on page 21 of the owners manual? Page 22 also mentions adjusting the "quadrant angle" to adjust the gear meshing width.

When my gears were new I found some of the gears were very tight on the axle and if they are not seated all the way then the meshing gears didn't line up.

When you loosen the nut on the axle swing arm (not sure what it's really called), behind the bottom gear make sure the swing arm hasn't moved in or out, on it's axle, when you tighten it.
Gear mesh was good, just the top gear when spun manually would also spin the axle and attaching nut would spin loose.

In the future I will remember to where some gloves as its a messy job, have grease under all my nails..lol

Loosening the swing arm with the gears all the way, removing the bolt and spacer allows the swing to rotate all the way down, making it easier to reattach the gears.

I snapped some pictures of the change gear operation, way more than I expected, had to file a couple pcs to get better fit. But overall a simple thing to do.
I see now why some people will not buy a lathe with change gears. So much more simple to shift the gears with a handle vs manually pulling them.
I guess with myself having more time than dime it will work great!!


Remember that after doing your threading, return the gears to the original setup for setting feeds. Otherwise, you will get some feeds that you were not expecting...
So save the gears out that I just took off? Really..lol
I was wondering about this today.
I was leaning towards leaving it, unless it feeds odd.
Does it state somewhere what the stock configuration is and what it would thread or how fast the rate of feed is?
The chart at the top left has the feed gearing. On mine, the one on the left was the default. The number in the columns is the feed rate.
Ok , thats what I thought, just didnt make sense to me why two different sets listed. also the two pictures in that chart, whats the difference and use of this? Pic 4193


The gears all went back on and adjusted out great with the lil set screw on the nut!! BIg help!!
4193 shows the feed rates for the carriage and the cross feed. The top set is the carriage. That's what those icons are trying to show you, but like all icons they don't mean much until you know what they are!

Glad that helped, it took me some goofing around with things before I got that set screw figured out, might as well save someone else the hassle.
I am often puzzled by the problems that people have with threading on a lathe, it is not that difficult.
The radial position of the spindle and the axial position of the tool must remain coupled, on a manual lathe this is achieved by way of the lead screw geared to the spindle.

If you are unsure of your gear choice on a lathe small enough to rotate the spindle by hand place a dial indicator on the bed and engage the 1/2 nuts and rotate the spindle 1 revolution , this will be the thread lead. If say a 20 TPI thread the indicator will move 1/20" per revolution of the spindle. One TPI lead off is easily seen this way.
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