Cutting Imperial Threads On My Metric Mini Lathe (And Metric On Imperial Lathes Too)
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- Опубліковано 17 лют 2022
- littlemachineshop.com/referen...
G'day everyone,
I have to cut some imperial threads in the near future for various projects. Seeing as these are likely one off threads, I wanted to avoid having to buy several taps that that I would probably use once or twice. My mini lathe is able to cut threads suing the leadscrew, but it is set up to cut metric threads, not imperial. In this video I will go through the various change gears used to cut imperial threads on a metric lathe.
Cutting Metric Threads On My Imperial Mini Lathe
#minilathe #lathe #machining - Наука та технологія
As an addendum which I did not get around to recoding, there are electronic leadscrew mods which will also allow for easy cutting if metric and imperial threads. It is something to consider if you use the leadscrew a lot for cutting threads. Cheers
Now I just need to know how to make metric threads with an imperial lathe cause merica(literally 6 seconds before you explained that)
Especially the one from Clough42. That is a truly neat setup.
I finished that a few months ago (Clough42 ELS). Makes my lathe a joy to use with all threads and changing feeding rate on the fly. I recommend to anyone.
Good timing... I cut my first threads today; just received the lathe last week. I was trying the "text book method", and well, I destroyed my ¼-20 threads both times on the final cut. Tomorrow, I'll leave the halfnut engaged and reverse. I'm really enjoying this hobby. I'm fortunate that I don't have to change gears for common imperial threads.
I have the opposite problem - imperial lathe and need metric threads. That little bit about "Never disengage the half-nut!" is critical. Learned that the hard way.
Actually you can. The trick is to start the lathe and engage the half-nut on your number on the thread dial. When you reach the end of the thread, disengage the half-nut and stop the lathe and allow it coast to a stop. Back out the threading tool. The clever part is to notice that your thread dial mark hasn't moved much past set mark. Reverse the spindle and when your mark comes back to the set mark and re-engage the half-nut and back up the carriage to your starting point.
Rinse and repeat.
A hand crank that fits into the spindle is a nice project and great for hand turning threads. Nice work on the conversion.
Your work is inspirational in that you aren’t aiming or expecting perfection. You just make things work and that is awesome.
Make yourself a mandrel that fits into the main shaft at the far end with a hex on it and use a ratchet spanner to turn the machine, so much easier than doing it by hand.
I regularly cut metric threads and a Myford lathe and TBH there’s no difference, just take your time.
Great video. Thanks for sharing. I am thinking of getting into the hobby. Love watching your channel you explain things really well and make it easy to understand. Thankyou
If your cutting threads by manually turning the lathe chuck i suggest making a handle to fit the back of the spindle so you can turn the spindle easier rather than turning the chuck by hand everytime. Basically a handle with an inverted collet thatll clamp inside the spindle for ease of removal. Like your videos look forward to seeing more. 👍
Awesome idea! 👍😁
I have to admit that I sometimes just remove the old/nonstandard threads and make new standard metric threads. If there's space and the material isn't hardened I have the feeling that saves me future headache. But your solution is probably more reasonable ;-)
I did that also. The post on my QTCP had a weird thread on it that didn’t match any of my dies, so I just turned it off and made a new one in M12x1.5. It is a more barbaric approach, but it works out because now I know I have that thread size in my set.
@@akaHarvesteR "Barbaric" is the word I reserve for people, who put both metric and imperial threads on one part.
@@jakubkopec9313 weeell… That’s sort of what I ended up with. The part had threads on both ends. :P
Cant wait till we move house and I actually have a garage so I can buy a lathe. Your videos have been very informative.
Never even thought about moving the chuck by hand!
Definitely helps on a small lathe
@@artisanmakes Will def do that. I do cut all the threads by band, spinning the chuck with a cutter in the tailstock...Ima chemist, I should have watched waaaay more videos 10 years ago when I bought the damn thing ^^
When I got my lathe I didnt know enough to know what I needed and I ended up with an imperial lead screw, as I am also in Australia, and refuse to use nuts and bolts measured in bananas, I also mainly use dies for thread cutting. I could be picky and say we have only been using the metric system for 50 odd years now, why would a new lathe sold here even have an imperial lead screw... but it is what it is. Wont get caught again next time though!
That's H&F for you.
There are still a few banana eaters still out there in the wild.
Nothing wrong with bananas, It's more natural to count by 0.001" than it is to count in 0.02mm increments
Excellent
Thanks for that, I didnt know you could even do that.
And less than 1 thou error over 1 inch of thread is well within usable thread tolerance. 👍
Well done …… precision home made tools making more tools 👍👍😎👍👍
If you _really_ want to get closer, the integer ratio between 16 TPI and 1.5mm/rev is very close to 189:200. It means making some big gears, but you can get to just about perfect for a lot of thread pitches from both systems.
Didn't know about that gear ratio, but that would never fit on my mini lathe :)
@@artisanmakes A mod 0.5 200 tooth gear would be 101mm diameter, which is conceivable. The idea is still simmering but the numbers look pretty solid.
if one has room for 189 teeth one could use a 127 tooth gear somewhere in a chain (there will need to be additional gears involved) and get an exact ratio. That is the standard method for lathes that have enough room as 1 inch = 25.4mm exactly (127 is half of 254 and as 127 is prime there is nothing smaller that will give an exact ratio)
@@jaytalbot1146 The 127:125 ratio is true but you'd need to work out the numbers for that approach and I haven't.
Try to add a gear with 63 teeth. 54 and 42 are further helpful, then perhaps 57 for some 19-related TPIs. That way you could significantly reduce the error of approximation, still being able to fit the gears into mini lathe's quasi-banjo 😉
By the way, I've just replaced the bolt and nut holding the banjo to the bed with a washer-head screw with head ground flat (and two nuts locking it to banjo and bed) to allow fitting 114 teeth gears instead of 80s for fine 0,046 mm auto feed. They're arriving tomorrow, then I need to slightly cut out the back of the cover and I'll see how it works 🤔
If pitch of the lead screw is metric you can make metric threads. If pitch is imperial, you can make imperial threads.
Most cheap import lathes that can make metric and imperial threads have a small pitch error. So their lead screw isn't exactly metric or imperial.
To get an exact conversion, the lathe must have a 127 tooth gear. 127 is a prime number. 127*2=254, which is the conversion between metric and imperial measurements.
The leadscrew on this one is 1.5mm pitch, so it can do metric without error. its true that there is a small amount of error on making imperial, usually less than 0.1% error if you go by the Little machine shop chart. Why we dont use 127 tooth gears on these smaller lathe in because you could not physically fit a 127 tooth gear on the banjo. The largest I was able to fit was 100, and that was not easy
That is a nice video thanks ! Maybe a stepper motor on the leadscrew could be an easy alternative instead of making new gears every time.
5:48 That final thread looked really loose in the chuck, so no wonder there was so much runout.
Since you are leaving the half nut engaged, and turning the lathe over by hand, you really should be checking the thread throughout the process, and also you need to take MUCH shallower cuts towards the end.
it was something to consider, but seeing how it was so close to the run out I get with the commercial arbor I stuck with the one I made. Cheers
Thanks, what cutter and tool holder are you using?
Hey mate, what steel did you use to make that from?
This is a time where having your cross slide on and set to 29.5 degrees would be beneficial for proper thread cutting. Fantastic video as usual!
That's really not necessary with indexable threading inserts. The thread cutting shown here is perfectly "proper" !
Oh really? My bad I thought it was always still good practice for better surface finish and lowering cutting loads even with indexable tooling. Good to know!
@@MidEngineering it really depends on the rigidity of the lathe as to how well they handle cutting threads straight in, you can half the pressure on the tool/ lathe by spinning the compound to 29.5 degrees
@@markshort9098 For any given depth of cut, the amount of metal being removed & therefore, the load on the tool/lathe (using indexable threading inserts), is the same whether you feed straight in or at an angle. The 29.5deg. approach is only really needed when using a simple vee tool with a top rake angle ground on one side.
@@MidEngineering it doesn't matter what the tool is made of, inserts don't magically require less cutting pressure.. with a straight in cut the tool has material engagement on both sides of the cutter for the depth of cut and when feed in on an angle it's cutting full engagement on one side and depth of engagement of that pass on the other side which is clearly less tool engagement so less pressure, add to that the chip coming off a straight in feed has more of a v shape to it which creates more pressure again because it has to deform the chip a lot more to get it flow.. if you have a really ridge machine then the extra cutting pressure isn't a problem but for a toy lathe or really big threads it does make a difference.. the more cutter engaged in the work the higher the pressure, this ain't brain surgery
Cut in reverse with cutter upside down.
Hard steel will require carbide insert cutter. Regular die won't cut.
It looked like you were turning the chuck by hand some of the time but at other times it looked like you were running the motor in short pulses. Thinking that an interesting mod would be a momentary push button that bypasses the normal on button.
Very unlikely - it was almost certainly all done by hand.
I'm the same as you. It's much quicker to use dies so I don't bother with screw cutting unless I need high accuracy or a non standard thread.
Also I have a mini lathe and that banjo is the biggest POS known to man. 🤣
You should add chamfers at both ends of the thread, before you start cutting the thread. Good job by the way.
Certainly something I overlooked. Cheers
how slow is your rpm now with ac motor
Your drill chuck arbor should have an unthreaded section to accurately locate the chuck. Threads aren't an accurate method of locating a feature.
Don't forget to get 55* inserts and pitch gauges for BSP threads.
Although a quick search shows that commercial arbors lack a locating shoulder, so I suppose the chuck doesn't have one either.
@@jonathan1427 threads are sometimes used as precise locating features, as in threaded lathe spindle noses. I have seen some 1/2-20 drill chuck arbors that have a locating boss
@@MF175mp Can you give an example of a lathe spindle nose that doesn't have a shoulder behind the thread which does the actual concentric locating?
The amount of play inherent in a thread for it to not bind is more than a locating fit tolerance allows.
@@jonathan1427 maybe it's more of a thing on wood lathes. But I found another example, my cnc lathe's rotating cylinder is held in place behind the spindle by 2 subsequent thread fits only and it needs to run true. Runs within 0,01mm (half thou) currently
@@MF175mp Interesting! Yes, for wood lathes I imagine the accuracy is sufficient. On your CNC lathe is that the collet closer/drawbar cylinder? Would parts be made defectively if it were out of alignment, or does it just need to be close-enough for balance? I was under the impression that there was a certain amount of 'float' between moving parts to allow misalignment with the spindle axis.
you modified the dividing head to make gears to cut threads to make a tool holder for the chuck so you can use it for next projects.
So you made a part to make a part to make a part to make parts.
Doing mods the extra long way round. :)
I was under the impression, unlike metric threads imperial ones require different cutters for pitches and thread type but maybe its not that important. I too have a metric lathe and would really like to be able to do some imperial threads, like the one on the front of a Dremel, I'll see what that calc is like thanks
If you are doing whitworth threads then you’ll need a 55 degree cutter. But unc threads use the same 60 degree cutters
@@artisanmakes OK but why do they have different inserts then like 16ER11.5NPT CP500 External Threading Insert? maybe its not the tooth angle but the overall profile?
You can get specific ones for specific thread profiles yes. From memory those are called full profile threading inserts and they are good for one thread pitch. Most general threading inserts are partial profiles and are good for multiple pitches
@@artisanmakes That explains it thank you
Isn't a 3/8-24 fairly standard to get a die in? I use that thread all the time, and I find taps and dies in that thread size and pitch all the time at garage sales and just all over the place. And they were very easy to order online, is it very uncommon where you are?
Not as common, you can buy them but I didn't feel it necessary to buy a $15 die that i'd probably only use once.
@@artisanmakes I was weighing that against spending the time to make a gear that (am I correct in saying this) you would also only use once (probably) to thread 3/8-24?
But I suppose at least you could get it done right away or in a couple days.
Maybe I'm biased, at my previous job, I messed with 3/8-24 every day.
@@dzarren Thankfully these gears are going to be used to cut other imperial threads. A 3/4 16TPI for a lathe chuck, 1/4 BSP for some pipe connections and a few other odds and ends that I need done.
@@artisanmakes - Crazy problem. Most people have the complete opposite. I am clearing out my dad's engineering tools and there is boxes and boxes of "imperial" taps and dies, all different sizes and types in BSW, BSF, UNC, UNF, BA, BSP, NPT, etc, etc, etc.
Old non-metric taps and dies are literally dime-a-dozen... do you realise that you don't need to buy them brand new?
@@johncoops6897 you can if you want, im sure its cheaper. But I simply don't have the time to go chasing used taps and dies.
have you ever considers cutting a third with a mill Threading Toll on you lathe See Stefan channel called Mill trading on a engine lath it will set you free.
damn, cutting treads on a lathe without nuts is a mofo to do. But yous doing it by hand cranking.
First one 😍
Nobody cares. Shameful that you embarrass yourself in public like that.
🏆🍾💰👏👏👏
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