Thread Cutting, Lathes and stuff

[funkychicken]

I've narrowed my lathe selection down to two Hafco lathes. The AL-50GB and the AL-54B.

The first is the right size for what I'm making, so it's the obvious choice but the latter can cut threads to 0.1mm and so it's looking rather attractive. But are threads that small practical? What I'll be making won't really require finer threads than normal fine metric threads so should I just save my dosh and get the AL-50GB.

What's cutting threads on the lathe got over using a die?

[joe greiner]

What's cutting threads on the lathe got over using a die?

Variable diameter, for one. Ancient, and possibly still current, photographic lenses often had/have threads of 32 per inch (approx. 0.8mm pitch), in at least two different diameters. Might be difficult to hold such a die square to the axis, if dies that size are made at all.

As robots and CNC advance into production, someone must teach the robots. Eventually, I suppose old robots can teach the new ones; but for now some prototype construction is advisable, with human contribution, to illuminate production difficulties.

Joe (old robot)

[echnidna]

Every tool/machine you ever buy won't be able to do something you'd like to do one day so then you have to work out alternative methods.

If it was me I'd go for the AL-50GB and worry about superfine threads when you need them.

The money you save might buy another totally different yet more practical tool

[Kody]

Hi Funky
Read all my posts about screwcutting for some excellent info on producing threads on the lathe. A thread that is cut (it's called screwcutting) with a lathe is far superior to a die cut thread because of its accuracy of form and depth. You can cut the internal thread with a tap (if you can find one) or even screwcut it and then make the external thread to fit. With some practice, it's not hard to do.
If the lathe you buy has an Imperial Leadscrew of 8 TPI then I suggest that the smallest thread to screwcut would be 48 tpi. In my opinion, the best lathe has an Imperial Leadscrew as this is so much easier to use compared to a metric machine.
A thread of 0.1mm pitch is extremely impractical. The smallest thread you would be likely to use would be 0.3 mm pitch but more realistically, it would be 0.4 or 0.5mm pitch. Are you going to make wooden pens?. I recomend using brass to cut the threads on if a metal is required for the pens. Fine threads reproduce very nicely in brass. You can also use machining grade aluminium but brass is better.
It's a real pain to cut metric threads with an Imperial lathe so I would stick to the Imperial thread system for selecting threads to use. It's just as big a pain (or worse) to cut metric threads with a metric lathe as the lathe needs a brake to stop. It also needs to be able to run in reverse. None of this is easily mastered by a beginner and without the ability to reverse, it's nearly impossible to do. Do read all my posts on screwcutting for more info.

Kody

[joe greiner]

Apples and oranges. Both lathes supposedly have "full set of change gears for metric and Imperial."

Get more complete specifications, and compare/contrast other features, e.g. dimensions.

Cheers,
Joe

[bollie7]

If you can afford it, spend the money and buy the bigger machine. Not for the screwcutting but for the size. You won't regret it. Otherwise a little bit later you will be thinking that you need a bigger machine and it will cost you more then.

I'd like to be able to afford something like this.
https://www.machineryhouse.com.au/Pr...tockCode=L254D

or this
https://www.machineryhouse.com.au/Pr...tockCode=L632D

regards
bollie7

[franco]

Kody,

You said:
"It's just as big a pain (or worse) to cut metric threads with a metric lathe as the lathe needs a brake to stop. It also needs to be able to run in reverse"

Did you mean "It's just as big a pain (or worse) to cut imperial threads with a metric lathe as the lathe needs a brake to stop. It also needs to be able to run in reverse"? If this is the case, I agree, though the brake is not always needed . It is a time saver and handy when threading to a shoulder though.

When cutting metric threads on the metric lathes I have used, the procedure is exactly the same as when cutting imperial threads on a lathe with an imperial leadscrew, except that the thread dial usually has more than one gear to engage the leadsrew. Each gear covers a range of metric thread pitches - one gear does not cover the lot as it does with an imperial leadscrew cutting imperial threads.

Regards,

Frank

[blackfrancis]

Hi FC

Here's some thoughts.

In my opinion, for you, a metric machine may be better. The imperial system is becoming more and more obsolete as time goes by. If you have the machine for 20 years you may find imperial a real pain. I note the machines you are interested in come with thread chaser dials. On a metric machine you don't have to reverse the lathe to cut a metric thread. The small complication they do have, over an imperial machine, is that you have multiple gears (worm wheels) for the thread chaser which need to be changed for different pitches. Personally I have never found this to be much of a problem. Anyway, as Kody rightly says, the imperial system is definitely better from the point of view of screw cutting.

A screw cut thread will have accurate pitch and it will run true. One cut with a die will have neither.

The AL-50GB is very similar to the lathe Big Shed recommended to you earlier. But the one Big Shed recommended has a tailstock that doesn't need a spanner to move and is available with electronic speed control. Perhaps worth some more consideration. This lathe looks like it doesn't really have a screw-cutting gearbox. The cut back gear box on it may be useful for adjusting feeds but Iooks like you will have to manually change gears to go from screwcutting to auto feed. I'm just guessing from the pictures, but worth checking out if you're going to purchace.

The other lathe appears to have a better gearbox, but perhaps not a great one either. For both lathes, it is worth checking out whether they have suitable gear boxs for their leadscrews. The gearbox for a metric lathe is different to one for an imperial lathe and it's not so uncommon for metric lathes to be sold with imperial gear boxes. With the AL-50GB you can put your hand under the gearbox and find a long cluster of gears. If this cluster is attached directly to the leadscrew it is an imperial box, if it's attached directly to the shaft where the change gear is fixed it's a metric box.

Having said all this you are probably geeting great bang for your buck with these machines. You can't expect to have everything for this type of money.

Good luck
Steve

[Big Shed]

Hi FC

The AL-50GB is very similar to the lathe Big Shed recommended to you earlier. But the one Big Shed recommended has a tailstock that doesn't need a spanner to move and is available with electronic speed control. Perhaps worth some more consideration. This lathe looks like it doesn't really have a screw-cutting gearbox. The cut back gear box on it may be useful for adjusting feeds but Iooks like you will have to manually change gears to go from screwcutting to auto feed. I'm just guessing from the pictures, but worth checking out if you're going to purchace.

The other lathe appears to have a better gearbox, but perhaps not a great one either. For both lathes, it is worth checking out whether they have suitable gear boxs for their leadscrews. The gearbox for a metric lathe is different to one for an imperial lathe and it's not so uncommon for metric lathes to be sold with imperial gear boxes. With the AL-50GB you can put your hand under the gearbox and find a long cluster of gears. If this cluster is attached directly to the leadscrew it is an imperial box, if it's attached directly to the shaft where the change gear is fixed it's a metric box.

Having said all this you are probably geeting great bang for your buck with these machines. You can't expect to have everything for this type of money.

Good luck
Steve

Steve, far be it from me to try and push people towards the lathe I chose, however when I did my original research I found that most that bought one of these 9x20 lathes modified it.
Of the top 5 modifications that people made to the lathe, number 1 was a 4 bolt compound mount. In the top 5 was a camlock tailstock and electronic variable speed. So when I found a 9x20 that already had these 2 my mind was made up very quickly.

The camlock tailstock works like a charm and the EVS is a godsend. You can just dial in the best speed for the cut your doing, no messing around with belts. The other BIG advantage of the EVS is that it acts like an electronic brake. I was recently cutting 1"x8tpi external thread up to a shoulder, so you have to stop the lathe very quickly, which at 110RPM can be tricky. However with the EVS you just hit the stop button and it stops on the spot. In fact I am in the process of making a stopswitch that can be mounted on the lathe bed that will make this automatic.

When cutting imperial threads on this machine, you keep the half nuts engaged all the time (left hand lever on the front), and just reverse back (using the lathe reverse feature). For metric threads you use the thread dial.

The right hand lever on the front is for the autofeed, the speed of which can be altered by changing gears on the side and selecting the appropriate position on the quick change gearbox on the front.

The other mod I have made to my lathe is getting a Quick Change Tool Post for it, worth its' weight in gold

[Kody]

Franco
Cutting Imperial threads with a metric lathe is bad news and cutting Metric threads with an Imperial lathe is also a pain. I have used both types of lathes and unless the lathe has the full compliment of gears and accessories, screwcutting can be a pain. I concider having a brake to stop the spindle is an absolute neccessity when cutting metric threads with an imperial lathe for beginners in lathework. When buying a lathe, you certainly get what you pay for, but keep in mind that many posts in this forum are questions from beginners who are searching for knowledge about machining and that they use small lathes described as "hobby lathes".
Some threads in the metric system are hopeless and a few in the Imperial system are the same. Of the two systems used for fasteners (nuts and bolts) I think the imperial system is far better. A good example is M6-1. IMO, a far better size is UNC1/4-20 but this pitch is a little too coarse for many applications where more core strength is required. Using UNF1/4-32 has a tendency to strip the threads with constant wear and tear but a BSF 1/4 - 26 is perfect. M10-1.5 replaces 3/8-16 but the OD is much bigger and often can't fit the parts if trying to swap over. The equivalent to M8 is 5/16th but there is no equivalent to 3/8's in metric. It's the same for a 1/2 inch thread. M12 is smaller and the next metric size is M14, no good when 1/2" is needed. What I am saying with all this waffling on, is that metric fasteners will never fully replace imperial fasteners. We will always have the two systems of threads to use here in Aust. The absurdity of metric threads becomes clearer when you want to use an "in-between" size. The metric system lists as a standard thread, M15-1, M17-1 and M18-1.5. While you concider those "standard" sizes, check out M18, M25 and M27. Try buying just one of these bolts or nuts, and there's even more "wierd" sizes listed. Oh well, waffle-waffle-waffle. I still prefer the imperial system of threads, esp the Unified National threads.

Kody

[echnidna]

so ya gettin confused yet FC?b

[Big Shed]

If you haven't already done so, check out Steve Bedairs' site, lots of good info and lots of links to other 9x20 sites.

This whole metal lathe thing can indeed be very confusing for the uninitiated, it certainly was (is?) for me.

[blackfrancis]

Hi Kody

I don't find myself disagreeing with your sentiments about imperial vs metric threads. But my point is simple. FC is 15 years old and like it or not, metric threads are slowly replacing imperial ones in this country. I tried to buy some BSF or UNF taps (wasn't fussy) at a tool merchant a few weeks back and the guy laughed like I'd just walked in out of the 1960's. For an older person, continuing to use imperial threading gear is no problem. For a young person, who is starting out, an imperial lathe will result in gradually acquiring a range of imperial taps. From a long time perspective I think metric is the way to go for such a person. It's no use having imperial gear when nobody's using it anymore. Like it or not, despite the pros and cons, people who design stuff for a living in this country don't draw imperial threads anymore. If you do a course in design in this country you are taught to use metric threads, not imperial. Imperial threads are slowly dying off. In europe they don't use them at all, and in the long run we won't either.

my 2c
Steve

[Woodlee]

I agree with what Kody says ,we will be using both systems for along time to come .
Even in Europe where the Metric system has been in use for a very long time ,they still use imperial threads and fasteners where a metric thread is not suitable or is non existent.

They well may be designing stuff with only metric threads ,but there is a lot of machinery around that have imperial threads ,when I worked in the mining industry , we had American threads on all the mining equipment and British threads on all the pumps and process equipment manufactured in Australia.I'm not talking last century here just a few years ago.This machinery will be around for along time .
I doubt Caterpillar will change to metric .

They are still manufacturing some metal stock in imperial sizes ,I've been trying to source some 12mm stainless steel round stock ,so far all I can get is 1/2" (12.7mm)

Kev.

[.RC.]

I doubt Caterpillar will change to metric .
.

They have been using metric fasteners in all their machines for a few years now. All US car makers use metric fasteners as well


I am not impressed with metric threads and bolts... We are supposed ot have been metricated since 1965 or so (long time before i was born anyway)..I went into Bolt and Steel a couple of years back looking for a 9mm metric bolt to replace a broken head bolt out of a Kubota engine...They said they cannot get bolts in 9mm size, even though it was a standard metric size.. I was in there again earlier this week and they gave me a catalogue of all the bolt sizes they stock..Quite amusing to see so many sizes stocked in Whitworth and Unified...In fact they probably outnumber the metric..

Me I prefer imperial bolts, at least they have standardised bolt head sizes for a given diameter bolt unlike the metric DIN compared to JIS..