Good advices for a newbie (threading tools lathe)

[rendoman]

Hi!
I'm a newbie of this forum
Some weeks ago i fixed my old lathe, changed bearings, restored a shaft for automatic, and buyed some gears for threading. Hardware store in Italy are similar to chinese store, same poor quality and common tools for Diyers sold at higher prices, the bigger is the shop the lower is the quality. Industrial suppliers have very good brands and tools, but they don't sell at single people, and if they sell the price is high as hell. At this time i have troubles finding used good tools. Surfing on internet i found on aliexpress some chinese indexable tool with insert, ( 40\50 $ one tool + 10 insert ) but i don't know if they are good or not.

I see in this forum some really interesting post of very skilled people, i'd like to ask some advice or tips and tricks for create internal (and maybe external) threading tools for lathe. I'm not too skilled in grinding tools, i'd like to create something sharps for threading aluminum and steel ( not inox ).

I post some photos of my little box with tools, i got lathe, cst milling machine, tube and plate bender , electric saw slow blade (sorry i don't know the eng name, in italian is "troncatrice a disco lento" with steel blade with short theets). transformer ac old welder and oxy-acetylene torch ( 40-500 lt/h and cutting torch )

Thanks in advance for an answer

Ps: my next project is to make a pair of aluminum horn similar tothe last photo, but bigger (130mm - 5" dia), i need threading the horn and the flange attached to driver.

Saluti
Stefano

[Ed ke6bnl]

I am not real machinist but bought my DRO through aliexpress and a nicely made threading tool with insert for the price of an insert. good service and good products. I will be doing more business with them

[C-Bag]

Hi Stefano, and welcome.

I'm new to threading on the lathe too, but there is a lot of folks on here like Paul and Marv who can help.

Just to be clear, the units in picture #5 are audio tweeter horns or wave guides, correct? And you are wanting to make larger versions of these? Are the drivers you are wanting to thread into the horns threaded?

I personally learn a new process best when I have a project, just like yours. I would think your first step would be if you have threads on the driver to use a thread gauge to determine the thread pitch. Then check your lathe gears to see if you have the correct gears to make that pitch. There are lots of great videos on YouTube on threading. Sorry if you already know all of this.

[rendoman]

Hi! thanks for advices!

The units in 5th picture are tractrix profile horn on an ex apt150 eminence driver. I didn't like the sound of the original constant directivity horn in my small room (5 x 5m) i tried different kind of profiles and wave guides on drivers 1" and 2", after my tests i found the tractrix profile maybe the best sounding at all for focus and detail (and for my taste).
I tried exponential, conical, multicell, iwata profile and some Others, i still prefer tractrix conical and iwata not bad! In my opinion the best things to do is choose the right frequency range in which the driver gives the best, than project the horn smaller possible.

I posted a couple of fresh photos of drivers, they have plane surface with 4 m6, i want to make a flange threaded and a bigger version of the 5th pic tractrix threaded too. I used this driver with different attachments for many years, although Rcf rate this drivers from 1K to 20khz i'm sure that using them in this range is a suicide they start good at least up to 1,6khz (2khz is better) and end at 12khz. Using them before and after this range in my opinion is forcing. In Pa speaker with 2 or maybe 3 way with a woofer really extended that's the only choice.
I don't know your ideas about spaker with fullrange or multiway system, i can summarize my experience and my taste in few points:

- high sensivity full range (single cone or whizzer, i want to try lowther alnico on my system) for voices and range from 100 up to 10k
- great improvement using subwoofers down to 250hz
- good setup with tweeter just for some more air

In my system maybe i don't need the 4th way, i got the range from 150hz to 15khz covered with the big horns up to 110db/w/m, but i love to see this massive aluminum horns and i want to make some test

Your right, I think i have to setup a good steps program, the project is a bit complicated and i have no possibility to fail

Are you enthusiast of hi end audio?

ps: sorry, my english is bad as hell

[C-Bag]

Your English is a million times better than my non existent Italian

In my youth I dabbled in hi end audio, but we are talking in the 70's. At that time there was what I think of as 2 schools of thought, hi efficiency JBL/Klipsh 2way horns with like around 75w RMS x2 amp. The camp I was in was the lo efficiency 2 way ESS Heil transformer line cabinet bi amp Dynaco 120 for teeters and Dynaco 400 for lows. I still own a set of EES's with Hafler pre and 220 amp. It cured me of the search. The Heils go from 1k to 22k.

As an acoustic musician, it sounds the most like what those instruments sound like live to me. I don't have the large line transmission cabs, but if I could have any cab for lows to match with the Heils it would be the old Dynaco A-50 cabs. With a big amp like the 400 running it with a good electronic crossover they would go down to 20hz. We did it with a frequency generator. Sadly you don't see those around much, and the design was a tuned baffle design that I've not found any plans for or I'd try and replicate them. They we much smaller and musical than a line cab IMHO. By the totally impressive picture of your stereo (wow!) I would say you and I are also in different camps as I shy away from directional horn setups. I'm more into what we used to call the "bathtub of sound".

I'm a mandolin player and mostly play Bluegrass, Irish fiddle tunes and some folk. So those genres and gypsy jazz is what I mostly listen to. I play in a couple of bands and when I think about it I was exposed to live sound PA's before I started to play an instrument. So dealing with PA is a whole other world. And most of the equipment is in the high efficiency camp. I use a set of gen 1 Mackie SRM450's(made in Italy!). I like the sound, they are a little heavy, but they just keep going. I toy with the idea of trying to build a set of PA cabs using the spare set of EES drivers I have.....but I'm lazy, and the Mackies are still going strong.

[PJs]

Welcome Stefano! Ambitious project but your system Rocks at least visually, just can't hear it from here!

As for threading on the lathe, I am a novice but done some. I found with aluminum I prefer high speed steel tools and grind my own. If you have a fish tail they are easy to grind. The profiles are easily found on the net, basically 60º with no top relief and around a 7º side clearance angle. The key is to know what the root radius is and grind it appropriate for the thread you are cutting. For internal threading you can search the net to find various profiles depending on your project and depth (length) you need to cut based on square tooling stock. You can also make one from round bar and use round tool stock with a flat ground on one side, drilling a tight clearance hole for the stock and then use a set screw to hold it in place in the round bar.

I tried exponential, conical, multicell, iwata profile and some Others, i still prefer tractrix conical and iwata not bad! In my opinion the best things to do is choose the right frequency range in which the driver gives the best, than project the horn smaller possible.

Very impressive on cutting the various profiles or did you just try them for your space? I would think that any time you add a horn, especially of the magnitude you are talking that it will be much more directional than the flat face style. Love to see where you take this based on your other horns!

C-Bag, you continually amaze me on the breadth of you knowledge. Aaaahhhh! ESS Heil AMT1, Sansui 1000, Nakamichi PA 7...Oh My, Yes! Still have my Sony PSX 7 with a Stanton 681EEE. Still love tubes for quality and richness. One day a set of MacIntosh's and modern Retro Heils to replace my Marantz and Monitor Audio set...(bucket list and lottery win)!

[C-Bag]

I'm glad you joined the party PJs and was helpful to Stefano. My ramble into my lo budget ancient hi fi days didn't do much to help his quest for audio nirvana

With your truly impressive background PJs do you think it's even necessary to have the guide thread onto the driver? Wouldn't a slightly tapered press fit with a set screw give as good acoustic coupling? Of course this would mean machining off the treads of the driver and then fitting the guide appropriately. But for my limited threading abilities this would be easier.

In my mathematically impaired brain I've wondered if it was desirable to excite the guide, or to have it dead? Inquiring ears want to know....

[rendoman]

Many thanks for the advices!
In the days after xmas i think i'll try to make an internal threading tool from round bar. It's late to buy from aliexpress now, italian post office is like hell (one of 1000 bad services to people ) if i buy now, i will receive in a month. I'm searching for a kit internal + external and insert 60° and 55° (i want to make some sort of reloading dies). I'm searching also for a fish tail, mission impossible here, i went to 5 specialized hardware store but nothing! i have to buy online.

Very impressive on cutting the various profiles or did you just try them for your space? I would think that any time you add a horn, especially of the magnitude you are talking that it will be much more directional than the flat face style. Love to see where you take this based on your other horns!

I hope you'll excuse, my English is not good enough and i got some difficulty understanding, above all the last phrase
I cut on lathe only the tractrix profile for tweeter ( 75mm dia) and now for driver (130mm dia), i built other profiles using paper mache, cement, plaster , steel and vtr ( i really hate resin, lot of dust everywhere and bad smell ). I tried some of these "prototype" in other system and room, i think the first of basic requirements is to have a good room, and at least 1.5/2m of distance from horn.

This type of horn is maybe the most directional you can choose, above all compared to traditional flat face. Someone hates horns, someone loves it... i think horns are a bit bastard If you listen a good horn system, well sounding, it's a pleasure. If you listen some bad approach not to point ... the listening can be difficult...

I experienced that worst thing are: choosing a wrong cutoff frequency, and not paying attention to seal well the horn with driver. As says C-bag the threading solution is maybe more for aestethic reasons than for practical use. As you can see i mark the hole for connecting the driver to the flange, but i'm not sure if it's better to make threading or a "simple" flange with 4 short m8 inox and a short "guide" between horn-flange-driver (1mm dept).
My threading problem is that if I fail , i throw the aluminum bar i fear this!

[C-Bag]

Stefano as we say in English, there's more than one way to skin a cat! You are doing what I tried to do when I was young. Take an idea and almost make it from the ground up. You are in the right place as that's what we do here! It also helps you have the time and resources to do it.

I think all of us have to rely on the mail for special parts. I know I do. I'm lucky Los Angeles is only 200mi. away and I can get things sent here within a couple of days because there is very little here for machining supplies.

So on pic #2 you are gas welding aluminum horn? And you made the big horns in your other pictures? Are the different sections not just for esthetics? But to keep the horns from resonating or to help them resonate? That has always been the "bastard" for me with horns......they are so COMPLICATED! And my impression is the only way to balance the whole system is to have the same efficiency from top to bottom. And to compound all this the ear hears different frequencies differently. Wow, you have really got a complicated project here.

I would have a really hard time getting big pieces of aluminum like In your photos. If it's so hard to get, and press fit would do instead I'm curious why you still want to thread on the guide? I'm not criticizing, I truly am curious about all this stuff.

[rendoman]

In pic 2 it's steel 8\10, even my big horn are made from steel. the reason is cost here aluminum plate and bar are difficult to find and they sold at very high prices ( 40km the nearer shop, 8e \ kg ). I tried to weld a 6\10mm alu plate with oxy-acet and a special flux with criolite, i got the recipe in my manual, but ingredients are not easy to find. really expensive flux and delicate material, when flux is good quantity and quality it's a fraction of second and it makes huge holes, when flux is poor or not in quantity alu makes White oxide cover... I tried because i want to build to my 2 little bikes alu gas tank, the steel one ugly i made, not treated with tankerite or similar is making some rust.

As you say the different sections are not just for esthetics in my big horn, i made 2 horns loaded by one driver, in few words the big and long part cover from 100 to 350\400 hz and the small upper horn cover from 350 to up frequency. You're right! i choose steel and the "floating" Anchorage with silentblock to help them resonate more than a cement type horn. It was a gamble, i bet that above all in lower fq this can help, the mix steel + body shutz + cork gives good performance .
In this days i should receive a microphone for testing the speaker (ecm8000 behringer, with Scarlett 2i2 sound card and dcx 2496 processor), i hope i can do some good measures and adjust the system!


you're right about mixing different kind of speaker and horns, it's not so easy making passive crossovers, but it's not impossibile. With a bit of luck the differences in efficency can be solved using an L-pad resistor or a pot to match other speakers. The big problem in my opinion is the prices of components for making good passive xovers, if you want to make a first order filter bw type for a tweeter, a simple (but good) cap like mundorf makes excellent work with few bucks, but when you have to buy different huge inductors and capacitors for trying some lower (150 to 500hz) cuttoff fq the situation becomes hard, and even harder trying different order of xover... I thinked lot of time, but at the end i decided to buy an active crossover with 3 stereo channel. this dcx 2496 is cheap compared to other hi end filters, it's pro audio, but it sounds good and above all you can change type of filter, delay, cutoff, offset, eq and Others parameters in real time. cons you have to give it one amplifiers for each channel ... but it's not a big problem

now i have to go out, after i try to do a simple image of the flange. the last 2 pics alu plate welded with flux and not grinded. i think with some practice i can weld 1,5mm for gas tank