Here's a thread for those new to threading :)

[precisionworks]

http://www.metalartspress.com/PDFs/60_degree_threads.pdf

 

[wquiles]

Very good reading material - thanks!

Will
(still not following step 4 for Al as it regards to the 30 or 29.5 deg :devil

 

[darkzero]

(still not following step 4 for Al as it regards to the 30 or 29.5 deg :devil

Why? :thinking:

 

[wquiles]

Why? :thinking:

Short answer: because it works great.


Long answer:
I understand the science/reason behind the need of the 29.5 deg angle, which has to do with various factors including the stress on the metal being cut/sheared, the finish after each pass, and also on the cutting edge. Given that I like to experiment I actually have tried cutting threads both ways, but for these soft Al hosts, I did not see an advantage.

The other reason is that it seems to work better than good enough: I have had experienced machinists evaluate and comment that my threads are great - they don't even know I cut them straight. I now have close to 100 customers (many repeat buyers) of my 1xD's telling me my threads look/work great; so if my customers are happy, I must be doing something right.

That being said, I have a very nice threading tool with coated inserts that works great and stays sharp time after time (probably have about 40 thread jobs on the same edge right now):

Since I have done so many of these thread jobs, I have developed and fine-tuned my own method/pace while cutting threads, I use a kerosene-based cutting fluid, and I typically cut no more than 5-6 mills on each of the initial passes, and even less as I go further. At the end, I am doing a 1 mill pass, and then a 0 mill pass (meaning like a spring cut; I cut again at the same value as last time - easy to do with the DRO), and this seems to clean up and polish the threads quite a bit as well.

It took me many, many tries and experimentation to get a "system" or methodology that works for me, my lathe, cutting tool, and these Mag Al hosts, but after a light pass of a scotch pad, and I end up with this:

Try it. You might be very surprised how well they look/work

Will

 

[precisionworks]

30 or 29.5 deg

Actually, the preferred angle can be any angle from 15° to 29.5°. Most people use 28 or 29 degrees, as it is difficult (on smaller machines) to split one degree.

By not using 30+30 (say 28+32) there is more metal removed on the leading edge of the tool, but still some metal removed from the trailing edge. Since the chip is uneven in thickness, it tends to break nicely. See "modified flank" below.

If you set 30+30, the threading tool is being pushed into the cut just as if it were a form tool. As the thread form is being finished, there is full contact on both side of the tool, which increases the tendency to chatter - especially when doing internal threads where the tool point may be some distance out from the tool post. Since chip thickness is equal on both sides of the cut, the chip may not want to break. See "radial" below.

The machine can also be set up for a flank cut (middle drawing) although it is not often used.

On edit: Will is using a radial cut (30+30), or "straight in". Most people use the modified flank, so the tool feeds more toward the front as it is being fed into the work. I'm not surprised that Will is getting nice results on aluminum, but wouldn't expect to see the same smooth finish on harder steels or Ti.

 

[darkzero]

but wouldn't expect to see the same smooth finish on harder steels or Ti.

Thanks for those pics Barry! Gives a whole new perspective & understanding seeing what's actually going on in pics rather than from reading or being told.

Although brass is easy to cut it's much denser than alumn I can actually see the difference when cutting at 29 deg & 29.5 deg especially when cutting internal threads like you mentioned. I was also taught to thread at 29.5 deg but I like threading mostly at 29.

Try it. You might be very surprised how well they look/work

Will

Thanks Will, I've always wondered. I have tried it on alumn & brass. I agree that on alumn I can't tell any difference. I still prefer 29 deg & I've been threading a lot of other metals other than alumn so I just leave my compound there. Plus it's just easier/quicker for me to use my reference numbers for DOC at 29 or 29.5 deg for reference for whatever pitch I'm cutting. I'm all in for any time saved having to calculate for the threads that I don't cut on a regular basis. I've been using Tap Magic Alumn for alumn & brass & Boelube for steel, SS, & Ti & I've been very happy. As you said, whatever works & what one is comfortable is all that matters. :twothumbs

To add & not that it matters I use Carmex threading tools. Although I was not taught this way in shop class (learned from someone else), for internal threads, I still leave my compound angled to the right as if I was cutting external threads. I mount my internal threader "upside down" & cut on the opposing internal surface. This also helps chips not to build up at the tip inside the work for smaller diameters close to the size of my threader. Also allows you to get a better view of the work in progress.

While I'm at it, some other pics of another build....

 

[bluwolf]

Don't know what to say. Thanks again Barry.:twothumbs

Mike

 

[wquiles]

Plus it's just easier/quicker for me to use my reference numbers for DOC at 29 or 29.5 deg for reference for whatever pitch I'm cutting. I'm all in for any time saved having to calculate for the threads that I don't cut on a regular basis.

I will be the first one to admit that the way I am cutting threads should not be used on anything other than Al. One of these days when I have fewer projects pending I will spend the time to learn the reference numbers/DOC for the 29.5 and like you just leave the compound at that angle, but for now like you said, it just works well. I also have a full profile 20 TPI internal threading insert for my threading tool that would be perfect for these 1xD's, but again I have not had the time to play with it since I bought the insert over a year ago!

To add & not that it matters I use Carmex threading tools. Although I was not taught this way in shop class (learned from someone else), for internal threads, I still leave my compound angled to the right as if I was cutting external threads. I mount my internal threader "upside down" & cut on the opposing internal surface. This also helps chips not to build up at the tip inside the work for smaller diameters close to the size of my threader. Also allows you to get a better view of the work in progress.

Awesome photos dude - very nice finish on those brass parts :twothumbs

 

[PhotonFanatic]

{deleted content}


While I'm at it, some other pics of another build....

Hi Will,

Nice pics and nice work, but I have to ask: Why are you using brass for your light engines, other than for its looks?

The thermal conductivity of brass is far worse than that of aluminum, or of copper.

Thermal Conductivity Btu / (hr - ft -°F)

• Copper -- 231
• Aluminum -- 136
• Brass -- 69

Admittedly, brass may be fine for many drive current/LED combos, but why not use the superior metal all the time?

Of course, if money were no object, sterling silver would be even better. :devil:

 

[cmacclel]

Hi Will,

Nice pics and nice work, but I have to ask: Why are you using brass for your light engines, other than for its looks?

:devil:

Probably because you can solder to it

Mac

 

[PhotonFanatic]

True, but that won't help the thermal transfer issue.

 

[jhanko]

Thanks for the link. Lots of good information there.
I am also guilty of sticking with the straight infeed method. It works for me just fine, and this is on 6AL-4V Ti. I've cut over 100 thread joints so far in titanium and they all turned out great. I tried the angle infeed method and the results were no better or no worse and I'm still using the first points of my laydown inserts. so tool wear is no issue. The required slow cutting speeds on manual lathes makes the advantages of angled infeed a moot point. The key is proper setup & taking your time. I realise that taking you time isn't an option when running as a business, but I'm at a hobbyist level.

 

[niner]

Thanks for the link. Lots of good information there.
I am also guilty of sticking with the straight infeed method. It works for me just fine, and this is on 6AL-4V Ti. I've cut over 100 thread joints so far in titanium and they all turned out great. I tried the angle infeed method and the results were no better or no worse and I'm still using the first points of my laydown inserts. so tool wear is no issue. The required slow cutting speeds on manual lathes makes the advantages of angled infeed a moot point. The key is proper setup & taking your time. I realise that taking you time isn't an option when running as a business, but I'm at a hobbyist level.

I don't know anything about threading. But Jeff, I have to agree with you. I have your light in my pocket everyday. I just took it out and turn the body. YES, it is butterly smooth:twothumbs

 

[precisionworks]

The required slow cutting speeds on manual lathes makes the advantages of angled infeed a moot point.

I've got to disagree on that point ... especially in tougher materials (Ti) or harder steels (4140 prehard, tool steels, etc.)

If you've ever used a form tool, you know that the deeper the tool gets into the cut the worse the tendency for chatter becomes. Sure, you can work around this by taking very light finishing cuts as the thread approaches full form, although it takes much longer to produce the same surface finish generated by the modified flank infeed. Longer times may not matter, and some people take great pride in how much time it takes to make something, but it is a less efficient way to get the same result.

Modified flank threading is not a new idea. Sandvik has a good, one page tech guide on threading:
http://www.coromant.sandvik.com/san...us01154.nsf/LookupAdm/BannerForm?OpenDocument

Changing the angle of the compound from 30° to 29° does not sound like it can make that big a difference, but the devil is in the details. You won't find any production shop that uses a 30° compound setting, because of the problems with the equal thickness chip, chatter, and surface finish. Even if your "production shop" is a lathe & a mill in the garage, that's not a sound reason to use a method that has proven to be less than optimum for many thread pitches and materials.

Straight in feeding (radial infeed) is the method of choice for some situations. If the thread pitch is very fine, meaning a pitch less than .059", it is the method most used. For these tiny threads, I've ground a couple of HSS thread profile tools.

 

[precisionworks]

I mount my internal threader "upside down" & cut on the opposing internal surface.

+1

Also a great way to bore a small diameter part.

 

[Tekno_Cowboy]

I've got a 4-in-1 tool from Mesa-Tools that I've been contemplating using for internal threading in reverse. This would completely eliminate the chances of running my compound into what I'm working on.

 

[darkzero]

Probably because you can solder to it

Mac

Exactly the reason. The Aleph LEs (with the exeption of the e-screw part) are also made of brass, they're just nickel plated. I know brass doesn't conduct heat well but making a can like this in alumn would pose an issue with grounding the driver as there's no room for a threaded hole for ground. I could have made the LE like TnCs alumn cans but that probably wouldn't have been as easy for me right now.

The LE is for an A2 style head. Since the emitter won't be positioned in place by resting against the reflector, since I'm using a XP-G, I made an extended can to sit where I need it to in the head. I could have made a spacer like I did here to position the LE where I needed it but the owner of this particular light wanted two LEs that he could swap back & forth. I wanted to make it so he wouldn't have to remove a spacer everytime he wanted to swap to the other LE.

The LE will be running 1A & the host is an "exotic" Ti host. Yes 1A, brass, & Ti is not a good combo but it's shouldn't be an issue & I doubt the owner will be using this light in critial situations. It still will be very usable light.

EDIT: Is there another way I could have made the can like this in alumn & attach ground without having to use electrical conductive epoxy?

 

[darkzero]

Thanks for the compliments, hope to be just like you guys someday.

One of these days when I have fewer projects pending I will spend the time to learn the reference numbers/DOC for the 29.5

No worries Will, I'll make it easy for you (but don't tell anybody this).

Here's my contribution to this thread (pun intended)......

This is what helps me to do threading so easily & quickly. Again I use this just for reference as every machine will differ on how accurate the compound's leadscrew & dials are. So for 20 tpi at 29.5 deg, DOC should be 0.0373".

Also good to know (I have not actually tried it to verify yet though): With the compound set to 30 deg, side movement of the tool is half the amount of the compund feed. So at 30 deg, feeding the compound in 0.010" will cut 0.005" from the end of the workpiece.

EDIT: There's got to be a calculator for this, anyone know where to find one? (Nevermind, found an easy solution)

 

[darkzero]

Thanks to the help of my little brother, we've made a spreadsheet that makes it even easier. All you need to do is enter in thread pitch & compound angle. Also added for metric thread to automatically convert to inches. Can't get more easier than this.

Here are two screenshots showing no values entered & with values entered. I can't host the file so if anyone is interested please email or PM me you email if you would like a copy. If someone would like to host it, that would be even better.

Hope you guys might find it useful cause I think it sure is.

 

[PhotonFanatic]

Will,

You can put it up for public access at GoogleDoc.com

BTW, you really need two DOC's for any particular pitch--one for internal threads, as well as external threads.