Single Point Threading = no Depth Gauge Joe P.

[Janderso]

One of my favorite YouTube channels is Joe Pieczynski.
He is a great teacher imho.
As a hobby machinist with little practical experience, I am always learning.
Therefore, I watched this video, “Single Point Threading, Want to do it better?” By Joe Pi.
In this video, Joe says, “If someone walks into my shop and asks, how deep should I cut this thread, throw him out”.
”Threads are not driven by the depth of the thread”.
I guess if you own a thread mic., put it away?
He explained to me the method to use is the 3-wire and follow the machinists handbook and the instructions that come with the thread wire kit.
This experience has given me confidence moving forward with respect to single point threading and learning more about threads.
Did you know the 2A is for external or “air” threads? did you know the 2B threads are for the “bore” or internal?
I do now.
The pics show my latest project, a smaller machinists jack. I cut the threads 5/8 x 18 UNF. I’m I followed the 2A specs. I put it in the imaginary mail and received the external thread portion to fit into my internal machinist jack base that I cut using a commercial tap.
It fits perfectly with no slop and smooth as glass. Did I get lucky or is this why there are published standards.

 

[ttabbal]

As I understand it, and I'm a noob too, thread mics measure the same thing wires + mic do, the thread pitch diameter. So they should be equivalent when it comes to accuracy.

The how deep to cut is when people want to go to a certain depth of cut on the dials or DRO. It's a close approximation a lot of the time, but can lead to parts that don't thread to standard fasteners.

Nice job on the jack. I'd like to make some myself sometime.

 

[jaek]

Looks pretty good!

FWIW a thread mic measures the pitch diameter (quality of fit) directly, just like the three-wire method. No need to throw it away.

Thread depth depends on major and minor diameters which aren't as critical. It's the reason "75% thread for aluminum, 50% thread for steel" thing works.

 

[mikey]

You did a nice job on your jack!

Have to agree that Joe Pi is a great teacher, and I really like his personality - confident, capable and direct.

Thread wires are actually very accurate and capable of being more accurate than most thread mics that read in the thousandths. More accurate because you can read wires to the tenths with a tenths reading mic. However, wires are a serious pain in the butt and I hate them so I don't use them. A thread mic is far more convenient to use, is direct reading and is more than accurate enough to obtain excellent thread fits.

There is a LOT to know about threads, thread fits and cutting threads. Took me a long time to understand it but then again, I'm slow. You might look into the fit classes and learn how to cut what you need, on purpose and to specs. Cutting a class 3A and matching class 3B thread is not as easy as it looks because you are cutting and measuring to tenths. On smaller threads, like a class 3 10-32 thread, the OD of your blank and the thread pitches are within a few tenths and you have to be able to work at that level of accuracy. Looks easy on paper, not so easy at the lathe.

Take your time and maybe look into grinding a good HSS threading tool. It will make your life so much easier and your thread form will be much cleaner.

 

[Janderso]

The one thing that still has me baffled, how do you assure you are cutting accurate internal threads? Is a bore gauge the only way?
I work alone, I don't ship my parts off to a job offsite. I make fit and finish adjustments on the fly so it's easy for me to start checking fit when I'm getting close to depth.

Looks pretty good!

FWIW a thread mic measures the pitch diameter (quality of fit) directly, just like the three-wire method. No need to throw it away.

Thread depth depends on major and minor diameters which aren't as critical. It's the reason "75% thread for aluminum, 50% thread for steel" thing works.

Now that you mention it, you are correct. I had forgotten you need to change the adapters for different thread pitches on thread micrometers. I don't own one so I am unfamiliar with them.

 

[benmychree]

For nearly all my threading, I use the threading tools from Aloris, they are made in several sizes according to the width of flat at the point of the tool, they are sharpened only on the top, and last a very long time. Yes, thread wires are a PITA, and I seldom use them, and then, only if my thread mikes are too small, then I go to my old shop and borrow the larger one. I think one can read a .001 thread mike to within a few tenths by approximation, I have never had to make anything closer than that. At my old shop I had a collection of thread ring gages, and used them to fit most threads.

 

[benmychree]

The one thing that still has me baffled, how do you assure you are cutting accurate internal threads? Is a bore gauge the only way?
I work alone, I don't ship my parts off to a job offsite. I make fit and finish adjustments on the fly so it's easy for me to start checking fit when I'm getting close to depth.

Now that you mention it, you are correct. I had forgotten you need to change the adapters for different thread pitches on thread micrometers. I don't own one so I am unfamiliar with them.

Most of the thread mikes that I have seen do not have interchangable anvils, they only work for a range of pitched, in 0-1 there are three mikes for the whole range of threads. For gageing internal threads, a thread plug gage is used, you just screw it in and feel for the fit; like the external gages, they come in GO and NO GO styles, varying in pitch diameter, one should screw in or on and the other should not.
I have made my own plug gages for such as my lathes with screw on chucks, so that when I need to make a backplate for a chuck or whatever, I use it to fit the internal thread. It is made to the exact pitch diameter as the lathe spindle, using a thread mike. Having said that most of the thread mike that I have seen do not have interchangable anvils, when I had my shop downtown, I bought three of them (up to 3 inch) made in Poland, and used them a good bit; I can still borrow them if need be.

 

[mikey]

The one thing that still has me baffled, how do you assure you are cutting accurate internal threads? Is a bore gauge the only way?
I work alone, I don't ship my parts off to a job offsite. I make fit and finish adjustments on the fly so it's easy for me to start checking fit when I'm getting close to depth.

The vast majority of threads we make in a hobby shop will be class 2 threads. We can cut the external thread and then cut the internal thread so that it fits the external one we made. This is how most of your threads will be made. If you need a class 3b thread then the best way is to make (or buy) a go/no-go gauge. You will not do this often but if you have to have it, this is how you do it in a hobby shop.

 

[brino]

Jeff I always enjoy Joe Pi's videos.....and your posts......

It fits perfectly with no slop and smooth as glass. Did I get lucky or is this why there are published standards.

I believe it's simply that you are paying attention, learning, and getting great at it!
I need more shop time......

-brino

 

[mikey]

Most all modern thread mics now have interchangeable anvils. Gone are the days of the beautiful Starrett and Lufkin fixed standard thread mics. My Tesa set, Mitutoyo, B&S and even the cheap Chinese ones all have interchangeable anvils. Aesthetically, I don't think the more modern tools are better but changing anvils is a lot cheaper than having separate mics.