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Mr Fixit
01-11-2014, 12:05 PM
Hello group,
I have a 5/8" piece of hot rolled stock that I need to turn threads on just the ends for a project. When looking around I find major diameters of .6250 for NC threads listed, is this before or after the die has cut the threads? I will be using a die and tool holder in the lathe.
Tx for any help.

Mr fixit for the family
Chris :)

Toolguy
01-11-2014, 12:36 PM
For single pointing I like to start with on size material. You can tell when you're getting close to size when the threads have a very narrow flat on the crest. For running a die I like to start about .010 under - .615 in this case. A die that big will take a lot of torque to turn on a blank rod. You might want to consider single pointing most of it, then use the die to finish to size.

duckman
01-11-2014, 12:38 PM
If you have a lathe rough turn the threads before trying to cut the threads by hand.

Mr Fixit
01-11-2014, 01:09 PM
OK I will give it a try. I have never single pointed any theads so I may be back after I read up on how to do this with more questions.
Tx
Mr fixit for the family
Chris :)

Doozer
01-11-2014, 01:13 PM
Go with what the machinist's handbook says,
but without looking it up, I would use .620 major
for a 5/8" NC thread. If you leave it .625 and you
cut and try the fit of the nut, you will get it to fit,
but the pitch diameter gets all jacked up.

--Doozer

DR
01-11-2014, 02:34 PM
Yeah, for sure single point it almost to size. Otherwise the die will be so hard to turn you won't be able to do it. And, without a bit of pre-threading chances are about 99% the die will not start on straight.

Home project? Chances are not a high stress project so .612" diameter would be a good starting diameter.

Wild assumption here, that die is probably not a high dollar, high quality high speed steel (HSS) unit. Under the best of conditions it's not going to cut very well. In other words, don't expect much from it.

Don't forget to use lots of heavy cutting oil with the die, or else....

andywander
01-11-2014, 03:50 PM
The tightest class of thread uses exactly the nominal diameter as the finished major diameter.

cuemaker
01-11-2014, 04:31 PM
The tightest class of thread uses exactly the nominal diameter as the finished major diameter.

This is not exactly true. The tolerance for class 3 threads for 5/8 is .6250-.6213 for the OD. Class 2 fit is .6234-.6113.

With Class 3 you better make sure you mating nuts/hole are correct... Most fasteners fit into the class 2 thread fits..

andywander
01-11-2014, 07:13 PM
This is not exactly true. The tolerance for class 3 threads for 5/8 is .6250-.6213 for the OD. Class 2 fit is .6234-.6113.

With Class 3 you better make sure you mating nuts/hole are correct... Most fasteners fit into the class 2 thread fits..

Yeah, I should have said that it includes the nominal. Thanks for the correction.

TOOLZNTHINGS
01-11-2014, 08:30 PM
If you can single point to get started, finish it with the single point and forget the die. Better fit and finish and now you know how to do it.

wierdscience
01-11-2014, 08:44 PM
For general purpose threading(bolts,assembly studs,stand offs etc) I use a simple formula picked up from somewhere I forgot.

Major dia. x .01

In this case .625 x .01 = .0062 rounded off to .006

.625 - .006= .619"

Doozer
01-11-2014, 09:37 PM
Yeah, I don't know why I see postings suggesting to
start threading in the lathe and then finish with a die?
Like are you some half baked machinist or what?
Do ya start baking something in the oven and then
switch to the microwave to finish it off??

--Doozer

PixMan
01-11-2014, 09:55 PM
I cut all threads over a #4-40 using full form cresting inserts and get PERFECT threads every time. Though I have a thread pitch micrometer and thread wires (for threads over 1"), I rarely have to use them because the full form inserts take the O.D. down from nominal to finished size as the thread pitch diameter is reached.

Here's a tool I used to make an M12x1.25-6g thread (in 316 stainless steel, no less), and the finished thread. You would be hard pressed to get a better quality thread without using a thread grinder!

http://img.photobucket.com/albums/v466/kenm10759/Dads%20shop/DSC_0445-r_zpsc72f81b5.jpg
http://img.photobucket.com/albums/v466/kenm10759/Dads%20shop/DSC_0444-r_zps4b1358e0.jpg

Juergenwt
01-12-2014, 01:07 AM
Hello group,
I have a 5/8" piece of hot rolled stock that I need to turn threads on just the ends for a project. When looking around I find major diameters of .6250 for NC threads listed, is this before or after the die has cut the threads? I will be using a die and tool holder in the lathe.
Tx for any help.

Mr fixit for the family
Chris :)

Since you are using a die to cut - what is all the talk about SINGLE POINTING? Just put the rod in the chuck and if it does not run fairly good than take a light skin cut. Put the die against the material, support it with the tail stock, turn on slow speed and cut.
Am I missing something? Oh - lubricate! The OD is 5/8 - .625. Minus .005 is OK.

Lew Hartswick
01-12-2014, 10:19 AM
Number 1 when doing almost anything with "hot rolled" is remove the mill scale. That stuff is so hard it could
substitute for the hardest abrasive. :-)
...lew...

Juergenwt
01-12-2014, 02:18 PM
Number 1 when doing almost anything with "hot rolled" is remove the mill scale. That stuff is so hard it could
substitute for the hardest abrasive. :-)
...lew...
Lew - I agree.

Mike279
01-12-2014, 04:16 PM
A real sneaky way to start your die is to to thread it onto a scrap bolt and chuck it in the tailstock. Chuck the material to be threaded and bring the tailstock right up to it and snug it down good. Then as you turn the die off the scrap, it is forced onto the piece you want to thread. Once it is started you can move it to a regular vise to finish. By chance I just did a 5/8 -11 rod for a friends minibike fork. It was cold rolled and cut a nice thread fast. Mike