# 3/8-20 Threaded Rod



## Jesus Hernandez (Oct 16, 2007)

I need some 3/8-20 Threaded Rod 3 ft long. I know the machine is from England. This can be 4140B-7 Steel. Can anyone help, you can pm me. Thanks


----------



## soffiler (Oct 16, 2007)

Jesus Hernandez said:


> I need some 3/8-20 Threaded Rod 3 ft long. I know the machine is from England. This can be 4140B-7 Steel. Can anyone help, you can pm me. Thanks


 

Are you SURE that you need 3/8-20? Apparently, you realize that is a non-standard thread, with standard sized being 3/8-16 and 3/8-24.

A standard thread size that is VERY close to 3/8-20 is M10x1.25


----------



## Jesus Hernandez (Oct 16, 2007)

OK. I can get around it. I can get a 3/8-20 Die. McMaster has them in stock. Thanks Soffiler. It's for a crankshaft milling machine.


----------



## soffiler (Oct 16, 2007)

Jesus Hernandez said:


> OK. I can get around it. I can get a 3/8-20 Die. McMaster has them in stock. Thanks Soffiler. It's for a crankshaft milling machine.


 

OK, as long as you're POSITIVE that it's 3/8-20 and not metric... it would take some very careful measurement to detect the difference between 3/8-20 and M10x1.25.

Crankshaft milling... that's kinda right up our alley... Central Tools has traditionally done a lot of automotive measuring tools for engine rebuilding work (aside from our line of worklights and LED's, that is). I must admit I am drawing a blank on the milling, however. Crankshaft GRINDING, now, that I understand.


----------



## highorder (Oct 16, 2007)

another vote here for the metric thread...

a thread mic or 3 wires are needed here.


----------



## soffiler (Oct 17, 2007)

highorder said:


> another vote here for the metric thread...
> 
> a thread mic or 3 wires are needed here.


 
According to the Machinery's Handbook:

* 3/8-20 UN external thread will measure between 0.3657" and 0.3750".
* M10 x 1.25 external thread will measure between 0.3843" and 0.3937".

So, you CAN tell them apart, assuming you are measuring with a micrometer.

The difference between the 1.25mm thread pitch and the 20 TPI is just 1.6% and is very difficult to see with a typical thread gage (one that looks like a tiny saw).


----------



## Jesus Hernandez (Oct 17, 2007)

The threads are 3/8-20. We machine crankshafts for Aircraft the piston type. We receive rough forging; rough machine; then finish grind. These rough machines came from England. 3/8-20; 1/2-12. We keep them going.


----------



## wykeite (Oct 18, 2007)

Sounds like 3/8" British Standard Fine, http://homepages.tesco.net/~A10bsa/bsfgo.htm


----------



## soffiler (Oct 18, 2007)

wykeite said:


> Sounds like 3/8" British Standard Fine, http://homepages.tesco.net/~A10bsa/bsfgo.htm


 

DingDingDingDing I BELIEVE WE HAVE A WINNER!

Sorry I beat on the metric drum for so long, Jesus. If you guys are good enough to build aircraft engines then I suppose you know how to measure a thread!


----------



## Ron Schroeder (Oct 18, 2007)

20 threads per inch is common for leadscrews, 50 thousands of an inch per revolution. Metric lead screws are usually either 1.0mm or 2.0mm pitch. Never seen one at 1.25mm.


----------



## soffiler (Oct 18, 2007)

Ron Schroeder said:


> 20 threads per inch is common for leadscrews, 50 thousands of an inch per revolution. Metric lead screws are usually either 1.0mm or 2.0mm pitch. Never seen one at 1.25mm.


 
Agreed, but you need tight thread specifications if you wish to attain _precisely _.050" per revolution. Ideally, ground threads. On the other hand, Jesus posted looking for 3' of threaded rod, which I've never seen manufactured to precision tolerances. If Ron is correct, and this is a lead-screw application, I hope Jesus realizes his machine might not be so precise anymore... ah but wait! He also posted that it's a _rough_ milling machine... ah HA!


----------



## tvodrd (Oct 18, 2007)

wykeite said:


> Sounds like 3/8" British Standard Fine, http://homepages.tesco.net/~A10bsa/bsfgo.htm



Uh wykeite, British Standard Fine/BSF are referred to in the motorcycle community as _British Stripped Fine._  (Kinda goes along with Lucas/Prince of darkness.  )

Sorry for the O.T.- couldn't help myself.

Larry


----------



## wykeite (Oct 19, 2007)

tvodrd said:


> Uh wykeite, British Standard Fine/BSF are referred to in the motorcycle community as _British Stripped Fine._  (Kinda goes along with Lucas/Prince of darkness.  )
> 
> Sorry for the O.T.- couldn't help myself.
> 
> Larry


 
Probably why it's so hard to find now.

Jesus, if you need help in getting dies or die nuts let me know, maybe I can help out. Threaded rod is also known as "stud bar" and also studding this side of the pond so you may be able to get some ready made. I'll let you know if I find some.:thumbsup:


----------



## Torque1st (Oct 19, 2007)

Standard threaded rod is usually produced by thread rolling and is a soft steel, hardly 4140. The OD is usually not tightly controlled. Leadscrews are usually hardened and ground.


----------

