Axial Thread Rolling

For producing long threads, or threads without run-out restriction, RSVP axial rolling heads are the ideal selection. Axial heads feed on from the end of the part and require one revolution of the spindle for each pitch of thread to be produced. Controlled forward axial motion, either by cam or CNC feed, are recommended although manually operated lathes can also give excellent results. RSVP axial heads are self opening and require an external closing action to reset them. Right hand rolling heads are required for rolling right hand threads and the spindle direction must also be right hand. Left hand threads require corresponding heads and spindle rotation.

How To Order

Selecting The Correct
Thread Rolling Head
There are two main factors that govern the choice of thread rolling head:

1. The thread size has to be within the standard capacity of the thread rolling head.

2. There must be sufficient clearance within the machine for the head to operate.

On Axial Head pages the range of the thread rolling heads is illustrated, showing the outline dimensions and standard thread sizes for each head. Left hand and rotating versions of these heads are available in all the standard sizes. Special high-helix heads can also be supplied to accommodate Acme and multi-start threads.


In order to produce a 7/16 - 14 UNC stud, there is a choice between the RA-1, RA-2 and RA-3 heads. This choice may be limited by the clearance on the machine so it is most important to know the maximum diameter and projection available. If the maximum diameter that will clear when the machine turret indexes is 3.75", then the RA-3 head, at 4.60" diameter, is no longer a viable option. The choice between the RA-1 or the RA-2 should then be made with consideration given to any other threads that may need to be produced on the chosen head. If 7/16 UNC is the maximum thread size required then the RA-1, with a range of 1/4 UNC up to 7/16 UNC would be the recommended choice. However, if thread sizes above 7/16 UNC are required then the RA-2, with a range of 5/16 UNC up to 5/8 UNC, should be selected. Having selected the appropriate thread rolling head, please specify the required shank diameter from the options available.

Selecting Thread Rolls

When ordering thread rolls it is important to specify as much information as possible about the rolls and the application so that the correct rolls may be promptly supplied. The minimum details required are as follows:

The full thread specification (e.g. 3/8 - 16 UNC, 7/16 - 20 UNF, 1/2 - 14 NPSM, 1/4 - 19 BSP)

The thread rolling head for which the rolls are required (RA-1, RA-23, RA-01 Etc.)

The lead required on the rolls (1K standard short lead, 2K standard long lead, or other special lead)

Using the 7/16 - 14 UNC stud example, to be produced using the RA-2 head, the final order would read as follows:







Should there be any doubt about the type of lead required on the rolls, or the size of head to be used, please provide our technical department with a component drawing so that we may make our own recommendations. Test samples may be produced with customer's material on special request.

Thread Rolling Advantages

Thread Rolling Introduction


Axial Threading Seminar


Thread Rolling Application Guide

Where is Thread Rolling Being used?

The Assembly Of Thread Rolls Into The Head

Adjusting The Axial Head To The Threading Diameter

Obtaining The Correct Thread Length

Preparation Of The Component Part

Maintenance & Problem Solving

Carbide Bushings

Axial Threading Heads

  RA-0 - Overview & Components
RA-001 - Overview & Components
RA-01 - Overview & Components
RA-1 - Overview & Components
RA-12 - Overview & Components
RA-2 - Overview & Components
RA-23 - Overview & Components
RA-233400 - Overview & Components
RA-3 - Overview & Components
RA-34 - Overview & Components
RA-4 - Overview
RA-45 - Overview
RA-5 - Overview
RA-56 - Overview


Problem Solving

Rolling Speeds

Axial Helix Charts - Lead Angles


UN Threads - 80 to 24 Threads Per Inch


UN Threads - 20 to 4.5 Threads Per Inch


Metric Screw Threads M Profile - 0.30 to 1.25 Pitch


Metric Screw Threads M Profile - 1.50 to 6.00 Pitch

Recommended Blank Diameters


UNF & UNC - Class 2


UNF & UNC - Class 3


Straight & Metric Threads

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