Thread rolling a bolt - GIF

[Altair]

Thread rolling a bolt.




Previously:

Thread rolling cylindrical dies - GIF
Thread rolling machine - GIF
Machining a multi-start thread - video
Threading a large shaft - GIF
Auto-retracting thread cutter - video

[mdhatter3]

Interesting but not sure about the safety of wearing the gloves

[Frank S]

Those look like bolts for attaching the cutting edge on toe mold board of a plow or grader blades.
As to the wearing of gloves near things that spin, most of us are of the opinion that gloves are taboo, but there are times when having gloves on is safer than being without them my fingers are so calloused that I can not use fingerprint activation devices. I can imagine what this person's finger tips would look like after doing this day in and day out for a period of time without gloves

[old kodger]

I agree with frank, my finger prints have got so many "extra bits" that you'd be hard pressed to identify them after years as a welder picking up hot things (and I don't mean women)

[Toolmaker51]

Aside from gloves.......

This demonstrates why rolled threads surpass cut threads; there is no significant material reduction. Grain of the material [lengthwise] flows into prescribed thread form; rather grain being removed to form same contour. Essentially a knurling operation, the fastener body is slightly under-size in proportion to eventual major diameter.
The rolls upset the crest and root into shape under considerable pressure.
Other benefits are very smooth surfaces that torque accurately and consistently, work hardening of the entire thread form, less deviation between lots, and of course high rates of production.

[cmarlow]

OK, 3 things I do not understand. First, does the bolt get longer when the threads are rolled? Second, if the bolts are high strength do they need to be soft for rolling then heat treated after? And finally the biggest confusion, why is the bolt not drawn in or pushed out as the threads are being rolled?

[Toolmaker51]

OK, 3 things I do not understand. First, does the bolt get longer when the threads are rolled? Second, if the bolts are high strength do they need to be soft for rolling then heat treated after? And finally the biggest confusion, why is the bolt not drawn in or pushed out as the threads are being rolled?

Bolt does somewhat lengthen. Look at end of a common hex bolt, evidence is shallow cup. The body not so much, mainly the exterior a bit under minor diameter.
The hardness condition depends on bolt grade, material and quality control. Socket head screws are high on the scale in all three. Down in Gr 2, doubtful they even get stress relieved.
The fastener is kept from screwing out by contra-rotation, [not clock direction, but one climbing, one conventional] but both rolls are same right or left hand, the work is on a rest with body just under centerline, to be ejected or pops out as diameter is reached. Bigger pitches probably need a end stop too, because process time is barely longer.

I doubt many are hand fed, I'm sure a vibrating hopper orients and feeds blanks.