Thread Rolling

I'm looking for advice on thread forming, I have all the taps and dies I think I will ever need, I also have a couple of die heads with various sets of jaws, However I use a lot of stainless bolts and also some Titanium ones, I am looking at the feasibility of building a dedicated CNC threading machine for bolts, probably based around a small ish Capstan or Automatic lathe, however I want to form the threads rather than cut them so thread rolling would appear to be the answer, max size will be 12mm.
So do any of you have experience of thread rolling and or thread rolling heads etc.

TIA

Shaun

Wow, sounds like a money pit at every level.

Forget automating a capstan and look at an old EMI-MEC Sprint.

You can still get rolling heads from people like Rotagrip. It needs neat cutting oil for best results.

You'd be better off buying them from someone who does this. In any event you need to be looking at 1000+ for it to be worth doing.

You will need some serious HP for stainless and Ti for thead rolling so this might limit the machine you want to use.

You could use progressive heads for stainless but I'd imagine that Ti will work harden that fast it will have to be a one pass operation.

I've had threads rolled on 3/8" stainless thick walled tube (304 & 316), for use on 2000 bar pulsating duty. I didn't handle the direct liaison with the local contractor who did the job, but I can contact the person who did.

I do recall that there were 2 common styles of rolling head - one type used rollers, the other worked more like a plough.

It took a bit of trial and error to find size to machine the tube OD to to give correctly formed threads.

Same process was (still is) used for much larger size tubes (typically in low alloy steels).

In a nutshell. I remember the first time I tried to knurl some Titanium, learned a valuable lesson there. Cut knurls like the Quick work but other than that, not a chance. Not unless you were using some very serious pressure. I would imagine threads would be just as challenging.

graham.

To be honest I figured that it could be a nightmare and require a lot of power, some of the bolts I use cost silly money, I can already make them for less using standard methods, I just don't enjoy doing it, I enjoy paying for them even less, I use a lot of Titanium and stainless bolts, I do more and more work on race bikes and drag racers, 500 quid for bolts on a single is not unusual, I have a small thread rolling machine for motorcycle spokes and surprisingly it easily threads Titanium, this is a long term project which may never happen in the mean time Ill keep my eye open for an automatic lathe with the above in mind.

How about thinking outside the box. ??

Rolled threads tend to have better fatigue resistance than cut threads. Using the wrong thread production method can, and has, had fatal consequences.

Andrew

I once saw someone make an adaptor for a centre lathe where it bolted to the rear toolpost mount and held a Coventry Die Head.

This allowed rapid production of small quantities in a cost effective manner.

High load applications of the product should be tested for safety.

JS, I've actually seen one of those in action, very fast in operation, I've also seen a spoke threader of this type, cuts and threads a spoke as fast as you can blink.

this is the type

https://www.philwood.com/products/tools/spokemach.php

I actually contacted them with a view to buying formers, however they only do them in imperial sizes, I'm still looking at this option which to me is the more interesting method, I could easily automate this.

I have a Fette thread rolling head (triple dies) for size M6-10 threads, that has been used on a 3hp colchester lathe. I have no experience of using this head and know it is a very expensive piece of kit that I do not want to damage! Firstly I am not sure if you set up the carriage on a free sliding basis to have the workpiece pull the rolling head onto itself (after manually pushing the carriage/head onto the chamfered end of the workpiece), or if you drive the carriage/head onto the revolving workpiece by the leadscrew.... Any advice before I try would be most welcome! Secondly, is a 3/4 hp Myford powerful enough for thread rolling, or is it only possible on something like the 3 hp colchester? Thanks

I can see that the dies spring apart when the motion of the carriage is stopped so then the workpiece cannot pull the head any further onto itself - how is this best performed on a manual lathe? Do you set up a stop for the carriage so that when it hits the stop the workpiece forces the dies to spring apart?

Edited By Adam Harris on 21/09/2015 16:50:46

Thanks Jason but I still don't really understand how it should be done on a manual lathe - do I feed the head onto the workpiece with the leadscrew engaged at tpi screw cutting feed (as if cutting) which is very slow? The Fette you tube videos show the head moving extremely fast (but nowhere do they show or explain the head-carriage-bed set up....

As I look at the mechanism it makes me think that the carriage should be free floating and one should set a carriage stop along the bed to determine the length of the thread (at which point the dies spring apart as the head is pulled forward from its shaft which is clamped to the stopped carriage). In terms of engaging the head onto the chamfered workpiece , I am wondering if best to push steadily to initiate a bite or to slam it more forcefully. Have I got completely the wrong idea?

Edited By Adam Harris on 21/09/2015 17:51:47

I have often thought about trying to make a simple tool for thread forming. In essence it would be a little like a conventional scissor type knurling tool but with the rollers threaded at the required pitch. It would be used like a knurling tool but with the leadscrew engaged and change gears to suit the required pitch. Has anyone seen or made such a tool?

Mike

Thread rolling, as far as I remember, was done very fast. We used a capstan lathe with the roller box in the turret.