power threading

[clogsParticipant @clogs]

Ctrl/Cmd+V

Hi guy's,

need to ask a dumb question…….

I'm rebuilding a 1928 Citroen and need to make hundreds of nut's and bolt's between 6mm – 14mm……..where possible I will use the modern threads, but the old threads are not easily available and quite a lot I want to use st / steel, 303 grade….besides most of the bolt's are specials……

 

so the question is……without spending hundreds of £'s…….my Colchester Student and Bridgeport (both are 3 phase and run direct from the mains) are too fast I think to cut threads on their slowest speeds, not wanting any unnecessary breakages any suggestions…..I don't mind threading a few by hand……. BUT……any suggestion's please…..

many thanks Frank

[clogsParticipant @clogs]

[Thor 🇳🇴Participant @thor]

Hi Frank,

have you checked out the screw cutting threads on this forum?

Screw cutting made easy and Screwcutting Simplified.

You would have to make either the Snap-Tap or Gray's screw cutting attachment, but it might be worthwhile if you have to turn many bolts.

Regards

Thor

Edited By Thor on 20/09/2013 05:09:24

[clogsParticipant @clogs]

Thanks Thor…….have looked at all those atachements…..would like to see them in the flesh and under power (setting up)……looked at quite a lot of stuff on U-Tube as well and have decided to go down the small three jaw chuck route in the tail stock…..will take a chance on the slowest speed…..I.shall make a drive plate and tube so that it can be mounted it in a collet chuck assy…..(like the idea of a bit of safety, it will spin if there's a problem)….I think the other stuff u recomend might want some setting up – beside I have good HSS dies…I just need to turn up a die-stock holder for the chuck……it all for 4 of those an 6 of another bolt……I guess those atachement would be good for the large dia. stuff or threading bar….

I'm prepared to take a calculated risk.

many thanks Frank

[David JuppParticipant @davidjupp51506]

Remember most commercially produced bolts in 'every day' sizes have rolled threads not cut threads. For any highly stressed bolts that could suffer from fatigue take care.

Also 300 series SS typically much weaker than alloy steels used in HT bolts – may not matter for most, but take care with anything securing safety critical items.

Most fixings on cars probably aren't particularly highly stressed, but just be aware.

[jason udallParticipant @jasonudall57142]

just wondered…who sells thread rolling dia nuts?

use thread rolls at work..love them.. but for home use a bit tasty

[Ady1Participant @ady1]

Two books/threads

martin cleeve and "screwcutting simplified" in here

Cut 1000 nuts and bolts

…and never need to ask anyone anything ever again…

[capnahabParticipant @capnahab]

this chap

has some very nice videos. this one is on 'power tapping'. It may not be exactly what you are after but worth a view.

[colin hawesParticipant @colinhawes85982]

You need to use HSS spiral point machine taps for the nuts. Drill and part off blank nuts and thread them all afterwards.Make sure the holes are big enough or the tap will break.An auto-reversing tap holder is desirable. If necessary for true running locate the nuts for second (tapping) op. on a drill or pin in the tailstock Colin.

[Sub MandrelParticipant @submandrel]

I've seen home made thread rolls in ME. I think they were for threading the spokes of the "otto di-cycle". I think there was enough information for anyone able to make the rollers from silver steel to make their own.

Neil

[Clive FosterParticipant @clivefoster55965]

With 'undreds of threads to do it probably makes sense to invest in the proper kit :- a coventry die head and an auto reverse tapping head. Far, far faster than the hand way and better results too unless you take great care which, for hundreds, is unlikely simply due to the yawn factor.

They come up on E-Bay fairly regular at acceptable, especially considering the time and labour saved, prices. My Coventry head cost around £35 delivered with several chaser sets which I'm slowly adding to. Order of £5 a set being acceptable to me although a couple of paid for jobs got new ones folded into the price. Pollard tapping heads numbers 1, 2 , 4 & 5 came along at £25 to £30 dleiverd so, like any self respecting toolaholic, I had to have them. By no meanseveryday tools but each time I use them I'm reminded why they are high on the list of things that will need prising out of my cold, dead, hands!

Clive

[john swift 1Participant @johnswift1]

if you can find good second hand tooling to produce production quantities

have a look at this – http://en.wikipedia.org/wiki/Die_head

it shows both the Coventry die head and the alternative thread roller

a few years ago , on one visit to small factory factory , I watched an automated capstan lathe roll a 25mm thread in a steel bar faster than a myford 7 can take a 5 thou finishing cut

note –  the rolled  thread diameter is larger than the bar diameter !

Edited By john swift 1 on 28/09/2013 18:51:30

[clogsParticipant @clogs]

OK, I've had enough of this threading by hand, just done a dozen m14x2 bolts (30mm thread length) in st / st…..

so now the new dumb questions :-

1. Have looked at the Cov / D / heads and there are some listed at 3/4 and 1inch, I'm guessing that this is the max thread size that'll go thru ??

2. will say M1.25 thread chaser / cutters cut threads on m6 – m12 using one cutter set or do u need individual cutters for each diameter bolt ??

many thanks Frank

[Sub MandrelParticipant @submandrel]

You're in luck. One set per pitch with a coventry die head, the diameter is whatever you set it to be.

Neil

[Anonymous]

Frank: Correct, the size of the diehead is nominally the largest thread diameter it will cut. It is possible to cut slightly larger fine pitch threads over a short distance if needed. However, it is also recommended not to run a diehead on production quantities of coarse pitch threads at maximum capacity. So, for a 1/2" BSW thread a 1/2" diehead is ok for a few, but for larger volumes it's better to go with a 3/4" head.

On my Coventry dieheads (8 at the last count, plus one for tapered threads) each set of four dies only cuts one pitch and one diameter, and are also specific to one size of diehead. The dieheads have a small amount of adjustment, a bit like a split die. The larger dieheads also have two positions on the detent, one for roughing and one for finishing.

Regards,

Andrew

[Sub MandrelParticipant @submandrel]

I stand corrected!

Neil

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