Thread turning tool.

[KimB]

Been a long time since I’ve done any thread turning but on my little Ransomes project I need to re make some gearbox shafts that are badly worn.
I tried to use a die but It broke it.
One thread is a 3/8 x 20 bsf, the other is a 5/8 x 14 bsf.
It’s been a long time since needing to source tooling so I’m just wanting some advice really.

Going off my engineers black book.
For the 3/8 thread I think I need something like 16ER20W it may however be a 16ER2055

For the 5/8 thread I assume it’s 16ER14W or maybe a 16ER1455

I’m cutting threads into bits of silver steel just fyi.

Finally where do people source tooling from like this.
Thanks

 

[Seadog]

You could single point cut it using a piece of HSS ground to 55 degrees, not to full depth, then finish with a die. One tool does both. I've started to use HSS recently, where I was only using insert tooling. It definitely works very well on some steels, silver steel being one in particular. Use plenty of lube.

 

[Rrobson]

Must admit, for stuff like that I’d be rummaging through my HSS box and grinding something appropriate up. Unless I was planning on making lots of any particular item I wouldn’t be buying any tooling. Plenty of lubricant and you will easily attain a good finish and thread form. Plus the one piece of HSS would do both with a little intermediate grinding

 

[pressbrake1]

I search eBay, I don’t think I’ve ever bought a threading insert any other way!

 

[Milkybars]

Given the cost of tips and suitable holder for this ..@seadog suggestion is the best option.
I definately have a 3/8" BSF die you can have ..I'd need to check on 5/8"

 

[striker]

When I made my new leadscrew for my mill, trapezoidal 26mm, I was thoroughly confused by insert tooling. I just ended up grinding my own from HSS.. it worked really well and I wouldn't hesitate to do it again..

 

[Seadog]

The 1/2" UNF thread on this chuck adaptor was single pointed with HSS. It actually looks like s**t in the photo

but the roughness is swarf. I wire brushed it and it was a nice clean thread.

 

[KimB]

Thanks you all. I’m going to check what hss I have but I’m sure I’ve got something good enough for doing that! I completely overlooked making one.

 

[KimB]

Given the cost of tips and suitable holder for this ..@seadog suggestion is the best option.
I definately have a 3/8" BSF die you can have ..I'd need to check on 5/8"

Thanks for that. I did have a full bsf set till my 5/8 broke . Pretty annoying and I needed it to clean some threads this evening. I’m going to order one in the morning so I can clean threads up next week.

 

[Erie Fred]

You could single point cut it using a piece of HSS ground to 55 degrees, not to full depth, then finish with a die. One tool does both. I've started to use HSS recently, where I was only using insert tooling. It definitely works very well on some steels, silver steel being one in particular. Use plenty of lube.

I would single point all the way, and not use a die.
Didn't Kim snag that die head for sale the other day ?

 

[Seadog]

The advantages of single-pointing then chasing with a die, are that you don't need to set the compund accurately (set it under 27°), and you don't need to cut full depth, so the die will give you the correct thread profile. Remember that split dies are adjustable.

 

[Seadog]

I've a piece of 1/4" HSS ground 55° one end and 60° the other.

 

[Kram]

I dislike using self ground HSS for threading, much prefer inserts!

Wouldnt say its expensive for carbide. You can get a cheap external holder for about 5 quid, and new, decent inserts are about £5 delivered.
For general use, buy an AG55 insert, that will do most UK imperial threads. AG60 for metric. £15 will set you up for most external threads..

However you will get better results using full profile inserts which are pitch specific.. 16ER 20W/ 14W. I get the full profile if its a common pitch I willl use often.
Another advantage is there is a chart I use which gives the infeed depths for full profile inserts and it generally gives a perfect thread every time ( I like measuring and checking my threads!).

 

[Rrobson]

The advantages of single-pointing then chasing with a die, are that you don't need to set the compund accurately (set it under 27°), and you don't need to cut full depth, so the die will give you the correct thread profile. Remember that split dies are adjustable.

This is good when you don’t have provisions to accurately grind up your HSS. I have also done this in the past to clean the last bit of the thread when the finish was shocking… sometimes certain materials don’t take kindly to slow speed single point threading so a die can work wonders!
Could also chase it with a hand chaser to fettle the last couple or thou and achieve the correct thread shape. Are those still a thing anymore?

 

[Guineafowl]

Could also chase it with a hand chaser to fettle the last couple or thou and achieve the correct thread shape. Are those still a thing anymore?

I’ve had some good results with these for getting the correct rounded Whit form after using a single point. Once you’ve cut the correct depth, run down the thread on low speed with one of these rubberised abrasives and it will conform to the thread and act like a universal thread shaper.

Edit: You might need to run a flat file over the crests to make a flat spot, which these ^^^ can then turn into a rounded crest.

 

[Erie Fred]

The advantages of single-pointing then chasing with a die, are that you don't need to set the compund accurately (set it under 27°), and you don't need to cut full depth, so the die will give you the correct thread profile. Remember that split dies are adjustable.

My concern is the OP is not dealing with mild steel, and may work harden it while single pointing it, along comes the die, and
being a very light final cut, get's chipped/broken.

 

[RichardM]

If your silver steel is annealed, I'd just use HSS tooling, finish off with a couple of spring passes and 320 emery tape for the crests. Use cutting compound (Trefolex in my case as I was given a tub years ago).

 

[Rrobson]

@Erie Fred If the silver steel isn’t in an annealed state you’d have a hard job machining it with anything other than ceramics or cbn… so I was assuming it was in the annealed state
I think some close grain specialist carbide will tolerate hss / tool steel / hardened silver steel but otherwise it’ll be super hard tooling for the job and then your talking mega money!