Threading a long rod and keeping it straight.

[terryd]

All the above reminded me of this item for turning slender rod and perhaps if you had a few to do it might be possible to adapt the idea to support the threaded diameter behind the die???

John B

Hi,
The tailstock holder which I posted a picture of earlier has an 8mm hole all the way through to the headstock which controls any whip in long slender rods. I have batch produced threaded 5/32 rods (4mm) BSW (approx #8-32 UNC) which are 11.5" long without any drunkenness in the thread, so I don't think that this is a problem with a decent tailstock die holder. I can use this system for up to M8 (5/16") threads, above this I use single point threading. I wouldn't use single point threading for small threads as quality split dies are available at reasonable prices. I find that brass cuts beautifully

There is a Youtube video showing a long thin threaded rod (for Meccano use) made using my tailstock holder here





Above - the Meccano coupler on the threaded rod is internally threaded and 1.125" long, thread 5/32 BSW.

Above - here I am cutting an M2 (2mm - just smaller than #2-64 UNF) thread

TerryD

 

[JohnBDownunder]

Hi,
The tailstock holder which I posted a picture of earlier has an 8mm hole all the way through to the headstock which controls any whip in long slender rods.

Hi,
The bit about the 8mm hole through to the headstock had me scratching my head a bit.

Did you mean through to the tailstock end which would work if your tailstock was continuous bore I guess.
My little 7x12 Seig clone has a blind outer end where the screw handle attaches to the tailstock quill. Kinda defeats the through hole idea.

Just trying to picture the process. I don't have the need to thread a long slender rod as yet but if I did I would likely use an ER32 collet chuck and feed 25-30mm a time through the collet and as my little lathe is under-powered at very low revs would be turning the spindle by hand crank so whipping would not be an issue.
Regards,
John B

 

[terryd]

Hi John,
My Boxford (South Bend clone) also has a closed end on the tailstock but the 'quill' can be wound out as far as needed to accomodate around 5" max of rod and the die carrier is around 5" long and can slide to about 3/4" of the carrier rod which is bored as is it's morse taper giving a total capacity of around 13 - 14" so in total there is quite a lot of leeway for long rods. Don't get me wrong, I don't use that maximum often, only for special orders such as long Meccano screwed rods which were originally made to an 11 1/2" length. Having said that it is a useful facility when needed. As you can see from my pics above it is also useful for short tiny threads as well. I really struggled before I took the plunge to make and I don't know how I would now manage without it.

I should also point out that I keep the main size dies which I use the most permanently in the interchangeable die holders which are interchangeable. I often make a new holder as I add extra dies rather than swapping them and as there are several sizes of die I make their holders to suit. They only take a few minutes to make.

TerryD

 

[BaronJ]

Hi John,
My Boxford (South Bend clone) also has a closed end on the tailstock but the 'quill' can be wound out as far as needed to accomodate around 5" max of rod and the die carrier is around 5" long and can slide to about 3/4" of the carrier rod which is bored as is it's morse taper giving a total capacity of around 13 - 14" so in total there is quite a lot of leeway for long rods. Don't get me wrong, I don't use that maximum often, only for special orders such as long Meccano screwed rods which were originally made to an 11 1/2" length. Having said that it is a useful facility when needed. As you can see from my pics above it is also useful for short tiny threads as well. I really struggled before I took the plunge to make and I don't know how I would now manage without it.

I should also point out that I keep the main size dies which I use the most permanently in the interchangeable die holders which are interchangeable. I often make a new holder as I add extra dies rather than swapping them and as there are several sizes of die I make their holders to suit. They only take a few minutes to make.

TerryD

Hi Terry, Guys,

One technique that I haven't used for a number of years, was to feed round bar through the headstock and use a die holder in the chuck. Start the die in the normal way and then transfer the die holder into the chuck jaws. Taking the tailstock off allowed me to make yard long (36 inches) threaded rod quite easily. Squirting cutting oil into the end of the lathe spindle to coat the rod.

 

[ytrose2]

I wonder if there was a way to modify a travelling steady to hold the die in the correct orientation once the initial thread had been started. The free end of the rod could be lightly held in the tailstock chuck for centring. The saddle could then be allowed to travel feely as the thread is cut along the rod whilst the chuck in the headstock is rotated.
Have not tried this, all theory, but it might be feasible.

 

[Tim Wescott]

Wow. I've been away for a couple of days, and I'm getting a huge number of answers -- thank you all (and don't stop helping!)

On cutting & threading in short sections -- d'oh. I'm already cutting it section by section.

Mainer -- the one reference I found called out 0.122", and I tried that without success. 0.120" also still resulted in a bent rod. So I have some learning to do. And the drawing is only representative; I should have pointed that out better. I'm using the same basic design, but I've got a bunch of engines that take a 1/8" or 3.5mm spraybar, so I need a slightly smaller thread (I've even got a few that are officially for 3mm spraybar, but I think I can cheat a 5-44 down to that by taking the tops off of the threads). I've seen drawings for similar spraybars with smaller threads, so I'd at least think it's possible.

I think that I'm going to go get a glass of wine and stare at my lathe for a while, to decide if it'll be easier to make a terryd-style tailstock die holder (which I like because it'll be quick) or a JohnBDownunder-style sliding steady rest. I kind of need a steady rest anyway -- but dang, that tailstock die holder looks nice!

I fly control line model airplanes, and the best cheap engines for that are lightly used plain bearing RC "sport" engines from eBay (mostly Enyas and OS LA series). The port timing is just about perfect for control line stunt, and the plain bearing engines are lighter than ball bearing engines (and seem to hold up well; I have a couple with over 500 flights).

Given that I'm scavenging them from a different market, they come with the RC carb (and sometimes the nose of a trainer airplane) attached, and only need to have a venturi and needle assembly machined for them to make a nice CL engine. Which is a really long way of saying that I need to make a number of assemblies, so having a way to zip out the solution is good.

 

[BaronJ]

Hi Tim,

Thread first, drill second !

A proper tailstock die holder is the way to go for fairly short lengths under 50 or 60 mm. After that single pointing in a traveling steady works.

 

[JohnBDownunder]

Thanks Terryd, Now my head is sorted. I could probably do similar if only I can remember down the years.

 

[Tim Wescott]

So, the point is that the rod and die should rotate with respect to each other, held concentric, and allowed to move along the length. But this doesn't mean that the rod needs to be turning and the die steady.

So what if I carefully adjusted my tailstock so that it slides smoothly on the ways, put the rod in the tailstock, and put the die in the chuck?

I'm going to have to give this a try, if for no other reason than I have all the parts I need for it already, unless it turns out that I should have the die in a pot chuck -- and I know how to make those.

 

[Tim Wescott]

Anyone have a feel for how concentric the rod and die need to be? I'm wondering if I can just toss everything into a 3-jaw and trust it, or if I need to do everything with a carefully dialed-in 4-jaw.

 

[BaronJ]

Hi Tim,

The whole point of using a tailstock die holder is that it will be as close to center when the workpiece is rotating in the chuck.

As I said earlier, I used to thread very long lengths of steel and brass rods by feeding them through the spindle with the die holder gripped in the three jaw chuck. I used to start the thread using the three jaw to turn the rod into the die in the holder, then transfer the die holder to the chuck and continue from there. You did need to hold the rod with mole grips to stop it rotating, but it worked very well. Certainly the guy I made them for was quite happy with it.

 

[awake]

So what if I carefully adjusted my tailstock so that it slides smoothly on the ways, put the rod in the tailstock, and put the die in the chuck?

I think that's what BaronJ was describing in post # 24 above - except that if I understood correctly, he starts the die first.

On edit - BaronJ got his post in while I was typing mine!

 

[BaronJ]

Hi Tim, Andy,

Yes that will work. The reason for starting the thread into the die first is the run out on the chuck jaws will be less than when the chuck is opened up to grip the die holder. Plus the die will start dead square to the rod and stay square when placed in the chuck.

The only difference is I was passing the rod to be threaded through the spindle, through the die and down the lathe bed. I had removed the tailstock.

At least gripping the rod in the tailstock drill chuck it won't rotate whilst cutting the threads, but do use lubricant, even on brass. I use diesel fuel as a cutting oil.

 

[peterl95124]

sorry, the easiest way to thread a long rod is to go buy some "all thread rod", and then screw it into
what ever part it was supposed to be part of. my experience threading just the ends of rods to be
used as long studs for the heads of my V12 is that getting the threads "straight" and concentric
with the rod is a hit-or-miss proposition even with a tailstock die holder, therefore something
requiring even longer threads is problematic, and if really necessary will require single-pointing
rather than cut with a die (and since you imply lengthy threads, will also require some sort of
steady-rest, which...). HTH, YMMV, etc.

 

[SmithDoor]

I single point first then use a die for finishing.
For long threads use a follower rest and single point thread

Dave

I'm trying to make needle valves per the drawing below, and I keep screwing up the spraybar.

Basically, I get a nice machined straight brass rod, but as soon as I thread it I end up with a nice, threaded, gracefully bent, brass rod.

How do people do this? I'm currently using a die in a holder, held in my hand -- if I made up a die holder to be held in a chuck in my tailstock would it work? I've considered trying to single-point machine it, my lathe isn't well set up to make such a cut in such confined quarters (but I'll figure it out, if it's the only way to make it work).

(Edit: I'm trying to tap it at 5-44 -- is that just too coarse a thread?)

Thanks.

View attachment 116075

 

[BaronJ]

Hi Peter, Dave, Guys,

Roller die boxes were made to produce long lengths of thread as were Coventry ones. The threaded rod or stud bar as it is sometimes called is made in this way.

Single pointing wins hands down for odd size threads but does require special techniques to be used for slender or long pieces.

 

[SmithDoor]

That type good but cost setup is great.
But most of work here is ones and two's. Maybe a haftdose parts. So a die works esely do 100 part run even 1,000's parts.

Single point works great for hand full parts but most time you find dies that are low cost.

Dave

Hi Peter, Dave, Guys,

Roller die boxes were made to produce long lengths of thread as were Coventry ones. The threaded rod or stud bar as it is sometimes called is made in this way.

Single pointing wins hands down for odd size threads but does require special techniques to be used for slender or long pieces.

 

[terryd]

sorry, the easiest way to thread a long rod is to go buy some "all thread rod", and then screw it into
what ever part it was supposed to be part of. my experience threading just the ends of rods to be
used as long studs for the heads of my V12 is that getting the threads "straight" and concentric
with the rod is a hit-or-miss proposition even with a tailstock die holder, therefore something
requiring even longer threads is problematic, and if really necessary will require single-pointing
rather than cut with a die (and since you imply lengthy threads, will also require some sort of
steady-rest, which...). HTH, YMMV, etc.

Hi Peter,

I would agree with you generally but I make my long threads for Meccano users. The thread is 5/32" BSW and I believe that the stuff now made in Calais is now metric M4. Many users, collectors and builders of traditional Meccano need these threaded parts and it is almost impossible to buy the stuff apart from us specialist makers. Meccano threaded rods were made in varying lengths up to 11 1/2" hence my manufacturing technique and of couse with my tailstock dies I can die cut any thread up to 8mm (5/16) up to that length and they are very straight and take a couple of minutes to set up and make. No sorting out gear ratios, wrestling with setting them up, perhaps finding an interposing conversion gear for another system, grinding tools or finding a stockist, driving around to collect or waiting on some courier to deliver. I simply make what I need, when I need it.

By the way my tailstock die holder has never produced a non concentric thread in years of use and there is a reason for that but I will keep that reason to myself.


Best regards and keep safe,

TerryD

 

[terryd]

Anyone have a feel for how concentric the rod and die need to be? I'm wondering if I can just toss everything into a 3-jaw and trust it, or if I need to do everything with a carefully dialed-in 4-jaw.

Hi Tim,

Depending on how you make your tailstock die holder the die should be self centering on the work in a 3 jaw chuck (hint don't make the die holder too precise a fit on it's slider - allows for self centering). There is no need for a super precise 4 jaw set up. That's just faffing about for the sake of it. Some folk like to spend large amounts of time on super precision even when it's not needed and that's ok if it's your bag. Me, I just like making stuff that does a job and does it well. I don't have enough years left to waste them on uneccessaries

 

[BaronJ]

Hi Terry,

Where about in the world are you ?