Rolled Threads

[steamer]

An interesting topic.     What about rolled theads?

Specifically, I'm talking about tooling for "formed" threads vs "cut" threads.

I'd like to understand the benefits of using "form taps" in the hobby vs using cut taps?

What are the benefits and procedures?    And where do we use this in our engines?

GO!

Dave

[Dan Rowe]

Dave, I switched to roll form taps several years ago for small work (smaller than 3mm). I cast silicon bronze and it is hard on cutting taps but I have not had issues with roll form taps.

I also use roll form dies to make bolts or tie rods or studs from wire. The ones I am getting are not expensive and if the wire breaks the die can be taken apart and reassembled in a few minutes with no damage to the dies.

https://www.ebay.com/itm/203043256517?hash=item2f465238c5:g:r2MAAOSwVOlfBizJ
This is my favorite size and what I use for the 00-90 bolt size

Cheers Dan

Edit: ebay links go dead so search for "thread rolling head spoke"

[crueby]

Hi Dan,
Took a look at that ebay link, some interesting information there. At one point it mentions that the resistance is 25-30 times higher than with a cutting die - that means it takes more force to turn the die onto the rod?
Are the dies set up with a tapered lead in at the very end to start the rod, or does it require multiple passes with closing down the spacing?
Would be great if you could give some narrative on how they are used.
Thanks!!
Chris

[Dan Rowe]

Hi Chris, yes I made holders to use the dies in the lathe. These all have 1/2" shanks and my latest method is to use a drill chuck in the headstock for the wire and use a bar with a 1/2" hole in the tailstock to align the holder. When you have enough threads or the die gets close to the drill chuck just let go of the die.

I only leave a small amount of wire sticking out of the drill chuck so I can push towards it with a bit of force for the first few threads. Leave a gap for the die holder shank when you lock the tailstock, so the lathe can be reversed to remove the die. It goes very quick with a single pass. The wire only needs a bevel in the end which is normal prep for threading.

I can set this up quickly if anyone wants a photo.

Cheers Dan

[Dan Rowe]

Here is my post when I first tried a roll form die:
https://www.modelenginemaker.com/index.php/topic,3456.msg61461.html#msg61461

Cheers Dan

[Lew Hartswick]

Dan, How would they work for threads as large as #10-24 or 1/4 - 20 ??
   ...lew...

[Dan Rowe]

Lew, the form taps are only good for ductile metal so super steel alloys and cast iron are out. I did use a 0-80 form tap to tap a hole in the stainless steel/bronze composite material printed by Shapeways. It was not happy but it worked. I am sure it would shorten the tap life by a whole bunch.

I have used form taps up to 1/4-20 and get good results in steel and bronze and other soft metals.
I use Moly-Dee taping fluid which is more like paste than fluid. It sticks to the tap so you get the lube right where it is needed.

The thread rollers start to get expensive as the size goes up so I do not have anything larger than 2.5mm.

Cheers Dan

[Dan Rowe]

The ebay info chart only goes down to M1.6 and there is a M1.4, M1.2 and M1 size all of which I have. The thread standard that comes with the roller head is not fully threaded so you can measure it if you do not get stupid and roll the rest of the standard like I did on one size. 

Here is a very detailed instruction set for Habegger (Swiss) thread rollers:
http://www.habegger-sa.com/INSTRUCT/Filieres%20a%20rouler/Instruct/3_IS_FR_E.pdf

Cheers Dan

[Admiral_dk]

Dan's first link works fine and they are based in St. Petersburg, Russia - I also believe that this explains the text (translation).

I do not think, that the 20-30 times are the force required to use this tool, but the strength of the tool compare the the die making the same thread .... or surface hardness ....

Per

[derekwarner]

So not being a Mug, I believe the Parker Hannifen reference is valid reading for the new [thread topic] of threads.............. Derek
-----------------


A bit long winded    , but Parker Hannifen have been producing their 3H series of hydraulic cylinders in the US for 50 years plus, which alll include tie-rods with rolled threads

So the bar stock is undersized, then the threads rolled up to size, and as Kim says ....'the metal is moved around'

So this eliminates the sharp thread cut V in the root or valley of the thread, replacing it with a rolled V profile with a rounded root profile and mirror polished thread faces

All a bit subjective, the thread rolling does produce that mirror thread surface, so by increasing skin hardness on the thread face which can reduce galling, however the rolling process does not alter the mechanical properties of the heat-treated bar stock

There are no Wifes Tales here     , however have not seen any low production of rolled threads  as commercially available

https://www.parker.com/literature/Industrial%20Cylinder/cylinder/cat/english/HY08-1114-6_NA_2H-3H%20.pdf

Derek

[kvom]

A good while back I acquired a batch of 1/4-20 form taps and mailed out 5 or 6 to people on the other forum.  They were easy to use as I recall.

On Practical Machinist website, form taps are recommended for CNC rigid tapping, so I assume that applies to tapping heads as well.

[Dan Rowe]

I was one of the guys who bought a form tap from you, but it is a 1/2” x 28 NS tap which I have not found a use for yet, but it did get me to look into form taps and as they are much stronger than cutting taps they are just what I needed for small work with silicon bronze castings.

The photo is a 3/8” brass bolt I found in the bin on a ship many years ago. I had no idea why it had a smaller section until I found it in my junk drawer a while back. It is a blank that did not get roll formed. A lot of bolts are made this way not just tie rods for cylinders or motors.

Cheers Dan

[dieselpilot]

Virtually all fasteners are rolled.

[Kim]

To keep the info all in one place, I'll add my comment on this thread too:  (sorry for being redundant)

I've found the forming taps work well for softer metals, including 12L14 steel.  I've worried about them in 1018 and have tried to use cutting taps there, especially for small taps.  Never tried it in stainless - seems scary.

The other thing I've found with forming taps is that they leave a small ridge around the tapped hole, which makes sense because the metal being pushed out of the way for the thread has to go somewhere.  So if you want the surface to be flush, you have to file the ridge off or ream a pretty good chamfer around the hole. Not a big deal, but something to know.

Kim

[Dan Rowe]

It should be noted that a form tap uses a larger drill than a cutting tap. You need to use a form tap drill chart. I use an iPhone app called Thread King to look this up and I have several others but some of them stop at M1.6 and 0-80. Thread King goes down to M1 and 0000-160.

Here is a calculator for metric and inch tap drills for cutting taps and form taps:
https://osgtool.com/tap-drill-size-calculator

Cheers Dan

[steamer]

Awesome information!   Thanks for posting this guys!

Dave

[john mills]

I had a job a few years ago were they made parts for large processing compressors  .i saw piston rods for reciprocating compressors  they were made in hardnable stainless materials  i can remember about 40 or 50mm dia stew threads  rolled   they were jobs of ones and twos  low numbers. the rollers i saw were 100 150 dia 150mm or so long .  rods could be a meter or so long.i did see much larger and longer rods made.
 John

[Dan Rowe]

Dave,
 here is a good link about roll form taps.
https://www.yamawa.eu/wp-content/uploads/2017/10/Roll_taps_2017_web.pdf

Cheers Dan

[steamer]

Thank you John and Dan!

Its interesting that the drilled tap hole must be tighter tolerance than a cut thread....  Lots to read!



Dave