Author Topic: Thread rolling device  (Read 13078 times)

Offline ksor

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Thread rolling device
« on: October 20, 2009, 02:14:47 AM »
I got some thread rolls M14-M16, M18-M22, M24-M27 like this:



I the first place I need some articles describing how it works "when you roll a thread" - any links ?

Then I would like to make some kind of "device" for the tail stock to ROLL the thread on instead of cutting with a die - maybe you got any links to plans ?
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KSor, Denmark
Skype name: keldsor

Offline Darren

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Re: Thread rolling device
« Reply #1 on: October 20, 2009, 02:43:37 AM »
I have no idea how a thread is rolled, but imagine a very big machine is used  :scratch:
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Offline sbwhart

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Re: Thread rolling device
« Reply #2 on: October 20, 2009, 02:54:29 AM »
Hi Ksor

We had some thread rollers (Alfred Herbert) where I working didn't roll threads with them though used them to roll another type of feature in one of our products, because of the loads involved they were strong robust machines and the processes was done under oil.

The diameter of the thread blank is made to the thread efective diameter, you squeze in and push out metal at the same time, rolled threads because of the material grain flow are stronger than a machined thread.

This is a pic of a thread rolling box as used on a capstan lathe I guess you want something similar to this.



Hope this helps

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bogstandard

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Re: Thread rolling device
« Reply #3 on: October 20, 2009, 04:30:40 AM »
Quote
I have no idea how a thread is rolled, but imagine a very big machine is used

Not really true Darren.

I bought some old castings off a car boot for a squid.

They turned out to be thread rollers for putting the thread on the end of bicycle spokes.

I tried offering them FOC to a museum, but they refuse to take them because they said they had enough examples, so one day they will be turned into something else.


John

Offline Darren

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Re: Thread rolling device
« Reply #4 on: October 20, 2009, 04:34:49 AM »
My, aren't they interesting little chaps ... be a shame to destroy them but thanks for showing as that was an eye opener  :smart:
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Offline ksor

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Re: Thread rolling device
« Reply #5 on: October 20, 2009, 05:19:32 AM »
-->bogstandard:

It was exactly a "divice" like that I had in mind - thanks !

But when I want to use it on the lathe ... I need to have the "spoke" in the chuck and then the tail stock with the "thread rolling device" had to be able to move towards the chuck as the thread is rolled on

OR do I misunderstand something ?

How is the "spoke" released when finished - I think there have to be some "click here to release" to remove the rollers from the spoke.
Best regards
KSor, Denmark
Skype name: keldsor

bogstandard

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Re: Thread rolling device
« Reply #6 on: October 20, 2009, 06:12:54 AM »
Ksor,

You have to remember that the ones I have shown most probably came from the early part of the 20th century and made down to a price.

When you have finished rolling, you wind it back off again.

But as you can see from the pics, it does have a crude tightening device that works by a tapered thread having a threaded hand feed nut on it, so I suppose it could cater for varying sizes of spokes and also put pressure on over several runs to form the thread, the same sort of thing you do with a die.

I don't know whether it is intentional, but the rollers are loose on their angled spindles, in all directions, but the spindles don't look to be worn. Maybe it is to allow the rollers to settle into their own rolling pattern.

I would have tried them out, but I don't have any soft iron spokes, only the modern day stainless ones, which I think would be too hard a material to try to roll threads onto. Threads on modern day spokes are cut I think, not rolled.

You can gain a lot of information by just looking at pictures such as these. With a little speculation you can imagine what was going through the designers mind when he was faced with the problem in the first place.

It is your turn now.

Bogs

Offline John Hill

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Re: Thread rolling device
« Reply #7 on: October 20, 2009, 11:14:04 PM »
I imagine those rollers go in something not unlike a knurler as the process is pretty much the same.  Of course the device would have to move in accordance with the pitch of the thread being rolled.
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Offline ksor

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Re: Thread rolling device
« Reply #8 on: October 21, 2009, 12:42:31 AM »
-->John Hill:
Yeah - just like knurling with a little more power - the movement because of the pitch of the thread can be managed just by loosening the tail stock so it can be dragged towards the chuck - just like CUTTING a thread with a die.

The hard one is to design the "click to release" - something like a ring around the rollers and when the ring is turned the rollers is moved away from the "spoke" and the tail stock can be removed

- but I have to think the design over a copple of times.
Best regards
KSor, Denmark
Skype name: keldsor

Offline John Hill

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Re: Thread rolling device
« Reply #9 on: October 21, 2009, 03:23:21 AM »
Ksor,  I think the company that makes a lot of these is Fette in Germany.

I do not know why the device would not be on the carriage then it could be moved in sympathy with the thread pitch being rolled.
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Offline madjackghengis

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Re: Thread rolling device
« Reply #10 on: April 03, 2010, 12:27:11 PM »
Hi, I used to use thread rollers to thread spokes, both for bicycles, when I was young, and later, with six and eight gauge spokes for motorcycles.  As far as I know, all spokes are still roll threaded, as that is a substantially stronger thread, and it allows for an effective heavier gauge in the thread, while the spoke shaft remains light.  The thread rolling machines I used were hand cranked, with a set screw to tighten up one of the rollers, and they cranked right off, turning backwards.  I expect you would have no problem rolling those stainless spokes, and using the rolls you have on your lathe would entail making a holder with three angled axles, at least one set up for tightening, and I'd run the lathe at slow speed while pressing the tailstock by hand, up against the job in the chuck, once the rolls start, they will pull the tailstock if it's loose.  Definitely use lots of cutting oil, like knurling.  The stock should be approximately the final pitch diameter, but I think there is a section in Machinery's Handbook that gives a formula for figuring out the proper diameter.  Thread rolling is generally done on a screw machine, automatically, so tail stock mounting is generally the rule, as it allows fast retraction for the next screw.  For what it's worth, Mad Jack

Offline ClydeBuilt

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Re: Thread rolling device
« Reply #11 on: May 19, 2010, 04:22:10 PM »
Didnt know such a thing existed! I'll have to keep an eye out for that sort of thing.

Ideal for push rods etc in the rc model hobby, I tend to use pretty beefy ball/socket connections to save slop, a gadget like that would save a shedload of time looking out and setting up the die etc....lucky man!

Offline Jasonb

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Re: Thread rolling device
« Reply #12 on: May 20, 2010, 03:08:50 AM »
I think it is going to have to be a hefty fixture if you intend to use the M27 size, its hard enough using a ratched die stock to cut threads at that sort of size let alone squeezing the metal into place. A google for images of thread rolling machines will give a good idea of whats needed.

I don't see the need to release the rollers you could just reverse the lateh and back the work out unless you are intending to do a lot of long threads

Do the rolls have any form of lead on them to start the thread off as there are also hydralic ones which are pushed into the work and would probably not require any leadin.

Jason

Offline madjackghengis

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Re: Thread rolling device
« Reply #13 on: May 24, 2010, 11:45:56 AM »
Hi Jason, I know when thread rolling is used on a turret lathe, the third roller is the means for setting the final o.d., and the means for releasing the roller assembly from the finished thread, so it can be retracted straight back.  I did some work on a machine in a shop that made their own special screws for the machines they made, and I watched their turret lathe turn them out about one every fifteen or twenty seconds.  I think the lathe used hydraulics to lock the rolling assembly as it moved up to the blank, and released it as soon as the thread was complete so the turret could instantly retract.  You might have to use back gear to get the torque to turn the blank, but you can probably use them in a home lathe, that third wheel definitely needs a means of adjusting for thread depth and o.d.   :headbang: mad jack

Offline Lew_Merrick_PE

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Re: Thread rolling device
« Reply #14 on: July 11, 2010, 04:28:42 PM »
The stock should be approximately the final pitch diameter, but I think there is a section in Machinery's Handbook that gives a formula for figuring out the proper diameter.

Mad Jack is generally (mostly sort-of kind-of) correct.  You are moving material from the "low side" of the thread to the "high side" of the thread.  As you squish material, it will reduce the total volume by a factor of 1 - 2*Poisson's Ratio for the material.  Rubber has a Poisson's Ratio of .50 -- which means that it stays the same volume no matter how you squish (or stretch) it.  Most steels have a Poisson's Ratio in the .270-.290 (.3 is the value taught in engineering classes) range.  Thus, if I have a block of steel that is a 1 unit cube and I squish it to .5 unit tall, I will end up with .5(1-2*.28) = .22 (i.e. 22%) less volume than I started out with.

Accounting for this in rolled threads is non-trivial.  It will depend on the exact metal and alloy with which you are working.  It is even somewhat dependent on the lubrication you are using.  As I recall (and this is from nearly 40 years ago which was the last time I rolled threads seriously), 4130 steel used a 7.5% increase over the pitch diameter for Unified National screw threads.

Offline Ned Ludd

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Re: Thread rolling device
« Reply #15 on: July 16, 2010, 06:16:46 PM »
Hi Guys,
Thread rolling may be used in industry to create threads but they are also used in the garage end of the business to restore slightly knackered threads. Many years ago we had some hand held thread restoring rollers in common motorcycle thread pitches. They were much kinder to parts, that were stripped or burred, by swageing a thread rather than cutting some metal away as you would with a die.
Ned
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Offline John Swift

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Re: Thread rolling device
« Reply #16 on: July 30, 2010, 08:16:33 AM »
Hi
a long time ago I watched a Danobat 50 automatic  capstan machine roll a 25mm thread at an amazing speed
the rollers retracted at the end of the thread as the spindle didn't stop

I've found a picture of the type of roller head

it may give you ideas