Buttress threads

[frank46]

Need a little help here. In looking at the construction of large bore artillery pieces and naval guns the buttress thread has been for the most part been used on the breechblock that swings either sideways or up from the bottom of the breech to close with and mate with the same type thread on the locking surfaces inside the breech. How were these threads machined?. Did they use some sort of thread mill, single point them?. Remember once the gun is loaded those threads on both the breech block and breech of the cannon had to endure the rearward thrust of both the explosive charge and the weight of the shell. I've looked at any number of period videos showing cannons being rifled but none show how they are made. So any help would be appreciated. Thanks, Frank

 

[gwilson]

I'd just make the thread tool shaped like the buttress thread and feed it straight in to cut the thread. I don't see any other way to make that thread. Maybe I'm wrong. One of these days I'd like to make a working model modern artillery piece.

 

[Gordon B. Clarke]

Frank, just for info but there are several types of buttress threads and with varying flank angles. I don't know if the same type is always used for weapons but it might be a good idea to check the flank angles in advance.

https://www.google.dk/search?q=butt...Nswa1iIAg&sqi=2&ved=0CC4QsAQ&biw=1311&bih=646

Buttress thread - Wikipedia, the free encyclopedia

Gordon

 

[Ray Behner]

Gordon,
I know the are a pile of variants of buttress threads, but isn't a more common one at 45º x -7º? Don't really know, but asking.

 

[neanderthal mach]

I don't have a link, and no doubt there were more than a few methods used over the years. But the breech block threads were obviously the toughest to do. It's my understanding that some rather specialized lathes with very quick acting retraction cams geared to the head stock for the cross slide movements were used for at least some of it. I read somewhere quite awhile ago that it was fairly high maintenance equipment due to the needed movements hammering on the lathe quite a bit. Wish I had more info.

Pete

 

[jhruska]

Buttress threads I made were single point. Made a gage of the thread. Ground the tool to the gage. Checked the finished thread with the gage.

 

[Gordon B. Clarke]

Gordon,
I know the are a pile of variants of buttress threads, but isn't a more common one at 45º x -7º? Don't really know, but asking.

It is the type I see most often but I don't know which is the most used buttress thread if we are talking worldwide. As far as I know they are probably the strongest thread when moving force in one direction i.e. in the direction of the smaller flank angle.

As you can see I ommited giving flank angles for a buttress thread in this link I made. I do give though the most common usages.

http://www.f-m-s.dk/1.02.pdf

Gordon

 

[moonlight machine]

I Had a close look at the threads on the breech block of an about 5" or 6" gun on the Olympia, in Philadelphia. This ship was used in the Spanish American war so the guns, if original were made around 1894. It was a buttress thread with open spaces, about every 90* or so so the breech block can swing closed and then turn about 1/4 turn to lock. Done decades before anyone ever thought of cnc. Threads done on a lathe, open spaces with a shaper I suspect.

 

[Limy Sami]

I think (????) a PMer has experience of breech threads - maybe Forrest Addy or John Oder?

 

[SouthBendModel34]

Welin Breech Block

The artillery breech blocks with the steeped, interrupted thread are Welin breech blocks. A search of PM will reveal prior discussions, some of which have the name misspelled with two L's.

The broadside guns currently on the USS Olympia are much newer than the ship herself. They are 5"-51 guns, meaning 5" caliber bore and 51 bore diameters long. In other words, the barrels are 255" in length. These guns are the same as the broadside guns currently on the USS Texas. The same sort of gun was on the USS Arizona, removed after the ship sank. These guns can only engage surface targets. They use separate loading - a projectile is rammed followed by bagged smokeless power.

The USS Olympia has such guns because her last naval use was as a gunnery training ship at a time when much of the USN battle fleet had 5"-51 guns as their secondary armament. (This was BEFORE the fast battleships of the 1930's & '40's)

The interrupted threads of a Welin breech block are indeed cut on a lathe with a "relieving attachment" - the cam-operated very-quick-withdrawing mechanism mentioned in Pete's post. Hendey, for one, offered this option on their lathes and there is info about it posted on PM. Variations of this attachment can cut a spiral milling machine cutter with "relief", said option being known as the "spiral relieving attachment"

Searching for "Welin Breech Block" and "Relieving Attachment" should turn up some interesting information.

The use of these Welin Breech Blocks is not confined to naval guns.

John Ruth

 

[frank46]

Gordon, the Danish spelling threw me off then checked your location. Some of the artillery and naval rifles had unusual thread arrangements. The most common I have seen were the ones with either 3-4 sections of threads followed by open spaces every other section of threads. And thanks all of you who took the time for responding to my post. Looks like I have some research to do. Frank

 

[Nick Mueller]

As you can see I ommited giving flank angles for a buttress thread in this link I made. I do give though the most common usages.

So this is once more just SPAM: There is not more info to be found re buttress threads. That would have been the only rationale for a link to your business.
The first two links you gave in posting #3 were informative (for someone who doesn't know Google or wikipedia).

Even worse, your PDF contains two severe errors.


Nick

 

[Gordon B. Clarke]

So this is once more just SPAM: There is not more info to be found re buttress threads. That would have been the only rationale for a link to your business.
The first two links you gave in posting #3 were informative (for someone who doesn't know Google or wikipedia).

Even worse, your PDF contains two severe errors.

Nick

I'd kinda hoped you'd gone into hibernation but no such luck

Mr. Mueller how about just once give something that can be useful instead of infantile comments such as, "Even worse, your PDF contains two severe errors."

Tell me what my "severe" errors are and I can correct them and you'd be helpful for a change.

I still remember when you first appeared on the scene (over 1½ years ago) with a broadside on this link.

English index

It isn't mine but I certainly wish I knew how to do something like that. It must have taken days if not weeks and yet your contribution was to ridicule.

The guy that made it is Danish and isn't mechanically minded which I also stated when I posted it. You trashed both him and the link because to you it wasn't perfect. Instead of helping him out by letting him know what you believed to be wrong you wrote that people who didn't know exacly what they were writing about shouldn't be allowed to write. I defended the guy that made the link and this apparently infuriated you. If I recall correctly too most of your posts were deleted and you yourself "vanished" for about a year.

Mr. Mueller, rather than tell people that you think they are imbeciles it'd be better if you tried to help instead. You must lead a very sad life if your purpose in life is to belittle and insult people. Petty is probably the best word I can find to describe you.

 

[Nick Mueller]

Mr. Mueller how about just once give something that can be useful instead of infantile comments such as, "Even worse, your PDF contains two severe errors."

Mr. Gordon you are the expert in thread metrology. And as such, you should notice the nonsense. If not, you have a great chance to dive deeper into threads, learn something, correct your PDF and post an other link to your site.
Do your own homework, stop SPAMing and stop trying to increase your Google page rank via practical machinist.

The guy that made it is Danish and isn't mechanically minded which I also stated when I posted it.

So you both have one thing in common: You talk about things you don't understand.

You must lead a very sad life if your purpose in life is to belittle and insult people.

Whom did I insult? Did I write "infantile" or was that you?

If I recall correctly too most of your posts were deleted and you yourself "vanished" for about a year.

You have a long revenue of deleted posts and locked threads. You also should not speculate why I wasn't posting at PM for some time. You did that too, and I'm not speculation for the reasons. You shouldn't throw stones in a glass-house.


Nick

 

[Zonko]

Well i do see a few oopsies in that .pdf. Such as Buttress threads: pitch in TPI. Obviously said person was not too familiar with the INfamous S 20x2 on all sorts of old deckel style mills.....Okaaay...the metric world calls it a sawtooth thread......still not much of a difference.....

And i dont think GB is using UNC threads. They had BSW and its special pitch derivatives, BA and now are officially metric.

Either I skipped the bad mistakes because i never deal with the thread forms in question or you are one hell of a grumpy Bavarian Nick.....


Dang, those Bavarians....

Edit: What i should have written: I dont think GB uses any UNIFIED NATIONAL threads...unless they manage to sneak their way in via some bloody OEM item

 

[Gordon B. Clarke]

Well i do see a few oopsies in that .pdf. Such as Buttress threads: pitch in TPI. Obviously said person was not too familiar with the INfamous S 20x2 on all sorts of old deckel style mills.....Okaaay...the metric world calls it a sawtooth thread......still not much of a difference.....

And i dont think GB is using UNC threads. They had BSW and its special pitch derivatives, BA and now are officially metric.

Either I skipped the bad mistakes because i never deal with the thread forms in question or you are one hell of a grumpy Bavarian Nick.....


Dang, those Bavarians....

Edit: What i should have written: I dont think GB uses any UNIFIED NATIONAL threads...unless they manage to sneak their way in via some bloody OEM item

Zonko I'll reply to your post and leave Nick to his own personal pissing contest

I once posted a link in here (PM) that I'd found on the internet and thought so good that I put it on my website. It was a DIN standard but I can't remember the number but very similar to what FETTE has in their thread information pages in their brochure.

Of course Nick stuck his nose in and threatened to contact the German authorities if I didn't remove it. As I hadn't in fact realized it was copyrighted I did in fact remove it. As I still did like the overview of various threads I chose to make one myself from the multitude of thread information give on the FETTE brochure. Things like Use, Origin and whether TPI or metric was common was taken from what was written.

Nick does seem to be an unusually grumpy Bavarian but why he doesn't offer help rather than negative criticism and snide remarks I don't know. Maybe someone once peed in his beer at a Bavarian beer festival?

If anyone can tell me what mistakes there are in http://www.f-m-s.dk/1.02.pdf I'll correct them. I won't hold my breath waiting for something from Nick I can use

Here's another link and much more detailed. I've also put it on my website and would have posted that instead except for the fact that some might think that the two buttress type threads mentioned were the only ones.
International Thread Standards

Gordon

For those that want to know more about Bavarians (south west Germany)
http://blogs.news.com.au/news/splat/index.php/news/comments/what_the_germans_say_about_bavarians/

 

[Gordon B. Clarke]

And i dont think GB is using UNC threads. They had BSW and its special pitch derivatives, BA and now are officially metric.

Edit: What i should have written: I dont think GB uses any UNIFIED NATIONAL threads...unless they manage to sneak their way in via some bloody OEM item

Maybe someone from GB can tell us how common UN threads are in GB?


I have a copy of British Standard 84 : 1956
Title: Parallel Screw Threads Of Whitworth Form.

On the back of the front page is written:

Ammendment No. 1, published 11 August, 1966

At a fully representative conference held on 23rd november, 1965 consideration was given to the action to be taken in relation to the move to metric as far as British Standards for screw threads were concerned and it was decided that:
British industry should be strongly recommended to to adopt the internationally agreed ISO metric threads or ISO inch threads but that ISO inch threads should be considered second choice. The implementation of this recommendation means that B.A:, BSF and BSW threads should become obsolete and should not be used in new designs.

ACCORDINGLY IT HAS BEEN AGREED THAT B.S. 84 BE RENDERED OBOLETE: IT WILL BE MADE OBSOLETE IN DUE COURSE.


I admit to not knowing if GB has arrived at "....... IN DUE COURSE".
Pipe threads with the Whitworth 55º flank form still are the widest used in the world to the best of knowledge. The old demonination for them was BSP and BSPT but have now been given an ISO denomination.

Oh, oh, more "spamming" coming up. BE WARNED

http://www.f-m-s.dk/3.05.pdf

For Whitworth type tapered threads there are 3 denominations:
R for external tapered thread
Rc for internal tapered threads
Rp for internal parallel threads (not to be confused with G type pipe threads which aren't intended to be leak proof on the thread itself).
G type pipe threads (in the link above) are usually sealed using an O-ring or gasket.

Gordon

 

[WizardOfBoz]

So this is once more just SPAM: There is not more info to be found re buttress threads. That would have been the only rationale for a link to your business.

C'mon, Nick. Do you really think that Gordon is looking to make a lot of money off the lucrative cannon breech block buttress thread gaging market? Are we expecting a resurgence of large-caliber weaponry manufacturing? Or is it more likely that he's trying to be helpful and join in the conversation? You've posted a few times with critical response to Gordon's posts. If Gordo's missives really drive you that crazy, you can adjust your settings so that you don't see his posts, I think. Or, skip over them. But incessantly criticizing someone for anything they post, and trying to silence their voice, is not in the best traditions of this forum. If Gordo bugs you I strongly suggest that YOU DON'T READ HIS POSTS.

The first two links you gave in posting #3 were informative (for someone who doesn't know Google or wikipedia).

Or, to save someone without Gordon's knowledge from having to sift the wheat from the chaff.

Even worse, your PDF contains two severe errors.
Nick

Even worse, you didn't identify the errors!

 

[James H Clark]

Frank46 : I have cut buttress threads a number of times. They can be cut in a lathe quite easily. There is a bunch of variations of configurations involving angles on the face of the thread . Usually anywhere from zero to seven degrees. also keep in mind that there are "push" and there are "pull " types. This means that the face of the thread does just that. there are also right and left hand threads and also male and female versions. Most of the couplings I made were 4" and 5" stainless . I may have made a few 6", not sure, this was a number of years ago. Engineers were doing a lot of experimenting . Just remember that the load on the thread is on the face, not the long flank. JH

 

[Gordon B. Clarke]

Frank46 : I have cut buttress threads a number of times. They can be cut in a lathe quite easily. There is a bunch of variations of configurations involving angles on the face of the thread . Usually anywhere from zero to seven degrees. also keep in mind that there are "push" and there are "pull " types. This means that the face of the thread does just that. there are also right and left hand threads and also male and female versions. Most of the couplings I made were 4" and 5" stainless . I may have made a few 6", not sure, this was a number of years ago. Engineers were doing a lot of experimenting . Just remember that the load on the thread is on the face, not the long flank. JH

James I did stress that in post #7 but thanks for mentioning it again.

As far as I know they are probably the strongest thread when moving force in one direction i.e. in the direction of the smaller flank angle.

I don't think I've ever heard of a buttress thread where the force isn't applied to the smaller flank angle. This means a LH thread can be spotted immediately unless of course it is used to pull as you mention.

In German buttress threads are called "saw tooth threads" and it's easy to see why when looking at a buttress profile. That's an easy lesson for anyone to remember when putting a blade on a hacksaw

Gordon

Now that I've been nominated "Google search expert" here's a couple more.

http://en.wikipedia.org/wiki/Buttress_thread
and it's even for a breech-lock.

http://www.scribd.com/doc/54060920/ANSI-B1-9-1973-Buttress-Thread-Spec
There seems to be quite a bit with just a little searching.

Happy hunting