Where to find detailed fastener head, recess & drive geometry? (Beyond ASME)

[AXNRXN]

Hi All,

I have a project where I am designing a new fastener head. It's something similar to a Philips head or Pozidrive type head. I've looked at the ASME standard for fastener heads, but they only give a few dimensions on the head and drive recess geometry. For instance, I've found additional info on a few of the drive angles and point angles on a standard #2 Philips driver that are not listed in the ASME standard by just googling around.

Anyone have a source for that type of info? I'm trying to model up head recesses and drivers in CAD and the little details matter. Maybe there is an additional ASME standard I'm not seeing?

Thanks for any help!

 

[Lou Scannon]

Check this out.
You'll probably get booted up a level or two and prompted to register, before you can get access to this drawing.

"Schiefgehen wird, was schiefgehen kann" - das Murphygesetz

 

[3DDave]

Phillips, et al, are licensed designs. That's how companies that design recesses and driver bits make their income.

It may be that you just have to measure a bunch of screw recesses to get a decent idea of the tolerances required, and use those for your design. I don't know they can come after you for that. What they will certainly sue for is if a patented recess design name is used to describe your product.

As it is there are a ton of unlicensed knock-offs and a lot of the patents (Torx?) have expired. But don't expect a lot of help to undercut the people who thought it up to begin with from the people who thought it up.

Bonus: Look up the histories of screw recesses and how much work it is to get a style into enough parts to make selling drivers for, drivers that have to exist in order to use the screws. Priming the chicken-vs-egg screw head recess pump is not for the weak.

 

[tbuelna]

Here are a couple mil specs for offset cruciform (Torq-Set) type recesses and drive bits. These are commonly used for aerospace flush head bolts/screws instead of the standard phillips type recess.

http://everyspec.com/MS-Specs/MS1/MS14000-MS14999/download.php?spec=MS14191E.023739.PDF

http://everyspec.com/MS-Specs/MS3/MS33000-MS33999/download.php?spec=MS33781B.008938.PDF

Might also take a look at the head standards in the Phillips Screw Company technical resource library.

 

[Screwman1]

Having been involved in the development of Torx Plus I will tell you to expect to invest a lot of time, testing and money into this project. Remember that whatever you come up with has to be able to transmit torque, be headable at a low cost and provide a sound head / shank ratio and provide excellent tool life. Also remember to develop the gages for header tooling, screws and driver bits. Oh and you'll need master gages to use to check all those other gages. Don't forget your drive tool life testing either. We invested 20,000 man hours into Torx Plus before all the sizes were done.

 

[AXNRXN]

@Screwman

So, as an engineer involved in cold-heading, did you come across any industry resources on it? Any recommendations? I'm working on the front-end for a manufacturer that already makes hardware of different varieties. So, when it gets into production, they will be taking over the production details and costs. However, I want the designs I put forward to be based on accurate representations of what is already out there. So, things like head / shank ratio, draft on the recess walls, min recess width and such should be pretty close to what we'd see on a final design.

 

[drawoh]

...

Bonus: Look up the histories of screw recesses and how much work it is to get a style into enough parts to make selling drivers for, drivers that have to exist in order to use the screws. Priming the chicken-vs-egg screw head recess pump is not for the weak.

Look up Robertson Screws. These were and are a huge success here in Canada. The inventor would not sign a licensing deal with Ford Motor Company, so they did not spread to the USA.

--
JHG

 

[Screwman1]

3D Dave has it right. The actual details of the recess dimensions as considered to be pretty valuable intellectual property by the licensees and trying to get the true geometry is dependent on purchasing a license from them. The best thing that I can suggest is to make several casts of the recesses that you are interested in the then analyze the heck out of them. That should get you pretty close so you can create a general model for CAD purposes- obviously it won't be good enough to make parts from, but if that is the end goal, then they can purchase heading punches from one of the licensed tooling companies like Wrenthan or Reed. Rico.
There is a lot that goes into designing a special head configuration for a given application and it really is too much to try to cover in a forum.

 

[3DDave]

tbeulna,

My favorite of the series was the Tri-wing. Apparently Torq-set is close enough to Phillips and whatever the other one is, that mechanics would grind the daylights out of those and chew up the Torq-sets. No such monkey business with Tri-wing.

Pretty good collection for anyone interested in the variety:

https://en.wikipedia.org/wiki/List_of_screw_drives

 

[tbuelna]

3DDave,

I don't think there has ever been a recess type of fastener drive developed that proved fully satisfactory for the aerospace industry. Here's a 118 page report of a 1978 study conducted by the USAF regarding problems with various types of recess drives in use at that time (including the infamous Tri-Wing), many of which are still in use today. Here's the first paragraph:

"Over the years, many complaints have been received by Aeronautical Systems Division (ASD) on the service failure of fastener internal wrenching systems (or recesses as they will be referred to in this report). A synopsis of the problem showed that the Hi-Torque recess was singled out as receiving the majority of the complaints; the reported failures concentrated on the smaller size fasteners (3/16 - 5/16 in.) installed in frequently removed panels. The failures usually occurred when removal of the screws was attempted with a speed wrench."

http://www.dtic.mil/dtic/tr/fulltext/u2/a059171.pdf

 

[3DDave]

tbuelna,

That's one of the many reasons we can't have nice things.

I'll add that to my collection.

 

[DerbyLoco]

Try BS EN ISO 4757 - That looks like it has the details you need but they are defined as types H and Z

 

[btrueblood]

I like Robertson drives. I replanked my old cedar deck using Robertson drive deck screws...biggest problem was my corded drill getting too hot to hold onto.

 

[Lou Scannon]

btrue, I refurbished my front deck last fall, by pulling up the old boards, installed with uncoated steel Phillips screws, by then rusted to a skeleton. You can imagine what a chore it was getting the remnants of the screws out of the boards and the joists, while preserving the boards as intact as possible!
My first preference for the replacement screws was obviously Robertson, but alas, they were not available at my hardware store in the size and outdoor-grade coating needed for my project, so I resorted to Torx.
By the way, here is an interesting look at the history of Phillips, Robertson, and the ensuing variants.

"Schiefgehen wird, was schiefgehen kann" - das Murphygesetz