Captive screws with availability in the US (CE Machinery Directive)

[geesamand]

I need to update all of our major product lines to meet CE safety requirements. I'm focused on getting all of the fixed guards fastened with captive fasteners, per the directive.

Lacking big production quantity, I need to either modify a commercial screw to retain a captive washer or buy a system off the shelf. There seem to be lots of options in really small sizes but even M8 seems to be uncommon. I've seen a couple of systems that look good but are sold only from Germany (SaveTix) and I'm nervous about availability both short and long term.

Application:
Currently we fasten stainless sheetmetal guards to cover an opening in a steel or iron housing. The guards have holes pre-drilled, and then at assembly we match drill into the housing and hand-tap threads. Then a stainless 1/4" or M8 bolt and washer are used to fasten the guard. We're happy with the match drill and tap and want to switch to bolts that stay captive in the guard. Smaller bolts are not desirable for durability and because I need to stay with wrench sizes the maintenance guys will have handy.

I'd love to hear from others because I'm sure we're not the only people in the US building/selling machinery according to CE.

David

 

[micalbrch]

What are the threads are you looking for, metric? How many captive screws do you need per machine (average)?
Have you checked this company?

http://www.accuratescrew.com/Captive-Screw-Assemblies.aspx

 

[hendersdc]

These guys offer a couple options in 1/4-20 but evrything I saw was screws, not bolts. They say they can do custom fasteners too so probably worth talking to them Matdan Fasteners

Doug

 

[geesamand]

The average is about 4 screws per machine. Commercial availability is my main concern as I need to keep two manufacturing sites fed and if there is any slip-up with minimum quantities / reorder logic, we could do serious damage to our production.

Note that these are not the same thing as "sems" because the washer gets assembled after the screw is passed into the guard.

I have reviewed the accurate screw offerings and it appears they have captive socket head cap screws in M8x1.25 thread.

http://www.accuratescrew.com/CatalogPage.aspx?ProdCat=183x

Savetix of Germany is another:

http://www.savetix.de/uk

 

[micalbrch]

The reason why I was asking about the average screw quantity per machine is that with such small quantity you can perhaps use standard studs and wing nuts. Drill a hole to one of the nut's wings and fix a small chain to it and the other end of the chain somewhere at your machine. CE does not specify how you make your fasteners captive. This idea is of course more work (= costs) but it is something your company can do with standard fasteners. I confess it gets tricky with small nuts but...

 

[geesamand]

Interesting. I have one particular situation where we already have a wing nut on a post and that may be the ideal solution...

Thanks for all of the ideas so far, and hopefully someone else can benefit from this.

I get the impression this is a rich, immature market and if a company comes up with a clean, simply, affordable design they could become the de-facto standard solution. The "Kleenex" of the CE machinery fastener market. Until then though we have to shop carefully.

 

[geesamand]

The reason why I was asking about the average screw quantity per machine is that with such small quantity you can perhaps use standard studs and wing nuts. Drill a hole to one of the nut's wings and fix a small chain to it and the other end of the chain somewhere at your machine. CE does not specify how you make your fasteners captive. This idea is of course more work (= costs) but it is something your company can do with standard fasteners. I confess it gets tricky with small nuts but...

There is an issue here: the latest CE directive does require in some cases that the fasteners can only be opened by tools. Thumb- and wing- heads are not permitted in these cases. There is some disagreement as to which situations dictate tool-only fastenings, so I'm just defaulting to tool-only styles to be safe.

David

 

[KENAT]

Pem actually has some captive fastener products but I think the size & match drill aspect will limit you there.

Posting guidelines faq731-376

http://eng-tips.com/market.cfm?

(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​

 

[geesamand]

I've had a look at the PEM line and similar to accurate screw, their products are focused toward captive nuts fitted to circuit boards. The tolerances are fairly tight and the fastener sizes are on the small end. They're not well suited to bolting sheetmetal covers to cast iron housings.

We've got a batch of M6 size Savetix fasteners on the way. I'm anxious to give them a go.

 

[HDS]

http://www.pemnet.com/fastening_products/pdf/pfdata.pd

PEM has captive screws to M6 in the catalog.

 

[geesamand]

Yes, the PEM PF11 comes in up to 11mm size. In addition to being a relatively complicated item, they require a ductile panel material, a hole size with a .003" tolerance on diameter (no hand drills), a separate pressing operation to install, and cannot be replaced in-kind if damaged because of the damage to the panel hole. For general industrial machinery I prefer to avoid these limitations. I see this fastener to be suited for higher volume product designs with relatively short life cycles or light use.

For outdoor-use machinery and long-life equipment, I prefer the Savetix because it's larger, easier to install, and replaceable. I'll report on my results once our first order comes in and is tested.

 

[KENAT]

Looking at the application page of the Savetix screws it doesn't look like they have much if any float along the screw axis.

This can make installing panels with several of these screws tricky.

That said it looks like the length of plain shank is customer specified so may not be so bad.

Posting guidelines faq731-376

http://eng-tips.com/market.cfm?

(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​

 

[geesamand]

Yes, as you state the shank length is important to consider. We bought both M6x16 long (10mm shank) and M6x10 long (4mm shank) and both were in stock. Plus they can make them to order very quickly from standard parts.

One advantage of their system is that while I'll be dependent on them for washers, but I can modify standard bolts to serve as screws. The washers were very affordably priced so we can afford to keep a big box of them on hand.