R109 clamp screw size?

[HenrikBP]

I'm taking apart and cleaning up a couple of R109 regulators bought off of eBay.

SP used different screws with different thread pitch on these; One type with regular slots and fine thread and another type with philips head and a slightly more coarse thread.

Unfortunately the seller, who apparently had quite a few of these, didn't realize this and had tried to jam slotted screws in clamps fitting philips head screws.

The clamps I have fit the coarse thread philips screws but I need a few more of them.

As far as I can tell with a thread gauge they're 40 thread count (or 0.65 in metric?) and just over 1/2" long including the head. Diameter is 0.106" - which doesn't convert to fractions well but 7/64" is close (= 0.109")

McMaster doesn't have anything like it, and especially not in chrome plated brass.

Are these available from SP? Any other leads for where to get these?

Thanks

Henrik

 

[DA Aquamaster]

Hmm...I looked through my box of left over R109 cover screws and I had lots of the new ones that are phillips head, I have two of the older ones that are socket head and I have some regs with the even older slotted ones and they are all fine thread.

I suspect the ones you have that fit the courser thread screws may have been retapped for the courser thread.

 

[Luis H]

The course thread screws used on the clamps are # 4-40 .
The nominal diameter is actually 0.112 (the OD on threads often tends to measure less than the nominal).

I would use a stainless steel screw like the McMaster Carr # 91794A110 or similar.

I am not sure the size of the fine threads screw, but my guess is that it would be a # 4-48. I will find out soon since I also have some clamps with the fine threads.

Machine screws in the US below 1/4" are sized by numbers not fractions.

 

[Luis H]

Hmm...I looked through my box of left over R109 cover screws and I had lots of the new ones that are phillips head, I have two of the older ones that are socket head and I have some regs with the even older slotted ones and they are all fine thread.

I suspect the ones you have that fit the courser thread screws may have been retapped for the courser thread.

I don't know when the course thread clamps where used, but I have both kinds. I talked with two of my LDS about it and they both confirmed that there has been two different screw threads used (both LDS have been Scubapro dealers for a long time).

I have only being able to confirm the course #4-40 since that is the screws I have handy (same screws we use in for the double hose, hose clamps).

It would be logical that the fine thread is the #4-48, but it could be that it is a metric thread.

 

[captain]

Take your clamp to a hardware store and look in their stainless steel machine screws until you find the correct one.

 

[redacted]

I've run into four variations of that socket head screw. An allen headed one and a large phillips one both with the coarse threads. And a slotted one and a finer phillips headed one both with the fine threads. The coarse thread is 4-40. I picked up a bag of 4-40 x 1/2 brass machine pan headed slotted screws to use in a pinch. It would have left the head showing if I did not reduce the radius of the pan head with a Dremmel grinder. I assume the fine thread is the newest as they were included in G200 kits for a while. All the socket head screws appear to be stainless steel (mildly magnetic).

 

[HenrikBP]

Thanks all. Great info.

I did look at stainless at Mcmaster (hardware stores around here are quite rudimentary in what they stock ...), but was concerned about reaction between the dissimilar metals.

These from Mcmaster seem like a near-perfect replacement: 91737A084

Luis: do you use 1/8" rubber caps for your DH thumb screws? (smallest I could find at Mcmaster)

Henrik

 

[Luis H]

Thanks all. Great info.

I did look at stainless at Mcmaster (hardware stores around here are quite rudimentary in what they stock ...), but was concerned about reaction between the dissimilar metals.

These from Mcmaster seem like a near-perfect replacement: 91737A084

Luis: do you use 1/8" rubber caps for your DH thumb screws? (smallest I could find at Mcmaster)

Henrik

That part number should work well if you prefer a Phillips head screw (that is just personal preference, I like the slotted or hex key Allen wrench type).

Dissimilar metals can be a concern, but if you soak the regulator regularly and take it apart occasionally you should be able to avoid any problems. You could also put a tiny bit of silicone grease on the threads before installing them.


I got the thread protector caps from Bryan at VDH and I believe they are the vinyl type which comes in smaller size, but I think the ones he picked are for 1/8 OD rod, I am not sure.

 

[HenrikBP]

Thanks Luis.

Henrik