M12 x 1.75 Bolt Kit for 6" Heavy Duty Tri Clamp, Deep Brass Nut
ABOUT THIS PART
Replacement hardware for the heavy casting 6 inch high pressure tri clamp. One set is one bolt, one split lock washer, one deep brass nut. A clamp takes two sets.
| Complete set: bolt, washer, deep brass nut | $38.50 |
| Deep brass nut only | $5.45 |
| Split lock washer only | $2.95 |
The nut and washer are sold on their own because they are the parts that wear out.
Check this is your hardware first
Put a wrench on the nut.
- 3/4 inch wrench and an M12 bolt: this is your hardware
- 5/8 inch wrench and a 3/8 inch bolt: you need the 3/8 inch set instead
The thread is M12 x 1.75, metric. These clamps get called half inch bolt clamps and the hardware gets listed as 1/2 inch, but M12 measures 0.472 inches and a 1/2"-13 bolt measures 0.500 inches. A hardware store bolt will not thread into this nut.
It does not fit a standard 6 inch tri clamp, and it does not fit any clamp closing on 3/8 inch hardware.
Specifications
| Bolt | M12 x 1.75 x 4 in, 304 stainless |
| Nut | Deep brass, 0.66 in tall, 0.75 in across flats |
| Standard M12 nut, for comparison | 0.394 in tall |
| Washer | 18-8 stainless split lock |
| Sets per clamp | 2 |
| Wrench | 3/4 in |
| Torque, elastomeric gasket | 30 in-lbs |
| Torque, rigid gasket | 50 in-lbs |
Torque is set by the gasket, not by the clamp. Which gasket you run decides whether you pull 30 or 50 in-lbs, and that choice is covered in Choosing the Right Gasket Material for Tri-Clamp Connections.
Why brass, and why so tall
Stainless threaded into stainless galls and seizes, and the nut ends up cut off. Brass on a stainless bolt does not gall, so the joint can be broken and remade over and over. We do not offer a stainless nut for this clamp.
The nut stands 1.7 times the height of a standard M12 nut, so it engages 1.7 times the thread. That engagement is what holds a 6 inch joint at pressure through repeated cycles.
Replace on a schedule, not on appearance
- Brass nut: every 6 months in service
- Bolt: every 12 months
- Any nut that runs on noticeably easier or harder than the one beside it
The brass nut is the softest part in the joint by design, so it deforms instead of the bolt. After several cycles the torque needed to reach the same clamp load climbs, and the wrench stops telling you what is actually holding the joint. There is no published cycle count for this nut, and anyone who gives you one is guessing.
The split lock washer is not optional. A flattened, reused washer is the most common reason a heavy clamp loosens between services.
Stock and lead time
Complete sets and brass nuts ship from Bend, Oregon. Split lock washers are restocked within a week. Worst case lead time on any part of this kit is 30 days.
SPECIFICATIONS
▦ IN YOUR MANUAL
This part appears in the operator manual that ships with your system. The QR code there links to this page.
◈ REFERENCE FOR THIS PART
COMMON QUESTIONS
Which 6 inch clamp does this fit?
The heavy casting 6 inch high pressure tri clamp, the one that takes an M12 x 1.75 bolt and a large deep brass nut on a 3/4 inch wrench. It does not fit a standard 6 inch tri clamp.
How do I know if my clamp takes this hardware?
Put a wrench on the nut. A 3/4 inch wrench and an M12 bolt means this is your hardware. If it takes a 5/8 inch wrench, you have a 3/8 inch bolt clamp and you need the 3/8 inch set instead.
Is the thread M12 or 1/2 inch?
It is M12 x 1.75, which is metric. These clamps are often called half inch bolt clamps and the hardware gets listed as 1/2 inch, but M12 is 0.472 inches and a 1/2"-13 bolt is 0.500 inches. They do not interchange. A 1/2 inch hardware store bolt will not thread into this nut.
How many sets does one clamp need?
Two. One item here is one complete set of bolt, washer and nut. A heavy casting 6 inch clamp has two bolts, so a full rebuild is quantity 2.
Why is the brass nut taller than a standard M12 nut?
Because it is a deep nut, which is the manufacturer's own term for it. A standard M12 hex nut is 0.394 inches tall. This one is 0.66 inches tall, about 1.7 times the height, so it engages about 1.7 times the thread. That extra engagement is what holds a 6 inch joint at pressure through repeated cycles.
Why brass instead of stainless?
Stainless threaded into stainless galls and seizes, and the nut ends up being cut off. Brass running on a stainless bolt does not gall, so the joint can be broken and remade over and over.
Can I use a stainless nut instead?
N.B. Oler does not offer one for this clamp and does not recommend it. Brass is the correct pairing here and stainless on stainless is how these joints get destroyed.
How often should the brass nut be replaced?
Every six months in service, or any time a nut runs on noticeably easier or harder than the one beside it. There is no published cycle count for this nut. What is established is that as a nut is reused, the torque needed to reach the same clamp load climbs, so the wrench stops telling you what is actually holding the joint.
What torque should I use?
The gasket sets the torque, not the bolt. 30 in-lbs on elastomeric gaskets, meaning Buna-N, Viton, EPDM and silicone. 50 in-lbs on rigid gaskets, meaning PTFE and Tuf-Steel.
Do I really need the split washer?
Yes. It holds preload on a joint that gets cycled, and a flattened reused washer is the most common reason a heavy clamp loosens between services. It is sold separately at $2.95. Some people call it a crush washer; it is a split lock washer, 18-8 stainless.
Can I buy just the bolt?
No. The bolt is only sold as part of a complete set. The brass nut and the split lock washer are sold individually because those are the parts that wear.
What is the clamp itself rated for?
The heavy casting 6 inch high pressure tri clamp is rated 300 psi at 70 F (21 C), derating to 200 psi at 250 F (121 C).