OEM hose fitting in Beneteau stern tube has metric thread M10-1.5. The hose fitting can be made by modifying M10-1.5 x 60mm long bolt and M10-1.5 hex flanged nut from the highly resistant to sea water corrosion Titanium (Ti). Titanium fasteners are available on eBay at reasonable cost, machining however is difficult due to low thermal conductivity and high hot hardness of material.
Described DIY Titanium hose fitting can be also made from M10-1.5, 316 SS bolt and hex nut. However, even if passivated after machining, 316 SS may develop in time pitting corrosion in the stagnant, Oxygen deficient sea water in the stern tube.
On PIC 1 are shown all required dimensions for the Ti fitting, Drilling Jig and drill bitts. Drilling Jig is made from a piece of hardwood cut on a mitre saw and holes drilled on a bench drill press. After drilling, the wood was cut by a hand saw.
PIC 2 shows ordered 70mmTitanium bolt and flanged hex nut. Bolt was cut with a hacksaw. Both ends of the bolt were finished to required length on a bench grinder. Flange of the Titanium nut was also removed on a bench grinder.
To make dimple on both sides of the bolt and ensure drilling in the centre of the bolt, the Centre Drill was fixed in the V shaped notch of a drilling vice and Titanium bolt was rotated in the chuck of the drill press.
See You Tube: “How do you make a hole in a steel rod”. This trick was used ONLY for making dimples on both ends of Ti bolt.
PIC 3 shows drilling hole on a drill press using Drilling Jig. This is most difficult task in modification of the bolt, but possible:
• Use lowest RPM in the drill press
• Buy Cobalt drill bits
• Make VERY FREQUENT PECKING to remove chips and to cool the drill bit with a cutting fluid
• Drill 1/2 depth from both sides to reduce heat drilling deep hole and to drill from the other side when broken drill is stuck in the hole
On PIC 4 are finished fittings made from Ti and SS. Score bottom of the nut and lower sides of the hex with a hacksaw. There is no need for barbs on the hose fitting; hydrostatic pressure at the depth of the fitting is lower than 1psi, and 3/8” DIA hose should be pulled-off from the fitting during haul out to check for calcium/salt blockages.
NOTE:
• To prevent breaking OEM hose fitting during removal from the stern tube, use soldering iron to heat the fitting and soften epoxy.
• Put hex nut on Titanium fitting and bond/seal with epoxy before installation of the fitting in the stern tube.
• For bonding I used J-B Marine Weld Epoxy mixed to desired consistency with Cab-O-Sil.
Described DIY Titanium hose fitting can be also made from M10-1.5, 316 SS bolt and hex nut. However, even if passivated after machining, 316 SS may develop in time pitting corrosion in the stagnant, Oxygen deficient sea water in the stern tube.
On PIC 1 are shown all required dimensions for the Ti fitting, Drilling Jig and drill bitts. Drilling Jig is made from a piece of hardwood cut on a mitre saw and holes drilled on a bench drill press. After drilling, the wood was cut by a hand saw.
PIC 2 shows ordered 70mmTitanium bolt and flanged hex nut. Bolt was cut with a hacksaw. Both ends of the bolt were finished to required length on a bench grinder. Flange of the Titanium nut was also removed on a bench grinder.
To make dimple on both sides of the bolt and ensure drilling in the centre of the bolt, the Centre Drill was fixed in the V shaped notch of a drilling vice and Titanium bolt was rotated in the chuck of the drill press.
See You Tube: “How do you make a hole in a steel rod”. This trick was used ONLY for making dimples on both ends of Ti bolt.
PIC 3 shows drilling hole on a drill press using Drilling Jig. This is most difficult task in modification of the bolt, but possible:
• Use lowest RPM in the drill press
• Buy Cobalt drill bits
• Make VERY FREQUENT PECKING to remove chips and to cool the drill bit with a cutting fluid
• Drill 1/2 depth from both sides to reduce heat drilling deep hole and to drill from the other side when broken drill is stuck in the hole
On PIC 4 are finished fittings made from Ti and SS. Score bottom of the nut and lower sides of the hex with a hacksaw. There is no need for barbs on the hose fitting; hydrostatic pressure at the depth of the fitting is lower than 1psi, and 3/8” DIA hose should be pulled-off from the fitting during haul out to check for calcium/salt blockages.
NOTE:
• To prevent breaking OEM hose fitting during removal from the stern tube, use soldering iron to heat the fitting and soften epoxy.
• Put hex nut on Titanium fitting and bond/seal with epoxy before installation of the fitting in the stern tube.
• For bonding I used J-B Marine Weld Epoxy mixed to desired consistency with Cab-O-Sil.
