James Bailey

Funny very, very funny . So looks like most far over tighten them !!!

Fogey1

Interesting, the synchronicity of issues. There's this thread, as well:

Hose clamp size decoding..
https://rennlist.com/forums/928-foru...-decoding.html

danglerb

Tension from torquing will be very different for a cheesy Zebra type clamp vs a Norma with a threaded nut and bolt.

pfbz

I realize this is a very old thread, but I was searching the internet for info on this exact question, came across it. The torque values listed above seemed really low, so I searched a bit more...

Found these recommendations from JCS, a UK maker of high-quality embossed-style hose clamps, similar to Norma. These seem much closer to what I would expect...

Clamp size (max part of range)

• 20mm and under: 3 Nm (26 inch/pounds)
• 20mm - 45mm: 5 Nm(45 inch/pounds)
• 50mm+ : 6 Nm (54 inch/pounds)

(Attached is the pdf from which I gleaned this info)

dr bob

So... What tool do you all use to verify tightening torque at 2 lbs/ft? Just curious. I found a cool Japanese torque screwdriver many years ago for just such low-torque applications. Initial use was to verify electrical screw terminal tightening torque in plastic terminal blocks. Nuke-spec QC stuff. Now it languishes in a waxed cardboard box in the toolbox.

The Norma spec sheet numbers look good for their clamps. The more common in the US "Ideal" brand stainless worm-gear clamps use pretty much the values.


In the end, most folks tighten them until they are snug, then a little more if they leak. The numbers from the manufacturer define what the clamp likes, not what it takes to get a hose to seal on a particular fitting or nipple. "Too Tight" risks damaging the outer jacket on a hose, and will often fracture a liner in a multi-layer hose especially when fitted over a barbed nipple. For hoses over nipples that have a flared end, the edge of the clamp needs to be at least one hose wall thickness from flare even if the flare is a bubble (rounded) and not a sharp barb. It's OK to add a soapy/detergent water lubricant to the outside of the hose to allow a standard screw clamp to slide a little while tightening. Else there's risk of uneven pressure around the hose.

j.kenzie@sbcglobal.net

This all makes sense. On the other hand, I have had occasions where I have had a coolant leak that I fixed by tightening the hose clamp. Often it needs more than 2-3 foot-pounds. Maybe I'm masking another problem when I tighten so much as 10 foot-pounds, by feel, but sometimes it works.
Dave

pfbz

I have several specific-torque t-handles, mostly used in the bicycle industry for clamps on carbon fiber parts, but I just ordered one of these CDI adjustable torque t-handles, it was about $45 shipped on ebay. 2-8 Nm.

Adk46

If you powder coat your water bridge and err by coating the nipple area, and further if your PC guy loses the circular wire bale that goes in the groove that provides a small barb, no amount of torque on the clamp will stop the hose from slipping off. In this I am an expert, though still a trainee on the fix.

jtrygstad

I like these clamps. Beats the "ideal" from Home Depot.

http://www.hps-siliconehoses.com/hps...r-coolant.html

Imo000

I tighten them until it feels tight. Sorry, can't describe it any better.

Snark Shark

I generally just make them screwdriver tight, but for some reason my brand new power steering feed hose wept a little at the reservoir until I tightened the **** out of it.

dr bob

And that's kind of my point -- The actual clamping pressure varies a lot. Hose wall thickness, the type of nipple they hose is fit over, and the actual service (fluid and pressure in the hose) all play a part in how tight you want to make the screws. Witness the evolution of "fuel injection"-style hose clamps. Born of a need to get adequate clamping on small hoses without distorting or cutting the outer shield layers.