Hydraulic fittings Qs.

[Green_in_MI]

Does anyone have a link to a source for learning about the various types of hydraulics fittings. I need a basic primer/introduction to thread types and sizes, etc. I am quite confused about the assortment of o-ring, threaded, letters, numbers and such used to identify the fitting type. I don't want to ever pay way too much again to my tractor dealer to make up hoses and fittings for my projects. I want to be able to go to the TSC or buy from the Northern catalog and know what in the world I need.

For instance, today I wanted to buy additional hose to provide some extra slack in a hydraulic line when I use an implement. I simply wanted a coupling that I could thread on each male end of the hose to lenghten it. All I could find on the shelf was this weird female/female coupling that was threaded on one end and had a thread with an o-ring on the other. I only presume the 3/8 inch size it said it was, is what I needed. Duh! I says to myself. Why is this different and will the thread and o-ring side actually fit on the threaded male end of the hose? Of course no one in the store can tell you so I ask you folks.

I am going to figure this out especially now to complement the fittings I already have on my tractor and accesories I have modified. Thanks for any help and happy new year.

 

[Anonymous Poster]

This link should get you started, just click on the RED number to get to the pages you need.
O ring straight thread connections are primarily designed for situations where the joynt will be disconnected and reassembled multiple times in it's design life. Taper threads actually self destruct when they are made up more than once.
When in doubt, look to Aeroquip.
Happy learning
http://www.hydraulic-supply.com/pdf/1192.pdf

 

[gordon]

Here is another link that is good for general hydraulic knowledge.

<A target="_blank" HREF=http://www.adtdl.army.mil/cgi-bin/atdl.dll/fm/5-499/toc.htm>http://www.adtdl.army.mil/cgi-bin/atdl.dll/fm/5-499/toc.htm</A>

Gordon

 

[Spencer]

I checked out your bio but it is incomplete. If you are anywhere near Muskegon I can point you to the place I get all my hoses and fitting. I can walk in there and tell them exactly what I want or I can bring in part of a project and let them figure out what I need. Not only do they have everything I would ever need for pneumatics, hydraulics, and water, but they make it up right then and there for very reasonable prices.

 

[herbenus]

What do you mean "tapered threads self destruct"? Pipe threads are tapered and I re-use them all the time -around the house and at work to 3000 psi. I know compression type tube fittings generally aren't good for re-use, but I never had trouble with tapered pipe threads. Except maybe brass fittings. Steel only when not properly made up with teflon, or not torqued properly. I'm not looking to start a long thread (or argument), just looking for clarification of what you mean by tapered threads self -destruct.

 

[Anonymous Poster]

By the very nature of the design of a tapered thread, each time it is made up, the thread eats itself away, and the male portion becomes smaller. I know you won't believe that, until you get a set of micrometers and prove it to yourself. Tapered pipe threads are not designed for multiple make ups.
Now, as to teflon tape, please recognize that teflon tape is NOT a thread sealant, it is a lubricant that allows additional torque to be conveniently applied in the makeup of a thread, thus allowing tighter makeup of a tapered thread. Minimal particles of teflon will fill in the defects in the threads themselves, and might provide soem sealing, BUT, teflon tape is NOT a sealant. Many hydraulic manufacturers clearly state the warranty of their product will be void if teflon residue is found upon inspection. All too often systems get plugged up by the residue of teflon tape.

 

[Green_in_MI]

The site you linked was very informative. I learned a lot , thanks. I am about 90 minutes from Muskegon. The Hydraulic Supply site says that the NPTF threads are not recommended for hydraulic fittings. I can understand that from the description of how they work. What I don't understand now is why most of the hydraulic fittings on Northerns web site and the fittings at the TSC are NPTF on at least one side. THe other end being NPSM or o-ring bosses.

They also say that the best fittings are those with o-ring inside the faces. I notices several of the fittings I bought from Deere have them. Maybe that is why I spend so much money there. The quality does seem to match the price.

So what I think I have learned is that NPFT fittings do match straight thread NPSM pipe, just don't take them apart often or they will soon leak. I think I know which fittings I can get from TSC now to get my snowplow project fine tuned.

BTW, a front mounted loader blade is almost unfair. Absolutely no contest, tractor wins.

 

[tomrscott]

That link to the Army Mil FM 5-499 is no longer working. I managed to truncate the URL back to where I got into the library site, and when I did a search for the FM 5-499 it turned up empty. Not even listed in the superseded list. Does anyone know what the title is? Maybe we can search for it that way.

 

[jsigrist]

Try this url for the MIL FM 5-499 document.

https://134.11.61.26/ArchivePub/Publications/DA/FM/ByPub.htm

 

[vicashoe]

I found this book to be a plethra of hyd knowledge. It is Industrial fluid power vol 1 Third edition published by womack educational publications. This is a very easy to understand book and it has a lot of info on hyd applications. If you look on Ebay or Half.com usually you an buy one cheap. Also if you want to call Discounthydraulichose.com at 1800 535 1302 they will help you in your quest for fittings hose and the like. I went to reuseable hydraulic fittings for all of my hose needs all I have to do is buy the hose from these people and cut it to length screw on the reuseable fittings and I am running again in about 20 min. Good Luck /forums/images/graemlins/cool.gif