DOM tubing question

[bx24]

I am finishing up my sketches for a new project and I have a DOM question (my projects to date have not had any pivot points)

If the Hyd cylinders I have use 1" pins, do I want DOM tubes with an inside diameter a hair above 1" to allow for grease and movement?

I am expecting to do some light reaming after welding, but I am ignorant as to how to approach this.

Thanks

 

[john_bud]

You want about 0.010" clearance or less. The tighter the clearance, the more spot on the work has to be to let it all go together. You can either get the DOM larger or the pin smaller. Or, you can get the DOM the same size and ream it out to fit. I've done that the red neck way and it works good.

For a 1" ID, get a 1/2" bolt about 5-6". Cut off the head, use a saw to slit the shank down about 2" or a bit more. Then get some sandpaper for a long board (2"x12") with the hook&loop backing and put it into the slit and wrap. You can overlap pieces to get a tight fit. Run that thru the DOM powered by your 1/2" drill. It's slow and you have to keep pulling it out and test fitting, but it works. And much cheaper than paying someone to do it for you.

 

[3RRL]

Good answer on the 10 grand clearance.
I always worked in much closer tolerances (+/- one thou) but found that way too tight for tractor implement clearances. I would get on-size DOM and ream or drill it out. I think you would have to shim a flute or two to get it to cut oversize for proper clearance though. They do make expandable reamers too. I think a 1" drill would probably end up cutting several thousands oversize so it would be a quick way to do it and leave the perfect clearance for grease. You could do it in a mill, drill press or lathe.

 

[chickenman]

another posibility is to chuck the pins in a lathe or drill press and polish them down with abrasive cloth

an external hone can be made by taking 2 pieces of wood and drilling a over 1 inch hole on the join between them and squeezing the abrasice cloth in one side and sliding that up and down

with a little practice some rather close tolerance work can be done

make the hole say an 1/8 or so over so the pin dosnt wedge itself in when the cloth is added

take some wood off one side so the pin touches both sides of the hone with a gap still remaining

i have used external hones by hand to do some extreamly tight work, down to within 2/10.000" and less

 

[dfkrug]

Paul:

It sounds like you have not bought your steel yet. The easiest approach
I have found is to buy the 1.000" ID DOM and then buy 63/64" or 25mm rods
for the pins. The 63/64" rods give you .016" clearance, which is just about
perfect. 25mm rods also give you about .016". The rod stock is easier to
find than the DOM tubing, in my experience.

 

[jimgerken]

There are no DOM questions.

 

[chumly2071]

something to consider is the deformation of the tube bushings caused by your welding process. you may want to use a 1" id tube for a 1" pin, and then ream to your final clearance id after welding for a good fit.

 

[denmansoft]

Just a dumb question from a computer geek getting into tractors....
what is DOM ????

 

[dfkrug]

DOM = Drawn Over Mandrel tubing. I keep a supply of 1.000" ID stock,
which has 1/4" walls. The tubing is made with a welded seam, then a
tool (mandrel) is run down the center which removes the imperfection
caused by the welding process. You get tubing with a very accurately
made bore as a result. THAT is a DOM question!

 

[bx24]

Thanks everyone .... I think I will end up using both the reaming technique and the "smaller rod" technique depending on the application.

There are no DOM questions.

Jim- Thanks for the chuckle