Covered Topics

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Sunday, June 6, 2010

Homemade Hydraulic Press

Recently, the U-joints started failing on my truck's drive shaft. Many articles on this subject will tell you to us a large C-clamp or even a bench vise to press out the old bearing cups. Since I don't have a large enough bench vise to do this with, I opted for the C-clamp option. That didn't work out so well.

The C-clamp twisted and buckled when attempting to apply the necessary force to break the rusted parts loose. In the process of taking apart one U-joint I broke two C-clamps. I needed something considerably more stout, and the local auto parts stores didn't have any U-joint presses to rent. On thinking about the problem, I realized I could use a pair of thick metal bars with an allthread rod through either end with jam nuts to hold the bars in place. A "bottle" style hydraulic jack could sit on one bar while squeezing the workpiece against the other. A friend, who is a mechanical engineer, advised me on what thickness of metal to use and where I could buy it online.

The top and bottom "bars" are made of 9 lb/ft A-36 "C-channel" hot rolled steel and were ordered from "Speedy Metals". Their web site is These two pieces are 5" wide, 1.885" high, 0.325" thick, and each is 12" long. They were expensive - about $29 for the pair + another $16 for shipping. If my truck had been safe to drive the 20-30 miles EACH WAY I would have shopped locally at a scrap metal yard and possibly saved some dough. The "allthread" rods are each 3/4" in diameter and bought online from McMaster Carr at These, along with a suitable drill bit to make the holes for them, cost me almost $60.

A "posed" shot of the press appears below. This was taken after the work on the drive shaft had been completed. By then I was tired and did not take the time to "square up" the top bar as I would in actual use. Thus it looks crooked in the picture. At least you get the general idea of how it works:

Some Items of Note:

1) ALWAYS use eye protection - if something breaks under this much pressure shrapnel can fly everywhere!
2) This press worked quite well for its intended purpose, but as shown it is awkward to use. One almost needs a helper to steady it to keep the parts from flopping around while one sets up the work to be pressed.
3) I used regular, non-impact type wrench sockets. One was slightly smaller than the diameter of the bearing caps I was pressing; the other was slightly larger so as to support the drive shaft yoke while allowing the other bearing cap to pop out.
4) Lay the drive shaft on boxes, books, or whatever you have available so the yoke lines up with the top of the hydraulic jack and is thus square with it. That's why I had the black plastic "milk crate" in the photo located directly behind the press.
5) I soaked all parts with WD-40 spray the night before starting work on this project, as they were badly rusted.
6) When the rusted parts broke loose, they made quite a BANG along with a spark as the pent up energy was released. Definitely best to use this well away from any fumes that may be ignited by sparks.
7) All told, the metal, allthread rods, nuts, and the 7/8" drill bit used to drill the metal to accommodate the allthread, cost me a little over $100.
8) Drilling the holes - I thankfully own a drill press - bought at an estate sale - with a 1/2" chuck capacity. A 7/8" drill bit will have a 1/2" shank or larger. If you duplicate my project you will need either a drill press (ideally), or be strong enough to hold a 1/2" chuck electric hand drill steady when it goes through the bar and "grabs". In either case, use a few drops of motor oil on the drill bit and take it slowly. Failing all that you will need to find a friend with the appropriate equipment or perhaps take it to a machine shop.
9) When pumping the jack, take short, slow, gentle strokes. Do NOT pump the handle through its full vertical travel. This helps maintain better control of the pressure being exerted on the work.
10) A typical "bottle" style jack, available at most auto parts stores, can exert up to several tons of force. That said, use ONLY the amount of force you need - excessive force may bend or break expensive parts such as a drive shaft yoke.

Improvements I want to make:
1) Use either some more metal, or even 2X4 lumber, to make "feet" for the bottom bar of the press. I would also have the allthread rods clamped in some manner so that they are held vertical and don't flop around.
2) I've only had the metal in my possession for about 3 weeks, and already it is starting to rust due to the high humidity we've had. Cleaning and painting the metal channel bars with car engine paint and keeping the allthread oiled is clearly a good idea in view of this.

Granted, the press cost me a sizable fraction of what I could have paid to have the drive shaft professionally done - even with the current $80/hour shop rates in my area. However, I now have a tool that can be used on future projects.