Newbie hydraulic press question

[leeko]

Hi all,

I just picked up a hydraulic press (basic 12 ton HF version, nothing fancy), and already I have a question. This is probably screaming obvious, but I can't seem to get my head around it.

I have a 1/2" mild steel rod, 24" long and threaded 1/2-13 on one end. On the other end, I'd like to press on a 2" long stub with a blind hole, 1” diameter (1/2" hole for the press fit).

How do I go about this without bending the long rod (and/or sending it flying)? I figure if I drop the platen of the press low enough to fit the whole 2ft length of rod in, the rod will just bend before the press fit happens.

Thanks for any pointers you can give,

Lee

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[DougWil]

1st off, do even have the required negative clearance and tolerance for a "press fit"?

Couple of ways, a clamp arraigment around the 1/2" rod close to where the stub is pressed on.

Long thick walled tube to keep the shaft from buckling capped at bottom and ears on top to set on platen. That is how axle shaft bearings are pressed off.

 

[joe49]

Heat female piece and cool male piece, depending on how much interference fit you have, you may need no press, just assembly.

 

[leeko]

Doug: I'll be reaming and/boring the stub part on the lathe, so I can create however much interference I need.

I figured no matter what type of clamp or vise I use on the shaft, it's unlikely to resist the press without marring the shaft... If anyone has a picture of a similar setup, that would help a lot.

Thanks again

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[Cobra5150]

Clamp support near the press head enough to keep the rod steady then rest the rod on a solid surface. If I was doing this I would use my drill press vise with aluminum inserts with reliefs to clamp the pipe hopefully without marring it. Then press the stud onto the shaft. The support at the top should keep it from bending and with the rod on a solid support no reason for clamping too tightly.

 

[DougWil]

Two 2"x2" steel blocks with a reamed 1/2 hole between them and 2 or more xbolts have a lot of clamping force.
This kind of arraignment.

If you need more than that a shoulder on the shaft.
Or the long tube that doesn't allow the shaft to buckle.
Could you just use a x pin? or set screw? or silver solder?

What you are proposing isn't how a manufacturer would typically do it.

 

[leeko]

Thanks guys. Doug, that clamp block looks just the ticket, thanks for that.

I realize it's not the manufacturers way, and ideally I'd like to turn the piece from a single length of 1" stock, but I'm lacking a steady rest/follow rest for the lathe so this is "next best".

The piece is for a drawbar on a brown and sharp #9 taper milling machine. On this particular machine, the drawbar is also used to forcefully eject the tooling (bs#9 taper is notorious for getting stuck in the taper), so it's important that it be as strong as possible. I'd worry that a cross pin would shear with the forces involved, and I had to get rid of my OA setup a while back so silver brazing isn't an option. I figure a tight press fit with
loctite is next best. May also cross pin it for belts and suspenders approach

Thanks again for the advice,

Lee

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[DougWil]

OK, a drawbar.

I think with the axial stress of tightening that drawbar, loosening and tapping on that drawbar that a press fit won't last long, especially with soft mild steel.
Brazing, silver soldering or plug welds would be better.

I would opt for 4140 prehard instead of mild steel too.

 

[leeko]

I could bore through the stub, and plug weld the top... Thanks for the 4140 suggestion, I've used that a couple times and it turns nicer than 1018.

Thanks

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[404]

As you have a lathe suggest you thread the rod. Through drill the slug and tap, assemble with loctite as desired, face off the slug/rod if needed.

Small diameter press fits can be a real pain in the *** to get just right. Train tires on the wheels are a lot easier.

 

[leeko]

Would threading it on with loctite be stronger than plug welding?

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[hawkeye2]

Thread the end screw on a coupling but, and put a roll pin or two in so it doesn't unscrew when listening the draw bar. If you let the rod stick out the top of the nut a little, you can peen it over so the rod (not the nut) takes the load when you unseat the taper.

 

[DougWil]

They make "permanent" locktite.


But I would thread it all the way through the slug, make the drawbar threads 3/8" short of flush. Tighten it good, preheat the weld end to 350-400 degrees, tighten it good again and reach down and plugweld down through the top.
Let cool slowly, in lime, dry warm sand, or top of the woodstove....

 

[Kevin54]

You would be better off having the piece welded on instead of using the Loctite.

 

[MJD1]

Use a split shaft collar on the shaft, setting that on the press plates. Heating the bored object and freezing the shaft will let you get by with the tightest interference fit.

 

[404]

With welding comes warping. In this case threading will be stronger than welding.

 

[DougWil]

With welding comes warping. In this case threading will be stronger than welding.

Thread and weld.
There won't be any warping at the very top of a drawbar "nut".