M20x1.5 to M16x1.5 Thread Reduction

[spggodd]

Hi all and thanks in advance,

I have an application whereby one piece of the assembly (A Load Cell) has an internal thread of M20x1.5, due to space constraights I need to screw this directly into an actuator with an external M16x1.5 thread on the plunger.

I have requested if the Load Cell can be manufactured with a smaller thread and am awaiting correspondance.
I have also tried looking at helicoils (not much luck) and small reducer pieces.

Does anyone have any clever ideas of how to reduce the thread down to the size I need?

Thanks
Steve

 

[JohnRBaker]

Can you replace the shaft on the actuator with perhaps one that is stepped-up to accept an M20x1.5 thread?

John R. Baker, P.E.
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Siemens PLM Software Inc.
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[MintJulep]

Fill the hole in the load cell with JB Weld. Drill and tap for M16x1.5.

 

[Tmoose]

what kind of loads?

I'd be thinking about drilling and tapping a piece of a M20x1.5 bolt.
The abutment requirements might need a fancier flange be included.

 

[spggodd]

The load cell is rated at 20KN, I want to push approx 5KN.
To be honest the Load Cell is overkill, but it is 20KN so that it can be interchanged with other equipment we have.

I was tempted of the idea to tap an M16x1.5 thread in a M20x1.5 bolt, I was just concerned about wall thickness..

 

[CoryPad]

The wall thickness would be < 1 mm, but the remaining cross sectional area would be ~ 100 mm², so the stress from 5 kN would be ~ 50 MPa.

 

[ornerynorsk]

M16 id helicoils are going to have M22 od. Do you have room for even a very short adapter spud?

It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.

 

[Tmoose]

M20 x 1.5 tap drill = 18.5 mm (the hole in the load cell prior to threading) - of no real consequence anyhow
M20 x 1.5 external thread (bolt) minimum minor diameter 0.704" = 17.88 mm

M16 x 1.5 internal thread (hole tapped in bolt) major diameter minimum ~ .630" or a squeak over 16 mm

since the pitch is the same 1.5 for both threads seems like the nominal wall, if the threads are synchronized in the worst possible way is indeed a little less than 1 mm.
If they are synchronized to be "out of synch" it would be more like 1.25 mm.
I'm not sure how well it would survive the stress of tapping. Maybe single point threading would be gentler.