Pressing plugs into Aluminum

[daewoo]

We press an anodized Aluminum 1.314" dia x .44" Long plug with a 15 degree chamfer cut .06" deep into an anodized Aluminum block where the tolerance between parts causes an interference fit of .001" to .003".
Plug also has a sealant groove of .02 to .06 wide and .01 deep for loctite.
Does anyone have information on chamfer design to provide optimal pressing conditions.
We wish plug to go in with minimal force, straight and allow air seal. Block air pressure when energized is 90psi.

 

[JAMCO]

Can you heat up the part which the plug is pressing into? We perform shrink fits all the time with aluminum, and your interference range of 0.001 ~ 0.003 is right in the reasonable value for a shrink fit. If you could heat up the 'hole' to be roughly 240 deg. F hotter than the plug, you will expand it's diameter by ~0.004 and the plug should drop right in. Freezing the plug can help keep your total temperature down such that you may be able to use the loctite as well.

With this appoach your 15 degree chamfer should be adequate. A 0.003 interference fit performed with a thermal shrink in this manner should resist 90 psi (122lb F) many times over.

 

[daewoo]

Jamco,
Thanks for the response, unfortunately we cannot heat the block but we could cool the plug.
Question is truly with regards to what is the optimal chamfer and the minimum interference fit for this pressing operation, where parts cannot be heated.

 

[jbel]

Instead of a chamfer why not use a stepped diameter design, similar to a die or fixture button? A diameter step down of 0.003"-0.005" only for the length of the chamfer you have should provide the alignment you need. Then press the plug in. The advantage over a chamfer is in the axial alignment provided by the stepdown design. The plug will align itself with the hole and shouldn't become cocked when you press it in.