# Latching issues



## Clint (21 Jan 2013)

I have an issue with a thin walled part springing open when split. Material is 4140 18-22 Rc OD 113.4mm ID 107 mm by 51 mm long, after turning the part is split with a 6 mm end mill and consequently springs open. Any suggestions for preventing this from occurring would be greatly appreciated.


----------



## jasonB (21 Jan 2013)

A common problem with any cold rolled metal, heating to red heat and holding it there for sohe time before allowing to cool as slowly as possible helps or try and source the metal in its black (hot rolled ) state.

You could also make teh part to a smaller dia and cut a norrower grove, that way when it springs open it will be the right dia and the correct grove, this would need a bit of trial and error before the ideal combination was found


----------



## Cheshirechappie (21 Jan 2013)

4140 - 708M40, En19?

I suspect that deflection is the result of residual stresses set up during heat treatment being released by the splitting operation. Not sure how possible this is, but can you machine the component with the material in the annealed condition, and heat treat subsequently? Another possibility is to determine a smaller OD to machine stock material obtained in 'R' condition to, with the same wall thickness, then split, such that the sprung-open component achieves design dimensions. A third option is to machine 'R' condition material to somewhat generous on design dimensions, then split, then finish OD and ID by mounting on custom-made mandrels or turning fixtures.


----------



## CHJ (21 Jan 2013)

Try machine to size, anneal as mentioned by jasonB and re-treat to required temper then split.

Over the top in detail I suspect for your needs but *details of recommended temps are here*

Edit: alternate, compress and fit existing sprung pieces into collar of required correct bore and anneal.


----------



## WoodMangler (22 Jan 2013)

jasonB":d9300dpy said:


> A common problem with any cold rolled metal, heating to red heat and holding it there for sohe time before allowing to cool as slowly as possible helps or try and source the metal in its black (hot rolled ) state.


If you have an open fire: heat the metal to red for a while, then bury it in the ashes under the fire and leave it till the morning to cool down.


----------

