How do I go about this??

[vcutajar]

Hi everyone.

I have started work on the MEM Corliss crosshead but had to stop because I wasn't sure which sequence of operations is the best.



I am going to make it from a piece of 60mm BMS.  There will be a 3mm flange at the end with a diameter of 51mm.  The OD of the body of the crosshead will be 29mm and I need to make a hole through the body of 22mm.

So, to all of you expert machinists, should I rough out the OD to 29mm first and then make the 22mm hole, or is it better to do the hole first and then the OD of the body??

What do you think?

Merry Xmas to all.

Vince

[steamer]

If you need to do it in two set ups....do the bore first...then mount on an arbor and do the OD and the flange.

If you can, do the whole thing ( ID and OD) in 1 set up if possible.

Dave 

[vcutajar]

I intend to do it in one setup (not removing it from the chuck).  So bore first and then do the OD.

Vince

[steamer]

Rough it first...including the bore....stuff moves around, stresses are released...so drill the ID, and rough the OD, put a parting tool in to get the flange face, then finish the OD, then bore the ID.   Then finish the parting operation.   If you have to, you can then mount in a 4 or 6 jaw or on an arbor to finish face the flange...but if your careful, you won't need to.

Dave

[Ramon Wilson]

Hi Vince,

I'm with Dave on this one - Rough out all round first - then finish bore first then mount on an arbor as my preferred choice.

However,

As you want to do it all in one hanging I would rough the bore to within a mm of finish then the OD down to plus a mm or so - no more than 2mm. Then do your finishing - the bore first followed by the ODs  That way there's a minimum amount of stress on finishing - Finishing the bore then turning the OD down from 60 to 29mm may induce enough stress to distort the bore slightly especially in mild steel - always an unknown quantity when machining big lumps off though to be fair not so frequent when turning. It's a big lump of steel though - always a risk there.

Hope you don't mind the input after such a while

Regards - Ramon

[vcutajar]

Thanks guys.

Vince