Model Engine Maker

Help! => Specific Engine Help => Topic started by: vcutajar on December 24, 2013, 06:26:11 PM

Title: How do I go about this??
Post by: vcutajar on December 24, 2013, 06:26:11 PM
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.

(http://www.nam-engineering.com/cm/albums/userpics/10009/CORLISS%200195.JPG)

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?? :noidea:

What do you think?

Merry Xmas to all.

Vince
Title: Re: How do I go about this??
Post by: steamer on December 24, 2013, 06:31:32 PM
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 
Title: Re: How do I go about this??
Post by: vcutajar on December 24, 2013, 06:38:07 PM
I intend to do it in one setup (not removing it from the chuck).  So bore first and then do the OD.

Vince
Title: Re: How do I go about this??
Post by: steamer on December 24, 2013, 06:52:00 PM
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
Title: Re: How do I go about this??
Post by: Ramon on December 24, 2013, 06:52:29 PM
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
Title: Re: How do I go about this??
Post by: vcutajar on December 25, 2013, 05:00:53 PM
Thanks guys.

Vince