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Posted by Chris Edwards on May 22, 2008, 5:32 am
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wrote:
>
>Thanks for all the suggestions,
>As I was writing the post the solution of using a slitting saw from the
>end then filling the gap with a plug occurred to me and I think this is
>the only practical solution to get a neat result. The Stuart supplied
>casting for this component seems to be made of cast iron so I don't
>think I can silver solder the plug in. I think I will have to pin it
>with some 2mm silver steel rivitted over. Hopefully this will work !
>Thanks again and I hope to contibute more to the forum in the future.
Having done this job on a similar model in the not too distant
past, may I suggest you drill it from both sides as accurately as you can
and then finish off with a sharp miniature file in order to square the ends
of the slot. Little of this work will be seen as it's completely concealed
by the strap, is it not? It really doesn't warrant too much worry!
If you do make a major pigs' of it, you can always saw off the leg
below the fluted casting, drill the casting and make a new leg to be fitted
with Loctite 603, or even instant glue with a little cross pin for added
security if you choose.
--
Chris Edwards (in deepest Dorset) "....there *must* be an easier way!"
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Posted by rsss on May 22, 2008, 5:13 am
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lfoggy Wrote:
> Hi,
> I'm building a model beam engine (Stuart Major) and am starting on the
> connecting rod. This is a fairly faithful copy of full sized practice
> with bearing shells that are held by straps onto the end of the rod. The
> straps are held in place by cotters that have to pass through a
> rectangular hole 3/32 x 11/32 (about 2.5 x 9mm) which passes right
> through the end of the rod which is 5/8 thick. (tried to attach picture
> of drawing) The question is how do I accurately cut these holes ? It as
> to be fairly square with parallel sides. Milling with a slot drill would
> be tricky as even long series slot drills in this size are not long
> enough. I could drill a series of holes and then try to open this out
> with needle files but it would be really difficult to do this neatly.
> Has anyone got any ideas ?
use a square electrode and die sink it.
Take it to your nearest tech college if you don't have one yourself.
--
rsss
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Posted by Trevor Jones on May 22, 2008, 8:59 am
Please log in for more thread options lfoggy wrote:
> Hi,
> I'm building a model beam engine (Stuart Major) and am starting on the
> connecting rod. This is a fairly faithful copy of full sized practice
> with bearing shells that are held by straps onto the end of the rod. The
> straps are held in place by cotters that have to pass through a
> rectangular hole 3/32 x 11/32 (about 2.5 x 9mm) which passes right
> through the end of the rod which is 5/8 thick. (tried to attach picture
> of drawing) The question is how do I accurately cut these holes ? It as
> to be fairly square with parallel sides. Milling with a slot drill would
> be tricky as even long series slot drills in this size are not long
> enough. I could drill a series of holes and then try to open this out
> with needle files but it would be really difficult to do this neatly.
> Has anyone got any ideas ?
>
>
> +-------------------------------------------------------------------+
> |Filename: Connecting rod.gif |
> |Download: http://www.rcgroups.com/forums/attachment.php?attachmentid=1879929 |
> +-------------------------------------------------------------------+
>
Me, I'd drill away as much as possible and take a couple strokes with
a needle file, or shave it out a bit at a time with an end cutting tool.
Possibly hold the tool in the lathe chuck, with the work on a Milling
slide and use the lathe as a shaper or planer, or, if you have one, use
a slide table set-up and hold the tool in a drill press and broach out
the slot after drilling (or milling) most of it away.
Milling cutters as small as this are readilly available with a long
enough reach, and you can make a single lip milling cutter from either a
broken HSS drill shank or a bit of silver steel if you don't mind
working slowly.
Once the slot is milled out, it's a cake-walk to square up the corners!
No need to hack off the end of the casting!
Cheers
Trevor Jones
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>Thanks for all the suggestions,
>As I was writing the post the solution of using a slitting saw from the
>end then filling the gap with a plug occurred to me and I think this is
>the only practical solution to get a neat result. The Stuart supplied
>casting for this component seems to be made of cast iron so I don't
>think I can silver solder the plug in. I think I will have to pin it
>with some 2mm silver steel rivitted over. Hopefully this will work !
>Thanks again and I hope to contibute more to the forum in the future.