Arthur2 wrote:
"John Rumm" wrote in message
...
Arthur 51 wrote:

To clarify.
[modifying ASCII diagram to work in a fixed pitch font!]

-----------------------------------|
wood for tread |
|
|
|
---------------------|-------------|
6mm mdf | |
---------------------|--------|
---
3/4" nail

The cutter will be a flush trimmer of say 3/8" diameter using
a 1/2" diameter bearing. The bearing will run against the mdf.
OK, I can see what you are doing, but not sure why. Is the MDF just to
increase the hardwood thickness? In the above diagram, where would the
riser meet the tread, at the point the MDF stops?

I would have though a screwing and gluing would be better than a nail in
the above situation.

A more usual layout would be:

------------------------------------\ P
A | |
-------------------------------| |
| B |
C | |
|---| |
---------------------------| D |----/ P

A = 6mm hardwood layer,
B = Hardwood nosing,
C = MDF core,
D = Routed rebate for top of riser
P = Pencil round or chamfer to take the arris off the nosing.



The 6mm mdf is a 'jig' that will be removed after the router has done the
edge of the tread.
The bearing of the router bit will run against the mdf.
On fixing the mdf to the underside of the tread the edge of the mdf would be
just shy of
the edge of the tread. To be exact, before routing the edge, the overlap of
the tread over the mdf will
be the difference between the cutter diameter and diam of the bearing plus
an eighth.


Ah, ok this is just for getting a straight edge to the step. Sorry I
though you were planing on leaving the MDF there.

Yup that would work, as would fixing the MDF close to the edge and using
a standard flush trim bit. Personally I think I would just route along a
straight edge clamped to the tread a measured distance from the back.

Alternatively place your MDF pattern on top and use a pattern following
cutter, or simply a guide bush on the router.

When I did my stairs, I simply cut the treads to size with a circular
saw and a saw board, and then routed a bullnose on the nosings with two
passes of a bearing guided half round cutter - once from either side.




--
Cheers,

John.

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