Got a mate that’s building a fan shroud for a nightclub.
The ID of the ring is 2000 mm, he’s using 16 mm thick MDF wood to make the ring so the OD will be 2032 mm.
He wants to know how many cuts with a 3mm thick blade he has to make to make the wood flexible though to curve enough to make a ring shape.
I reckon it’s 33 cuts, because the length of the OD is 2032 x pi = 6383 mm and the ID is 2000 x pi = 6283. So the ID is about 100 mm shorter, which is 33 cuts.

Does that seem right?

Ah never mind, he’s changed how he wants to do it now.
Thanks for playing.

Spiny Norman said:

Got a mate that’s building a fan shroud for a nightclub.
The ID of the ring is 2000 mm, he’s using 16 mm thick MDF wood to make the ring so the OD will be 2032 mm.
He wants to know how many cuts with a 3mm thick blade he has to make to make the wood flexible though to curve enough to make a ring shape.
I reckon it’s 33 cuts, because the length of the OD is 2032 x pi = 6383 mm and the ID is 2000 x pi = 6283. So the ID is about 100 mm shorter, which is 33 cuts.

Does that seem right?

33 and one third. ;)

Spiny Norman said:

Got a mate that’s building a fan shroud for a nightclub.
The ID of the ring is 2000 mm, he’s using 16 mm thick MDF wood to make the ring so the OD will be 2032 mm.
He wants to know how many cuts with a 3mm thick blade he has to make to make the wood flexible though to curve enough to make a ring shape.
I reckon it’s 33 cuts, because the length of the OD is 2032 x pi = 6383 mm and the ID is 2000 x pi = 6283. So the ID is about 100 mm shorter, which is 33 cuts.

Does that seem right?

No,
to get anything close to circular you would need to kerf MDF at around every 20mm , then cut to correct length .
If you kerf 33 times , it will be every 200mm or so . It will not be round . It will be a tetratriacontagon (yeah looked it up )
Plus timber blades come in 2.4,2.8,3.0, and 3.2 mm (plus many other specialty sizes ) But of those four 3.0mm is the least common .
I know useless info ……
Brett

Thomo said:

Spiny Norman said:

Got a mate that’s building a fan shroud for a nightclub.
The ID of the ring is 2000 mm, he’s using 16 mm thick MDF wood to make the ring so the OD will be 2032 mm.
He wants to know how many cuts with a 3mm thick blade he has to make to make the wood flexible though to curve enough to make a ring shape.
I reckon it’s 33 cuts, because the length of the OD is 2032 x pi = 6383 mm and the ID is 2000 x pi = 6283. So the ID is about 100 mm shorter, which is 33 cuts.

Does that seem right?

No,
to get anything close to circular you would need to kerf MDF at around every 20mm , then cut to correct length .
If you kerf 33 times , it will be every 200mm or so . It will not be round . It will be a tetratriacontagon (yeah looked it up )
Plus timber blades come in 2.4,2.8,3.0, and 3.2 mm (plus many other specialty sizes ) But of those four 3.0mm is the least common .
I know useless info ……
Brett

Not useless, I had not ever used the word tetratriacontagon in a sentence beforehand.

Spiny Norman said:

Ah never mind, he’s changed how he wants to do it now.
Thanks for playing.

No worries.

Spiny Norman said:

Got a mate that’s building a fan shroud for a nightclub.
The ID of the ring is 2000 mm, he’s using 16 mm thick MDF wood to make the ring so the OD will be 2032 mm.
He wants to know how many cuts with a 3mm thick blade he has to make to make the wood flexible though to curve enough to make a ring shape.
I reckon it’s 33 cuts, because the length of the OD is 2032 x pi = 6383 mm and the ID is 2000 x pi = 6283. So the ID is about 100 mm shorter, which is 33 cuts.

Does that seem right?

So this is all sorted?

dv said:

Spiny Norman said:

Got a mate that’s building a fan shroud for a nightclub.
The ID of the ring is 2000 mm, he’s using 16 mm thick MDF wood to make the ring so the OD will be 2032 mm.
He wants to know how many cuts with a 3mm thick blade he has to make to make the wood flexible though to curve enough to make a ring shape.
I reckon it’s 33 cuts, because the length of the OD is 2032 x pi = 6383 mm and the ID is 2000 x pi = 6283. So the ID is about 100 mm shorter, which is 33 cuts.

Does that seem right?

So this is all sorted?

Yep, I went over there to have a look.
He wanted to have the inner end of the slot pretty much closed-up so there was no real gap in the slots, and I worked out that the top of the milling cutter would have to be about 1mm diameter – that’s 12 mm up from the bottom of the cutter – and the bottom would have to be about 0.5 mm diameter. We couldn’t immediately find any in his stash nor on-line and in any case with such a small cutter you’d have to have a pretty slow feed rate.
Anyway after looking at it all I told him he was over-thinking it and to just make cuts every 20 mm or so with the plain 3mm diameter cutter. So it uses a bit more glue to fill the slots, no big deal.

Spiny Norman said:

dv said:

Spiny Norman said:

Got a mate that’s building a fan shroud for a nightclub.
The ID of the ring is 2000 mm, he’s using 16 mm thick MDF wood to make the ring so the OD will be 2032 mm.
He wants to know how many cuts with a 3mm thick blade he has to make to make the wood flexible though to curve enough to make a ring shape.
I reckon it’s 33 cuts, because the length of the OD is 2032 x pi = 6383 mm and the ID is 2000 x pi = 6283. So the ID is about 100 mm shorter, which is 33 cuts.

Does that seem right?

So this is all sorted?

Yep, I went over there to have a look.
He wanted to have the inner end of the slot pretty much closed-up so there was no real gap in the slots, and I worked out that the top of the milling cutter would have to be about 1mm diameter – that’s 12 mm up from the bottom of the cutter – and the bottom would have to be about 0.5 mm diameter. We couldn’t immediately find any in his stash nor on-line and in any case with such a small cutter you’d have to have a pretty slow feed rate.
Anyway after looking at it all I told him he was over-thinking it and to just make cuts every 20 mm or so with the plain 3mm diameter cutter. So it uses a bit more glue to fill the slots, no big deal.

I made a curved two step construction like this. Blackbutt curved riser panel. 3mm saw blade. cut every about 10mm in 15mm board. down to about 3mm of the edge.

If your kerfing every 20 or so I would try a thinner cut first not a 3 . Im thinking a 1mm would do the job .
Brett

Thomo said:

If your kerfing every 20 or so I would try a thinner cut first not a 3 . Im thinking a 1mm would do the job .
Brett

I did mention that.

Great minds think alike .

Fools rarely differ .

:)

Brett

Just as a side note .
Your talking about a lot of cuts .
You want to take MDF dust seriously .

Brett

Thomo said:

Just as a side note .
Your talking about a lot of cuts .
You want to take MDF dust seriously .

Brett

I am indeed – I’m now about 5 km away from the machine. :)