Hole Size?

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1,554
Terrible thread title I know... but can I ask what diameter hole should be drilled out in order to snugly fit a 23mm knot?

Thanks
 
It really isn't as simple as that.


All knots are different
Some knots have a "hard base" extending several millimetres above the top of the plug. If set deeper than their natural loft, then they need to be set in a hole that is at least 2mm larger in diameter, sometimes more.

OK... many folks say to set the loft of your knot at 45mm to 50mm.
I am going to show you that there is a problem.

#1 rule : Always make the hole for the knot size and loft that you want to end up with.
In other words, start with the particular knot you are using, and make the hole fit IT

#2 rule: All knots are different. Which is why we obey rule #1

I am going to provide you with an illustration.
Here we have two "22mm" brush knots. (from different sources)
Both have the same total height (66mm), both have the same plug depth (8mm).

One (A) has a plug diameter of 22.5mm - that isn't going to even fit into your 22mm bored hole in the handle
The other (B) has a plug diameter of 21.5mm - that will fit into your 22mm bored hole.

BUT
(see, that is a very big BUT, and its in red too)

sizes-22mm.jpg


If you want to end up with a loft of 50mm, then your hole needs to be 16mm deep.
And THAT is where you will run into trouble.

I measured the diameter of those two knots at the 16mm depth, with the hairs squashed in the digital calipers as tight as they would go. In other words.... the diameter that your hole would need to be.

Brush A: 25mm
Brush B: 22.9mm (let's say 23mm)
Sometimes the answer may be to bore a stepped hole for the knot.

Now, the total height of your knot may be different. But the same principles apply!

Rod
 
I wonder if this applies to a plan I had in mind for the future. I have a Muhle limited edition xl silvertip which has a knot of 25mm. I was thinking of eventually buying one of their 25mm synthetic knots to convert it. The handles look to be the same size but now I'm thinking that it will not be such a simple job. :s

Chris.
 
Fido said:
I'd sell the silvertip and put the money towards the new brush!

I think I will as I've decided it's too big for me. Does all this hole fiddling also apply to synthetic knots? I've noticed that the Muhle knots look like they are set quite high in the handle.
 
Just apply the 2mm rule as it's unlikely the synthetic knot will be overstuffed and if it is you can adjust the loft accordingly.

If you're going for a straight swap do measure the knot hole first, if it's 25mm buy a 23mm knot and so on, no idea why Mule synths are set high perhaps they are particularly stiff.
 
antdad said:
no idea why Mule synths are set high perhaps they are particularly stiff.

I have one sat in front of me and from a quick feel test against one of the silver tips I use, I'd say there isn't much in it, if anything slightly less stiff. They do come with a 14mm deep spacer already fitted which automatically gives a 2mm clearance, presumably for manufacturing expediency.
 
Err I feel a bit of a muppit now... I've just finished my first brush and according to what I've just read I've dropped a testicle. I made mine with an interference fit and only slightly deeper than the plug. DOE.......:mad:
 
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