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Small grooves - advice / suggestions please!

 

I need to make some fine grooves, in aluminium or stainless (304).
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I'm making a very simple lap steel guitar, and this is for the nut - the piece just below the tuners that the strings pass over, at the end of the fingerboard.
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The strings are the following thickness:
?
inches?????? mm
0.012 ? ? ?? 0.30
0.016 ? ???? 0.41
0.024 ? ???? 0.61
0.032 ? ???? 0.81
0.044 ? ???? 1.12
0.056 ? ???? 1.42
?
Ideally the string should sit in a semi-circular groove (the same size, halfway in) but I don't think this will be possible.? A flat bottomed or 45 degree sided groove is more likely.
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Specialist luthiers nut files are too expensive for a one-off job. One suggestion I have seen is to grind down hacksaw blades on a bench grinder to the correct thickness.
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It would be good to use the Unimat though. An angled (chamfering) end mill might just do the larger sizes but I doubt the point is very fine on them to make the smallest grooves. I see that ball nose end mills go down to 1mm.
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You folks know a lot more about what's available and (more importantly) what is likely to work! - what would you suggest?? I'm in the UK by the way.
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Many thanks!
 

Peter, have a look for these like in the image I don't remember where I got them but they screw onto a 6mm shank that fits in the Unimat I have done some small cuts like what you want and this insert worked well for me, you should be able to cut all your sizes although they would be a V cut.
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Hope it helps.
Phill
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The simplest thing is just to make the grooves with either a square or
three-square needle file. As you file deeper the groove will widen.
Since you're doing it in stainless there's no worry that the string will
significantly distort the groove, so having perfect semi-circular
grooves is not an issue.
Get a good quality Swiss-pattern needle file from a jeweler's supply
house. I suggest #4 cut as this will leave a nicer finish.
If you're not in a city with a large jewelry industry there are several
suppliers with good websites. Here's one:


On 3/27/25 2:54 PM, Peter Brooks via groups.io wrote:
I need to make some fine grooves, in aluminium or stainless (304).
I'm making a very simple lap steel guitar, and this is for the nut - the
piece just below the tuners that the strings pass over, at the end of
the fingerboard.
The strings are the following thickness:
inches?????? mm
0.012 ? ? ?? 0.30
0.016 ? ???? 0.41
0.024 ? ???? 0.61
0.032 ? ???? 0.81
0.044 ? ???? 1.12
0.056 ? ???? 1.42
Ideally the string should sit in a semi-circular groove (the same size,
halfway in) but I don't think this will be possible.? A flat bottomed or
45 degree sided groove is more likely.
Specialist luthiers nut files are too expensive for a one-off job. One
suggestion I have seen is to grind down hacksaw blades on a bench
grinder to the correct thickness.
It would be good to use the Unimat though. An angled (chamfering) end
mill might just do the larger sizes but I doubt the point is very fine
on them to make the smallest grooves. I see that ball nose end mills go
down to 1mm.
You folks know a lot more about what's available and (more importantly)
what is likely to work! - what would you suggest?? I'm in the UK by the way.
Many thanks!
--
Elliot Nesterman
elliot@...
www.ajoure.net

"Remember, if women don't find you handsome they should at least find
you handy."
 

On Thu, Mar 27, 2025 at 06:54 PM, Peter Brooks wrote:
I see that ball nose end mills go down to 1mm.
Ball nose cutters are available from 0.2 to 1.0 mm in 0.1 mm steps, see Ebay:
?
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A sharp bottomed 90¡ã groove will hold any size string. If you take a small flat needle file and make sure the safety edge is really flat by honing it down you can file a very sharp groove and ease it out one side at a time until it is just the depth you need. Cutting with a square or triangular (three square) file always leaves a radius in the groove, generally bigger than your finest string gauge. The honed edge of a flat file gives a very sharp corner - and doing this also improves the file for many other jobs too.
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I feel that cutting the groove to exactly the same width as the string is a mistake - what happens if you can't get just the same gauge of string one day?
 

Thanks Phil.? The 'nut' will be a piece of angle, so I'm planning to use the milling attachment.
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The 'bridge' will be a piece of brass rod though, and something like this would work well. I have 6mm shank that takes the 60 degree (triangular) replaceable cutters, I might look for one with 45 degree cutters.
 

Thanks Elliot, good suggestion. I'm thinking now that I will use the milling attachment, and can set up a dial indicator to get the exact spacing between the strings (rather wide at 11mm).
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I do like to find specialist stores though with good quality items, jewellery suppliers is a great idea.
 

Thanks Keith - your link led me to investigate engraving bits, I'm going to try some of these.
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As I mentioned above I'm hoping I can get more than adequate spacing precision using the U3 milling attachment and an indicator.
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The 'nut' will be a piece of angle attached by three screws to the body, so easily replaced if plans (or string diameters) change. Strings can be bought in sets, or singly, so I don't think they will become unavailable.
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Great tip on improving a flat file though!
 

I have cut long vee grooves in aluminium using 90¡ã pointed burrs, and I found they needed some lubrication - I used car screenwash, as I had some handy. The problem is that at the point the surface speed approaches zero, so it clogs up. In other work engraving plastics we found the milling cutters are better than single edge engravers on acetal, but the single edge cutters worked much better on rigid PVC. The milling cutters melted the PVC, which then jammed everything up and broke the cutter. So it might help t have a choice of cutter types.
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Regarding string spacing, i used to think about the space between adjacent strings, which is the gap left to get your fingers in, so I widened the spacing towards the basses, taking into account the thicker strings. I applied that particularly to a six string electric bass I made many years ago. The neck proportions and string spacing were based on typical classical guitars. It worked very well.
 

Anther option for fine grooves is to use a piercing saw - the blades go down to very thin, and are never very thick. The problem then is controlling the depth, but I favour having a top fret, so the nut sets the string spacing and the fret sets the string height.
 

Those looking for guitar nut and saddle files check out Stewmac @.
On the same page on line they have a number of other files used in lutherie.
Hope this link proves useful to all.
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Bill in NC
 

Hi Phil,
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I'm in need of a tool holder similar to yours.? Could you let me know where you purchased it?? I have purchased the carbide inserts but can't locate a tool holder to use with them!
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Regards,
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Myron
 

Hi Myron,
I forgot where I got them but my wife came to the rescue my niece in Canada picked them up for me:? Tassocut.? ?Regards Phill?image.png



Sent with secure email.

On Sunday, 30 March 2025 at 03:13, vital.spark via groups.io <vital.spark@...> wrote:

Hi Phil,
?
I'm in need of a tool holder similar to yours.? Could you let me know where you purchased it?? I have purchased the carbide inserts but can't locate a tool holder to use with them!
?
Regards,
?
Myron
 

Thanks Phil!?

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