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Posted by Alan Bain on May 15, 2008, 4:34 pm
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In the process of making Watch screws (14BA and smaller) from carbon
steel, I have been experimenting with slitting them. Normally I use a
screw head file, but this can be somewhat time consuming so I tried a
slitting saw in the lathe. I mount the screw in a tapped brass block
clamped to the vertical slide and run in gently at centre height to the
slitting saw.
This sort of arrangement I find works well when making larger screws
(4BA and larger), but with a 8 thou slitting saw and slow backgear
performance was somewhat hit and miss; sometimes a beautiful slot was cut,
other times the slot was very Vee shaped with ragged torn edges and
in one case the slitting saw lost a tooth (but the screw was undamaged)!
I have a feeling that this may be because I am using a cutter
of too coarse a pitch (the finest saw I could find had a tooth spacing
greater that the diameter of my screw head and normally I try to ensure
that at least two teeth are in contact with the work. I should
be interested to know if this is a plausible explanation?
Alan
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Posted by dave sanderson on May 15, 2008, 4:48 pm
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> In the process of making Watch screws (14BA and smaller) from carbon
> steel, I have been experimenting with slitting them. Normally I use a
> screw head file, but this can be somewhat time consuming so I tried a
> slitting saw in the lathe. I mount the screw in a tapped brass block
> clamped to the vertical slide and run in gently at centre height to the
> slitting saw.
>
> This sort of arrangement I find works well when making larger screws
> (4BA and larger), but with a 8 thou slitting saw and slow backgear
> performance was somewhat hit and miss; sometimes a beautiful slot was cut,
> other times the slot was very Vee shaped with ragged torn edges and
> in one case the slitting saw lost a tooth (but the screw was undamaged)!
>
> I have a feeling that this may be because I am using a cutter
> of too coarse a pitch (the finest saw I could find had a tooth spacing
> greater that the diameter of my screw head and normally I try to ensure
> that at least two teeth are in contact with the work. I should
> be interested to know if this is a plausible explanation?
>
> Alan
sounds plausible to me, IIRC when selecting a hacksaw / pierceing saw
blade the
guidance on TPI is to select one which will keep 3 teeth in the cut. I
guess slitting
saw blades would be similar.
Have you thought of using dremel / clone cutting disks? Im not sure
how thick they are,
but might be able to thin them a bit anyway.
Dave
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Posted by Peter Fairbrother on May 15, 2008, 6:39 pm
Please log in for more thread options Alan Bain wrote:
> In the process of making Watch screws (14BA and smaller) from carbon
> steel, I have been experimenting with slitting them. Normally I use a
> screw head file, but this can be somewhat time consuming so I tried a
> slitting saw in the lathe. I mount the screw in a tapped brass block
> clamped to the vertical slide and run in gently at centre height to the
> slitting saw.
>
> This sort of arrangement I find works well when making larger screws
> (4BA and larger), but with a 8 thou slitting saw and slow backgear
> performance was somewhat hit and miss; sometimes a beautiful slot was cut,
> other times the slot was very Vee shaped with ragged torn edges and
> in one case the slitting saw lost a tooth (but the screw was undamaged)!
>
> I have a feeling that this may be because I am using a cutter
> of too coarse a pitch (the finest saw I could find had a tooth spacing
> greater that the diameter of my screw head and normally I try to ensure
> that at least two teeth are in contact with the work. I should
> be interested to know if this is a plausible explanation?
Yes, very plausible. Three teeth is standard.
http://cgi.ebay.co.uk/4-Diamond-QUALITY-Lapidary-Saw-Blade-1-2-Hole-20mm_W0QQitemZ300203774152QQihZ020QQcategoryZ4843QQcmdZViewItemQQ_trksidZp1742.m153.l1262
-- Peter Fairbrother
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Posted by Peter Fairbrother on May 15, 2008, 7:37 pm
Please log in for more thread options Alan Bain wrote:
> In the process of making Watch screws (14BA and smaller) from carbon
> steel, I have been experimenting with slitting them. Normally I use a
> screw head file, but this can be somewhat time consuming so I tried a
> slitting saw in the lathe. I mount the screw in a tapped brass block
> clamped to the vertical slide and run in gently at centre height to the
> slitting saw.
>
> This sort of arrangement I find works well when making larger screws
> (4BA and larger), but with a 8 thou slitting saw and slow backgear
Backgear? Why? What dia is the saw? The center height of the lathe?
> performance was somewhat hit and miss; sometimes a beautiful slot was cut,
> other times the slot was very Vee shaped with ragged torn edges and
> in one case the slitting saw lost a tooth (but the screw was undamaged)!
>
> I have a feeling that this may be because I am using a cutter
> of too coarse a pitch (the finest saw I could find had a tooth spacing
> greater that the diameter of my screw head and normally I try to ensure
> that at least two teeth are in contact with the work.
something smaller than my last suggestion:
http://www.jlindustrial.co.uk/CGI/INSRCH?ns=1&oldNtt=&oldNtk=&oldURLVar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scrNtt=0.008&x=25&y=15&Ntk=Keyword+Search&withinResults=true
but the teeth are still 1.5 mm apart.
-- Peter Fairbrother
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Posted by Cliff Coggin on May 16, 2008, 3:59 am
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> Alan Bain wrote:
>> In the process of making Watch screws (14BA and smaller) from carbon
>> steel, I have been experimenting with slitting them. Normally I use a
>> screw head file, but this can be somewhat time consuming so I tried a
>> slitting saw in the lathe. I mount the screw in a tapped brass block
>> clamped to the vertical slide and run in gently at centre height to the
>> slitting saw.
>>
>> This sort of arrangement I find works well when making larger screws
>> (4BA and larger), but with a 8 thou slitting saw and slow backgear
>
> Backgear? Why? What dia is the saw? The center height of the lathe?
>
>> performance was somewhat hit and miss; sometimes a beautiful slot was
>> cut,
>> other times the slot was very Vee shaped with ragged torn edges and
>> in one case the slitting saw lost a tooth (but the screw was undamaged)!
>>
>> I have a feeling that this may be because I am using a cutter
>> of too coarse a pitch (the finest saw I could find had a tooth spacing
>> greater that the diameter of my screw head and normally I try to ensure
>> that at least two teeth are in contact with the work.
>
> something smaller than my last suggestion:
>
http://www.jlindustrial.co.uk/CGI/INSRCH?ns=1&oldNtt=&oldNtk=&oldURLVar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scrNtt=0.008&x=25&y=15&Ntk=Keyword+Search&withinResults=true
>
> but the teeth are still 1.5 mm apart.
>
> -- Peter Fairbrother
There are 1" diamond slitting discs on 2 mm arbors available. I don't have
access to mine at the moment so I can't give a thickness, but it is far
thinner than the Dremmel type of resin-bonded slitting disc.
Cliff Coggin.
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> steel, I have been experimenting with slitting them. Normally I use a
> screw head file, but this can be somewhat time consuming so I tried a
> slitting saw in the lathe. I mount the screw in a tapped brass block
> clamped to the vertical slide and run in gently at centre height to the
> slitting saw.
>
> This sort of arrangement I find works well when making larger screws
> (4BA and larger), but with a 8 thou slitting saw and slow backgear
> performance was somewhat hit and miss; sometimes a beautiful slot was cut,
> other times the slot was very Vee shaped with ragged torn edges and
> in one case the slitting saw lost a tooth (but the screw was undamaged)!
>
> I have a feeling that this may be because I am using a cutter
> of too coarse a pitch (the finest saw I could find had a tooth spacing
> greater that the diameter of my screw head and normally I try to ensure
> that at least two teeth are in contact with the work. I should
> be interested to know if this is a plausible explanation?
>
> Alan