In a message dated 18/10/05, charles.r.patton@........ writes:

> Chris,
> Your're right -- apparently frames or some such. So, anyway, got to 
> McMaster-Carrs site http://www.mcmaster.com/ and enter :
> 91800A087 in the "FIND" box for the screws
> 91828A006 in the "FIND" box for the nuts

Hi Charles,

       Thanks. Sorry for the slow response.

       Found them OK, but what size of seismometer are you thinking about?

       The screws are 1.2 mm OD = 0.047" and the length is 10 mm = 0.394"

> I know Angel and others are talking about micrometers for leveling screws 
> -- but any micrometer I'm familiar with only has 40 TPI, not a lot better than 
> a 10/32 screw, and the screw is a lot cheaper, that's why I suggested some 
> of the metric screws with 0.25 pitch (101.6 TPI).  The laser adjustment screws 
> are generally in the 80 TPI range with some in the 100 TPI class, but they 
> are generally $20 or more, while the metric screws can be put together for a 
> 

       For light apparatus I can use SS Socket Cap 4 mm OD with a 2.5 mm 
ball, which is 36.3 TPI and max 1.38" long. For Lehmans and the like, I use 6 mm 
OD with a 5 mm ball, which is 25.4 TPI and max 1.97" long. McMaster do not seem 
to stock either lengths in SS. The big ++ so far as I am concerned is that 
you can cover a small hole in the top of your Celotex box with sticky tape and 
use this to intoduce a hex driver to adjust the levelling screws. I keep the 
tension in the mounting bolt using a second nut on the top of the baseplate and 
wavy washer. This effectively removes any 'slop' in the threads.

       The A2 grade SS range of socket caps can be centre drilled in the end 
with a carbide bit and some oil. I made myself a couple of centre locating 
attachments. In a lathe, I drilled a small central hole in a short length of hex 
bar to match the pilot of a centre drill. Then I drilled and blind tapped the 
other end to 4 or 6mm. I clamp the bolt vertically, screw on the centring 
tube, start the pilot hole using the centre drill, remove the centring tube and 
finish boring to get a 90 deg cone to hold the ball.

        However as I mentioned in a previous note, you can get rotating ball 
end and swivel end socket cap screws for McMC. You can also buy a range of 
'thumb screws'.

      I also buy zinc plated mild steel 6 mm set screws / bolts up to 60 mm 
long. (or 1/4" by 2.1/2" long.) These are very convenient for mounting the two 
1/4" mild steel backing plates for a quad NdFeB variable magnetic damping 
attachment, using three nuts with each screw. Being mild steel, they 'short out' 
most of any stray field due to the powerful magnets.

       Regards,

       Chris Chapman
In a message=20=
dated 18/10/05, charles.r.patton@........ writes:



Chris,

Your're right -- apparently frames or some such. So, anyway, got to=20

McMaster-Carrs site http://www.mcmaster.com/ and enter :

91800A087 in the "FIND" box for the screws

91828A006 in the "FIND" box for the nuts




Hi Charles,



       Thanks. Sorry for the slow response=
.



       Found them OK, but what size of sei=
smometer are you thinking about?



       The screws are 1.2 mm OD =3D 0.047"=
 and the length is 10 mm =3D 0.394"



I know Angel and others are=
 talking about micrometers for leveling screws -- but any micrometer I'm fam=
iliar with only has 40 TPI, not a lot better than a 10/32 screw, and the scr=
ew is a lot cheaper, that's why I suggested some of the metric screws with 0=
..25 pitch (101.6 TPI).  The laser adjustment screws are generally in th=
e 80 TPI range with some in the 100 TPI class, but they are generally $20 or=
 more, while the metric screws can be put together for a dollar or two.



       For light apparatus I can use SS So=
cket Cap 4 mm OD with a 2.5 mm ball, which is 36.3 TPI and max 1.38" long. F=
or Lehmans and the like, I use 6 mm OD with a 5 mm ball, which is 25.4 TPI a=
nd max 1.97" long. McMaster do not seem to stock either lengths in SS. The b=
ig ++ so far as I am concerned is that you can cover a small hole in the top=
 of your Celotex box with sticky tape and use this to intoduce a hex driver=20=
to adjust the levelling screws. I keep the tension in the mounting bolt usin=
g a second nut on the top of the baseplate and wavy washer. This effectively=
 removes any 'slop' in the threads.



       The A2 grade SS range of socket cap=
s can be centre drilled in the end with a carbide bit and some oil. I made m=
yself a couple of centre locating attachments. In a lathe, I drilled a small=
 central hole in a short length of hex bar to match the pilot of a centre dr=
ill. Then I drilled and blind tapped the other end to 4 or 6mm. I clamp the=20=
bolt vertically, screw on the centring tube, start the pilot hole using the=20=
centre drill, remove the centring tube and finish boring to get a 90 deg con=
e to hold the ball.



        However as I mentioned in a p=
revious note, you can get rotating ball end and swivel end socket cap screws=
 for McMC. You can also buy a range of 'thumb screws'.



      I also buy zinc plated mild steel 6 mm se=
t screws / bolts up to 60 mm long. (or 1/4" by 2.1/2" long.) These are very=20=
convenient for mounting the two 1/4" mild steel backing plates for a quad Nd=
FeB variable magnetic damping attachment, using three nuts with each screw.=20=
Being mild steel, they 'short out' most of any stray field due to the powerf=
ul magnets.



       Regards,



       Chris Chapman