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Posted by MikeH_QB on March 7, 2008, 5:59 am
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I've got a bar around 20mm square and 90mm long.
I want it reasonably parallel along its length. I dont have a mill, so
it need to be done in the 4-jaw of the lathe.
Set it in the chuck, skim the first side. Turn it around, new 'flat'
side against chuck jaws, skim to final size determined by how i've set
my carriage stop. No problem.
So, now I have 2 reasonably parallel edges at the correct distance
apart.
I now need to get the third side skimmed and parallel. I can't just
rely on putting side #4 against the chuck as this is unmachined yet. I
don't have any true reference edge to put a DTI against, so how do I
achieve true squareness? Once edge #3 is skimmed, the final side can
be skimmed to the appropriate size via the stop.
How do I then avoid ending up with a 'traqezoid' form. This particular
job is not super critical in itself, its just a thought that came to
me when planning to do it?
Have I missed the bl**ding obvious somewhere?
Regards
Mike
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Posted by dave sanderson on March 7, 2008, 7:15 am
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> I've got a bar around 20mm square and 90mm long.
> I want it reasonably parallel along its length. I dont have a mill, so
> it need to be done in the 4-jaw of the lathe.
> Set it in the chuck, skim the first side. Turn it around, new 'flat'
> side against chuck jaws, skim to final size determined by how i've set
> my carriage stop. No problem.
>
> So, now I have 2 reasonably parallel edges at the correct distance
> apart.
> I now need to get the third side skimmed and parallel. I can't just
> rely on putting side #4 against the chuck as this is unmachined yet. I
> don't have any true reference edge to put a DTI against, so how do I
> achieve true squareness? Once edge #3 is skimmed, the final side can
> be skimmed to the appropriate size via the stop.
>
> How do I then avoid ending up with a 'traqezoid' form. This particular
> job is not super critical in itself, its just a thought that came to
> me when planning to do it?
> Have I missed the bl**ding obvious somewhere?
> Regards
> Mike
use a faceplate and one or more angle plates to clamp the bar on its
machined sides at 90 degrees to the faceplate. you could skim the
faceplate lightly to be sure of flatness, but probably not required.
Dave
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Posted by MikeH_QB on March 7, 2008, 7:44 am
Please log in for more thread options wrote:
>
>
>
>
>
> > I've got a bar around 20mm square and 90mm long.
> > I want it reasonably parallel along its length. I dont have a mill, so
> > it need to be done in the 4-jaw of the lathe.
> > Set it in the chuck, skim the first side. Turn it around, new 'flat'
> > side against chuck jaws, skim to final size determined by how i've set
> > my carriage stop. No problem.
>
> > So, now I have 2 reasonably parallel edges at the correct distance
> > apart.
> > I now need to get the third side skimmed and parallel. I can't just
> > rely on putting side #4 against the chuck as this is unmachined yet. I
> > don't have any true reference edge to put a DTI against, so how do I
> > achieve true squareness? Once edge #3 is skimmed, the final side can
> > be skimmed to the appropriate size via the stop.
>
> > How do I then avoid ending up with a 'traqezoid' form. This particular
> > job is not super critical in itself, its just a thought that came to
> > me when planning to do it?
> > Have I missed the bl**ding obvious somewhere?
> > Regards
> > Mike
>
> use a faceplate and one or more angle plates to clamp the bar on its
> machined sides at 90 degrees to the faceplate. you could skim the
> faceplate lightly to be sure of flatness, but probably not required.
>
> Dave- Hide quoted text -
>
> - Show quoted text -
Its only 20mm square to start with, so won't have a lot of clamping
area. It would need to be at the 'top' of any faceplate and still
don't have an accurate reference edge to determine (in this case) when
both ends are exactly the same distance from the face plate. If not,
just as with using the chuck, I risk getting a bar thats perfectly
square in section, but with a 'taper', if you get my drift.
This seems something that should be such a common task that I feel it
must be dead obvious, it just doesn't seem to be. Still, good exercise
for the old grey-matter!
regards
Mike
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Posted by _ on March 7, 2008, 10:28 am
Please log in for more thread options On Fri, 7 Mar 2008 04:44:24 -0800 (PST), MikeH_QB wrote:
> wrote:
>>
>>
>>
>>
>>
>>> I've got a bar around 20mm square and 90mm long.
>>> I want it reasonably parallel along its length. I dont have a mill, so
>>> it need to be done in the 4-jaw of the lathe.
>>> Set it in the chuck, skim the first side. Turn it around, new 'flat'
>>> side against chuck jaws, skim to final size determined by how i've set
>>> my carriage stop. No problem.
>>
>>> So, now I have 2 reasonably parallel edges at the correct distance
>>> apart.
>>> I now need to get the third side skimmed and parallel. I can't just
>>> rely on putting side #4 against the chuck as this is unmachined yet. I
>>> don't have any true reference edge to put a DTI against, so how do I
>>> achieve true squareness? Once edge #3 is skimmed, the final side can
>>> be skimmed to the appropriate size via the stop.
>>
>>> How do I then avoid ending up with a 'traqezoid' form. This particular
>>> job is not super critical in itself, its just a thought that came to
>>> me when planning to do it?
>>> Have I missed the bl**ding obvious somewhere?
>>> Regards
>>> Mike
>>
>> use a faceplate and one or more angle plates to clamp the bar on its
>> machined sides at 90 degrees to the faceplate. you could skim the
>> faceplate lightly to be sure of flatness, but probably not required.
>>
>> Dave- Hide quoted text -
>>
>> - Show quoted text -
>
> Its only 20mm square to start with, so won't have a lot of clamping
> area. It would need to be at the 'top' of any faceplate and still
> don't have an accurate reference edge to determine (in this case) when
> both ends are exactly the same distance from the face plate. If not,
> just as with using the chuck, I risk getting a bar thats perfectly
> square in section, but with a 'taper', if you get my drift.
>
> This seems something that should be such a common task that I feel it
> must be dead obvious, it just doesn't seem to be. Still, good exercise
> for the old grey-matter!
> regards
> Mike
Can you live with three holes through it (crossways)?
One for a bolt, two for dowel pins, bolt and pin it to the angle plate.
Skim, reverse and skim to desired thickness.
To make sure your holes are perpendicular, bore them on the faceplate.
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Posted by dave sanderson on March 7, 2008, 10:46 am
Please log in for more thread options > wrote:
>
>
>
>
> > > I've got a bar around 20mm square and 90mm long.
> > > I want it reasonably parallel along its length. I dont have a mill, so
> > > it need to be done in the 4-jaw of the lathe.
> > > Set it in the chuck, skim the first side. Turn it around, new 'flat'
> > > side against chuck jaws, skim to final size determined by how i've set
> > > my carriage stop. No problem.
>
> > > So, now I have 2 reasonably parallel edges at the correct distance
> > > apart.
> > > I now need to get the third side skimmed and parallel. I can't just
> > > rely on putting side #4 against the chuck as this is unmachined yet. I
> > > don't have any true reference edge to put a DTI against, so how do I
> > > achieve true squareness? Once edge #3 is skimmed, the final side can
> > > be skimmed to the appropriate size via the stop.
>
> > > How do I then avoid ending up with a 'traqezoid' form. This particular
> > > job is not super critical in itself, its just a thought that came to
> > > me when planning to do it?
> > > Have I missed the bl**ding obvious somewhere?
> > > Regards
> > > Mike
>
> > use a faceplate and one or more angle plates to clamp the bar on its
> > machined sides at 90 degrees to the faceplate. you could skim the
> > faceplate lightly to be sure of flatness, but probably not required.
>
> > Dave- Hide quoted text -
>
> > - Show quoted text -
>
> Its only 20mm square to start with, so won't have a lot of clamping
> area. It would need to be at the 'top' of any faceplate and still
> don't have an accurate reference edge to determine (in this case) when
> both ends are exactly the same distance from the face plate. If not,
> just as with using the chuck, I risk getting a bar thats perfectly
> square in section, but with a 'taper', if you get my drift.
>
> This seems something that should be such a common task that I feel it
> must be dead obvious, it just doesn't seem to be. Still, good exercise
> for the old grey-matter!
> regards
> Mike
both ends exatly the same distance from the face plate is not
important.
square to the sides is. as long as your not massively out then bolt to
top of
angle plate, set approximately square to faceplate. skim.
then reverse and use 2 lengths of tube or similar that you bolt to the
face plate
from behind. skim these in situ so they are the same length. then
place face 3
on them, with face 1 on the angle plate, clamp and face off face 4
until at the
desired thickness. you will end up with the 4 long faces square to
each other.
(the ends are a different matter)
Dave
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> I want it reasonably parallel along its length. I dont have a mill, so
> it need to be done in the 4-jaw of the lathe.
> Set it in the chuck, skim the first side. Turn it around, new 'flat'
> side against chuck jaws, skim to final size determined by how i've set
> my carriage stop. No problem.
>
> So, now I have 2 reasonably parallel edges at the correct distance
> apart.
> I now need to get the third side skimmed and parallel. I can't just
> rely on putting side #4 against the chuck as this is unmachined yet. I
> don't have any true reference edge to put a DTI against, so how do I
> achieve true squareness? Once edge #3 is skimmed, the final side can
> be skimmed to the appropriate size via the stop.
>
> How do I then avoid ending up with a 'traqezoid' form. This particular
> job is not super critical in itself, its just a thought that came to
> me when planning to do it?
> Have I missed the bl**ding obvious somewhere?
> Regards
> Mike