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Model Engineering in UK - Model engineering, metal crafts in UK
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Posted by ravensworth2674 on March 6, 2008, 8:36 am
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Derek,
It doesn't work like that. You should be going to
Schlesinger's limits which will explain lead screw testing- and a lot
more tests on parts which make up final accuracy in machine tools.
I apologise but I am not trying to be rude or anything like that. It
is the famous- or infamous- adding incorrect dimensions which don't
even work in two dimensions or three.
Unquestionably, such concepts are far too detailed to be listed here.
Norman
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Posted by Austin Shackles on March 8, 2008, 4:50 am
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On or around Thu, 6 Mar 2008 05:36:44 -0800 (PST), ravensworth2674
>Derek,
> It doesn't work like that. You should be going to
>Schlesinger's limits which will explain lead screw testing- and a lot
>more tests on parts which make up final accuracy in machine tools.
>
>I apologise but I am not trying to be rude or anything like that. It
>is the famous- or infamous- adding incorrect dimensions which don't
>even work in two dimensions or three.
>
>Unquestionably, such concepts are far too detailed to be listed here.
For what I use the machine for, it's possible to work around most of the
wear issues, anyway. Now that I've done the split nut mod on the leadscrew
nut, it's a bit better behaved.
Currently, the cross-slide is a touch too slack (feed and ways) in the
middle and a bit tight (again, feed and ways) at the extreme end towards the
operator; if you like, it's optimised for turning small items 'cos that's
what I mostly do. If I had a need to do significant amounts of work on a
large diameter, I could re-adjust the gibs in the cross slide and get more
freedom at that point, at the cost of having it a bit slack near the middle.
--
Austin Shackles. www.ddol-las.net my opinions are just that
Travel The Galaxy! Meet Fascinating Life Forms...
------------------------------------------------
>> http://www.schlockmercenary.com/ << ...and Kill them.
a webcartoon by Howard Tayler; I like it, maybe you will too!
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Posted by ravensworth2674 on March 8, 2008, 7:25 am
Please log in for more thread options Austin,
I haven't seen your cross slide but I can understand wear
in the screw in its middle but I would question wear in the middle of
the cross slide itself.
If this is so, you would have the rear bit unworn because the gib is
the wearing/working face but the front edge bears against the male
front apron edge.
Logically, you should have original scrape marks at the front of your
cross slide but wear in the middle.
Forgive me but I am being pedantic on your behalf.
With a decent ruler and a bit of blue, you should be able to offer the
rule moving it, perhaps half an inch to find what you claim is a
hollow. You haven't said that but it is implied.
Well now?
Cheers
Norman
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Posted by Austin Shackles on March 9, 2008, 11:59 am
Please log in for more thread options On or around Sat, 8 Mar 2008 04:25:08 -0800 (PST), ravensworth2674
>Austin,
> I haven't seen your cross slide but I can understand wear
>in the screw in its middle but I would question wear in the middle of
>the cross slide itself.
>If this is so, you would have the rear bit unworn because the gib is
>the wearing/working face but the front edge bears against the male
>front apron edge.
>Logically, you should have original scrape marks at the front of your
>cross slide but wear in the middle.
>
>Forgive me but I am being pedantic on your behalf.
>
>With a decent ruler and a bit of blue, you should be able to offer the
>rule moving it, perhaps half an inch to find what you claim is a
>hollow. You haven't said that but it is implied.
>Well now?
I dare say I could, but it's a lot of hassle to get it "right" and all the
time it works "OK" I intend to live with it.
The facts are that if adjusted so that there's no play with the cross-slide
where it would be to turn something (say) up to about 3" dia., then it gets
increasingly stiffer as you move it further towards the operator. If you
adjust it so that it's free to move but with no discernible play when wound
most of the way out (i.e. turning something and more or less max. diameter)
then it has play when moved to a position near the centre.
I've not invesigated which parts (slide, saddle, gibs(2), etc.) is actually
worn, although logic says it should be the saddle to give that effect, since
the gibs can be adjusted to take up wear.
despite that there are 2 gibs, I suspect the rear one doesn't do a lot
unless using a rear toolpost.
--
Austin Shackles. www.ddol-las.net my opinions are just that
Travel The Galaxy! Meet Fascinating Life Forms...
------------------------------------------------
>> http://www.schlockmercenary.com/ << ...and Kill them.
a webcartoon by Howard Tayler; I like it, maybe you will too!
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Posted by Tim Leech on March 10, 2008, 5:18 am
Please log in for more thread options On Sun, 09 Mar 2008 15:59:48 +0000, Austin Shackles
>On or around Sat, 8 Mar 2008 04:25:08 -0800 (PST), ravensworth2674
>
>>Austin,
>> I haven't seen your cross slide but I can understand wear
>>in the screw in its middle but I would question wear in the middle of
>>the cross slide itself.
>>If this is so, you would have the rear bit unworn because the gib is
>>the wearing/working face but the front edge bears against the male
>>front apron edge.
>>Logically, you should have original scrape marks at the front of your
>>cross slide but wear in the middle.
>>
>>Forgive me but I am being pedantic on your behalf.
>>
>>With a decent ruler and a bit of blue, you should be able to offer the
>>rule moving it, perhaps half an inch to find what you claim is a
>>hollow. You haven't said that but it is implied.
>>Well now?
>
>I dare say I could, but it's a lot of hassle to get it "right" and all the
>time it works "OK" I intend to live with it.
>
>The facts are that if adjusted so that there's no play with the cross-slide
>where it would be to turn something (say) up to about 3" dia., then it gets
>increasingly stiffer as you move it further towards the operator. If you
>adjust it so that it's free to move but with no discernible play when wound
>most of the way out (i.e. turning something and more or less max. diameter)
>then it has play when moved to a position near the centre.
>
Sounds just like my DSG <g>
The cross slide gib was worn unevenly, the slide clamping screw works
on the centre of the gib & it's probably been run with the clamp
nipped up instead of adjusting the gib properly. I've surface ground
the gib and packed it, beyond that I intend to live with the wear for
the time being.
Tim
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> It doesn't work like that. You should be going to
>Schlesinger's limits which will explain lead screw testing- and a lot
>more tests on parts which make up final accuracy in machine tools.
>
>I apologise but I am not trying to be rude or anything like that. It
>is the famous- or infamous- adding incorrect dimensions which don't
>even work in two dimensions or three.
>
>Unquestionably, such concepts are far too detailed to be listed here.