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Model Engineering in UK - Model engineering, metal crafts in UK
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Posted by Mike D on February 13, 2007, 4:13 am
Please log in for more thread options
: quoted-printable
Many thanks for all the helpful advice
I tried John's Homebrew, it was much better but I am still unhappy with =
the results
The taps were new via tracy tools
the results give an oversize fixing
2 further questions Please
1 where do you get the other type of tap john mentioned?
2 how should the metal be heat treated?
mike
Please can I pick your assembled brains
I am finishing off making a Hemingway fixed steady for my MYFORD 7 and =
this involves tapping the finger adjustors in the aluminium casting for =
a quarter whit cap screw.
I am far from happy with the results in that the new taps did not cut =
cleanly leaving an ill formed thread and a floppy fixing. The metal =
just seems to tear
I used 3 in 1 oil as a lubricant and firstly tried a taper tap and =
secondly a second tap which gave a marginally better result. The =
casting was about 3/8 thick. I had a similar result on a thin piece of =
alum. plate with a 5 mm tap Last week and had to resort to using mild =
steel. The results using these taps on steel was fine and as to be =
expected.
I used the recommended size 20 drill and used thin oil and RTD grease =
as a lubricant.at different times
I can't believe everybody has these dire results and perhaps someone can =
suggest what I'm doing wrong please
Mike
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<DIV>Many thanks for all the helpful advice</DIV>
<DIV>I tried John's Homebrew, it was much better but I am still unhappy =
with the=20
results</DIV>
<DIV>The taps were new via tracy tools</DIV>
<DIV>the results give an oversize fixing</DIV>
<DIV>2 further questions Please</DIV>
<DIV> </DIV>
<DIV>1 where do you get the other type of tap john =
mentioned?</DIV>
<DIV>2 how should the metal be heat treated?</DIV>
<DIV> </DIV>
<DIV>mike</DIV>
<DIV> </DIV>
<DIV> </DIV>
<DIV> </DIV>
<DIV> </DIV>
<DIV> </DIV>
<DIV> </DIV>
<DIV> </DIV>
<DIV> </DIV>
<DIV> </DIV>
<DIV> </DIV>
<DIV> </DIV>
<DIV> </DIV>
<DIV> </DIV>
<DIV>"Mike D" <<A=20
wrote in=20
message <A=20
$n36.27074@newsfe7-gui.ntli.net</A>...</DIV>
<DIV>Please can I pick your assembled brains</DIV>
<DIV> </DIV>
<DIV>I am finishing off making a Hemingway fixed steady for my MYFORD 7 =
and this=20
involves tapping the finger adjustors in the aluminium casting for a =
quarter=20
whit cap screw.</DIV>
<DIV> </DIV>
<DIV>I am far from happy with the results in that the new taps did not =
cut=20
cleanly leaving an ill formed thread and a floppy fixing. The =
metal=20
just seems to tear</DIV>
<DIV> </DIV>
<DIV>I used 3 in 1 oil as a lubricant and firstly tried a=20
taper tap and secondly a second tap which =
gave a=20
marginally better result. The casting was about =
3/8 thick. I=20
had a similar result on a thin piece of alum. plate with a 5 mm tap =
Last=20
week and had to resort to using mild steel. The results using =
these taps=20
on steel was fine and as to be expected.</DIV>
<DIV> </DIV>
<DIV>I used the recommended size 20 drill and used thin =
oil and=20
RTD grease as a lubricant.at different times</DIV>
<DIV> </DIV>
<DIV>I can't believe everybody has these dire results and perhaps =
someone can=20
suggest what I'm doing wrong please</DIV>
<DIV> </DIV>
<DIV>Mike</DIV></BODY></HTML>
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Posted by stooby-doo on February 13, 2007, 1:20 pm
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> 1 where do you get the other type of tap john mentioned?
J&L industrial supply,
http://catalogs.shoplocal.com/jlindustrial/index.aspx?storeid=1039181&circularid=7330&jlpass=112&firstname=&lastname=&loggedin=false&itemcount=0&mode=test&pagenumber=112
or just search for 'thread forming'
Stu G
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Posted by Dave Baker on February 13, 2007, 5:13 pm
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Many thanks for all the helpful advice
I tried John's Homebrew, it was much better but I am still unhappy with the
results
The taps were new via tracy tools
the results give an oversize fixing
2 further questions Please
1 where do you get the other type of tap john mentioned?
2 how should the metal be heat treated?
mike
Sounds as though the taps are no good. It's best to stick to known brands
like Dormer, Blue Point etc. If you live anywhere near Slough there's a
little shop in Farnham Common called Sert Tools which has boxes of hundreds
of second hand taps, many as new, for a quid or so each. Most of my stock
has come from there. If that's not an option then J&L online as has already
been suggested.
Aluminium heat treatment will be done at the factory. It's not something you
can do yourself.
You seem to be posting in html. If you could stick to plain text it would be
appreciated.
--
The internet. It's not a big truck.
It's a series of tubes.
Dave Baker
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Posted by Mike D on February 14, 2007, 3:30 am
Please log in for more thread options Thanks for the extra info
Mike
ps think I have killed html now
Many thanks for all the helpful advice
I tried John's Homebrew, it was much better but I am still unhappy with the
results
The taps were new via tracy tools
the results give an oversize fixing
2 further questions Please
1 where do you get the other type of tap john mentioned?
2 how should the metal be heat treated?
mike
Please can I pick your assembled brains
I am finishing off making a Hemingway fixed steady for my MYFORD 7 and this
involves tapping the finger adjustors in the aluminium casting for a quarter
whit cap screw.
I am far from happy with the results in that the new taps did not cut
cleanly leaving an ill formed thread and a floppy fixing. The metal just
seems to tear
I used 3 in 1 oil as a lubricant and firstly tried a taper tap and
secondly a second tap which gave a marginally better result. The casting
was about 3/8 thick. I had a similar result on a thin piece of alum. plate
with a 5 mm tap Last week and had to resort to using mild steel. The
results using these taps on steel was fine and as to be expected.
I used the recommended size 20 drill and used thin oil and RTD grease as
a lubricant.at different times
I can't believe everybody has these dire results and perhaps someone can
suggest what I'm doing wrong please
Mike
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Posted by John Stevenson on February 14, 2007, 3:58 am
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>Thanks for the extra info
>Mike
>ps think I have killed html now
>Many thanks for all the helpful advice
>I tried John's Homebrew, it was much better but I am still unhappy with the
>results
>The taps were new via tracy tools
>the results give an oversize fixing
>2 further questions Please
>
>1 where do you get the other type of tap john mentioned?
>2 how should the metal be heat treated?
>
>mike
>
>
Mike,
The advised tapping drill for materials is selected to give about an 80 % thread
engagement ratio.
this is chosen for ease of tapping and to relieve tap breakage but still give a
decent
thread.
Quarter Whit tables tell us tat the effective diameter is 0.218 but minor
diameter is
0.186 which matches the fact that the depth of thread [ one side ] is 0.032
Now a No 20 drill is 0.160, way below the minor diameter.
So it could be that the taper part of your tap is having to ream out material
first and so
'stretching' the pitch because of the work it has to do, leading to a loose
thread?
Try using a 3/16" drill as this is bang on size but in soft material will
probably cut a
tad big.
>
>
>
>Please can I pick your assembled brains
>
>I am finishing off making a Hemingway fixed steady for my MYFORD 7 and this
>involves tapping the finger adjustors in the aluminium casting for a quarter
>whit cap screw.
>
>I am far from happy with the results in that the new taps did not cut
>cleanly leaving an ill formed thread and a floppy fixing. The metal just
>seems to tear
>
>I used 3 in 1 oil as a lubricant and firstly tried a taper tap and
>secondly a second tap which gave a marginally better result. The casting
>was about 3/8 thick. I had a similar result on a thin piece of alum. plate
>with a 5 mm tap Last week and had to resort to using mild steel. The
>results using these taps on steel was fine and as to be expected.
>
>I used the recommended size 20 drill and used thin oil and RTD grease as
>a lubricant.at different times
>
>I can't believe everybody has these dire results and perhaps someone can
>suggest what I'm doing wrong please
>
>Mike
>
--
Regards,
John Stevenson
Nottingham, England.
Visit the new Model Engineering adverts page at:-
http://www.homeworkshop.org.uk/
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