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Posted by rodjava on November 21, 2008, 11:23 am
Please log in for more thread options
Hi fellow home shop machinists,
Can somebody please refer me to a link on how to accurately grind 60
degree lathe bits. Consistancy is what I'm looking for. I need to
grind several single cut threading bits from blanks.
I currently hand grind. Now that I have a hand held microscope, I now
know that my points are not true 60 degrees when matched to a fish
tail guage.
I'm not threading for aerospace, but would like to acheive a perfect
60 degree point if possible.
Thank you in advance,
Rod
San Francisco
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Posted by rodjava on November 21, 2008, 11:25 am
Please log in for more thread options
> Hi fellow home shop machinists,
> Can somebody please refer me to a link on how to accurately grind 60
> degree lathe bits. =A0Consistancy is what I'm looking for. =A0I need to
> grind several single cut threading bits from blanks.
>
> I currently hand grind. Now that I have a hand held microscope, I now
> know that my points are not true 60 degrees when matched to a fish
> tail guage.
>
> I'm not threading for aerospace, but would like to acheive a perfect
> 60 degree point if possible.
>
> Thank you in advance,
>
> Rod
> San Francisco
I forgot to mention that I'm using a standard pedastal grinder.
Rod
San Francisco
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Posted by Bruce in Bangkok on November 21, 2008, 11:50 am
Please log in for more thread options On Fri, 21 Nov 2008 08:25:45 -0800 (PST), rodjava
>> Hi fellow home shop machinists,
>> Can somebody please refer me to a link on how to accurately grind 60
>> degree lathe bits. Consistancy is what I'm looking for. I need to
>> grind several single cut threading bits from blanks.
>>
>> I currently hand grind. Now that I have a hand held microscope, I now
>> know that my points are not true 60 degrees when matched to a fish
>> tail guage.
>>
>> I'm not threading for aerospace, but would like to acheive a perfect
>> 60 degree point if possible.
>>
>> Thank you in advance,
>>
>> Rod
>> San Francisco
>
>I forgot to mention that I'm using a standard pedastal grinder.
>
>Rod
>San Francisco
Look up "center gage".
"L.S. STARRETT" SPRING STEEL CENTER GAUGES
Extremely handy for use in grinding and setting screw cutting
tools. Has a table of double depths of threads for determining size of
tap drills. Made of spring-tempered steel with satin chrome finish.
Gaging surfaces ground. Number of threads per inch scale. American
Unified National Standard, 60°
Cheers,
Bruce
(bruceinbangkokatgmaildotcom)
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Posted by Jim Wilkins on November 21, 2008, 11:58 am
Please log in for more thread options wrote:
...
I never studied solid geometry. In an angle fixture, if I rotate the
bit say 5 degrees for side relief, how do I refigure the 30 degree end
angle?
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Posted by Bruce in Bangkok on November 21, 2008, 7:59 pm
Please log in for more thread options On Fri, 21 Nov 2008 08:58:06 -0800 (PST), Jim Wilkins
>wrote:
>...
>
>I never studied solid geometry. In an angle fixture, if I rotate the
>bit say 5 degrees for side relief, how do I refigure the 30 degree end
>angle?
Not sure what you are asking but the usual procedure for cutting
threads is to grind a tool bit to a 60 deg. point with normal side and
end relief. If you want side rake then grind it as once the sides are
ground changing the top surface doesn't change the side angles.
The tool is then set with the center line of the tool at right angles
to the surface being threaded. The compound is set to 30 deg., or very
slightly less.
Using the cross feed the tool is advanced until the tip of the bit
just touches the work. Either a threading stop is then set or, more
usually, the cross feed dial is set to zero.
Feeding the tool into the work is then done by use of the compound
while the cross feed is used only to retract the tool between cuts.
The zero setting on the cross feed dial, or the threading stop, makes
it easy to return to your base setting.
As tool feed is done at 30 deg. to the work surface it means that the
threading tool cuts only on the forward edge resulting in a smoother
cut.
Setting the compound to slightly less then 30 deg. means that as the
tool is advanced by the compound the path is not exactly parallel to
the rear edge of the tool resulting in a very light, scraping, cut
being taken by the rear edge of the tool bit. Some argue that it
results in a smoother thread.
Cheers,
Bruce
(bruceinbangkokatgmaildotcom)
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> Can somebody please refer me to a link on how to accurately grind 60
> degree lathe bits. =A0Consistancy is what I'm looking for. =A0I need to
> grind several single cut threading bits from blanks.
>
> I currently hand grind. Now that I have a hand held microscope, I now
> know that my points are not true 60 degrees when matched to a fish
> tail guage.
>
> I'm not threading for aerospace, but would like to acheive a perfect
> 60 degree point if possible.
>
> Thank you in advance,
>
> Rod
> San Francisco