If one was to use a thread mill in a manner consistent with milling, the
resulting surface would look much like a gear rack...having maybe 8
peaks or so...the reason for a thread mill to have so many
teeth(typically a function of engineering data for a "so many turns to
equal a solid connection" on the fact that deeper threads does not mean
a better hold)..moving onward. thread mills are not supposed to cut
from the top down. They are designed to be inserted into the hole first
then helically moved into the side, then a full revolution around and
up, then similar retraction. That is how the hole keeps from being recut
by the teeth further up on the tool. Thread milling can be performed by
a single toothed cutter, however that would take a lot of time to
perform, and in some cases with larger thread forms is the case. Its
loud and the first time I used one it really scared me a bit.
Just try not to think of them as taps, they do not work the same.
They are not designed to form the thread top to bottom, but to form it
as quickly as possible. Only way to do that is to get down in there and
go at it in 3 small moves. To make the left hand version of a thread the
rotation of the helical paths is reversed or its started with the last
tooth at the top of the hole and and worked one revolution down to the
bottom(climb/conventional)
|>
|> would take 2 sets of passes to make a 6 thread hole
|> just think of the tool as a cut directly through a tapped
hole looking at .001 or so degree
wise arc of the outer circle. IE mill one half of a
tapped hole off so you can look into the
threads from the side.
I hope this has helped some
Phil
Mark Wendt (Contractor) wrote:
> At 01:11 PM 5/20/2008, you wrote:
>
>> Mark Wendt (Contractor) wrote:
>>
>>> Trying to wrap my mind around this tool. One of the bullet points says
>>> that only one tool needed for right or left hand threads. Howdeydodat?
>>>
>> It is not like a tap, it has no thread lead. All the teeth are
>> in rings. The tricks is it only touches the OD in one line
>> along the length of the hole. It can do EXTERNAL threads the
>> same way, you orbit around the OD of a post and it will thread
>> the outside. The spindle needs to extend or retract in synch
>> with the rotation of the orbit to develop the correct thread pitch.
>>
>> Jon
>>
>
> I think I have a grasp of how this thing works now. My only question
> left is, if the "teeth" are in rings, and there are multiple rings
> (and assuming the thread mill is spinning at that same time as the x
> and y axes are moving), how does the tool keep from munging the
> threads that are already cut if there is no "screw" ramp to
> them? From the looks of the thread mill in the picture, the thread
> mill's "rings" all seem to be parallel with each other, and have no screw
> ramp.
>
> Mark
>
>
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