Jar thread TO63

[alhussien]

hi guys
i am asking if i can make this jar thread on 3 axis vertical milling machine with 4th axis rotary table?
itry to make it on fixed vise but it is not completed machines coz i the tool cant reach to some areas.
anyone know how to make it on inventor cam or powermill by using 4th axis .
thanks guys

 

[Dan from Oakland]

Model it as any other multi-start female thread. Your model looks to have duplicated the male thread where it starts and stops. The female thread leads can be continous and still mate with the male thread.

 

[alhussien]

Model it as any other multi-start female thread. Your model looks to have duplicated the male thread where it starts and stops. The female thread leads can be continous and still mate with the male thread.

i thought about that but i cant write the right multi start thread cycle for it .
FYI. the one start have three leads . it is not only one thread lead for each start . it is three leads .
please check my attached file for more detail about that thread .

 

[implmex]

Hi alhussien:
Why do you believe you need a fourth axis for this part?
This looks like a pretty typical neck plate for a bottle mould.
We used to make a custom flycutter and swing these on a standard VMC with no issues whatsoever.
The flycutter is simply a single tooth saw, and you run it exactly like you'd run any other threadmill.

Cheers

Marcus
www.implant-mechanix.com
www.vancouverwireedm.com

 

[alhussien]

Hi alhussien:
Why do you believe you need a fourth axis for this part?
This looks like a pretty typical neck plate for a bottle mould.
We used to make a custom flycutter and swing these on a standard VMC with no issues whatsoever.
The flycutter is simply a single tooth saw, and you run it exactly like you'd run any other threadmill.

Cheers

Marcus
www.implant-mechanix.com
www.vancouverwireedm.com

so i need to form a T-cutter with tooth geomtry same as the thread profile . like this one in my attachments

 

[alhussien]

Hi alhussien:
Why do you believe you need a fourth axis for this part?
This looks like a pretty typical neck plate for a bottle mould.
We used to make a custom flycutter and swing these on a standard VMC with no issues whatsoever.
The flycutter is simply a single tooth saw, and you run it exactly like you'd run any other threadmill.

Cheers

Marcus
www.implant-mechanix.com
www.vancouverwireedm.com

just keep in mind that the tool must have an inclination angle during cutting the thread . and i cant get it through 3 axis vertical milling machine

 

[implmex]

Hi again alhussien:
Yes, it's technically true that you need the spindle to be inclined to the helix angle of the thread which would mean a 5 axis machine or a 3 axis machine with a 4th axis tilted to the helix angle.

However, the practical reality is that it's a jar top thread...the tolerances are typically really liberal on those and just about every 80's era mold maker who has built bottle molds has done hundreds with nothing more than a hand ground bit in a die grinder mounted in the toolpost of a manual lathe with felt pen marks on the chuck and a piece of masking tape to tell him where to start and stop the thread(s).

Tens of thousands more have been done on VMC's with zero effort made to tilt the plane of the saw into the helix of the thread.

Yeah, it's not correct, but often it does not matter enough to worry about.
Make the cutter as small as possible and you will minimize the impact of doing it incorrectly, and model the threadform to accommodate the helix angle mismatch, and you may well be just fine.

If it's a mold for a glass jar, the fidelity of the molded thread will be crappy anyway, and if it's a plastic blowmold the same will apply.
Only if it's injection blow will the thread be pretty close in form to the mold cavity.

I leave it to you, to sort out if it's worth the bother of tilting the neck plate on the rotary or on a 5 axis mill.

Cheers

Marcus
www.implant-mechanix.com
www.vancouerwireedm.com

 

[Dan from Oakland]

Keep your cutter diameter as small as possible and you might well be able to mill it with the cutter spindle parallel to the thread axis. As Marcus mentioned, model the cutter tooth profile in the the transverse plane not in a plane normal to the thread lead.

 

[alhussien]

Hi again alhussien:
Yes, it's technically true that you need the spindle to be inclined to the helix angle of the thread which would mean a 5 axis machine or a 3 axis machine with a 4th axis tilted to the helix angle.

However, the practical reality is that it's a jar top thread...the tolerances are typically really liberal on those and just about every 80's era mold maker who has built bottle molds has done hundreds with nothing more than a hand ground bit in a die grinder mounted in the toolpost of a manual lathe with felt pen marks on the chuck and a piece of masking tape to tell him where to start and stop the thread(s).

Tens of thousands more have been done on VMC's with zero effort made to tilt the plane of the saw into the helix of the thread.

Yeah, it's not correct, but often it does not matter enough to worry about.
Make the cutter as small as possible and you will minimize the impact of doing it incorrectly, and model the threadform to accommodate the helix angle mismatch, and you may well be just fine.

If it's a mold for a glass jar, the fidelity of the molded thread will be crappy anyway, and if it's a plastic blowmold the same will apply.
Only if it's injection blow will the thread be pretty close in form to the mold cavity.

I leave it to you, to sort out if it's worth the bother of tilting the neck plate on the rotary or on a 5 axis mill.

Cheers

Marcus
www.implant-mechanix.com
www.vancouerwireedm.com

thanks . it was really useful Discussion.
i will use the flycutter with small diameter as possible as i can
many thanks

 

[alhussien]

Keep your cutter diameter as small as possible and you might well be able to mill it with the cutter spindle parallel to the thread axis. As Marcus mentioned, model the cutter tooth profile in the the transverse plane not in a plane normal to the thread lead.

i will try it and i will write back here the results . thanks