G4003g Cutting 1.0 Mm Threads Help Please

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Dman1114

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So i need to cut some M28 x 1mm threads for an adaptor i am making.

Long story short they cut close but its not right. I checked it with my gauges and its closer to 27 TPI than 1.0 mm....

not perfect 27 TPI but its a lot closer than 1mm

I change over to a 26 top gear and have the 60 on the bottom. it says any middle gear combo so I'm good there.


I have it set at position B - 5.... but no dice....

Threads looks great they just are not spaced properly.


Anyone have any suggestions? Why can't i cut a 1mm thread? I cut 1.25 and 1.5 all the time and never have an issue.

Thanks in advance
 
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Make sure that the 26 and 60 teeth gears are both meshing on the same gear between them, not like in the bottom of the metric threading chart where the upper and lower gears are meshing with different tooth counts in the middle. If that is correct, get back to us.
 
So 26-86-60 B5 will cut .9456mm or 26.86 TPI which is probably what you have.
26-91-60 B5 will cut 1.0006mm or 25.385TPI
Closer still:
35-86-60 B8 = 1.0002mm
40-86-40 C6 = 1.0002mm
40-86-60 C1 = 1.0002mm
45-86-60 C2 = 1.0002mm
50-86-60 C4 = 1.0002mm

Hope one of these will work for you.
Dave
 
Is the 91t gear inside? on my 4003g lathe the 91t was on the outside When trying to cut metric threads I could not get them to cut correct either until i changed the 86/91 gear around putting the 91t gear to the inside then I was able to cut the correct thread pitch. Don't know why but it works now. I was thinking that when the chart said any gear it would work with any gear but it did not until I changed them around. don't know why but it works now. The whole metric chart is a little confusing to my old ADD ADHD brain:confused:
Tomh
 
Bob, dave I do believe you guys Nailed it ...

I got it done.... I found a chart http://www.truetex.com/grizzly-12x36-pitch.htm and after reading over all the variables i realized that i had the 26 t and the 60t on opposite idlers.... (even though the Grizzly Chart says "ANY" WTF!!!)

Maybe I'm misinterpreting the ANY ... it should say "either or but not both"

so instead of flopping the bottom gear i just changed the top to a 35 and went B - 8. worked like a Champ. and was closer than the other one. Guess i can't trust the stupid Grizzly chart.



Thanks guys for the imput.
 
OHH and this chart i found is actually really easy cause it tells you what gear goes on what idler. No confusing BS like "ANY"

im gonna print it out and hang it in the shop

http://www.truetex.com/grizzly-12x36-pitch.htm

I was making and part and one side had 28 x 1mm and the other had 1/2 x 20 threads....

wish i looked the chart over would of saved me time having to flip over the idle and swap all the gears.... could of just change the upper....


Ohhh well guess i learned something knew today
 
Below is a pic of the Metric Thread chart on my G4003G. It can be pretty confusing, but here is how I interpret it.

G4003GThreadChart.jpg

For a pitch of 1.0 mm, one should use the 26 tooth for gear F and the 60 tooth for gear G. The diagram shows both the F and G gears are meshed with the same gear, the inboard gear. The chart says that any gear can be used for this inboard gear, which makes sense, because this one gear will not change the ratio. Finally, choose positions B5 on the levers for a 1.0mm pitch.

Bob
 
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