Threads and gear conversion chart

[tailoredpencompany]

You do not need two 120 gears, it just means you use the same 120 gear to connect the 40 to 32. Or for that matter the same 127 gear.

That makes total sense. Sorry my brain is fried right now as I’m dealing with a water tank that flooded my basement and I’m frazzled. Sorry.

 

[tailoredpencompany]

Quick Change thread and feed gearbox.

Ah yes, it is.

 

[Rodneyk]

My error, I have the calculation sheet for imperial and there is a gear combination for 50 TPI.
Levers D 4
40 -> 120
120 -> 32

I was looking for this a while back (the chart), Thanks it will come in handy in the future...
It would be cool to have this in an excel sheet or even just a text file.

 

[brino]

Why on earth would this vintage pen company have used 50 tpi. Crazy company I say.

Some companies did this so that you would have to return to them for replacement parts.
Maybe not so crazy.....

Brian

 

[silverhawk]

Check that the thread is actually not multi point threaded, which is a higher pitch, but not a deep thread.

Sent from my SM-T500 using Tapatalk

 

[Ischgl99]

Silverhawk brings up a good point, many pens use multistart threads, so it might be a more standard thread pitch that has multiple threads. Have you checked the lead to see how much it threads in per turn? 50TPI is also very close to 0.5mm, is there a chance this could be metric?

 

[tailoredpencompany]

Some companies did this so that you would have to return to them for replacement parts.

Maybe not so crazy.....

Brian

Hey Brian, thanks for the suggestion. It’s a single start. I love multi start threads but for sections, it’s never done. I shouldn’t say that, I occasionally do it on larger pens to reduce the need turns to seat the section to the body. But thanks, I did check it after you mentioned it and it’s single start.

 

[tailoredpencompany]

My error, I have the calculation sheet for imperial and there is a gear combination for 50 TPI.
Levers D 4
40 -> 120
120 -> 32

Not sure what I’m doing wrong but that setting isn’t working. That’s giving me 30TPI.

 

[Ischgl99]

Not sure what I’m doing wrong but that setting isn’t working. That’s giving me 30TPI.

The calculations are backwards, you need to do 32-120-40 on D4 and that should give you 50 TPI. The way you have the gears set up will speed up the leadscrew, you need to slow it down.

 

[Ken226]

Is that the same spreadsheet as the one @Just for fun used, from this thread?

Post in thread '11.5 TPI' https://www.hobby-machinist.com/threads/11-5-tpi.101904/post-981438