8.5x .75 tap and die sets

[mredburn]

Im am getting quotes on the 8.5 x .75 single thread tap and die sets.

I believe these would be of great use when making fountain pens for the front section. It would allow you to drill a 7.9 or 8mm hole for the tap and that would allow you to pass a convertor through the hole.

Your body to cap threads would be 10mm and the inner threads will be 8.5 mm.

Would that be useful to us or would 8x.6 be better?

 

[hewunch]

What is the thread for the bock feeds (big)?

 

[MrWright]

You know Mike, I think it would be good for a 8.5x.75 as you can you them in doing most of the pen. So, I vote what you have indicated.

 

[mredburn]

The large Bock is 7.9 x.6
I also considered the 8.5 x .5 but its a very fine thread. It would be good for metal but im not sure it would work well on any other materials.

 

[BigShed]

Mike, as some of us already own the 8.4x1 tap for the Jr Gent II/Baron section, perhaps a die to match that thread would be better?

Those of us that already have the tap would then only have to buy the die.

We would then have a matching tap/die set to match an existing kit size.

The 8.4x1 works quite well as a thread size for a section, as evidenced by its' use in the Jr Gent/Baron kit.

Or do you see a particular advantage for the finer 0.75mm pitch?

PS The Sierra transmission also uses the 8.4x1mm thread.

 

[mredburn]

Fred
I gave that a lot of thought before the 8.5 x.75. Because I have them also. But would the 8.4 x1 require a drill hole size of at least 7.6mm? or .299. The converters Im measuring are going to need a .310 hole minimum. If I recall We had to drill a hole larger than the standard " subtract the pitch from the diameter" rule of thumb. .310 is 7.9mm. This is why I want to discuss it here. I have a quote but I am holding off ordering to see if we can nail down a solid reason one way or the other.

 

[BigShed]

Fred
I gave that a lot of thought before the 8.5 x.75. Because I have them also. But would the 8.4 x1 require a drill hole size of at least 7.6mm? or .299. The converters Im measuring are going to need a .310 hole minimum. If I recall We had to drill a hole larger than the standard " subtract the pitch from the diameter" rule of thumb. .310 is 7.9mm. This is why I want to discuss it here. I have a quote but I am holding off ordering to see if we can nail down a solid reason one way or the other.

Mike, just measured the Schmidt converters supplied with the Jr Gent II kits and they are 7.64mm maximum.

Got out my sample female threaded PR piece for the 8.4x1 tap and it passes thorugh there quite easily.

When I get some time I will do a deeper test piece that has some unthreaded part as well and see how I go.

Will get back to you.

 

[mredburn]

Fred the converters I have are 7.82, they are not the kit ones. They are the ones that are sold individully by Indy Pen dance Exotics and others.

 

[BigShed]

Fred the converters I have are 7.82, they are not the kit ones. They are the ones that are sold individully by Indy Pen dance Exotics and others.

OK, that changes things. BTW the Schmidt converters are also available individually from several suppliers, eg BTW here, they also have a cheaper version, here, but I don't know what size they are. I find it is sometimes cheaper to buy the kits and use the parts from them rather than buy the parts individually. I do that routinely for my bullet pens.

Just for the record I have just done 2 tests with the 8.4x1 tap and 2 different drills. Both are oversize for the theoretical drill size for this tap which is 7.4mm. I hardly ever use the theorectical drill size preferring to go slightly oversize to make for an easier thread engagement.

Anyway, first test was using an "M" size drill, which is .2950" or 7.5mm

Good engagement of the section thread, but wouldn't allow the Schmidt converter in to the unthreaded part.

Second test was with an "N" size drill, which is .3020 or 7.7mm.

Still good engagement of the section thread and Schmidt converter goes easily in to the unthreaded part.

Neither of course would handle the IDP converters, don't know what brand they are. They appear somewhat thick for this size pen though.

 

[Texatdurango]

Mike, I don't believe I would be interested in this size tap and die.

I currently make my sections with 9mm x .75mm threads going into the pen body.

To me, the diameter of the converter isn't as important than the .250" diameter of the converter tip which goes up inside the section body.

As it is, the wall thickness when cutting 9 x .75 threads then drilling the .250" hole for the converter to fit snugly inside is fairly thin. I don't think I would want to make the wall any thinner since this is actually the weakest point of the whole section and the point that will get the most stress when the user is pushing the converter in to snap it into the feed nipple. I think the thinner wall around the threads will result in some easily broken sections.

Just an opinion.

 

[mredburn]

The 8.4 or 8.5 would have its primary use in pens with cap threads using the m10 x,75 either triple lead or single. In those pens a 9x.75 inside a 10x.75 would mean the threads of both would have to be cut parallel with each other and at best they would only be .5mm thick. It is getting down to splitting hairs as it is, and it would have to be done in metal to hold. I dont believe that resins would be able to hold at all. If your using 11mm or larger cap threads then the m9x.75 or m10 x.75 or 1 become a better choice. There are quite a few Heritance taps at 8.4x.75 and the 8.4x1 taps out there already it would be nice to have a die that would lend them to another use.
the 8.4 x 1 probably would have been better off at 8.5 x 1 to start with.