Jinhao x750 barrel tap size?

[mikedealer]

Does anyone have a tap size for a Jinhao x750?

 

[apple320]

I am thinking a 7/16 x 36

 

[QuoVadis]

I was wondering this also. I bought a couple of these to try out and couldn't believe how nice feeling they were compared to the one I bought at a big box stop recently for 5xs as much. I started thinking I could just use the section and nib off the jinhao to start going kit less and it would save more money than buying nibs and sections elsewhere. I just needed to figure out the threading. Surely I'm not the first to consider doing this. Someone tell me what I'm missing.

 

[mikedealer]

I am thinking a 7/16 x 36

I'm a little thick when it comes to tap sizes etc. but wouldn't a Chinese product be in metric? Unless the fraction is an exact equivalent

 

[budnder]

Maybe M10 x 0.7?

36 TPI seems right for the x750 I have, but 7/16 seems too big. I'll attach some pics...

I tried screwing my own 10 x .75 section into an x750 barrel and it screwed in but felt a bit loose. When I tried to screw a x750 nib into my 10 x .75 barrel it started and went maybe one revolution and then got tight.

So I'm thinking M10 x 0.7?

 

[frank123]

Tap to m10 x .7 and give it a try. I think this might work.

You may need to make a tap, taps for plastics and soft material are easy enough to make if you have access to a metal lathe ( I usually just make them out of simple cold roll mild steel bar when they are intended for plastic, they don't need hardening).

 

[More4dan]

Tap to m10 x .7 and give it a try. I think this might work.

You may need to make a tap, taps for plastics and soft material are easy enough to make if you have access to a metal lathe ( I usually just make them out of simple cold roll mild steel bar when they are intended for plastic, they don't need hardening).

I use either W1 or O1Tool steel (drill rod). See this link: http://www.penturners.org/forum/f166/making-your-own-specialty-taps-bock-5-mm-139755/

You can also use a bolt with the ends ground for soft material.

 

[frank123]

I use either W1 or O1Tool steel (drill rod). See this link: http://www.penturners.org/forum/f166/making-your-own-specialty-taps-bock-5-mm-139755/

You can also use a bolt with the ends ground for soft material.

Yeah, I usually use higher carbon or alloy stuff for anything that is to be used on harder materials or that needs to last for extensive use, but for limited use or testing use (particularly by someone with limited experience) mild steel works just fine. In between drill rods that need hardening and mild steel that is only good for plastics would fall alloys like 4140 prehard which is readily attainable and easily worked with carbide tooling if you're cutting standard form factor threads. 4140 will probably never go dull in plastics and is acceptable for soft metals such as aluminum or brass and will give usable service on mild steels and such. Cutting the flutes is what usually is the hardest part (unless you also have a mill) and this is more easily done for something that has limited or single use intended using mild steel than harder carbon steels and alloys.

Alloy bolts (which is what your will find most easily in metric stuff) are fine if you're cutting a standard thread but not if you're cutting something in an unusual diameter or pitch (which pen manufactures seem to have a passion for doing. as in .7 instead of .75 or 6.4 or 6.5 instead of either 6 or 7).

Thread form and pitch is sometimes a problem, Chinese oddball stuff -pen or otherwise- that doesn't have standard pitches and thread forms may take several attempts to get it right. You can use the threads on your part as a guide to get the correct form and depth for your cutter when you grind it, but you may need a decent magnifying glass if your eyes aren't really good. Experimenting with this is where fast and simple cuts in mild steel (or even brass) can be worthwhile since you may toss it after the first try if it doesn't work out.

Grinding a simple V thread cutting tool is pretty easy and is most common, but if you want a square or acme thread or something else outside of the usual you can face a real challenge since you have to grind for the helix angle of the thread as well as the form and allow for relief angles based on that as well.

Overall, making a simple tap no matter the material for use in soft stuff like plastic isn't difficult and doesn't take long, determining exactly what thread can be the harder part of the chore.

But you still need access to a metal lathe with threading capability and the skill to use it. Might not be a bad idea for someone wanting a hobby business to start making them for all the odd sizes found in pens and such, professionally made ones usually cost too much for anyone not intending extensive use from having them made just to try something.

 

[Joey-Nieves]

I am thinking a 7/16 x 36

7/16 x 36 is equivalent to 11.1 x 7

 

[budnder]

I am thinking a 7/16 x 36

7/16 x 36 is equivalent to 11.1 x 7

Which, just to avoid confusion... looks to be the wrong size for the x750 I have - M10 x 0.7 is what I'd try first with mine.

I don't have access to a metal lathe (yet... someday...), but am interested in the possibilities here. Just posting info to help others that do and to document it for posterity. I'll also attach magnified view of the threads in question, if someone wants to see their shape.

 

[duncsuss]

I'll also attach magnified view of the threads in question, if someone wants to see there shape.

Cute!

That looks similar to the (molded) threads on a Noodler's ink freebie -- kind of like a double-start thread which has one of the two intertwined helices stripped out.

 

[frank123]

Looks like a modified "V" thread with a wider and flatter than normal root and crest. Maybe a shallower depth of cut as well. When you're making your own proprietary threading, you can pretty much do it anyway you want and I think this may be at least a partially proprietary thread.

(If you're imitating a proprietary thread that means you will have to make your own cutters and such to match it since taps and dies won't be an off the shelf item. I'm wondering if it could be retreaded to whatever is closest to it using standard dies and taps to make it easier to work with and more universal in application? You only need it to thread on for a few diameters so re-cuts shouldn't present much problem if they're close enough to start with.)

Jinhao pens are fairly inexpensive so it doesn't cost a lot to experiment with them to find out, I think I have one around somewhere that I can sacrifice so I may try this sometime (trouble is that I never seem to want to sacrifice or get rid of anything pen related).

To add, nice photo. Wish my photography didn't stink so much I'm ashamed to post it.

 

[budnder]

Well, re-threading it actually produced something usable.

Since I use 10x.75 for my kitless and have some barrels of that size handy, that's what I re-threaded it to. By re-threading it, I mean I simply put the x750 section into a collet and turned a 10 x .75 die on it. It now screws into my kitless just fine. The x750 section is just a hair bigger in circumference than my custom sections, so my kitless cap is tight on it, but it screws into my 10 x .75 barrel just fine.

This section's days of screwing into an x750 barrel are definitely over - it now slides in without engaging any of the threads.

Attached is a pic with it attached to my kitless and another closeup of the threads (warning... it's ugly what it did to the threads).

 

[frank123]

That's great to know, makes a useful addition to kitless pen making. I like the Jinhao pens for their sections, feeds and nibs -and price- and will probably experiment with them some now.

FWIW, some plumbers silicone grease can make up for lots of small threading irregularities on parts that don't have to be taken apart often.

 

[budnder]

Here's some incentive for harvesting the section of an x750... the "press on" cap works by having the metal ring at the end of the nib pass over a "bump" in a plastic insert that's inside the x750 cap. That insert threads into the finial and is also glued. I was able to knock out the upper part of the finial and then push out that plastic insert and the bottom part of the finial.

I could, in theory, glue that harvested plastic insert into my own cap and then I'd have a "press on" cap for my kitless pen (as long as I was using the x750 section or devised my own equivalent bump ring).

The clip comes out unscathed and looks pretty standard also - definitely reusable. And the converter, I think is standard as well. So lots of parts for a few dollars, and if you buy several at a time, you can even get the shipping down to dirt cheap.

The end cap in the barrel looks like it's brass pressed into the barrel tube. Not sure if the barrel tube is metal or not, but the cap looks to be a metal tube. Another take on what might be possible is to an x750 down to it's metal tubes then turn your own body and cap on those tubes, then put it all back together.

 

[More4dan]

My Homemade fluteless taps have worked great in plastics, brass, and aluminum. They can be made without a mill and are much stronger. You just can't use them to thread to the bottom of blind hole typically not an issue for pens.

 

[QuoVadis]

Roy your last post was very informative. I was curious, instead of rethreading, is it possible to harvest the barrel threads and just glue those into a new turned barrel? So a person could use the barrel threads made for the section, use the section, use the plastic bump ring from the interior of cap...and then make the cap and barrel yourself. Would it work?

 

[budnder]

Roy your last post was very informative. I was curious, instead of rethreading, is it possible to harvest the barrel threads and just glue those into a new turned barrel? So a person could use the barrel threads made for the section, use the section, use the plastic bump ring from the interior of cap...and then make the cap and barrel yourself. Would it work?

Yes, it looks like that's how it's put together, so should be able to get it apart. It just looks to be glued. The barrel threads and trim ring are one piece, about 11.5mm or so "tall". From top to bottom, the outside dimensions are...

- a 2mm tall inner lip that's 12.6mm in diameter
- a 2mm tall trim ring that's 13.6mm in diameter
- an 7.5mm tall inner barrel that's glued into the body. The part glued into the barrel is about 13mm wide

I'll try turning the body off the barrel and see what happens...

 

[budnder]

Here ya go...

So I turned down the barrel... it's a super thin coat of paint/enamel/whatever over metal. I'm not a metal guy, but looks like some sort of thin stainless - harder than aluminum. My parting tool (wood lathe) wasn't going to cut through it very easily, so I took a file and cut through it that way. Once parted, the metal pretty easily peeled away from the threaded barrel insert. Attach is a pic of just the insert.

I updated the dimension in my previous post. The part that was glued in the barrel is a hair wider than I expected and it has a couple of ridges (for glue adhesion?).

I also took a pick with it on the section and beside the cap insert... kinda of a family picture of the "Jinhao pen kit" I suppose...

 

[QuoVadis]

Nice work Roy! Here's a question for you: do you think it's doable to do an all wood closed end pen with those parts? Is the metal you spoke of something that could basically calmly be a tube for a word d blank or would it be way too thick diameter wise once finished. Also trying to decide from your pics what to do with the plastic cap as it probably wouldn't support wood on it own. Any thoughts or ideas. I'm gonna buy a bunch of these pens tomorrow to do what you just did!

 

[QuoVadis]

Correction: could the metal barrel you turned down be used as a tube for a wood blank. I'm typing with my thumbs on a phone. My apologies.

 

[budnder]

Well, if you want the wooden body to be flush with the trim ring, that would mean the wooden pen wall would be 0.3mm. Not sure what the minimum is, but that's got to be cutting it close. Alternatively, you could just let it go fat and try to go seemless with the cap (e.g.let the cap come over the "trim ring" part of the barrel insert).

I assume the plastic cap insert could be glued to wood, since it was glued to the metal tube. It also has threads at the end that mated with the finial, so you could try and reuse the finial on the custom pen, or maybe use those threads to hold glue. The plastic insert is tapered, so won't present a continuous surface for gluing. I think my first take would be to drill two steps in the cap, with the deep step being sized to that threaded plastic insert end. The positioning of that plastic insert will need to be precise - after the cap engages the bump ring, it's the "downhill" side that keeps the cap taunt against the body, and that "downhill" side will only be like a 0.5mm or something similarly small. Too lean and the cap won't engage the bump, or won't get it completely and the cap will come off too easily. Too fat and the cap will rattle because it's not being held against the barrel.

 

[budnder]

Correction: could the metal barrel you turned down be used as a tube for a wood blank. I'm typing with my thumbs on a phone. My apologies.

It's tapered, so that might be problematic.

 

[QuoVadis]

I finally got 5 of the stainless steel x750s in the mail. Looking forward to tearing into them. Roy, on the barrel insert were you able to get the glue off of them? I'm hoping there is a brass tube that will fit that insert.

 

[budnder]

My memory was the glue came off easily. I think I recall just using a knife to "pop" it off.