The Experiment Continues

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DrD

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I have about exhausted the different ways I can think of to manufacture this style of ballpoint: short "fountain pen" type section mated to a longer main body.

The first attempt was to make the section and the body as two different parts; that had the problem of getting a seamless transition from the section to the body. Then I tried using a longer blank and the parting off the section. You guessed it, due to the very slight taper going up into the body from the section, once parted, losing the "kerf", the od's of the section and the body didn't match. No problem, you say, just get the 2 back together and create the smooth transition. Now I was faced with the same issue as I had in making the 2 parts separately. If a long brass tube - 4.5" - is inserted to stabilize things, you may find perceptible wobble between the blank and the tube. This is a problem.

After much head scratching, the problem became evident: CONCENTRICITY. Let me explain. Measuring a number of 7mm brass tubes, I found the od to be consistently 0.265" to 0.266". The 2 different drill bits commonly used for 7mm pens are: 7mm bit, od 0.276", and the letter "J" bit, od 0.277". Couple that with the mounted drill bit run out when mounted in either a drill press using (typically a Jacobs MT 33) or in a lathe, and you will add at least another 0.001" or more to the hole you're about to drill, not to mention additional error due to method of mounting the blank, round or square.

The next factor affecting the concentricity issue is the length of the bit itself compared to the length of the blank; you may have to retract the bit and either move the blank or retract the tailstock quill. Each time the drill is re-inserted into the blank, the entrance point into the blank, and for some distance into the blank may become more out of round, and possibly become greater than the expected bore diameter. Experience has also shown me that if one lets the bit or the blank or both heat up, the drilled out material may become matted (read semi-melted) and adhering to the flutes of the bit. Upon removing the bit, that matted crud has the possibility/probability of further eroding the concentricity and the diameter of the bore hole.

Where this comes up to grab you is when you glue in the tube(s). Usually in acrylics, but maybe not always, the brass tube, when inserted will slide in and out freely. If using to separate pieces - section and body - this means once the body tube is glued in place, the brass tube of the section may be concentric with the body. That is to say, when the section with brass tub in inserted into the body with a glued tube, there most likely will be some "wiggle" of the section tube inside the body. These variances aren't much, but they CAN keep both pieces from becoming perfectly mated.

I further noticed that , inserting the transmission into the section tube, the above issue doesn't always go away, there is still some wiggle - not a good thing to have when shearing with a lathe or sanding.

So my experience has been there is always a teeny tiny lip (maybe a 0.001" or so, but noticeable to the touch) between the section and the body. This may be more pronounced when the section is rotated to move the pen tip in or out.

Given all that, I have found these pens are way more difficult to turn than I first imagined. Any comments, help advice is greatly appreciated. Attached is the latest attempt. It is a BHW Streamline 7mm kit in chrome with a translucent gray body (could not find this particular AA on BHW's web site any more) with a translucent red (AA24P) section. Finish was wet sanded with 320 grit on lathe at ~800 rpm; removed from lathe and wet sanded by hand long-wise (horizontally?) with MM2400 until no radial - round-wise - scratches are evident under 6 x magnification. Next wet sand by hand long-wise with MM 12000 until no scratches are evident. Finally, hand buff with Micro-Gloss.

Thanks for reading, and happy turning,

DrD
 

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DrD

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WOW !!!

Extremely nice !!!

A "silvery" ring between the red and black might be appropriate ..... what do you think ?
Thanks for the compliment! I think your suggestion of a "silvery" ring is "sterling!" I think it was Mark James who had earlier suggested a copper ring for one of my wood pens I had posted.

My question to you is how to do it? I've never done anything like that before, and would love to learn how. I tired once with some brass shim stock, and that was a complete and total disaster.

Thanks!

Don
 

magpens

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My question to you is how to do it?
Thanks!

Don
@DrD

For this red and black pen, I would suggest an aluminum disc. . Sand on both sides and use epoxy glue. . I have done this successfully for a pen that is constructed in the conventional way .... but things might be more tricky in the case of a single barrel slimline where you may not have the complete internal support of a brass tube. . I don't know your construction method. . It may be that, in your design, the pen comes apart at the red/black transition for refill replacement. . Even so, the alum. disc at that point could work ... but the machining of the alum at the end of a piece of resin could pose problems. . I have only done it with the alum. sandwiched between resin pieces to form a continuous cylinder so that the whole can be machined in one operation.

Brass shim should work also ... again with epoxy glue. . Also copper sheet.

Bear in mind that I do all my pen turning on a metal-working lathe. . That might give some advantage.

I have read your original post ( OP ) and can relate to the issues you raise. . Drilling blanks on a metal-working lathe is, I believe, more accurate than drilling on a wood-turning lathe. . After my initial attempts at drilling blanks with a drill press some 10 years ago, I have never done that again.

Even when drilling on a metal-working lathe you have to be very careful. . I always start with a round blank (accurately sized the same along its length to within 0.002" or better). . Also, I always accurately square the ends of the blank before attempting to drill.
And throughout the drilling process, I go quite slowly and back out every half-inch or so. . With "acrylic" materials, I always use WD-40 as a lubricant. . (You h ave to clean the hole with alcohol before gluing.)

My drilling speed is always around 200 RPM to try to minimize the heat.

When drilling a blank over 2.5" long, I go in from both ends .... It's probably harder to achieve accurate meet-up in the middle when drilling like this on a wood-turning lathe, which has a much shallower head-stock throat than a metal-working lathe.
 
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magpens

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@DrD

I have now read your TADT thread.

If your construction method for this red/black pen is the same as for your all-red pen in the TADT thread, then you probably will have a problem with the glue joints at the alum. disc because there is probably not sufficient "meat" in the blank material to give a reliable glue joint.

I have made one or two, but I do not routinely make single barrel slimline pens, so I have not had much experience with them.

However, I do make single barrel pens using the PSI Slimline PRO, which uses 8 mm brass tubes. . But I have never done the aluminum disc feature with one of these pens.

I will probably do so at some time, now that I have seen your gorgeous pen shown above.

I have to say again, that I find this pen of yours EXTREMELY attractive !!
 
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DrD

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Thanks Mal for the kind words. Would love to see some of your work with the 8mm pens. Also would love for you to jump into the 7mm Section pens. Below are a few of previously posted photos of a stable-mate of the red/gray pen of this post.

Thanks again,

Don
 

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howsitwork

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Don

aproaching it from a different angle. Stick with your method and add a very fine chamfer at the break line , to allow easy extraction of the front end for refil changes. If the chamfer is very fine, say 0.5mm bevel on both pieces you end with a fine, visible break at the joint. Your eyes are telling you there should be a difference there so when your fingers find it you allow for it so it’s not an error or irritation to the user.

I too greatly like the shape and as I have lots of 7mm kits I shall have a go. Mind you it will have to wait as currently I am experimenting with Ken’s celtic knot jig and playing with my new sliding mitre saw !

Having re read Mals comments above if you were to use an aluminium ring and attach it to the black bit of the above pen it would be supported by the tube and glued to the black cap so should be ok? I would not use CA to adhere it as it’s heat fragile , epoxy should be ok and hopefully any heat generated by sanding would be transmitted to the brass tube? Having said that I did use CA to attach a rough aluminium disc to a steel washer once I then gripped the steel washer in a 3 jaw chuck and turned the aluminium to true round. It worked twice and the third time it failed but the disc was 4” diameter compared to the 1” diameter steel washer. So that was wit an intermittent cut and the forces involved far exceed what the end load on the aluminium ring would be in your situation.
 
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