How to get a perfect length tube/blank every time?

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mikeschn

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Jan 6, 2016
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Hey Guys,

Got a question for you. How to I trim my blanks to an exact length.

Let's say I'm turning an Elegant American. The tube gismo that gets pressed in there is exactly 2.0" long. The gismo has to protrude by 0.1" so my upper tube/blank needs to be exactly 1.99" long.

Using the barrel trimmer I overshot my mark, and then had to sand a little bit off the gismo. :eek:

Any suggestions how to get a perfect length every time?

Mike...
 
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My suggestion is to discontinue use of the barrel trimmer and switch to sanding. It is very easy to "sneak up" on the tube and there is much less chance of destroying a fragile blank while squaring. Add a set of digital calipers and you can get as exact as you wish.

Regards,
Michael
 
I have been making pens for only a year now but one thing I learned is that this is a craft not a production run. Do every thing as slow and as meticulous as you can. Take the time to do everything in small and enjoyable increments. I blew through a bunch of pen blanks before this settled into my brain.
 
I really don't understand the question. "Tube gizmo"? "Overshot my mark"? With a barrel trimmer, if you "overshoot your mark", you make the brass tube too short. Sanding won't fix that.
 
The cleanest, easiest and most efficient way to resize blanks, trim ends is what I show in the below video. Not only does this allow you to use chisels but all ranges and grits of sandpaper, CA and all other treatments.

In this video I took a standard size sierra blank and shortened it to fit a sierra grip.

https://www.youtube.com/watch?v=xfGCJnwdlsk

I used the blue painters tape to mark where the proper length is to reduce (yes I was cutting blank and metal tube alike in this video)
 
qquake said:
I really don't understand the question. "Tube gizmo"? "Overshot my mark"? With a barrel trimmer, if you "overshoot your mark", you make the brass tube too short. Sanding won't fix that.[/QUOTE

Sometimes, since the wood is softer than the tube, the trimmer will remove more wood then tube and the tube will stick out slightly. This can also be caused by the tube going between the cutter and the shaft.

The problem may not even be noticeable until you assemble the pen and notice a very, very slight gap between the wood and the kit components.
Click to expand...
 
Some rules of thumb to follow here.


  • If the kit uses a spring you have an enormous fudge factor on the kit.
  • If the kit uses a twist or a click transmission you have a close tolerance fitting kit and your tube length is VERY critical.
 
Mike; I believe I understand your question. Using your example of the Elegant American, I measure the tube length against the pen itself. Thread the transmission into the centerband. Insert the inkfill into the transmission and twist it until the point is in the extended position. Place the nib over the inkfill. Hold the pen with the nib pointing up. Now bring your blank up beside the pen and push the nib upward until the blank fits between the centerband and the nib. See how much of the point is exposed and you can accurately judge how long to make the blank. I have found some kits where the tube is not the correct length for the transmission spacing.

Hope this helps. Off to church now....
 
I do.

attachment.php


The gizmo is called a 'transmission' not to be confused with the transmission in your vehicle ;)
 

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Photo of Gizmo

Okay, so since you asked, here is a photo...

Here's the gizmo aka twist mechanism/brass clip stud assembly...

When the brass clip stud is pressed into the twist mechanism, it is exactly 2.000" long.

The turned blank is 2.024" long. I need to shorten it to 1.99" long, exactly. Over shooting the mark would mean that it is something less than 1.99".

I don't have a sanding disc for the lathe. I do have a sander, but I'd have to hold the blank by hand to use it. :frown:

Mike...

P.S. Opps, I see Ed posted while I was writing my post... yep, that's the gizmo! :biggrin:
 

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Mike, the best way as mentioned to sneak up on a correct barrel length is to sand it. You really should get the components to make a very easy one if you do not have them already. JimB shows an easy way of doing this. Faceplate with a flat surface and use sticky back sand paper. A set of transfer punches from Harbor Freight. and a drill chuck. These things you should own already.
 
mikeschn said:
Okay, so since you asked......I don't have a sanding disc for the lathe. I do have a sander, but I'd have to hold the blank by hand to use it. :frown:
Click to expand...

Make a jig for the sander. Once squared up to the disc and the correct transfer punch in it, you slide the tubed blank on the punch and gently offer it to the sander. I'll attach a picture of ours even though it's been posted a number of times.
 

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There's also Rick Herrell's jig:

http://www.penturners.org/forum/f172/custom-made-penturning-tools-accessories-92501/

I tried trimming several ways before finding what worked best for me. I have seen others trim very delicate materials with a steel (non-carbide PSI) barrel trimmer and a hand-held drill - a practice that I couldn't even master with a carbide trimmer and a drill press. With experimenting and observing your results, you will find what works best for you and is likely to be a method posted here.

Much success!
 
Thanks for the ideas. I am going to have to print out a jig of some kind to hold my blanks. :)

Mike...

TonyL said:
There's also Rick Herrell's jig:

http://www.penturners.org/forum/f172/custom-made-penturning-tools-accessories-92501/

I tried trimming several ways before finding what worked best for me. I have seen others trim very delicate materials with a steel (non-carbide PSI) barrel trimmer and a hand-held drill - a practice that I couldn't even master with a carbide trimmer and a drill press. With experimenting and observing your results, you will find what works best for you and is likely to be a method posted here.

Much success!
Click to expand...
 
I have always used a barrel trimmer. I trust the perpendicularity (wow, can't believe I can even spell that!) better than setting up anything else. As far as trimming to length, any thing you use takes a bit of getting a feel. I can feel when the trimmer gets to the tube. Can't explain it, really, but there is a different feel when you are cutting just wood, and when you get to the tube. My guess is there is some of that with sanding as well. Most of the components are not so critical that a small fraction taken off will effect the finished pen.
 
corgicoupe said:
The only disadvantage of the trimmer is the expense of buying another reamer for a new tube diameter.
Click to expand...

If you take a 7mm tube you can add an inexpensive blank and turn it down to the internal diameter of whatever tube you want to be able to trim, works great! I've got one for all of the main pens I turn although I still use the sanding jig most of all.
 
But the reamer has cutters that will remove any internal glue; the sized dowel cannot do that. But it is a viable solution if the tube is clear.
 
You used the word "perfect" in your title.

I use a metal-turning lathe and a pair of digital calipers, having written down the desired length from actual measurement (or manufacturer's specs) beforehand.
 
Do you have the instructions on how you made your homemade Jig good sir?

JimB said:
You will get better with the barrel trimmer with practice but as Michael said, sanding is easier to control. I use both. If I don't get the blank close enough to final length I first use a barrel trimmer to remove the bulk of the blank then I move over to do final sanding/squaring on my lathe using my homemade jig.


View in Gallery
Click to expand...
 
I've been using Ricks offset sanding jig for a while now and It works great. Invaluable in cleaning up the ends after applying a ca finish
 
I just use a belt sander with it's "miter gauge" to quickly bring the blank down to the brass tube. It makes a different sound as soon as you start hitting brass. If you use a light touch toward the end, you can avoid taking any significant brass off the tube. I think of this as my rough sanding. Once I have the blank turned down to the correct diameter and sanded, I will use my squaring jig, which I use to precisely square the ends. I also use this squaring jig again after I apply my CA finish to make sure the ends are flat and square to the long axis of the brass tube. Makes for perfect joints every time and I've never had a problem with shortened tubes.

Here's a link to my sanding/squaring jig.

Other helpful links:
Hook and loop conversion pad
By using a hook pad on the squaring jig, I can easily use and reposition cheap 5" sanding pads used on random orbital sanders. I just reposition it as needed until every area is used up.

Transfer punch set

Previous post
 
wfsteadman said:
Do you have the instructions on how you made your homemade Jig good sir?

JimB said:
You will get better with the barrel trimmer with practice but as Michael said, sanding is easier to control. I use both. If I don't get the blank close enough to final length I first use a barrel trimmer to remove the bulk of the blank then I move over to do final sanding/squaring on my lathe using my homemade jig.


View in Gallery
Click to expand...
Click to expand...

It actually was very easy. I bought a 1x8 bolt (nut) from Fastenal for about $1. Epoxy it to a scrap piece of hardwood. Let if fully cure and then mount it to the headstock and turn down the wood. The hardest part is getting the face where the sandpaper goes perfectly flat. I don't remember what tool I used to do it. Get it as close as you can then use sandpaper on a flat block to finish it off. Attach sandpaper. In the tail stock is a Jacobs chuck and a punch. Both are from Harbor freight.

The one pictured was my first one. I've made a couple more. The new ones don't have a nut. Instead I have a 1x8 tap and tap the piece of wood so it screws directly onto the headstock. Both my lathes are 1x8 so these fit both.
 
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