Last week I turned a pen for my granddaughter and started to assemble it in my usual way, using my woodworking vice as a press. The twist mechanism was a very tight fit and I could feel the assembly getting out of line but just about managed to complete the assembly. I'd toyed with buying a pen assembly tool before but they are typically over £50. Then when browsing the Turners retreat site last weekend I saw that they sold a lathe mounted tool for just under £20 that looked perfect so I ordered it. Screenscrape from the browser...
It is really easy to use. the small section stays in the tailstock which is then wound to apply pressure. for fitting the nib and cap the brass tube is slid over metal rod. What I didn't realise from the photo online, is that the twist mechanism sits inside the other end of the headstock piece - this stops it from moving out of line when pressure is applied. As long as you have a headstock tread protector it is very quick to remove and rotate the headstock part of the tool (or be more methodical in batch assembly!). A simple tool that does its job well. I assembled the 4 pens I had turned.......
I also purchased the pen disassembly kit - not just because I do pens, but the hardened rods are in plenty of diameters that I can use for other drifting tasks. The gripper is a modified 'mole grip'.
I didn't expect to need to use it on day one! I'd forgotten that one of the four pens had a shorter tube than it should (due to enthusiastic barrel trimming), so when the twist mechanism was inserted to the marked line, the nib stuck out about 1mm too much - previously I'd have left it, but it was an ideal time to try the tools. The clamp gripped the acrylic perfectly and a drift (3rd size up from memory) fitted through the twist mechanism to knock out the nib, then using another best fit drift, the mechanism was knocked out. The assembly tool was then used again, this time stopping early and test/adjusting the fit.
In summary two good tools, and a set of drifts that have a wider use case than just pens. The assembly tool also comes in 2MT taper.
Dave