Summary
I recently replaced the 3 Morse taper ER 25 collet chuck on my mill but without really thinking about the implications of the drawbar diameter it was going to need.
On taking delivery I discovered it needed a drawbar with an M12 thread, the spindle bore was drilled through at 3/8 inches diameter.
This short article records the steps I took to open the bore out and the method of attack used on this particular machine.
Introduction
The change of chuck became necessary when the first two threads on my previous ER 25 collet chuck started to pick up on the nut, making it difficult to engage the nut without risking a crossed thread. Other threads on the chuck were also beginning to crumble. The chuck wasn’t actually that old either, maybe three years or so, but It uses a drawbar thread of 3/8 inch Whitworth which of course suited the Dore Westbury mill very well indeed.
The chuck is hardened throughout which effectively ruled out the possibility of lightly chasing the 1.5 mm thread for the closing nut. In the end I made a working repair to it by turning off the first two threads and followed that with a little fine-grade valve lapping paste to bed the remaining threads of the chuck and nut together again. Photograph 1 shows the result.
It is still a useful chuck but is now ‘under notice of eviction’ in case of further thread deterioration.
However, it is such a useful piece of tooling I decided to replace it anyway. The replacement came this time from Arc Euro Trade, the previous one was from RDG. Both are well-respected companies and there was no bias made in my choice of replacement other than to avoid another fully hardened component if I could.
Diese Geschichte stammt aus der March 2020-Ausgabe von Model Engineers' Workshop.
Starten Sie Ihre 7-tägige kostenlose Testversion von Magzter GOLD, um auf Tausende kuratierte Premium-Storys sowie über 8.000 Zeitschriften und Zeitungen zuzugreifen.
Bereits Abonnent ? Anmelden
Diese Geschichte stammt aus der March 2020-Ausgabe von Model Engineers' Workshop.
Starten Sie Ihre 7-tägige kostenlose Testversion von Magzter GOLD, um auf Tausende kuratierte Premium-Storys sowie über 8.000 Zeitschriften und Zeitungen zuzugreifen.
Bereits Abonnent? Anmelden
Readers' Workshops - Patrick Cubbon
Patrick Cubbon describes his workshops – a portable one from 1963 and the current accommodation
Desktop Gear Hobbing
Toby Kinsey has designed this fascinating piece of gearmaking equipment
The John Stevenson Trophy 2020
Many readers and forum members will remember John Stevenson, a contributor to MEW but best known for his larger-than life presence on the Model Engineer forum.
From the Archives: Twist drill Sharpening by the Four Facet Method
Giles Parkes, MEW Issue 64, February/March 2000
Dividing on the Warco 220 Lathe
Peter Shaw describes a mandrel dividing attachment for this popular lathe that can be adapted to fit many other benchtop machines
Choosing Steels
Stub Mandrel offers some advice on choosing the right steel for the job
A Storage Story
Robin King shares the lessons learned from his experience of workshop moves
A Simple Drill Grinding Aid
A newcomer to our hobby was having trouble sharpening drills, so Howard Lewis made a simple aid for him
Yet Another Bodge-Up!
Peter Shaw finds a use for some aged homebrew slot drills.
Workshop Press Tooling Part 2
Will Doggett makes a set of tooling for his press tool described starting in issue 285