Monday, April 11, 2011

taig lathe cabinet - drawers, slides and lock

On a roll here - hopefully the 'phone won't ring...

Drawers for the lathe cabinet.

A few design criteria I specified;
a - accessible from the front of the cabinet - previous stand was from the RHS (under tailstock) - never used because it required too large of a footprint on the workbench
b - no "un -viewable" space - the drawers had to be able to be viewed in their entirety.. to often the tool I need is found hiding in the very back of the drawer
c - drawers needed to be big enough to be useful, but small enough to be hard to overload
d - preferably lockable - more for controlling little fingers rather than theft.

To the "bin of useful junk"... and I returned with 2 pairs of drawer slides I had previously salvaged from some BIG photocopiers. These slides were used to house internal mechanisms (or was it 2000 sheet paper feeders.. I can't remember) so they're made tough, and best of all they extend out to 2.5 times their length.

Figure 1 - Salvaged drawer slides

When I built the base frame, I included some flat rails for bolting drawer slides in place. I had pre-drilled them to match the slides and simply welded them inside the frame. The centre rail was effectively double-sided since it was designed to hold a rail on each side, plus I made it longer to provide a tongue for a locking mechanism.

Figure 2 - Drawer slides fitted to base frame rails

The drawers were then drawn up on the sheet metal with a width to match the inside width of the drawer opening - drawer slide to drawer slide, depth, and height, to match the base frame - with suitable reduction for clearance.

The drawers were cut and folded using the previously described methods (clamped between tubing and angle-iron, bent over with bits of wood, and metal flatters)

Figure 3 - Drawers made and fitted to slides

After the mistakes were corrected, the drawers were shimmed up to the correct height for clearance, and holes drilled for the drawer slides. Bolts inserted, nuts tightened and all done.

The next step was to make some fascia sheets for the front of the drawers so the gaps around the sides for the drawers slides wasn't as obvious.. measure, drill, and pop rivet on.

The handles for the drawers are actually bus insulators from a switchboard I scrapped. A friend needed the breakers, and I disposed of the rest. The insulators were trimmed with the grinder, and then screwed in place to form the handles.

Figure 4- Drawer extended out to show the full drawer contents

As mentioned previously, the central slide rail was made extra long so a tongue protruded. This tongue was cross-drilled and a matching plate with slot was made from 4mm sheet. Locking the drawers is as simple as closing them both, then placing the plate over the tongue and slipping a lock on - illustrated here with a bolt.

Figure 5 - Demonstration of locked drawers

Writing this article doesn't do justice to these headaches these drawers caused... It's easy to blame my tools, but every one of the problems I had with these drawers actually highlighted something I'd read about, but luckily avoided thus far in the project.... metal stretch

If you're going to use the same methods I did for bending metal - clamping and hammering, be aware that the metal will stretch as you work it. I found the sheet metal stretched by about 4% over the length based on hammering in 4 bends... that doesn't sound too bad until you're trying to hold a dimension to within 2mm (about 1/16") so the drawer slides aren't tensioned in use.
The answer to the issue - test bends on scrap first, and clamp up tight to avoid shifting... the clamping is why I'd love to build a brake, but even then I'd still do test bends for high tolerance work.

Resulting drawer sizes...290W x 100H x 450D  and 375W x 100H x 450D (11.5" or 15" x 4"H x 18"D)

NB - A note about scrapping photocopiers... The local photocopy guy gets paid $50 for each defunct/ old copier and they get shipped to India for refurbishment... For $50 I can bring home a photocopier which is nearly the size of my 6' x 4' trailer and salvage many heavy duty slides, at least 4 NEMA 27 or 34 Stepper motors (and several smaller ones), a few PSUs, shafting, bushes, pulleys, mirrors, etc. It takes about 6 hours to tear one down to the last nut and bolt if you use a cordless driver, but you get a treasure trove of useful bits - hence why the Indians want them. A bonus, you get to learn about how they are built, the engineering and tricks in their assembly and design.

Next installment.. most likely the top tray and control panel.. that will wrap up the mechanical construction.

No comments:

Post a Comment