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Drum Thicknessing Sander Build

Documenting my woodworking drum thicknessing sander build.

Design

The design I chose was based on plans by Matthias Wandel, the woodgears.ca guy (woodgears.ca/sander/plans/), along with various tweaks from other forums and YouTubes, plus a few of my own.

Materials

I decided to scale up the plans, as I am aiming to build acoustic guitars, including oversize acoustic bass guitars.
To minimise warping, expansion and shrinkage, I used hardwood (Tasmanian oak), and marine-grade plywood.
Both of those are much heavier than pine and also more expensive.

I also decided to use PVC drainage pipe for the drum, rather than disks of MDF. The idea was that once the internal mounting disks were trued, the drum itself would require very little additional trueing.

The build

Drum components (the disks were an early attempt and not used)

Frame pieces - Tasmanian oak, almost certainly over engineered

The basic frame assembled

Bracing for the table

The work table mostly complete

Hinges attached

Attaching the table to the frame

The table lift assembly using a press screw

Motor (2HP) and pulleys. The motor runs at 2800 rpm, 5" and 8" pulleys bring this down to 1750 rpm. Since the drum diameter is 160 mm (6.3"), if my calculations are correct that gives a velocity of 2886 surface feet/min.

Testing the power train

I decided to add more bracing to the table to increase torsional stiffness

The electronics tidied up

Components of the drum mounting disks

Glueing up the mounting disks. A length of 25mm PVC pipe is used (smeared with car wax to guard against glue squeeze out) to keep the holes aligned.

Completed disks. The four screws are to prevent splitting from the set screws used to secure the disks to the steel axle.

Trueing up the disks with coarse sandpaper. A small section of the PVC pipe is threaded so I can test the fit.

The drum fitted. I was planning to use small countersunk screws to secure the drum, but friction appears to be more than adequate (I had to use a rubber mallet to fit the drum). If the disks shrink, I can always add screws later.

Some cross bracing for the frame

Dust shroud frame

Completed dust shroud with integrated upper safety guard

A lip around the ends of the table, so that the top layer (melamine coated) can sit securely, but be easily replaced if worn or damaged.

The lower safety guard

Testing the fit of the dust port

A shim underneath one of the pillow block bearings to get the drum perfectly parallel to the table

Trueing the drum with sandpaper. If there is any event of movement, shrinkage or expansion, I may need to do this again.

The drum after trueing

A roughly assembled benchtop to allow the unit to be used as a light-duty, elevated work area when not in use.

Sandpaper loaded, held in place with hose clamps (which overhang the sides of the table)

The table lift press screw was quite loose, and the vibration (which was not excessive) was causing it to unwind, lowering the table while in use. To fix this I made a "lock nut" from construction plywood, which works well.

The first test - a piece of hardwood (Tasmanian oak), went through nicely. I took it slow, about three passes to take off 1mm or so. It's not super smooth, as I was using 80 grit paper, but it's level and even, and the trued-up drum performed well (no "bumping").

Final Verdict

Time will tell how much additional truing the drum requires - I waited three weeks between trueing the mounting disks before addressing the drum, so hopefully things have settled down.
There is some vibration, but certainly nothing alarming. The machine is very quiet - the vacuum cleaner used as a dust extractor is far louder, leading to momentary confusion when I switch the sander off, but the noise stays the same.
Speaking of the vacuum cleaner - it is not as effective as I'd hoped, quite a bit of dust shoots out the front. I may lower the leading edge of the dust shroud, that might stop a bit of it. (All this will come as no surprise to anyone with experience of a real dust extractor).

The looseness of the press screw was the only surprise, but the wooden lock nut solved it perfectly. When making it, I didn't even use a proper thread tap: I just drilled the plywood and clamped two pieces of pine either side, drilled slightly wider. This kept everything in alignment, and prevented tearout as I force-threaded the press screw itself through the whole lot.

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All content Copyright 2015 Trevor Magnusson