Get out of jail card

It is Sunday, (or after trading hours), or simply live too far from your normal woodworking supplies shop, and your drum sander has run out of abrasive.

What do you do?

I decided to find out if there was an alternative, if only temporary to get you out of trouble so you can finish the job you are doing.

Headed down to Masters to see what was on offer.  Seriously….very little.  Certainly no cloth backed sandpaper in a roll or of any length.  About the only stuff I could find was a very weak paper backed painter’s sandpaper.  No idea how it’d survive – you just touch it and the abrasive is flaking off the backing.

Went to take a length anyway, and discovered that even worse, it is perforated every metre (for easy tear-off – the last thing you want for a machine sander!)  But there was nothing else, so it was either this to get out of jail, or nothing.  It wasn’t the right width either, so it was going to be an interesting attempt.

First, I took some packing tape, and ran a length down the entire back of the 2m long strip I bought.  Oh, and the strip cost $4 ($2/m), compared to something like $18 for the real deal.  (Remembering this is a temporary fix, not a long term viable alternative).

With a bit of guesswork, I trimmed the end to an angle, then with a bit of adjustment got it so each loop butted up against the previous, and got to the opposite end of the drum.  That was a lot easier, as the end was simply trimmed to be parallel to the edge of the drum, and secured with the second clip.

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Kind of looks the part doesn’t it!  Also proves that you can use other widths of sandpaper – you are not restricted to just using a 75mm wide roll (think that is what the standard width is).

A quick test – turn on and off (while standing clear) – seems to work – it didn’t fly to shreds instantly.

Next test – sand something!

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Took a scrap of timber, and ran that through.  It survived as well, even multiple passes.  You can see a gap at the right hand side- I hadn’t gotten sufficient tension in the roll, so after this pass I readjusted the paper to get it tight on the drum again.

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After a few passes, the wear is a lot more evident on this sandpaper than is on the garnet cloth-backed sandpaper.  However, it was working.

So let’s do it for real.  Got the piece of walnut that I needed to sand, and ran it through again, and again to flatten it off.  I did go with a slower feed speed and less height change between passes to give the paper the best chance for survival.  Even so, near the end of the job the drum was bogging down a bit as the paper was loosing its ability to cut.  But I got the piece flattened (over a dozen passes)

Turned it over to dress the rear side a bit, and managed to get about three passes in before the paper exploded off the roll.

It wasn’t dangerous – the paper was flapping a lot on the drum, but there was no issue in turning the machine off.  There were bits of sandpaper everywhere (about 1″ square) – when this let go, it really let go!  Surprisingly, the perforated area halfway along had survived (although had started to tear when the length failed).

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The proof of concept was achieved however – I have a nicely sanded piece of walnut – so this indeed “get me out of jail”  It isn’t the most economic – an $18 length will last and last (until you burn it or do something silly, or wear it out), but for a one-off when the shops are shut, this worked.

Be your own judge whether you choose to ever do this for yourself or not.  I am satisfied that there was no real risk (and I stood aside even so).  If I have to do it again, I may try gorilla tape next time – something a bit stronger than a cellotape-type packing tape which may increase the time the temporary fix can survive.

My Drum Sander

Unsurprisingly, I have begun mentally (mostly) dusting off some of my machines, reconsidering their place in my workshop (and not just where they will go, but whether they belong).  For the most part, they will simply translate from the old workshop to the new, but in some cases, I haven’t been 100% content, and these will receive closer scrutiny.

One of these machines is the drum sander.

Now I don’t have the most expensive drum sander on the market.  Actually (excluding home-made versions), I think I probably have the cheapest.  Even so, at $840, it isn’t an afterthought either.  I can buy a cheap cast iron tablesaw for that sort of money, so you’d expect a lot to be packed into a small package at that price.

Carbatec Drum Sander

Carbatec Drum Sander

I’m not denying that the drum sander isn’t a useful tool – having had one for a few years now (over 4), I have put quite a bit through it, and have found it does work pretty well.  It could be improved, and I’ll get to that in a second.

Firstly, location.  Since having it in my workshop, I have had it perched on top of my thicknesser.  A bit higher than desirable, but still workable, and as both machines had similar requirements for infeed and outfeed, it proved a pretty good space saver.

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This only works if your thicknesser is the larger version, with a fixed head and rising and falling table.  Otherwise you’d be lifting the weight of the motor and thicknesser head, and the drum sander combined!  However, it is time it got its own stand.  There is one made for this unit, and although I am not a fan of bolt-together pieces of angle iron as a commercial solution, for $70 it wasn’t too pricey, and it ended up proving to be a pretty robust design, so I can live with that.  The space underneath isn’t going to be wasted either – just have to make a storage unit that fits.

The next issue is the method by which the paper is secured.  At the free end, it is pretty straightforward – a springloaded clip that holds the paper against the underside of the drum.

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It is the other end that has been bugging me recently.  I just have not been able to get the paper to secure.  Initially, I had a look at the clamp at the other end, and it didn’t push against the drum – that was a concern – what had gone wrong with the clamp?  A stop into Carbatec to look at their display machine, and it was the same – the paper does not get held against anything, it is just a bit of a torturous path to hold it in place.  So it is the length of the sandpaper which is the problem – the piece I have is too short.  Must be old stock or something – and the supplier was scrimping on the length of paper supplied.

Now I have had a close look at the clamping arrangements, I’ll cut my own to be longer, and see if I cannot get it resolved.

I do find a lot of burn marks on the drum – and that I have worked out is primarily a lack of adequate dust extraction.  If a dust buildup occurs between the drum and the workpiece, it burns, sticks, burns more, and the paper is quickly toast (pun intended!)

Guess there is no way around this really – have the correct feedrate for the timber and the grit, take lighter passes, and good dust extraction.  The large oscillating Jet may not have such a problem, but otherwise I’d expect this would be a pretty typical complaint?

The final area that I looked at is the one where the most criticisms are leveled at this machine. The amount of flex in the head.  If you lift the open end, you can detect some movement relative to the bed.  In operation, this equates to the machine not operating the drum parallel to the bed, and therefore creating a wedge shape, rather than simply making the board thinner.

To now, I have compensated for this by a few strategies:

1. rotating the work each pass
2. taking lighter passes when nearing the final desired dimension
3. feeding the work in closer to the support when nearing final dimension
4. finishing passes by not adjusting the height, and feeding the work through a few times, each time therefore becomes a lighter and lighter pass, with less and less deflection.

While in Carbatec looking at the clamping system, I also spent some time comparing this drum sander to the three Jet models.

There were some interesting outcomes.

jetn628900Not only is the drum quite short (and therefore not a lot of length to load up for deflection, but note how far apart the two bolts are holding the upper structure to the base.  It is a good amount of area resisting any rotation of the head around that joint.

JET-2244OSCNot sure if this is exactly the one looked at (wasn’t looking at the stand!), but the main point of difference here was a cast iron base which the head is attached to with a wide attachment area.  Very hard to get any movement here!

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This had less movement than the Carbatec model, but still significantly more than the other two.  The bolts attaching the head to the base are quite close together, and the base is angle iron, not cast.  And there is movement.

The Carbatec model looks to all be cast, but the main members of the base are angle iron.  Furthermore, the bolts attaching the head to the base are very close together.  Add these together, plus what flex there is in the attachment bolts and the cast iron, and there is deflection.

If the attachment point could be reinforced, and the attachment bolts (both at that junction, and where the head connects to the height riser) were replaced with high tensile bolts, I may not be able to eliminate all the flex, but I bet I could significantly decrease it.

A mini project to work on!

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