Taffy Evans wrote: ↑Wed Apr 12, 2023 3:17 pm
Hi again, well I might be a bit early making any (positive) comments, but, using ideas gained from this thread I did the following.
I put extra force on the clamping lever and, as I said before, moved the whole assembly so it sat directly under the slot in the drum.
I could not see any way the paper could be gripped but pushed it in to the opening and then pushed it down further with a small steel rule, as advised.
I then released holding pressure on the clamping assembly and let the spring pull the whole assembly back…
I pulled really hard on the, unfitted, test piece of belt and could not move it.
I will try a proper set up tomorrow.
You can add to the sander issues, (from new).
Hight adjustment will not go lower than 5mm so I have to use a sheet of Masonite on top of the drive belt.
There is a few thousands difference on each side of a board. Not a level drum.
The drum rises as timber goes through, so I use multiple 1/64” passes.
I’ll be back
Taff
Hey Taff (and others!).
The outboard spring clamp is a simple lock to start your wrapping process. The inboard clamp mechanism is both a clamp and tensioning device. Your first depress of the spring is simply the clamp opening, but as you suggested, this does not appear through the slot in the drum. Holding this spring in and pushing further, you activate and rotate against the second higher tension spring, which then brings the open clamp into alignment with the slot. Feed the final end of the paper through here. The purpose of this two-part mechanism is to first clamp the end of the paper, as per the outer clamp, but then when released, the spring returns it to the original position, pulling the drum wrap tight. This should prevent the paper from sliding around on the drum. This is a deliberate design found on many drum sanders and is necessary to keep the paper under tension in use.
With respect to the minimum depth, this too is by design. Although the precise depth varies from brand to brand and model to model, the limitation is in place to prevent you from lowering your drum into your feed belt and destroying that, or worse, the bed underneath. Remember, sanding to such specific thickness (or is that thinness?) the likes of which we work in, is quite a specific task. These machines were not designed for luthiers as such, they are just very useful for that purpose! A sled is always recommended and in fact required, for our work on a wide drum sander.
Finally, yes. The drums are not always level or moreover, move over time and require adjustment/setup. This comes as a result of having such a large/long heavy rotating drum, hanging from a single end, then put under heavy load. Over time, it will move. Some machines the only fix for this is shims, which are usually included with the machine from the outset. Other models have various height/levelling adjustments for the bed - some easier to use than others. This is part of the setup/maintenance of these machines and will require adjustment from time to time. However, there is another work around...
Get a piece of quality plywood to use as your sled - the thicker it is, the more stable and likely to stay flat. Cut this down to the width of your drum sander's capacity and a little longer (say 50mm) than your largest back or side requirements (build two different sizes if your prefer). On one face, mark it with pencil from edge to edge. Feed this into the sander removing very small amounts per pass. When you have a full clean face, you now have both a (nearly complete) sled to use for your guitar requirements, but also one that matches the slight inaccuracy between your drum and bed - therefore giving your stock an even flat cut. Of course, you may need to resurface this from time to time through use, with additional movement of the bed or drum.
Make sure you mark which way it goes so you don't accidentally reverse the direction and double your discrepancy! Next, you will require a "stop" of sorts at one end, to prevent your workpiece slipping. This only needs to be 2mm or so to provide a good lip for your workpiece to sit against. If you rout a trench, say 10mm wide by 8mm deep just in from the back end of the sled, you can use a thicker piece of standard stock timber such as 10 x 10mm pine inserted into this trench, giving the 2mm lip projection required, but also being removable and replaceable when it inevitably wears down. For some jobs, I remove this piece and use some double side tape on the front edge of the stock being sanded. This is done on excess length, as the double sided tape creates an unevenly thickness sanded piece - but that is how I sand some some stock to veneer thickness such as 0.7mm for purfling lines etc. When you get this thin, the back stop is less effective and the pieces can lift and be destroyed. Pinching from the front works better for very thin sanding.
In any case - I admit I did not read every post on this thread, so if this has already been covered, my apologies. If not, I hope this helps resolve or at least explain, some of your concerns.
Cheers,
Jeremy.
