Drum Sander envy

[andersonec]

Am I being daft or isn't the direction of rotation be wanting to push the wood back towards you? it sounds like it is pulling it through.

Andy

 

[CHJ]

Can I just ask a stupid question? As you feed the wood under the roller, what's to stop it getting fired out the other end?

Thanks

Si.

Surely you should feed against the direction of rotation so that the drum is not trying to climb on the work piece.
That way it will not spit out of the other side and it will be less likely to be thrown back at you.

Am I being daft or isn't the direction of rotation be wanting to push the wood back towards you? it sounds like it is pulling it through.

Andy

Exactly

 

[Bigdanny]

Stupid questions are always welcome because they are sometimes not as silly as you think. I hold the wood back slightly as I feed it over the table and under the roller, once it is almost all the way through I catch on the other side and ensure that it finishes the passage at more or less the same speed. I assume this is the same for a planner/thicknesser. It only gets launched at the last centimetre or so because the rest of the time the friction of the whole surface on the table is far greater than the friction across the drum. The sander is one supposed to take off a small amount at each pass.
The plywood is completely smooth, as easily as smooth as mdf would have been, it just doesn't look it because of the dark and light strips caused by the end grain being intermitently at 90 degrees to the piece adjacent to it. This is not the cause of the abrasive load tearing. The original 1950's plan I used suggested plywood. I don't really see how running the drum in the other direction would stop the abrasive from tearing as it would actually increase the load on it.

Hi Gerard, A lot of other homebuilt thickness sanders seem to be built on the principle of pushing the wood though. See http://www.youtube.com/watch?v=W-5Sj6kB ... re=related. For the small inconvenience of swapping 2 wires and a length of sandpaper , is it not worth trying the motor in the opposite direction. Quite often the tables on the homebuilt sanders are built at an angle to give some gravity assistance when pushing through the wood, not holding back the wood. Again I am interested if this works for you before the pulley etc is changed. Regards
Danny

 

[Gerard Scanlan]

Hi Danny,

I am picking up the pulley in the morning it needed changing anyway as the drum was rotating way too fast. The plans asked for equal sized pulleys but a 1400 rpm motor and I got a secondhand motor later on which was 2800 rpm and did not think about checking the speed. Then when I did check the speed, I thought so what it will just sand the wood quicker. . I will have a look as reversing the direction of the motor at the same time.

Thanks for the ideas!

 

[whiskywill]

Surely you should feed against the direction of rotation so that the drum is not trying to climb on the work piece.

I think you are correct. I have a Jet 16-32 drum sander and, from memory, when I have been cleaning the abrasive, I'm almost certain that the drum rotates against the direction of the piece being sanded. The friction on the drive belt stops the piece being sent backwards.

 

[CHJ]

In all normal machining processes you feed the workpiece against the rotation of the cutter.
It has to be a very well engineered and correctly set up machine to allow 'climb milling' without risk of disaster from the cutter climbing 'gear wise' across the top of the workpiece.

 

[Gerard Scanlan]

I can't believe it the supplier gave me the wrong size of bushing for the pulley wheel today! So back off there again tomorrow. Looks like I will have to wait another day to see if slowing up the drum speed helps to prevent the abrasive tearing away.

 

[mailee]

Yes I have the small Axminster drum sander and like the Jet the drum does spin pretty fast. It also feeds against the rotation of the drum. I think the idea of having a sandpaper backing would indeed help especially if the loading is fabric backed as it would then even out the load on the paper around the drum. :wink:

 

[Bigdanny]

Hi Gerard,
How did you get on with the sander, pulley, direction of sanding etc?
Have yuou managed to solve your problem?
Cheers
Danny

 

[Gerard Scanlan]

Hello Danny,

Well I got the new pulley installed and then I was snowed under an avalanche of other work, so I won't be able to tinker with the Drum Sander for a day or so. I reckon it will be the weekend before I manage to post the results. Swapping around the wires is a two minute job for someone who knows what they are doing, but usually I have to study the diagram and scratch my head a few times before I swap the wires. :? I reckon I would have a very short career in bomb disposal.
I discovered that the pins in the piano hinges, the hinges that hold the board with the motor, had worked their way out by more than half their length. I just caught that in time . So I have ensured that they can't wiggle out again. I assume that the vibrations from the motor are the cause.

 

[PaulO]

I have tried paper backed and linnen backed abrasives but they both shear off at the brackets after 10 minutes of sanding.
Any ideas where I am going wrong?

Where the paper is clamped it is being forced into a right angle turn, this really concentrates the forces on the paper and weakens it. The rebate for the clamping plate is square sided, try making it a taper/rounded instead. So instead of this |_| go for this \_/ , the smoother the transition over the edge of the rebate the less stress on the sand paper. Should take a copuple of minutes with a chisel and a bit of sanding. You may also want to file the edge of the metal plate into a round profile.

For example look at the clamping rebate here:

 

[Gerard Scanlan]

Thank you very much for the advice about the clamping of the paper. I think I will have a go at that. Unfortunately I did not had time to look at the reversal of the motor this weekend. But rest assured I will post the results soon.

 

[Gerard Scanlan]

The smaller pulley is installed, the direction of rotation has now been fixed, just waiting for the Velcro and velour backed abrasive to arrive. I have decide to give this system a try over the clamping the abrasive. All the plans and instructions recommend this way to attach the abrasive and who am I to argue with a body of experience. Should have some pictures soon (and good news too).

 

[Gerard Scanlan]

Now I have managed to take some new pictures at last.

You can see I have installed a smaller diametre pulley. The velcro is stuck to the drum. Abrasive is attached to the velcro. Test run later this evening.

 

[kirkpoore1]

Gerard:

Old time drum sanders had a layer of felt glued to the drum. This gave a little bit of compression to the drum that might prevent or at least delay the paper tearing off. As far as rounding off/V-ing the slot for the paper clamp, that was standard too.

Kirk

 

[Gerard Scanlan]

At long last my drum sander is finally working properly. The velour backed sand paper stays in place properly on the velcro backing and it can even handle taking off 0.5 mm in a single pass with 100 grade sandpaper. It was always my intention to use this machine as a thicknesser and when I was having difficulties with the abrasives I sort of thought I might be expecting too much from it. Now this appears not to be the case as it does a wonderful job. Thank you all for your input and advice and I hope this encourages other people to have a go at building one.

 

[gasman]

Hello Gerard
I followed this thread out of interest originally (I like problem-solving) but now I think I might want to build one myself. Did you base it on a plan? I know there are some out there but I like the simplicity of yours - outstanding result
Best wishes
Mark

 

[fluffflinger]

Try the link below. It's on my list of projects to build at some point. The link below will lead you through the construction process, video of operation on youtube and plans too.

By far the best resource I've found yet.

If you find a source of the motor please let me know, being rather "careful" it was the only bit that put me off price wise the rest of it is pennies. Excluding the velcro backed abrasives.


http://woodgears.ca/sander/thickness.html

 

[Gerard Scanlan]

Hello Mark,

I followed the instructions and plan on this website.

http://www.rockslide.org/drum%20sander.html

It tells you a lot but not everything.

I just kept digging around until I found someone local who was selling an induction motor cheap. Check out a scrap merchant for the bearings because new they can be as much as 25 pounds each. I did not use axel steel. #-o I would recommend that you get a piece because it will reduce vibration.
I did try to avoid buying the velcro and velour back sandpaper for too long which frustrated me a bit at the finish line. As far as I am aware almost everyone who home builds a drum sander ends up opting for the velcro backed solution. I am still very happy with the results it is giving and the velour backed sand paper is lasting longer than I had hoped it would.

I thiink I did just about everything wrong and had to correct it. I used oak for the frame because I picked up a pack of oak flooring cheap at a DIY shed because it was the last pack on the pallet. It was cheaper than using softwood and I am glad I did use it. The sander is a big beast of a thing and it vibrates a bit so building a really sturdy frame is essential. It is not very fast to use. But it is very accurate. So I often have it running for half an hour at a time. I have also considered building a half size table top version for smaller stuff because it was Jim Byrne's thicknesser (which is actually a drum sander) that inspired me to build one in the first place.
(hammer) Now where did I leave that cheap circular saw...

 

[gasman]

Great links thanks a lot - I particularly like the Pat's drum sander link as the diagrams are so great
However actually Gerard yours is an invaluable resource since, as you pointed out, you had virtually every problem imaginable and solved them all sequentially
I am on holiday from next tuesday and have 3 days before we go away so will start collecting bits and pieces - exciting!
Ebay seems to have a few induction motors - but actually if you search induction motor there are several pressure washers which have 1200-2000 watt motors. If I remember my O level physics, i HP is about 750 watts so I wonder if the induction motor from my old washer (motor fine but holes etc in hose and never powerful enough) would be good enough. What do you think?
Cheers
Mark