Made a drum sander attachment for wood lathe (Pic heavy)

[Ed.]

I made a large wood lathe several years ago and had always wanted to build a drum sander, but due to very limited space left in the shed, I decided that my best option would be to make one as an attachment to the lathe rather than having another separate piece of machinery that would take up even more room. It also meant that I could save on the cost of an electric motor and associated bits as the lathe had more than ample power to power it. I do have a 15” wood thicknesser but some of the hard woods I have, contain a knotted grain which ends up with a bit of tear out, so this attachment should reduce that nicely.


Pic 1. Found a very old and very rusted trailer axle, cut off the ends and put it in the metal lathe to clean it up.


Pic 2. Machined the axle down to 35mm to clean it up.


Pic 3. Found an old flange in my scrap pile that was not going to be used for anything else and welded it to the shaft.


Pic 4. I stuffed up the machining and took off a smidge too much metal for the bearing so knurled the end to build up the difference.


Pic 5. I had a 2 step pulley lying around so turned one step down to make it into a double pulley. Probably not necessary but at least now the belt definitely isn't going to slip under load.

 

[Ed.]

Pic 6. Tapping the pulley to fit onto the shaft.


Pic 7. Welded up a bed frame from some rusted 50mm SHS that I had salvaged and had cleaned it up a bit. There is still one cross member that I hadn't welded when I took this picture, they will stop the bed from flexing when the timber is under the drum getting sanded. There is a sheet of 19mm Form ply that is the bed material and the slick surface should help to stop the conveyor belt from sticking and wearing away the belt.


Pic 8. Welded up 2 height adjustable support posts for the bed. They can be adjusted for variable heights in case I would like to sand something reasonably thick.


Pic 9. Cutting up the disks on the bandsaw for making the drum out of 1/2" plywood. I had pre drilled the centre hole with a hole saw and the shaft fits in through it.


Pic 10. Liberal coating of PVA glue over the shaft and ply wood.

 

[Ed.]

Pic 11. This is the completed drum stack with the excess glue brushed over it all to help soak into the ply and seal the seal it for machining.


Pic 12. After a first pass on the metal lathe the ply drum was coated coated with a couple of coats of polyurethane floor paint so seal off the ply further. This left a fairly prickly surface once I got down to the actual ply surface which offers great grip to the cloth backed sandpaper I used for the drum. A stainless screw and a washer at each end holds the sandpaper to the drum.


Pic 13. Got some hardwood timber and partially drilled a hole in it with a hole saw for the bearings to sit in it. This is the first time in my life that I had used timber for this purpose but I figured that since the conveyor belt rollers only travel at only 1 rev. per second there wasn't a need for anything more substantial and making them out of steel would take much longer.


Pic 14. Made a feed roller out of some thick steel pipe. Welded some caps on the ends and a stub for the bearing and then put a knurl on the roller surface to grip the conveyor belt. The other end roller doesn't have a knurl on it as it will just spin on the bearing and doesn't need it.


15. This is how the knurl turned out. I didn't have a large enough scissor knurl tool to go right over the top and bottom of the roller so just got the largest one I had and just pressed it into the sides. Seemed to work out OK.

 

[Ed.]

Pic 16. As I was using a 2 speed 12V car windscreen wiper motor, I had to make a new sprocket holder to fit the motor shaft, so I got a small piece of 30mm round and drilled a hole in one end and then threaded it to connect to the motor, the other end I machined it down and then threaded it to the sprocket hole size and then ground down one side of the thread for the sprockets keyway, and then just used a nut to hold the 11 tooth sprocket on.


Pic 17. The feed roller has an approx. 80 tooth sprocket attached to it and both sprockets come from a small electric bicycle parts supplier. I had to make a small adapter to connect the sprocket to the drive roller.


Pic 18. The dust cover I made by cutting down an old pool filter that I picked up from a recycle yard and it had been laying around for a good 10 years in my yard, so now was the perfect time to use it. I cut it down to the length I needed, took out a section from the middle as the diameter was too wide. Stuck it into the oven at about 200C (when the missus wasn't home, I hope that she doesn't end up reading this post)and then when softened up enough, pushed the sides together to the right diameter. Had a bit of tube left over so slit it on one side and flattened it to make the end supports.


I welded the end supports and a dust extractor connection using a hot air welder. The drum is bolted to the sided of the wood lathe by a couple of bearing holders I had made and welded up and there is also a spacer on the shaft between the bearing and the drum, wasn't sure what the final size of the shaft would be so just made the shaft oversize and took up the slack with the spacers. They are locked on to the shaft by a couple of grub screws.


Pic 19. Dust extractor cover bolted to the other side.


Pic 20. Dust extractor cover bolted to a small bracket for clearance of the belts. The double pulley screws on to the spindle of the wood lathe (M30 x 3.5mm) and locked in by a 14mm socket cap bolt bolted to the end and also a grub screw in the middle of one V.

 

[Ed.]

Pic 21. This is the fine height adjustment, is a threaded shaft that I welded a flat bit of steel to the ends and drilled a hole in them. It has a knurled round knob for adjustment and a locking nut to set the height. The bed has a removable cross piece of SHS across from one side of the bed to the other and this bolt is connected to it. I made the bar removable to enable the conveyor belt to fit above it and below the bed and still give me a single point for fine adjustment.


Pic 22. This is the control panel of the wood lathe, generally the lathe will run up to about 1160 RPM full speed on the lowest gearing but I can change the lathes internal pulleys to get 2166RPM and then slow it down to a slower speed using the VSD. But I must admit that it is a bit of a pain to change it, so I am thinking that it may be easier to make another but larger diameter 2 belt pulley for the lathe spindle as it would be much easier to change with a couple of longer belts, but I will see how it performs before I do that. The drum is about 135mm wide and so far seems to sand OK at its current RPM's but probably could do with a faster RPM.


Pic 23.

This is the control box for the conveyor belt which has 2 speed settings. The switch box has a forward/reverse switch, an on/off switch plus a 10A fuse, it is connected to 2 x 12V 18A UPS batteries which will have a battery charger attached to them to charge up the batteries when the drum sander is working. The conveyor belt travels at 170cm/minute on slow speed and 228cm/minute on fast speed on an unloaded belt. The panel on the left is the motor overheat control which switches an additional fan on and off should the motor heat up past a set temp. Also another emergency stop switch.


Pic 24. Conveyor control box with bolted speaker magnet to the back, this enables me to place the control box to either side of the lathe, depending on which is more convenient.


Pic 25. Machined a larger pulley to spin the drum faster. This increased the drums rotation speed to an unloaded 1830RPM from the original 1130RPM, wood is being sanded much better now.

 

[Ed.]

Pic 26. This is a board being sanded with a new 40 grit paper, very rough finish but fast wood removal. Bearing in mind that this is Ironbark timber so quite a hard wood to sand down to depth.


Pic 27. First strips glued and clamped



Pic 28. Re-sawn strips and glued again



Pic 29. End grain Iron Bark cutting board sanded and oiled


Pic 30. Plain Iron Bark cutting board sanded and oiled


Whilst doing the end grain cutting board I had 2 slight accidents, as the drum sander isn’t finished yet by not having a conveyor belt, I had to push the end grain cutting board into the drum using 2 push sticks on either side of the board, as the end grain got sanded it got hot and then it started to develop a bulge in the middle.


This forced the board against the drum more, more heat and bigger bulge and then it grabbed against the roller and skewed off on an angle, one of the sticks slipped off and you can guess the result, the roller threw it out back towards me in a spit second at a high speed hitting my thigh muscle with one of the corners.


So after saying a few choice words (actually quite a few, I waited a bit till the board cooled down a bit and tried again, and yep it did it again almost hit the same spot on the leg. Though looking on a brighter side it could have hit me elsewhere, 5 inches to the left and I would have been talking with a very high pitched voice for a while. Anyway I finally got them finished using very light sanding passes, they are now flat, level and oiled with Paraffin oil and they are now in the kitchen.

My leg is quite stiff, painful and very swollen and I am just waiting for a very large bruise to show. The end grain board weighs about 3.5Kg so it had a lot of mass.

I have machined and knurled a full width heavy metal roller which I am going to somehow add to the feed side (about 15Kg) which will roll on top of any wood I am feeding the sander by pressing the wood against the grit covered conveyor belt and I am just waiting for 2 anti-reverse bearings to arrive from overseas, also waiting on the conveyor belt to be made (once I have sufficient funds) hopefully this will slow down/stop any timber being thrown back out.

 

[Ed.]

Finally finished off the drum sander today, the conveyor belt arrived yesterday and so I pulled the whole lot apart, gave it a lick of paint and a few touch ups. Fitted the belt today, reassembled it and gave it a few test runs.

It took a couple of goes to adjust the belt so that it tracked straight and had the right amount of tension as it slipped a little bit a couple of times. But it seems that all the gremlins are out now and the gritted belt seems to have over come the issue I had with it throwing out the timber towards me if it became jammed. I had finished off the heavy roller which I was going to use to press the wood down to the conveyor belt but from a couple of tests I did, it seemed a bit superfluous now and so I didn't fit it.
Once I do a bit more sanding work on it I will decide if it needs to be fitted or not.

Made a short video of it working and it is now on Youtube

https://www.youtube.com/edit?o=U&video_id=wjL-Xebulq4

 

[zx9]

Cool, at first I did not understand why you making it so big / wide (I am not a wood worker) but seeing the picturs of the finished wooden blocks I now see why.

Youtube video link not working BTW.

 

[Ed.]

Actually I built it that size in case I decide to do some coffee tables and or benches which usually are about 50-60mm wide which this one will do, but it won't do a table top as they are usually about 90cm. I suppose if I needed to build a table I could always pay a furniture company to sand it down for me or alternatively do it in two halves.

 

[Ed.]

Try this link

Oops, just noticed that I put "50-60mm wide" in the above post, should have been 50-60cm wide.