In this article I'll will be discussing how to make a DIY belt sander. Actually I never had an intention to make one but for my upcoming layer speaker project this sander was very essential. So I thought why not to turn this into an article. This is a very simple version of a belt sander but its very useful and rigid in construction. It can sand metal, wood, PVC and lots of other materials. Also you could adjust the length between the two rollers with the help of the bolts provided, which makes the sander adjustable to all belt length and thus making it more versatile to all applications. One of the rollers (driver roller) is attached to a drilling machine through a long bolt which makes the second roller (driven roller) to rotate when the belt sand is placed over it. It would be better to watch the video first and then the article to get the whole picture. OK now lets discuss the build...
Step 1: Making the Wooden Roller
The wooden roller is the most important part of the sander since it's this roller on which the belt rotates. We need two of this rollers to create a rolling belt drive system. The rollers are made from circular sections of plywood which is fixed together using brad nails one by one to form a stack of plywood which finally forms a roller. These circular sections are cut using a standard hole saw of 44mm attached to a drilling machine. The number of circular sections needed will depend on the thickness of the plywood section and the width of the belt. Through out the project I have used only 12mm plywood sections. The sand belt which I'm using is having a width of 10cm, so 9 circular sections cut from a 12 mm plywood would be enough to accommodate the belt. since we need two of these rollers, we need a total of 18 circular sections. While we are making the circular sections using a hole saw a central hole would be already created if we are fixing a drill bit it the hole saw attachment. This central hole in each section could be used to drive in a shaft through the center to support the rollers. The shaft which I refer is nothing but a long bolt which is about 4 cm longer than the roller length in order to accommodate the extra supporting block at both ends of the rollers. After cutting the 18 sections Its time to make it into rollers. For the perfect alignment its always better to first insert the bolt through one of the circular section then place the second section on top of the first through the bolt. You could also apply some wood glue in between these section for additional strength. after placing the second section on top of the first secure the two sections using two or four brad nails. Likewise repeat the process to form the 2 roller each consisting of 8 sections. After its done if there is still small surface imperfection then we could attach these rollers to a drilling machine to rotate and placing a piece of sand paper at the surface we could make the surface even and smooth which is very essential for the smooth running of the sand belt over the rollers.
Step 2: Making the Holders of the Rollers
The holders fixes the rollers in place and keeps a clearance with the bottom platform on which everything is arranged . This clearance is essential for the easy insertion and movement of the sand belt. Since we have two rollers obviously there should be two holders also, out of which one holder is fixed and another is movable. both the holders are exactly the same in construction. The holders are made from 3 pieces of plywood blocks where the small two blocks act as the end supporters and a longer block at the bottom holding this two side blocks vertically in place. The side blocks are drilled with a hole on the flat side, make sure that holes in both blocks are placed exactly at the same vertical distance. This is the hole through which we place the bolt containing the roller is fixed. The structure is done by piercing some brad nails from the bottom block to the side block placed vertically above the bottom block. After its done you should end up with an upward faced C structure. One important thing to note is that after fixing the first block don't forget to take a 2 cm longer than the horizontal roller length, since we are fixing the rollers after the two end blocks are fixed. Also make sure that you have given sufficient vertical clearance for the roller to roll freely and for the sand belt to rotate over it. In my opinion a clearance of either 1.5 cm or 2 cm would do the job. This completes the first holder. For the second roller i.e. the moving roller proceed as same as above but wit a small difference. The bottom plywood block is taken a litter wider than the rollers. The idea was to slide this entire assembly consisting the 3 blocks and the rollers on the final platform through the slits provided on the platform. Two bolts are inserted trough the bottom block which then goes through the slit at bottom platform and could slide the entire assembly through the slit giude. After fixing a convenient position the bolts could be then tightened with the help of nuts. Also make sure that the bolts are inserted with its head portion at the bottom of platform and thread through the C shaped holder and thus we could tighten the holder from the top itself. This completes both the holders.
Step 3: The Base Platform
The base platform is the platform on which all arrangements are fitted. The size of the platform depends on the size of the drilling machine and the maximum length of the belt that the setup could be used for. In my personal opinion using a belt length more than 1 meter is little bit on the higher side. I'll tell you why, since the belt is supported only on the two rollers no matter how much you try there will be a small looseness of the belt as the belt length increase. This creates a weak point that sanding in the middle part of the belt could sag the belt a little thus imparting a curved sanding of the required surface rather than a perfectly flat surface. So what I'm conveying to say is that suppose we are tying to sand small part then using a shorter length belt could do a lot of advantage to the surface finish. So If we are limiting the maximum length of the belt to 1 meter then we need at least half a meter of roller to roller distance, since when the belt is fitted around the rollers half the span of the total length of the belt is obtained, half meter above and below the roller together forming a single belt. So to round off take the length of the base platform little bit above half meter say 70 cm. while the width of the base plate is taken little bit longer that the horizontal length of the drilling machine. The one that I'm using is Bosch GSB 600 RE which has a length of 26 cm so to round off I took 30cm as the width of the base plate. After cutting the base platform to the required size its time to fix the driver roller. this is the roller which is directly connected to the drilling machine. Thus it has to be fixed straightly and properly. I used some brad nails to fix the roller and the support system to the base platform. After fixing this roller firmly two slots perpendicular the roller kept at a distance. is cut on the base platform. this is to insert the bolts which would hold the second movable roller.
Step 4: Fixing the Drilling Machine
As we discussed in the above sessions, it is the drilling machine which powers the roller (driver roller) and rotates it on its axis supported by the end plywood blocks. Since we are tightly attaching the belt around the driven and the second roller (driven roller) it forms a belt drive system and thus rotates the second roller through the rolling movement and friction of the belt. thus obtaining a continuous rotating sand belt on which we could perform the sanding operation.
The next main thing is fixing the drilling machine. I have seen several tutorial video in which the drilling machine is not at all supported or fixed to the platform. This could be very dangerous if we are applying a much higher sanding force to the belt which is often required for sanding wooden block or things with more size and mass. The reason is that while we are applying the resistive force on the belt for the sanding operation this opposes the rotation force of the drilling machine, thus leading to the development of a reverse torque which would try to rotate the whole drilling machine. It will be less significant while sanding lesser mass objects at a much lower speed. But If the rolling speed and mass of the required object is comparatively high we should restrict the motion of the drilling machine by properly creating a locking mechanism for the machine which is discussed in the session below.
Constraining the motion of the drilling machine
There is no specific arrangement for fixing the drilling machine in place. The only thing to consider is that the drill should be perfectly straight once attached to the bolt of the driver roller and all the freedom of motion of the drilling machine should be constrained. after collecting some small pieces of plywood blocks, try inserting to the places where the drilling machine should need some support. I'll discuss what I have done for the support. after tightening the bolt to the chuck of the drilling machine I began to align the drilling machine to be straight to the bolt, this provides a very smooth uniform running of the rollers. the height of the drilling machine is matched by inserting the plywood blocks in place. just before the rotating shaft of the drilling machine there should be a circular extension to support the shaft. This circular section is the perfect place to start. Try inserting blocks beneath this circular cross section to make the support and aligning the drill straight. Then go for the handle of the drilling machine there you could attach a removable support to constrain the backward motion. For the removable support you could make a guide way track with two rows of plywood pieces stacked one on top of the other on both sides so that another plywood piece could be fitted width wise. First the drilling machine is inserted and fixed with this removable piece of plywood. An angle shaped structure is also created at the place of trigger of the drilling machine. After fitting the drilling machine the position for the trigger is marked and a nut is fixed at the position of the trigger so that when a bolt is inserted and turned forward it could adjust the speed of the drilling machine. separate picture of this assembly is added with this session .
Step 5: Fixing Sand Belt and Operating the Belt Sander
So things are almost complete. The last thing to do is fixing the belt between the rollers. For this the belt should be continuous and we are using some upholstery resin and cloth at the back side of the belt (i.e. non abrasive side) to form a single belt. One thing to note is that while sticking the two ends of the belt together they should be cut in a way that they interlock in a slanting cut position. This is achieved by placing the two ends on top of another then cutting out a slanting piece from the edge. Then fold the two edges in reverse i.e. the abrasive side up. and join the two equal and opposite section with upholstery glue and cloth at the back. The reason why this procedure is done is to make the forces acting on the joint to be applied on much larger area of section, if this slanting cut is not provided then the full force on the belt will be applied to a single line of action, thus making that section more vulnerable to failure. After sticking the belt with adhesive place some weight (i used brick) on top of the joined section and this strengthens the bond and thus we could get a perfect and continuous belt with no discontinuities or projections.So once every thing is done we could start running the belt by powering the drilling machine and slowly turning the bolt for trigger speed controlling. If our work demands a much higher pressure to be applied on to the belt then we could do that by sanding it on the place of rollers like what I have done while sanding the rusted metal knife in the intro of my video. While seeing the results I'm very impressed and it was on the high side than my expectations. the shiny knife after the sanding was the best example for it. Also it works very well on wood also. Like I mentioned before the sander was actually designed to sand wood and it also turned into good results. So this is it guys.. let me know your thoughts and suggestions in the comment section below. Thank you for your patience to read the article.