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Thickness Sander Design

9K views 19 replies 6 participants last post by  depictureboy 
#1 ·
Initial Thoughts

I have been very impressed by the creativity and ingenuity of the users of this site. One of the best things I have found so far is the discussions on the thickness sanders. All the plans I have seen have been very nice, and very well done. However for my purposes I just don't have the room for something that can't be knocked down. So my goal with this project is to build a Thickness sander that can be knocked down, as well as still be a useful size for my projects and future endeavors.

One of the things I noticed is that most of the sanders seem to be for small parts sanding. Of course my perception of this could be wrong.

So my initial draft ideas are thus:
1. Primary importance is that the whole table be collapsible to some semblance of flatness and not be so heavy that it cannot be moved to its storage location.
2. The sanding drum would be rather large to give a good surface area availability
a. Maybe have the option of several drums with grits of different levels
3. The feed table must be wide enough to allow for most glued panels to fit.
4. The height between the table and the drum should allow the possibility for edge sanding ganged boards of typical thickness(2 to 4 inches)
5. Some sort of automatic feed system, using the same motor as the sanding drum if possible.
6. More options added as needed.

I started my initial sketches in Sketchup. Below is a rough draft of just the top assembly. I am currently working on the motor sub-assembly.

 
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#3 ·
Some points on your points.

2. The bigger the drum (diameter and length) the bigger the motor you would need to power it.
3. You would need a very precision height adjustment for a second drum. Even the different thicknesses of grit would make a difference.
5. Any motor sharing wouldn't work. Look at all the sanders on the market. They all have seperate motors.
 
#4 ·
on point 3, I didnt mean at the same time. I would switch out the drums. Instead of having 2 pillow blocks, the side with the belt would be a U type thing( I have to research it). I could have 2 drums then, one for hogging and the other for fine finishing.

on point 2 I was looking at a 1hp, but maybe that wouldnt be enough, even with different sizing of the pulleys.
 
#5 ·
Here are the specs for my peformax 22/44 to give you an idea.

The motor is 1 3/4 HP
RPM is 1720
Direct connect to motor shaft 1:1 ratio
5" diameter Drum

Circumference = pi x diameter

3.1415×5 = 15.7075 inches

15.7075×1725 (RPM) / 12 = 2258 surface feet/min.

You could use a 2:1 pully with a 3450 RPM 1 HP motor
for about the same thing.
 
#6 ·
Thanks Gary.

Math was never my strong point…Could you explain your calculation for me a bit more? I went to the pulley rpm site and given the numbers you suggested, the rpm on the drum would be 6900. That seems way fast to me. That would be with a powered diameter of 4 and driven diameter of 2. Do I have them reversed?

If I use a 1720 1hp with that configuration the rpms are 3440. Maybe I have my Powered to Drive ratio backwards.
 
#8 ·
I think that you have to two pulleys reversed. The smaller pulley would go on the motor making one rev. of the motor equal to 1/2 rev of the drum.

1720 at 1:1 (direct drive with no gears or pulleys) means that the drum is rotating at 1720 rpm.
 
#9 ·
Hey York,
Yes yours is one of the ones I have studied. I was still going to use the velcro backed roller. I didnt realize a change was really that quick. Maybe i will just keep one roller.

Gary,
In the mechanics of things is there any reason that I couldn't use the same size pulley on each spindle? or even have the larger spindle on the drive shaft? I am sure it has some mechanical advantage having it the way you said, but I am curious as to reasons. thanks
 
#10 ·
You can put whatever size pulley you want where ever you want, but there are advantages and disadvantages to how you do it.

I only mentioned using a 2:1 pully on the 3450 RPM motor to slow it down and in effect would about double the HP at the drum.

You can use a 1:1 pully without a problem. I would just make sure that the motor you use has the HP and RPM you need.

You just need to determine how much performance you are looking for and use the motor/pulley combination to get it.

I provided you what my peformax uses to give you an idea what a commerical unit does.
 
#11 ·
Thanks Gary, I hope I didn't come across wrong.

I am trying to learn the right way to do things. I havent ever had to use pulleys and such, so I dont know alot about them. I dont want to make some fundamental mistake that could be seriously dangerous. I plan on using this for sanding(of course) but also thicknessing until I can afford a planer….

Thanks for your help.
 
#12 ·
Yes, I can change abrasive grades, including remove and re-fit the dust hood, in about sixty seconds

I did have a list of specs of a few commercial machines, but can't find it just now. However, from memory, with a 5" dia drum, a speed of 1700rpm seems to be the standard. Gary's lines up with that and that's what I aimed for. I also used a 1.5 hp motor.
 
#13 ·
Initial Modifications



Well I have added some more features to my table.

As you can see I changes the orientation of the front and rear stiffeners. I have also added the undercarriage for the motor. The undercariage will be supported on hinges that allow the fixture to swivel toward the back of the sander. The platform that the motor sits on will also be hinged so that it will have the necessary tension on the link belt to drive the sander. With Gary's recomendation I will be shifting the position of the motor closer to the edge so that 2 motors can fit on the assembly. One to drive the sander and another eventually for automatic driving of the workpiece.

The part that makes this whole thing work is that the motor will be removable from teh undercarriage assembly using Male threaded knobs connected to threaded inserts on the motors stand. (ie the motor will be attached to a wood platform permanently, but the wood platform will attach to the under carriage with threaded inserts and starknobs. I am thinking this will work pretty good, but I am looking for input into my thought process. Also because Iwill be running 2 motors eventually , I am going to be able to shift the table more toward the center and possibly make it a little bit larger. Right now it is 16.5 inches wide, but with the runners on each side I only get 15.5 for a full piece.

The runners right now are designed as glued strips to the very edge of the bed. I may change this so that they are adjustable along the width of the bed so that they are actually used to guide the piece being run through.

I have placed the table at 34" high which I think should be a comfortable height as that is just above my wrist level when my arms are at my side.

Let me know what you think and any suggestions you may have. thanks
 
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