Thread: Building a thickness sander - WIP

Originally Posted by Black Ned

Howdy tdrumnut,
any chance of you providing the cost of items used as you go to give an indication of approximate cost we could expect to pay if we copy your unit? That is if you do not have a problem with us forumites pinching your design and brains!
thank you, Ned

Hey Ned firstly I am copying someone else's design with a few mods so I am only too happy for anyone to use material from this WIP and with a bit of luck we can all learn something.
Secondly I will be posting costs as they occur. The only reason there has been none so far is that Today was the first actual cash outlay that I have made. What did I buy? I hear you ask.
Well here goes.
Power switch $4.00, Bearings X 2 $35.27, pillow block housing X 2 $16.19, Pulley 3 1/4" $20.83, Pulley 2" $12.40, Key steel $2.63, 3/4"steel shaft $8.00 Total so far $99.32

Yet to be purchased is the velcro and the sand paper and casters should I wish to make it mobile. So hopefully I will get out of this for under $200.
Note that I have not included the cost of a motor as I found one on an old compressor that was buried in the back shed and that I forgot was even there.

Originally Posted by tdrumnut

Correct Swift775
My roller will have a finished size of 75 - 80mm. I am at this stage looking at using hook & loop (velcro) sand paper which will in turn add a couple of mil to the finished size, but until I have trued and sealed the drum then attached the velcro and sandpaper the exact size will be a mystery. With either combo the actual speed of the drum will be a bit lower than the actual speed of the of the pulley. Whether the difference in speed becomes an issued I am unsure but I have read where others similar builds have ended with the drum speed at around the 2000 rpm mark and they have worked. Food for thought I suppose.

With an 80mm drum diameter, I'd go with the highest speed, I reckon. My commercial drum sander has a drum diameter of 125mm and speed of 1725rpm, making a surface speed of 677 metres per minute.
At 1850rpm, your 80mm drum would only give a surface speed of 465 m/min, so even faster would be better. If you can get it spinning at 2000rpm, that's a little better at 502m/min.
To achieve 677m/min, you'd need to spin the 80mm drum at 2693rpm.

Originally Posted by Hermit

With an 80mm drum diameter, I'd go with the highest speed, I reckon. My commercial drum sander has a drum diameter of 125mm and speed of 1725rpm, making a surface speed of 677 metres per minute.
At 1850rpm, your 80mm drum would only give a surface speed of 465 m/min, so even faster would be better. If you can get it spinning at 2000rpm, that's a little better at 502m/min.
To achieve 677m/min, you'd need to spin the 80mm drum at 2693rpm.

Thanks Steve, you have now got me thinking that maybe I should increase the drum size to 100mm that would get the surface speed closer to the commercial ones, and it would be a lot easier to do it now than later (I was going to glue up the discs to the shaft today but will think about it over night now.

Originally Posted by tdrumnut

Thanks Steve, you have now got me thinking that maybe I should increase the drum size to 100mm that would get the surface speed closer to the commercial ones, and it would be a lot easier to do it now than later (I was going to glue up the discs to the shaft today but will think about it over night now.

Sorry to have rained on your parade, but I agree with you that a larger diameter is probably better than higher speed. A 100mm drum @ 1850rpm is 581 m/min - not bad at all. At 2000rpm it'd be 628 m/min.
I'd say that it's probably easier to wrap the sandpaper on the larger diameter. Also, the larger surface area will help keep temperatures in check as well as providing better wear so that your paper will last longer.

Originally Posted by Hermit

Sorry to have rained on your parade, but I agree with you that a larger diameter is probably better than higher speed. A 100mm drum @ 1850rpm is 581 m/min - not bad at all. At 2000rpm it'd be 628 m/min.
I'd say that it's probably easier to wrap the sandpaper on the larger diameter. Also, the larger surface area will help keep temperatures in check as well as providing better wear so that your paper will last longer.

Steve don't be sorry mate I really appreciate the input. I've just been out in the shed and cut up some new discs. I only had a 111mm hole saw and that wasn't to sharp so I just scored the discs to get the shape of the circle and centre hole, then cut them out on the band saw and drilled the 3/4" hole for the shaft. Once it is trued up, sealed and has the sand paper on it will probably finish up around 107mm. I have dry fitted them onto the shaft and to be honest it actually looks better as well, so thanks for your imput.

Keep in mind you can easily work out the speed your machine is turning at.

Get a strobe tachometer disc, print it out, mount it at a bit of mdf or something, and put an overhead flouro globe near it.

There are more details at Very low cost way of measuring tool speed.

Will there be anything carrying the work through?

This video puts the sander at an angle, but the same would work if the "belt" underneath went at an angle ...
(Plus it's got a real 80s vibe to it )
Cheers,
Paul

Originally Posted by pmcgee

Will there be anything carrying the work through?This video puts the sander at an angle, but the same would work if the "belt" underneath went at an angle ... (Plus it's got a real 80s vibe to it )Cheers,Paul

No auto feed on this one Paul, the timber will be put through the sander using a thin flat push stick.

what a great idea, I love it

Ok so I have purchased most of the components required to complete the build (see post #17) at a total cost to date of $99.32. Now its time to start putting this thing together. The pics below will show the progress but first I will explain how it went.
Firstly I have already made one major change (thanks to input from Hermit) and that is the drum size. I remade the drum and it will now have a finished size of 105mm or there abouts. This was done to give the sand paper better surface speed and it actually looks better as well.
So the new drum is all glued up and epoxied to the 3/4"shaft, has the bearings fitted and is sitting nicely in the pillow blocks.
I have also wired up the switch and fitted the motor platform and the table, both using piano hinges for stability. Nothing has been bolted down yet as I still need to fit in the table height adjuster.
I have decided to run a piece of angle iron under the table. The reason for this is 1) to stop the screw thread from the adjuster digging into the bottom of the table and 2) I think this will assist in helping to prevent table twist which can occur when the height adjustment is made in this fashion.
I have also ordered the velcro and sand paper from the Sandpaper Man. I have calculated that the new drum will require around 2.2 metres of 76mm sandpaper and have ordered 5 metres each of three grits (120, 180 and 240) wicch will give me 2 wraps of each grit and a bit left over. The total cost of this was $89.72 incl delivery.
So now the total outlay so far is $189.04.
Just in case anyone is wondering why the on/off switch is mounted on the left hand side, it is because I am right handed and as I will be pushing the work through the sander with my right hand the left can be ready for a fast switch off should the be any mishaps (god forbid).

It's looking pretty good. Nice job.

Righto then, there has been a little more progress on this project so here goes. The table, motor and drum have all been attached and it all runs well. I spent the morning truing the drum to the table and once that was completed sealed the drum with Feast & Watson floor sealer in preparation for the velcro to be attached to the drum. There is still a bit to do but I feel that I am on the home stretch. Next is to make a handle and lock mechanism for the table adjuster then I will start on the dust collection. One thing I have discovered this contraption is heavy and and such will require casters to mahe it mobile so that will have to be done as well. The following pics are 1. the pulley assembly, 2. the motor and drum assembled , and 3. the drum after truing and sealing.

how adjustable is the bed, it does not look like you can take a big range in timber sizes?

First off I have to strongly register my disapproval of this "saying I will do something ... and then doing it" carry-on.

Frankly, it's making us look bad - and if the other halves ever get wind of the concept ... transformed of course into "she saying we will do something ... and then me doing it" ... we're all completely stuffed.

Originally Posted by tdrumnut

I spent the morning truing the drum to the table

How, sir, how?! Details please.

I had a thought that if you knew you had the axle parallel to the table, you could stick sandpaper to the table and get the drum to wear itself even.

Paul