Home Made Drum Sander - WIP

[kinsella]

Sorry chaps,
Mixed up my posts. I accidentally replied on my box making jig.
Yes the bar is 20mm thick. Got it off Ebay. Mild steel. Then 36 ply disks all clamped together.

Mike. I'm a tad worried about that myself. I have a few ideas to fix it. Even the knobs when tightened will make the table move slightly. It will be a little trial and error. I have a digital metre that i can use to test if the table is parallel to the rollers. So will be giving that a go at the weekend. If i get inconsistent results, i was planning to add a horizontal bar beneath the table to then span 2/3rds of the width to give more support. I need to work on the knobs also to stop them climbing and falling on each side when tightened.

 

[Tortion-Stephen]

This is a great project. Fantastic ingenuity, really enjoying watching it unfold.

 

[monkeybiter]

What did you use for the central bar? I've seen some people saying certain bars flex too much, but yours looks quite thick.

Judging by appearances any flexibility of the bar should be irrelevant, the necessary stiffness will be provided by the laminated ply stack, however the drawing [and the photo] show a 20mm bar. Or are you referring to a different bar?

Kinsella, I think I'd be a little worried about the table not always rising or staying parallel to the drum. I'll maybe go for a torsion box or thicker board when I copy yours :wink:

 

[kinsella]

Sorry chaps,
Mixed up my posts. I accidentally replied on my box making jig.
Yes the bar is 20mm thick. Got it off Ebay. Mild steel. Then 36 ply disks all clamped together.

Mike. I'm a tad worried about that myself. I have a few ideas to fix it. Even the knobs when tightened will make the table move slightly. It will be a little trial and error. I have a digital metre that i can use to test if the table is parallel to the rollers. So will be giving that a go at the weekend. If i get inconsistent results, i was planning to add a horizontal bar beneath the table to then span 2/3rds of the width to give more support. I need to work on the knobs also to stop them climbing and falling on each side when tightened.

 

[mickthetree]

Ah yes, I hadnt seen the measurement for the bar on the drawing.

Are the bearings SF20?

 

[Ian down london way]

I was looking at that and considering the problem of kick back and driving the material past the sander. It struck me that if one had tyred wheels whose bottom edge were aligned to the bottom of the sanding drum (could be fixed to the side) then they could help to hold the work down and if they were ratcheted internally, so that they turn only one way, they would help control / stop kick back, ensuring the wood was pushed through - by hand. I'm not sure where you can get one-way turning wheels from, and you may need an escape mechanism, to lift the wheels, just in case you do need to pull the wood back out the 'wrong way' - but maybe its worth considering.

Good luck !

 

[kinsella]

Mick
The bearings i used was "UCF 4 Bolt Flange Self Lube Bearing" from eBay, if you put that in the search bar on eBay you will find them. Regarding kickback. I'm expecting it, so when using it, the golden rule will be stand to the side and nobody else in my workshop when in use. I'm very meticulous when it comes to things like that so safety wise, I'm happy enough.

Ian, Regarding the tyre wheel that's a dame good idea and sounds like i could retro fit easy enough. When i get it up and running, i'll add my lessons learnt so that if i had my time over again i'll highlight what i would do again.

 

[gasman]

Apologies if you have covered this already but I also went down this route a couple of years ago and although I do not use it very often mine is invaluable. I made it whilst doing a campaign chest and a photo is in this old post https://www.ukworkshop.co.uk/forums/secretaire-campaign-chest-t76578-45.html?hilit=sander
I used 25mm bar and made the drum in the same way as you did from 3/4" MDF circles which I turned roughly but then finished with 80 grit sandpaper laid flat on the sander bed - that way I was ensured that the cylinder and sander bed were 'parallel' as it were. Does that make sense?
Mine works well - I used adhesive velcro paper and then 120 grit sandpaper - but that takes ages and actually, 80 grit is much quicker and seems not to leave much in the way of scratches - don't really understand why?
Looking really good though
Regards mark

 

[kinsella]

Chaps
I just measured the rod and i did indeed use a 25mm bar with matching flange bearings.
Mark, snap! everything i'm doing is exactly as you say. I just today glued the 80g paper to a section of ply so as to level it tomorrow. The next trick is to see how the table works when i tighten the knobs. it looks like they move it out of parallel. But with the electronic metre i have i know exactly when its not true and i give it a thump. I could engineer something else but i'm going to leave it for the moment to see how it works.

Tomorrows activity is to level the drum.

 

[n0legs]

Would a pair of those gas filled cabinet door stays help in keeping the table parallel?
The come in different weights/pressures 50Nm 80Nm etc.

 

[kinsella]

Not sure how they work but if they are not connected to each other, i can't understand why they would stay parallel.
I think the solution was made by Mike earlier in the post. I think its just thicken up the top to another layers of 18mm ply. ie 36mm top to get extra stiffness.

 

[n0legs]

Not sure how they work but if they are not connected to each other, i can't understand why they would stay parallel.
I think the solution was made by Mike earlier in the post. I think its just thicken up the top to another layers of 18mm ply. ie 36mm top to get extra stiffness.

I was wondering if they would help by applying some upwards pressure on each side/outer edge of the table, not sure.

Probably a thicker table is the answer. What would work really nice though is the geared rise and fall mechanism from a knackered 'lunch box' thicknesser.

 

[kinsella]

What is a "lunch box" thicknesser, tried a search on google and nothing obvious popping up? The other option would be two threaded rods to the sides connected by a chain to rise and fall at the same time.

 

[n0legs]

What is a "lunch box" thicknesser, tried a search on google and nothing obvious popping up? The other option would be two threaded rods to the sides connected by a chain to rise and fall at the same time.

One of these style thicknessers
https://www.machinemart.co.uk/images/li ... 610250.jpg

 

[kinsella]

I see, probably easier to try thickening the top first. The other option is a car jack type mechanism which means i could weld a support to the top. Lets see how thickening goes.

 

[monkeybiter]

I think I'd be tempted to try making a pair of identical cams [mdf probably better than ply] fixed at either ends of a shaft under the rising edge of the table, as the shaft rotates both cams act on the underside of the table and raise it by an identical amount. Guaranteed parallel.

 

[kinsella]

Mike
I see what you mean. An interesting idea and actually simple. The test would be to get both shaft and cam rod exactly parallel.

I gave the bed a few tests today and using my digital angle gauge (http://www.axminster.co.uk/gemred-digital-bevel-box) i'm normaly within 0.1deg of parallel to the shaft. For what i'm doing that will be good enough.

 

[kinsella]

Out of interest, how do you plan on making all those plywood discs perfectly round and true?

If I were doing it, I would get them to be as round and true as possible then use the bed to sand them perfect. So attach abrasive to the bed and spin them with the motor.

Mick

I find myself today remember Mike's advice. I didnt make them as round as possible and thought i'd just leave it when i'm sanding the bed. True it will still work but its taking ages.

 

[mickthetree]

would love to see a video demo once it is running!!

 

[mickthetree]

I really like the simplicity of your design. There are lots of variations of this out there, but they get so over complicated. This should be a simple machine.