Drum Sander diy pre build question.

[TRITON]

You can make one for your lathe, it’s ideal as it runs fairly slow and is pretty solid, you just make a tilting table underneath your drum which you mount between the centres. Use a section of soil pipe or similar to make a good dust cowl or the mess is unbelievable

+1
Utilizing the lathe solves a number of problems, namely having a variable drive speed, with torque and what i think is more important, having both ends parallel to each other. Theres a flat bed to mount the base on and it is only really the drum and base that you need to find storage for.

 

[sometimewoodworker]

I think your shafting is too small. My 22"/560mm drum (5"/125mm diameter) drum sander has a 1"/25mm shaft. It is an overhead type.

Pete

While you could be correct on the size being a little small depending on the material used for the drum and length it’s probably perfectly OK as it’s an under table drum so it’s only function is to hold and spin the paper while maintaining rigidity along the length.
This is different from your machine as your roller also maintains pressure on the workpiece, so needs considerably greater strength.

 

[sometimewoodworker]

Stumpy Nubs combined both types of sander by having the v sander on top and thicknesser underneath a single drum. I have no idea what compromises this would bring in, but it's a completely over-the-top build, so why not try it?

I don’t want to poke holes in the work of the stumpy nubs channel, he is a far more accomplished woodworker than I am, however his machine is an overhead drum machine that can be used for under drum work.

It isn’t as good an under drum machine as those using Velcro to attach the paper. It does look as if he could, with a small number of modifications swap out the glued on paper rollers for a Velcro one for the best under table roller use.

I also note that James said in that video thar his main use for the machine is as an under table unit (1:20 in the video) so that is certainly a point to think about, it was certainly a consideration when I decided on my machine.
if I had unlimited money I would think seriously about getting an overhead sander. I have plenty of space but no pressing need at the moment.

 

[Inspector]

While you could be correct on the size being a little small depending on the material used for the drum and length it’s probably perfectly OK as it’s an under table drum so it’s only function is to hold and spin the paper while maintaining rigidity along the length.
This is different from your machine as your roller also maintains pressure on the workpiece, so needs considerably greater strength.

Since mine is only taking 0.1mm to 0.3mm a pass unless using very coarse paper 40/60 grit and slow feed I believe you’re wrong. It is all about stiffness not strength. Take a 2’ long 17mm rod and set it between 2 blocks and see how easy it is to deflect. Do the same with 25mm. Up to you though.

Pete

 

[TheTiddles]

Rigidity isn’t a thing, rigid is a theoretical condition. You want stiffness, diameter and material will give you that (and the first is way more effective unless you’re going to use marshmallow as the material).

A small drum will need a much faster angular velocity to give the same cutting speed with a reduced surface area that will minimise heat dissipation and ability to shed embedded material whilst maximising pressure to increase the chances of burning and deflection.

In rolling mills where they want small rollers for higher pressures, they’re backed up by several rollers of increasing diameter to take the load called cluster mills.

Aidan

 

[sometimewoodworker]

Since mine is only taking 0.1mm to 0.3mm a pass unless using very coarse paper 40/60 grit and slow feed I believe you’re wrong. It is all about stiffness not strength. Take a 2’ long 17mm rod and set it between 2 blocks and see how easy it is to deflect. Do the same with 25mm. Up to you though.

Pete

As I mentioned the stiffness is a vital function of the overhead drum and you are using that in your machine with the work pressing on the drum, it doesn’t matter how little you are taking off apart from probably slightly reducing the stiffness requirement If you are building it yourself.


However in an under table roller has zero pressure on the roller so it’s conceivable that a cardboard roller (I don’t know if anyone has tried that) would be more than adequate in one of those.

The point is not how easily the rod can be deflected when pressing it down (there is NO pressure) but does it deflect when spinning. If the answer is no then it’s good for the job. if the answer is yes then you need something better.

Your reasoning is faulty. (Because my truck has 24 gears your EV can't work with just 1) different us cases, different needs.

Also FWIW my machine has a 16mm (probably a fractional inch really) shaft with about a 100mm drum on it.

 

[sometimewoodworker]

A small drum will need a much faster angular velocity to give the same cutting speed with a reduced surface area that will minimise heat dissipation and ability to shed embedded material whilst maximising pressure to increase the chances of burning and deflection.

An excellent explanation and perfect for an overhead drum machine.

Still mostly accurate but a little less important for an under table drum machine. As the paper has an air gap underneath so there is little to no heat buildup and zero deflection.

There is a 457mm version with a 50mm drum, the benefit is a smaller opening in the table, the down side is the reduction in paper you can get on the drum.

 

[TheTiddles]

An excellent explanation and perfect for an overhead drum machine.

Still mostly accurate but a little less important for an under table drum machine. As the paper has an air gap underneath so there is little to no heat buildup and zero deflection.

There is a 457mm version with a 50mm drum, the benefit is a smaller opening in the table, the down side is the reduction in paper you can get on the drum.

Zero deflection = zero load

Drum sanders have dust cowls and 4” hoses funnelling vast air flows over them, they still get hot.

The best of luck with your endeavours

 

[TRITON]

if I had unlimited money I would think seriously about getting an overhead sander.

Along with everyone else here

I'm actually tempted to purchase one, although the price of them has increased quite a bit, i think its one of those handier machines that would make life considerably easier.

 

[sometimewoodworker]

Zero deflection = zero load

Drum sanders have dust cowls and 4” hoses funnelling vast air flows over them, they still get hot.

The best of luck with your endeavours

You are confusing overhead and under table sanders and the way they function. For overhead you have the information and the way they function correct, though I think your airflow dynamics may not be exactly .

the under table, Velcro attached work differently there is no need for deflection as there is NO load ( or very little load) on the roller. The paper floats off the roller allowing an air cushion, the deflection of the PAPER is compressing the air cushion so while there is very slight air pressure down it also travels sideways.

is there any deflection of the circular path of the paper? Of course.

Is there any heat generated? Of course but the paper is air cooled.

Is it noticeable? No it isn’t

is it measurable? Probably, I’ve never noticed any difference touching the roller after using it, but a tiny increase wouldn’t be noticeable.

Does the paper load up with melted finish? Never that I have seen.


this is drastically different from overhead models where the paper is squeezed between the roller and work this compression the cause of the vast majority of heat generation. The cutting action of the paper produces very little heat.

 

[clogs]

it's been said that to make a sander with power feed is expensive.....!!!!
I plan to use a car type wiper motor for the power feed drive.....
it doesn't have to be fast or very powerful......your not taking much material off......
cant wait to get started on mine......

interesting about the construction of the over head roller......weight......

 

[Gerard Scanlan]

I built a drum sander without a power feed and I discovered it is a tricky machine to use without a power feed. You need to take lots of passes with only a minimal amount of pressure on the timber you are sanding or it will leave ridges. A power feed is a luxury but perhaps a really useful one.

 

[Sachakins]

I think your shafting is too small. My 22"/560mm drum (5"/125mm diameter) drum sander has a 1"/25mm shaft. It is an overhead type.

Pete

I was only going to go to 14" Or 16" wide. Do you think it will still be too thin?

 

[NickDReed]

Been there, done that, ìts on my 12" **** sander...

That made me wince!

And congrats on the 12"s

 

[sometimewoodworker]

I was only going to go to 14" Or 16" wide. Do you think it will still be too thin?

My under table sander with a 30” drum has a 16mm shaft and it is plenty big enough. Size the shaft on the bearings you can get from 16mm and up.

I hold no opinion on the overhead sizes.

That made me wince!

And congrats on the 12"s

It’s a quite a bit smaller now.

 

[Trainee neophyte]

PVC vs ply vs mdf cylinders - anyone have any thoughts? Olive picking machinery tends to have exactly the right Pvc cylinder arrangement, so I can get bearings and shaft fixings without problem, but I have heard talk of Pvc causing static buildup and doing odd things with dust: is this true? Would it be better to make one from ply? A stainless steel machined cylinder is probably not going to come in under budget, so looking for the diy option.

Another local habit is to roast an entire sheep on a spit - you can buy slow, hight torque motors for turning the spit on your barbecue - typical Chinese tat but cost €15. They turn at perhaps 20 rpm - would that work as a feed drive? This sort of thing: https://www.amazon.co.uk/s?k=barbecue+motor&tag=duckduckgo-20&ref=nb_sb_noss

 

[Ttrees]

I was going to build one years ago, but found hand tools just in time.
Do you folks not get serious gumming of the paper?
That was the biggest gripe that the luthiers on the OLF had with them at the time.

 

[TheTiddles]

I was going to build one years ago, but found hand tools just in time.
Do you folks not get serious gumming of the paper?
That was the biggest gripe that the luthiers on the OLF had with them at the time.

Some, depending what you put through it, like a planer head you have to have a defect all the way around for it to stop working on that line, so that’s where a big diameter helps and an abrasive cleaner stick.
Sanding/scraping down an entire table’s worth of veneer by hand, would not be my idea of fun!
Aidan