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Too much finishing!

L

lorn

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Jan 25, 2006
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Hi there,

I'm an amature box maker who's recently been getting quite a bit of work from family/friends. So much so that it's been difficult keeping up with the workload and I've been trying to cut time down where I can. The boxes are made out of rather exotic wood (bloodwood, ebonies, etc.) and one of the most time consuming parts of the project is finishing. Currently, I hand finish each box, starting from 1-200 grit and stepping that out to 1600-2000. I use no polish or wax as these woods have an excellent natural oil, and they truly look beautiful when complete. Problem is, is they take forever to finish.

My idea is to integrate a belt sander to help speed up the process. From my intial searching it doesn't look like there are many manufacturers who make very fine grit paper as belts. I'm also a bit concerned with the speed of the motor causing problems... would be nice if I could find a model with a speed control mechanism on it. If anyone has any input on this problem of mine it would be hugely appreciated... also if anyone has any experience in non-hand production type finishing I'd really like to hear your thoughts.

Best regards,
Lorn Davies
 
Flat worker or turner--no problem

Lorn, welcome to the AAW site be you flat worker or turner. If you are a flat worker then we look upon you as a future turner. If you're a turner you are aware of the pleasures thereof.

In answer to your question: I seldomly, if ever, use a "finish" on Mountain Mahogany. It's similar in density to ebony. I have used Abralon pads on a backing plate mounted on a die grinder. Abralon pads go as high as 4,000 grit.

I have also used Jeweler's rouge, both white and red, on a buffing wheel. One needs a light touch for no longer than 20 sec. at a time.

The finest sanding belt of which I know is a 600 grit, cork, polishing belt. It comes in only one size--2" x 21". It may be that Micromesh makes belts but I'm not aware of that.
 
My mom is a glass artist and uses a wet belt sander for her work.
We of the wood-warrior tribe obviously don't like that whole wet factor, but I know that she has silicon carbide belts of different sizes going anywhere from that 60 to 800 grit and beyond. (I just checked.) If you really want a polish, and are too cheap to get a buffing wheel set up, she also has buffing belts, which go right on the belt sander.

Check out glassworking tools retailers, I bet they would have plenty of options.
 
Couple reasons why you don't see fine and finer sanding belts.

1) There comes a time where the particle size is just too small to get much glue under it. With the mechanical stress, the grit would "fri" like a soft grinding wheel.

2) Belt sanding generates a lot of heat with little pressure. Heat dries, hardens and burnishes the surface of the wood. That's why we wet sand.

Answer to saving time whether turning or flat is the same - sharp edges and proper angles to produce the best surfaces. Those of us lucky enough to own Lee Valley smoothing planes don't sand much in flat work, those proficient with the chisel don't sand much on turnings.

One observation, though. Sanding across the ridges made by a gouge or scratches made by a coarser grit is a bunch faster at removing them. Most use rotary sanders to do this.
 
Sounds like you might need to work on you tool technique. There are many techniques for getting smoother cuts, shear cuts, shear scraping, etc. Also if you have rough surfaces are you starting with coarse enough sandpaper ? One common problem I see is that people see on the internet or read in a book/magazine that this or that turner starts with 1,000,000 grit sandpaper because their finish off of the tool is so good. Don't be afraid to start with coarse grits. If the surface is rough start with 60 or 80 grit and work up, don't skip grits, use a good quality paper (Klingspor or similar), and don't move on until you have sanded out everything possible with the grit. Also don't be afraid to go back a grit or two to do cleanup as it is much faster to go back and do the cleanup that way.

Scott
 
Here is a secret.

I send more time on finishing then I do on turning.
Flat or round, I even finish the finish.
 
Belt sanders are made for removing material and not for finish sanding. I have never had a need for a sanding belt finer than 120 grit and even then, it is necessary to exercise care to avoid glazing the wood and loading the belt. Once a surface has been flattened on the belt, I go to some other method of finishing the sanding. A ROS is fast and works well. For anyuthing finer, hand sanding is my preferred method because it is just as fast as powered sanding, but without the risk of glazing.

Bill
 
Thanks for the input guys and the warm welcome.

The boxes are flat, but I turn them a bit to round the corners. I could probably just send a roundover on them, but it's much funner to use the lathe. The combo of lathe/planar leaves a nice finish in and of itself... but these types of woods polish out very far, and it's been well worth the effort to do so... I'd be hard pressed to find someone who could generate a finish like that right off the tool.

Yes, I did see the silcon carbide paper for glass sanding, but I don't know of anyone who's used it on wood. Anybody here tried that? I also checked to see if micromesh has any belts and it turns out they do, but they're very small 1/4" x 13"... so unless I build up a custom drive to run a bunch of them in parallel, they're probably not an option.

The overall concern I hear is the heat caused and the potential for damaging the finish by glazing, etc. I agree with this concern completely, at the same time though it seems to me that the only difference between a machine sanding something and your hand is that your hand gets tired and it takes a lot longer. The same basic principles still apply, but this assumes you can control the machine. So, I'm thinking if I can build a small modulator to adjust the speed of the motor I could potentially have a sander that is much slower than the standard belt drive but faster than hand sanding. Most standard belt sanders run at 1300-1600 sfpm... so if I could bring that down to 100 or less I could still have a lot of control with much less risk of causing damage. I don't know what do you guys think? If I could get it to work, seems like the biggest challenge would be finding the paper. (silicon carbide?)

Anyway, thanks for listening.
Lorn
 
Belt Sander for fine finishing?

I would drop the idea of a belt sander and get a good random orbit sander which can take pads to 4000 grit. When working with exotics I seldom start below 180 grit and usually start at 220 grit. Belt sanders are not meant for fine finishing. After you go through all your effort to make it work you will undoubtedly be unhappy with the results.
Matt
 
I must admit I'm not too wild about the belt sander idea, but I believe the guy has the right to experiment if he wants to. I mean, I've never tried it before, it may work for him.

Note on the silicon carbide paper:
I use it on A-weight automotive paper extensively for my fine sanding. It's cheap and it does the job. A light touch is needed however, or you get these wonderful black scuffs on your wood that require 320 or coarser to get out.
 
Ok, I hear you guys on the belt sander. The main reasoning behind it was that it would allow me to run the belt in the direction of the grain, mimicking how I do it by hand. I think, though, that it's generally just going to be too much of a PIA. I'm very pro KISS.

So, onto the other possibilities. Re: the random orbital sanders; I've heard they can leave swirl marks, which was the main reason why I hadn't looked into them yet. You guys using these, are you taking them out to the finer grits? Matt, sounds like you are and have some experience with exotics... would really appreciate it if you could perhaps give a rec on a brand/model or any useful tips or observations. Also, what makes you guys reccomend these over finishing/palm sanders?

Thanks a bunch.... really helpful input so far.

Lorn
 
Lorn,

I have never had a problem with swirl marks from a ROS. Used improperly, they could leave swirls -- three possible causes:
  1. skipping a grit
  2. insufficient sanding to remove marks from previous grit
  3. applying too much pressure against the wood with the sander -- random orbital sanders should be used such that the weight of the sander is the only pressure being applied.
Bill
 
lorn said:
Re: the random orbital sanders; I've heard they can leave swirl marks, which was the main reason why I hadn't looked into them yet. You guys using these, are you taking them out to the finer grits?
Click to expand...

Normal reason for making swirls with a ROS is that you have taken away one dimension of movement by friction - slowing down too much - or having it in contact with the work on startup or shutdown - a dig-in. You may discover swirls left by previous grits as well, which will never come out with the current grit, because the background's already burnished or you wouldn't see it. Given the wavelengths of visible light and particle size of the dust, you should not see a shinysurface when you lift the paper at less than 600-1000. If you do, you're already heating and burnishing, not sanding.

You mentioned that these corners are within roundover contour limits. Makes an ROS a poor choice, as the dual motion makes them difficult to hold on narrow surfaces without digging. What you need is an oscillating belt sander or a stroke sander, where you can use grits as fine as 220 or so without burnishing and a table to reference.
 
I'm a little confused- you make a flatworked box and then turn it on the lathe to round the corners? Maybe I am not visualizing this but it sounds like the hard way, or maybe an easy way but I don't think I understand what you are ending up with. Can you post a picture? 😕
 
Wood,
Does indeed seem like the hard way. Maybe a router with carbide roundover bit would be easier.
Lorn,
I still like your idea of a variable speed belt sander. My 6x48 with 10" disc is way too fast a lot of the time, and no space for stepped pulleys. An EVS would be dandy, but cost prohibitive, for me at least. But technically feasible.
 
Another fan of the random orbital sander here. I'd be worried that the belt would cause streaking or scratches precicely due to its unidirectional nature. Using the ros on flats and hand sanding the curves might be the way to speed it up.

Dietrich
 
Speed Control

Lorn,
I too doubt that a belt sander is the answer, BUT if you want to slow one down and test it, well, if the electric motor has brushes (and is within the amp limits of the controler) you can plug it into a variable speed controler like is used on a single speed router to slow it down when using large bits. A motor with brushes is a "universal" motor. Here is a site the sells the speed controller, good luck. >> http://www.woodzone.com/Merchant2/merchant.mvc?Screen=PROD&Product_Code=828122
 
Richard and Woodwish,

I agree about putting the box on the lathe to "round the corners". A roundover router bit would be a far better choice in my judgement. The result of doing such a thing on a lathe would not achieve a roundover in any event, but rather a chamfer as shown in the picture below. And if the box were not square (a much more likely scenario), the chamfers would be skewed. It also seems to be a great opportunity to destroy boxes at the abrupt transition from side to end grain. Is that a tugging feeling that I sense in my leg?

Bill
 

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Lorn,

How about a disc sander? Make your lathe into one and slow it down as far as you can. Lee Valley sells a mandrel you can use to mount a chunk of MDF. Standard 9x11 sheet sandpaper gives you a 9" disc and a wide range of grits. Not quite as in line with the grain as a belt sander but maybe worth a try. It ought at least to be a cheaper experiment.

Graeme
 
Thanks for the replies guys. Really appreciate the input.

re: the corner rounds (didn't think the rounding aspect would get so much interest 🙂).... these boxes are very small. I'm using 2x20" bar stock, and it really is pretty easy to mount it up and turn it due to the size... then I just part off for the specific width. No, they're not perfectly round (bit of a chamfer), but it's been a much simpler solution for me then to buy some small roundovers and then build up a custom jig... would probably have to mount my router on a table to do it right, so I've just been going with the lathe. Also, when hand sanding the corners, the chamfer sands out. The faces are planed square (mic measured), so I don't have any problems with skew and I always make sure my tools are sharp, so I don't see a lot of chipout.

Anyway, I've definitely decided to go ROS. If it doesn't work out then I'll explore building up the custom belt sander idea. One of the other problems I realized I would face with the belt, is that most motors are rated for a certain RPM where they're delivering full torque... it's possible I would run into problems with the motor having very little torque (if at all) at the speed I intended to run it. I'm sure I could find a custom motor, but then this all just starts getting really complicated.

Anyway, once I get it all up and running, I'll let ya'll know how it went.

Thanks again,
Lorn
 
Hi Lorn,

If you use an AC induction motor to drive a belt sander, there will be essentially no difference between no load and full load speed -- just a few RPM. The 60 Hz. power line frequency is the main factor in governing the speed on induction motors. Also, the main load on a belt sander is driving the belt mechanism and normally is not the object being sanded.

Bill
 
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