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Old 6th October 2002, 08:00 AM   #1
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Default Straight sanding


Im at the sanding stage of making my cabinets. All is cut. Im experiencing some difficulty along the 18mm edges of the MDF.

I find that Im not sanding it flat, but rather depending on direction, the uneven pressure from my hand is causing a 'hump' in the middle.

I realise this is basic woodworking skills, but I severlely lack. I have the sandpaper wrapped around a block of wood that I use to rub up and down the edge Im sanding.

Tips?

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Old 6th October 2002, 01:02 PM   #2
remp is offline remp  New Zealand
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If you are sanding an edge there are two problems you can experience.

One is as you have found, uneven pressure can easily result in humps and hollows on you edge.
The other common problem is the sanding block is not held exactly square to the wood and along the sanded edge you have some parts that lean one way, some lean the other way and some are square.

When you look down the edge any out of squareness becomes easily noticable.

The way to cure this in a simple manner is to locate a long sturdy piece of wood that is straight and about a foor longer than your edge. Gauged 4 x 2 is good for this but check it is straight first. Then buy your sandpaper in a roll as long as the board, glue the sandpaper onto the board so you now have a long sanding block. As long as your long sanding block is stiff and not bending you can easily get straight edges.

The other problem of sanding the edge square can be done by screwing a long flat board or several smaller guide blocks onto your sanding block so it is at right angles to your "long sanding block" and you can glide the squaring board along the face of the MDF.. I do this often and glue a sheet of felt on the "squaring baord so it does not mark the wood.

Now you can sand the edge straight and square quite easily.

Often cut boards are not exactly the right dimension. They can be wider at one end than the other. This is easily corrected by the long sanding block by a little more pressue at one end of the sanding stroke than at the beginning. For example.

It is also most helpful if you can arrange to clamp your MDF steady while sanding so you can guide the sanding block with both hands rather than trying to sand with one hand and hold the wood with the other.
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Old 6th October 2002, 03:22 PM   #3
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If you have access to a router I would suggest using a trimming bit to even out your edges. This is a bit that has a bottom mounted bearing exactly the same diameter as the cutter.

If you set the depth of cut so that the bit runs along the board you are joining to, and you run the base of the router of the surface of the board with the offending edge the you will get smooth accurate 90 degree cuts, that ,if you use a sharp bit, will need only finish sanding.

If you don't have a router, buy one! I think it is the most valuble tool a speaker builder can own, as with a bit of practise, just about any process needed in cabinet manufacture can be carried out with one.

Other than that, Remp's idea is a good one, or you could borrow or buy a small hand plane.

But with all new techniques, practise on some scrap first
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Old 6th October 2002, 03:34 PM   #4
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Check Brian's comments about routing bits here: Pictures of my Thor project

If you work with wood more often than occasionally a router is a must.
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Old 7th October 2002, 03:14 PM   #5
Schaef is offline Schaef  United States
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You guys are going overboard here... All he really needs is what's called a shooting board... Its more commonly used with hand planes, but will work quite well with sanding as well. I thought that's what remp was going for, until I realized he was just making a HUGE sanding block! A shooting board is just a board clamped to the edge of the board to be sanded or planed and is used to give some extra support on the one side so that you'll be shooting straight down the edge. In other words, take remp's idea of a long straight board, clamp it to the edge you're sanding at the height you're sanding to. Then take your sanding block and sand until you're holding it flat on both surfaces.

Now, granted the routing trick is quicker and easier, but this way is cheaper, less noisy, and it helps you get some exercise in the process!!
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Old 7th October 2002, 05:45 PM   #6
Bob2 is offline Bob2  Canada
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The edges you are talking about, if they are the edges you are going to glue together, then you shouldn't be sanding these. I made the same mistake on some cabinets I was making, a cabinet maker friend of mine told me to just glue the joint together, be they cut on a table saw, jointed, whatever. This will give you a better joint and avoid the problems just mentioned.

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Old 8th October 2002, 11:30 PM   #7
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Well - my cuts are not perfect. Jig-saw doesnt give perfect enough that I can just make the cabinet straight. There is a little excess which needs to be taken off.

I have run into the issue of the 'hump' as I mentioned with sanding by hand. A friend reckons I should use a plane (which he apparently has, so I might pop around to his place to do it).

Other than that, if I understand right, Im making an L-shape from wood with sand paper on the bottom of the L, and than the upright of the L will serve as a guide to help against uneven sanding?

Im not too clear on Schaef's description of a shooting board - can someone clarify?

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Old 8th October 2002, 11:38 PM   #8
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Just going to bed, will post some pics in the morning, if Schaef doesn't beat me to it
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Old 9th October 2002, 03:33 PM   #9
Schaef is offline Schaef  United States
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Don't have pictures, but I did a search on google for woodworking and shooting board. Here's some web pages that might be usefull:

http://www.millard.demon.co.uk/plani...otingindex.htm
http://nitwit.com/nws/article_1/article1.html

These should give you some ideas on how to accomplish what you want. If not, I can try some other things as well...
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Old 9th October 2002, 07:29 PM   #10
Bob2 is offline Bob2  Canada
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Try taking 2 of your 18mm edges that need sanding and clamp them flush together, this will give you a 36mm edge to sand, wider surface, less chance of rounding edges.

Bob2
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