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I recently queried the group and searched the archives on shim replacement (thanks again for helpful responses). One of my shims had sheared and I needed a quick fix so I could get back to a project that had to be done right away. Based on my needs, I decided to use the following two separate methods, both of which were mentioned in the archives, but only once each--so they may not have produced much notice--and one (the brass shims) was never tried as far as I know, someone just suggested it. I read of no negative responses. The two methods:
*Brass shims. These *should* be an ideal material for the shims, better than SS anyway.
*3M Marine 5200.
Here was the procedure:
1. Use standard method of disassembly to access the guide holder and shims (http://www.bt3central.com/forum/topi...TOPIC_ID=16878)
2. Clean up everything in the area. Vacuum, compressed air, then a swab of acetone. Then I took my Dremel and buffed the aluminum guides lightly. Another swab of acetone.
3. Fabricate brass shim. Using a digital caliper (didn't have a micrometer on hand), I measured the SS shim at .008 thickness. I had on hand some brass shim stock that was .005, which should do. If it doesn't then I'll try something thicker--the play between the aluminum guides is enough to support much thicker stock, which would probably be a better fix, but I was in a hurry, so....
The brass stock, BTW, I got from a Hobby Lobby store, is made by K&S engineering, stock #5250, sold for $1.99, and is 4" x 10". It cuts easily with a razor knife. I used one factory edge on a 4" side for the length of the shim and made it just a tad wider than the SS one--there's plenty of overhang room on the aluminum guides for a wider shim on the lateral edges (the ones pointing towards the front and back of the saw); likewise, the 4" length is a bit longer but makes for fine tabs. Bent it over a straightedge (make sure to try and get the interior edge--the one *parallel* to the front and back of the saw--the correct width) and cut about 1/4" along the crease on both ends to form the tabs. The bends were not very crisp, but with this thin of brass stock, just tightening up the guide holder forms it nicely.
4. Lube the aluminum guides. Since I had the thing halfway apart anyway, I took the opportunity to lube the adjustment screws for miter and height. I use a formula that is fairly "dry" and slippery (wire-pull lube + powdered graphite). Used a small dab of the same stuff smeared on all aluminum surfaces that contact shims.
5. Adhere shims to guide holder. Got out the trusty 3M marine 5200, spread on a thin layer with a razor edge to the guide holder aluminum surfaces (being careful not to get it around the shim set screw openings).
6. Pop the shims on, reassemble. Use loctite on guide holder and arbor mount screws.
7. Readjust the shim set screws, again using loctite. This is easy and necessary (I noted upon disassembly that one of mine had been over-tightened, which may have led to the failure).
8. Give the 5200 a day or so to dry. Use the fast-cure if you can.
As I mentioned, I had to get a project done right away, so I used it without letting the 5200 cure fully. Everything was smooth and glided easier than I ever remember it to have been. The shims showed no signs of movement. So, I'm hopeful.
If this works out, it seems the best fix for the shim problem so far, but I wanted to canvass this groups opinions. Norman Haven's shim supports seem to be the favored cure, but if the 5200 works as it has for others (http://bt3000.com/Shims/), then it's far easier, quicker and cheaper than machining. I don't understand anyway, from a material perspective, why the shims have to move at all relative to the aluminum bed of the guide holder. The brass shims are also worth considering: for $2 and maybe 2 minutes of "work" making them, they're an improvement over the SS units economically, materially, and temporally (i.e., you can get them quicker).
So, what do you think? I'm interested to hear the voices of experience.
H.
*Brass shims. These *should* be an ideal material for the shims, better than SS anyway.
*3M Marine 5200.
Here was the procedure:
1. Use standard method of disassembly to access the guide holder and shims (http://www.bt3central.com/forum/topi...TOPIC_ID=16878)
2. Clean up everything in the area. Vacuum, compressed air, then a swab of acetone. Then I took my Dremel and buffed the aluminum guides lightly. Another swab of acetone.
3. Fabricate brass shim. Using a digital caliper (didn't have a micrometer on hand), I measured the SS shim at .008 thickness. I had on hand some brass shim stock that was .005, which should do. If it doesn't then I'll try something thicker--the play between the aluminum guides is enough to support much thicker stock, which would probably be a better fix, but I was in a hurry, so....
The brass stock, BTW, I got from a Hobby Lobby store, is made by K&S engineering, stock #5250, sold for $1.99, and is 4" x 10". It cuts easily with a razor knife. I used one factory edge on a 4" side for the length of the shim and made it just a tad wider than the SS one--there's plenty of overhang room on the aluminum guides for a wider shim on the lateral edges (the ones pointing towards the front and back of the saw); likewise, the 4" length is a bit longer but makes for fine tabs. Bent it over a straightedge (make sure to try and get the interior edge--the one *parallel* to the front and back of the saw--the correct width) and cut about 1/4" along the crease on both ends to form the tabs. The bends were not very crisp, but with this thin of brass stock, just tightening up the guide holder forms it nicely.
4. Lube the aluminum guides. Since I had the thing halfway apart anyway, I took the opportunity to lube the adjustment screws for miter and height. I use a formula that is fairly "dry" and slippery (wire-pull lube + powdered graphite). Used a small dab of the same stuff smeared on all aluminum surfaces that contact shims.
5. Adhere shims to guide holder. Got out the trusty 3M marine 5200, spread on a thin layer with a razor edge to the guide holder aluminum surfaces (being careful not to get it around the shim set screw openings).
6. Pop the shims on, reassemble. Use loctite on guide holder and arbor mount screws.
7. Readjust the shim set screws, again using loctite. This is easy and necessary (I noted upon disassembly that one of mine had been over-tightened, which may have led to the failure).
8. Give the 5200 a day or so to dry. Use the fast-cure if you can.
As I mentioned, I had to get a project done right away, so I used it without letting the 5200 cure fully. Everything was smooth and glided easier than I ever remember it to have been. The shims showed no signs of movement. So, I'm hopeful.
If this works out, it seems the best fix for the shim problem so far, but I wanted to canvass this groups opinions. Norman Haven's shim supports seem to be the favored cure, but if the 5200 works as it has for others (http://bt3000.com/Shims/), then it's far easier, quicker and cheaper than machining. I don't understand anyway, from a material perspective, why the shims have to move at all relative to the aluminum bed of the guide holder. The brass shims are also worth considering: for $2 and maybe 2 minutes of "work" making them, they're an improvement over the SS units economically, materially, and temporally (i.e., you can get them quicker).
So, what do you think? I'm interested to hear the voices of experience.
H.
Loring in Katy, TX USA
Black wallnut
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