Miter Table Slot Wear

[jmw]

I have a BT3000 that is about 12 years old. Although I have never been impressed with the smoothness with which the bolt for the miter fence adjusting clamp slides inside the slot of the miter table, it has always worked.

However, a few days ago, I was unable to tighten the adjusting clamp in the zero dgree position. When I checked out the underside of the slot in the miter table, I noticed that the steel bolt has worn a pocket in the edges of the slot, something that I've had a suspicion might happen one day. It doesn't surprise me, considering the relative difference in hardnesses between the steel bolt and the aluminum table.

I certainly cannot be the first one to encounter this issue and I'm wondering if anyone has come up with a solution other than replacing the miter table itself. Thanks for any input.

JMW

[NJFrank]

Just was discuused here

http://www.bt3central.com/showthread.php?t=26031

[LCHIEN]

I assume that the bolt head is rotating so you cannot tighten it?

I thought about somthing like Bondo-ing the slot. but that would be soft and eventually fail.

Another option is to convert the whole shebang from a 5/16 bolt to a 3/8" bolt with a slightly wider hex head, new knob and drill out the plastic piece...

I have to wonder, this is not a frequent issue although I have heard of it once before. Are you overtightening the fence locking knob? I find what some people think are tight sometimes means crushing force and for others its just snug.

I think personally what I would do, is look around fora parted out BT3000 and buy the SMT table for $30 bucks or something... that would probably be the most straightforward. The risk is that the table slot will be worn, too, but since this seems to be a rare event, and yours lasted 12 years, a part from a relatively unused saw may last you another 5-6-7 years...

HTH, let me know how it comes out.

BTW, the slots NJFrank references are miter slots (in the add-on dual miter slot table) in the top of the table.
The slot JMW is inquiring about is the slot for the bolt head in the bottom of the SMT; the bolt being for the miter fence angle locking mechanism.

[Slik Geek]

JMW - you aren't the first. I was surprised to read that this is apparently a "rare event". It happened to me during my first five to seven years of ownership of the BT3000, just as described. There is too much of a gap between the bolt head and the slot. This allows the hex head bolt to turn, so all of the force of the bolt head against aluminum is concentrated at two corners of the bolt's hex pattern. The steel quickly wins the battle, resulting in significant slot widening wherever the bolt is most frequently tightened. This scheme was one of the few areas of design on the BT3000 that I thought was lacking.

I don't think that I'm overtightening the miter knob - I'm not known for my crushing physical strength! I do have to snug the knob well to keep the miter from sliding out of position, and even then it still moves at times. (Have to search the archives for guidance on that one).

My solution isn't fancy, but it has worked for about five years with no maintenance required. I believe that I was able to cobble it up out of parts found at my local hardware store too.

You'll need a hacksaw, grinder (or a file and lots of time), 5/16"-18 die (or just buy a couple of 5/16"-18 nuts), a 1/2" and an adjustable wrench. Buy a 5/16"-18 x 4" bolt and a 5/16"-18 square nut.

Thread the square nut onto the bolt and tighten it very securely against the head. Grind or file about 0.015" off each of the flats of the square nut. Don't worry about what you do to the hex head - you'll probably be removing some material from it later as well. The objective is to get the assembly to fit inside of the miter table slot with just enough play to allow smooth movement, while keeping the play as small as possible. Use a "virgin" area of the slot to test your bolt trimming progress.

Next, grind a smooth radius on each of the four square bolt corners. Also take off the corners of the hex head so it doesn't extend beyond the square nut. You need to make all surfaces smooth, or your aluminum slot will get chewed up mighty fast. Don't rush this step, or you'll be replacing the miter table soon.

Temporarily assemble the miter table, using your new bolt combo. Note how much of the bolt needs to be trimmed off. Remove the bolt from the miter. Thread the die onto the bolt backwards (so that it will cut a new thread on the way off). Alternatively, thread on a couple nuts. Either way, thread past the point where the bolt will be cut.

Hacksaw the bolt to length. Better to be a tiny bit too short than too long. Grind or file the bolt end flat, and taper the sharp thread as it reaches the end of the bolt. Unscrew the die or nuts to clean up the threads. Reassemble the miter table and make sawdust once again!

Hope this helps. It has worked well for me.

[LCHIEN]

JMW - you aren't the first. I was surprised to read that this is apparently a "rare event"...

Well, I maybe misspoke, but I've been on the forum here and at Ryobi before that for several years and don't recall its being that frequent.

Of course a doctor friend once told me in Medical school they said
some procedure only had a complication rate of .5%, but, if it happens to you , it's 100%.

Anyway, sounds like your fix would work well. Make sure if you try this to get a bolt threaded all the way to the head, many hex head bolts I've seen they only thread the last 1-1/2 inches of the bolt.

[Black wallnut]

I'll agree with Loring on this one! Not to appear sheep like but I find myself agreeing with Loring quite often! It seems his memorey is about the same as mine when it comes to problems and issues that have proven over time to be common with the BT3 saws. Both of us were common contributer to Ryobi's forum long before Sam started this one.

My solution would be to take a bar of steel 5/16" x 1/2" x 1" and drill a hole dead center in the side 1/2". Tap this hole to 5/16" and locktight in a stud the lenght of the current hold down bolt. Thus making a rather large "T" bolt. That should allow the use of most of the adjustment slot except for perhaps +/- 45° to +/- 40°. Unless the complete slot is warn away at 0°.

Replacing the table is another great option if you can find one for a reasonable price in the classifides on this site.

[jmw]

I really appreciate all the ideas that have been provided. I'll probably end up trying one of them- or more, if need be.

My first, hurried attempt to solve the problem was to find a washer for the bolt and grind parallell flat edges on it so it would just fit within the miter slot. Of course, in hindsight it would be easy to say I knew the bolt would spin with a washer between its head and the slot. However, for a moment I thought I might have a clever and very simple solution.

One idea I have is to buy a machine t-nut (part #A80010) from t-nuts.com and attach it to a threaded rod with the same diameter as the bolt. If the t-nut is too long to fit into the "keyhole" in the SMT, maybe I could grind the keyhole a bit bigger to accomodate it. What I like about the machine nut is that, being rectangular rather than hex-shaped, it will provide for more surface contact in the slot and will hopefully bridge the pocketed area at the zero position. How does this sound?

[backpacker85]

Not exactly the same problem, but.....

While I've only had my BT3100 assembled and "tuned" for a couple weeks now, I was originally disappointed with the movement of the fence on the SMT. It seemed to bind in the slot and was very difficult to adjust, no matter how loose I turned the knob.

Looking at it closer, I realized that as I was loosening the knob, it was rising on the bolt, but the bolt was not dropping down in the slot. I got into the habit of loosening it a few turns and tapping it down to ensure the bolt head dropped away from the underside of the SMT. Slid slick as a whistle after that.

After reading this thread, I think I'll look into a square head bolt that fits the track better, or maybe a square nylon nut or nylon T-nut that fits the track better. I'd rather sacrifice the nylon than the SMT (just my rookie thoughts).

[LCHIEN]

I really appreciate all the ideas that have been provided. I'll probably end up trying one of them- or more, if need be.

My first, hurried attempt to solve the problem was to find a washer for the bolt and grind parallell flat edges on it so it would just fit within the miter slot. Of course, in hindsight it would be easy to say I knew the bolt would spin with a washer between its head and the slot. However, for a moment I thought I might have a clever and very simple solution.

One idea I have is to buy a machine t-nut (part #A80010) from t-nuts.com and attach it to a threaded rod with the same diameter as the bolt. If the t-nut is too long to fit into the "keyhole" in the SMT, maybe I could grind the keyhole a bit bigger to accomodate it. What I like about the machine nut is that, being rectangular rather than hex-shaped, it will provide for more surface contact in the slot and will hopefully bridge the pocketed area at the zero position. How does this sound?

Actually now that I've had 24 hours to think about it, I'd do something along the lines of what already has been suggested (shamelessly stolen), perhaps with the following new features:

Get a 5/16-18 threaded rod (or all-thread as they call it), cut to a length a little longer than the existing bolt.

The existing bolt hex head is I think 1/2" across (I didn't measure it but i tihnk a normal 5/16 nut takes a 1/2" wrench or socket, IIRC). The flats are short so lengthening them is important - the square nut is good, the 1" bar suggested is better but may cut into the overall angle min and max,
so I think an in-between length like 3/4" long would work.

so, Get a piece of aluminum stock 1/2" wide, 3/4" long and 1/4 to 3/8" thick. Aluminum because its softness matches the table and we will want to wear the new "nut" faster than the table.

So drill and tap for 5/16-18 into the center of the 1/2 x 3/4 side.
Now use a file and round over the 3/4" long edges on the top.
Also round off the vertical edges of the ends so from the top it looks like an oval.

Loc-tite the end of the threaded rod into the new nut with the rounded
side on the side with the rod projecting.

Now use this in place of the old bolt. The rounded top will fit into the slot better and spread the loading on a larger area, at least lack of sharp edges will protect the aluminum table slot. The ovaled ends will allow it to slide better when changeing miter angles. Being aluminum it will not gall so badly and reduce wear on the table and wear on the nut more, the nut being more easily replaced than the table.

Make a couple of extra nuts while at it in case they ever wear out. Having spares is a great way to prevent recurrance (thank you, Mr. Murphy).

Probably there are some more improvements - (I'd check the rounding over of the bar to make sure it fit the slot as I rounded it over) but right now its cold and I just got the part to fix my compressor so I'll be working on that instead of looking at the miter table.

[Slik Geek]

While I've only had my BT3100 assembled and "tuned" for a couple weeks now, I was originally disappointed with the movement of the fence on the SMT. It seemed to bind in the slot and was very difficult to adjust, no matter how loose I turned the knob.

Looking at it closer, I realized that as I was loosening the knob, it was rising on the bolt, but the bolt was not dropping down in the slot. I got into the habit of loosening it a few turns and tapping it down to ensure the bolt head dropped away from the underside of the SMT.

Ken,
Your post brought back old memories. I had the same problem before I changed to the square nut described above. The phenomenon you describe was a symptom on my miter table of the nut digging into the aluminum. It started wearing a path in the upper part of the channel. (The nut, IIRC, is thinner than the slot channel and only contacts the upper 2/3?) Eventually, the binding got worse as the channel deepened. The sooner you modify your setup, the less damage your SMT will experience.