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Forum topic by Chas7715 posted 02-08-2016 04:59 PM 532 views 0 times favorited 6 replies Add to Favorites Watch
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Chas7715

23 posts in 353 days


02-08-2016 04:59 PM

Hi Everyone!

I’ve been busy making some wall cabinets for the garage and I ran into a problem over the weekend that has me confused.

I’m using a french cleat to mount the cabinets on the wall. I had a problem when I tried to rip a 45 degree cut on an 8ft 1×4. My table saw is an older Craftsman with left tilt. I ran the board through with the fence on the right of the blade so that meant that the off cut was to the left of and under the blade. The board kept trying to rise up the blade angle resulting in a real sloppy cut. I tried using a feather board clamped to the fence but the board would still rise up, now tilting with the cut edge rising.

What in the heck am I doing wrong and what is the best way to accomplish this??

TIA,

Chuck

-- Perfection is highly overrated!


6 replies so far

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jeth

249 posts in 2304 days


#1 posted 02-08-2016 05:04 PM

Sounds like the fence is probably not parallel to the blade… slightly closer at the back?

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clin

514 posts in 462 days


#2 posted 02-08-2016 05:42 PM

I was running into a similar issue cutting french cleats. Here’s a link to the thread I started about it.

http://lumberjocks.com/topics/138754

In my case, I used feather boards, but what worked best was to put a block between the feather board and fence to hold the feather board away from the fence and closer to the blade. Be VERY careful to not extend the feather board over the angled blade.

In the thread (linked above), I have a photo of my initial setup, though not one with the block behind it. But someone did put in a drawing of the idea.

The only issue with all this is there is a lot of stuff in the way of using a push stick. As you are doing, I was ripping 8 ft long boards. So for much of it, I could guide the board holding it well out in front of the saw. But once the end got on the table, I had to use a push block. As I recall, I could just fit it past my clamps.

There were a lot of other ideas in that thread. One I liked, but wasn’t well setup to try, was doing it with a circular saw and guide or a track saw. This I believe would be the easiest and safest once setup for it. As it was, I was about half way through cutting 5 sheets of ply into cleats when I started that thread.

On a side note, I’ve just purchased some fence clamps:

I’m thinking about making feather boards I can hold down with these. Not sure how tight they can grip the feather board against the fence to apply down pressure. But the advantage for something like ripping is the clamp doesn’t extend out past the feather board. So the clamps wouldn’t be in the way of a push stick.

-- Clin

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JBrow

819 posts in 386 days


#3 posted 02-08-2016 08:12 PM

Chas7715,

I think what is happening is the out-feed side of the blade is contacting the stock which then imparts a lifting force to the stock. The problem have be one or a combination of causes. The blade, mitre slot, and fence may be out of alignment, as suggested by jeth. The stock may be moving away from the fence or rising off the table causing one edge of the kerf to contact the blade or the stock may be pinching the blade. Also, if the stock is has even a slight bow along its length, the stock can make contact on the out-feed side of the blade.

After checking the blade to the mitre slot and fence to mitre slot alignment, a hold-down, hold-against, and a splitter may help.

In an effort to work as safely as I can, I keep the Original Equipment blade guard and splitter on the table saw whenever I make through cuts. A splitter will prevent the stock from pinching the blade as the stock passes beyond the blade. Also, as you lose the ability to hold the stock firmly against the fence, such as toward the end of the cut, the stock can rotate slightly toward the blade and the back of the blade will cause the stock to rise up on the blade. A splitter will go a long way in preventing these problems.

The hold-against is a feather board (or even a simple board – no fingers) that sets in front of the blade and holds the stock against the fence. It must be in front (in-feed side) of the blade (never on the out-feed side of the blade which could cause the stock to pinch the blade). It must not be set tight, but just in contact with the stock. If the hold-against is too tight, it can cause a slight rotation of the stock into the blade as the stock clears the hold-against.

The hold-down I often use is a simply straight board secured to the fence from near the in-feed edge of the blade to the end of the fence. Once the fence is positioned to make the cut and the blade lowered, place pieces of scrap the same thickness as the stock on the table and against the fence at the in-feed, blade center, and behind the blade to set the hold-down height. Drop the hold-down board on top of the scrap and secure the hold-down to the fence. The hold-down should not apply downward pressure on the scrap, but rather just contact the scrap so that the stock slides freely under the hold-down but cannot rise up.

With the hold-down secured to the fence, raise the blade to a height that will clear the stock by about ½” – so that a through cut is assured. Minimal blade height will minimize out feed side contact of the stock with the blade.

Before making the cut prepare a push stick. It can be a piece of scrap the same thickness as or thinner than and narrower than the stock. It must be sized to push the stock safely beyond the hold-against and under the hold-down and past the blade.

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Chas7715

23 posts in 353 days


#4 posted 02-08-2016 09:12 PM

After posting the question and doing other things ( I am at work after all!) I think I answered my own question. I thought through the steps and realized that maybe my blade wasn’t high enough? Since the real cutting action takes place during the downward (toward the table) portion of the rotation, it the blade wasn’t high enough to put downward force on the work piece, the rear of the blade was going to push it up. Does anyone think this a possibility? Earlier, I ripped a 6” piece of 3/4” ply into two 3” pieces at 45 degrees and had no problem. The difference as I remember it was that blade was higher.

I’ll check to see if the fence is still parallel to the blade. Thanks for the suggestion!

-- Perfection is highly overrated!

View clin's profile

clin

514 posts in 462 days


#5 posted 02-08-2016 10:34 PM

I think the amount of down force on the front, cutting side (or up force on the back) is the same no matter how high the blade is, as long is it is going completely through the stock. What changes with blade height is the forward force. The higher the blade, the less of the blade there is pushing the stock forward. I.E., the higher the blade the easier it is to push the stock through the blade.

All this is true if the blade forces can be viewed simply as friction forces. Given that cutting teeth are involved, it’s more complex than that. But in general, I still think it works out pretty much the same.

I’m not going to say it wasn’t easier when you had the blade higher, but it sounds like you were cutting different wood. I know when I ripped hundreds of feet of plywood, some pieces were easier than others. If the wood had little or no bow in it, it was always easiest. Some pieces, even being plywood, had significant bow and it took much more effort to keep them flat through the cut.

I little bow doesn’t effect common 90 degree cuts very much, if at all. While with an angle or bevel cut, it critical to keep the stock flat on the table, else the cut won’t be were it is intended.

-- Clin

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JBrow

819 posts in 386 days


#6 posted 02-08-2016 11:08 PM

Chas7715,

I do not understand how the height of the blade would cause the stock to lift up from the table.

Rather, I suspect that the blade is lifting the stock up off the table because the direction of the back of the blade at the throat plate is upward and the stock is making contact with the back of the blade. Additionally, back of the blade contact with stock is the cause of kickbacks. If the back of the blade makes no contact with stock, there should be no lifting of the stock.

On a related note and contrary to conventional wisdom, I make all through cuts with the blade at full height. According to Forrest manufacturing, maximum blade height keeps the blade cooler and increases longevity. To ensure safety, I always make through cuts with the Original Blade Guard in place – otherwise, with no blade guard, keep the blade as low as possible.

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