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post #1 of 8 (permalink) Old 02-26-2011, 05:44 AM Thread Starter
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Default A dangerous idea?

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I've just completed my first router table, and gave it a run today. All went well although I'm slightly fearful that I was making a mistake in feeding a long (circa 300mm) batten (circa 25 x 25mm) across the bit, with one end butted against the fence and the other free. I made many passes as had to make a total of 10 slots, each about 20mm wide by 12mm deep) and although most went without a hitch, there was the odd pass when something went wrong and the stock jumped a little and got a little ripped up. I did have a feather board on the fence (vertical) and a piece of MDF behind the batten. I'm soon to build a cross-cut sled with toggle clamps - I would have used that had it been ready. I've done a quick diagram (attached) of my setup - and indicated where I was getting a little tear out - but not on every pass. The bit was almost brand new, a Trend 3/4" dado cutter. The wood was quite hard (rimu) , I was taking about 6mm (height of cut) at a time, and tried 15,000rpm and 12,000rpm. Bit speed didn't seem to make much difference - I also varied the feed speed. I did notice the wood was burning a little - that would indicate too high RPM, or too slow feed - or both - correct?

Anyway, my next idea is to build a finger joint jig as demonstrated here (Finger Joints (Box / Comb joints) - by Steve Maskery @ LumberJocks.com ~ woodworking community) - check it out, it's a very fine & safe jig. The author uses a mitre track, which I (as yet) don't have in my table. I was going to just run the edge of the jig along my fence, and then figured that it might wander away from the fence a touch - thereby affecting the accuracy of the joints. Here's the potentially dangerous idea : what if I clamped a straight edge parallel to the fence, perfectly spaced to ensure that the jig couldn't move laterally between the two fences. Is that dangerous? I know it's dangerous to use a rip fence and a cross cut fence on a tablesaw, for the same cut - but this isn't the same - both fences are parallel.

Any advice would be much appreciated.

Matthew
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Last edited by matt1710; 02-26-2011 at 05:58 AM.
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post #2 of 8 (permalink) Old 02-26-2011, 08:03 AM
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I don't know how hard rimu is but it sounds like you might have been better off making an even more shallow cut, say 3mm at a time. Clamping the work piece to the mdf backer and applying downward force plus force against the fence would also help.
I don't think it's ever a good idea to trap wood between 2 fences because if something does go wrong, the only place it has to go is up, potentially towards your face.
I'm no pro though, I just go with what i know. Yo.
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post #3 of 8 (permalink) Old 02-26-2011, 10:23 AM
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Hi Matt

Once you get the table saw out of your head your jigs will work right..

The router table works on the round so to speak, if you use a guide in your router table it will always be right on. a slot for the guide in your jig will keep it running true to the bit

The slot in the router table for a miter sled is the table saw way.


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Quote:
Originally Posted by matt1710 View Post
Hi

I've just completed my first router table, and gave it a run today. All went well although I'm slightly fearful that I was making a mistake in feeding a long (circa 300mm) batten (circa 25 x 25mm) across the bit, with one end butted against the fence and the other free. I made many passes as had to make a total of 10 slots, each about 20mm wide by 12mm deep) and although most went without a hitch, there was the odd pass when something went wrong and the stock jumped a little and got a little ripped up. I did have a feather board on the fence (vertical) and a piece of MDF behind the batten. I'm soon to build a cross-cut sled with toggle clamps - I would have used that had it been ready. I've done a quick diagram (attached) of my setup - and indicated where I was getting a little tear out - but not on every pass. The bit was almost brand new, a Trend 3/4" dado cutter. The wood was quite hard (rimu) , I was taking about 6mm (height of cut) at a time, and tried 15,000rpm and 12,000rpm. Bit speed didn't seem to make much difference - I also varied the feed speed. I did notice the wood was burning a little - that would indicate too high RPM, or too slow feed - or both - correct?

Anyway, my next idea is to build a finger joint jig as demonstrated here (Finger Joints (Box / Comb joints) - by Steve Maskery @ LumberJocks.com ~ woodworking community) - check it out, it's a very fine & safe jig. The author uses a mitre track, which I (as yet) don't have in my table. I was going to just run the edge of the jig along my fence, and then figured that it might wander away from the fence a touch - thereby affecting the accuracy of the joints. Here's the potentially dangerous idea : what if I clamped a straight edge parallel to the fence, perfectly spaced to ensure that the jig couldn't move laterally between the two fences. Is that dangerous? I know it's dangerous to use a rip fence and a cross cut fence on a tablesaw, for the same cut - but this isn't the same - both fences are parallel.

Any advice would be much appreciated.

Matthew



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post #4 of 8 (permalink) Old 02-26-2011, 12:25 PM
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I don't think it is necessary to abandon all lessons learned about one tool when working with another, but it's essential, I think, to remember the differences in how they work.

The basic approach shown in your diagram, Matt, is fine, I think - essentially, a large push block riding on the fence to provide stability. What isn't included, however, is a means of keeping the stock stable with respect to the push block, so both the push block and the stock act "as one" in relation to the bit. Even minor variations in positioning can be problematic at times. Edge-clamping the stock to the edge of the push block by some means would solve that issue.

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post #5 of 8 (permalink) Old 02-26-2011, 02:18 PM Thread Starter
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Ok - so I wasn't doing anything too bad. Sounds like my cross-cut sled would have been the answer. I posted a scan of it a little while back - see here : http://www.routerforums.com/jigs-fix...ow-strong.html

You can also click on 'View matt1710's Uploads' under my avatar picture, and the scans are there. The sled (and it's long grain brother) look pretty handy.

How about my idea of using twin parallel 'fences' in lieu of a mitre track?

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post #6 of 8 (permalink) Old 02-26-2011, 09:11 PM
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Quote:
Originally Posted by matt1710 View Post

. . . How about my idea of using twin parallel 'fences' in lieu of a mitre track?
As your mother used to say, "It depends."

That is, it depends on what is being done, and how the stock is being held. If the secondary parallel guide is used with a sled type of jig that holds the stock independent of the guide, it will act much like a feather board that has no "give" - except that the feather-board substitute is guiding the jig, not the stock.

Obviously, you'd want to ensure that the guide edge is straight, and clamped such that there is no binding of the sled through the range of travel. A well-jointed edge (smooth, straight, and square) that is waxed to reduce friction while keeping tolerances reasonably tight, should be OK.

What you'd want to avoid are situations in which the secondary guide could pinch or mis-guide the stock behind the cut. For example, the reason one shouldn't combine a miter gauge and a fence on a table saw is that as the stock is moved through the cut, any lack of precision in parallel will shift the vector of the cut in relation to the blade. That can result in the already-cut section of the stock binding on the rising teeth on the back side of the blade, causing a kick-back. Kazing, board through chest, or board through skull, are among the options.

- Ralph
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post #7 of 8 (permalink) Old 02-27-2011, 03:00 AM
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Quote:
Originally Posted by matt1710 View Post
Hi

I've just completed my first router table, and gave it a run today. All went well although I'm slightly fearful that I was making a mistake in feeding a long (circa 300mm) batten (circa 25 x 25mm) across the bit, with one end butted against the fence and the other free. I made many passes as had to make a total of 10 slots, each about 20mm wide by 12mm deep) and although most went without a hitch, there was the odd pass when something went wrong and the stock jumped a little and got a little ripped up. I did have a feather board on the fence (vertical) and a piece of MDF behind the batten. I'm soon to build a cross-cut sled with toggle clamps - I would have used that had it been ready. I've done a quick diagram (attached) of my setup - and indicated where I was getting a little tear out - but not on every pass. The bit was almost brand new, a Trend 3/4" dado cutter. The wood was quite hard (rimu) , I was taking about 6mm (height of cut) at a time, and tried 15,000rpm and 12,000rpm. Bit speed didn't seem to make much difference - I also varied the feed speed. I did notice the wood was burning a little - that would indicate too high RPM, or too slow feed - or both - correct?

Anyway, my next idea is to build a finger joint jig as demonstrated here (Finger Joints (Box / Comb joints) - by Steve Maskery @ LumberJocks.com ~ woodworking community) - check it out, it's a very fine & safe jig. The author uses a mitre track, which I (as yet) don't have in my table. I was going to just run the edge of the jig along my fence, and then figured that it might wander away from the fence a touch - thereby affecting the accuracy of the joints. Here's the potentially dangerous idea : what if I clamped a straight edge parallel to the fence, perfectly spaced to ensure that the jig couldn't move laterally between the two fences. Is that dangerous? I know it's dangerous to use a rip fence and a cross cut fence on a tablesaw, for the same cut - but this isn't the same - both fences are parallel.

Any advice would be much appreciated.

Matthew
Basically I can't see anything wrong with your set-up, the only changes that I would make are: cuts no deeper than 3mm in hard wood and a strip of 80 grit paper on the edge of the MDF pusher. As you can see in these shots, the set-up is virtually the same as yours but because of the size of the stock, a pusher wasn't required, also as the material was soft, I took about 6mm cuts.
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post #8 of 8 (permalink) Old 02-27-2011, 04:37 AM Thread Starter
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Thanks very much for all your input gentlemen! Actually, I was quite proud to emerge from the shed after my first hour on the RT, with 8 fingers and 2 thumbs!
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