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Adjustable Stops

Some  years ago I needed some way of ensuring that I could make a batch of repeatable and accurate mortise and tenon joints.

I raided my scrap box and came up with the following simple and very cheap jig. It was very quickly and (crudely) made but was so successful for me that I have never bothered to clean it up. I took a piece of 20mm alloy angle the same length as the white plastic guide rail and drilled two fixing holes. These match up to the guide rails. I used longer Philips head screws to fix down. 

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I used the Woodrat to mill an 8mm slot in the upright side of the angle ending two and a half inches from either end. Any further and I think stiffness would be compromised. I used  an ehss spiral cutter as used in the window industry to cut the slot. (these work extremely well on wood, they are designed to last on abrasive anodized alloy) An old carbide cutter run at a lower speed with some wax lubricant will do just as well.           

               I cut two stepped stops from alloy, you could use plastic, brass, steel or even hardwood, then drilled and tapped them to take locking screws and washers. The stops are made so that they can be flipped in either direction to extend the operating range. 

 

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I used bolts that matched the collet spanner purely because they were to hand, Allen bolts would probably be a bit more professional. 

  I just used a piece of bar in the router to run between the adjustable stops. In use, I loosen the stops and extend the bar to engage the required stop. Slide the router until the bit is aligned with the cutting mark then tighten the relevant stop screw and cut away. Simple!

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This cost me nothing to make but checking in the local B&Q D.I.Y store a length of suitable alloy angle and steel  bar (enough to make 3 or 4 sets) cost about 5.0


Sliding ruler

I sometimes find it difficult to see exactly where the cutter position is when cutting north/south and  wanted some method of transferring this to an  adjustable scale on the front of the base plate. I also wanted to avoid using gauge blocks for tenons and to have an easy method of cutting variable spaced box or finger joints.  A tall order but eventually came up with this simple method:-

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 With the above described alloy angle in place , I removed the stepped stops and placed an alloy ruler on edge against the slotted rail as shown. I drilled a counter sunk hole in the ruler to directly align with ground end of the router bar as shown here.

Now when the router bar is engaged with the ruler it holds the ruler against the rail and causes the ruler to slide north/south when the router plate is moved. border="0"

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Next make a slotted, adjustable position marker as shown and fix with the front rail screw. You may have to use a longer screw. Cut the marker from any suitable material so that the ruler is a snug sliding fit against the rail. I waxed the back of the ruler for a silky slide.

  Lower the router bit to align the cutting edge on the start cut line and move and lock the marker to any recordable position on the ruler. Remember to add or subtract the cutter diameter before cutting!!!  Here the marker is zeroed at the four and three quarters mark plus quarter inch because I am using a quarter inch bit.

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It is now a simple matter to plunge and draw the router towards you any distance or incremental distance as measured against the sliding ruler.

To make quarter inch finger joints, with the wood cammed north/south, bring the cutter up to just touch the rear edge and set and lock the marker to a whole inch line on the ruler. Pull forward a quarter inch, fix the router plate with the star knob and cut. Loosen the knob, slide forward another half inch, lock the star knob and cut again. Repeat as required. Don't use exact spacing but allow a very slight adjustment for fit and glue line.

It is very quick to remove the ruler and replace the stepped blocks.

click any photo to enlarge


Drill some holes!

Here are some simple modifications to extend your Woodrat facilities. My machine is six years old and I understand if you are reluctant to drill some holes in your shiny new one but let me assure you that I had no problems. I don't know how this would affect your warranty so please check first.

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This is what I did. I carefully marked the position for three holes, just one would be OK. Take care not interfere with the inside web or be too close to the crank handle. Use a 6.5 mm drill and thread with an 8mm tap. This allows the use of the star knob to fix down clamps....

 

Such as this toggle clamp here

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  or a piece of acrylic as here.

If you make a T shaped acrylic cursor with a scratch line which is vertically in alignment with the cam lock fence as shown here  then it is a simple process to clamp a ruler (18" thin stainless is best) to create a very accurate left and right tracking scale. Position the cutter, take account of the cutter diameter, slide and zero the rule, clamp and cut in the usual way.

 

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With this system you can, for instance,  create a master comb template for making finger joints. This master should not be exactly spaced or the joints will be too tight but be very slightly spaced to..............

 Allow for glue and fit. Clamp like this  and cam a pawl at an angle like this  so that it be sprung out of engagement to track to the next cut.

 

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Create the master in conjunction with the ruler like this.   

 


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This site was last updated 11 July, 2009