mortise and tenons... mortise...


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I would use an upcut spiral bit to make the mortices. This type of bit clears the chips from the mortise instead of letting them stay in the slot and create heat. Make sure you tighten the collet. The cutting force tends to pull the bit out of the collet.

I've made mortises using the router's fence and starting and stopping by eye. I've also used home made templates and a guide bushing if I wanted more precision or had lots of mortises to do.

BTW - I assume you are using a plunge router for this.

Mike

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What bit would be correct choice in my router to make a mortise?

Any tips on how to do this? I have seen a few videos here and there on woodwisperer and other sites but any that are truely dedicated videos?

Use the biggest bit you can that fits the size mortice you need. Up cut spirals are probably the best but beware of them spinning out of the collet. I've used an ordinary 1/2" x 2" straight bit most times and with care it is perfectly OK.

What ever bit you use make absolutely sure you only take light cuts. Go in 1/4" rout the full length of your mortice. Go in another 1/4" and do the same. Keep on until you are at the depth you want.

Setting out or making a jig are the critical points to watch. Get either of them right and you're more than halfway there. Most of the time before I aquired a dedicated mortice machine I used to run from the fence, but, Elu 1/2" Industrial routers were well made with rigid easily adjusted fences. It can be beneficial to drill a full depth hole at the start end of the mortice particularly if using a simple two flute straight bit. Not all of them are designed for 'plunge' routing so check first. And remember, always run the router from the left hand end towards the right hand end. If making a mortice wider than your bit, make the first full depth mortice with the fence set so that you are nearest to the edge the fence is running on, then move the setting away from this, finishing with the final run at the furthest distance from the fence. If you don't and you are making a large mortice there will be a tendency for the router to grab and dig in the near side by pushing the fence away from the piece. This can sometimes happen very quickly and ruin your mortice and if you're close to the edge it can break out which is a real disaster.

Hope this helps.

Pete

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If you are looking for a simple mortising jig to use with your router, this is one that I used on a recent project. I found it pretty easy to make and use compared to other jigs I've built in the past.

You use a larger diameter router bit and a guide fence on your router to cut the slot in the jig, and the slot is sized to fit a guide bushing in your router. When you locate the slot, you take into account the offset between the outside edge of the bushing and the edge of the router bit. In my example I used a 1/2" slot/guide bushing and 3/8" and 1/4" bits for the mortises. If I were to do it over, I'd make the slot and guide bushing 3/4" instead so there was more room for chips to exit without jambing up. As others have mentioned, an up-cut spiral bit works well for mortises, although I think you could use a normal straight bit as well without any major problems.

Rory

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What bit would be correct choice in my router to make a mortise?

Any tips on how to do this? I have seen a few videos here and there on woodwisperer and other sites but any that are truely dedicated videos?

Up-spiral bits are my first choice. I have heard of end mills (machinist's territory) being used as well but have not tried them. A standard straight bit will not work very well because there are no cutters in the center of the bit - the only way you can plunge cut with them is to simultaneously plunge and move the router laterally. Straight plunge bits are also available. They do not have the drill-bit-like flutes of spirals that remove chips so efficiently.

Pete talked about taking multiple passes, but I have another approach I like better. I start at one end and plunge the bit to the full depth, then bring the router back up. Then move over and overlap your last cut by about 1/4 the bit diameter, then plunge to full depth again. Repeat until you are at the end, then plunge and, while at full depth, slide the router across the moritse to clean it up. For this approach, you NEED a plunge bit - an up-spiral is best.

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