I need to make through mortises approximately 2 inches deep (i.e. through). They will be about 3/4 wide and 2 inches long, too.
I have a Delta benchtop mortiser but these seem a bit big for it. What's the best way to get these done? My tempation is to first use my drill press with a Forsner bit to bore out 80% of it. Then use the benchtop mortiser to do the sises, and finally a chisel to clean up.
Is that a good approach or is there a better way?
The wood is maple if that matters.
That'll work ...
I rarely make mortises that thick (3/4"), but generally do use the Delta to do both sides of a through mortise without prior drilling.
By going a little more than half way through on the first pass, then flipping the piece to finish on the opposite side, I find that I end up with a much cleaner exit where the edges of the through mortise will be visible.
The challenge is in meticulous marking, sharp chisels, and _most_ importantly, using the same face referenced against the mortiser fence for both sides.
Best ? Chain morticer from someone like Mafell. About $2K for the little one.
Reasonable way is to find a _SLOW_ drill (you really don't want to be holding a fast hand drill if it snatches) and some big augers. Hog out the waste by drilling. If it's powered and you're not in a hurry, you can manage with small drills and plenty of them. Be as accurate as possible, for care now saves you personal sweat later.
Now clear out the rubbish with a "pigsticker" mortice chisel, the sort with a tapered oval handle, not the usual skinny turned sort. The chisel is also very deep in section, with a rounded top "corner" to the ground bevel, so that's it's useful as a prybar for chips.
If you can find one (let alone use it), a twybill is the traditional tool for this.
Clean up the surfaces with a wide slick, about 2" wide and razor sharp. This has a long handle that you tuck under your arm and push, rather than hammering.
Sounds like a reasonable plan.
I think I might be tempted to use the mortiser first (to define the boundaries of the mortise [slightly undersize]), then use the Forstner bit to complete the through hole, and then make a decision whether to finish up with chisel or mortiser from the other side. Finally, I'd use a chisel to pare the slightly undersize mortise to final dimensions.
My reasoning: This isn't something I do much and so look for all the help I can get from both tools and wood. By using the mortiser first and cutting undersize (by perhaps the width of a pencil line) I give myself a fence of sorts for the Forstner bit
- so that I stay "inside the lines" and have one side of the mortise cleanest right from the beginning. Once I'm all the way through, I'd have a certain amount of latitude in "squaring up" the part cut by the Forstner. The final paring with a chisel would allow me to be as unreasonably precise as I like to be. (-:
Hello, You should have no problem cutting these mortises with your delta unit. I have one too, and it works great. Use you biggest bit and make sure it's sharp with that maple! Just set up your cuts to come in from both sides. Have to make sure that everything stays in line when you flip the piece. Going in to the center also prevents tear out, A good thing! Trust your fence set up and use a stop if you have to and you'll do fine. Best of luck! Michael
Good schedule, tho I'd finish with router and double edge guide if the width of the work permits. 2" deep is substantial for a plunger but with most of the waste gone, it's trimming and should waste nicely. Some pix at the
Makita also has a chain mortiser that goes for about $1,350... but either are overkill for this project.
I'd go ahead and use the Delta bench top mortiser. Do the corners first and then cut in between... I'd either cut them from the side that meets the tennon shoulder or leave the stock thick, cut the mortise, and then rip the stock to width. Either approach should take care of the chip out.
John
Give it a try, but you may find, like I did, for it to often be a waste of time, and material.
As is said, I get better results with sharp chisels and accurate placement (marking and proper face/fence referencing). I chalked that up to the fact that, due to the necessity of multiple plunges, it's rare that machine cut mortise walls are uniform enough ... all those ripples and inconsistencies seem to show up more after ripping than when making clean entry holes up front.
... not always, but just enough to be frustrating, time consuming, and tough on the hardwood budget.
ymmv
Good luck in any event.
Yeah, sorry - I'd rather mis-read the sizes and though we were still dealing with 4" by 2" on the pergola.
3/4" wide ? Anything should manage that.HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.