Powermatic 719T or similar - Is a 3/4" chisel bit too much?

[Dominik Dudkiewicz]

Hi guys,

For those of you with a Jet/Powermatic 719T chisel mortiser, or similar sized hobby mortiser, do you believe that this mortiser can handle a 3/4" mortiser bit (assuming good quality and sharpened well)? If not, what is the maximum practical size that it can handle?

I'm about to put an order in for some LV Premium chisel mortiser bits. I would like to get a 3/4" as I see myself cutting mortises this size, but if the mortiser (which I haven't taken delivery of yet) is not really capable of handling such a large bit properly, then I won't waste my money. What about a 5/8" ?

I will be working in hardwood, with walnut probably the softest timber I would work.

Any advise appreciated.

Cheers,

Dom

[Dave Cav]

I have an Old Iron Newman Mortimer with a foot pedal, and it really struggled with a 5/8 chisel in alder which is relatively soft. 1/2 is no trouble. I think your machine would have a very hard time with 3/4.

[keith wootton]

you will be hanging on lever with both hands and pulling with most of your body weight in hard wood. also, the speed of the large diameter bit will likely char the chips. that said, it will cut cleaner mortises than using smaller chisel to cut a big mortises. i use 3/4" chisel and bit for big thru mortises. with care, they can be perfect, straight from the machine, but it takes vigilance. cut from outside, and use a backer board with no holes exactly where mortise comes thru. also i use a rubber mallet to wack workpiece down solidly square. use your dial calipers to get you dead center in workpiece. get all the slop you can out of the dovetailed ways, and watch the backlash when turning handwheels.

[Bill Adamsen]

I too when reading this a few days ago was thinking ... "with that machine ... white pine, maybe ... hard maple, NFW". I have an older "foot-powered" Yates M40 and it will zip through tougher hardwoods with the 3/8" but you feel the difference as the size increases.

[Dominik Dudkiewicz]

Thanks guys, so looks like the 1/4 to 1/2" set will be all I need as the machine is unlikely to handle anything larger.

I'll just have to make a larger quantity of smaller cuts to get the larger mortises when needed.

Cheers, Dom

[John C Bush]

I use a small Delta mortiser and have hogged out the center of large mortises with a forstner--leaving enough stock to guide the chisel drill--then finish the mortise as usual. Not sure if it saves much time but my arm doesn't get as tired and there is less smoke in the shop.