On 12/9/17 1:09 PM, Unquestionably Confused wrote:
On 12/9/2017 12:03 PM, -MIKE- wrote:
I picked up a barely used Jet JBM-5 mortising machine for 200 bucks!
Not the best score I've ever achieved, but it's a pretty good deal.
I've been wanting one for a while because I'm doing more and more
projects with mortise and tenon joints, so I'm looking forward to
working with it.
Maybe if I get to doing a lot of M&T projects, this will whet my
appetite for a Domino machine.Â* I'm pretty sure I can sell this Jet
for at least what I paid for it.
In the mean time I'll have some fun with it.
Congrats on the score, -MIKE-.Â* Not really a "You Suck" but you can at
least claim to have licked it a bit! 
As others have commented, key to using these is sharp tools and
patience.Â* Take your time and let the mortiser do the work.
Other than sharpness, set up is critical.Â* The old advice of spacing the
inner bit a nickel's thickness was a good generalization but subject to
how fast you're feeding and the hardness of the wood.
Trial and error still seems to be king.
I did find this recently which may or may not work for a specific
application:
"A gap the thickness of a nickel€”roughly 0.072€ť thick€”results in
operating temperatures roughly 40 or 50 degrees higher than if you
increase that gap to 0.117€ť (the gap provided by the built-in spacer, on
the Powermatic PM701 mortiser, used in their testing"). So I now use a
0.125" gauge block to set the gap. The importance of sharpening and
polishing the chisels and bits can't be overstated!
The manual has a chart for the gap corresponding to hard/soft woods and
chisel size.
--
-MIKE-
"Playing is not something I do at night, it's my function in life"
--Elvin Jones (1927-2004)
--
www.mikedrums.com