How much machining precision to expect from benchtop mortiser?

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Forum topic by jcwalleye posted 01-11-2013 04:39 AM 821 views 0 times favorited 2 replies Add to Favorites Watch
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306 posts in 3066 days

01-11-2013 04:39 AM

Topic tags/keywords: mortiser

I just assembled a new benchtop mortiser and was wondering how tight of tolerances it should be machined to. It’s a low end model, but not the lowest and I plan to write a full review when I get some issues worked out.

Basically the machining is not of the highest precision. First, the fence was not square to the base by about .007”. The chisels were also not square by about the same amount. I shimmed both of those to within a couple of thousandths, using a couple plys of beer can aluminum between the base and one edge of the column.

A little more serious problem is that the face of the fence is not very flat, wavering about .010” or one one hundreth of an inch at the biggest gap of the length. I don’t see any way to eliminate that short of having that surface re-machined.

Is that an acceptable amount or is it something to be concerned about. It doesn’t cut the cleanest of mortises, but some of that is to be expected from lower end equipment. And the chisels aren’t the highest quality and will benefit from some honing, which I plan to do next.

Thanks for your opinions.

-- Trees, a wonderful gift --Joe--

2 replies so far

View Loren's profile


10373 posts in 3641 days

#1 posted 01-11-2013 04:44 AM

The tenon shoulders play a big role in effective
mortise and tenon joints. Probably where your
mortiser will annoy you is the clamp and, possibly,
flex under working pressure. Try some mortises
with your smallest chisels and check them for
alignment. Then try some with your biggest
chisels and check those.

Realistically your mortiser is likely to cut more
consistent mortises than cutting them by hand
with chisels, yet the hand method is accurate
enough that lots of people still do it.

View mbs's profile


1656 posts in 2933 days

#2 posted 01-11-2013 05:23 AM

I have a mortiser that has the same issues you’ve described. I don’t use it unless I’m making holes for square pegs because I have other tools that do a much better job at making mortises than the bench top mortiser. If it were higher quality I may use it more.

-- Sorry the reply is so long. I didn't have time to write a short reply.

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