Shop built horizontal mortising table question

[Jim Martin]

Hello All:

I am thinking of building a horizontal mortising table similar to the ones made by Multi-router and by Inca. They slide in two directions and are controlled by a joy stick. Options that I can think of for the slide mechanism range from very expensive linear bearings and shafts to something as simple as a bar in a slot.

A while back I saw a design that used ball bearing drawer slides. That seems like it might be a slick and inexpensive way to go but I wonder how much slop I would get in a design like that. I really like precise control and if I absolutely have to buy linear slides I will but I am interested in saving money too.

Anyone care to comment?

Thanks,

Jim

[Bernard Randall]

Jim,

A lot depends on what shop facilities you have, which ever way you go you need to be able to drill pretty accurately in order to get every thing to line up. If I recall correctly you have a shop bot, what's its accuracy?

My own feeling is that the drawer slides won't withstand the side thrust. I would go one of two ways. Enco sell linear rod and frelon bearings which I have used and are good for a woodshop. If you can support the rods rididly at both ends they are comparatively inexpensive, certainly much cheaper than linearly supported bars, which would also have to have open type bearings. The other option, again from Enco, is drill rod and bronze bushings, much cheaper than the linear bearings, but you need shop facilities to make housings for the bearings and they would also need dust shields.

Of the two the Pacific Bearing frelon closed bearings would be my first choice. Compared to roller ball bearings they are much cheaper, for example

3/4" ID closed pillow block are $37 ea whereas the Thompson is $62 ea. As you would need 4 for each axis it makes a big difference. You probably don't need 3/4" for the short axis, depends really on the unsupported length/

There are certainly other options but nearly all of them involve at least a mill and preferably a metal lathe as well.

Bernard R

[Lowell Holmes]

That might have been the one in FW #141 (March 2000).

[Mark Jerde]

My public library has the book "Shop Accessories You Can Build" (or something like that ) by FWW. IIRC there were plans in there for building one of these. I don't have the book checked out so I can't look up any construction details.

-- Mark

[Bernard Randall]

I have a copy of the book and did a check, it has movement in one plane and uses filing cabinet type slides augmented by hardwood runners. One of the comments the author made was that the longer the slides the more stable the system is; he is using 20" slides.

If you wish I can e-mail you a copy of the article.

Bernard R