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portable handheld mortising jig "build blog" #3: the determining and building of the guide rails

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Blog entry by hobby1 posted 321 days ago 772 reads 0 times favorited 3 comments Add to Favorites Watch
« Part 2: building angle brackets for base subassembly Part 3 of portable handheld mortising jig "build blog" series Part 4: the finalizing of the dovetail slides, and prefit everything together »

At this point I have everything screwed together for the first subassembly.
It’s time to work on the axis travel arrangement.

I thought about 3 ways to do this, first was with a linear bearing approach, where I would ream a hole through a piece of steel to be the bearing, and make 4 of them, then make some sort of rail system out of round bar stock for the bearings to run on, however, that would mean some elaborate bracket sytem to hold the rails up, which would mean 4 rails 2 for each axis, then I thought about linear beraring surfaces, with simple rabbets cut on workpieces (guides) to be put together, to form a square channel rail system, lastly the good ole dovetail rail system, I’ve built quite a few projects using dovetail slides they are very efficient, so opted to use the dovetail method, for the linear slides.


Now to achieve the “X and Y” axis movement, I need a central dovetail slide block, which will have perpendicular dovetail grooves cut in it.
I need a thick enough stock to do this with so 1” bar stock will suffice for this.
Here the x y directions are drawn out for me to use as reference.

Now the design of this whole project is dictated, with the available bar stock I have on hand, in my metal bin, and because of that, I need to have the right sequence of machining operations, so as to not cut something wrong size.

I want to start cutting the dovetail slides, however the width of this piece,

determines the distance of the x axis movement on this assembly here

and the width of this piece

determines the length to cut off this piece here
which is the ‘Y’ axis movement,

Now I can start the dovetail slides,
first cut the stock to rough size, then flycut all 4 pieces to get good straight reference flat edges.

and finally start cutting the dovetails on the individual rails,

when all 4 are done, then the central block can be dovetailed.



3 comments so far

View stefang's profile

stefang

12947 posts in 1968 days


#1 posted 320 days ago

Very interesting Hobby1. I’m wondering how you rough cut the dovetail slides shown on the 4th photo from the bottom. I’m still wondering what this is going to look like and how it will work when finished. The suspense makes it all the more interesting, meanwhile it’s fun getting some insight into the designing/machining process.

-- Mike, an American living in Norway.

View kaerlighedsbamsen's profile

kaerlighedsbamsen

465 posts in 347 days


#2 posted 320 days ago

Nice to see some fine metalwork on this site. Looking forward to more parts!

-- "Do or Do not. There is no try." - Yoda

View hobby1's profile

hobby1

282 posts in 931 days


#3 posted 320 days ago

Mike:
The stock I made the slides for was 1/2” thick by 6” wide by around 5” long, aluminum flat, it was to long to use my bandsaw in the horizontal position, so I used it in the vertical position, and cut the pieces by hand, to a little over 1” in width, I have out in my outside woodshop one of those harbor freight horizontal/vertical bandsaws, again another Christmas present back in the early 2000’s when these saws were very, very affordable, now the prices on all these machines, I have are skyrocketed, I’m glad I bought them when I did.

If I needed clean edges, I could have made a set up to clamp this workpiece in my saw, and use it in the vertical mode, if I did, it would cut extremely smooth, where any milling to be done would be just to do a little straightening up, to make sure it is parrallel, those saws cut very smooth.

I just discovered lately on another project I did for upgrading my milling machine, that using the bandsaw in the vertical mode, is very easy to cut all kinds of curved shapes in 1/2” thick aluminum, something I never thought possible before.
I use it alot now when it comes to scroll cutting metal thicker than 1/4”. —————————————————————

Kaerlighedsbamsen:

Thanks for following along, machining parts is a lot of fun.
I must say though, I’m not a metalworker, I rather work with wood, I enjoy building furniture and arts and crafts projects, but I do enjoy model engineering, and metal is the best medium for mechanical parts when it comes to small scale working models, however I’m finding more uses for metal in my woodworking which using this variety opens up more unique designs for me.
Here is an example of incorporating metal in my woodwork.

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