# Simple But Precise Project



## RestlessMind (Dec 29, 2009)

I am working on a project that requires a base/chassis that is a square or disk about 7 inches in diameter/length,width and 1/4 inch thick.

I need to make these incisions (shown in the diagram below):

http://i538.photobucket.com/albums/ff341/the_cake_is_a_lie/M-A2TEMPLATE.png

The lines in the diagram must be incisions going all the way through the wood, and be just a tiny bit wider than 1/8 of an inch. They are at 22.5-degree angles from each other. The dot in the center represents a hole that must be at least 3/4 inch thick.

I tried to do this by hand with a Dremel with a bit like this:

http://www.dremel.com/en-us/AttachmentsAndAccessories/Pages/AttachmentsDetail.aspx?pid=561

And it turned out... well... here's a picture of the finished project (ignore the markings on the wood).

http://i538.photobucket.com/albums/ff341/the_cake_is_a_lie/Picture002-3.jpg

The problem is, the cuts are... sort of straight, and a few of them are not at the correct angle. That messes things up quite a bit. Now, things don't have to be laser-precise, but I'd like them to be nice and well done.

My question is; what would be the best way to make these cuts? I have access to a powersaw, the Dremel mentioned above, and a jigsaw. Also, what would be the best wood to use?

Thank you very much!


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## phinds (Mar 25, 2009)

Looks to me like the tool you used can make the cuts just fine, but what it CAN'T do is make them straight without a guide jig. That's what you need. Shouldn't be too hard to make one (he says with the smug knowledge that he doesn't have to do it himself ).


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## cabinetman (Jul 5, 2007)

I would start with a square and use a straightedge as a guide. It can be as simple as a straight piece of solid wood. Starting with a square allows you to clamp the straightedge to the substrate, and support the square from moving around. 

You have 8 rays to cut that are in line, You could just mark on the straightedge the start and stop point for each ray (as they break in the middle, and mark the base of the Dremel. 

Position the straightedge so the Dremel base rides on the right side of the straightedge while you move the Dremel away from you. A Dremel should give smooth cuts in 1/4", but a router with a straight cutter would be better.

As for what wood/plywood to use, that would depend on the use and purpose of this piece. It wasn't stated.


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## RestlessMind (Dec 29, 2009)

Thanks for the tips!

Ah, the purpose is a base/chassis for several rectangular pieces that will fit in the slots, and need to be easily yet snugly placed in and removed for rearrangement.


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## mics_54 (Oct 28, 2008)

I wasn't sure about the hole in the center by your disctiption but I think the idea is correct. A dremel with a guide or a router with a jig would certainly work.


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## pianoman (Jan 16, 2008)

I think a template with a 1/4" pattern bit with 1/4" bearing would work. The hard part is the fraboracating of the template. And that`s kind of a waste...if you only need one base. I have made templates with 1/4" ply (without voids) that seem to hold up for a good while. Since all the plows are the same...a template with one straight line could be pinned or clamped to an oversize disc.for each pass. And then again...there`s the router mounted to a RAS trick using the center hole as a pivot. I made one of those once... Rick


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## RestlessMind (Dec 29, 2009)

mics_54 said:


> View attachment 12512
> 
> 
> 
> I wasn't sure about the hole in the center by your disctiption but I think the idea is correct. A dremel with a guide or a router with a jig would certainly work.


Whoa! Impressive 3d thing! How did you make that?

Oh yes, that's correct. The hole will probably be a little smaller, though.



> I think a template with a 1/4" pattern bit with 1/4" bearing would work. The hard part is the fraboracating of the template. And that`s kind of a waste...if you only need one base. I have made templates with 1/4" ply (without voids) that seem to hold up for a good while. Since all the plows are the same...a template with one straight line could be pinned or clamped to an oversize disc.for each pass. And then again...there`s the router mounted to a RAS trick using the center hole as a pivot. I made one of those once... Rick


I thought that I would just draw on the wood with a pencil and then follow the lines, I just need a way to make sure my cuts are straight. Do you think making a template first would be better? I don't even know how I would make sure the template's lines are straight, either.

I have a Dremel guide like this one:

http://www.reality.net/case/photos/dremel-guide-4.jpg

That assures that I get the right depth, but I'm going all the way through the wood anyways. I just need to make sure the cut is straight.


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## mics_54 (Oct 28, 2008)

I believe I would make a sliding indexible jig that sits under a fixed position dremel that can be raised and lowered. The complexity of the tooling would depend on how many of these you want to make. 

From the mysterious nature of your query I presumed this was some type of invention and that reproduction may be an interest rather than a one off type project.


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## BHOFM (Oct 14, 2008)

With the limited tools you have, I would lay it out.
Drill a 1/8th" hole on each end of the cuts and
then with a straight edge make the cuts with a
razor knife. It will take some time but they will
be straight and clean. A little sanding and they
will be near perfect.

A router with a jig would be the ideal way to
do it if you need more than one.


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## RestlessMind (Dec 29, 2009)

mics_54 said:


> I believe I would make a sliding indexible jig that sits under a fixed position dremel that can be raised and lowered. The complexity of the tooling would depend on how many of these you want to make.
> 
> From the mysterious nature of your query I presumed this was some type of invention and that reproduction may be an interest rather than a one off type project.


Actually, I only need one of these frames, lol. I doubt I'll be manufacturing them.



> With the limited tools you have, I would lay it out.
> Drill a 1/8th" hole on each end of the cuts and
> then with a straight edge make the cuts with a
> razor knife. It will take some time but they will
> ...


Cut through 1/4 - 1/2 inch of wood with a razor knife? Perhaps if I used balsa wood... what type of razor knife?


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## BHOFM (Oct 14, 2008)

RestlessMind said:


> Actually, I only need one of these frames, lol. I doubt I'll be manufacturing them.
> 
> Cut through 1/4 - 1/2 inch of wood with a razor knife? Perhaps if I used balsa wood... what type of razor knife?


I said it would take some time. I did this in 1/8 in
about two minutes, three passes on each side.










Just make light cuts and clean out the slot now
and then.


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## mics_54 (Oct 28, 2008)

Perhaps somebody can make it for you? I get the impression you really aren't into the woodworking thing. Maybe I am totally wrong. Would some material other than wood work better for you? If you would be a bit more forthcoming about it's purpose I could probably make some suggestions. It looks like some type of QC lab testing equipment.


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## BHOFM (Oct 14, 2008)

After playing with this in the shop, the tool of choice
will be a scroll saw.

Quick and easy, leave the line and file to size.


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## RestlessMind (Dec 29, 2009)

> I said it would take some time. I did this in 1/8 in
> about two minutes, three passes on each side.


I have patience. :icon_smile: I was just surprised to hear that.



> Just make light cuts and clean out the slot now
> and then.


It sounds like a good way to do it!



> Perhaps somebody can make it for you? I get the impression you really aren't into the woodworking thing. Maybe I am totally wrong. Would some material other than wood work better for you? If you would be a bit more forthcoming about it's purpose I could probably make some suggestions. It looks like some type of QC lab testing equipment.


Well I don't have much experience in woodworking, but I don't mind it. :icon_smile: Its an experiment/invention idea, but I'm just doing it on my own out of interest. The only restriction on materials I have is that the base must not be metallic.

A question about balsa wood: if it was pressed on by a metal object like a hammer or something with about 2 pounds of force, would that be enough to smash it? Because I think balsa wood would be easy to make the cuts in, but I also don't want it to be weak either.


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## BHOFM (Oct 14, 2008)

I don't think balsa is the way to go. 

There are several ways to do this.

Make the a top plate of 1/8 ply, easy to work with
and then glue it to a piece with the cuts under it.
the under piece cuts would not need to be as precise
as the top. Just clearance cuts. Drill a row of holes
and cut between them.

Or you could make some 22.5` wedges and glue
them up using 1/8" spacers at the ends.

If you could find a scroll saw it would make it
easy.


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## RestlessMind (Dec 29, 2009)

> I don't think balsa is the way to go.


Too soft I suppose?



> Make the a top plate of 1/8 ply, easy to work with
> and then glue it to a piece with the cuts under it.
> the under piece cuts would not need to be as precise
> as the top. Just clearance cuts. Drill a row of holes
> and cut between them.


So get two 1/8 inch thick plywood sheets, make the cuts in both, then glue them together as to make a 1/4 inch sheet with the cuts in it?

The method sounds good as well. What kind of knife should I use? The picture of one somebody posted looked like a box-cutter.



> If you could find a scroll saw it would make it
> easy.


Unfortunately I don't have access to one of those.


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## BHOFM (Oct 14, 2008)

I posted the pic with the razor knife. 

Would the lower, bottom need to be as accurate as the top?
It would make it a lot easier if it didn't.
The bottom would just be for support.

If you buy a razor knife for this type work, get one with a screw
lock, not a button. The one with the screw is much more secure.


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## RestlessMind (Dec 29, 2009)

> Would the lower, bottom need to be as accurate as the top?
> It would make it a lot easier if it didn't.
> The bottom would just be for support.


What do you mean? I think the bottom and top should be of the same quality. Just to make sure we're on the same page here; the bottom and top pieces would be two of these glued together as to make a thicker product, correct?












> If you buy a razor knife for this type work, get one with a screw
> lock, not a button. The one with the screw is much more secure.


Okay!


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## BHOFM (Oct 14, 2008)

It will be hard to make two identical pieces by hand.
I thought the bottom could have maybe wider slots?
To solve any alignment errors.


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## RestlessMind (Dec 29, 2009)

What would be the point of the bottom having wider slots?


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## RestlessMind (Dec 29, 2009)

Does anybody know what kind of wood is being cut in this picture?


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## BHOFM (Oct 14, 2008)

RestlessMind said:


> Does anybody know what kind of wood is being cut in this picture?


1/8" birch plywood.


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## BHOFM (Oct 14, 2008)

RestlessMind said:


> What would be the point of the bottom having wider slots?


Less of a problem lining up the two pieces.


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## woodnthings (Jan 24, 2009)

*You will have to make a few jigs to get one right*



mics_54 said:


> View attachment 12512
> 
> I wasn't sure about the hole in the center by your disctiption but I think the idea is correct. A dremel with a guide or a router with a jig would certainly work.


I would start with a piece of plywood to hold and rest your work piece on the table saw with a circle divided into 12 equal angles stuck to your workpiece with a registration mark or index point and a center hole of 3/4" as a pivot. The blade should be the proper thickness to achieve the width you desire in your slot . You might have to stack 2 blades together. You'll need a way to hold the workpiece in place as you rotate the workpiece to each cut around the wheel. Maybe a screw and a wooden pressure tab.

The first cut will be into and through the plywood while you *raise the blade only* do not move the jig. The jigs stays clamped to the table and against the fence for the whole operation. Each time you raise the blade into the next angle after indexing the mark on the circle with the registration mark. You need only raise the blade until it shows enough from the top to give you the correct length on the bottom. You can clean up the remaining part of the slot with a file.
This is clear in my mind, but I may have not explained it fully. :blink: bill


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## RestlessMind (Dec 29, 2009)

> 1/8" birch plywood.


Ah! Do you think I could get that at Home Depot or something?



> Less of a problem lining up the two pieces.


Oh I see.



> I would start with a piece of plywood to hold and rest your work piece on the table saw with a circle divided into 12 equal angles stuck to your workpiece with a registration mark or index point and a center hole of 3/4" as a pivot. The blade should be the proper thickness to achieve the width you desire in your slot . You might have to stack 2 blades together. You'll need a way to hold the workpiece in place as you rotate the workpiece to each cut around the wheel. Maybe a screw and a wooden pressure tab.
> 
> The first cut will be into and through the plywood while you *raise the blade only* do not move the jig. The jigs stays clamped to the table and against the fence for the whole operation. Each time you raise the blade into the next angle after indexing the mark on the circle with the registration mark. You need only raise the blade until it shows enough from the top to give you the correct length on the bottom. You can clean up the remaining part of the slot with a file.
> This is clear in my mind, but I may have not explained it fully. :blink: bill


I only have access to a miter saw, perhaps I could do the same with that though. The length of the slots is of no real concern, but they must stop in the center. Being at proper angles, though, is of most importance. The hardest part would be getting the 1/8th inch slots right with the blade.


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## BHOFM (Oct 14, 2008)

Yes, it comes in 5'X5' sheet, but you can also get smaller pieces
at a hobby shop, aircraft ply.

https://www.discountrocketry.com/fi....html?osCsid=745d82a407b10e9c3906d2b1af4e9d9d


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## RestlessMind (Dec 29, 2009)

Ah alright!


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