Circle/Radius Cutting Jig - Page 3 - Router Forums
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post #21 of 46 (permalink) Old 12-19-2019, 11:53 PM
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I got to thinking about this, and decided that I could use my CNC router to make a jig. I stopped at 13" diameter, but basically it could be made to handle any size by calculating more location holes.


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post #22 of 46 (permalink) Old 12-29-2019, 10:16 PM Thread Starter
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Rick,

Nice first design. I've attached Pat Warner's circle jig which I have found to the be the best out of all the circle jigs I've used. ...snip...

I copied Pat's design in MDF. I would suggest cast acrylic because it's super handy to see thru the base. My base has seen quite a bit of use and the couple of coats of thinned polyurathane varnish is holding up well. Some paste wax on the bottom helps too. Below are a couple of pics of the build.
DG,

Thanks. I am just getting back to this project after a rather extended hiatus. This fall was extremely busy for some reason and THEN the holidays came. Whew.

In sitting down with my design and the template that I need to route the circles for, for the ships ladder, I came to realize my jig, as is, cannot cut a small enough circle. The pin has to inside the circle inscribed by the router base. I like the Pat Warner design and think I will make one like it. I will probably do it in MDF, as that is what I have. But, I am going to the "city" tomorrow, so maybe I can find some suitable acrylic. I kind of doubt it. Baker City, OR is 10k population in cattle country in NE Oregon. Although there are hardware stores, there really aren't any beyond the stock TV or DIB and I don't recall ever seeing acrylic thick enough. 1/4" yes, but nothing thicker. Gotta check, tho.

Funny. I do not mean to take any credit for an original thought, and maybe I was just recalling having seen the photos you posted, but before coming back on here, I thought of something remarkably similar, with an adjustable bar extending under the base. At first, I thought of just making a base and drilling a hole at the hopefully right location and make it a one-off. But then, I thought I should make it adjustable.

I've printed Pat's design and save the photos you posted. I will plan this out (my code for CAD it out) tonight and see what I can find for base stock tomorrow.

Thanks,

Rick

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post #23 of 46 (permalink) Old 12-30-2019, 08:33 AM
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But, I am going to the "city" tomorrow, so maybe I can find some suitable acrylic. I kind of doubt it. Baker City, OR is 10k population in cattle country in NE Oregon. Although there are hardware stores, there really aren't any beyond the stock TV or DIB and I don't recall ever seeing acrylic thick enough. 1/4" yes, but nothing thicker. Gotta check, tho.

I've printed Pat's design and save the photos you posted. I will plan this out (my code for CAD it out) tonight and see what I can find for base stock tomorrow.
Try freckleface.com for cast acrylic. I have the same problem trying to source raw materials locally.

There are some subtle aspects to making this base so doing it in MDF the first time will be good practice. If your 1st one is good, you can use the MDF as a template for making more of them.

Even if you are doing this w/a CNC router, I would drill a 1/4" hole for the spindle location. Then mount a 1/4" drill rod in the 1/4" router collet. It will let you determine the handle orientation for a particular router. Secondly, surprise, you'll find some tolerances in base plate hole patterns. At least w/this method, you know the base will mount easily on the router. While the PC 690 hole pattern is a near universal standard, the orientation of the handles to the hole pattern is not. It's not until you use Pat's edge guide that you realize how important this is.
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post #24 of 46 (permalink) Old 12-31-2019, 12:54 AM Thread Starter
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Thanks, DG. Freckleface is a great site.

In 1972, I used 3ft long sections of 12" dia. plexiglass tubes as experimental chambers for rapid water exchange tolerance tests of fish exposed to heat and cold shock experiments at a nuclear power plant on the Hudson River (Indian Point). I brought one with me when I left in 1973. I carted that thing around for years, hoping to make a vertical, fish tank. Never did. It became a rolled map storage container and eventually degraded to the point it could not be used as a fish tank. I disposed of it, grudgingly, when I move to my current location in 2016. That kind of acrylic tube is ridiculous expensive now.

I was sorely disappointed in my search today. Not even 1/4" could I find in Baker City? I'm going to make something out of MDF to get me through this project and come back to making a decent circle jig another time. I do not want to be distracted from getting this ladder done this week. I put it off from Sept., not that it will get much use until Spring, but it is just one of those "things" hanging over me if I don't.

Nice advice on orienting the handles. I fiddled with that a bit, trying to figure out not only which way the handles should go, but also the plunge release lever, actuated by my left thumb. I found it much more comfortable to have it on the outside of the rotation and on the inside. But, I realize that changes as the router rotates, but for starting the cut with a plunge, it works best on the outside.

Rick

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post #25 of 46 (permalink) Old 01-01-2020, 01:53 AM Thread Starter
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Made the base plate for a Pat Warner style circle jig today and used it to cut the radii for a router template, for making the hand hold cutout in the ships ladder stringers. I printed and pasted a full size pattern for the base plate on to a piece of 1/2" MDF and band sawed the outside and sanded to the lines on a disc sander. Then, drilled a hole for inserting a scroll saw blade and cut out the center hole, then sanded it to the line on a spindle sander. Milled the slots on my vertical mill with DRO, but I don't have the right metal stock for the pivot arm, so did not make that much of the jig today. Instead, for the immediate need, I drilled a 1/4" pivot hole at the right distance from the center of the jig, which can be seen just inboard from the 1/4" wide clamping slot.



Here is a test run in a scrap piece of MDF.


Rats, I was going for 7.040". Missed it by a smidge


Cutting the radii on the production template. I need to work on dust collection. Dust went everywhere and these were just 1/2" deep cuts. The shopvac hose didn't do a thing, and I even had the shopvac turned on. Chips will come off of the stringer lumber rather than dust as fine as what came off of the MDF, but I still need dust collection very close to the cutter. A dust hood came with the edge guide, but I haven't figured a way to mount it on the router bases yet.


Straight edges were milled out on my vertical mill. I used a laser center finder to set the stock up, splitting the beam over the edge of the radius and then shifting over about 0.150" to rough it out. Then a final cleanup pass at 0.125".


The completed cutout. I had backed the template up from the mill table with 1/4" Baltic birch plywood scrap, which was screwed to the center section for the second cutout, so the middle part would not be loose as the cut was complete.


There are some small rises at the transitions from the straight edge to the radii. I'll blend those tomorrow with a spindle sander and then it should be ready to try out.

This template is for creating cutouts for the handholds. The cutouts will be started by boring holes on each end with a large diameter forstner bit and the sides with be cut with guided, circular saw plunge cuts. These are going into 12 ft long stringers of 2x12 fir boards. The stringers will be on sawhorses. I have another template for guiding the circular saw cuts and will get close to the final dimensions. Final size will be done with the router/template and a 1/2" dia. straight router bit.

If there is a better way to make the straight cuts in these boards, I'm eager to hear about it. I'm not thrilled about making the plunge cuts in the 2X boards, but that is probably because I haven't done it much. I'll be testing it all out on scrap before going to the stringers.

The hand holds will be finished with a 1/2" radius roundover bit.

Rick
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"Quality is like buying oats. If you want nice, clean, fresh oats, you must pay a fair price. However, if you can be satisfied with oats that have already been through the horse, that comes a bit cheaper."
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post #26 of 46 (permalink) Old 01-01-2020, 01:19 PM
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A lot of work but it looks like you got a good result.

This sort of thing is one of the reasons I bought a CNC machine. I would labor over making a template but could never quite get it perfect. There were always a few imperfections. They were "good enough" and no one ever even noticed but I knew I could do better. Now, with my little CBeam CNC machine, I can crank out perfect templates every time. And I can make much more complex templates too. It's definitely a game changer for me.

Measure twice, cut once and CROSS OUT THE WRONG MARKS.

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post #27 of 46 (permalink) Old 01-01-2020, 01:42 PM Thread Starter
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A lot of work but it looks like you got a good result.

This sort of thing is one of the reasons I bought a CNC machine. I would labor over making a template but could never quite get it perfect. There were always a few imperfections. They were "good enough" and no one ever even noticed but I knew I could do better. Now, with my little CBeam CNC machine, I can crank out perfect templates every time. And I can make much more complex templates too. It's definitely a game changer for me.
I was thinking about CNC as I did this. Thought the use of the mill with DRO was a touch toward that. I like figuring out stuff, like making the templates, but when they take longer than the project they are being made for, it looses its shine.

Rick
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post #28 of 46 (permalink) Old 01-01-2020, 01:56 PM
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I was thinking about CNC as I did this. Thought the use of the mill with DRO was a touch toward that. I like figuring out stuff, like making the templates, but when they take longer than the project they are being made for, it looses its shine.

Rick
DROs are great and for certain things loads faster than designing in CAD, making GCode in CAM (and getting it right) and then actually cutting. And both CAD and CAM have learning curves, sometimes steep. Hard to make arcs-n-circles with a DRO'd mill, though.

I have a Sherline mill and a lathe that I sometimes use to cut steel and such. Wish I had DROs on them. Either that or CNC upgrades. Using calipers gets old fast.

Measure twice, cut once and CROSS OUT THE WRONG MARKS.

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post #29 of 46 (permalink) Old 01-03-2020, 12:17 PM Thread Starter
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I have avoided getting in to CNC with my metalworking machines. I have DROs on my lathe (two axes) and on my knee mill (three axes) and love them. I no longer even look at the dials, except the compound on the lathe.

For some project involving radii, I've used a rotary table on my mills, first a minimill, then a milldrill and now a small knee mill. I'd love to have a full sized Bridgeport type mill and now, in my new location, I have the room, just haven't put the effort into finding one.

Despite not wanting to get into CNC with metalworking, I am very tempted to do so for router work.

Rick
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"Quality is like buying oats. If you want nice, clean, fresh oats, you must pay a fair price. However, if you can be satisfied with oats that have already been through the horse, that comes a bit cheaper."
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post #30 of 46 (permalink) Old 01-03-2020, 12:35 PM Thread Starter
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Default Template Designed for Fixed Base

Completed a dust hood for the plunge base (Bosch 1617EVS) by making a plywood base. The best existing holes for mounting it were 1/4" dia. but were without threads. So, I put in some M6 threaded inserts. The holes were already the correct size for threading oversized (part of the kit) and screwing in the inserts. Very clean. This is the first time I've used threaded inserts in metal (which is what they were intended for in the first place).

It assembled just fine, but I failed to account for clearance of the locking lever. I'd have to move it outward about 1/4", which leaves much larger gaps on both sides, which does not thrill me. As it is, there is not a lot of depth (~9/16") for a 1/4" bit, which is recommended for cutting circles. This would work for 1/2" stock, which may work for most applications.

But... Once this was done and I realized its limitation and thinking I needed more depth, I started thinking about using the fixed base instead. Then I realized my template, which I just completed using the plunge base/circle jig setup, I designed it for use of the fixed base, not the plunge base. The latter is larger diameter and would not work. So, now I need to remake a mount for the fixed base.

There are three threaded holes on the open side of the fixed base, two of which are used for mounting the base plate (M4). I'll have to add at least one threaded hole. But, I think I'll like using the fixed base better. The provided acrylic guard fits in the other side and the dust hood that I fitted to the plunge base will fit closer with less gap that is easier to fill with the fixed base. In looking at how the hood fits, I think it can be modified, by sanding out a radius to match the fixed base and get the hood in closer to reduce the gaps.

I sure hope this one works. I'd really like to get on with the actual ladder project.

Rick
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"Quality is like buying oats. If you want nice, clean, fresh oats, you must pay a fair price. However, if you can be satisfied with oats that have already been through the horse, that comes a bit cheaper."
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