# How to make a tractrix



## pedromdf (May 12, 2011)

I'm an enthusiast woodworking for many years. I have made furniture, model ships, and now I am making a set of hi-fi loudspeakers. This is my forth pair of loudspeakers, and now I would like to make something "special".

I would like to make a hole in a MDF plank with 40mm deep. The hole has to be a tractrix profile for a tweeter mounting. See the attached file.


I thought of a circle cutting with a milimetric control of radius and deep. The problem is that the for a smaller radius I have a deeper circle cutting. I think a center based circle cutter is'nt the best solution.

Does anyone made something like this, and have a solution?


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## bobj3 (Jan 17, 2006)

Hi Pedro

I think if you use a bit like below it will let the horn fit right into place..


Point Cutting Round Over Bits / #8734

MLCS groove forming router bits

http://www.google.com/#sclient=psy&...=1&bav=on.2,or.r_gc.r_pw.&fp=668845393480168f

========



pedromdf said:


> I'm an enthusiast woodworking for many years. I have made furniture, model ships, and now I am making a set of hi-fi loudspeakers. This is my forth pair of loudspeakers, and now I would like to make something "special".
> 
> I would like to make a hole in a MDF plank with 40mm deep. The hole has to be a tractrix profile for a tweeter mounting. See the attached file.
> 
> ...


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## allthunbs (Jun 22, 2008)

pedromdf said:


> I'm an enthusiast woodworking for many years. I have made furniture, model ships, and now I am making a set of hi-fi loudspeakers. This is my forth pair of loudspeakers, and now I would like to make something "special".
> 
> I would like to make a hole in a MDF plank with 40mm deep. The hole has to be a tractrix profile for a tweeter mounting. See the attached file.
> 
> ...


Hi Pedro:

You're going to want to look at the circle cutting jig that Santé has created. The problem is the 76mm depth. I don't know of a router that would do that kind of depth, even with a bit extension. 

Santé's jig is independent of the centre of the circle so you can cut it without a circle centre. See it at this url: Association Les copeaux . It's in french but that's pretty straight forward. If you have a problem, contact Sante directly.

If you were to cut progressive holes and then stack the result and sand even, that might work.


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## gav (Oct 12, 2009)

Hey Pedro, 
The way I'm seeing it, you just need to make the hole through the 40mm deep mdf, and the remaining 36mm of the tweeter is protruding from the hole. So the 40mm depth shouldn't be a problem. 
I've attached a reworked version of your image.
I would use a normal circle jig and rout 3-4 concentric circles at varying depths. It looks like you already have the ability to work out what depth to rout at particular diameters.
Start with the shallowest cut on the largest diameter, and work your way in to the deepest cut at the smallest diameter.
In the pic that would mean starting in the blue area, then green, then yellow. You could probably even use a drill and a hole cutter to remove the yellow part.

Then it would be a matter of using a rasp file to even out the 'steps' to the curve that you want. Perhaps even a drum sanding attachment on a hand drill could do that part also.


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## pedromdf (May 12, 2011)

I don't know why but I can't reply with quote.

Bobj3,

I have made the first loudspeakers with a plastic horn, but this time I want to make the horn directly on the front panel. Thanks anyway.

Alltunbs

I also think that a circle cutting jig without circle center is the best solution for this application. Thanks for the site information.

Gav

Thanks for your idea, this is what ocurred to me. I have thought milimeter by milimiter in diameter and dept, but I think in pratice is not so obvious. 

With a circle cutting without center I think its possible, associated to your idea of fewer steps.

Thanks for all.
Pedro


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## Mike (Nov 22, 2004)

Pedro, the best solution to your problem is to have a machine shop make your cut with a milling machine. Another option is to have a custom built router bit manufactured for this job. That would only be cost effective if you plan on building lots of these. A bit with these dimensions would most likely run around $400.


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## newwoodworker (Mar 27, 2009)

How about using a thinner material and creating a bigger angled hole in each piece then as you layer them on top of each other it should produces the shape your wanting.


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## pedromdf (May 12, 2011)

I need to make 5 horns, on the front panels of a home cinema loudspeakers system.

I have imagined something like the attached image. Has anybody a simpler (easier) ideia.


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## pedromdf (May 12, 2011)

The idea is to use a Dremel machine.

All the ensemble rotates in the 400x400mm fixed square piece.

I think it's not complicated to do and I hope that the precision is good enough for the 5 applications I need.


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## allthunbs (Jun 22, 2008)

pedromdf said:


> The idea is to use a Dremel machine.
> 
> All the ensemble rotates in the 400x400mm fixed square piece.
> 
> I think it's not complicated to do and I hope that the precision is good enough for the 5 applications I need.


Hi Pedro:

Ok, I've been thinking about this and there is another way but it can get complicated. Go here...

http://www.routerforums.com/woodworking-articles/28343-routers-organized.html 

Take a look at the article. You're looking for skis, pivot frame and angler and angle router base. Here's what I see in my mind. You can create an oversized circular rail, put guide bearings on the bottom of skis and mount an angle-based router on a skis rails. Infinite sizing completely independent and you're able to carve only what you need to get close to your bell shape and use rasp or sand paper for the rest.

Your Dremel is going to be pretty light for this operation. Even laminate trimmers will be too light. I would suggest something about 2 hp or 1500 watt.

The advantage of the above is that it will allow you to angle your cuts for each layer and allow you to stack them as you need. You can achieve something similar by using a 45 degree bit of an appropriate size and skis on bearings. If you send me a PM, I'll send you some notes on skis that you may find helpful. Also search out Harrysin's article on Skis for beginners. I'm not in favour of threaded ski rods.



Please note that MDF contains formaldehyde which becomes airborne when you're working with it, especially with power tools.


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## pedromdf (May 12, 2011)

Hi Allthunbs

I have a DeWalt 620 router and I see the fig. 20 - Pivot frame, at "router-organized.pdf".
I think that's the way to find a solution. Is close to a manual CNC. lol
Ok I'll send you a PM and thanks for yout attention.
Pedro


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## pedromdf (May 12, 2011)

Hi, Allthunbs
I'm sorry but I have no enogh messages to authorize a PM to you.
I've seen your "router- organized.pdf" and I find the pivot frame very interesting. I have a DeWalt 620 router for that solution.
Thanks for your attention.
Pedro


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## pedromdf (May 12, 2011)

I think the circular jig for my DeWalt router is something like this


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## bobj3 (Jan 17, 2006)

Hi Pedro

That's a great drawing , how about a real photo shot of the jig ?
I would love to see your jig 

YouTube - Trend Pivot Frame Jig

http://www.amazon.com/Trend-PFJ-SET...ref=sr_1_7?s=hi&ie=UTF8&qid=1305554736&sr=1-7
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pedromdf said:


> I think the circular jig for my DeWalt router is something like this


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## allthunbs (Jun 22, 2008)

pedromdf said:


> I think the circular jig for my DeWalt router is something like this


Hi Pedro:

That would work nicely too. Your problem will be centring your jig. With this jig, your holes will be clean and accurate.


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## pedromdf (May 12, 2011)

bobj3 said:


> Hi Pedro
> 
> That's a great drawing , how about a real photo shot of the jig ?
> I would love to see your jig
> ...


Hi Bobj3

The problem is that "my jig" is only a 3D drawing yet!

I hope the real photo is available as soon as possible.

Thanks for your interest.

Pedro


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## bobj3 (Jan 17, 2006)

Thanks Pedro


Thanks for the feed back , I keep looking at your drawing and it is out of wack for the mounting of the router and rods, that's what got me going..and very limited in the way it can be used, but that's just my 2 cents.. 


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pedromdf said:


> Hi Bobj3
> 
> The problem is that "my jig" is only a 3D drawing yet!
> 
> ...


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## pedromdf (May 12, 2011)

allthunbs said:


> Hi Pedro:
> 
> That would work nicely too. Your problem will be centring your jig. With this jig, your holes will be clean and accurate.


This is the great question, and I thought to make an auxiliary acrylic piece with the center position.


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## pedromdf (May 12, 2011)

bobj3 said:


> Thanks Pedro
> 
> 
> Thanks for the feed back , I keep looking at your drawing and it is out of wack for the mounting of the router and rods, that's what got me going..and very limited in the way it can be used, but that's just my 2 cents..
> ...


I'm open to any better idea. This is inspired on Trend pivot frame and certainly can be better. Please fell free to another 2 cents.

PS: "out of a wack" means what? I think it's "o cabo dos trabalhos" in portuguese.


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## pedromdf (May 12, 2011)

Hi Bobj3

Pardon me, but only now I see the jig attached to you message.

It's all there.

Pedro


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## bobj3 (Jan 17, 2006)

Hi Pedro

We have a member that made a jig like your drawing, well almost he is in France ,he has posted a PDF file how to make one I'm not a big fan of his, I think the Trend can do so much more..
I will try and find his post for you..

add on
http://www.routerforums.com/235398-post16.html

See his uploads for more shots of it and a PDF file..on this web site.
more on his web site ▼
http://www.lescopeaux.asso.fr/
======


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## bobj3 (Jan 17, 2006)

HI Pedro

" "out of a wack" means what? " = it's like installing a VW engine upside down,looks good but it just will not run that way = out of wack..


====



pedromdf said:


> I'm open to any better idea. This is inspired on Trend pivot frame and certainly can be better. Please fell free to another 2 cents.
> 
> PS: "out of a wack" means what? I think it's "o cabo dos trabalhos" in portuguese.


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## RJM (Apr 11, 2010)

Is a router even the right tool for this?

1. Make a cylindrical insert on a lathe. Glue up some MDF, then turn it. Glue it into a hole in the speaker panel. This is probably the easiest way. Will take some skill to get the pattern you want manual gouging. A patten follower, or cnc lathe would make it easy.

2. Use your plastic cone as a mold and make a cylindrical insert using "Durham's Rock Hard Water Putty". Then glue it into a big hole in the MDF.

3. Use the step drilled method previously posted and clean up with a chisel and a custom scraper. Make a scraper from O2 steel yourself, or have a machine shop cut out the 2D profile. Attach it to a shaft and chuck into a drill press.

4. Have a custom drill bit made with the profile shown. I don't know if this is possible but it's probably expensive.

5. Get a CNC router.


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## pedromdf (May 12, 2011)

RJM60 said:


> Is a router even the right tool for this?
> 
> 1. Make a cylindrical insert on a lathe. Glue up some MDF, then turn it. Glue it into a hole in the speaker panel. This is probably the easiest way. Will take some skill to get the pattern you want manual gouging. A patten follower, or cnc lathe would make it easy.
> 
> ...


The front panel has 1360x450x40mm. I want to make the horn based on a tractrix curve directly on the front panel. In the past I screwed a plastic horn on the front panel, but this time I want to make it a different way.

The way to make this is your point 3, I think. The question is, how many steps to obtain the exact curve. The scraper is a good idea. And I'm gonna see if the "Durham's Rock Hard Water Putty" is good to make a mold with sandpaper to smooth all the surface.

Finally, it could be achived with several technic steps.


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## pedromdf (May 12, 2011)

bobj3 said:


> HI Pedro
> 
> " "out of a wack" means what? " = it's like installing a VW engine upside down,looks good but it just will not run that way = out of wack..
> 
> ...


Hi Bobj3

Thanks for the good explanation.


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## pedromdf (May 12, 2011)

From what I have read I think this are the jigs more popular.

Now I am finding the right sizes and dimensions to begin do it.

Thanks in advance for any help.

Pedro


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## bobj3 (Jan 17, 2006)

Hi Pedro

Thanks for the pictures, I have many cir.jigs but I'm going to make one like the one on the Trend router.  I love jigs and you can't have to many. 


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pedromdf said:


> From what I have read I think this are the jigs more popular.
> 
> Now I am finding the right sizes and dimensions to begin do it.
> 
> ...


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## pedromdf (May 12, 2011)

bobj3 said:


> Hi Pedro
> 
> Thanks for the pictures, I have many cir.jigs but I'm going to make one like the one on the Trend router.  I love jigs and you can't have to many.
> 
> ...


Can you give me some of your jigs plans? :no:


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## allthunbs (Jun 22, 2008)

Hi Robert:



RJM60 said:


> Is a router even the right tool for this?
> 
> 1. Make a cylindrical insert on a lathe. Glue up some MDF, then turn it. Glue it into a hole in the speaker panel. This is probably the easiest way. Will take some skill to get the pattern you want manual gouging. A patten follower, or cnc lathe would make it easy.


A lathe is an excellent base for a router. Mounting is a bit of a problem but a router mounted horizontally on a sled is perfect for lathes. If you take a look at a Legacy and other "ornamental wood mills" you'll find that's their normal setup.



> 2. Use your plastic cone as a mold and make a cylindrical insert using "Durham's Rock Hard Water Putty". Then glue it into a big hole in the MDF.


Neat suggestion. I'll add that one to the reference digest.



> 3. Use the step drilled method previously posted and clean up with a chisel and a custom scraper. Make a scraper from O2 steel yourself, or have a machine shop cut out the 2D profile. Attach it to a shaft and chuck into a drill press.


Alternatively, scraper's aren't difficult to make from scrap hardened steel. My father sharpened old fine files and used them for chisels. Thin spring steel can be used as well. But, all my scrapers are flexible. 



> 5. Get a CNC router.


The CNC doesn't have enough travel through the "Z" axis. Remember, we're dealing with 75mm. That's almost 3." There are few "small" CNC that will do that kind of thickness. 

You also have to remember that this member is in Portugal and availability of such machinery is less evident than in the US and Canada. You also have to remember that the prices of these machines goes up dramatically the farther away you get from the US.


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## pedromdf (May 12, 2011)

Allthunbs

Thanks for the clarifications.

Today I'm gonna try to make this two scrapers.

I'm thinking to make some steps with circle cutting and after make some passages in slow speed with this two scrapers.


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## allthunbs (Jun 22, 2008)

pedromdf said:


> Allthunbs
> 
> Thanks for the clarifications.
> 
> ...


Whoa Pedro!

Are you an engineer? Do you understand balance and torque and centrifugal and centripetal forces? Making a scraper is one thing. Making a router bit to turn at 8000-10000 rpm is another matter completely. Make sure you protect yourself. Your drawings look to be very dangerous.


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## RJM (Apr 11, 2010)

I agree with allthumbs.

What I had in mind was a single piece blade with a rod (or split rod) attached somehow. The welds shown in the picture are a failure point.

Also, I might try using this in a slow turning drill press but not a router.


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## pedromdf (May 12, 2011)

This weekend I've made the circle cutter, a very simple version adapted to this work only.

A few minutes ago I made the first three passages with a round nose router cutter.

I'm very happy with the results. Sorry I have no photos.

The idea for the scraper I showed is not to use with the router, is only to smooth the surface after the round nose router cutter.

I thought to use it in a column at minimum rotation.


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## allthunbs (Jun 22, 2008)

RJM60 said:


> What I had in mind was a single piece blade with a rod (or split rod) attached somehow. The welds shown in the picture are a failure point.
> 
> Also, I might try using this in a slow turning drill press but not a router.


Thanks for clarifying that Robert. I couldn't assume that was what you meant and I couldn't let it pass. However, your clarification takes this into a whole new category. If Pedro has a drill press and can control the speed slow enough that just might be the ticket.


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## OPG3 (Jan 9, 2011)

Possibly this will not work, as I have never dealt with sound equipment, but can you make a through hole the larger diameter, flip it over and infill with some kind of filler, putty, etc. If you don't want the filler material to bond to the applicance, just make a "negative" from modeling clay, line the "negative" with a bond breaker, then make a "fake positive" (matching the appliance) to place a debonded filler material. I hope this makes sense and helps you. *OPG3*


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## pedromdf (May 12, 2011)

The final aspect after all the passages with the round nose router cutter, is near like this in the atachment, I hope.

One or two passages with the scrapers (I don't know if is realy necessary), and many sandpaper and body putty work, to have a very smooth surface and finaly a glossy piano black finish. I'm dreaming ...


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## pedromdf (May 12, 2011)

Thanks Allthunbs, when I said "I thought to use it in a column at minimum rotation.", column is a direct translation for press drill as you said.


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## bobj3 (Jan 17, 2006)

Hi Pedro

That looks great and will look great in wood I still say the Trend cir.jig is the tool for that job..

http://www.youtube.com/watch?v=18CUKZo2JUE
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pedromdf said:


> The final aspect after all the passages with the round nose router cutter, is near like this in the atachment, I hope.
> 
> One or two passages with the scrapers (I don't know if is realy necessary), and many sandpaper and body putty work, to have a very smooth surface and finaly a glossy piano black finish. I'm dreaming ...


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## allthunbs (Jun 22, 2008)

pedromdf said:


> Thanks Allthunbs, when I said "I thought to use it in a column at minimum rotation.", column is a direct translation for press drill as you said.


Hi Pedro:

Glad we could help. Keep us posted on your progress. We're all learning from your experiments so details will help us all.


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## pedromdf (May 12, 2011)

Today I have some time to do a little more and now the tractrix is something like this.

Now I need a longer round nose router cutter.

Please tell me what is the safety minimum to fix the router cutter?


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## bobj3 (Jan 17, 2006)

MLCS Router Collet Extension and Review

http://www.mlcswoodworking.com/orderstatus/html/smarthtml/pages/bt_core.html
#6418
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pedromdf said:


> Today I have some time to do a little more and now the tractrix is something like this.
> 
> Now I need a longer round nose router cutter.
> 
> Please tell me what is the safety minimum to fix the router cutter?


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## allthunbs (Jun 22, 2008)

pedromdf said:


> Today I have some time to do a little more and now the tractrix is something like this.
> 
> Now I need a longer round nose router cutter.
> 
> Please tell me what is the safety minimum to fix the router cutter?


Hi Pedro:

I have not found a minimum statement anywhere. All of the information I can find says that the bit needs to be almost bottomed out in the the collet. (There's whole threads on this discussion on the forum.) 

Extensions are a possibility but I'm loathe to use them. That's a lot of side load. I prefer instead to maximize the protrusion of the collet through the base of the router. In your situation, an extension may be the only way to go if laminating proves inadequate.

Work safely. Don't take chances.


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## pedromdf (May 12, 2011)

Hi Bobj3

Thanks for the information. Never heard about extensions , allways learning.

I think its better to buy a longer bit.

Hi Allthunbs

I think you're right. I hope I can find a longer bit here.

Regards
Pedro


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## bobj3 (Jan 17, 2006)

HI Pedro

It's true a longer bit would be best BUT that's why they make and sale the extensions, they are safe to use..and MLCS can ship them to you..

Maybe Phil (UK )will jump and give you a link to one on your side of the pond. 

=======



pedromdf said:


> Hi Bobj3
> 
> Thanks for the information. Never heard about extensions , allways learning.
> 
> ...


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## pedromdf (May 12, 2011)

Here is the first part of the horn for the tweeter of the central loudpeaker of my future home cinema system.


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## allthunbs (Jun 22, 2008)

pedromdf said:


> Here is the first part of the horn for the tweeter of the central loudpeaker of my future home cinema system.


Nicely done. Now, how did you do it? What worked and, more important, what didn't? Any comments or suggestions for someone else wanting to do the same thing in the future or something similar???


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## pedromdf (May 12, 2011)

Hi Allthunbs

Firstly I did an AutoCad scheme with the number of cuts I need with a round nose cutter tangent to the form curve I want to make, as I showed earlier.

With this I have a chart of diameter/deep cut.

With diameter data I've made a simple circle cutting jig that consists on a wooden base for my router with 3mm holes for each radius.

After this is critical the exact deep control and a lot of patience. I think there are 2 passages that are too deep (as you could see in the photo).

The last cut is critical, you have to leave some material not to lose the center rotation of your jig. I have failled.

Now I have to make the last section of the horn in another block of MDF, with same enthusiasm.


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## pedromdf (May 12, 2011)

Now I'm thinking about a solution to a precision circle cutting jig for little diameters, between 11,5 and 25mm radius.

Any idea?


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## allthunbs (Jun 22, 2008)

pedromdf said:


> Now I'm thinking about a solution to a precision circle cutting jig for little diameters, between 11,5 and 25mm radius.
> 
> Any idea?


Yup, Santé's circle cutter. Bang on for small diameters, and precise too.


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## allthunbs (Jun 22, 2008)

pedromdf said:


> Hi Allthunbs
> 
> Firstly I did an AutoCad scheme with the number of cuts I need with a round nose cutter tangent to the form curve I want to make, as I showed earlier.
> 
> ...


I like the way you're doing this. How did you manage to get the gaps though (way above). I can't figure that one out.


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## bobj3 (Jan 17, 2006)

Hi Ron

Do you have one of the " Santé's circle cutter " ???? how about a snapshot of yours..

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allthunbs said:


> Yup, Santé's circle cutter. Bang on for small diameters, and precise too.


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## pedromdf (May 12, 2011)

The Santé's circle cutter is very interesting, but have a problem, the first 22/23mm of the router bit are absorbed by jig thickness.

I'm thinking about a n-compass based solution, made with a 3mm steel plate.


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## allthunbs (Jun 22, 2008)

pedromdf said:


> The Santé's circle cutter is very interesting, but have a problem, the first 22/23mm of the router bit are absorbed by jig thickness.
> 
> I'm thinking about a n-compass based solution, made with a 3mm steel plate.


Hi Pedro:

I don't understand the n-compass based solution. 

You could redesign Santé design and eliminate the 23mm thickness problem. Given that your tractrix are all consistent in size, why not use the initial cut for the tractrix as your jig for the remainder of the thickness of the cut? Does that make sense???


Ron


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## pedromdf (May 12, 2011)

Hi Allthunbs
The n-compass is like the attach photo.

As I said I've made a circle cutting jig very primitive, a little difficult to use because the center is under the router. The circle cutting jig is only a wooden baseplate with a hole center for each radius.

In the present situation the difference between each radius are very little and the 3mm center holes are very near, so the risk of mistake is great.


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## Phil P (Jul 25, 2010)

bobj3 said:


> It's true a longer bit would be best BUT that's why they make and sale the extensions, they are safe to use..and MLCS can ship them to you..
> 
> Maybe Phil (UK )will jump and give you a link to one on your side of the pond.


Sorry, Bob, but I missed that one :lazy:. The best quality collet extender I know of over here is made by Axminster Power Tool. It utilises a high quality ER20 collets which cover the range 2 to 13mm; much better than other extenders such as the CMT. As ER20s are standard engineering collets they are available from many, many sources. Axminster will ship to anywhere in the EU and because they manufacture these in-house they may possibly make a special longer one if requested



pedromdf said:


> The n-compass is like the attach photo.


The NCompass is OK, I suppose, but they do need a 1/4in (not 6mm) diameter hole to be drilled in the dead centre of the work piece to take the pivot pin. Can you accommodate that? I've used the Trend jig to do circular cut-outs in 44mm thick veneered doors to convert them into porthole doors and they work fine for that - or rather they were used with an 8mm plunge router (Elu MOF96) to rout a groove at the outside of the circle, the jig and small router were removed and the rest of the cutting performed using a 1/2in plunge router with a large diameter template trim bit fitted. The NCompass base (which the router sits on) is rather thin acrylic and needs to be supported over much of its length. It also flexes if you try taking too heavy a cut, so shallow and many passes is the approach. It is limited to 1/4in or 8mm routers such as the small routers by Bosch, deWalt, Elu, Festool, etc because the rods are 8mm diameter and they won't go wide enough to take a 1/2in deWalt router for example. And in any case to use a collet extender you'll need to have a 1/2in router......

I'm of the opinion that you may need to take a completely different tack on this one. Were I doing this job I'd consider building a static gantry to support the router above the workbench. Beneath the gantry I'd then arrange the timber to sit on top of a revolving table such as a Lazy Susan, and for that revolving table to sit on top of a table which runs on tracks such as a pair of drawer slides so that it slides right to left beneath the gantry. By utilising this system it should be possible to set up each cut, rotate the workpiece, move in (or out) then adjust the depth of cut and take the next cut until all the required cuts are made. This is a similar approach to that which a pattern maker might have taken on a recessor or overhead pin router in the days before CNC routers. If you are having difficulty envisioning this I'll try to knock up something in Sketch-Up if needs be

Regards

Phil


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## allthunbs (Jun 22, 2008)

Hi Phil:

What you're describing is a set of skis with a turntable beneath it. That just might work.


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## pedromdf (May 12, 2011)

Hi Phil

Thanks for your help. If you don't mind, please I need your Sketch-Up.

Regards
Pedro


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## allthunbs (Jun 22, 2008)

pedromdf said:


> Hi Phil
> 
> Thanks for your help. If you don't mind, please I need your Sketch-Up.
> 
> ...


Hi Pedro:

Do a search on this forum for "skis" and you'll come up with a large selection of information on skis. Now, if you can't see the forest for the trees, drop me a line and I'll send you a copy of my notes.


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## bobj3 (Jan 17, 2006)

Hi Pedro

Using the key word skis you will not find to many but if you check out HarrySin uploads you will find many of them..

http://www.routerforums.com/members/harrysin-10844.html

i.e below
http://www.routerforums.com/jigs-fixtures/25155-wanted-pictures-your-skiis.html
=======


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## pedromdf (May 12, 2011)

The big difference between my two situations, is that now I can rotate the piece of MDF.


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## allthunbs (Jun 22, 2008)

bobj3 said:


> Hi Pedro
> 
> Using the key word skis you will not find to many but if you check out HarrySin uploads you will find many of them..
> 
> ...


One of the better ones is this one started by a member and well contributed to:

http://www.routerforums.com/portable-routing/24435-newly-created-router-skis.html#post208291


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## pedromdf (May 12, 2011)

I've made this scraper.

Now the surface is very uniform and smooth.


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## allthunbs (Jun 22, 2008)

pedromdf said:


> I've made this scraper.
> 
> Now the surface is very uniform and smooth.


are you using a turntable?

do you have a picture of your setup, turntable and scraper mounting?


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## pedromdf (May 12, 2011)

In this case, as the shape of the horn is very near the final form, I've used the scraper manually. MDF is easy to work.

In future applications I will adapt this scraper to a drill press at low speed to smooth the surface after the router passages.


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## allthunbs (Jun 22, 2008)

pedromdf said:


> In this case, as the shape of the horn is very near the final form, I've used the scraper manually. MDF is easy to work.
> 
> In future applications I will adapt this scraper to a drill press at low speed to smooth the surface after the router passages.


Thanks. That makes the picture clearer. It will be interesting to see how you "balance" the shaft on the centre of the scraper when you convert it to drill press use.


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## pedromdf (May 12, 2011)

I'm gonna be at Tampa, FL, next month for work.
Can you tell me about some woodworking tools shops?


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