My New Router

[special bone]

8-[
Words fail me. Building your own CNC router was impressive. Being able to carry your boyweight was astounding. But cutting teardrop shaped dovetails?!?!?!?!?!? That's just not fair.

Rich

P.S. I'm trying to handcut dovetails for a toolbox at evening classes. It's not going swimmingly .

P.P.S. I am in total awe of what you've achieved. [-o<

 

[Fecn]

I was in a rush to get the pics up before dinner in my last post. Thanks to everyone for their continued encouragement. This project's been a real crowd pleaser, and it's fantastic to receive all this praise. My head is starting to swell.

I have used my best video editing skills (you can tell I don't work in TV) and pieced together the following 20MB 7 minute video clip of cutting the tails and pins. I'm going to have to start using youtube soon if I keep knocking out these videos. I was trying to mix the normal router-noise soundtrack with the music, but lost the noise somewhere along the way - The music starts abruptly a few seconds in.

After I'd spent a couple of hours doing test cuts until I was confident with the positioning of the workpieces on the machine and the alignment with the tool, cutting the tails took just under 13 minutes per end, and doing the pins takes just under 17. Making the box itself took a total I used 2 hours of machine time. Whilst the machine was cutting one set of pins/tails, I was cleaning up the previous set using a stanley knife blade and 100grit sanding block.

Watching through the video illustrates two mistakes which I shall try not to make again..
1. High Speed Steel tooling (like that cheap little router bit) wears out very quickly when cutting Ipé - I ordered some carbide bits yesterday, but they won't be here for a couple of days. - I reckon the bluntning of the tool is partially responsible for the mis-shaping on the tails. You can see how much more blunt it's become by the time it's onto the pins - there's loads of smoke when it does a plunge cut.

2. You should rout edges (e.g. pins) in a counter-clockwise direction, but you should rout holes/pockets in a clockwise direction - I knew this all along, but haven't worked out how to tell the software yet - I reckon that's the other factor for the mis-shaping of the tails.. Those two.. and the push-fit tool holder.

 

[Gill]

This thread is fascinating - much better than watching Norm!

=D>

Gill

 

[Woodmagnet]

Cor Blimey! :wink:

 

[wizer]

Right, That's it... Jim, where do I send my cheque? I'll take one

 

[devonwoody]

Quote from fecn above

I've no idea what to do for the bottom of the box or the top - I really hadn't thought any further than this. Ideas on a postcard to me please

Because your dovetails are not half blind type, I think the base just needs a ply bottom that sinks inside the carcass and stringers to hold it in place, I quite often let the stringers hand below carcass level and they form a secret support for the box to rest on.

The lid could remain quite plain so it doesn't detract from the carcass joints which are very novel in their appearance.

Keep up the good work :wink:

 

[dedee]

Rather than use your machine to cut a straight grooves for a drawer bottom perhaps you could make it curved instead? I am sure you would have no problems getting the curves on opposite sides to be aligned?

Keep up the good work

Andy

 

[Fecn]

Right, That's it... Jim, where do I send my cheque? I'll take one

Where to send it.. That's the easy part.. What to write on it is the tricky bit. - I like the idea of using the CNC machine to make a copy of itself (only better), but working out all the details in the software would undoubtedly take far longer than knocking up another one by hand using the table saw. I reckon I could make all but 3 bits (the bits for the base) on the machine and do a flat-pack version.

Because your dovetails are not half blind type, I think the base just needs a ply bottom that sinks inside the carcass and stringers to hold it in place, I quite often let the stringers hand below carcass level and they form a secret support for the box to rest on.

The lid could remain quite plain so it doesn't detract from the carcass joints which are very novel in their appearance.

The only ply I have is either 6mm or 18mm WBP which came from Jewsons - At either thickness, it's not pretty to look at. I could do with some nice high quality 3mm birch ply (or something similar) for the bottom. I've got some bits of Ipé and Cedar which are thicknessed down to 12mm currently.. I was thinking of taking them down to 6mm, and having a centre strip of Cedar with Ipé strips on either side.... I reckon that would look OK for the base... Only problem with Ipé is that it doesn't take glue well. - I try some experiments and see how it looks.

My current thinking is 6mm Ipé for the top in two pieces. I could make a rebate in the top to allow the lid to sit flush, and then cut a lowered section into the rebate so that if you press the lid in the centre, the two leaves fold upwards at the outside..

Hopefully this ascii-art will illustrate what I mean.

Closed - Lid rests in rebate.
 _____ _____
|---\__/----|

Push in middle - Middle pushes down into lowered section and lid opens up from outside.       
   \    /
|---\\//----|

Rather than use your machine to cut a straight grooves for a drawer bottom perhaps you could make it curved instead? I am sure you would have no problems getting the curves on opposite sides to be aligned?

I think I see what you're getting at there and reckon that I can handle the software well enough now to manage it. That idea (if I've got your gist) could possibly work for the lid/top I'm thinking of, which needn't be square since the rebate doesn't have to be straight.

 

[devonwoody]

Lid looks very technical, reminds me of crab pots! only joking, looking forward to the day it arrives.

 

[Lukey]

Re the teardrop dovetails. They do look good.

BUT! Because they are so unusual, having the two different sizes makes it look completely random...

Do you think it may be an idea to keep all the sizes uniform (in future, obv.)? I think it would look neater, and the impact of that contrasting wood would work much better IMO.

 

[Fecn]

BUT! Because they are so unusual, having the two different sizes makes it look completely random...

Do you think it may be an idea to keep all the sizes uniform (in future, obv.)? I think it would look neater, and the impact of that contrasting wood would work much better IMO.

Yep.. I see your point. I think that fewer, larger pins/tails might look better. It's hard to visualise how things are going to end up looking when you're designing it in B&W on a computer screen. I have another idea for a joint that I'd like to try, but I'll keep the details on that secret until I find out if it'll work or not.

In other news...

I won 40 second-hand 1/4" shank slot-drills & end mills from ebay for £32. For safety reasons I don't have an ebay account, so I got a friend to bid for me and just popped round to his place this morning to pick them up.

A coulple of the bits seem to be brand-new and still had the protective wax on them, so I reckon I got a good deal even of the rest are useless. A friend of mine tells me that end mills can't be used for plunge cuts, but I'm wondering if I can sharpen the tips so they can. I'm hoping that the screw threads won't get in the way with the collet in my router.

Does anyone have any safety warnings for me before I try some of these in a router? - Maybe I should post that question to the general woodworking topic.

 

[Fecn]

Only managed to get a couple of hours in the shed today (so far).

First off, I attempted to work out why the tails I cut yesterday weren't up to scratch. I started off by cleaning up the cutter I'd been using and attempting to sharpen it again (don't know how successful the sharpening was).

Next, I moved onto improving the Proxxon the tool holder. There was a lot more wiggle than I like, so I came up with this solution using a spare lump of MDF and an old bag strap.

I cut another set of tails for a test, and this time they're much better. I did try to take some pics to show the change, but my mobile phone camera couldn't get things in focus properly today in spite of me taking 5 pics. I nearly broke out my good camera, but looking at the pic I posted to the thread on Friday, you can't really see that there was anything wrong in the first place. Anyway.. I was rather happy with the box on Friday, but I'm far happier with the results I'm getting now.

 

[Lukey]

What do you mean for safety reasons you dont have an ebay account - the danger of spending too much? :lol:

 

[Fecn]

What do you mean for safety reasons you dont have an ebay account - the danger of spending too much? :lol:

Yep.. and on things that I find myself wanting, without any reason why - I drink beer and I browse the web... I have plastic and I think Mini Diggers are rather cool. No ebay account is a great safeguard.

On with the show...
A freind of mine came to visit over the last couple of days, and we spent our time messing around with the CNC machine and software - We spent rather a lot of time wokring out the mysteries of cutting half-blind dovetails. Thanks again to waterhead37 for the scans of the jig.

After one very late evening, we finally cracked it (we think), and I should now be able to cut dovetails at any depth and any tightness. The cutting path we feed to the machine tells it where to put the centre of the cutter, so we have to offset that path by the radius of the cutter to get the edges in the right place. For the pins the offset is equal to radius of the base of the cutter, but for the tails it depends on the cut depth, so we had to calculate it using trig.

Here's the the exciting bit first...
3 minute video clip (10MB) of cutting pins and tails on the machine.

And here's the science bit for anyone who wants extra credit. These are the pictures we drew to help us work it all out.

We design the dovetail based on the width of the thick ends of the tails - Here we have a 20mm, 30mm, 20mm arrangement.

We know our cutter has a 104 degree angle, so we can work the rest out with some very easy trig.

I can see I'm going to have to plan some new projects.. but i must finish off dw's box first.

 

[motownmartin]

Excellent stuff fecn, it really is looking the bees knees, I know that you will place in some backing boards to prevent splintering, can I also suggest that when cutting the tails you first run a small cut or a scoreline on the ends of your boards, this will prevent the corners of the boards splitting.
This really is a fantastic bit of work and i'm looking forward to the finished box for John.

 

[devonwoody]

I'm getting excited!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

(John)

 

[herdsman]

Top stuff Fecn, I did have reservations about the feed screws for moving the carriages but that does not seem to bee a problem. Are you still using the Mach 2 software?

Keep it coming, a very intersting project.

 

[Chris Knight]

Super work Fecn - look forward to seeing the results!

 

[catface]

hello, you bought a load of mills & were asking about plunge cutting :

It used to be the case that there were two similar looking products & these were called slot drills and end mills.
Some can plunge cut and some cannot plunge cut.

End mills are so called as their primary cutting is done on their ends. (They may also have two, three, four or more cutting flutes and be right handed or left handed ie. right handed cutter cuts when rotated anti clockwise & vice- versa).

Two flute end mills can be used for centre cutting(plunge cutting), since the tooth grind extends to the very centre of the bit (like on a conventional twist drill bit you use in your black and decker).

Most four flute end mills will also plunge cut, as the flutes are ground to the centre of the bit. However, some four flute bits will not plunge cut as they have a small space (hole) or flat circle at the centre of the tip. This is called "gashed". A gashed end mill will not start its own hole & must start its cut with the side of its body, ie. start it off the workpiece or drill a starter hole first to put it into.

To summarise, plunge cutting depends on having a tooth which extends to the centre of the point of the cutter ; two flute mills are ususally ground to do this. Other eg 3, 4 flute mills, you have to look to see if its "gashed" & needs a starter hole or off-workpiece start.

Hope I haven't bored you stiff ! regards, Catface.

 

[Fecn]

Top stuff Fecn, I did have reservations about the feed screws for moving the carriages but that does not seem to bee a problem. Are you still using the Mach 2 software?

The feed screws seem to work OK... I do worry about them getting gummed up with sawdust, but so far that hasn't been a problem. I was using Mach2 until last week, but I've since shelled out for copies of Mach3 and LazyCam because I wanted the tool diameter compensation and pocket cutting functions to work properly. I also downloaded trial versions of the Vectric Cut3D software, but haven't had the chance to try it out yet - The Vectric stuff looks quite nice.

Hope I haven't bored you stiff ! regards, Catface.

Not in the slightest - in fact.. I want you to go on speaking

I seem to have got about 60% slot drills and 40% end mills which is a good mix. I imagine all these bits were designed for use at a the farily low spindle speeds found on milling machines around 2000RPM. The slowest my router can go is 8000RPM. I don't imagine the bits will mind the increased speed since they're all very small diameter.

Do bits like this have a maximum speed rating?
I imagine the upcut spirals will have a tendency to try and lift the workpiece from the table - I reckon I need to improve my clamping a bit before I try them in anger.