Dovetailing with Gary C's system and collet wear

[jTr]

I've been enjoying cutting dovetails with Gary's system for years now. One of my favorite routines to run on the shopbot, and always have great results. Minor cosmetic nit to pick: I do use 5/8 stock, and always found the depth of cut a bit shallow at about 5/16". Finally tried a Freud 22-122 bit today. It is an 8* vs 14* pitch, and I thought this gentler taper would allow a deeper cut = larger more proportionate set of tails.

One image shows the results- it actually will do a through dovetail, which has me thrilled. In fact, what you're looking at was cut at .620 into .625 stock, resulting in a veneer - thin layer. Awesome!

However, concerned about collet wear, as you can see marks on the shank of the bit. This was first use of this new bit. Granted, I've ordered some 1/2" shank replacements to reduce chatter, but noted that my original 22-112's with 1/2" shanks also develop these burnish marks.

Ultimately just trying to determine if this is:
- Normal, due to additional stresses on bit with this type of cut?
- Pushing collet life too far?

Either way, I'm very grateful for the ability to dovetail with this level of quality on the cnc. 2976429765

Jeff

[Ken Sully]

Trying to find the link, or post for Gary C's dovetail procedure. Can't seem to find it.
Anybody know where to find it?

[bob_s]

Ken

take a look here, way back in the archives
http://www.shopbottools.com/LabFiles/GaryDovetail.htm

Bob

[Keith Larrett]

What feed rates do you use when cutting with the dovetail bit? Do you make a clearance pass with a straight bit first? I have experimented a bit with cutting dovetails on the CNC with mixed success. I broke a couple of dovetail bits. I suspect they broke for a couple reasons, 8mm shank (Leigh bits), no clearance pass and my feed rate was probably to fast.

The experimentation was getting expensive so I set it aside for a while :)

Appreciate any advice you can offer.

[Ken Sully]

Thanks Bob
Couldn't find that for the life of me!

[jTr]

Keith,
The original file is set to run 1ips. I've tried 1.5 and 2, and simply settled on 1.5 as it seems the sweet spot for cleanliness and speed. Can quickly be modified in the file if wood species allows. I've yet to break a bit using this system. A little tear out from time to time, but nothing fatal, as the worst occurrences usually show up on what will be the underside of the drawer.

The original file also is programmed to run a climb cut on the inside of the drawer front, so that part is always pristine. Note that this is done with the dovetail bit, so once you've chucked and calibrated your bit, you can just keep punching out drawer parts, no tool changes.

Another time saver: I calibrate for my deepest drawer parts (9") first, then run all smaller sizes with this setup. If you stop to change width of stock, you will need to run tests and tweak the fit for each size. The bulk of time is with the bigger drawers, so I just run the same routine for the smaller sizes. The machine simply air cuts as if 9" parts were there, but this often results in time savings vs. resetting for each drawer part width. Typically, I can set up, test and produce a kitchen worth of drawers in a morning, ready to assemble.

Another interesting point- dovetailing requires a bit of time and tedium in marking parts to make sure pairs are kept together. This system also recommends it, but I've found precision reliable enough that I've ceased marking parts a couple years ago. Once things are dialed in, it all just works. Just be certain your parts are milled with high accuracy and above all, uniformity of dimensions.

As intended when posting about this, I'm trying to point out that once you're comfortable, you may experiment with other bit geometry for different results. I've even produced finger joints with minor adjustments of variables in the part file, as it was written to allow this type of versatility. Try it. You'll like it. Only thing better I can imagine is a dedicated machine for dovetailing, only because it saves set-up time.

Best to simply refer back to the original article, as Bob posted above to get rolling.

jeff

[jTr]

I made a very large version of the jig - it is 34" between fences. This allows you to do some case construction . Due to extended width, it is helpful to put the extra bolts in the center to control wider drawer stock. They can be removed for larger case sized parts. Only other limitation of stock size is the case part hanging off the end of the table, which would be the pins, or as I've labeled it, drawer sides. It is limited in length by height of your cnc table from the floor, which in my case is about 32".


My favorite grip-assist material for the clamp bars is 3M adhesive tread as shown. You can buy by the foot at most local hardware stores. No mar,(like sandpaper style) and it doesn't transfer any oils like some rubber based products I've used.

jeff

[Gary Campbell]

Guys....
I am so happy that these files are still being used almost a decade later. Kudos to those that keep this going long after I forgot what I did to make them!!

[Keith Larrett]

Jeff

Thanks for the reply. I'll check out the article Bob posted. I appreciate the comments on the feed rates as well. When I have some spare time I will experiment with it again.

Regards

Keith