Dovetail cutting?

[Lakc]

I am at the point where I am making tools to make more tools to finally make parts. One set of these tools requires dovetails, and while I find a wealth of information on measuring them, I have found very little info on actually cutting them.
Just what is the best way to avoid explosive dovetail cutter syndrome? ;D
Do you cut the majority in one pass with a fast tool and slow feed? Do you take the average of cutter diameter and apply a standard speed and feed equation?
I have managed to cut several so far but am not sure I am doing it the best way. Using a 1-3/8" 60 degree hss cutter and taking about .020 max with about 300 rpm spindle speed and just enough feed to take a bit of chip and hopefully not dull the tool, cutting cold roolled mild steel. It seems to have worked so far without undue cutter wear, but is certainly taking a lot of passes to get the job done. The scary part is the internal cutting where the first pass has to cut a little on both sides.
Thanks,
Jeff

 

[kf2qd]

Mostly depends on your machine. First you use a straight end mill and cut most of the extra material away. then you start cutting out the dovetail area. depth of cut there depends on ho big the cutter is and how solid your machine is. Earlier cuts can use more depth of cut than later ones because of the amount of contact between the cutter and the workpiece.

But the biggie is - how confident are you? iIf you are comfortable with the process then it is probably working well.

 

[JohnLanark]

Why not buy another tool.... a shaper. They are very interesting and fun to use, but unloved and can be bought for peanuts. Ideal for dovetails. John.

 

[Deanofid]

If you're worried about the cutter taking a cut on both sides of the dovetails at once, you could start with a smaller dovetail cutter with the same angle, or take the edge off the start of the corners with a t-slot cutter. That assumes you have either of those two tools.
It sounds like you are going at it okay, though. Watch your feed speed and clean the chips out often. It's not a fast process, especially if you are using a small machine.

Dean

 

[Krown Kustoms]

Sounds good, if you could post some pics it would really help, I have never cut a dovetail and I want to make a QCTP.
I have put it off several times due to the lack of knowlege.
thanks -B-

 

[Lakc]

Actually, I am using my Millport/Bridgeport, but in this case, that seems to just make it easier to break the tool.
I tried a 3/4" 45 degree cutter at first, but it died midway on the second pass, I guess .050" was too much for the Enco $12 special. I wound up with the current cutter because thats the only one production tool had in stock, and went to 60 degree because the cutter looks like it should be stronger. Inexpensive, and dovetail cutters, do not seem to go hand in hand, so I am leery of pushing this one too hard. Still, I am trying to push it hard enough that every tooth takes a bite, but its slow going.
I'll try and get some pics of it tonight.

 

[Deanofid]

Krown, I have a bit about dovetail cutting on my web pages. Click the link below my name, and then go to the boring head project. Might be something there you can use.

Dean

 

[steamer]

Take most of the stock out with an end mill and only cut what you need with the dovetail cutter...it saves the cutter

Work to roll dimensions.



Dave

 

[craynerd]

I am also struggling with dovetails. I have taken the channel out using the endmill and now I am going on to the dovetails with the cutter. However, the dovetail cutter is screaming at me or if I change the speed nothing, it just still chatters. How much should I be trying to take with the cutter, with only the tip cutting it seems as though it is really struggling. I`m using an X2 with a 3/4" 45deg cutter on free cutting steel.

 

[websterz]

I am also struggling with dovetails. I have taken the channel out using the endmill and now I am going on to the dovetails with the cutter. However, the dovetail cutter is screaming at me or if I change the speed nothing, it just still chatters. How much should I be trying to take with the cutter, with only the tip cutting it seems as though it is really struggling. I`m using an X2 with a 3/4" 45deg cutter on free cutting steel.

I was cutting a dovetail in 303 stainless last night, also on an x2. My cutter is 5/8" and I was only able to take .005" without the machine bogging down. Feed was approx 3" per minute @ approx 300 RPM.

 

[craynerd]

OK so I guess it is my setup - it must have taken a good number of passes to cut the dovetail.

 

[Krown Kustoms]

Thanks Dean that helps alot.
-B-

 

[Lakc]

Well, the consensus seems to be you just nibble away. While my machine is capable of pretty big cuts, at the cost of the cutters I am not going to push it. If I had a thousand to make it might be worth a few experimental cutters to see how well I can move the metal.

I went downstairs last night and cut another dovetail (pair). Mostly by hand feed until it became repetitious. Machine seemed happier cutting .015 vs .005, but the cutter lived through another set and the edges dont show any wear yet. This, I guess, is as good as I can hope for regarding a non-production job. Oddly enough, the part where I have to mill both sides of the dovetail at once is actually the smoothest part of the cut.

I realize what I was looking for was some magic formula, or at least something close to one, that would give me confidence to crank it up. As I tried to fall asleep last night, a thought occurred to me, WWTD, or rather what would TeeNut do, for those of you who may remember Robert Bastow. Another quick bit of Googling brought up this gem from him.
http://yarchive.net/metal/empirical_feed_rates.html

And he basically sums it up quite well. I do miss his prose, and wealth of experience.

 

[Bernd]

Lakc,

Just read the Tee Nut thread. Nice. That's just about the way I learned to do it to. I listen to what the machine tells me. Although I have broken a few cutters. :big:

Regards,
Bernd

 

[websterz]

OK so I guess it is my setup - it must have taken a good number of passes to cut the dovetail.

Yes, but with power feed and an abundance of free time it was not a problem. ;D