Real dovetails on a CNC?

[Mad Dog]

The prospect of purchasing a CNC machine to perform tasks which would otherwise require a template or additional tool with a router is very appealing. One such task is dovetails. An eariler thread mentions a site which allows the user to create joints which would be nearly impossible with a traditional setup or even hand tools. Once again, nice but not what I was looking for. What would be very helpful, considering the expense of a good dovetail jig, is the ability to perform the same operation on the Pro Plus. A one time jig would need to be built to hold the two pieces at 90 degrees to each other and the necesary G-code written to perform the task. While I have no doubt the Pro Plus will handle this, the issue of running the unit over the edge by 1 to 2 inches is a show stopper.



After looking at the design, would it be possible to switch the router carrier (Z-axis) 180 degrees so the Y axis stepper motor is now on the opposite end? If so, the router can easily extend past the end of the table to perform the dove tail operation. I believe if this configuration were successful, you could create perfect dove tail spacing every time regardless of the width of the material simply by adjusting the G-code and save yourself from buying an expensive jig.

I'd like to know if there is any interest in this concept and if it is even possible.

[REG]

My thought on this is rather than flip the carrier I would look into the Shark Pro Plus table extension set that is available and tool to that end. But, the clencher is the extension would cost more than most dovetail jigs. Now, while talking about jigs, you can use the Shark to make the jigs for dovetails.
I wouldn't be too fond of flipping the carrier as that you will still be working very close at the Y-axis end limit. I can understand your intent but I don't think it fits within the design of the Shark.

Bobby

[Mad Dog]

Thanks for your thoughts Bobby.

I've seen this done on another CNC machine and it appeared to be within the design limits of the Shark Pro Plus. I agree you would be very close to the Y limits even if you moved the entire table to the the very edge and rotated the gantry 180 degrees. This was of similar concern with the other machine however there was just enough room to accomplish the task with material around 1 inch thick. I've not seen the table extension you speak of so if you have a part number and know the company who carries it, that would be helpful too. I was thinking the addition of a single piece of multitrack cut to about 28 inches and attached on the end of the unit would be enough vertical surface area to support the material plus the slots would give you the ability to use off the shelf clamps to hold the material securely as well as providing an attachment point for a reference block for repeated cuts. I'm sure there will be costs associated with this type of modification, however my first hurdle is to determine if it is within the design limits of the pro plus.

For those of you who have a Shark Pro Plus, I would like to know how far the head travels beyond the edge of the metal frame that supports the top to see if there is enough room before you hit the Y axis limits. If there is at least 2" over travel beyond the edge of the base, I think it will work. I only ned 3/4" for the multi track, another 3/4" for the material plus 1/2" for bit clearance. Of course, more would be better. Other wise, I guess it's a moot point.

For me this is a deal breaker so any information would be very helpful.

[REG]

The info. from Tim Owens on the table extension is here: http://www.cncsharktalk.com/viewtopic.p ... 8&start=10
As for having the gantry/tool over-extend the end of the table, yes, this can be done but you would need to flip the gantry as you mentioned since the router side of the gantry is facing the same as the Y-axis motor. One could pull back the T-slot table on the "-"Y-axis side but the Y-axis motor would protrude preventing the use of the table end. Fliping the gantry (if the gantry alignment would allow) then pulling back the T-slot table to the "-"Y-axis side (the Y-axis motor end), would allow you to use the +Y-axis side with probably 1" - 2" reach beyond the stop of the +Y-axis. You would have to check with Tim Owens to see if the gantry can be flipped. I don't see it being a problem but the gantry and base are drilled for a standard finished assembly.

Bobby

[Tim Owens]

I am not an expert on dovetails but what you are looking to do should work on the shark or pro either turning the gantry around or cutting a slot into the table top so you can extend it down into it at the end of the machine by the motor.

Putting it on the end will work since there is about 2 inches of travel off the end where you can machine.
For those with a pro plus they would have to either take of the aluminum top or readjust it so they can get enough movement on the end.

Thanks

Tim

[Mad Dog]

I am not an expert on dovetails but what you are looking to do should work on the shark or pro either turning the gantry around or cutting a slot into the table top so you can extend it down into it at the end of the machine by the motor.

Putting it on the end will work since there is about 2 inches of travel off the end where you can machine.
For those with a pro plus they would have to either take of the aluminum top or readjust it so they can get enough movement on the end.

Thanks

Tim

Just the info I was looking for Tim. Thanks for the quick reply.

Do you think it's too much to ask the wife for a Pro Plus for Valentines day?

[Tim Owens]

That might depend on what this thinks you are going to get her for V day.
But hey you could say your going to redo the kitchen cabnets with the new toy.

[Mad Dog]

That might depend on what this thinks you are going to get her for V day.
But hey you could say your going to redo the kitchen cabnets with the new toy.

Rebuilding the kitchen was on the list of honey do's...

Could be a win/win!!

[billb]

Re-consider using a Doveail Jig and a medium size router. Each cut will take only 2 seconds.
The little 1HP router on the CNC is too small in my opinionand will take multiple depth passes, which you can't do with a dovetail bit.

[Mad Dog]

While a dovetail jig would be the best, a proper jig will run you over $500. Sure, you can purchase less expensive versions or even make your own templates or for that matter, use the CNC machine to make customer templates. But why add all the middle men to the equation if you were able to create the electronic template and leverage the power of the CNC to handle this task? For me, if eliminates the trouble of purchasing another single purpose tool that requires far too much set up time to accomplish the desired task.

As far as power is concerned, the 1hp motor is more than up to the task as most common dovetail bits use the 1/4 shaft or 8mm. This is where the control of the CNC helps control the speed of the cut so you shouldn't have an issue there. Even the latest wood mags are claiming the smaller routers are nearly as powerful as the standard size units.

Finally, this was a way to justify the purchase of the CNC as a "multi purpose" device capable of eliminating those expensive jigs. So, right now I'm still on the fence with all of this. Your points are well taken and noted.