Rats and spirals

[Anonymous]

Well, some of you may recall that a long time ago i procured a 'Rat. And finally, some 8 months later, I've actually had the opportunity to play (don't ask). All in all, pretty impressed - I'm getting through dovetails at least as good as my handcut ones, in a fraction of the time. Major problems with tearout on MDF, but that just shows the crappiness of the material.

First attempt at cutting a through DT gave me a joint that was way way way too loose, caused by inaccurate spiral setting, which is the reason for this post - is there a more reliable method of setting the spirals than that described in the manual, or is it that + experience?

After practicing, went on to make a box with some gash pine I had laying about - set the spirals following instructions, and then opened them out 3 degrees to avoid loose joints - result, way too tight (heck, not too tight - wouldn't even start to fit!). Gradually brought the spirals back in, and eventually got a perfect fit, so that's ok, but would prefer a first time, one cut, everything good method, if such a thing exists.

Cheers
~Esp

 

[Anonymous]

Esp,

The best way is to record the settings that work for you, for each pair of dovetail/straight bit that you use. Once you've written these down, you'll have no trouble at all simply going back to these same settings time and time again.

If I'm using a setup that I've not done before, I cut a few test joints until I've got it just right - tight enough to avoid gaps, loose enough to allow for a bit of glue, and then go to work. Although it's a bit of a pain to start with, once you've got your set of numbers written down, it's a doddle.

AG

 

[Alf]

Esp,

I've had success in the past with using a sliding bevel. Set it to the angle of your dovetails, then use that against the base plate, bring the spirals in and tighten up. Seems to work better for my cranky 'Rat than trying to use the spirals as you're meant to, but your 'Rat may vary.

Of course all this is based on the old days when I actually did some woodworking and could get to the 'Rat. It may be I'm confusing spirals with something else and all that's totally unconnected, in which case disregard all of the above and hand me the DFPs... :roll:

Cheers, Alf

 

[Anonymous]

I've had success in the past with using a sliding bevel. Set it to the angle of your dovetails, then use that against the base plate, bring the spirals in and tighten up. =

Now that sounds good to me. The idea of noting spiral settings for combinations for DT and straight bit makes sense at the start, but I tend to use a huge range of stocck thicknesses, ranging from 6mm to 25mm and above depending on reason for use, so that results in a lot of notes, not to mention a huge amount of waste getting the spirals right in the first place. I think I'll use a combination of the 2.

good advice guys - thanks.

 

[Aragorn]

Could just use a Leigh :wink:

 

[Chris Knight]

Basically this is the method suggested by Alf but illustrated
http://www.woodshopdemos.com/wr-58.htm

 

[Anonymous]

ROFL....the leigh couldn't cope with what I wanted the rat for! A while back, I posed the question - Leigh or Rat, and came to the independant conclusion that the Rat could do it, the Leigh couldn't!

Don't mention that I haven't yet used the rat for the intended purpose! And the Leigh could have done everything I've asked of the Rat thus far (in a whole 8 hours of playing with it!)

 

[Alf]

Chris,

Excellent. I hadn't realised John Lucas had got round to the 'Rat in his dovetailing round-up.

Cheers, Alf

 

[Adam]

To avoid tearout, the technique I use *as suggested by Mike Humphries - is to hop the router over the top of the workpiece, take a bit of a cut on the reverse side, and then hop it back to the side closest to you to make the cut. This way, you eliminate all tearout whatsoever, when you break through to the opposite side.

Adam

 

[Anonymous]

Adam - I used that method - works perfectly on wood, but the MDF just seems to peel away - not really sure how to describe it, but suffice to say it wouldn't be good to make something like that

 

[johnjin]

Thanks for that Chris.
And I guess to everyone for this illuminating discusion. I think the Woodrat will be my next purchase as it seems so flexible. I've got to admit that I am still a little confused but the cost of this for what it is capable of doing is a huge saving compared to other methods when you are talking about mortice & tenons and dovetails. I also like the fact that any dovetail cutter will work with the rat. On top of all this it seems to pass very well as a general router table as well.
What more could anyone want.
Thanks for the Info

John