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Woodrat through dovetail problem

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RogerS

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I tried to make a through dovetail with the rat.

I'm using the Woodrat drawer-front set cutter WR 8-9-18-6.5 and that tells me to put the button on 67.5 and spirals on 40 degrees (with an 8mm straight cutter). I've had several goes and there are several problems that I'm struggling with.

First is that the fit is as loose as anything. I've cracked that by changing the spiral setting to 50...but I would have thought that 40 meant 40. Is this normal to have to fiddle with the spirals if you're using WoodRat bits?

But by far the most frustrating is that the edge and side don't line up.

I line up the side thus



Make some cuts so..


but when I put them together I get this



Apologies for the breakout...that's the least of concerns at the moment.

Feeling a tad despondent that I can't work it out.

Many thanks for any advice

Roger
 

Chris Knight

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Roger,

There are several possibilities:-

1. Have you double checked the sizes of your bits with a digital caliper?
2. The pencil line you have drawn is apparently curved (on the side of the dovetail) - is this really so or a photographic wrinkle? I had a problem a while ago with a worn bit that actually created this kind of cut and it resulted in a lot of grief for me.
3. The registration error at the side of the two pieces of wood is very large - are you sure you have not inadvertently got your tail board the wrong way round (easily done if you take it out of the clamps and it is not marked.
4. Did you set the spirals in the empirical way suggested in the manual, or with a bevel gauge, or just rely on the printed suggestions?
5. Are you sure about the dovetail bit you mention - it's not listed on the WR site - should the last number be a 7 and not 6.5?
 

Alf

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Ooo, I got that a while ago; just about that amount of offset too. Couldn't work it out. The dovetails appeared to be snug, but the side was offset. Trouble is I still don't really know how it happened and the thread I started on one of the Woodrat forum incarnations asking about it was lost ages ago. :roll: IIRC I systematically went through the setting up process again, disregarded the settings given for the spirals and used a bevel gauge instead, and all was well. I think somehow a combination of wrong button and spiral setting can give the result, but I'm not sure. So check you've got the button setting right for the correct mounting points for the plate for a start - that could give the "wrong" button setting IIRC. (Ages since I've used the 'Rat :oops: )

Cheers, Alf
 

Chris Knight

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I have just looked at my Drawer front set - couldn't find it earlier. The bits are indeed stamped as you mention - despite what it says on the box and Woodrat's site. However, measuring the relevant bit, I find its diameter to be 6.31mm and this gives a button setting of 64.4 for an 8mm straight bit.

BTW - do be sure there is nothing blocking the router or base plate when you push it back to the stop button when fixing the button setting. I have done this before and you get a completely random result as you might expect!
 

RogerS

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Chris

1/ I have to confess that I haven't..thinking perhaps erroneously that it was 'as it said on the tin'.

2) well spotted...it was my first cut using the dovetail cutter and didn't take as much care as I should...But the overall shape is what sets up the spacing (isn't it?) and so the initial position should be spot on???

3) Don't think so as I just kept the one side peice in the Markup clamp and one edge piece in the fixed clamp. I then offered up the edge piece to the side piece in the clamp.

4) I just entered what it said on their box. 40 was too loose and I went for 50.

Alf..I double checked the button position and it shuould be OK.



I notice that the manual talks a lot about calculating the spiral position if you're not using their cutter but is silent on the question of button position.

Which, incidentally, is a right pain because originally the base plate was fully forward but the setting of 67.5 didn;t give enough meat to tighten down properly in the groove). Going for a larger 10mm cutter meant that the plunge bar hit the stop on the button bar and so that wouldn';t work either. So in the end had to re-position the baseplate. They never show all that in the video!![/quote]
 

aldel

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Roger,
To reach a wider audience on the woodrat you could also try posting on the woodrat forum.
I seem to remember that there has been some mention that the scale has been stuck on a few MM out and so you will have to try an experiment with some positioning.

Aldel
 

Chris Knight

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Roger,

Button position is easily calculated - I don't know if there is still one of the excel worksheets on the web somewhere but I made a simple one ages ago and have another from somewhere - if you PM me your email address I will send them

Spirals are more problematic - at one stage Martin Godrey admitted that the spiral decals were "approximately positioned" - meaning you couldn't rely on another's setting to work for you." This did not seem to afflict the button positioning for some reason.

When you find settings that work - for goodness sake note them down somewhere you won't lose them - saves a lot of heartache. And don't rely on penciling them on the base plate! (DAMHIKT).

Your pencil line is not one I would use. Do make sure you use thin stock for making the MARK and if you get tearout that makes it hard to get a good line, make another cut or, two, or three that does give you a good MARK this is essential.

For tight joints, just cover the line on the relevant side of the MARK with your tailpiece. Initially you may find the joint too tight but experience will soon tell you where to cut.

I usually carry my MARK onto the top of the Rat with a small square, it is easier to see up there as it is not shaded by the sides of the tails.

I usually find that with my baseplate in the central position it covers most of what I need to do.
 

Aragorn

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Wouldn't happen on the Leigh, of course.... Don't worry: coat's already on, adding scarf as we speak...
 

Chris Knight

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Aragorn,

True, but then the Leigh can't handle the kind of bit that Roger is using - makes a joint a lot like one of Rob Cosman's!
 

RogerS

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Of course, one idea running around in my head is that possibly the two jaws on the bar haven't been set-up properly (in other words, the distance between them is wrong). That would explain why there is the offset (which appears to be a linear offset) since the actual dovetail angles fit pretty well.

But then I also seem to remember thinking that my router was turing the wron way, once upon a time :oops: :oops: :oops: so guess that the above idea is duff.

I think I need to spend some time with graph paper, pen and a ruler to try and understand the fundamentals.
 
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