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Mortice & tenon glue line thickness

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SBJ

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Infact, a 10x5 sheet would get you
2
 

Louise-Paisley

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I am paying £20 a sheet for 8 x 4, so a 10 x 5 will likely be nearer £30 I guess. Using quarter sections I can get 4.75 rims from one 8 x 4 sheet with little waste using a 10 x 5 I would get two with much more waste.

While I do agree completely that time is money and often it makes better sense to pay more for materials to save even more in time (the flexi ply being an example), my pal who is helping me wants to be involved more. I will be giving him some payment but he is really just interested in helping out for something to do rather than sit in the house watching soaps :roll: So the idea is that he will either cut and pre shape the parts while I cut the joints or visa versa.

Also, while I am far from an eco warrier, I do where possible try to minimise the wastage of things in general and from visits to the skip site with waste it would seem that MDF is not a recycle item and it goes in the general refuse skip so not the best material to waste.

If I was to be working alone on them then I would likely give the idea a lot more thought to save time cost but at the moment at least it is not really much of an issue and benefits of jointed outweigh the benefits of single pieces - I think.
 

Eric The Viking

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If you do semicircles, you can just about get one set per sheet of 8'x4':
semicircles.png

If you scale down to 48" outer diameter (proportionally), you can get one and a half sets (three circles) per sheet:
semicircles 48.png

Those are to scale, using the dimensions you gave. If you stick with quadrants, you get much more from the material, obviously, but semicircles should be far easier to glue-up, as you just have the two parallel glue lines.

It all comes down to your time versus materials cost really.

And I almost forgot: given what you're using them for, you really will need some sort of jig to true them up with once they're glued, and even if you cut them as whole discs.

Even though it's rotating at slow speed, much more than a few millimetres out of round will make the finished item look pretty rough, as will the drum if it doesn't have a proper cylindrical shape rather than slightly conical.

I think I'd make some sort of cross-shaped frame with clamps so you can spin the ring against a sander before you rout the groove. The inside face would be a bit trickier but not insurmountable. Doing the thin 'treadmill' cylinder will need very accurate cutting and clamping I think.

E.
 

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Louise-Paisley

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Eric The Viking":3qoa8k86 said:
If you do semicircles, you can just about get one set per sheet of 8'x4':
If you scale down to 48" outer diameter (proportionally), you can get one and a half sets (three circles) per sheet:

Those are to scale, using the dimensions you gave. If you stick with quadrants, you get much more from the material, obviously, but semicircles should be far easier to glue-up, as you just have the two parallel glue lines.

It all comes down to your time versus materials cost really.

And I almost forgot: given what you're using them for, you really will need some sort of jig to true them up with once they're glued, and even if you cut them as whole discs.

Even though it's rotating at slow speed, much more than a few millimetres out of round will make the finished item look pretty rough, as will the drum if it doesn't have a proper cylindrical shape rather than slightly conical.

I think I'd make some sort of cross-shaped frame with clamps so you can spin the ring against a sander before you rout the groove. The inside face would be a bit trickier but not insurmountable. Doing the thin 'treadmill' cylinder will need very accurate cutting and clamping I think.

E.

Yes, with quarters I get 4.75 rims to a sheet easily.

And of course you are right about the rims needing to be trued up, I have seen a similar wheel where this has not been done and it looks awful when the cat runs in it even though its only a couple of mm out of true it completely spoils it.

They are oversize when cut, after assembly and gluing I have a large plywood X with a pin in the centre and the circle marked on the arms, I stick the glued rim to the cross with double sided tape and fit a compass jig to the pin in the centre (just made a new compass jig for the new Triton router which uses the quick release pins). I then trim back the rim to the finished size with the compass (they are oversized by 5mm inside & out) and then cut the groove for the bendy ply.



This was a previous attempt with ply rims half lap jointed and kerf cut running surface, this would have been near on indestructible with a full track but the kerf cutting was not smooth enough on the outside and far too easy to break when fitting so it was abandoned in favour of MDF rims and Bendy ply.



I set up the woodrat and cut M&T's on four parts of rim today and they went together surprisingly well - probably not in the eyes of some of the craftsmen here, but for me it was pretty darn good - so I have glued that up and clamped with a strap so I will see what its like when its cured maybe on friday (busy tomorrow)

Cutting the joints on the woodrat was actually fairly quick and easy, once I had marked out the first one I just positioned the bit at strategic points and made reference pencil marks on the sliders, cut one to test and it was good so cut the rest to the lines and they all fitted exactly the same. I was really quite impressed, this is the first time I have used the woodrat in anger so to speak and to be honest everything turned out much more accurate than it has done when I have been playing with it with scraps of wood.

One thing has become quite clear, if I am to continue with the mortice & tenon plan then I need to get me some upcut spiral bits because its a pain cutting the mortice with a normal straight cutter with the dust in the mortice
 

siggy_7

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Louise-Paisley":kf3v1lap said:
One thing has become quite clear, if I am to continue with the mortice & tenon plan then I need to get me some upcut spiral bits because its a pain cutting the mortice with a normal straight cutter with the dust in the mortice

I'd recommend trying a carbide centre-cutting endmill if that's suitable - they are available much cheaper than the spiral fluted router bits. You can also get them with more flutes (up to 4), which makes the bit stiffer. Only thing to bear in mind is that the shank size will be the bit diameter, so for anything that isn't the same size as your router bit you will need something like an ER20 collet adapter, which Axminster sell.
 

Eric The Viking

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Cor this is an interesting thread!

Thanks for raising the subject, Louise.

One other thought, while I remember it: Your kerf cut version would have excellent grip, but I can see the fragility of it. Years ago, when I used to do a bit of dinghy sailing, we used to mix fairly coarse but clean sand with polyurethane to get a grippy finish for wet plimsolls (no trainers back then!!!).

Do you get a good enough finish just by painting the wood or are you doing something similar with grit?
 

Louise-Paisley

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Eric The Viking":384sj5ww said:
Cor this is an interesting thread!

Thanks for raising the subject, Louise.

One other thought, while I remember it: Your kerf cut version would have excellent grip, but I can see the fragility of it. Years ago, when I used to do a bit of dinghy sailing, we used to mix fairly coarse but clean sand with polyurethane to get a grippy finish for wet plimsolls (no trainers back then!!!).

Do you get a good enough finish just by painting the wood or are you doing something similar with grit?

With the kerf cut bend we were planing on back filling the kerfs with resintite/ sawdust. The inside surface will be carpeted when finished so plenty of grip but also a level of soundproofing - My wheel has a textured paint finish inside and when they gallop in it it sounds like a heard of elephants charging about!

The main problem with kerfing was it is real easy to break, irrespective of how deep the kerf cuts are, we broke two panels and fitted one which is unacceptable. Also the time involved kerfing (I made a sled jig but still takes time) and filling the kerfs was significant.

I did ask for prices of bendy ply and was quoted £105 a sheet + vat so decided to kerf, I have since found bendy ply at £23 a sheet which is a touch more realistic LOL
 

Louise-Paisley

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Well the mortice & tenon joints worked very well, took the straps off today and the rim is pretty darn solid and definately plenty strong enough for the task.





I jointed up the second rim today so tomorrow its trim them to size, cut the groove and fire in some bendy ply.
 

heatherw

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I will be fascinated to see whether you can persuade a cat to use the thing after all this hard work, contrary animals that they are. Mine spend most of their time lying down when they're not eating playing or hunting.

Oh, and I've never made a mortice and tenon in MDF, but I have joined it edge to edge with biscuits.
 

Louise-Paisley

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heatherw":3llbkok8 said:
I will be fascinated to see whether you can persuade a cat to use the thing after all this hard work, contrary animals that they are. Mine spend most of their time lying down when they're not eating playing or hunting.

Oh, and I've never made a mortice and tenon in MDF, but I have joined it edge to edge with biscuits.

I already have a cat wheel, different design to this completely. My two bengals spend a huge amount of time in it, they fight over it even! The two moggies have never been near it and just seek out a warm spot to sleep :roll:
 

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