CNC MDF Wardrobe build - Gap between overlay wardobe doors

[geddhedd]

Hello all.

We are having a loft conversion and would really like some built in wardobes to fill most of one of the walls.

After hearing some pretty frightening quotes from other people who have had built in recently, I have decided to get the wardrobe CNC'd at a local place in 18mm MR MDF. The price seems ok based on initial quotes.

I am a design engineer, but having never done any furniture before there a few things I am unsure of.

One of which is:

What sort of gap do I leave between the wardrobe doors?

Currently I am basing it on using 4 full size carcasses with overlay doors. and 3 shorter carcasses.

I have made the doors 4mm shorter in width than each carcass, which leaves 2mm between the outer doors and the 'side cheeks, and 4mm where the doors meet in the central carcasses.

Does this sound about right? Too big?

What is a normal gap between wardrobe doors on something like this?

Many thanks in advance,

Ged

 

[foxhole]

Sounds fine , if you check out your kitchen units you find on a 600mm wide carcass the doors are 596mm .Does not need to be MR mdf.
Did something similar with storage cupboard at top of my stairs .

 

[big-all]

just a point as you are using 18mm mdf will the hinges cope well with 18mm mdf rather than 15/16mm contiboard type materials i simply dont know iff hinges and materials will operate fully and without clashing/conflict with other surfaces ??

 

[JohnD]

My kitchen is made of 18mm units, laminated chipboard by Egger. A cheaper line uses 15mm, but AFAIK there is no difference in the hinge. Mine are just from the ordinary Blum range, and have plenty of adjustment.

For making specials, I found a metal Dowel jig really handy. The factory made ones also used glued dowels.

I do not have a woodworking workshop but these cabs are really simple.

 

[Deleted member 174758]

Kitchen and bedroom units almost always have the doors made 5mm undersize - so a 600mm wide x 720mm high unit would have a 595 x 715mm door supplied. The same is normally true of units with double doors, so a 1200mm wide unit would normally be supplied with 2 no. 595mm wide doors. You can pull this up a couple of millimetres, but more than that and the doors will potentially clash if both are opened simultaneously. You also need 2mm margin between the hinge edge of the door and the edge of the carcass to prevent this on that edge, especially if the catrcass terminates hard against a wall or partition

As to 15mm being "cheap", it isn't necessarilly the case. High end German kitchen manufacturers (e.g. Poggenpohl) use 15mm for their carcasses and I doubt that you say they were poor quality. Plain fact is that if you are scratch building and unable to get CNC levels of accuracy for drillings 18mm gives you a bit more "meat" to play with

If the OP is getting his material CNC machined and the machine shop has a point-to-point machining centre or a CNC with a drilling head it may be worth his while asking them to drill his dowel holes for him (normally 64, 96 or 128mm centres x 8mm holes for 18mm MDF) together with any 3 or 5mm shelf peg holes (32mm centres - Google "Blum Pearls" or "System 32" for details of how these are set out)

 

[geddhedd]

Sincere apologies everyone.

I've been so busy with work and the loft conversion I completely forgot to check this thread!

From what I have read the 18mm MDF is OK with the blum hinges I have been looking at and I have found people on YouTube using 18mm MDF for carcasses so that's reassuring. I just need to have enough on them for the height so looks like it will be 4 hinges per door.

Thanks all for the reference door to carcass widths and other advice. Very very useful. I think it's less of an issue if you have the tools and space to do this in a workshop as you could make them with a very small gap and skim it off as required. But as it will all be cnc'd I have to be really sure on everything before I push the button.

Sounds like I'm not too far off so far though which is good.

Job and Knock you are correct, the intention is to get every hole and recess I can think of machined in by the cnc vendor, so it should just be like a giant piece of lego which I'm actually really looking forward to putting together.

The OH is getting 1 cabinet maker in to quote tomorrow who has done a friend's recently and his price was less freightening than others we have seen. The quality was also very good. But to be honest I have enjoyed drawing up and hope to enjoy putting together so a large part of me is hoping his quote is still expensive enough to justify me cncing them

 

[big-all]

just keep in mind you need wiggle room all round
if the opening is say exactly 600mm at every point side to side measured and 100% plumb and level on all planes then you may get away with 10mm all round but iff the bottom back corner is 40mm mm out compared to the top front then you need 50mm minimum wiggle room iff not 60mm

you need to find any high points and any dips as they detract from the usefull space

 

[Deleted member 174758]

From what I have read the 18mm MDF is OK with the blum hinges I have been looking at and I have found people on YouTube using 18mm MDF for carcasses so that's reassuring. I just need to have enough on them for the height so looks like it will be 4 hinges per door.

18mm is the modern equivalent of the old 3/4in (19.05mm) blockboard or laminboard which was used at one time for carcassing. It is pretty much a standard in the UK and is far easier to source than 15mm. another reason that German manufacturers use 15mm is that they can get more boards on a truck for export (weight and size)

I think it's less of an issue if you have the tools and space to do this in a workshop as you could make them with a very small gap and skim it off as required.

I seem to recall a couple of manufacturers who worked to a 3mm gap, but that is for pre-finished doors whereas yours are sized as raw MDF, so after they have been sealed, primed and painted I'd expect the sizes to "grow" 1mm or so bigger in real terms

...the intention is to get every hole and recess I can think of machined in by the cnc vendor, so it should just be like a giant piece of lego which I'm actually really looking forward to putting together.

Then remember to make allowance in your sizes for assembling flat on the floor and rotating up into position. Attic rooms are often difficult to get full sized furniture into - it is far easier to move individual panels upstairs and assemble it where it will live. Also consider how you are going to pull up the joints in final assembly - in a workshop you'd normally assemble on either a bench or trestles and clamp the item together using sash cramps whilst the glue goes off. Something the depth of a wardrobe (600 to 700mm deep) will require at least three cramps per end (these needn't be bought in - they can be home-made from 2 x 1 softwood). Finally have you considered the plinth? This really needs to be dead level, regardless of what the floor is like. I always favoured making up a softwood ladder frame by screwing 2 x 2 or 3 x 2 softwood together (a trick from bar fitting to make life easier), positioning that, levelling up using packers beneath the frame as required then angle-plating and screwing down to the floor:

Ideally I'd say your design needs the carcass to overhang the ladder frame a bit to allow comfortable standing hard by the cabinets without stubbing the toes. This rough frame is faced off by a rip of MDF which can be scribed to the floor (jigsaw, block plane) as you would scribe a kitchen plinth:

If you are lucky enough to have exactly plumb walls (checkable with a plumb bob or a laser) you will most likely be able to build straight onto the frame. I'd caution about making your carcasses tool big as the heavier they are the harder thet are to assemble and manhandle into position - better to build separates and join them together (clamp together on the front edge, align and screw beneath where the cruciform plates for the hinges will go to hide them - the ones at the rear of the carcasses will need to be countersunk, and filled with 2-pack filler afterwards)

One way to design carcasses is to set your top and bottom panels within the sides, thus:

This is commonly used on kitchen cabinets. In this form, without a back or some form of additional bracing the carcass is going to be very weak and can break the joints if lifted awkwardly, so some form of bracing or back, either temporary or permanent is advisable.

With out of plumb walls a scribe strip can be made up and goes between the end of the carcass and the wall. Obviously an allowance for this must be made when designing the carcass (here shown as 50mm). One way to accomplish this is to screw and glue a piece of 2 x 1 planed softwood down the edge of the carcass set back by the thickness of the scribe strip from the front face of the carcass (lt. yellow). In this case I have drawn the scribe strip as 12mm thick. Accurate positioning is essential and if you don't already have a decent combo square when doing this, you will need to get one (recommend a Bahco CS1560 or CS300). The scribe strip is cut and then scribed to match the wall (dividers/pencil compasses, jigsaw, blockplane) and is fixed to the front edge of the timber batten (glue and pins). The edge to be scribed is highlighted in red. You are aiming for a gap of 1mm or less all the wal down so that it will caulk in nicely. Note that the doors will need something like 2mm clearance between their back and the face of the cabinet - this is shown here and is what the hinges will give you more or less by default

This does mean there will be a set back from the front faces of the doors to the scribe strip. If you wish to avoid this a wider piece of 18mm MDF should be affixed to the side of the cabinet so that the edge of it protrudes 8mm from the face of the carcass (if using a 12mm thick scribing strip) to bring the face of the scribing strip flush to the doors. In this case I've illustrated the support strip as being 18mm thick x 50mm wide and I'd screw and glue that to the side of the cabinet before manouvering the carcass into position and doing the scribes. If you used softwood for the side of cabinet batten it would not paint out the same as the front of the scribe strip which sort of spoils the effect

To further disguise the joint in the MDF a shallow V-joint can be planed in as shown below. This is only 1.5 to 2mm wide and when you come to paint the carcasses you can take the doors off and "wipe" a thin bead of caulk down the length of the "V" with your finger. This has the effect of bith hiding the joint (which can show up as a crack in the paint over time) and of softening the V-cut to a shallow, rounded groove which is not very obtrusive, especially as it is half hidden by the door

About the only other bits of advice in terms of design that I can give at this juncture is that when designing these units bear in mind that a factory made unit is often 600mm deep, presumably because they are made from standard 1220mm wide panels, however I have always found that 600mm is a bit shallow for mens jackets. In fact 700 to 750mm may be preferable, but that may involve either excessive wastage or the purchase of larger sheets of material, such as "jumbos" (circa 3020 x 2000mm depending on source). Always go for MR-MDF over standard MDF, being denser it machines to a crisper edge. Lastly before painting break the arrisses (the sharp edges) just slightly with some P120 alox paper held in your hand - the slight radius will paint out better

 

[geddhedd]

Thanks JobandKnock.

Some great references and advice in here.

You have basically given me loads of information I hadn't managed to garner from several videos / threads.

Very good point regarding the paint build up / growth. I hadn't considered that. There is a small chance (if costs allow) we will use Valchromat for the doots instead but depends on costs really. Most likely we will paint so I need to factor this in.

For the size part of me is considering splitting the carcass so it isn't full height. Then having top boxes that slide in later and having the doors span the carcass and top box. I worry if I make full height and assemble the wardrobe horizontally it may be extremely difficult to then maneuver vertically and onto the plinth. Not sure on how professionals tackle this generally. I have seen it done both ways (full height with space for scribes / 3/4 height with top box added at end, still with scribes)

The only negative of the top box is it is another piece to try and make square, but think it is the best route until I hear otherwise.

I have considered the plinth but I am in 2 minds about the best way. I could assemble a ladder style as you suggest but worried it would be tricky for me to get dead flat and level with my tools / experience. I may be overthinking this though.

I have also considered making one at the CNC place as shown below. It is overcomplicated but would hopefully take any user error out of the way as everything is aligned by shallow slots and I thought why not if I am getting everything machined anyway. It only uses one sheet 18mm MR MDF. But open to ideas why this might be a bad idea. The widths align with the edge of each Carcass for something to sit on and take the weight.

Thanks for the advice on the cabinet constuction. I think I may have overcomplicated mine but again if CNC'd I have just added features to hopefully make alignment and construction super simple for me.

This is a cross section through the middle. I have used lapjoints top and bottom

There is a groove for LED's near the front (shown below) and also a overhang / stopper for front to back alignment. Still need to add doglegs for the router paths but will look similar to below.

For the back I have used 9mm MDF sitting in a recess which I am hoping should give some decent support. Thinking I may use panel pins on the rear as worried it may end up being too close to the edge for an M3.

Thanks for the images and details on the scribe strips, I had left some room but wasn't sure on the best way of tackling so this has saved me a lot of research!!

I'm hoping everything should be plum as it is mostly brand new. Fingers crossed.

Understood on the 600mm depth. This is pretty much what I have. It does make it easier for machining with the place I am using as it is just less than half so just enough room for 2 with the 600 plus room for the tool.

The place I am intending to use only uses MR MDF which is handy.

Never heard of breaking the arrisses, really good to know thanks!

Cheers

Ged

 

[Deleted member 174758]

I have considered the plinth but I am in 2 minds about the best way. I could assemble a ladder style as you suggest but worried it would be tricky for me to get dead flat and level with my tools / experience. I may be overthinking this though.

DON'T make your plinth out of MDF - not only is that design very complicated, problematic to assemble straight and wasteful of machining time, but any MDF plinth won't be particularly stiff and may well bend to the shape of the floor if the floor isn't level (and many aren't). From experience screwing or nailing a softwood ladder frame together and packing really will be far faster, easier and cheaper. It will also (most importantly) be stiffer.

Another minor point about your plinth design - you show what appears to be a butt joint at the front. If you need to join plinths, skirting, etc it is always better to have a scarfed joint where a mitre cut is made ate the end of each piece. This gives a greater glue area at the joint as well as being less likely to crack in the future. In the case of a softwood plinth frame this is a lot easier to achieve with a 6 or 12mm MDF facing

Alignment of the plinth is really simple - you use a spirit level to check level front to back and end to end, starting in one corner and working left to right (or right to left). Not got a long spirit level? Tape a shorter one onto a straight length of 3 x 2 planed softwood (just eyeball down the length to see if it is straight first). Having a straight and level plinth which is properly fixed down to work off is the basis of getting the rest of the structure in without pulling your hair out

...on the cabinet constuction. I think I may have overcomplicated mine but again if CNC'd I have just added features to hopefully make alignment and construction super simple for me.

If you use rebated joints it is again very wasteful of machining time as well as producing a much weaker joint, Your use of rebated joints suggest that you have probably been watching American (or Ameriucan-influenced) videos, where they often use a table saw with a dado head to make their joints. Whilst this technique may work with plywood (and is really designed so that the joints can be nailed together) it is a very poor approach for MDF and chipboard or MFC as the joints are weak and can fail during manhandling of carcasses to get them into position (American DIYers don't use much MDF or MFC/chipboard and are therefore a poor source of information on effective joining of these materials). Rebating the joins also reduces the amount of "meat" you have to connecty the components with dowels or screws - a "standard" dowel is something like 8 x 30mm (dia x length) which ideally requires a 16mm deep hole in both elements - put a 5mm deep rebate in your top panel and you won't get enough depth. This is why the industry nowadays (and bench joiners in the days before we had CNC routers) used overlaid butt joints and dowelled, biscuited or more recently Dominoed the joints.

As to the backs, a common fault with wardrobe backs is that people can be heavy handed and throw stuff in. the most common failure areas are at the bottom (shoes, etc) and in the middle, and putting the backs in grooves doesn't help. By all means groove the bottom and sides to allow you to slide in a back, but put a gap in the top to allow you to do this - trying to assemble a back in a large carcass which is trapped round 4 sides is a sure way to die of frustration. Also check the back thickness - 9mm isn't always 9mm thick! In addition machine your back a couple of millimetres shy of the required size - you'll need some wiggle room to get it in. Personally if going for a back in a groove I'd make it out of 18mm stuff with rebated edges. OK, it's heaver, but it's much thinner and a lot less likely to be punched out (particularly at the bottom) should the wardrobe be overloaded. With most backs, though, I'd probably just run a rebate in the carcasses and glue/pin the backs in place, adding an extra "splat" across the bottom of the panel at the back to stiffen that area

TBH I think that you've overcomplicated your design, particularly the plinth, and the you would find a simpler design easier to make and assemble. Frankly, I could make this lot with a relatively simple set of power tools - the main "specialist" kit I'd opt for would be a router and rebate cutter, a biscuit jointer and a plungeing rail saw (or a circular saw with a home-made straight edge). The use of nested machining (where multiple components are machined from a single sheet) means that you cannot side or end drill the components which makes conventional dowelling a no-no. If you are nesting it is far better to design the piece so that you can use the appropriate KD fittings to assemble your item(s)

 

[geddhedd]

All fair points on the above.

I think I have a fear of getting everything perfectly machined at the CNC place and then messing it up with a uneven base that I have done by hand. But it sounds very much like making the base in MDF is a big no so I will do this as you have suggested. I had actually never seen anyone do the base in MDF so it was a bit of a risk anyway even before your comments.

For the joints I actually got it off a website as below so I thought I was in safe territory! - https://www.finewoodworking.com/2017/10/05/building-with-mdf

It is an american website though

There were various joints it suggested, but the one's I chose were based on the fact that for the CNC place it is much easier (and cheaper) to machine on a single face and they can't really machine into the ends without a big upcost)

I could avoid machining the faces altogether and use butt joints, but I was worried about getting the alignment wrong

The whole build is designed around the single face machining and taking out the most likely part to go wrong (which is my relative inexperience with hands on cabinet making)

But it sounds like I need to have a bit of a rethink on how to join!

Cheers

 

[Deleted member 174758]

Example of what a plain rebated corner will look like - assumed a 10mm wide x 6mm deep rebate carrying a 9mm thick MDF back panel. Remember, this detail is at the rear of the carcass and will never be seen

As I stated though - don't trust Yanks when it comes to MDF! And in any case that technique is for hand wood working, NOT CNC work

 

[Deleted member 174758]

I could avoid machining the faces altogether and use butt joints, but I was worried about getting the alignment wrong

There is a tendency with CNC to think that if you can do it with the CNC, you should do it. The guys selling you the time on their machine will be happy to charge you an extra 30 to 60 minuters of their (highly priced) machining time without necessarilly giving you advice on technique. That isn't really the best approach IMHO. Quite frankly a wardrobe carcass is a straightforward item to produce and it would cost you a lot less to have somebody break down your components accurately on a panel or beam saw then just rebate for the backs (or even just screw them onto the outside!) and buy a low cost biscuit jointer to do your joints (which will probably cost you the equvalent of an houtr's CNC machiningh). Biscuits are a relatively cheap, fast and accurate way to ensure good alignment - tyake a look at something like the Trend web site for examples

 

[geddhedd]

I think for me because I often get things machined or tooled in the day job it seemed like a good way to go about this project as it's what I am comfortable with. Although i do a fair amount of DIY and have made fences and gate's and things like that, this just seems on the face of it beyond my hands on skill set. But I am going to look down this route too and cost everything up everywhich way and see which works out best. The loft won't be ready for the built in until after Christmas now, so have a bit of time to play around with everything.

The person who was going to be quoting on the built in isn't round till next week now. It will be really interesting to compare the 3 methods cost wise. Professional cabinetmaker vs CNC version vs full DIY version (more like your last post). I'll see where I get to and happy to update if people are interested.

 

[Deleted member 174758]

This is how easy biscuit jointing is - note how alignment in one axis is automatic (the tool takes care of it) whilst in the second axis is takes very little effort. The main thing is to start with accurately machined components

As you can maybe tell I'm not a DIYer (at least so far as woodworking goes) but I have had experience of interior fitout (design, bench and site) as well as knowing a bit about CNCs