Router table, insert plate levelling question

[JJ1]

Hi,

I'm just in the process of building my first router table, in fact I've almost finished it but I've decided to remake the insert plate with a few improvements over the first one I made.

My question relates to the best method for levelling the plate.

Basically, the insert is made from 18mm MDF and will be reinforced with two 30cm lengths of 14mm box section steel which I'll recess into the underside of the insert plate. The insert plate will be sitting on a 1.5cm rebate cut into my 36mm MDF table top. So far so good, but what I would also like to do is add some levelling screws to ensure the plate stays nice and flush with the table. I used strips of thin card before, which worked fine, but I would like something permanent and adjustable. My thoughts were to buy some grub screws about 12mm-16mm long and insert one into each corner and maybe one in the centre of each side. I believe the grub screws are fairly flat bottomed, rather than pointed ones. I then thought that having them press into the MDF rebate that the insert plate rests on might not be ideal, in case they 'sink' into the MDF a bit. I decided to buy a one metre strip of 1cm wide x 2mm thick flat steel bar which I intend gluing on top of the rebate to give a stronger, flat edge fot the insert plate and grub screws to sit on. To compensate I'll also route a 1cm wide x 2mm deep recess around the outer edge of the underside of the insert plate.
The part where I'm a bit stuck is with fixing the grub screws into the corners of the MDF insert plate. I was concerned that they may 'pull through' over time, or not remain properly in place in the MDF, what with the weight of a Triton TRA001 router combined with the weight of the reinforced insert plate bearing down on the grub screws.
One possible solution I though of, was buying some small threaded inserts. Gluing them into the corners of the insert plate and then screwing the grub screws into those. I'm guessing this should work (please correct me if I'm wrong).
I then thought that instead of messing about with threaded inserts, which I would have to buy especially, I could cut a small 1cm square of 2mm thick steel, tap a threaded hole into it, recess and glue it into the underside of each corner of my insert plate where the grub screws will be located.
Do you think this should work ok? The purpose of the tapped, steel corner inserts is to ensure the grub screws are securely fixed in place and won't pull through the MDF insert plate.

Any advice, tips, suggestions on the above would be very much appreciated. Thanks

 

[paultnl]

personally I think it sounds a bit over engineered. What is wrong with using shims?

 

[longinthetooth]

1 - I'm unclear why you'd want to reinforce an insert plate - does it span 3 metres, or something?

2 - Apart from that your basic scheme seems to be sound - hardness of bearing surfaces (that includes threadways) is essential. MDF has tough-ish faces & a soft core ...

3 - If supplied grubscrews were pointed, their points could be ground. But you don't need hardened screws in this application, any mild steel screws would be fine ... they are to provide a bearing surface, not a gripping point. Easy work.

 

[Reggie]

Your idea is sound, although I'm not sure I'd use grub screws, my bosch router table uses plain old nuts and bolts. Sink some nuts into the top of the part of the table that is holding the insert plate, you can then use delrin tipped bolts to level the plate, very simple, very effective. t-nuts might be effective for this too. and with the bolt heads it's very simple to get a spanner in to adjust.

 

[siggy_7]

I'd use grub-screws in your situation. Only put one in each corner though, more than 4 points of contact and you're just creating problems for yourself when levelling. Sounds like you have a very stiff design for the insert as well so it shouldn't sag. As for the method of including them, I'd use threaded inserts - cheap and effective. Don't go all the way through with the hole for the insert (just install flush to the under-side), but drill the smaller hole for the grub screw all the way through so you can adjust the level from above.

 

[Mike.C]

I'd use grub-screws in your situation. Only put one in each corner though, more than 4 points of contact and you're just creating problems for yourself when levelling. Sounds like you have a very stiff design for the insert as well so it shouldn't sag. As for the method of including them, I'd use threaded inserts - cheap and effective. Don't go all the way through with the hole for the insert (just install flush to the under-side), but drill the smaller hole for the grub screw all the way through so you can adjust the level from above.

+1 sounds the perfect way to do it.

Cheers

Mike

 

[Steve Maskery]

I'd put grub screws at each corner, and let them sit on inset magnets. That means they don't chew up the MDF and the magnets help to stop them vibrating loose. If you can't get the small magnets, just inset a penny at each corner and use a drop of Loctite instead.
S

 

[JJ1]

Thanks all for the very helpful and excellent advice.




The reason for reinforcing the insert plate is quite simply because the original un-reinforced one sagged after just a few hours of use. There was about 0.25mm of a gap. How detrimental that would be, I don't know because I don't have the routing experience to know, but I'm guessing it could well be an issue for some routing operations.
I had to make a new insert plate for other reasons anyway and I thought it would be pretty pointless making the same again when I knew it would only sag again. For the sake of £4 for some box section steel and a minute or two to rout a rebate for it, it seemed silly not too and hopefully I'll have a much stronger and longer lasting plate.


I thought about sinking some bolts into the table but I preferred the idea of making any levelling adjustments from above the table if possible, just for convenience more than anything.


Thanks for the tip about using only four grub screws, I certainly don't want to complicate things and use more if they're not needed. That's also a good tip about just inserting the grub screw just far enough into the table as needed.


I've heard of the magnet in each corner method and I always wondered why the use of magnets, now I know



I was thinking of going for these Insert Nuts

and these Grub Screws

and also these Rare Earth Magnets


Do those three items look like they'll be suitable? Am I right in assuming that M6 size will be fine for the grub screws?

 

[JJ1]

On looking at the info for the grub screws it says the following; Metric Thread Pitch - M3-0.5mm, M4-0.7mm, M5-0.8mm, M6-1.0mm

There is no mention of the size of the thread pitch on the Insert Nuts though. Is it safe to assume they will have a compatible thread pitch?

 

[Steve Maskery]

Yes. If it's not 1.0mm it's not M6, for example.

 

[JJ1]

That's great. Thanks Steve.

 

[Mcluma]

This may sound different to what they say, but i would have done about 8 screws, but make them from the top. so you can ajust them from the top

you are very concerned about flex, hence the 8 screws

if you do them from the top, you can first line-up the corners, then rest is just done on feeling so that all flex is eliminated

 

[JJ1]

Thanks for the advice. I've bought the threaded inserts this afternoon and I've ordered the grub screws which should be here next week.
I'm certainly planning to do it so that any adjustments can be made from the top. I'm hoping that I won't get too much flex with the steel box section in place, but we'll see and at least I'm prepared for it if it does happen.
I've just finished sanding the new insert plate so as to make it a fraction below the level of the table.

One thing I have discovered is when screwing the threaded inserts into MDF, it's a nightmare as it just pulls the MDF apart. The recommended pilot hole is 8.7mm to 9.1mm, but I had to go up to 9.6mm to make sure the MDF didn't pull apart. Not ideal as it means there isn't much thread being cut into the MDF. I'm hoping some Titebond wood glue or some contact adhesive will keep the insert firmly in place. Also, because the inserts are 13mm long, I've only got 5mm of MDF between the end of the insert and the top of the insert plate and that's going to have a 5 or 6 mm hole cut through it for the grub screw, so there's not going to be an awful lot of wood to keep it firmly seated. Hopefully the glue will suffice.

 

[Steve Maskery]

JJ
I would not use threaded inserts in the way that you have, for precisely the reasons you have found out.
Instead, I would embed an ordinary M6 nut from the rear face. I do this a lot on my jigs, for example here:
http://blip.tv/workshopessentialscom/fi ... ig-3225447
S

 

[JJ1]

Thanks for the tip Steve. I think that's the way I'll have to do it. I've only got about a 12mm shelf for the insert plate to sit on and one thing I overlooked was just how very close the inserts have to be to the corners of the insert plate, meaning absolutely no margin for error and as I've just discovered, so very easy for the MDF to split apart, particularly when so near the edges.
Another advantage of your nut method is that I'll have plenty of depth of wood above the nut, meaning it shouldn't budge at all, especially when glued in place.

Great video by the way and talk about perfect timing . Being new to woodworking and routing in particular, one of the very first projects I'm planning on when my router table is finished, is building a couple of boxes for my router and all the router bits and other bits and pieces. I was hoping to have a go at box joints but had no idea how to go about making the jig or where to start. I do now 8) Many thanks.

 

[Steve Maskery]

All part of the service!

 

[JJ1]