Pocket holes and MDF

[dlowry_uk]

I've just bought a Kreg Pocket Rocket kit to make MDF face frames and doors for a built-in. Tried it out this morning on scrap 18mm MDF, and haven't been able to avoid splitting, both in end-to-end and right-angle joins. I'm using coarse Kreg screws as recommended for MDF. Part of the problem is judging how far to drive the screws - its very easy to overdrive slightly and thats probably when the splitting occurs.

Anyone had similar problems, or tips to avoid it? Another possibility is that the scrap had been lying around for a while in an outhouse, where it may have picked up some moisture.

Drew

 

[philpolish]

hi try using a low powered drill or do them up by hand until you get the feel for it. I use a little 3.6 metabo with a long reach drill bit you can feel the screw grip right at the end . I take it you are doing the screw up to hard.
cheers Phil.

 

[jonny boy]

I know it seems a little time consuming but when driving any screws into mdf inthe endgrain or near the edge, I alway's drill a small pilot hole first and this usually solves the problem. I'm afraid while mdf is a very versatile board material, it is very poor at accepting screw fixings of any type.
cheers,
jon.

 

[jasonB]

Just turn the torque setting on your cordless to a low setting. Quality of the MDF will also affect how it may split.

End to end is not a good idea with MDF as any screw into the edge will tend to split the board. Pilots should not be needed as the kreg screws have a selfdrilling point.

If the hole part is splitting its due to overtightening but is easily done.

Jason

 

[Anonymous]

This is a general problem with MDF. I now use only Moisture Resistant MDF (the green stuff). It's a little more expensive, but as well as the obvious advantages with regard to moisture, it works better, takes screws better, and most importantly finishes better.

Well worth the extra cost.

Cheers
Brad

 

[Anonymous]

This is a general problem with MDF. I now use only Moisture Resistant MDF (the green stuff). It's a little more expensive, but as well as the obvious advantages with regard to moisture, it works better, takes screws better, and most importantly finishes better.

Well worth the extra cost.

Cheers
Brad

Hooray, another one has seen the light, i really dislike the hairy MDF.

 

[Anonymous]

Hi,

Just to add weight to the MR MDF argument, I have be making some wardrobes today using a combination of Pocket screws and biscuits and it didn't occur to me that there might be splits. I cant remember who it was that recommended it but I have been using it for a while, it really is so much better than ordinary MDF, especially that sold by the sheds. As to cost, the last purchase that I made 18mm sheets cost 19.98 + vat which is a "trade" price, compared to 17.57 + vat for ordinary MDF.

Doesn't solve your problem I'm afraid but it might help next time.


Saint

 

[David C]

Pocket screws were thought up in the days of solid timber.

Mdf is easily split.

David

 

[dlowry_uk]

Luckily, I haven't bought the MDF for the job yet - I was experimenting on some scrap as I hadn't used pocket screws before. I'll try to source MR MDF locally.

Thanks for the help
Drew

 

[jonny boy]

We alway's have srew and industrial supply reps comming into our company and recently we had one arrive with what he claimed was the best woodscrew available. He handed me several of them and said that I would be able to put one in mdf only half inch in from the end corner and would still not split it. Before it was attempted I knew that this was rubbish and said so. He gave me a smug look as though he knew something that I diddn't and said go on then, the screw did exactly the same as any would and split it before it even got half way in and it was my turn for smug looks then.
It is in my opinion, impossible to insert any type of screw into end grain of mdf without splitting unless it's piloted. Even the pocket hole screw's with a drilling tip just dont give the amount of clearance needed.
cheers,
jon.

 

[Anonymous]

As to cost, the last purchase that I made 18mm sheets cost 19.98 + vat which is a "trade" price, compared to 17.57 + vat for ordinary MDF.

You should be able to do better than that. I pay around £14.50 for MR MDF as against £12.00 for fluffy MDF. Look for a specialist board merchent in your area rather than a general timber merchent.

Cheers
Brad

 

[Anonymous]

Pocket screws were thought up in the days of solid timber.

Are you suggesting that the days of solid timber are over, David? :wink:

I somehow can't see you writing a book on sharpening biscuit joiner blades! :lol:

Cheers
Brad

 

[Anonymous]

As to cost, the last purchase that I made 18mm sheets cost 19.98 + vat which is a "trade" price, compared to 17.57 + vat for ordinary MDF.

You should be able to do better than that. I pay around £14.50 for MR MDF as against £12.00 for fluffy MDF. Look for a specialist board merchent in your area rather than a general timber merchent.

Cheers
Brad

Is that for a named board, kronaspan, medite etc or is it chinese, if you have a sample of both leave some water on them for half an hour and see the difference.

 

[Anonymous]

Is that for a named board, kronaspan, medite etc or is it chinese, if you have a sample of both leave some water on them for half an hour and see the difference.

Finsa - Spanish, I think.

Seems OK to me.

Cheers
Brad

 

[Anonymous]

Finsa is good, what I would call a named brand, some MR MDF is little better than the hairy stuff.

 

[David C]

Brad,

What a nice idea!

Biscuit jointer sawblades need to be sharp too........................................

and biscuits are very useful in the modern world.

David

 

[Scrit]

Anyone had similar problems, or tips to avoid it? Another possibility is that the scrap had been lying around for a while in an outhouse, where it may have picked up some moisture.

Yes - tips to avoid it? Don't use pocket holes in MDF....... The Kreg jig was really developed to be used with plywood and has found a niche in MFC as well but I don't think it works brilliantly in MDF. Dowels or biscuits are a better choice.

I'll also second (third? fourth?) the advice to go for MR-MDF and buy a named European board, e.g. Kronospan, Caber, Egger, Finsa, Medite, Sonae, etc. There are a couple of alternatives to MR-MDF, though. You might be offered "deep rout" MDF - a grade of MDF which is denser and was originally designed for edge profiled work on CNC routers, also I've found that Caber standard MDF is darker and denser than many others and will machine to a crisper edge profile than standard MDF, the downside is it generates loads of very fine dust.

Biscuit jointer sawblades need to be sharp too........................................

Best way to achieve that is to use a TCT replaceable tip cutter....... No need for nasty, messy hand sharpening

and biscuits are very useful in the modern world.

Especially with elevenses :wink:

Scrit

 

[Martin Brown]

We are at Kreg this week asnd I asked Joel at Kreg his thoughts. These may not answer the thread but will help I hope.

1 Keep away from the edge
2 Use better MDF
3 Always glue

Hope this helps.

Martin

 

[Jezmaster]

I don't own a pocket jig, so i just do but joints, and use the MDF screws that screw fix sell, pilot, and insert. no spilt out, or bulges. in 18mm.
compaerd to nomal chipboard screws, etc.

pick my sheets up for £13 ish, and it isnt the furry stuff tht B&Q sells.