Cheers derek yes far wiser now  it's only the second time i've used it i'll keep practising.

P J

derek willis wrote (see)

 The larger the bit the slower the cutter will run,

 No , sorry but no. The cutter will run at the rpm set but the greater the diameter of the cutting edge the faster the effective speed will be.

 also the slower the feed speed the better the finish, but not too slow as to burn the timber, only costant use will determine this for you, have fun.

Absolutely correct.

This issue has always been a difficult one to get to grips with and only gets worse when multiplied by two or three or even six cutting edges over  a set diameter combined with the RPM. Please dont ask me to try and calculate all the speeds and feed rate ... Ive had a hard day.

Ps. The hard day started with a very early awakening that resulted in an early post!

Rob is dead right on this. Just to make his head hurt even more......cutting speeds for drilling in steel are often given in terms of "feet per minute", rather than RPM. This requires you to take the diameter of the drill bit and apply C=pi D, multiply this by the RPM, do a metric to imperial conversion, then work out which belt to take off which pulley and replace on which other one, according to a table which varies with the thickness of the material being drilled. The "feet per minute" measurement is the speed of a spot on the outside edge of the cutting edge of the drill bit.

The usual response is to ignore all that, have the machine set to a slow speed, and depress the drill harder or softer depending on its response to the material it is cutting. Pragmatism wins over arithmatic!

Mike 

Not Fair! it's hurting enough already and by morning and the bottle of Armagnac is somewhat depleted, will probably be more so..have a heart!

Drill bits have the propensity to break if ill treated then become the model of obstinance when trying to remove them from the workpiece.

Need big , powerful painkillers ..now

Paul,

I would only ever allow for shrinkage. Timber for internal use will rarely if ever expand or swell when brought indoors.

It's hard to imagine how we got here, but one of the greatest disasters in woodworkering was the development of biscuits for jointing longgrain to longrain boards. Like many modern concepts, before they were invented we didn't need them so I agree with Ben Plewes. Why fall into that pit. You must remember that not many machine manufacturers are woodworkers. They want to make something that sells. Biscuits are more expensive than digestives and sometimes modern methods are hard to stomach. The same goes for loose tonges, dowel joints and so on.

Sorry I'm late in on this one, but I recommend you leave the biscuits alone and just rely on the glue. It worked for centuries and we still have panels glued up two-hundred years ago.

Paul Sellers 

Rob,

it is ahard and fast rule that the larger the bit the slower you run it, no more to be said.

derek. 

Paul Sellers welcome but you have got to be joking about the time 5.26am I hadn't finished work then. I will keep using the biscuits for now as loose tonges i will build up to rub joints. Conclusion; ''Wisdom from others but practise makes perfect''

THANKS ONE AND ALL ! P J

P S I do need to read this again.