Advice on Insert/U/Spade drills...

[hotponyshoes]

Hi all,
I often have need to put large holes into stainless steel and aluminum,
I have a boring head for my mill and a boring bar for the lathe.

To make a hole big enough for the boring bar to get into I have been using HSS jobber drills to take it out a bit at a time, For the boring head I have been plunging a milling cutter through first.

I get through a lot of drill bits doing this so I was thinking about getting some of the 'U' drills that take the replaceable inserts and would let me pump coolant into the hole at the same time.

I am really after some advice on: A - is this a cost-effective way of drilling or should I just invest in a set of colbolt drills,
B - How do you mount the indexable drill bits?
The lathe has a no.3 Morse Taper tail stock and the mill has a 3MT in the head stock.

The only holders I have seen (I am looking on ebay!) are BT40.

Also, I presume it will be simple enough to feed coolant when using them on the lathe (as the bit will remain still) but what about the mill?
There is coolant but not through the head. Do you get (or make) some sort of rotary adaptor or will the fact that the drill is vertical and coolant should fill the hole anyway be enough?

Many thanks!!

[star-turn]

cant speak for the mill, but really a manual lathe will not have the speed/power to get the best out of u-drills.

you can get carbide spade drill ( Allied Max Cut ) they have many holders inc morse taper - but you may find the price prohibative.

ST

[Ginger_Ninja54]

as previous...

a manual machine wouldnt have the power to run a u-drill fast enough to make it cut correctly.
also, the through coolant would need to be fed at about 8bar!


have you thought/tried solid carbide drills?

can you get WNT?
their 11-734 and 11-739 ranges are very good, and not much difference in price to a good HSS-E Cobalt drill.

[gridley51]

It would be helpful if you let us know the dia and depth you are drilling.Depending on depth through coolant may not be needed with a u drill in a lathe,whether your lathe is rigid enough is another question.
Again depending on depth a spade drill will probably do.I use them a lot on manual machines.
Please give us the hole sizes and the make and model of your lathe and mill.It all helps.
Mark
www.ems-fife.co.uk