U DRILLS ARE DRILLING TOOL WITH CARBIDE INSERTS WHICH CAN CHANGE EASILY AND COST ECONOMICAL A NORMAL U DRILL LOOK LIKE THIS.
To understand basic of hole making tools are those cutting tools which are used to make drill in any work piece weather its wood, aluminium, brass, steel, cast iron , titanium etc.
There are few types of drills in the market but only few are most commonly used because of economic cost and easy usage and can be used on both turning and milling machine.
They are SPMG and WCMX type U drills comes in Square and Trigon Shape inserts from Drilling range LXD 2 to LXD5 , 12 mm to 60 mm now 8 mm to 12 mm small drills are also becoming common if they are successful they can be very cost effective for these diameters drills.
Why u drills are Economic and cost effective.
Carbide Drills are very costly compare to HSS , its 10 Times higher than HSS so here comes the indexable drill which comes with cheap carbide insert Square with 4 edges and Trigon with 3 edges and cost of inserts somewhere Rs.120 To Rs. 300.
2. No need of Center Mark (Center Hole)
As u drills can plunge directly into work piece so you don’t need centre drill mark it saves a turret space in lathe and extra time in both the machines.
3. Drilling Capacity
Every drill comes with drilling capacity Known as LXD(LENGTH BY DIAMETER) LD2,LD3,LD4,LD5,LD6 IF a 20 mm LD4 drill it can drill till 80 mm and same LD3 means drill upto 60 MM so when you choose u drill must keep your drilling range in machine.
Drill has +- tolerance the more LXD has more the tolerance if you choose a LXD5 U drill there are chances of .2 size of drill size the smaller the diameter the less is tolerance so its not a good choice to take a LXD5 drill when you require LXD3.
5. Through Coolant
U drills are through coolant as external coolant cannot reach in depth so it’s always better to choose drill with coolant holes only as coolant can reach inside and save it from burning and help better chip evacuation