Piloted drills

[ronan]

Does anyone know where piloted drill bits can be bought in the uk ? I have done a google search and looked on fleabay with limited results, i want to open out the oilways in a bike engine (triumph t150 trident common mod) but need a piloted drill to make sure it doesn't break through the sides.

 

[mike 109444]

You might need to get a drill spundown (on a grinder) depending what size between the pilot and the finished size? If it say a finish size of 10mm and pilot needs to be 9mm and because the 9mm will be non cutting (it's only a guide) then stick a 10mm drill in cordless drill and spin down the diameter on a bench grinder. ps yes I know being a Triumph it's imperal but could not think of fracions to enter! it's been a long day : ) Failing the above get a bunch of right (finish size) drills and take to local tool grinders.....

 

[ronan]

Thanks mike , i think the pilot needs to be 13/64's which is approx 5.5mm , i am not quite sure what size i need to drill it out to but 8 or 8.5 mm sounds good, the oilway to the crank was too small especially on cold mornings as the oil was even thicker , this lead to seized big ends and knackered crankshafts,broken rods etc, the factory did change to a much bigger size themselves but my engine is an early one

 

[Robotstar5]

Would a counterbore bit work?

 

[hotrodder]

Annoyingly they seem to go by the title of 'step drill' in the UK which means they get confused with sheet metal step drills when googling. Like counterbores they're most commonly sized for bolts like for example... http://www.phantomdrills.co.uk/ShowProducts.aspx?CatID=534. J&L/MSC Industrial do a range too and while they're not as spendy they're still not cheap and are sized for drilling tapping + clearance holes or clearance + counterbore/countersinking. A 5.5mm pilot is typically 10mm counterbore

Double margin drill is another term to search for but will probably be a lot more expensive than getting a drill ground to suit

 

[Pete.]

Thanks mike , i think the pilot needs to be 13/64's which is approx 5.5mm , i am not quite sure what size i need to drill it out to but 8 or 8.5 mm sounds good, the oilway to the crank was too small especially on cold mornings as the oil was even thicker , this lead to seized big ends and knackered crankshafts,broken rods etc, the factory did change to a much bigger size themselves but my engine is an early one

An 8 or 8.5mm drill will follow a 5.5mm hole perfectly so long as it's not too sharp.

 

[ronan]

Thanks for the suggestions and replies , the drill needs to be pretty long as well as piloted or stepped down, guessing around 7 or 8 inches , so i might buy a long series 8 or 8.5 mm drill and grind the end down as suggested. Gun smiths suppliers in america do them for people relining gun barrels but they are expensive , $120 + .

 

[flash of light]

http://www.drillbitsonline.co.uk/index.php THEY GOT SOME LONG DRILL BITS ALSO you could try making an extention

 

[graffian]

Drill Service in Horley?

 

[flash of light]

ive used them before and been happy with them, last year.

 

[graffian]

DEL-8.00X240 8.00mm 165.0 240.0 118 £5.45

Thats a 240 mm long 8mm drill.
Tell them what your doing, they used to grind one offs in their workshop and some times didn't charge.

Another alternative is a D bit, home made.

 

[mwi]

i use a couple of dewalt extreme drill bits they have a pilot bit on the end not sure about there size range i have them in 10mm to 13mm but very handy for repetitive work. there on fleabay i believe although i just get them straight through dewalt