Why can't you manually re-sharpen a center drill?

by Morning Machinist

Jon House
March 09, 2025

Why can’t you manually re-sharpen a center drill?

Top comments include:

“I’d rather ask why we are using a center drill in a modern machine shop?”
“Its a center drill, meaning it has a precision cut center point. If a drill is not perfectly sharpened right then your .500 hole is now .521 or it could be undersized by .0.025 for a hole size of.475 hope you see why. Enjoy and good luck.”
“You can , but if the point gets too short, you may have to redrill the point depth or the live centre could touch the bottom of the hole , and the part would not run true”
“Re sharpening center drills is fine for manual work but if you use a re sharpened drill in CNC and use the formula to calculate the center drill depth, you most likely won’t have the correct size chamfer around your center drilled hole. You’ll have to adjust your depth accordingly.”
“I do it a lot. Just the tip. On bigger work you don’t have the RPMs so they dull and load up faster.”
“Take one with a broke tip and grind a slot in the middle to use like finger cutters to get another broke tip out of a shaft”
“You can sharpen anything if you have a crack haha we used to reduce the radiuses on particular inserts on disk face cutters to stop chatter..
one thing I was told as an apprentice, learn to sharpen HSS and you’ll always have a job.. and it’s bloody true.”

Reisterstown MD & Lakewood CO | Primus Aerospace | CNC Programmer, CNC Machinist, CNC Operator, Quality Manager, CMM Programmer
Indianapolis, IN | Aerodyn | CNC Programmer, CMM Programmer, CNC Machinist, EDM Machinist
Sebewaing, MI | Sebewaing Tool & Engineering | Remote CNC Programmer, Machinist II

You can view all hireCNC companies/jobs by visiting hirecnc.com/jobs

Top comments include:

“Rig up an extra coolant pipe to the steady position and have it running all the time you are machining. This keeps everything cool and lubricated and washes away any swarf. Also guards against distortion caused by heat build up at the steady position..”
“I use Emory cloth, put the abrasive side on the brass and the cloth side on the part. The cloth holds oil well and seems to be available in most shops"
“Place a 1 inch wide Emery paper around the cylinder ( smooth side around the cylinder, of course) put loose ends together. Close steady rest. Add oil done”
“Brass works fine with heavy parts if you have enough contact. If in doubt make a sleeve to shrink onto the rod”
“The rod OD was 3.5", yes? You can also make a heavy wall slip-fit bushing for over the rod. Add a half collar style clamp AT ONE END and put the steady on the bushing. Way more work, but wont damage the rod. Save and reuse the sleeve for the next job.”
“I take a piece of sling strap and loop it around the shaft and pinch the two ends of the strap in the clamp/ bolt. It will hold the libration much longer and not scar your shaft.”
“Here's the old school way. Take a long strip of emery cloth and double it over so the backing is touching the part and the brass. put some way lube on the contact areas and away you go.”

Top comments include:

“We did that back in the 1980s... Held machining to TENTHS every day... and TIG welded to .001" thick foil stainless steel... every day in our shop. Really not all that hard, if you do it EVERY DAY... and... and.. and measured to one-Quarter wavelength, every day...”
“I hear they have a lot of micro management going on”
“The placement of the dots on the twos is hurting my brain”
“1mm parts on a swiss is easy stuff. I made a part with a .031" turn diameter at 16xD last year, +/- .0005" OD. I gave my 10mm STAR a pat on the back after that one. The welding is crazy on this though!”
“Needs deburring”

⁉️ Haas gurus, what am I doing wrong here?

⁉️I can’t seem to power tap on my 2006 Haas SL-30…

⁉️ Any suggestion for a good coolant for a lathe that doesn’t peel the paint?