Drilling Holes In 3mm Galvanized Steel.

Johns1980

Member
I'm thinking hole sizes from around 8mm - 25mm. I have a decent quality, newish, floor standing pillar drill. What are the best type of drill bits to use and technique of drilling, speed to run bits, will steel heat up, deform? Cutting fluid type, using it, better to drill smaller hole first, then larger?
" drill smaller hole first, then larger ", speed to drill at? This in relation to different drill sizes?
Will I get a nice clean hole?
I'm drilling a 300 x 300mm sheet.
Any help advice appreciated.
Cheers.
 
I'm thinking hole sizes from around 8mm - 25mm. I have a decent quality, newish, floor standing pillar drill. What are the best type of drill bits to use and technique of drilling, speed to run bits, will steel heat up, deform? Cutting fluid type, using it, better to drill smaller hole first, then larger?
" drill smaller hole first, then larger ", speed to drill at? This in relation to different drill sizes?
Will I get a nice clean hole?
I'm drilling a 300 x 300mm sheet.
Any help advice appreciated.
Cheers.
I think my first choice would be a decent step drill.
 
The first formula I was taught when I started my City and Guilds was the cutting speed calculation; n=1000s/pi*d , stayed with me!

Any way, for anything under 5 mm steel I would set the pillar drill at high speed, 2000 rpm or so. 25 mm you should be taking the speed right down, something around 400 rpm and use plenty of oil. This is for a standard HSS drill bit.

https://www.sserc.org.uk/wp-content/uploads/2011/12/drill-speed-chart.pdf
 
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