Drilling metal - speed charts vs reality

[Ultradog MN]

Judging by that chart I can't drill much of anything.

 

[RJSakowski]

The above chart appears to have originated in Wood Magazine. I wouldn't look to a woodworking magazine for advice on how to work metal.

 

[RJSakowski]

There is a tremendous wealth of useful and valuable information of the internet but there is a lot of crap as well. "trust but verify" are words to live by.

 

[woodchucker]

Judging by that chart I can't drill much of anything.

well damn, your problem might be that your lathe is talking in German.
and well maybe RPM is in Metric .

We'll have to do a lobotomy and remove it's head for reprogramming.

All kidding aside, I think you would be fine... We have to remove the chart to all feel better.

 

[ARC-170]

In the metal machine shop class at my former employer we used this:


I've been using it for my metal lathe and mill and it works just fine.

 

[MrWhoopee]

In the metal machine shop class at my former employer we used this:
View attachment 404201

I've been using it for my metal lathe and mill and it works just fine.

I LIKE that chart. Simple and easy to read. Those are the numbers I was taught in school, 80 SF/M for mild steel is the only one I carry in my head, I adjust from that for other materials. CSx4/dia. is a simplification of the formula that can be done quickly without a calculator.

These calculations do not need to be ultra precise, they just get you a safe place to start that won't toast your tool. Optimizing for maximum metal removal rates is generally left to CNC programmers in production settings. The boss would rather see you making chips than punching buttons on your calculator.

 

[vocatexas]

Mr. Whoopee, DeWalt makes metal drill bits with a bullet point on the end. I've used them for years in my hand drills. The bullet point keeps the bit from walking, especially on a curved surface. They do cost a bit more than a standard drill bit, however.

 

[MrWhoopee]

Mr. Whoopee, DeWalt makes metal drill bits with a bullet point on the end. I've used them for years in my hand drills. The bullet point keeps the bit from walking, especially on a curved surface. They do cost a bit more than a standard drill bit, however.

I can see the advantage. How do you re-sharpen them?

 

[jwmay]

Being no expert, I can only qualify my generally useful suggestion with an anecdotal bit of data. The larger the bit, the slower the rpm. The anecdotal data is my 8 year old, nearly full index of drill bits. Running small bits too slow is not nearly as bad as running any size too fast. Err on the slow side. Ymmv. I'd love to have been able to give you an rpm range, but I've literally forgotten. It's all by pulley changes, which I remember as either "slow" or "mid range". I never go beyond mid range.

 

[tjb]

In the metal machine shop class at my former employer we used this:
View attachment 404201

I've been using it for my metal lathe and mill and it works just fine.

Could you post that chart as an attachment so we can download it?