Steel contamination

[TortugaTonta]

I hope this is the correct place to direct this question and I am sorry if it is not.


I build steel bicycles and one of the problems we have is mitering the thin wall tubing. I would like to try to use abrasive diamond cutters to miter the tubes as opposed to a metal hole saw to avoid chatter and get a more precise cut. I was told by a machinist that this is a bad idea because the steel is "carbon hungry" and will "absorb" carbon from the diamond cutter and weaken the area when it is then welded to the adjacent tube.

Is this a legitament concern?

Thanks in advance for any help, Ted

 

[btrueblood]

As long as the steel isn't getting red hot or melting during cutting, carbon pickup shouldn't be much of an issue. I.e. use a good coolant when cutting. What steel are you using, presumably a medium-carbon Cr/Mo (4140 or similar)?

 

[TortugaTonta]

First, Thanks for the quick response.

I use a good bit of 4130 with wall thickness of 0.024,0.035 and 0.049. These aren't too bad but some of the specialty alloys like reynolds 853 at 0.7 and 0.8mm, they are soo tough that the teeth simply break off of a bimetal hole saw. I recently tried an annular cutter but the teeth seem too agressive for the thin wall material I am using, it actually "snagged" the tube, breaking the cutter and bending up the tube.

My other concern is getting a precise cut. If the miters are not precise the tig welding becomes difficult

Anyway thanks for the tip, I will give one a whirl tomorrow.

 

[EdStainless]

Run it wet and you should be fine. can you get CBN instead of diamond? That would reduce the risk further.

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Plymouth Tube

 

[Metalguy]

Why are you welding a steel like 853 when it was designed to be low-temperature brazed? Didn't you have to braze a test frame and ship it to Reynolds for testing before they'd sell you tubing for production?

That's how it was when Reynolds went from 531 to 853 years ago. They wanted to make sure you could braze it w/o overheating it and killing the strength in the HAZs.

Gold is for the mistress - silver for the maid
Copper for the craftsman cunning in his trade.
"Good!" said the Baron, sitting in his hall
But iron - cold iron is the master of them all.
Rudyard Kipling