Need Help!- Knurling 4130 Tube

[racecraft]

I am trying to diamond knurl Military Grade 4130 thin wall tubing.
The Sizes are: 1.250" x .058" wall thickness
1.500" x .058" wall thickness

I have tried using a dual wheel bump knurling tool with plenty of Hangsterfer's cutting oil. My results are not working.

The material is so tough that the force you must put on the piece of tube in order to "bite" into the material makes the tubing flex off of the live center. I also end up with about a quadruple knurl.

Any help here? Any suggestions on tooling that would work better for this?

Thanks, Racecraft

[newc]

Try cocking your knurl rollers so they are more or less cutting on the front edge, rather than trying to shove the entire width into the piece. Then feed back and forth to get the width you need. Follow up with a little wire brushing to get rid of flaking, and you will end up with micrometer grade knurl.

[sambo67]

you should try a c-clamp style knurling tool

[CNC_Simon]

You could try putting a filler piece in the tube to stop it deforming while you knurl it.

[msomerville]

I agree with CNC simon with a .058 wall that piece is going to push away on you all day long.

[racecraft]

I will try all of these ideas. They all sound great.

How bout a good estimate on speed and feed for this operation? The knurls are 3/4" diameter and are HSS.

Any suggestions?

Thanks!

[newc]

610 RPM
0.006 ipr infeed to depth (probably about 0.035)
0.012-0.015 feed towards chuck - don't dwell

You can repeat a time or two if you need to, in order to raise the knurl to a good height, but don't go over it too many times, it will start to tear.

Again, use the knurl rollers more as cutting tools than forming tools.
4130 should knurl up real nice.
Regards,
Newc

[racecraft]

newc,

I think im misunderstanding the correct formula on what knurling wheels to use.

What TPI knurls should i be using for 1.250" material and for 1.500" material.

The problem i think i am also running into is that i can not turn the material to a specified diameter before i knurl it. So i have to try and get a knurl that has a TPI that will get me "close enough".

Just not sure how to calculate to get that.

Hope to hear from you soon.

Thanks, racecraft

[newc]

racecraft:
Don't worry about it. There are formulas for all that crap, but just use what you have lying around. Turning to a precise diameter first is not necessary, just push the knurls in until you get a good height. They'll track OK, trust me. Again, turn the knurl holder so just the edges of the rollers are hitting the stock - doing more of a cutting action than a "knurling" action. CNC Simon has a good idea of putting in a plug to keep the tubing from collapsing, especially where you chuck it.
Regards,
Newc

[racecraft]

sounds good, i will try this first thing tmw, and post my results.

thanks for the help guys.