I am trying to make a  4tpi 0.850” dia worm gear, my lathe is not big enough to handle the forces generated, so I thought I could thread mill on my CNC mill using the fourth axis rotary table.
Problem is how do I control A axis and X axis independently while on the same line of code i.e.?
G1 A360 F30 X1.00 F6
Or is there another G code command to cover this situation? I have looked through G codes but can’t find one that suits.

Thanks

Mike

Hi Mike,
You can't use 2 feed rates on the same line. IIRC it will just use the last one. You might want to have a look at Gearotic to see if it will generate code for the gear you are trying to make.

Mike

my lathe is not big enough to handle the forces generated

What you may want to try is using alternate flank cutting for the 4tpi. See page 44 of Threading on The Lathe - Mach3 Turn  which can be found in Member's Doc. I fooled with this some time ago and was able to do some threading I never thought possible with the wee little Sherline Lathe.

RICH

Thanks for your suggestions however does not solve the problem, I have found a way of producing a very coarse thread by using G0 rapid code and reducing kernel speed to 100 so X and A axis turn together at a reasonable feed to run a milling cutter. A four start worm can then be made buy making an angled cutter to suit the pitch.
Industry mill worms using a rotary axis so there must be a way of controlling the two axis independently?

Mike

You can’t control a rotary and linear axis independently in the same block nor would you want to. For the example:
G1 A360 F30 X1.00 F6
At 30 deg/min it would take 12 min for the A to make one rev while at six in/min the X would move one inch in 10 sec. They won't come out even.
The problem is the different units used for each, (deg/min vs. in/min).

Fortunately Mach has a feature to resolve this prob. Use the in/min feed that you want to cut and then enter the radius of the work in the ‘Rotation Radius’ block on the ‘Settings’ page. Mach will use this radius to calc the actual rotary and axial feeds to achieve your required resultant feed rate.
Al

Alanz

Brilliant! it works a treat, by altering the A axis dia and X length you can create desired pitch of worm. CNC capabilities always impress me.
Thank you very much for this valuable information.

Regards
Mike

Glad to help

hi there im new to this hobby im using mach3 cnc milling and would like to cut a worm gear using 4th axis how do i go about setting this or the codes please help
Thankx

hi there im new to this hobby im using mach3 cnc milling and would like to cut a worm gear using 4th axis how do i go about setting this or the codes please help
Thankx

Hi Khaled,

Welcome to the forum.

Whilst machining a worm gear using a milling machine and 4th axis sounds like a simple enough task, as a beginner you may find it difficult to set up the necessary parameters within Mach3 (as explained by Al in the above post).

Not wishing to deter you from the exercise but I think that using a screw cutting lathe would be a whole lot easier.

Tweakie.

nb. Please don't make multiple posts on the same subject, it is counter productive - thanks.

Hi thankx I do have a lathe but its too small so I got to do it on milling machine please someone help with just an example even to get me on track