# Geared Head cnc



## nighthawkFmobil (Apr 30, 2021)

I'm looking for feedback on geared head cnc builds. What kind of longevity are you looking at with this kind of set up? Aside from the obvious speed issues what are the drawbacks? What are the pros? Any kind of info is much appreciated. I recently bought a pm940v but I can still change my mind if I choose to. I'm going to run it manual for a while and I really just want a good all around mill. If it ends up being a hassle struggling with the low speed power(hoping the dual pulley makes it tolerable) I plan to upgrade the motor and vfd. 

I've noticed a lot more people than I thought have converted geared head machine to cnc so I'm interested. The cost saving of a 940m vs a 940v is nice especially when adding pdf but it seems like quite a gamble if I did in  fact want to convert to a belt drive in the future. It's all about the learning experience for me at this point.


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## spumco (Apr 30, 2021)

Can of worms, whatever the answer.

The best way I could answer would be to pose a question: If you had unlimited funds, what single mill would you buy for use in your home shop?

Do you see yourself with a high-speed, low-drag CNC machine that can do all sorts of sexy small stuff?
Or do you see yourself doing one-off pieces that require way more time spent fixturing than CAD/CAM?

Where I'm going with this is that most folks I know - in job shops or as a hobby - want both.  A CNC mill and a manual mill.  And if you've only got room/money for one then you have to decide based on what stuff you want to make.  And that will determine the type of head/drive system is appropriate for your usual applications.

A slow, geared head mill can still use small cutters, but it'll be _really _slow in the feed rate.   A higher-speed belt drive won't be able to do really slow or high-torque RPM stuff (big drills, big taps, big facemills in steel, etc).  But it won't take you a week to engrave something with a 1/32" ball end mill.

And if you get a belt-drive 940 and convert it to CNC and get 8kRPM out of it... will you have the axis travel speeds to keep up with the spindle?  I'm not sure I'd want to push a dovetail mill much faster than 100ipm in the cut (rapids are different).

If you are going to CNC the PM940, don't buy the PDF option.  And make sure the the V model has a VFD that can be controlled externally (by the CNC controller).  Besides, you can always get the M, pitch the motor, and get a VFD and 3phase motor for it so you aren't doing as many gear changes.

If you want a few examples of manual-type mill conversions, youtube is your friend.  I'm not talking about G0704 or PM940 stuff, but things like converted Bridgeports or similar.  Robin Renzetti has a few videos which feature his mill; not sure the actual brand but it looks like a Trak.  These are belt-drive with hi-lo gears.  They are available in manual or 2/3 axis CNC.  While not fast, they are about the most flexible CNC mill's I've ever seen.

I have a CNC mill...and I want a manual mill, too.  If I only had a manual mill, I'd still want a CNC mill to go with it.

If I were in your shoes I'd get a geared-head PM940 with PDF, put a VFD on it and then _leave it alone_. If I had to have a CNC machine, I'd get a used CNC mill, upgrade the electronics/control and not convert anything mechanical.

I'll wrap it up so you can go deep-dive some more research.


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## macardoso (Apr 30, 2021)

I only have a CNC and would love a good manual mill with some rigidity. Would be much faster to setup and use than the CNC for 80% of what I do.


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