1945 Craftsman 101.07403 CNC Conversion

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14 Oct 2018 23:36 - 15 Oct 2018 03:20 #118808 by SnailPowered
Hello, I am looking to convert my old 1945 Craftsman lathe into a CNC lathe. I am a CNC Machinist professionally and have access to the machines to make the parts I need like bearing supports and a new tool post mount to replace the compound. I am trying to convert this to CNC without permanently altering the lathe itself. The cross slide will have a new bearing support where the current handle is and the servo/stepper will be bolted to the other side where the taper attachment would have been. I believe I can replace the apron with a plate that bolts to the nut on a ball screw. The bearing supports currently bolt on so my plan is to build replacements to accept the ball screw bearings. I plan to have the stepper/servo mounted on the head stock side of the lathe. I have been looking at the closed loop stepper options on Amazon for prices, even though I'm sure there are better places to purchase my components. They come with the driver so I think all I need is a power supply and a way to connect them to my computer.

I was an Explosive Ordnance Disposal (EOD) technician and I have had some training in electronics, including soldering to PCBs. I am sure that I have the ability to assemble the required equipment but I'm not currently sure how to size all of the components and ensure that I'm purchasing what I need and not something similar to what I need. I look forward to sharing my project with you all!

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Last edit: 15 Oct 2018 03:20 by SnailPowered.

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15 Oct 2018 02:26 #118812 by OT-CNC
That could be an interesting project. I would look first at modifying the head stock drive system so you have reliable spindle speed for threading. Some place to mount an encoder and switch out the step pulleys with timing belt/pulleys. You may want a bigger motor and VFD for low end torque.
Maybe you can get away with the stock setup. Does the belt slip under load?
I would also look at mounting zero backlash ball screws and a way to protect them with proper covers.
Add some DMM servos (400w or 750W?) 10 inch swing machine??
And add some type of auto lube system to the saddle/ways, flood coolant and a way to keep the spray off the wall,ceiling and body (guards/enclosure)

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15 Oct 2018 02:51 #118814 by SnailPowered
Yeah, I don't have the money to do a VFD or convert the spindle drive initially. Once I remove the gears I could definitely attach one of the gears onto an encoder and attach it to the spindle gear that currently drives the lead screw. That would allow me to thread and the factory spindle setup actually gives me a wide selection of spindle speeds to work with until I can afford a good VFD setup.

My original post mentioned my ideas for replacing the factory lead screws with ball screws. I have never had the spindle belt slip even during knurling so I'm pretty confident in the ability of a V belt to handle what this lathe's bed can handle. It isn't going to produce parts like the Mori Seiki SL-15MC I used to run, but I think it can work very well for simple projects that I have in mind. Here are some more pictures with my idea of what I will change for the conversion.

Speaking of the drive belt, that adjustable link belt from Harbor Freight that I'm using is absolutely fantastic compared to a normal drive belt. I haven't had any slip with it at all either. It doesn't build up vibrations like the old conventional belt did. It is also much quieter.

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15 Oct 2018 03:23 #118816 by OT-CNC
Yes, the fenner type twist link drive belts work pretty good at reducing vibes.
You will want to mount the spindle encoder 1:1 ideally directly to the spindle.
Looking at the images, there may not be much spare room inside the X saddle for a ball nut with mount. They can get quite large in comparison to a brass nut just be aware of that.
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15 Oct 2018 03:34 #118817 by SnailPowered
I may have the proper gear to make the 1:1 off that gear. I have a full stack of drive gears that was originally for a wide variety of threads and carriage feeds.

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16 Oct 2018 13:34 #118877 by andypugh
The simple solution to the spindle encoder would be a couple of gear tooth detectors sensing the spindle bull gear.

A third one would be needed for index, sensing a keyway or something.

www.pico-systems.com/bridge_spindle.html

I converted a lathe slightly newer than yours. But deliberately over-specced things just for fun.
bodgesoc.blogspot.com/2015/08/holbrook1.html (and following)
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17 Oct 2018 02:45 #118918 by SnailPowered
I am definitely going to read through that thread, thanks! Today has been been busy but I will have more time the rest of the week.

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22 Oct 2018 03:24 #119189 by SnailPowered
That one is definitely quite a bit beyond what I'm working with. I wish I could do all that! Maybe someday, but for now I will be taking baby steps. I think I could use the gear on the spindle of my lathe with a similar setup to what they did on that mill. Thanks for sharing!

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22 Oct 2018 04:10 - 22 Oct 2018 04:21 #119191 by SnailPowered
From what I understand, as far as the electronics side goes, I think that I basically need a computer (hoping to use the one I'm on) and the following items.

A Breakout Board

Power Supply

Z-Axis Stepper

X-Axis Stepper

Is there something that I'm missing? Will that PSU be enough for those two steppers and possibly a third. Obviously I wouldn't be able to do any threading at this point. Thank you for looking and helping me with my project!
Last edit: 22 Oct 2018 04:21 by SnailPowered.

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22 Oct 2018 10:07 #119194 by andypugh

SnailPowered wrote: Maybe someday, but for now I will be taking baby steps.


My first conversion was nothing like as elaborate as the Holbrook, that was a conversion as a project of it's own to see if I could do one that looked "factory"

My first conversion was a lot less elaborate, and done a lot more cheaply. I didn't really document it very well (this was before I became a Social Media narcissist) but there are some pictures here, though it was mainly documenting making tapered Gibbs: photos.app.goo.gl/nwM9Ze59j3zi5TB77

Lessons-learned from that conversion include having the leadscrew bearing further behind the headstock face to make room for a leadscrew cover and that reflective optos on Vero board covered in epoxy putty are not as good as off-the-shelf inductive proximity switches embedded in drilled holes out of the way of chips and contamination. I can't find a good photo of an installation, but if you look at this photo: photos.app.goo.gl/fWnVETvw7Njy5M6Z6 the hole to the left of the ball-nut block is threaded M8x1 for a proximity sensor. The sensor detects two shallow holes drilled in the cross-slide at each extent of travel. There is a very similar arrangement for the saddle, you can _just_ make out the target in this photo, in the side of the slideway near the front of the tailstock: photos.app.goo.gl/gB5zjg3uaZPBKCtQ8 It is a shallow hole, in this case plugged with a Delrin disc to keep it from getting contaminated with swarf. (don't use an aluminium plug, the sensors can still "see" aluminium when surrounded by iron).
If embedding in the machine castings then you need the shielded style. like this: www.ebay.co.uk/itm/123391003334 with the threads all the way to the end. The type with the shorter threads are more sensitive, but permanently detect the metal they are embedded in, which is no use. You probably want a short detection distance (that one is 1mm) for a sliding-past detection.
NPN can be interfaced to the parport as they act as a switch-to-ground, though they need at least 6V as a power supply to operate. PNP won't (easily) work with a parport as they source V+ when activated. Of course, if you use a BoB rather than wiring direct to a parport this probably is less of a concern.
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