[LeeWay]

Well I had such good luck building a mill using good parts with 80/20, that I have decided to go the same route for a small production lathe.
I did convert a 7-12, but with less than stellar results. It is the backlash, general flexing, lack of motor power that directed me to just build new, rather than try to upgrade the 7-12.
It is a much better manual lathe than it is on cnc with stock parts.

Anyway, I have many of the parts already. Some parts are exactly the same as on my mill. The 3060 80/20 base, the THK rails, I will be using the spindle head from the 7/12, much the same way I used the X2 spindle head on the mill.
I will be using a treadmill motor on this but not quite as strong as the one on the mill.

I will be using SDPI timing belts and gears and the existing 270 oz motors and Gecko 201's with a 48 VDC PS.


This will be the first time I fully design something using CAD drawings.
This will be my 4th machine build or my 5th if you count the conversion, but I haven't completely finished the plasma yet, so 4th is about right.
Here is what I have so far.

I will be using 5/8" ball screws and nuts like I used on my router from Mcmaster Carr. I will preload these though.


Several areas I am not sure about yet. Gang tooling is one. I have a cast iron T-slot table from an X Y table that I want to use for mount tooling. I don't need a lot of different tooling on here to start with.
I want to cover the head and part of the motor and include the controls in it. This will also get a sliding lexan cover that has to slide closed before I could start it manually. I do want it eventually under Mach control for the spindle.

While it turned out not needed on my mill, I do intend to fill these extrusions with concrete or hydraulic cement and lead shot.
That should give it a little more mass.

Let me know your thoughts and suggestions.
Thanks.

[sergizmo]

Looks good Lee.

Gang tooling is the way to go. Simple and fast.

Do you plan to do any threading on this lathe? If yes, how will you do so?

[LeeWay]

Thanks Serge.
This is a semi production machine and will mainly just turn 9/16" brass rod. I would like to do some threading eventually. I did some on the mini lathe using gears, but although they worked, they were not pro quality.

I think even with the mini lathe spindle, this build will be pretty rigid for a small bench top. I have proven to myself the concept works with my mill.

It ain't gonna have to weigh as much as a house to get good results in small brass rod. It will have to be faster though. Just a little.
I should be able to get near 6000 RPM with this motor I have. It goes in reverse as well, so I will use a board from cnc4pc for that. I also have an indexer thingy i bought for it, so threading should be fairly easy, should I choose to do it.

I will still have this little lathe converted back to manual if all else fails. I have another spindle head that I may use. Just buy the spindle and new bearings from LMS.

I have woked on the drawing a little more, but don't have time to get them ready to post.
I will do that in the AM.

[digits]

It's looking good so far Lee!

I really am looking forward to seeing how you get on, as I quite fancy an ally-extrusion based lathe myself

Good luck!

[Todd Price]

Whoa dude slow down..... I'm still trying to keep up with your mill build.....lol Keep up the good work.

Todd

[sergizmo]

It should be plenty strong enough. Especially if you use rails as big as the ones on your mill. Those were beefy for a small machine. Like you say, turning 9/16 brass rod will be cake.

What travels are you going for?

Are there any concerns about sustained 6,000 RPM with the stock spindle bearings?

No need for "If all else fails". You did the mill, a lathe should be no problem. Just 2 axis instead of three. Stationary spindle and motor and fewer parts overall.

I look forward to the build.

Serge

[digits]

What sort of chuck are you planning Lee, and do you know that it's good for 6,000 rpm? I can't imagine there's any good place to have to have a surgeon remove a chuck jaw from

[LeeWay]

Thanks, Guys.
Digits, you are correct. I only wanted this a little faster. Right now it runs @ 2900 RPM. I have seen guys speed these up some, but don't recall how fast they went with them.
The motor I have does 4500 on it's own, so I need to belt it down to about 4000 max I think.
I will try to work out the toothing to 3800. That should be plenty fast for this and should still hold up well.
I will also be using a 1/4" polycarbonate shield for the most part.
As it is now, I have no shield and when the parts get cut off @ 2900, about 10% fly up and I need a baseball glove to catch them.

Really the cut off does not need to turn near that fast, but this is not controlled by Mach yet. The little motor on the 7/12 just doesn't have the torque I would like.

Gearing this treadmill motor back down to around 3800 should solve any torque issues as well.

Here is another drawing showing the motor cover.
This will be made from .125 aluminum. The end caps will be stationary and the formed cover would get screwed to some flanges on the caps.


I want to design and build an outboard rod holder for this. Very similar to the steady rest that came with this little lathe, but with adjustable roller bearings.
I have to cut the stock into 18" lengths now to eliminate floppig, but with a rest that far back, I should be able to load 36" rod.

[Jason3]

Now I want to do a lathe too!

...must finish something first...

Is it just for threading in the future that you want to control the spindle with Mach3, or for convenience / cool factor?

Jason

[LeeWay]

I didn't have much luck with controlling the motor on my mill yet, but still haven't given up. I do want it on the lathe for threading, but also to regulate the speed.
I normally run with the lathe full speed peck drilling brass and then turning and parting it.
I would need the ability to set the speed for other materials and types of turning. Especially so if it is a larger part and you have deep turnings. It starts really slow toward the outside and increases in speed as you move to the center. This effectively tries to keep the same surface speed.

I have the little C3 from CNC4PC.

I am not sure how or even if I could use this to control rotation just yet. I'll cross that bridge when I get there.

I have most of the parts I need for this and should start some assembly pretty soon. Like a couple weeks or sooner.

[digits]

I'm sure I'm not the only one looking forward to seeing lots of lovely new pics of your progress

[Jason3]

Interesting... I didn't see any note of the motor you're planning to use - did I miss it?

I had considered using a servo to drive the spindle - is that wise/unwise? My thought was to get something around 1 hp & have Mach3 control it the same as the axis servos. This would perhaps also allow live tooling. Is 1 Hp enough for threading (nothing to coarse pitch, but maybe up to 1.5" dia.)?

It seems straight forward to me, but I don't see a lot of others doing it, which makes me worry there's something I'm missing! Is there a reason not to go this way?

Regards,

Jason

Ps - Pictures!

[LeeWay]

I have considered using a big servo. Cost is really the main reason I didn't go that route. I am also not real familiar with servo's yet, but will tinker with some perhaps on a future project. Theoretically a servo should work great I think.

The drive for this motor was bought to try on my mill. The motor on the mill looks very similar to this one, but it's 180 VDC. This one is 130 VDC. This smaller controller from Surplus Center will work better for this.




I bought the larger controller from them for the mill. There is no stalling that one on 220 VAC supply.


This is the same motor I have for the lathe, but different seller from Ebay.


I think I probably paid about $35 with shipping.

I did order the speed control board from Homann Designs today to try out on the mill. I was having issues with the one from CNC4PC and I want to see if I have the same with this board.


I will get some pictures going when I get a chance to start on the building.
Thanks and stay tuned.

[LeeWay]

I had to install double nuts on my router and came up with a fairly simple and effective design. It used 3/4" x 1.5" aluminum tube. Milled the top out for nut clearance. This design leaves the top of the nuts up so I can squirt in some oil when needed. Couple three drops down each side of the tubes works great. The set crews are fastened tight on the lead nut, but just snug to stop movement on the trailing nut. This lets the spring do it's thing. I probably need to add a second set screw to the lead nut just to keep it secure in the future. The tubing was a very tight fit, but metal moves.
I was pleasantly surprised how well this worked on the router. It smoothed things out alot especially on the X where it had the most weight to push and the longest screw to deal with. 300 IPM x and y, no problem at all.

I will be using this very same double nut design on this lathe. At only $25 per extra nut, I should have done that long ago for the extra performance it gives. This was very easy to install on the router, but would be more difficult to tackle afterward on a lathe, so it's getting designed in from the start.

The springs are .08" wire and are about 3" long uncompressed. I got them from Ace for about a buck each.

[LeeWay]

Just a few pictures of some of the parts for this sitting together. I have ordered the pulleys and timing belt for the motor. I am going to go with direct drive initially. It works fine on the mini lathe, and should work even better with ball screws.

I feel a sense of urgency on this build. I was using the mini lathe the other day and all the sudden it would not do anything. I checked the fuse and everything. Perhaps there was a loose wire inside or something. I reached for a screw driver and was going to unplug it and open the control box and then it worked. So, it let me know it doesn't like doing what it does.
I will hoepfully start on this next weekend. I will be powder coating the spindle housing and its base. Probably black.

I have a question about turning the ball screws. I have turned these before on a mini lathe, but I want to make it a little easier on the machine. Would a mapp gas torch anneal the ends?
Thanks.

[Jason3]

That's a nice looking set of parts - looking forward to this weekend's update

I'm curious, would you happen to have checked how flat those extrusions are? I see plenty of people building machines with it without surfacing the linear rail mounting faces and they don't seem to have any trouble, but I've also heard that as supplied it isn't flat. I can't find a specification for it either.

I've never used it since it's remarkably expensive here so I have no personal experience with it, but would like to know more if you had a moment to give some feedback on this based on your experience?

Many thanks,

Jason

[phomann]

I did order the speed control board from Homann Designs today to try out on the mill. I was having issues with the one from CNC4PC and I want to see if I have the same with this board.
.

Hi Lee,

Did you get around to testing the DC-06 yey? I'd be interested in the feedback.

Cheers,

peter.

[LeeWay]

Jason, the extrusions aren't actually flat, though they may actually hold something flat once bolted down. You can see on the first post of my mill build here, how I flattened the extrusions for it. I wanted the most surface contact I could get as well as having a milled flat surface. I didn't have to take very much at all off. Only two surfaces needed this. One on each extrusion. I could have gotten away without it perhaps, but it was worth the effort.

I will do the same for this large extrusion. The design as shown is evolving some. I will note some of the changes in design as I get to them.


Peter, I did try the board i got from you on the mill. I was going to contact you about it when I got the chance. I couldn't get it to work. It may actually be my motor controller that isn't compatible.

This is my motor controller. I am running it on 220 VAC and it is mounted on the required heat sink. My motor is a 2 wire brushed 180 VDC 2.5 HP max. The controller maxes out for 2 HP. These two items work great together. The trouble starts when I want Mach to control them.

I think the conflict between this controller and your board is because this controller says I can't hook up S3 for use as a voltage follower. Page 23 in the pdf here.

The control voltage range on 220 VAC is also only 0 to 2.8 VDC. I think therein is the incompatability with the DC-06.

Then again, without a wiring diagram, I can only tread water. Any help or thoughts there would be great. Thanks.

Where this will be very nice is on the lathe. The mill works okay for now on manual. I could run it on the CNC4PC board, but I hate the loping that it does. Probably a setting and my fault again, though I spent many hours trying to get just the right range of speeds.

I have an index pulse card from CNC4PC, so this may help me figure out how to control the lathe for threading in Mach. The reference material there does tell me how to hook it up, but not how to actually use it, so that will me more water treading.

[Jason3]

Jason, the extrusions aren't actually flat, though they may actually hold something flat once bolted down. You can see on the first post of my mill build here, how I flattened the extrusions for it. I wanted the most surface contact I could get as well as having a milled flat surface. I didn't have to take very much at all off. Only two surfaces needed this. One on each extrusion. I could have gotten away without it perhaps, but it was worth the effort.

Lee, I even remember reading that you milled them flat now I re-read the start of your thread. Sorry... You were one of the ones I was thinking of, saying they weren't flat enough. Do you know how much they were out by - did you need to take off all of the .0075" to get them flat or was that just what you took off in one pass?

Best regards,

Jason

[LeeWay]

I could see small gaps along the extrusion when I laid a straight edge across. I just estimated it as less than .01". That was a pretty good estimate, because the .0075" eliminated those gaps so that the only gaps were the actual profiles in the extrusion. I could have went down even further, but it would have taken a lot more material removal to gain anymore surface contact. This would have weakened the extrusion too, so I stopped with one pass for a happy medium.

I think these are fine for normal routers and things just the way they are from the factory. On a router, you really aren't looking for the same accuracy as you are on a mill or lathe. Well some guys are, but that's not the norm around here.

I will be mounting the spindle on the X2 head extension minus it's dovetails and then mounting that on a CRS plate. The two Z rails will mount on 1/2" by 1 3/4" CRS flat bar. That stuff really like to buckle when you face it on one side. I will flatten the top side of this extrusion the same way in the router. Then mount the steel in place for the rails and remove just the barest minimum on the mill. I will have to remove my enclosure sides, but that is easy. The rail mounts will need two setups.
I won't surface the larger plate. I think that would be a mistake. Instead I will surface the dovetail extension once its mounted to that plate. That shouldn't throw any warpage into my face.