Build Thread- 7 x 10 project started

[blades]

Here's my recent progress in the past week or so.
Motor mounts are done, and next up is a few purchased parts. Need a couple timing pulleys and a belt, and a split collar to clamp the screw on to the motor shaft.
I'm using the original cross-slide screw assembly (for now, anyway), and a 3/8-10 acme screw & delrin nut for the Z axis (that IS what you lathe guys refer to as the Z-axis, right? Pardon my ignorance, as I'm primarily from mill background).

One of the criteria for this project (other than low-budget) is that I didn't want to grow the footprint of the lathe excessively, and it looks like I've accomplished that so far. I'm extremely happy with the motor mounts. I will lose about 1/2" travel from mounting the motor this way. I can definately live with that.

So far the only permanent modification to the lathe is 4 m6 tapped holes in the back of the bed.

MACHINED MOTOR BRACKETS, READY TO PUT TOGETHER


STRIPPED LATHE, READY FOR THE NEW MOTOR MOUNT BRACKETS


NEW MOTOR BRACKETS & MOTORS INSTALLED

[Teyber12]

wow that looks really REALLY good! the z axis is a dual shaft right?

keep up the good work and nice pics on the machine

[blades]

Thank you Teyber! And no, it will be a single shaft setup.
More pics forthcoming when I get more done on it.

[NEATman]

Blades-
That does look good - very compact. I think that Teyber was trying to say that the Z axis motor must be a dual shaft motor, and that you will be connecting the lead/ball screw to the second shaft on the back of the motor.
I have worked out a deal and should be getting a 7x10 lathe very soon, and I am intersted in following this thread to make modifications in the same manner. Would you be willing to share models/drawings of the parts you have designed and made so far?

Have you thought about limit switches? You may be able to hide the Z axis limit switch inside the block that mounts to the X axis - and have a plunger poke out both sides of that block that would touch the headstock housing at one end of travel and the Z axis motor at the other end.

Also, you could get back the last 1/2" of travel if you made a spacer that mounts between the bed of the lathe and the motor mounting plate.

One thing you may need to watch for is backlash on the Z axis - most stepper motors don't have thrust bearings on thier shafts, they use a wave washer to preload the bearings. A simple way to check is to push on the end of the shaft by hand on the mounting flange end - if the shaft moves in, you may have an issue when your screw is clamped to the shaft.

Keep up the great work.

Keith

[blades]

Hey Keith, thank you for the comments. I believe you're right, I misunderstood Teyber's question: yes, it is a dual-shaft motor (some days I'm really slow...).

You are right about adding a spacer block to the back - good idea. I will leave it as-is for now, and address that issue if I ever need to. I haven't looked at limit switches yet, but I will have to pretty soon.

The motor seems to have no perceivable shaft end-play, as this is one of the first things I looked at when deciding how to drive the screw. Apparently, these motors have a decent thrust bearing setup. For a couple reasons, this setup will be acceptable. If this were a larger lathe, such as a 8x12 like Teyber has, I would not load the motor thrust bearings like that, I'd have the screw set up with it's own thrust bearings. I don't anticipate any heavy cuts with this lathe, and I'll only be cutting soft materials with it. Plus, my lead nut is delrin, so that won't take a lot of abuse itself. This all plays into my "low-budget project" to help keep costs down and still be reasonably solid.

The crank handle was removed from the cross-slide and attached to the z-axis motor, likewise the crank handle was also removed from the compound slide (which I won't be using anyway), and will go back on the cross-slide, allowing full manual useability (except for threading, of course). Some time ago, I replaced the compound slide with a solid block for added stability.

Absolutely I will share anything I have regarding construction information and drawings. I started out with hand-sketched drawings and built my parts from there. I do have an AutoCAD file of the 3 main parts, but nothing is dimensioned or called out. I've gotten really lazy when it comes to modeling or full drawings.

I ordered my timing belt & pulleys today. Only modification to those will be to open up a 3/8 hole in one of the pulleys to 12mm to fit on the x-axis screw.

Keep us posted as to when you get your 7x10!
I originally had no intentions of CNC'ing this lathe, but I sold my X-2 mill (which was my previous low-budget conversion project), and almost immediately started planning a retrofit for this lathe.

[Farasien]

Your build looks really clean. I know you said you don't want to increase the footprint, but there are 2 things you can probably do to get a bit more travel out of it without adding much to the footprint...

First, I like how you did the Z axis, but have you thought about making the end-of-bed plate a little longer and putting the motor on the other side of the bed? You could run the lead screw out like it was (or longer if you were planning on upgrading) so it sticks out of the end, put a timing pulley on it and run a timing belt to the motor, mounted on the other side of the bed. This would get you travel all the way to the end of the bed instead of taking, what, about 3-5 inches out of the envelope by putting it where you have it? You could put the hand crank either on the end of the lead screw or on the front side of the pulley if you didn't mind cranking the thing from there.

Second, there is a mod out there somewhere (I think its in one of the Yahoo groups relating to the mini lathe) that lets you add another inch to the X travel. All it requires is that you mill out a bit more of the clearance in the saddle for the X axis and mill a small block (about an inch deep) that mounts between the saddle and mount for the dial. It allows you to use the lathe to cut on stuff another inch or so in diameter than how its currently set up.

Lastly, any chance of seeing a few drawings of what you have so far?

-Farasien

[blades]

Actually, one of the first options I looked at was what you suggested: mounting the motor on the back side (under the chip tray) and run a timing belt setup. This was looking like a pretty good option, but I opted for my method due to it being more simplistic (albeit at the cost of limited travel).

Like I was telling Keith, I would be glad to share my drawings, but they are incomplete, lacking any dimensions or callouts. The are, of course, drawn accurately though, so dimensions could easily be pulled off the drawing. Given the opportunity and time, I will dimension them.

Funny, I used to be a tool designer for a living, and was very demanding of my own work. I'm really getting lazy (or maybe just too busy).

[Teyber12]

good to be busy in this climate

[blades]

I ended up having some time to kill at work today, so I detailed the CAD drawings. Note that I have also attached a .DWG and .DXF files as well. The .DWG file is AutoCAD 2006.

I would encourage anyone following this project to take liberties with it. Like Farasien mentioned, the Z-axis motor could very easily be mounted on the back side of the lathe (under the chip trap), and utilize a timing belt setup. I was so close to doing this, but then decided to go with how I did it to simplify things (for what I'm going to be doing with it, I won't be missing any lost travel). Also, if you're not concerned with keeping a small footprint, you could easily use this same plate and mount the motor to the other side, thereby losing no travel at all, and still keeping it simple.

I will include more engineering data once I pull it off my sketches. Will also include info regarding purchased parts.

[blades]

I picked up my 3/8" shaft collar today, so I attached the screw to the motor for try-out.

[Farasien]

I was looking at the photos you had posted for the parts and the drawings, but don't see how the ballscrew nut plate attaches to your assembly- does it get put onto the side of the carriage block somewhere? Just wondering, because I didn't see any holes on the carriage block drawing for it...

Secondly, what are the specs of the ballscrew you have and, if I may, where did you get 'em? McMaster Carr?

-Farasien

[blades]

Not using a ballscrew, it's a standard 3/8-10 LH acme screw. I did look into using a ballscrew, but opted to go with the acme screw because of price and simplicity (would love to have used a ballscrew though). Got the screw and delrin nut from user widgetmasterinc on ebay. Here's a link to the nut: LINK
The same seller also sells an 18" section of 3/8-10 LH acme threaded rod for $10.
It wouldn't be very difficult to adapt this design to use a ballscrew though. Would probably require some type of side plate off the Carriage Block.
Here's a pic showing the mounting of the nut. This pic also shows where the Lead Nut Plate is utilized.