# Vevor  250 x 750 Lathe Upgrades



## lesrhorer (Sep 6, 2021)

*Phase I: DRO*
Installing the Digital Readout was a bit of a challenge.  Space was tight, and I had to re-do some of the parts.


----------



## lesrhorer (Sep 6, 2021)

Parts Detail:


----------



## lesrhorer (Sep 6, 2021)

X-Axis:


----------



## lesrhorer (Sep 6, 2021)

Z-Axis:


----------



## lesrhorer (Sep 6, 2021)

Full Assembly:


----------



## lesrhorer (Sep 6, 2021)

Photos:


----------



## lesrhorer (Sep 6, 2021)

*Phase II: Motor*
They were supposed to ship me a lathe with an 1100 Watt motor, but they sent one with a 750 Watt motor by mistake.  Rather than ship the entire system back, they refunded me the cost of a 1200 Watt motor.  The original was a higher speed brushed DC motor, but the new one is a 3000RPM brushless motor.

The original design employed a 3 position idler cone pulley and a 2 position cone pulley on the spindle, using tiny V-belts to allow for two spindle speed ranges.  V-belts (especially ones this tiny) can tend to slip and one of them shredded itself within a few hours of operation.  The new motor should allow the lathe to operate across a wider speed rage (3000RPM vs. 1250 / 2500 RPM) with higher torque, without the need for belt changes.  The original idler bracket was poorly made, with a very sloppy fit and poor registration.

In addition, I changed the V-belt pulleys out for timing belt pulleys, which should prevent slipping.  If the torque turns out to be too low at the low and high ranges, I will change out the motor pulley to one with fewer teeth.

In order to maintain tension on the belt, I designed an idler pulley with a threaded rod adjustment.  This is an idler only, not a transmission gear.

Here are photos of the original design, which employed a 4mm steel motor mount:


----------



## lesrhorer (Sep 6, 2021)

Parts Detail:


----------



## lesrhorer (Sep 6, 2021)

Photos:


----------



## tweinke (Sep 6, 2021)

Looks like nice work to me! I see you have changed the drive for the spindle also, any details?


----------



## lesrhorer (Sep 6, 2021)

Thanks!  I am not certain what you mean by "details".  I replaced the pulley, if that is what you mean.  ErichKean was kind enough to bore the motor pulley and the spindle pulley and broach keyways into them for me.


----------



## matthewsx (Sep 6, 2021)

Nice write-ups with high res pictures. Good to have detailed info on how to make lower end machines perform in a hobby shop

John


----------



## lesrhorer (Sep 6, 2021)

Thank you.  More to come...


----------



## lesrhorer (Sep 17, 2021)

*Phase III: QCTP*
The lathe came with a classical square turret tool post.  Now, there is nothing particularly wrong with those posts, and they certainly have excellent rigidity, but unless one is engaging in a very limited set of operations on the lathe, the Quick Change Tool Post is certainly far easier and faster to swap out and set up tools on the lathe.  Given the relatively low cost and very decent quality of Aloris clone tool posts, I would say it is, if not quite essential, at the very least a highly desirable and economical upgrade for the lathe.  Swapping out the tool post is fairly easy.  The hold-down bolt for the square tool post is usually too short, so the first step is to remove it from the compound and replace it with the one supplied with the new tool post.  The QCTP may come with a thick spacer to fit between the post and the compound.  Its use may or may not be necessary.  In my case, it was, but the spacer did not fit my lathe.  Rather than modify the spacer, I made a new one from cold-rolled steel.  The post tended tor slip on the spacer, so I roughed up the surface of the spacer so it no longer slips.  There is a small indexing post on the compound, so I drilled a small divot in the bottom of the spacer to accomodate the indexing post.  This insures the spacer does not slip on the compound.  I made the spacer of round stock, but a couple of the tool holders, notably the parting tool, need to slide down further than the spacer allows.  I milled off one side of the spacer to allow the holder to sit all teh way down on the compound when necessary.

When tightening down the tool post at a required angle, there is a tendency for the post to slip as the nut is cinched down.  A simple flat washer caqn help alleviate this, but a thrust bearing will help even more.  I purchased a thrust bearing off Amazon for $3 - hardly a difficult purchase.  The thrust bearing with its two included flat washers not only completely eliminates any tendency of the post to move when tightening it down, it also allows the original locking lever that came with the square tool post to be used.  Without the thrust bearing, the bolt was just a little too long to allow the lever to be used, meaning one had to use a plain hex nut with a separate wrench to cinch down the post.  The permanently attached lever is far more convenient.


----------



## lesrhorer (Sep 17, 2021)

Photos:


----------



## lesrhorer (Sep 17, 2021)

*Phase IV: Chip Shield*

I previously posted the plans for this guard here. Machining on the lathe or mill tends to cast swarf all over the shop, including in my face and down my shirt. This helps. I machined a small shelf out of mild steel and attached it to the left side of the carriage to make it more convenient to attach the magnetic base and position it over the chuck. It can also attach to the compound.


----------



## lesrhorer (Sep 17, 2021)

Photos:


----------



## lesrhorer (Sep 21, 2021)

*Phase V: Carriage Handwheel*

The carriage handwheel on this lathe is quite unacceptable.  It wobbles badly, causing the movement of the carriage to be very jerky as the friction betwen the wheel and the carriage body jumps up and down wildly.  Furthermore, the handwheel handle is very short and thin.  This means it is a bit uncomfortable to grasp, and since the wheel is quite close to the cross slide handwheel, it means my fingers often hit the cross slide wheel handle.

Job 1 is to add a pair of thrust bearings to the wheel and tighten the wheel on the axis.  There are a couple of hitches, however.  The first is the handwheel assembly fits through a 16mm hole in the carriage, while the axle is 10mm.  Obviously, the thrust bearing on the inside of the carriage housing next to the drive gear cannot be more than 16mm in outer diameter.  I looked rather extensively, but rather unsurprisingly I was unable to find a 10mm x 16mm thrust bearing.  I decided to manufacture the bearing right into the handwheel assembly itself.  I purchased some 2mm ball bearings, and turned down the shaft near the drive gear by 2.2mm.  I then bored out the body to a depth of 1.8mm and a diameter of 12mm.  I placed 18 ball bearings down inside the body next to the shaft.

On the other end of the shaft, there was not quite enough room between the body and the Woodruff key to accommodate the outer thrust bearing, so I faced off the body by 1.5mm.  Unfortunately, after this was done, the recessed retaining screws stuck up above the body, interfering with the placement of the bearing, so I used an end mill to bore the counter-bore down by another 1.5mm.  The hand wheel stuck out a little more than I liked, so I bored an 18mm hole 3.5mm deep in the body to accommodate one of the thrust washers and the bearing, leaving 2mm of the thrust bearing assembly protruding from the body.


----------



## lesrhorer (Sep 21, 2021)

Photos:


----------



## Weldingrod1 (Sep 21, 2021)

A fun mod! The light loads should play well with the un-hardened surface.

Sent from my SM-G892A using Tapatalk


----------



## lesrhorer (Sep 21, 2021)

Thanks.  Yes, the loading should be less than 20 lbs per bearing, I expect. The aluminum may still deform by a few tenths into a semi-torus shape due to extrusion, but I don't think it will wear appreciably.  If it does, I can always tighten the nut a bit.  It's a very simple piece.  I could easily replace it with steel, if necessary, but I don't think it ever will be.


----------



## lesrhorer (Sep 25, 2021)

The handwheel now runs smoothly without any appreciable wobble.  This did not affect the backlash, obviously, but the backlash is only moderate, and the feel is much more precise.


----------



## lesrhorer (Sep 25, 2021)

Job 2 is to replace the handle assembly on the handwheel.  The carriage handwheel is quite close to the cross slide handwheel, and its handle is very short.  This means it is very easy to accidentally pinch the hand between the grips of the two handwheels.  The grip is also a bit inconveniently thin, producing an unnecessarily high pressure on the fingers when turning.  Finally, it did not run smoothly when moving the carriage.

I replaced the 8 x 45 + 10 mm retaining screw with a 5/16" steel drill rod, 112mm long, tapped at both ends.  The end facing the handwheel was tapped to 6 x 1 mm, to match the threads in the handwheel.  The other end was tapped to 10-32.  The rod is well polished to limit friction between it and the Aluminum grip, which is also much longer and fatter (3/4") than the old grip.  I considered knurling the grip, but since there will be almost no torque applied to the grip when in use, I decided not to do so.  The grip was bored its entire length to 8.0mm and tapered to 0.500" at one end.  The other (untapered) end was bored to 16.1mm x 19.0mm deep.  I inserted a 6mm x 20mm stainless steel set screw into the 5/16" steel rod and added blue locktite to both sides of the threads, screwing the rod into the handwheel.  I slid an 8 x 16 x 5.5 mm thrust bearing over the rod, followed by the grip, which was then followed by another 8 x 16 x 5.5 mm thrust bearing.  To maintain a proper pre-load on the thrust bearings, I followed the second thrust bearing with an 8mm x 15mm stainless steel wave washer.  I machined a piece of Aluminum to 15.25mm diameter x 9.5mm long.  I bored the piece to 5mm and then counter-bored one end to 8.5mm x 5mm deep.  This bears against the wave washer.  A 10-32 button head allen screw holds the entire assembly together.

Now it runs vary smoothly and with no appreciable wobble or slack.  The surface finish of any hand-turned parts is vastly improved.  No more bruised knuckles.


----------



## lesrhorer (Sep 25, 2021)

Photos:






(Old handle on the left.)


----------



## Sparkynutz (Mar 31, 2022)

Nice upgrades. Anything new lately?


----------

