[Lathe] Need to Replace Nylon Reversing Gear(?) in Vevor 7 x 12 Lathe

[Growley Monster]

I have a Vevor 7 x 12 mini lathe and I am having difficulties finding a replacement gear, one of the two gears on the forward/reverse lever that transfers power from the spindle to the change gears. Below is a pic, not my machine but same. You can see the handle that changes from forward to reverse, and the two white nylon gears mounted to it, secured by large hex head bolts. The gear I need to replace is the one on the right. It is .885" diameter, 20t. 0.278" thick, 0.392 I.D. Part of my problem is I do not know what that particular gear is officially called. Vevor doesn't put out much of a manual and no drawings or parts list, and getting help from them is like pulling teeth.



Being that the gear is nylon or some other plastic, and is very vulnerable to someone ignoring the instructions to put the machine into all stop before changing directions of the feed screw, I KNOW there have been a lot of these replaced, so somebody must be making them. Below is a pic of my trashed gear. I guess you would call it the feed screw reversing gear? I don't know.


Any help appreciated.

 

[VicHobbyGuy]

Your Vevor is probably made by Realbull, other 7x lathes are mostly made by Sieg. Not all parts fit both lathes. LittleMachineShop would be the first place I would try - I've heard that they have knowledgeable people answering the phones.
https://littlemachineshop.com/products/product_view.php?ProductID=1353&category=

 

[WobblyHand]

Looks like a 7mm thick, module 1 gear, 20T, with a 10mm bore. The gear is out of focus, does it have a key way in it? Can you measure it? This is a metric gear.

 

[VicHobbyGuy]

If you have access to a 3D printer you could print a gear which would work OK, at least until you got a 'nylon' gear.
The gear plugin for OnShape is really easy to use (even I could produce a usable file); probably other CAD software has something similar.

 

[markba633csi]

Sometimes called a "tumbler reverse gear"

 

[ChazzC]

Your Vevor is probably made by Realbull, other 7x lathes are mostly made by Sieg. Not all parts fit both lathes. LittleMachineShop would be the first place I would try - I've heard that they have knowledgeable people answering the phones.
https://littlemachineshop.com/products/product_view.php?ProductID=1353&category=

They also have a metal “upgrade” p/n 3455. They usually have someone in the technical side available, but make sure you have all of the nameplate info ready. It looks like all of the 7x lathes use the same two gears in the reversing group: a 20T & 25T. I would replace both, and get a set of spares. With the exception of the change gears, I believe all of the other gears are metal.

I suggest you also get the three plastic gear-sets/gears in the High/Low train unless your lathe does not have these (eventually one of these will fail).

Before you reassemble the lathe, check the fully engaged locations for the forward/reverse lever and either deepen the existing detents or drill new ones. The factory detents aren’t very deep and can allow the lever to shift unintentionally causing the damage you have.

 

[GrifterGuru]

@Growley Monster Have a look at LMS and see if they carrier reverse tumbler gears. They should be the same as Sieg C2/SC2 C3/SC3 reverse tumbler gears.

As for stopping the lathe to go from reverse to forwards or visa-versa, with a practiced hand and a fast enough action, it can be done. I do it regularly, though I do have metal gears fitted since I replaced mine.

@WobblyHand The reverse tumbler gears are the only two gears in the whole gear-train that are not keyed.

@ChazzC Not all machines have a "full metal" gear set (Sieg certainly do not!). I had to pay out a vast amount to get all metal gears to cover imperial threads and metric pitches. The only "gotcha" was the need to open the keyway in some of the gears with a needle file.

Some machines have narrow keys, others have a wide key. BTW, good call on the detents. I actualy used the lever as a "centre-punch" since it is a hard cone-point, then pin drilled the locations before countersinking for full engagement. (will have to grab a photo).

 

[WobblyHand]

If you can buy the gear, get it, especially since it won't be all that expensive. That kind of gear is quite printable, bet I could whip up an stl file in under 5 minutes. M1 gear, 20T, 10mm bore, 7mm thick. Well I lied, it took me 4 minutes. If you can't buy one, see if you can print this.

 

[ChazzC]

@Growley Monster Have a look at LMS and see if they carrier reverse tumbler gears. They should be the same as Sieg C2/SC2 C3/SC3 reverse tumbler gears.

As for stopping the lathe to go from reverse to forwards or visa-versa, with a practiced hand and a fast enough action, it can be done. I do it regularly, though I do have metal gears fitted since I replaced mine.

@WobblyHand The reverse tumbler gears are the only two gears in the whole gear-train that are not keyed.

@ChazzC Not all machines have a "full metal" gear set (Sieg certainly do not!). I had to pay out a vast amount to get all metal gears to cover imperial and metric pithreads and pitches. The only "gotcha" was the need to open the keyway in some of the gears with a needle file. Some machines have narrow keys, others have a wide key. BTW, good call on the detents. I actualy used the lever as a "centre-punch" since it is a hard cone-point, then pin drilled the locations before countersinking for full engagement. (will have to grab a photo).

I agree Grifter; I should have been clearer: with the exception of the High/Low gear train (on those lathes that have them), change gears and reversing gears (including the 45T change gear drive), the few remaining gears (20T output/upper gear, 20T intermediate/lower gear [although mine is a plastic 15T – part of the 90/15/90 slow feed set], 45T change gear drive) and the two timing belt pulleys are metal. The metal change gear set, plus a metal 21T gear (for better metric threads) are upgrades.

 

[Growley Monster]

Looks like a 7mm thick, module 1 gear, 20T, with a 10mm bore. The gear is out of focus, does it have a key way in it? Can you measure it? This is a metric gear.

Yeah I measured. OD is .858" * 25.4 = 21.7932mm, so call it 22mm in metric. There is probably some wear on the tooth tips so 22mm is realistic. 0.278" * 25.4 = 7.0612 mm thick and not critical measurement anyway, so 7mm thick it is. ID measures .392" * 25.4 = 9.9568 and 10mm should work just fine there. 20t in metric is still 20t unless they changed the rules.

At module 1, a 20 tooth gear should be 22mm dia with a pitch dia of 20mm and root dia of 17.5mm so close enough to say that yeah it is a metric gear. I measure in inches though. Don' need no steenking metric dial caliper.

No keyway. The gear just spins free on its mounting bolt. When the lever is pushed down, that gear is driven from the spindle, driving the other gear on the arm, which drives the change gears and feed screw.When the lever is pulled up, the bad gear is disengaged and the other gear engages the spindle gear directly, and either way, it still drives the change gears and feed screw. In the middle position neither gear engages with the spindle and nothing happens with the change gears and feed screw at all.