Cutting SAE 24 TPI threads on an asian lathe

[Road_Clam]

Hey all, i'm looking for an asian lathe that's capable of cutting SAE 24 TPI threads and most of the typical metric screw asian lathes can not cut this pitch. Is it possible to purchase optional change gears to cut 24 TPI or is this not possible ? Tried researching this specific requirement and come up with nothing specific. Interested in purchasing this asian lathe :

8.7"x29.5" Mini Metal Lathe Variable Speed Metalworking Machine 2500RPM 1100W | eBay

Motor Power: 1.5 HP (1100W). 1 × Follower Rest. 1 × Mini Lathe. Swing over Bed: 8.7 in. 5 × Turning Tools. Max Spindle Speed: 2500 rpm (±10%). Thread: 8-44 tpi. Motor Type: Brushed.

www.ebay.com

 

[pdentrem]

Found same lathe in this topic.

Mini Lathe and Change gear calculators

I have a wm210 mini lathe that has the 38mm spindle bore with a 56t gear. The banjo has 3 pairs of gears but the bottom pair is actually a gear and spacer. The gear calculator on Little Machine Shop produces charts with only 4 gears. Can those gear combinations be used with my setup and if so...

www.hobby-machinist.com

My original response what this.
You need to know the pitch of the leadscrew and will have use a threading gear chart which are available online. 56 on the spindle and I see the following gears listed on the threading chart. 30,33,40,50,52,60,66,72,80,84
Pierre

 

[markba633csi]

I would buy from a reputable supplier like Precision Mathews or Grizzly. They will guarantee the performance of the machine
These no-name machines are a gamble- some folks have found the no-name machines sometimes will not cut the threads listed and the charts on the machine don't match up with the manual (if there is one)
Also there have been reports of machines not supplied with all the necessary change gears
Buy from a good company and you can avoid such problems
-M

 

[Bi11Hudson]

Having followed your link, the machine shown appears to be marketed for the U.S. and other english speaking countries. I couldn't see the threading chart clearly in the advert, but it appears to be threads per inch. 24TPI is a fairly common thread and is very close to 1mm pitch (25.4TPI) If the metric conversion gears are included, it should be a "drop in" conversion from one to the other.

The gears to convert from metric to imperial or vice versa are 127 tooth and either 100 or 120 tooth. The 120 is the more common and is amenable to more combinations. The small machines such as this usually have external change gears. Some more advanced models have an internal "transmission" to handle this function. The "normal" threading range will be from around 4 TPI to around 80 TPI. The normal being taken with a very large dose of salt.

We all know what advice is, and is worth. . . I would advise you source a machine from a well known vendor. In your case, one that lists the threading ranges openly as part of the advert. Little Machine Shop, Precision Matthews, Jet, and Grizzly being near the top of the list. Harbor Freight would be towards the bottom. An unknown vendor is a stab in the dark at best and may or may not provide a particular (often critical) part. The cost may well be a few dollars more with a well known vendor. But they have aftermarket assistance that is often invaluable.

.

 

[homebrewed]

Little Machine Shop sells an 8.5x20 lathe that is specified to cut both metric and SAE threads. You will pay more for it than the ebay vendor linked in your OP, $2699 not including shipping. They stand by their stuff so if there's a problem they will correct it. The motor is a 1KW DC motor so similar to the ebay version (if not exactly the same thing). If it matters to you, the LMS version appears to be a blend of Metric/Imperial with .001" graduations on the dials and a 2mm lead screw.

I note that the ebay package includes a fixed and follower steady rest, LMS doesn't. Sort of a negative there for LMS.

For the added cost, the LMS version is far more likely to work out of the box. Machines from no-name vendors are notorious for being more like a kit, so be prepared to do some light-to-serious messing around with that one. OTOH you might get lucky, but I wouldn't count on it.

I don't own one so am just going by my experience with LMS. Good folks. No affiliation other than being a satisfied customer.

The LMS lathe uses change gears, not a gearbox. But gearboxes aren't all that common for lathes in this class.

 

[RandyWilson]

LMS also sells the changegear set that does both metric and imperial on these C4 lathes.

Change Gear Set, Bench Lathe, Metal 4583

8.5x20 Lathe (C4/SC4) Accessories 4583 Change gear set for the HiTorque 8.5X16 lathe; Module 1 metric gears; Bore 16 mm; Keyway 4 mm; Width 9.75 mm; C...

littlemachineshop.com

 

[Road_Clam]

The LMS 8.5x20 is a great lathe but I need a minimum 25mm / 1.00" spindle bore as I want to be able to tackle threading heavy contour rifle barrels which typically measure .83"+ dia at the muzzle. As for PM and Grizzly, I'm just tired of "backordered status" for over a year now. Really the Grizz 11x26 is a great choice but the post covid supply of lathes has been seriously interrupted and like I said, tired of waiting.

 

[RJSakowski]

In absence of a manual, I made some assumptions regarding the change gears and lead screw. I assume that the h in the charts indicates a spacer so the gear on the same shaft functions only as an idler. It also appears that the lead screw is metric and the pitch is 2 mm. Going through calculations for various thread [pitches based on the charts, it appears that only the .5mm, 1.0mm, and 2.0mm pitches are exact. The others are, IMO, poor approximations of the nominal pitch. It gets even worse for the SAE threads. It is theoretically possible to select gear combinations using additional gears to create close approximations to nominal pitches although it may be hindered by physical restraints.

In other concerns, pluses for the lathe is the large bore size, a 1.5 hp. variable speed motor, and the long bed length. On the negative side, the low wt. means loss of rigidity which is one of the biggest drawbacks to a small lathe. The ways are flat as opposed the having a vee way for more positive positioning of the carriage and tailstock. There is no mention of the chuck mounting scheme. I suspect that it is threaded. If so, what are the threads. This is important when one desires add a four jaw chuck or a collet chuck. A faceplate is not included. Only six change gears are shown in the included parts while the charts show 10 gears, meaning that quite possibly all of the threads shown cannot be cut with the stock gears provided. Curiously, the marketing hype states that the 3 jaw chuck can mount both round and square stock. I am at a loss as to how square stock can be mounted in a 3 jaw chuck. (Joe Pyczinski shows a work around but not an easy method)

Based on these observations, I would strongly recommend not purchasing this lathe.

 

[Road_Clam]

In absence of a manual, I made some assumptions regarding the change gears and lead screw. I assume that the h in the charts indicates a spacer so the gear on the same shaft functions only as an idler. It also appears that the lead screw is metric and the pitch is 2 mm. Going through calculations for various thread [pitches based on the charts, it appears that only the .5mm, 1.0mm, and 2.0mm pitches are exact. The others are, IMO, poor approximations of the nominal pitch. It gets even worse for the SAE threads. It is theoretically possible to select gear combinations using additional gears to create close approximations to nominal pitches although it may be hindered by physical restraints.

In other concerns, pluses for the lathe is the large bore size, a 1.5 hp. variable speed motor, and the long bed length. On the negative side, the low wt. means loss of rigidity which is one of the biggest drawbacks to a small lathe. The ways are flat as opposed the having a vee way for more positive positioning of the carriage and tailstock. There is no mention of the chuck mounting scheme. I suspect that it is threaded. If so, what are the threads. This is important when one desires add a four jaw chuck or a collet chuck. A faceplate is not included. Only six change gears are shown in the included parts while the charts show 10 gears, meaning that quite possibly all of the threads shown cannot be cut with the stock gears provided. Curiously, the marketing hype states that the 3 jaw chuck can mount bith round and square stock. I am at a loss as to how square stock can be mounted in a 3 jaw chuck. (Joe Pyczinski shows a work around but not an easy method)

Based on these observations, I would strongly recommend not purchasing this lathe.

thanks for taking the time to add a very comprehensive reply ! Now that you offered experienced feedback , I'm throwing up red flags on the linked asian lathe. I've been scouring my local FB marketplace for a South Bend lathe but very few are available and the ones I do see are either clearly beat up and rusted, or the seller claims vague details and the typical "I know nothing about this lathe" yet oddly they did extensive research to know the market pricing....