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Restore or Not? WT Lathe

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shell70634

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#1
I have an older lathe from Taiwan, Model TD-4A. It has a bad gear. The Book identifies it as TD-4H-11 Change Gear. It's a 70 tooth steel center nylon tooth gear approx 4 1/2 in diameter with about a 7/8 in center bore. If I can't sell it as is, is it worth restoring? I've been told production ended in 1985 or so.
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dtsh

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#2
I'm not overly familiar with these newer lathes (1980's is still "new" compared to mine) but it is my understanding that many of the parts are still available from various sources. Failing that, perhaps a look over at Boston Gear might turn up something useful. I've read where some folks have even used 3D printed gears (Atlas lathe I believe). I'm sure someone more familiar with the model will come along with more accurate information.

Assuming the rest of it is in good shape, it's probably worth repairing, but I would consider checking the spindle, ways, feed screws, etc for excessive wear before spending much time or money on it as a good gear train in an otherwise clapped out lathe isn't especially useful or valuable.
 

4ssss

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#3
Wholesale Tool is still in business. Maybe they can steer you to a gear. As stated above, Boston Gear will be your next best bet. I wouldn't replace it with another nylon gear.
 

bfd

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#4
that gear is the built in failure point. it needs to be something that will save the rest of the geartrain in case of some lock-up situation, if you replace it with a steel gear then it needs some sort of shear pin setup to protect things. my lathe has a similar gear in its geartrain . when I got it, it was cracked so when I found it at enco ( yes my lathe is an enco) and I bought 2 of them just in case. bill
 

4ssss

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#5
that gear is the built in failure point. it needs to be something that will save the rest of the geartrain in case of some lock-up situation, if you replace it with a steel gear then it needs some sort of shear pin setup to protect things. my lathe has a similar gear in its geartrain . when I got it, it was cracked so when I found it at enco ( yes my lathe is an enco) and I bought 2 of them just in case. bill
If you don't abuse the lathe , (IE running the carriage into the chuck) you'll be fine with a steel gear. Believe it or not, those lathes from Wholesale tool were actually pretty good, and they sold a lot of them.
 

Ray C

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#6
As mentioned, the gear was made of plastic/nylon as a failure point. If the specs of the gear a known (pitch, # of teeth and pressure angle) a new one can be made. Many folks are having success using 3D printers. Steel is fine too and as mentioned, a false center bushing held with a shear pin would be a good idea.

If the rest of the lathe is in working order and it serves your purposes, heck yes, just replace the gear.

As far as "abusing" a lathe. Abusing a lathe is when people take medium duty machines install chucks and toolpost holders that are 1 or 2 sizes too big and attempt to hog-off metal the same way Abom does with a 3 ton machine with a 15HP motor.

Crashing a piece of equipment is something to absolutely avoid at all cost. Doing it intentionally is a clear-cut case of abuse. That said, if anyone uses machines on a very regular basis, there are two kinds of machine operators... Those who have never crashed a machine -and those whose turn is coming.

Not all crashes are catastrophic and not all are avoidable. It's happened to me twice. Once when a a parting blade broke (out of the clear blue sky) and once when my oily hand slipped off the carriage release. My brake pedal cuts power and seizes the main spindle. Other than a bruised ego, no harm done.

Ray
 

projectnut

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#7
that gear is the built in failure point. it needs to be something that will save the rest of the geartrain in case of some lock-up situation, if you replace it with a steel gear then it needs some sort of shear pin setup to protect things. my lathe has a similar gear in its geartrain . when I got it, it was cracked so when I found it at enco ( yes my lathe is an enco) and I bought 2 of them just in case. bill
I would agree. My 1960's era Sheldon also uses a plastic gear(in this case phenolic) as a sacrificial element should you have a crash. It also helps keep down the noise in the gear train when running at high speeds. In this case the machine is capable of 2,200 rpm. This is a machine made for the professional market. The manufacturer recognized accidents do occur regardless of the operators level of experience. My machine is going on 60 years old and the gear has been replaced only once. It was not replaced as the result of a crash, but rather as a part of a total rebuild in 2003. The original lasted over 40 years in a commercial shop. I doubt you'll be using the machine nearly as much, so I would expect a replacement to last a lifetime barring any crashes.

Knowing that the manufacturer has gone to the trouble of making a sacrificial element indicates to me that in cases where crashes have occurred damage to machines without the sacrificial element has been far more costly to repair than those equipped with that element. I would look into the price of an original replacement as opposed to a steel one. If the prices are similar I would stick with the original equipment.
 

Dave Paine

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#8
I think it is worth restoring. Look around for an STL file for the gear. Several forum members including myself able to 3D print a gear, we just need the STL file.

A recent thread on 3D printing change gears.

3D printing change gears thread
 

shell70634

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#9
Well, it's not my problem now. Sold it this morning. I will make sure the buyer knows about this site and all the help there is here.

Thanx
Shelly
 
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