Replace Single Tumbler Gear Box with 2 Tumbler Gearbox

Utah Smitty · Jul 12, 2015

Hello All

I haven't posted much, but often lurk on the forums. I find a lot of good information here and appreciate the collective knowledge of forum members.

I just purchased a SB Heavy 10 lathe with the single tumbler gearbox. I have a chance to buy a double tumbler gearbox from a Heavy 10 lathe.

My question: How difficult would it be to do this--Is it a simple remove and replace operation, or what amount of modifications would be needed to do it?

Thanks in advance for any information you can provide.

Regards,

Utah Smitty

iwananew10K · Jul 12, 2015

I think you have the factory metric kit.

chip's · Jul 12, 2015

Hi, you would also need to change the lead screw. I believe the 2 tumbler has different hole locations as well. This would make it harder to mount to your machine. It is a very doable thing but a lot involved to do it. There is also having to change the stud gear for lower pitch threads. You don't have to with the single. That being said you don't have to do that very often. I like the double tumbler better but the single has good points as well. If your single is worn, the double may be a good deal if it and the lead screw (if you can get it) are not as worn. I hope this helps some, good luck.

Jim B. · Jul 12, 2015

You will also need to change the entire drive from the stud gear to the gearbox input.

That is not a trivial or cheep task

kitno455 · Jul 12, 2015

chip's said:
Hi, you would also need to change the lead screw.

You can re-machine the end of the leadscrew, as the double tumbler gearbox is wider than the single, so the leadscrew is 2 or 3 inches too long.

chip's said:
I believe the 2 tumbler has different hole locations as well. This would make it harder to mount to your machine.

Some of the double tumbler gearboxes have an extra hole that lines up with that from the single tumbler, so you can get at least two screws in it. But, the right end of the gearbox will be poorly supported unless you drill another hole in the bed.

chip's said:
There is also having to change the stud gear for lower pitch threads.

This is only true for the narrow ratio 10L gearbox. Most of the double tumblers are wide ratio, no gear changes required.

I did this swap on my 10L, but it was missing all of the end gears, banjo and covers. Given that you appear to have the metric conversion set already in place, much of the advantage of the double tumbler is moot, IMHO. Keep what you have.

allan

stephen thomas · Jul 12, 2015

Question: For those of us who don't know the difference, what are the pros/cons of each? I did not understand the single tumbler to lack any particular capability, but maybe it does?

smt

kitno455 · Jul 12, 2015

They cut the same range of threads, but the double tumbler has simpler end gearing. This makes it possible to easily swap the end gears for metric threads, DP/Module worms, etc. For South Bend, the big difference was probably cost- the double tumbler is clearly less expensive to build.

allan

Utah Smitty · Jul 12, 2015

Thanks for your reply. Yes, there's a plate on the gear cover that says it has the metric kit... however, I don't have any extra gears for it--can I still turn English threads without swapping out gears?

I have some manuals for this, but nothing that talks about the metric kit.

Regards,

Ut Smitty

SBLatheman · Jul 12, 2015

Utah Smitty said:
Thanks for your reply. Yes, there's a plate on the gear cover that says it has the metric kit... however, I don't have any extra gears for it--can I still turn English threads without swapping out gears?

I have some manuals for this, but nothing that talks about the metric kit.

Regards,

Ut Smitty

Show us what's under the end gear guard.
Ted

Utah Smitty · Jul 13, 2015

Picture of End Gears

SBLatheman said:
Show us what's under the end gear guard.
Ted

Here's a picture of the gears under the cover. The lathe is still at the previous owner's garage until I get my garage rearranged... I should have it this next weekend.

Then, I need to clean it up, replace the lube oil, etc.... it's sat for quite awhile.

Utah Smitty

Utah Smitty · Jul 14, 2015

I added a picture of the end gears for my SB 10L lathe to my previous post...

I'm not sure if all the gears I need to do English AND metric threads are there, but there isn't any others with the lathe, so I'll have to buy some if I need them.

English threads are my biggest need since I refurbish old garden tractors--but having metric thread cutting capability would be a major plus.

thanks,

Utah Smitty

SBLatheman · Jul 14, 2015

Utah Smitty said:
I added a picture of the end gears for my SB 10L lathe to my previous post...

I'm not sure if all the gears I need to do English AND metric threads are there, but there isn't any others with the lathe, so I'll have to buy some if I need them.

English threads are my biggest need since I refurbish old garden tractors--but having metric thread cutting capability would be a major plus.

thanks,

Utah Smitty

It looks like you have the standard set up for inch/English threads. You will need most of a Metric Transposing attachment, which I have for sale if you are interested.
Ted
[email protected]

SBLatheman · Jul 14, 2015

Utah Smitty said:
I added a picture of the end gears for my SB 10L lathe to my previous post...

I'm not sure if all the gears I need to do English AND metric threads are there, but there isn't any others with the lathe, so I'll have to buy some if I need them.

English threads are my biggest need since I refurbish old garden tractors--but having metric thread cutting capability would be a major plus.

thanks,

Utah Smitty

It looks like you have the standard set up for inch/English threads. You will need most of a Metric Transposing attachment, which I have for sale if you are interested. :scratchchin:

Ted
[email protected]

Utah Smitty · Jul 14, 2015

Metric Transposing Gears

SBLatheman said:
It looks like you have the standard set up for inch/English threads. You will need most of a Metric Transposing attachment, which I have for sale if you are interested.
Ted
[email protected]

I'm interested... send me a PM with the price and, an estimate to ship to zip 84120

I'm also looking for a follower rest for it.

Smitty

sicero · Jul 17, 2015

I have both and see no disadvantage with the single box. Kenny

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