Metric Transposing Gears for SB 13

Can anyone point me to information on metric transposing gears for a SB 13" lathe?

I have a couple of SB 13's and would like to setup one to do metric threading.

I searched the normal forums and did not find anything for the SB 13.

Either a source for the gears and threading charts such as those available for the SB 10 or the specifications for the gears so we can cut them in our shop.

Thanks,

Frank

Do your 13's have double or single tumbler gearboxes?
I think I have a complete set for the double tumbler. I will check tomorrow.
TED
[email protected]

Regardless of the lathe, if you have a TPI leadscrew, you have to put a 100/127 ratio somewhere between the spindle and the leadscrew. Once you've got that, it's a simple matter to figure out corresponding metric pitch.

Quick example:

20 TPI QC box setting with a 100/127 reduction somewhere in the train results in 20 / ( 100/127) = 25.4 TPI. There are exactly 25.4 mm in 1", so you're at 1 mm pitch.

The "perfect" way to get that 100/127 reduction is to stack a 127 and a 100 tooth gear together on one of the idler shafts between the spindle and the QC input shaft. Those are big gears though, and usually quite expensive. They also won't fit within the confines of some lathes's headstock areas. There's another ratio, 37/47, that is very, very close to 100/127. So, if you can get those two and stack them on an idler shaft, you'll be very, very close to the exact ratio.

Regards.

Finegrain

TED,

Both are double tumbler gearboxes.

Thanks for the response.

I will look forward to hearing the results of your search.

Frank

courtesy of Jeff Beck

I have a photo of a chart that covers the 13,14-1/2,16" double
tumbler
> and it seems to only have 2 things different then the 9-10 chart.
1)
> The gear box output uses a 64t instead of a 56t gear and 2)Those
lathes
> have a single arm banjo gear bracket instead of the double arm
style.
>

Click to expand...

all the best.markj

FrankW said:

Can anyone point me to information on metric transposing gears for a SB 13" lathe?

I have a couple of SB 13's and would like to setup one to do metric threading.

I searched the normal forums and did not find anything for the SB 13.

Either a source for the gears and threading charts such as those available for the SB 10 or the specifications for the gears so we can cut them in our shop.

Thanks,

Frank

Click to expand...

Frank,
I have 2 complete sets of IN/METRIC gears and spacers(N.O.S.). I do not have the index plate like the one that aboard epsilon displayed, but I can supply a copy of the doucument I have that has the information needed.
$500 each plus shipping(should fit in a large flat rate box)
TED
[email protected]

$500 !!!!.....wow ..we are living in inflated times .

all the best.markj

The SouthBend set is comprehensive and easy to use because the metric pitches come pretty much in order on the box without a lot of hopping around or gear train changes but it does use a fair number of gears.
It can be done more simply using 40, 30 , 120 and 127 gears giving a more limited but fairly comprehensive range of pitches viz:- 6, 4.5, 4, 3, 2.5, 2.25, 2, 1.8, 1.5, 1.2, 0.9, 0.75, 0.6, 0.5, 0.45, 0.3, 0.375(?), 0.25 mm. I think I've got the complete list there.

The trains are either 40/127 x 120/GD or 30/127 x 120/GD so there is only one gear switch involved. GD is the standard gearbox drive gear and / represents the driver /driven pair. Hope that's clear but its getting late.

Clive

I was thinking of using my double tumbler 13" to cut some metric threads and wodnered if I could get by with just changing one gear-the 127 tooth solution mentioend above. Can that be done to my lathe?

If so, where does the gear need to go and where can I find one?

CLive-would you happen to have a pic or schematic showing what has to be swapped? I do not need a full metric range.

$500 is pretty freaking steep for what metric threading I need to do. I am wondering if there is a much lower cost solution.

Marc

Attached are pictures of the imperial gearbox plate and metric conversion plate from a lathe using this simple conversion. Sorry about the angle and quality but these are clipped from larger pictures and I don't have the original images.
This lathe used a 40 tooth stud gear running at spindle speed and a 40 tooth gearbox driver. I've calculated things for my Heavy 10, which also has a 40 tooth driver, to verify that you get the correct results by retaining the standard gearbox driver (56 tooth) and simply swapping the 40 and 30 tooth stud gears as required.

Clive

The trick is getting your hands on the 120 and 127 tooth gears. They turn your 13"'s 6 TPI lead screw into one having an effective pitch of 4mm which has a prime factor of 2, everyone's best friend because we love even numbers so much.

While 120s are easy to make using standard dividing equipment, good luck finding that 127 hole indexing plate which is what you need because 127 is prime.

That's why you are going to pay the man $500 for set of NOS metric change gears from SB.

'tis a pity that the $200 Heavy 10 set that you can buy on ebay wasn't made with a 127/120 transposing gear instead of a 127/100. The Heavy 10 runs a 8 tpi lead screw and a 127/100 gives you a 2.5 mm effective pitch while 127/120 would give you 3mm effective pitch, both workable. A 127/100 running on a 13" will give you an effective 3.33333... mm pitch which is no one's friend.

WestCoastFranky

127 gears can be got, at a price, from stockists. If the right DP isn't gettable or is too expensive then its feasible to get the least expensive one of adequate diameter and use that as a notch plate to either make a temporary single row division plate a direct division set up or even do the gear cutting work directly from it if you are confident your set up is good enough.

Big advantage of making a temporary plate and running it through a conventional dividing head to make a second generation plate is that any errors are reduced and spread out. The error reduction repeats when using the second generation plate so any gear produced will be more than good enough unless the first temporary plate was terrible. Careful stepping out with dividers will produce a good enough plate to use directly. CAD drawing printed out on sticky back paper and drilled at the marks ought to be good enough for a first generation plate.

One method I've always fancied trying to make prime number dividing plates was inspired by the humble spin indexer. Consider starting with a gettable or available plate say ± 1 or 2 from the desired prime and arrange the locating pin registration hole to be on an arm pivoted concentrically to the indexer spindle with a micrometer push adjuster. As the reference plate has either slightly too many or not quite enough holes the micrometer can be used to push it forward or back buy a calculated amount each time you move to the next index hole to give the correct number of holes in the plate being made. Using a computer spreadsheet its no great problem to calculate how much micrometer movement is needed at each step but its advisable to choose a radius of action giving easy setting increments. Either use the spreadsheet solver routine or think things through when setting up the initial calculation. Best to arrange the push through a pivot to avoid cosine error although I guess a ball end adapter would be good enuf.

Clive

A Harrison 300 is looking better by the minute.

Marc

Yup it is. Having the metric conversion in the box is so much easier. However metric threading is a PIA on any lathe not properly fitted out for the job with a single tooth dog clutch in the train, auto stop at the end of the thread and fast carriage return.

Clive

Does anyone have photos of these parts, I have a 13 and it came with some exrta gears and parts that I would like to identify.

Sent Frank a PM

Sent PM on some Gears
Milton

Pictures of actual gear train

Does anyone have a picture of the actual gear train with the metric transposing gears?
This is my 13" serial 2059 TKL9 and I am not sure where the transposing gears would go.

The 3 large gears are 66 tooth about 4 7/8" diameter making them 14 DP. The middle gear is the sliding gear that changes the ratio from 3:1 over to 1:3 when you pull the sliding gear outward. Thanks, David

Alternate source/possibilty for metric transposing gears for the 13"....

SB13" metric transposing gears from amazon.com.....mostly