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

mgermca

Plastic
Joined
May 17, 2010
Location
Montreal Canada
Hi all,

I've owned my 13" double tumbler SBL since the early 90's and have always found a way around the need for metric thread cutting capability.

This winter however, I needed to cut some metric threads for my son's Honda Sabre V65 cafe racer project
( http://www.customfighters.com/forums/showthread.php?t=121226&page=17 ) so I started shopping around for a set of metric transposing gears.

If you are reading this you probably are up against the same thing I was, that 13" SB accessories are getting harder and harder to find, and when they do come up for sale they can be quite pricey.

I have some very detailed email exchanges with fellow Practical Machinist member Gene Poole on the subject and he sent along words of wisdom and photos of his OEM set that are also posted in this thread
( http://www.practicalmachinist.com/vb/south-bend-lathes/10l-build-ideas-314254/ )

The info I had from Gene regarding his OEM gearset had the following essential information:
i) You swap out the lower QCGB driven gear with a spacer and the 64T gear that is included in the stock metric set. The spacer makes up for the fact that the "idler" is now a stacked offset set of gears that are pinned together (127/120) so the 64T QCGB drive gear must sit further out.
ii) Note that these are a different pitch than the normal imperial gears, this so the higher tooth count gears still fit under the side cover, even the big 127 tooth gear.
iii) All the gears in the metric set are 16DP as opposed to the standard set which is 14DP....

So I set off to see if Boston Gear had anything in 16 DP that could be used to build a set of transposing gears for a 13" SBL.
The Boston Gear catalog here eCatalog | Enclosed Speed Reducers | Open Gearing | PT Components | Boston Gear and its 'change gears' section had pretty much what was needed, even the 127T gear.
However, it was clear from the outset that some compromises would have to be made to make this work. First, the bore size of the 16DP gears is .750" so they'd all have to bushed and re-broached. Easy enough. The second consideration was that the tooth face width of the gears is a little narrower than the imperial gears at 1/2", also not a major problem considering the light loads generally associated with thread cutting, especially in aluminum.

The next issue, what gears to acquire? I only needed to cut some 1.0 pitch metric threads for the Honda bike project but I decided that if I was going to make the effort that I'd like to cover a range of pitches so perhaps a partial set but certainly not a full set...

In consulting the photo of the original 13" SBL gear/tumbler selection plate Gene had sent and shown below, I decided to acquire the following gears in addition to the required 120/127T and 64T gears to be able to cut the following pitches:

28T for .35, 1.75, 3.5
32T for 1.0, 2.0
40T for 1.25, 2.5
48T for 1.50, 3.00

..so 7 gears in all.

GP CHART.jpg

Next step of course was where to source the gears. eBay was a natural choice and it did turn up some results but a Google search turned up Amazon (!) as a source so what the hey, right? I did some price comparisons between eBay and Amazon for NIB gears with Amazon always coming out cheaper for the required Boston Gear gears.

In the end, I sourced all the gears I needed save one from Amazon. The 64T 16 DP used Browning came from eBay, and it required the machining of a bolt-in hub.

Not all of you will agree with my having tig welded my bore reducer sleeves in but I'm ok with that. The re-broaching was going to cut through the sleeves anyway.
I pinned the 120T to the 127T with spring pins and that method is a little 'quick and dirty' but it's spring now this bike has to get out of my shop(!) and I'll redo that if ever I have to.

So, the the answer to the question you obviously all have or you wouldn't have read this far... the cost for the acquired gears was as follows, shipping included :

120T Boston gear part no. GB120A Amazon 89.50$
127T Boston gear part no. GB127A Amazon 94.30$
28T Boston gear part no. GB28 Amazon 43.75$
32T Boston gear part no. GB32 Amazon 47.68$
40T Boston gear part no. GB40 Amazon 47.68$
48T Boston gear part no. GB48B Amazon 63.93$
64T Browning gear part no. NCG-1664 eBay 34.65$

Partial set total: 421.49$

Although admittedly this is not a complete metric set, the beauty of this approach is that if you acquire the essential 120/127 and 64 lower QCGB gears, you can acquire the stud gears one at a time as you need them for your particular metric project's thread pitch requirements thereby allowing you to avoid the "sticker shock" of acquiring of a full set all at once.

I hope this info helps someone expand the usefulness of their SBL!, still a lot of machining left in these ol' girls...

...and thanks again to Gene Poole for his help with this project!

Thanks
Mark
MontrealIMG_4318.jpgIMG_4321.jpgIMG_4342.jpgIMG_4324.jpg
 
Hi Mark, great post.
I'm in the same boat here in Canada as I keep running into metric threads. Can't find any (NOS)Metric Transposing Gears for the SB 13".
Looks like your method will be my only option unless someone has a set for sale.

I haven't pulled my Imperial gears off yet, but would like to know the SB shaft OD and the ID of this bushing if you had bought one.
Boston Gear GBB16A Bushing: Amazon.com: Industrial & Scientific

Did you just line up the 127/120 gears with that bushing?
 
Cheap way to acquire a metric transposing set would be to buy those cheap 1.5 Mod gears off eBay....I wont tell if you won't.:)

ps- I can't remember if this was the seller but a while back I bought a few gears from such a vendor and they actually responded to my request for a quote including shipping for a mess of gears....gears were not great quality but we're not bad either, plenty good for what I needed.

Example-

1.5Mod 12T 45# Steel Motor Spur Gear Outer Diameter 183mm Thickness 15mm Qty 1 | eBay
 
Interesting and the price would be right.
I could ask the seller if they make a 127T gear so all the pitch diameters mesh or does it matter if they don't?
The gear you posted doesn't state PD.
 
1.5 Mod is the pitch....it's the metric equivalent to "roughly" 16DP ( to convert is 25.4/16 )...as long as they all match the lathe doesn't care.

Send them a message...I have seen them list 127 too...

Ask for a price with shipping for 127,120,64,48,44,40,32,28,26 gears.( I think that all of them)

You will only need to bore and key them.

If you ask let us know what reply you get.

Edited to correct...120T gear
 
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Thanks for that.
I sent off a question for the 127T. Will update on it.
I believe I need the 127/120 Idler because I have a 6 TPI lead screw.

*Update*
Out of stock with the 127T gear. Asked when and if they would restock. Still waiting on that.
 
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Just found out they did not make 127T gear nor intend to in 1.5Mod.
So far my options are the Boston Gear 127T and all the rest with the eBay gears for the best price.
 
Bummer...can you,make 1 MOD work?? That's actually what I bought.. Those are available in ALL tooth count and cheap too..,the 127 would only be about 5" diameter though...not sure if that could work??

Do consider form member Zahnrad Kopf....good guy...if you let him know what you need he can sometimes work with you and make your gears when he is set up for 16DP to keep the cost down...and that would be first rate hobbed gears too, in the 5/8" face width and the proper bore and key....I hate to speak for him but I bet his price would not be out of line with trying to piece a set together and certainly much less hassle.
 
Hi Mark, great post.
I'm in the same boat here in Canada as I keep running into metric threads. Can't find any (NOS)Metric Transposing Gears for the SB 13".
Looks like your method will be my only option unless someone has a set for sale.

I haven't pulled my Imperial gears off yet, but would like to know the SB shaft OD and the ID of this bushing if you had bought one.
Boston Gear GBB16A Bushing: Amazon.com: Industrial & Scientific

Did you just line up the 127/120 gears with that bushing?

Hi,

Yes I did buy the bushing but did not use it in the end, it is the wrong ID for our application and it is expensive.

When you remove the 80T gear in the imperial set, you will see it has an OEM hardened South Bend bushing already in it.

This bush is the same OD as the ID of the Boston 120/127 pair, .750" if I recall correctly. Only thing then required is to pin the 120/127 pair together.

To do this, I just put both the 120 and 127 on this bushing to align their centers and then cross drilled them while they were on the bushing and tapped in three 3/16" spring pins.

I then made up a couple aluminum spacer rings to get the 120/127 gear pair to align with everything else.
Works like a charm.

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Hi Mark, great post.
I'm in the same boat here in Canada as I keep running into metric threads. Can't find any (NOS)Metric Transposing Gears for the SB 13".
Looks like your method will be my only option unless someone has a set for sale.

I haven't pulled my Imperial gears off yet, but would like to know the SB shaft OD and the ID of this bushing if you had bought one.
Boston Gear GBB16A Bushing: Amazon.com: Industrial & Scientific

Did you just line up the 127/120 gears with that bushing?

Hi I did buy the bush but in the end you don't need it.
There is a hardened bush on the idler 80T gear that is a perfect fit in the 120-127 gear pair so all you have to do is put both gears on this bush, pin them together and makeup a couple of alum spacers to align the 120/127 idler with the rest of the gear train and you're done.

I put both the 120 and 127 on this bush and cross drilled and pinned them together with three 3/16" spring pins.
 

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Hi I did buy the bush but in the end you don't need it.
There is a hardened bush on the idler 80T gear that is a perfect fit in the 120-127 gear pair so all you have to do is put both gears on this bush, pin them together and makeup a couple of alum spacers to align the 120/127 idler with the rest of the gear train and you're done.

I put both the 120 and 127 on this bush and cross drilled and pinned them together with three 3/16" spring pins.
I see where you went with that. Nice job.
Managed to get all the stud gears except the 48T from eBay, but will still be looking at getting the 127/120 idlers and the 64T, lead gear made up.
Thanks
 








 
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