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9" South Bend Cross Feed Screw

wk2hons

Plastic
Joined
Oct 15, 2018
I am looking for a cross feed screw for a 9" south bend lathe model A. serial #145758 with power cross feed. must be in good condition without much backlash.
 
I have looked on E-bay and found just the threaded portion without the gear. He says he press fits them together. Not sure I like that option. I would have to see the threaded portion and would like to see how it is supposed to press into the portion with the gear.
 
replacing the ACME portion is actually pretty easy and a nice little project that covers basic set up+ turn/face/drill/bore operations.
Just gotta lock down the crosslide and use the compound...no biggie since the facing cuts are so short.

as for the securing of the new ACME if you simply make it a nice sliding fit into the geared portion and use loctite #680 it will last at least as long as it takes to wear out the new ACME.

ps- the geared portion on the 9" is ~.685"ish diameter....a slick way of holding it very accurately without damage and having no other means is to chuck up a piece of scrap ~3/4" or so and drill/bore it to a tight sliding fit then simply insert the geared portion and tighten the chuck a little more...basically an in-situ collet.
With the tight sliding fit even without slitting the "collet" will compress enough to firmly grip the part...and is very convenient since the entire job can be done in that single chucking...same method can be used to grip the new ACME when you turn down the end to 5/16" or so...just be sure to prepare the ACME section first as it will be your gage to do the geared portion.
 
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replacing the ACME portion is actually pretty easy and a nice little project that covers basic set up+ turn/face/drill/bore operations.
Just gotta lock down the crosslide and use the compound...no biggie since the facing cuts are so short.

as for the securing of the new ACME if you simply make it a nice sliding fit into the geared portion and use loctite #680 it will last at least as long as it takes to wear out the new ACME.

ps- the geared portion on the 9" is ~.685"ish diameter....a slick way of holding it very accurately without damage and having no other means is to chuck up a piece of scrap ~3/4" or so and drill/bore it to a tight sliding fit then simply insert the geared portion and tighten the chuck a little more...basically an in-situ collet.
With the tight sliding fit even without slitting the "collet" will compress enough to firmly grip the part...and is very convenient since the entire job can be done in that single chucking.



The gear section on my 10L screw, which I think uses the same 12-tooth 20DP gear as the 9", is 0.700" exactly which is correct for the gear profile. I just made a complete new screw for my heavy 10.
 
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The gear for the 9" is kind of a stub form of a 20DP 12T gear.
the 10L uses a straight up 20DP x 14.5PA gear, and yes, is .700" diameter.
 
Yeah sorry I meant 20DP not 12DP. Do we know how the gear is modified on the 9" - is it profile-shifted down 7 thou?
 
The 9-10 NK gear blank OD is 0.683 - 0.6825, the 10L is 0.7005 - 0.700, both measure 0.7072 +- 0.001 over 0.084 wires. If you take the 0.100 cut on the 9, you may likely be too deep. Mine run around 0.0965.

Steve
 
The 9-10 NK gear blank OD is 0.683 - 0.6825, the 10L is 0.7005 - 0.700, both measure 0.7072 +- 0.001 over 0.084 wires. If you take the 0.100 cut on the 9, you may likely be too deep. Mine run around 0.0965.

Steve


So they just topped the gear to clear the 3/4" x 16tpi thread ID? On the 10L they increased the thread OD so the .700" gear would just clear through. two different ways to skin a cat but I wonder why they did it?
 
I'm also getting ready to run some acme repair blanks over the weekend, the blanks are 24.95 plus 6.50 priority shipping. I have 20 new (NOS) south bend 65NK1 feed nuts for 45.00 each to go with the blanks.
These blanks are made on the South Bend factory automatic feed screw machine to SBL specs.

Steve
 
The 10L saddle (and other parts) were improved revisions of the O, R and T series letter lathes, by the 2 or third revision of the O series saddle, the mount bushing threads were the 25/32 16tpi. that ran all the way to final 10L S series. The early Workshop series used 3/4 16tpi and when the B and A series were designed the feed gear pinion would not fit in the early 15 saddles, so they relieved some of the inner casting and turned down the 700 gear to 683.

Steve
 
I repaired one of my 9" lathes cross feed screw a long time ago by using the acme screw. Used red locktite and then cross pinned it, that was back in 2006 or so, I use my lathe a lot and it has never failed. Getting ready to do another lathe in the next month or so.
 
I'm also getting ready to run some acme repair blanks over the weekend, the blanks are 24.95 plus 6.50 priority shipping. I have 20 new (NOS) south bend 65NK1 feed nuts for 45.00 each to go with the blanks.
These blanks are made on the South Bend factory automatic feed screw machine to SBL specs.

Steve

how would one contact you to purchase one of these acme repair blanks?
 








 
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