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C to B 9" workshop conversion.
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john kling
Varying accuracy are claimed for different models of SB lathes lead screws. Also the different suppliers of acme stock makes assertions about high accuracy. What is involved and how is accuracy measured for threads? I guess I am asking for some one to put on a pedogogue's hat.
From: "armne@..." To: "southbendlathe@..." Sent: Saturday, November 2, 2013 1:27 PM Subject: Re: [southbendlathe] Re: C to B 9" workshop conversion. Thank you Jim, I have cut acme threads to fit a worm amce cast iron nut on my tail stock. Alec Ryals From: Jim B. To: southbendlathe@... Sent: Saturday, November 2, 2013 8:41 AM Subject: RE: [southbendlathe] Re: C to B 9" workshop conversion. [2 Attachments] Steve Wells has some very special, accurate
and polished 7/16-10 LH stock for rebuilding cross feeds.
The compound is 3/8-10 RH
You can find accurate stock for that here.
http://www.roton.com/
MSC also carries some stock but they are
expensive.
Here is some leadscrew rod.
http://www.mscdirect.com/product/01206184
Of course you can roll your own. You only
need some rod and to grind an ACME threading tool.
I have made some for my Burke Mill in/out
feed and its been good for 5 years now.
This also gives you the ability to “fit”
the thread to a worn nut.
Jim B.
.
Were do I buy accurate amce thread stock.
Thank You Alec
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Flash Gordon
John,
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You are correct. SB did claim that the lead screw on a tool room lathe was of higher quality then on a standard lathe. But the conversation is about the acme screw for the cross feed. I do not think SB made any claims for different quality in that area. If anyone were to change that screw they would also need to change the nut to match. The nut is very small and does wear out. As Jim B pointed out if one were to make their own cross slide screw they could turn it to match the nut that have in hand. Ed S
At 08:15 PM 11/2/2013, you wrote:
Varying accuracy are claimed for different models of SB lathes lead screws.
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Steve Wells
toggle quoted messageShow quoted text
John, if you are referring to the apron lead screw,
there were three specs: standard; tool room and military. the military spec
being the best.
these were sorted as they were ran in production.
If you are referring to the 7/16 LH acme for the cross feed, the normal (old
way) was measurement over 3 wires to an SBL internal spec for back lash with the
nut and or assembly. On a 7/16 acme you would use .05164 wires
and the internal spec was .451 +.000 and
-.003. So .003 backlash was allowed. The stock for the screw on a non ground crossfeed was turned to
.4375/.4370. on a ground screw, the turn was .4475/.4455 and then ground to
.4375/.4370. South bend didn't use a standard Q9000
screw standard such as 4G or 5G (rub fit) the screw
fell in-between those numbers but was listed on the control sheets as
4G.
A 3G screw if roll threaded will make it into the
back lash specs just fine. My screw material is roll threaded 3G, and I'm
almost out of stock, but I will soon be running the original South bend
automatic screw machine that made these cross
feed screws, I have the only one left from the factory thanks to Ted. and I have
it running, but need to set up the collet for the blank stock and set the cutter
blocks up, I have the finish tool block done, I need to do the rougher bit
now. Just takes a lot of time...
Steve Wells
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john kling
Thanks for the information. I am trying to approach this with my own attempt of order. My first step is acquisition of the A and B apron. The cross feed screws seem to be a bottleneck as well. I have what I believe is a model 415 (single arm banjo and top oilers). I assume there is no additional problems here. When one has excess backlash (I do not have this problem) is the greater problem of wear normally found in the bronze "nut" or in the steel screw?
From: Steve Wells To: southbendlathe@... Sent: Sunday, November 3, 2013 3:55 PM Subject: Re: [southbendlathe] Re: C to B 9" workshop conversion.
John, if you are referring to the apron lead screw,
there were three specs: standard; tool room and military. the military spec
being the best.
these were sorted as they were ran in production.
If you are referring to the 7/16 LH acme for the cross feed, the normal (old
way) was measurement over 3 wires to an SBL internal spec for back lash with the
nut and or assembly. On a 7/16 acme you would use .05164 wires
and the internal spec was .451 +.000 and
-.003. So .003 backlash was allowed. The stock for the screw on a non ground crossfeed was turned to
.4375/.4370. on a ground screw, the turn was .4475/.4455 and then ground to
.4375/.4370. South bend didn't use a standard Q9000
screw standard such as 4G or 5G (rub fit) the screw
fell in-between those numbers but was listed on the control sheets as
4G.
A 3G screw if roll threaded will make it into the
back lash specs just fine. My screw material is roll threaded 3G, and I'm
almost out of stock, but I will soon be running the original South bend
automatic screw machine that made these cross
feed screws, I have the only one left from the factory thanks to Ted. and I have
it running, but need to set up the collet for the blank stock and set the cutter
blocks up, I have the finish tool block done, I need to do the rougher bit
now. Just takes a lot of time...
Steve Wells
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Steve Wells
toggle quoted messageShow quoted text
The stack up height of the A/B apron for the cross
feed was set with the apron cross feed gear they are marked M for
minus and P for plus, a common line card listing would be M 10 for minus .010
The cross feed nut should wear first by design, but
after many years the screw can wear in the center and you can expect to
have to replace the nut and screw if backlash is over 10 to 20 K. I would
replace the nut first and inspect the screw and if you can see sharp threads or
measure wear, replace the screw threads. It's not difficult to do either and you
refit everything and you will probably never do it again if it's oiled and
maintained.
Steve Wells
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Gregg Eshelman
On 11/3/2013 1:55 PM, Steve Wells wrote:
Would a 9" originally purchased by the corps of engineers in 1952 be military spec?
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Gregg Eshelman
On 11/3/2013 2:06 PM, john kling wrote:
This guy makes new ones. http://www.millermachineandfabrication.com/products.html The slide screws also differ depending on if the lathe has large or small dials. Yours should have the small dials, but there are upgrade kits to the large dials South Bend had starting in the later 1950's. Yet another change around then was adding a small radial ball bearing on the cross slide screw so it'd turn smoother and wouldn't wear the end of the bushing. Take some photos and measurements of your cross slide screw, send to Miller and say you want one like it with the power feed gear added.
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john kling
With say a cylinder it easy for me to think of some simple measurement say with a dial gauge to determine accuracy. How is accuracy specified for a lead screw? I am not a machinist but a statistician/ economist by training.
From: Gregg Eshelman To: southbendlathe@... Sent: Sunday, November 3, 2013 10:24 PM Subject: Re: [southbendlathe] Re: C to B 9" workshop conversion. On 11/3/2013 1:55 PM, Steve Wells wrote:
> > > John, if you are referring to the apron lead screw, there were three > specs: standard; tool room and military. the military spec being the best. Would a 9" originally purchased by the corps of engineers in 1952 be military spec?
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Steve Wells
toggle quoted messageShow quoted text
Ted could answer that, but I think Goverment would
be the same, yes.
Steve
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Steve Wells
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John, a lead screw is measured in moving and object
a set distance compared to a know measurement.
Lets say we could move your cross feed 12 inches
exactly by the dial, then compare the distance moved to a
12 in gauge block. the error in the lead screw is
compared to the gauge or indicator, then stated as accuracies
in x inches, such as + or - .003 in 12
inches.
Steve
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sblatheman
Machines for the military were usually made to the tight specs. I can't say if a 9" in 1952 was made to Govt. specs. Perhaps that information is on the serial card. Ted
On Nov 3, 2013, at 10:33 PM, "Steve Wells" <wswells@...> wrote:
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john kling
So far I have not found an a or B crossfeed screw. I follow your clear discussion of replacing the threaded portion of a cross feed screw. Would cutting a C screw and splicing in the gear work in a similar fashion.? Somewhere I read that as much as 1/2 '' might need to milled in fitting the a/b apron to the c saddle. The parts have not yet arrived so
I am not sure with what I am dealing with - but this really sounds extreme.
From: Steve Wells To: southbendlathe@... Sent: Sunday, November 3, 2013 3:55 PM Subject: Re: [southbendlathe] Re: C to B 9" workshop conversion.
John, if you are referring to the apron lead screw,
there were three specs: standard; tool room and military. the military spec
being the best.
these were sorted as they were ran in production.
If you are referring to the 7/16 LH acme for the cross feed, the normal (old
way) was measurement over 3 wires to an SBL internal spec for back lash with the
nut and or assembly. On a 7/16 acme you would use .05164 wires
and the internal spec was .451 +.000 and
-.003. So .003 backlash was allowed. The stock for the screw on a non ground crossfeed was turned to
.4375/.4370. on a ground screw, the turn was .4475/.4455 and then ground to
.4375/.4370. South bend didn't use a standard Q9000
screw standard such as 4G or 5G (rub fit) the screw
fell in-between those numbers but was listed on the control sheets as
4G.
A 3G screw if roll threaded will make it into the
back lash specs just fine. My screw material is roll threaded 3G, and I'm
almost out of stock, but I will soon be running the original South bend
automatic screw machine that made these cross
feed screws, I have the only one left from the factory thanks to Ted. and I have
it running, but need to set up the collet for the blank stock and set the cutter
blocks up, I have the finish tool block done, I need to do the rougher bit
now. Just takes a lot of time...
Steve Wells
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Gregg Eshelman
On 11/8/2013 6:01 PM, john kling wrote:
Just buy one from this guy. http://www.millermachineandfabrication.com/ Better than new, far easier than cutting and splicing old parts, and the prices are decent.
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armne@sbcglobal.net <armne@...>
The Lord is a strong hold in the Day of trouble, and he knoweth them that trust in him )(
From: "armne@..." To: "southbendlathe@..." Sent: Saturday, November 9, 2013 1:34 AM Subject: Re: [southbendlathe] Re: C to B 9" workshop conversion. Not to bad removing the .400 done in one pass on a Bridgeport. Alec From: john kling To: "southbendlathe@..." Sent: Friday, November 8, 2013 5:01 PM Subject: Re: [southbendlathe] Re: C to B 9" workshop conversion. So far I have not found an a or B crossfeed screw. I follow your clear discussion of replacing the threaded portion of a cross feed screw. Would cutting a C screw and splicing in the gear work in a similar fashion.? Somewhere I read that as much as 1/2
'' might need to milled in fitting the a/b apron to the c saddle. The parts have not yet arrived so
I am not sure with what I am dealing with - but this really sounds extreme. From: Steve Wells To: southbendlathe@... Sent: Sunday, November 3, 2013 3:55 PM Subject: Re: [southbendlathe] Re: C to B 9" workshop conversion.
John, if you are referring to the apron lead screw,
there were three specs: standard; tool room and military. the military spec
being the best.
these were sorted as they were ran in production.
If you are referring to the 7/16 LH acme for the cross feed, the normal (old
way) was measurement over 3 wires to an SBL internal spec for back lash with the
nut and or assembly. On a 7/16 acme you would use .05164 wires
and the internal spec was .451 +.000 and
-.003. So .003 backlash was allowed. The stock for the screw on a non ground crossfeed was turned to
.4375/.4370. on a ground screw, the turn was .4475/.4455 and then ground to
.4375/.4370. South bend didn't use a standard Q9000
screw standard such as 4G or 5G (rub fit) the screw
fell in-between those numbers but was listed on the control sheets as
4G.
A 3G screw if roll threaded will make it into the
back lash specs just fine. My screw material is roll threaded 3G, and I'm
almost out of stock, but I will soon be running the original South bend
automatic screw machine that made these cross
feed screws, I have the only one left from the factory thanks to Ted. and I have
it running, but need to set up the collet for the blank stock and set the cutter
blocks up, I have the finish tool block done, I need to do the rougher bit
now. Just takes a lot of time...
Steve Wells
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Steve Wells
toggle quoted messageShow quoted text
John, It depends on the year of the C saddle,
anything past 1938 and it should slide right in there.
with the A/B gear /handle blank and the acme blank
you can make a complete screw for $45.00
Steve
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john kling
You say past 1938 is unlikely to be a fitting problem. Is early 1938 not in the low problem group/set?
From: Steve Wells To: southbendlathe@... Sent: Saturday, November 9, 2013 9:13 PM Subject: Re: [southbendlathe] Re: C to B 9" workshop conversion.
John, It depends on the year of the C saddle,
anything past 1938 and it should slide right in there.
with the A/B gear /handle blank and the acme blank
you can make a complete screw for $45.00
Steve
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