# OOPS!  I really messed up.



## Mark_f (Aug 22, 2017)

Most of you know my work and many of my projects. I want you all to know, EVEN I SCREW THINGS UP NOW AND THEN! My friend has a South Bend 14 1/2" lathe and he wants me to help him put the large dial conversion on the cross side and compound. The cross slide lead screw for the conversion is almost 24" long. Way to big for my 36" bed South Bend 9. In this photo you can see the set up I had to use. There is a little more than 15" sticking out of the ER 40 collet. I had to use a dead center and leave half the tail stock hang off the bed to get it set up. I also had to move the QCTP to the other side.




I measured and checked and double checked everything. I then spent 5 HOURS cutting a 13 inch long acme lead screw on this end of the part. (Also it was over 90 degrees in the shop). I cut a perfect 11/16-10 acme screw but the nut wouldn't fit! Then I noticed , the screw is 11/16-8 acme thread.  Who in H**l would make a cross slide with 125 thousandths per revolution? We kept assuming it was 100 thousandths per revolution. My friend said "no wonder i always screw up cutting on this lathe!" After a lot of self loathing and severe disappointment I will start over and make a new lead screw. So ... to all those who followed my work ...... Yes, I screw things up too, and I do it big!



Edit: since I solved the taper problem on my lathe, there was less than .001" taper in 13" long cut.


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## jocat54 (Aug 22, 2017)

That's a bummer, sorry Mark,  but we know it will turn out perfect!


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## extropic (Aug 22, 2017)

I'm not familiar with the "normal" process for the conversion your friend is pursuing, but . . .
Why not use the screw you made and make a new nut to match?
If the large dial needs to be made anyway . . . easy enough to make them .100"/rev.
If the large dial is a purchased item and .125"/rev . . . Oh well.

At least you're out in the shop. No harm, no foul.


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## tertiaryjim (Aug 23, 2017)

This is the first 11/16 screw that I've heard of since I found my Rhodes shaper has one 11/16"-10. Seems like an odd size.
I once cut a 17" long  5/8"- 10TPI screw  and had trouble with deflection. Don't have a follow rest yet.
Had to make a couple of laps to clean the thread up.
A 8TPI lead screw would be rather unexpected but as EX said just make the dial and nut to match and the feed will be 
just a bit more accurate and more sensible.
Thats if your friend won't mind having a lathe with the modification.


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## Tozguy (Aug 23, 2017)

Mark, you are in good company so don't beat yourself up too bad. I too get reminders every so often that ''experience is what you get when you don't get what you want''.  That is still good work you are doing.


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## RandyM (Aug 23, 2017)

Yup Mark, everyone gets a reminder of who we are occasionally.


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## Mark_f (Aug 23, 2017)

I don't think there are any write ups for the large dial conversion like for the 9 and 10 inch South Bend lathes we are flying by the seat of our pants here. I am using the 9 inch conversion and scaling it up for the 14 1/2 inch lathe. The new cross slide dial will be 3" diameter and the compound dial will be 2 1/2" diameter. I never understood why South Bend used such small dials.


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## Dave Paine (Aug 23, 2017)

As you said, a big "oops".  I have had my share.  A good reminder to check/measure and not assume.


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## Mark_f (Aug 23, 2017)

What is really bad is I measured the pitch between the teeth and got .125" which would be 8 TPI, but I just kept working with .100"/rev. I just cant figure why they would build it with .125"/ rev. I wonder if all the big SB lathes are that way?


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## Ken from ontario (Aug 23, 2017)

“If gold rusts, what then can iron do?” 
― Geoffrey Chaucer, The Canterbury Tales


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## Technical Ted (Aug 23, 2017)

I've got a 1935 15"x6' SB and it's cross feed dial is .125" per revolution. I made a new nut and screw for it years ago when I first got it because they were worn pretty badly. Luckily, I checked the lead before starting!  Mine had a gear on it and rather than make a new shaft with gear I bored the original out and pressed & pinned a new acme threaded screw into it. This worked out well because the rest of the shaft/gear/bearing surfaces were in good shape. 

Ted


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## Technical Ted (Aug 23, 2017)

Since you're making new dials anyways, can't you just make a new nut as well and use the screw you just made? Just a thought... Threading an acme nut on your lathe that size wouldn't take long and then everything would be new!

Edit: of course this would throw off you power cross feed some, but that shouldn't make too much difference.

Ted


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## Mikebr5 (Aug 23, 2017)

mark_f said:


> I then spent 5 HOURS cutting a 13 inch long acme lead screw on this end of the part. (Also it was over 90 degrees in the shop). I cut a perfect 11/16-10 acme screw but the nut wouldn't fit!


You have a well-made acme lead screw for building a brand new machine around.
Looking forward to the build.


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## Bamban (Aug 23, 2017)

Not nearly as bad as when I did a fireforming barrel for my brother's bench rifle. I cut the tenon, threaded it, could not get the receiver to screw. Lopped off the tenon and cut another one, still would not screw in, then I had to sit back and think about it, read the print again, 1 1/16 x 18. I had the diameter correct, somehow I was fixated on 16 and the fact that I do mostly AR barrels, which are 16 TPI, I automatically set the gear box to 16.

Well, 18 TPI receiver will not screw on a 16 TPI tenon.

It was rather embarassing as he watched me the whole time.


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## f350ca (Aug 23, 2017)

I've had those OPPS too Mark. Would they have went with 8 TPI to get the cross feed at 1/2 the longitudinal feed.

Greg


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## woodchucker (Aug 23, 2017)

extropic said:


> I'm not familiar with the "normal" process for the conversion your friend is pursuing, but . . .
> Why not use the screw you made and make a new nut to match?
> If the large dial needs to be made anyway . . . easy enough to make them .100"/rev.
> If the large dial is a purchased item and .125"/rev . . . Oh well.
> ...


I think this is a spot on recommendation, and corrects a flaw in the original design. Mark consider it. It's easy enough to make a tap to do one critical tapping operation of the nut.


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## Downwindtracker2 (Aug 23, 2017)

I'm working on a '50s  shop built 6" shaper, they used 1/2" x13 for the feed screw and 3/8" x 16 for the clapper box feed screw. How's that for odd. Obviously, it didn't have dials.  I picked up a 50 and 100 dials at Grizzly and will use 1/2 x10 Acme and 7/16 UNF.


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## Mark_f (Aug 23, 2017)

We have decided to make the large dial conversion .100"/rev. This makes more sense. I would hate to have .125"/rev. I did some checking and it seems South Bend made all or most of the bigger lathes this way, why I don't know. I know it will result in a little slower cross feed,but that can be solved by the QCGB so I don't see that as a problem. We are making everything from scratch. To my knowledge this has not been done or no one has done a write up on it. I could find noting on the net. So we are redesigning and making all the parts. I will post the results as we get the parts made.


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## T Bredehoft (Aug 24, 2017)

Machines were made to be improved upon. In this case the original engineers didn't have to run the machine, they were thinking in fractions, we think in thous. Go ahead and make it right.


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## uncle harry (Aug 24, 2017)

T Bredehoft said:


> Machines were made to be improved upon. In this case the original engineers didn't have to run the machine, they were thinking in fractions, we think in thous. Go ahead and make it right.



My early vintage mill/drill has an eighth in/turn screw as well.  Moving between it and my BP knock off Tiawan mill is confusing some days.


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## Mark_f (Aug 24, 2017)

We are putting a 3" dial on the cross slide and a 2 1/2" dial on the compound. The cross slide dial originally extended 11/4"  from the cross slide. The new 3" dial will extend 2 1/2" . This will allow full travel of the cross slide. 

The original cross slide dial was .125 /rev and the compound was .100/rev. They will both be .100/rev when finished and MUCH EASIER to read.

I dont know about anyone else, but when you use the dials ( I can't afford DROs) I get easily confused when I pass zero and then you have to start calculating to allow for that odd .025 and it is easy to mess up.
For example if you want to move .150, you have to pass zero and stop on .025. instead of .050. you have to add in your head for the next move.


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## RandyWilson (Aug 24, 2017)

And here I thought it was just me finding the .125 a bit odd. I'm still too green and timid to be lopping off such large chunks. Small cut and measure, small cut and measure, so dealing with the extra .025 hasn't been a big deal.

The only thing to watch is your power crossfeed speeds will be 20% lower than published.


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## Technical Ted (Aug 24, 2017)

I think "comfortable" dial gradations are just what you're used to... No DROs in my shop either. On my 15" SB the cross feed is .125" per rev, but the compound is .100" per rev. On my Brown and Sharpe 2B horizontal mill, the table X is .250" per rev, but the Y and Z are .100 per rev. I don't remember what the machines at work used to be. Using dials, taking the backlash out when making movements and doing things the old fashion way are my standard operating procedures and I'm very comfortable with them!

So, I guess I've just gotten comfortable with being uncomfortable! 

YMMV,
Ted


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## epanzella (Aug 27, 2017)

Won't the new lead screw pitch screw up your threading? You may not be able to get all the common pitches without buying/making conversion gears.


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## epanzella (Aug 27, 2017)

epanzella said:


> Won't the new lead screw pitch screw up your threading? You may not be able to get all the common pitches without buying/making conversion gears.


Nevermind, I just noticed it was the cross slide lead screw.


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## Mark_f (Aug 27, 2017)

epanzella said:


> Nevermind, I just noticed it was the cross slide lead screw.


It will however slow the cross slide feeds about 20% slower, which is not a problem. The feed rate can be adjusted to compensate if needed. It wont matter since this is not a production environment.


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## loggerhogger (Oct 3, 2017)

mark_f said:


> Most of you know my work and many of my projects. I want you all to know, EVEN I SCREW THINGS UP NOW AND THEN! My friend has a South Bend 14 1/2" lathe and he wants me to help him put the large dial conversion on the cross side and compound. The cross slide lead screw for the conversion is almost 24" long. Way to big for my 36" bed South Bend 9. In this photo you can see the set up I had to use. There is a little more than 15" sticking out of the ER 40 collet. I had to use a dead center and leave half the tail stock hang off the bed to get it set up. I also had to move the QCTP to the other side.
> 
> 
> View attachment 240321
> ...


My Kerney & Treker milling machine has a couple of dials that are .125 per revolution. 

Sent from my SM-G930V using Tapatalk


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## 4GSR (Oct 4, 2017)

Mark,

If you still have that 11/16-10 pitch Acme threaded lead screw, I'm interested in buying it from you if it's left handed.

Ken


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## Mark_f (Oct 4, 2017)

4gsr said:


> Mark,
> 
> If you still have that 11/16-10 pitch Acme threaded lead screw, I'm interested in buying it from you if it's left handed.
> 
> Ken


Once I knew I made a mistake I didn't finish it. I think I threw it out. I will look.


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