Topics

Internal threading woes


trackthatpot2000
 

I’m making a batch of cast iron lead screw nuts for a repair job ... these are an odd size and and no taps exists ..so I’m doing them with a boring bar the hard way with a sample short leadscrew used as a gauge ..but I’m having a bit of trouble making the  threads parallel....the thread size 9/16 x18 TPI  x 40 mm deep and I’m getting a slight taper making them tight at the rear end ...any tips would be welcome.


engmaxx
 

9/16-18 is a common size tap.  I would thread chase with one.  That said, your bar is likely deflecting at the end so you may correct it with a few spring passes and be sure your tool is sharp.


On Tue, Jan 19, 2021 at 11:47 AM trackthatpot2000 <timmsken@...> wrote:
I’m making a batch of cast iron lead screw nuts for a repair job ... these are an odd size and and no taps exists ..so I’m doing them with a boring bar the hard way with a sample short leadscrew used as a gauge ..but I’m having a bit of trouble making the  threads parallel....the thread size 9/16 x18 TPI  x 40 mm deep and I’m getting a slight taper making them tight at the rear end ...any tips would be welcome.


Steve Wells
 

Drill undersize,
bore undersize,
ream to minor diameter for class fit (.502 ??).
Make sure your drill, boring bar and reamer are parallel,
check them with an indicator.
Use spring passes to obtain final fit.
 
Steve
 

From: engmaxx
Sent: Tuesday, January 19, 2021 11:52 AM
To: SouthBendLathe@groups.io
Subject: Re: [SouthBendLathe] Internal threading woes
 
9/16-18 is a common size tap.  I would thread chase with one.  That said, your bar is likely deflecting at the end so you may correct it with a few spring passes and be sure your tool is sharp.
 
On Tue, Jan 19, 2021 at 11:47 AM trackthatpot2000 <timmsken@...> wrote:
I’m making a batch of cast iron lead screw nuts for a repair job ... these are an odd size and and no taps exists ..so I’m doing them with a boring bar the hard way with a sample short leadscrew used as a gauge ..but I’m having a bit of trouble making the  threads parallel....the thread size 9/16 x18 TPI  x 40 mm deep and I’m getting a slight taper making them tight at the rear end ...any tips would be welcome.


m. allan noah
 

how thick is the wall of the nut? Are you testing for fit out of the chuck?

allan

On Tue, Jan 19, 2021 at 12:15 PM Steve Wells <wswells@earthlink.net> wrote:

Drill undersize,
bore undersize,
ream to minor diameter for class fit (.502 ??).
Make sure your drill, boring bar and reamer are parallel,
check them with an indicator.
Use spring passes to obtain final fit.

Steve

From: engmaxx
Sent: Tuesday, January 19, 2021 11:52 AM
To: SouthBendLathe@groups.io
Subject: Re: [SouthBendLathe] Internal threading woes

9/16-18 is a common size tap. I would thread chase with one. That said, your bar is likely deflecting at the end so you may correct it with a few spring passes and be sure your tool is sharp.

On Tue, Jan 19, 2021 at 11:47 AM trackthatpot2000 <timmsken@hotmail.com> wrote:

I’m making a batch of cast iron lead screw nuts for a repair job ... these are an odd size and and no taps exists ..so I’m doing them with a boring bar the hard way with a sample short leadscrew used as a gauge ..but I’m having a bit of trouble making the threads parallel....the thread size 9/16 x18 TPI x 40 mm deep and I’m getting a slight taper making them tight at the rear end ...any tips would be welcome.
--
"well, I stand up next to a mountain- and I chop it down with the edge
of my hand"


trackthatpot2000
 
Edited

I tried a 9/16 UNF Tap but the fit was way too sloppy...I think spring passes are the best bet ...it’s a repair kit for some sanding machines the undersize spindle was causing the nut threads to strip.


mike allen
 

        how long are the nuts ? you want to use the shortest boring bar you can & lock the  saddle. you may already know this .

        animal

On 1/19/2021 8:47 AM, trackthatpot2000 wrote:
I’m making a batch of cast iron lead screw nuts for a repair job ... these are an odd size and and no taps exists ..so I’m doing them with a boring bar the hard way with a sample short leadscrew used as a gauge ..but I’m having a bit of trouble making the  threads parallel....the thread size 9/16 x18 TPI  x 40 mm deep and I’m getting a slight taper making them tight at the rear end ...any tips would be welcome.


Steven H
 

Besides keeping the boring bar as short as possible, you want to use as large a boring bar as possible to minimize deflection. Obviously, 9/16” does not allow for that large of a bar. Spring passes. Or a solid carbide boring bar. Good luck.

Steve Haskell

On Jan 19, 2021, at 1:00 PM, mike allen <animal@...> wrote:



        how long are the nuts ? you want to use the shortest boring bar you can & lock the  saddle. you may already know this .

        animal

On 1/19/2021 8:47 AM, trackthatpot2000 wrote:
I’m making a batch of cast iron lead screw nuts for a repair job ... these are an odd size and and no taps exists ..so I’m doing them with a boring bar the hard way with a sample short leadscrew used as a gauge ..but I’m having a bit of trouble making the  threads parallel....the thread size 9/16 x18 TPI  x 40 mm deep and I’m getting a slight taper making them tight at the rear end ...any tips would be welcome.


eddie.draper@btinternet.com
 

Does your lathe normally bore sufficiently parallel plain holes from the saddle position you are using? If not, there is no hope for boring a parallel thread without some nerve wracking manual cross slide adjustment during the last pass.


If your lathe is OK in this respect, are you absolutely certain that you are screwcutting tapered rather than suffering from a small pitch error? This cons you by allowing the gauge to enter easily and then progressively tighten when working to tight fits. A lathe leadscrew does not need to be very worn to start introducing pitch error as the amount of wear varies along the leadscrew. Also, if you are set up to produce an approximate Imperial pitch on a metric leadscrew (or v v) then long threads to close clearances should be avoided.


Finally, are you sure there isn't a pitch error or taper (for all the same reasons) on the thread you are using as a gauge? If the OEM could make them undersize so the nuts strip, then anything is possible.


Eddie






------ Original Message ------
From: "trackthatpot2000" <timmsken@...>
To: SouthBendLathe@groups.io
Sent: Tuesday, 19 Jan, 21 At 17:46
Subject: Re: [SouthBendLathe] Internal threading woes

I tried a 9/16 UNF Tap but the fit was way too sloppy...I think spring passes are the best bet here is a pic of the job so far .....
it’s a repair kit for some sanding machines the undersize spindle was causing the nut threads to strip.
[url=https://flic.kr/p/DfjHkg][img]https://live.staticflickr.com/4635/24447282417_d4abc4f775_c.jpg[/img][/url][url=https://flic.kr/p/DfjHkg]repair kit 2[/url] by [url=https://www.flickr.com/photos/150702140@N02/]Ken Timms[/url], on Flickr


eddie.draper@btinternet.com
 

A further thought: Sounds daft, I know, but are you sure you are dealing with UNF here?


9/16" translates to 14.2875mm, and you say the male threads are a bit undersize, so possibly 14mm?


18 tpi translates to 1.41111 mm pitch.


14mm fine standard is 1.5mm pitch.


Close? Pitch error as in my earlier response?


Eddie




------ Original Message ------
From: "mike allen" <animal@...>
To: SouthBendLathe@groups.io
Sent: Tuesday, 19 Jan, 21 At 18:00
Subject: Re: [SouthBendLathe] Internal threading woes

how long are the nuts ? you want to use the shortest boring bar you can & lock the saddle. you may already know this .

animal

On 1/19/2021 8:47 AM, trackthatpot2000 wrote:
I’m making a batch of cast iron lead screw nuts for a repair job ... these are an odd size and and no taps exists ..so I’m doing them with a boring bar the hard way with a sample short leadscrew used as a gauge ..but I’m having a bit of trouble making the threads parallel....the thread size 9/16 x18 TPI x 40 mm deep and I’m getting a slight taper making them tight at the rear end ...any tips would be welcome.


Glen Ruch
 

Is the stock 'thin?'


Could the chuck be deforming the stock?


Could the stock be reversed in the chuck?


Regards.


On 1/19/21 2:35 PM, eddie.draper@... via groups.io wrote:
A further thought: Sounds daft, I know, but are you sure you are dealing with UNF here?


9/16" translates to 14.2875mm, and you say the male threads are a bit undersize, so possibly 14mm?


18 tpi translates to 1.41111 mm pitch.


14mm fine standard is 1.5mm pitch.


Close? Pitch error as in my earlier response?


Eddie


------ Original Message ------ From: "mike allen" <animal@...> To: SouthBendLathe@groups.io Sent: Tuesday, 19 Jan, 21 At 18:00 Subject: Re: [SouthBendLathe] Internal threading woes

how long are the nuts ? you want to use the shortest boring bar you can & lock the saddle. you may already know this .

animal

On 1/19/2021 8:47 AM, trackthatpot2000 wrote:
I’m making a batch of cast iron lead screw nuts for a repair job ... these are an odd size and and no taps exists ..so I’m doing them with a boring bar the hard way with a sample short leadscrew used as a gauge ..but I’m having a bit of trouble making the threads parallel....the thread size 9/16 x18 TPI x 40 mm deep and I’m getting a slight taper making them tight at the rear end ...any tips would be welcome.


trackthatpot2000
 
Edited

No the stock is not thin it’s 1 inch cast iron rod....the thread pitch is definitely 18 TPI.....I’ve sorted the problem now , it was just a build up of fine cast iron dust as I screwed in the gauge...these repair kits I’m making are to rectify a problem with the “Jet-Performax 10-20” drum thickness sander there were hundreds sold world wide with a specific design problem where the rise and fall leadscrew was stripping out the aluminium nut which was way too thin and wrong material to hold the weight of the drum/motor assembly.
you can see a video of the fix here https://www.youtube.com/watch?v=RsmnY8dCODA


Ondrej Krejci
 

Howdy,

Stating that a nut made by tapping had too much slop may imply that the original nut of aluminium acted as a lap.  Cellulous fibres are quite abrasive.  Per standard machine building practices, the smaller member should be harder; i.e. a pinion gear is of hardened steel and the driven gear left soft or of cast iron.  May be nuts from air hardening steel would be more suitable?

Best wishes,


OK


eddie.draper@btinternet.com
 

"Air hardening steel"? To me that means high speed steel! A bit OTT, perhaps?


I feel that the combination of a steel screw and cast iron nut should be about the best economic solution. The one feature that sticks out in this design is why use UNF for a thread that is going to get a lot of use? I'm not sure about that statement, but the original question did describe it as a leadscrew. The coarser the better under those circumstances, and if you're not updating to metric, then use Whitworth. 12 tpi, and as a marginal added bonus, the thread is slightly deeper than a UN 12 tpi due to the 55 v 60 degree thread angle.


Agreed that a nut made of Aluminium can be abrasive if not protected from air by a layer of oil. Aluminium oxide (sapphire / ruby) is the second hardest material behind diamond, and is used for grinding tungsten carbide (green grit wheels). More likely that the male thread was just plain made undersize, which can happen if a diebox on a capstan lathe is misused (my apprentice school experience in 1973 - ahem).


I think we can agree that both original design and manufacture were unsound.


Eddie




------ Original Message ------
From: "Ondrej Krejci via groups.io" <okrejci@...>
To: "southbendlathe@groups.io" <southbendlathe@groups.io>
Sent: Thursday, 21 Jan, 21 At 09:17
Subject: Re: [SouthBendLathe] Internal threading woes

Howdy,

Stating that a nut made by tapping had too much slop may imply that the original nut of aluminium acted as a lap. Cellulous fibres are quite abrasive. Per standard machine building practices, the smaller member should be harder; i.e. a pinion gear is of hardened steel and the driven gear left soft or of cast iron. May be nuts from air hardening steel would be more suitable?

Best wishes,


OK


Bill in OKC too
 

Green grit wheels are silicon carbide, not aluminum oxide. Alox is the gray (or grey) wheel. A2 is an air hardening tool steel. My class has us make our first set of parallels for milling from ground-flat A2 stock. I've scavenged a number of pieces of that stock from the scrap dumpster. It's not HSS. There are a number of non-HSS tools steels that are air hardening. Though if you need a couple of thick parallels, a couple of HSS tool bits can work. ;)

I've also used Alox wheels to sharpen carbide tooling. It's not perfect, but it can work. ;) The first lathe tooling I ever bought was the cheap carbide from Harbor Freight. The carbide chips on those tools were not ground to have the cutting edge touch the workpiece first. I had to grind them to make them work. I've got a green wheel, but it's for a lapidary machine, and I didn't want to mess it up, so tried the Alox wheel. It worked. Best to use the right material, when you can, but "Improvise, adapt, and overcome." 

Bill in OKC

William R. Meyers, MSgt, USAF(Ret.)


A human being should be able to change a diaper, plan an invasion,
butcher a hog, conn a ship, design a building, write a sonnet, balance
accounts, build a wall, set a bone, comfort the dying, take orders,
give orders, cooperate, act alone, solve equations, analyze a new
problem, pitch manure, program a computer, cook a tasty meal, fight
efficiently, die gallantly. Specialization is for insects.
LAZARUS LONG (Robert A. Heinlein)





On Thursday, January 21, 2021, 03:34:29 AM CST, eddie.draper@... via groups.io <eddie.draper@...> wrote:


"Air hardening steel"? To me that means high speed steel! A bit OTT, perhaps?


I feel that the combination of a steel screw and cast iron nut should be about the best economic solution. The one feature that sticks out in this design is why use UNF for a thread that is going to get a lot of use? I'm not sure about that statement, but the original question did describe it as a leadscrew. The coarser the better under those circumstances, and if you're not updating to metric, then use Whitworth. 12 tpi, and as a marginal added bonus, the thread is slightly deeper than a UN 12 tpi due to the 55 v 60 degree thread angle.


Agreed that a nut made of Aluminium can be abrasive if not protected from air by a layer of oil. Aluminium oxide (sapphire / ruby) is the second hardest material behind diamond, and is used for grinding tungsten carbide (green grit wheels). More likely that the male thread was just plain made undersize, which can happen if a diebox on a capstan lathe is misused (my apprentice school experience in 1973 - ahem).


I think we can agree that both original design and manufacture were unsound.


Eddie




------ Original Message ------
From: "Ondrej Krejci via groups.io" <okrejci@...>
To: "southbendlathe@groups.io" <southbendlathe@groups.io>
Sent: Thursday, 21 Jan, 21 At 09:17
Subject: Re: [SouthBendLathe] Internal threading woes

Howdy,

Stating that a nut made by tapping had too much slop may imply that the original nut of aluminium acted as a lap. Cellulous fibres are quite abrasive. Per standard machine building practices, the smaller member should be harder; i.e. a pinion gear is of hardened steel and the driven gear left soft or of cast iron. May be nuts from air hardening steel would be more suitable?

Best wishes,


OK


david pennington
 

The shop where I was introduced to machining had a green wheel we used for carbide tooling.

In my home shop, I've had to improvise.

For hand touch-up I use a Lansky fine diamond "stone". For more extensive work, such as grinding beyond a small chip, I use a diamond wheel in a Dremel tool.


The discussion reminds me of a story from a restaurant manager I knew. 
The traditional method of making hollandaise sauce involves a hemispherical SS bowl over simmering water.
The manager walked into his kitchen one day to see the chef with said bowl at the deep fryer. 
"Herman, whatcha makin'?"
"Hollandaise"
"I thought you used a double-boiler for that."
"Don't have time for a double-boiler. Deep fryer works fine if you know what you're looking for."


David W. Pennington
Denver, Colorado
720-442-3744 - Please note the new number.


On Thursday, January 21, 2021, 08:35:24 AM CST, Bill in OKC too via groups.io <wmrmeyers@...> wrote:


Green grit wheels are silicon carbide, not aluminum oxide. Alox is the gray (or grey) wheel. A2 is an air hardening tool steel. My class has us make our first set of parallels for milling from ground-flat A2 stock. I've scavenged a number of pieces of that stock from the scrap dumpster. It's not HSS. There are a number of non-HSS tools steels that are air hardening. Though if you need a couple of thick parallels, a couple of HSS tool bits can work. ;)

I've also used Alox wheels to sharpen carbide tooling. It's not perfect, but it can work. ;) The first lathe tooling I ever bought was the cheap carbide from Harbor Freight. The carbide chips on those tools were not ground to have the cutting edge touch the workpiece first. I had to grind them to make them work. I've got a green wheel, but it's for a lapidary machine, and I didn't want to mess it up, so tried the Alox wheel. It worked. Best to use the right material, when you can, but "Improvise, adapt, and overcome." 

Bill in OKC

William R. Meyers, MSgt, USAF(Ret.)


A human being should be able to change a diaper, plan an invasion,
butcher a hog, conn a ship, design a building, write a sonnet, balance
accounts, build a wall, set a bone, comfort the dying, take orders,
give orders, cooperate, act alone, solve equations, analyze a new
problem, pitch manure, program a computer, cook a tasty meal, fight
efficiently, die gallantly. Specialization is for insects.
LAZARUS LONG (Robert A. Heinlein)





On Thursday, January 21, 2021, 03:34:29 AM CST, eddie.draper@... via groups.io <eddie.draper@...> wrote:


"Air hardening steel"? To me that means high speed steel! A bit OTT, perhaps?


I feel that the combination of a steel screw and cast iron nut should be about the best economic solution. The one feature that sticks out in this design is why use UNF for a thread that is going to get a lot of use? I'm not sure about that statement, but the original question did describe it as a leadscrew. The coarser the better under those circumstances, and if you're not updating to metric, then use Whitworth. 12 tpi, and as a marginal added bonus, the thread is slightly deeper than a UN 12 tpi due to the 55 v 60 degree thread angle.


Agreed that a nut made of Aluminium can be abrasive if not protected from air by a layer of oil. Aluminium oxide (sapphire / ruby) is the second hardest material behind diamond, and is used for grinding tungsten carbide (green grit wheels). More likely that the male thread was just plain made undersize, which can happen if a diebox on a capstan lathe is misused (my apprentice school experience in 1973 - ahem).


I think we can agree that both original design and manufacture were unsound.


Eddie




------ Original Message ------
From: "Ondrej Krejci via groups.io" <okrejci@...>
To: "southbendlathe@groups.io" <southbendlathe@groups.io>
Sent: Thursday, 21 Jan, 21 At 09:17
Subject: Re: [SouthBendLathe] Internal threading woes

Howdy,

Stating that a nut made by tapping had too much slop may imply that the original nut of aluminium acted as a lap. Cellulous fibres are quite abrasive. Per standard machine building practices, the smaller member should be harder; i.e. a pinion gear is of hardened steel and the driven gear left soft or of cast iron. May be nuts from air hardening steel would be more suitable?

Best wishes,


OK


Bill in OKC too
 

I've got a set of the EZE-Lap diamond hones, some diamond files, and diamond wheels for Dremel-type tools, plus the usual carborundum stones, and a fine Arkansas stone, and one square India stone I scavenged over 40 years ago. Every time I get a chance to snag something like that, I do it! Never can tell when you'll need something like that. Also have dozens of files, and a few rasps. Lots of ways to make what you need, if you have the tools. Including a well-loaded brain. May have to think about how to apply that story to producing steam, too. :) I have some stuff I need to steam, and several possible ways to do it. None of them are allowed in SWMBO's kitchen. ;)

Bill in OKC

William R. Meyers, MSgt, USAF(Ret.)


A human being should be able to change a diaper, plan an invasion,
butcher a hog, conn a ship, design a building, write a sonnet, balance
accounts, build a wall, set a bone, comfort the dying, take orders,
give orders, cooperate, act alone, solve equations, analyze a new
problem, pitch manure, program a computer, cook a tasty meal, fight
efficiently, die gallantly. Specialization is for insects.
LAZARUS LONG (Robert A. Heinlein)





On Thursday, January 21, 2021, 09:38:27 AM CST, david pennington via groups.io <davidwpennington@...> wrote:


The shop where I was introduced to machining had a green wheel we used for carbide tooling.

In my home shop, I've had to improvise.

For hand touch-up I use a Lansky fine diamond "stone". For more extensive work, such as grinding beyond a small chip, I use a diamond wheel in a Dremel tool.


The discussion reminds me of a story from a restaurant manager I knew. 
The traditional method of making hollandaise sauce involves a hemispherical SS bowl over simmering water.
The manager walked into his kitchen one day to see the chef with said bowl at the deep fryer. 
"Herman, whatcha makin'?"
"Hollandaise"
"I thought you used a double-boiler for that."
"Don't have time for a double-boiler. Deep fryer works fine if you know what you're looking for."


David W. Pennington
Denver, Colorado
720-442-3744 - Please note the new number.


On Thursday, January 21, 2021, 08:35:24 AM CST, Bill in OKC too via groups.io <wmrmeyers@...> wrote:


Green grit wheels are silicon carbide, not aluminum oxide. Alox is the gray (or grey) wheel. A2 is an air hardening tool steel. My class has us make our first set of parallels for milling from ground-flat A2 stock. I've scavenged a number of pieces of that stock from the scrap dumpster. It's not HSS. There are a number of non-HSS tools steels that are air hardening. Though if you need a couple of thick parallels, a couple of HSS tool bits can work. ;)

I've also used Alox wheels to sharpen carbide tooling. It's not perfect, but it can work. ;) The first lathe tooling I ever bought was the cheap carbide from Harbor Freight. The carbide chips on those tools were not ground to have the cutting edge touch the workpiece first. I had to grind them to make them work. I've got a green wheel, but it's for a lapidary machine, and I didn't want to mess it up, so tried the Alox wheel. It worked. Best to use the right material, when you can, but "Improvise, adapt, and overcome." 

Bill in OKC

William R. Meyers, MSgt, USAF(Ret.)


A human being should be able to change a diaper, plan an invasion,
butcher a hog, conn a ship, design a building, write a sonnet, balance
accounts, build a wall, set a bone, comfort the dying, take orders,
give orders, cooperate, act alone, solve equations, analyze a new
problem, pitch manure, program a computer, cook a tasty meal, fight
efficiently, die gallantly. Specialization is for insects.
LAZARUS LONG (Robert A. Heinlein)





On Thursday, January 21, 2021, 03:34:29 AM CST, eddie.draper@... via groups.io <eddie.draper@...> wrote:


"Air hardening steel"? To me that means high speed steel! A bit OTT, perhaps?


I feel that the combination of a steel screw and cast iron nut should be about the best economic solution. The one feature that sticks out in this design is why use UNF for a thread that is going to get a lot of use? I'm not sure about that statement, but the original question did describe it as a leadscrew. The coarser the better under those circumstances, and if you're not updating to metric, then use Whitworth. 12 tpi, and as a marginal added bonus, the thread is slightly deeper than a UN 12 tpi due to the 55 v 60 degree thread angle.


Agreed that a nut made of Aluminium can be abrasive if not protected from air by a layer of oil. Aluminium oxide (sapphire / ruby) is the second hardest material behind diamond, and is used for grinding tungsten carbide (green grit wheels). More likely that the male thread was just plain made undersize, which can happen if a diebox on a capstan lathe is misused (my apprentice school experience in 1973 - ahem).


I think we can agree that both original design and manufacture were unsound.


Eddie




------ Original Message ------
From: "Ondrej Krejci via groups.io" <okrejci@...>
To: "southbendlathe@groups.io" <southbendlathe@groups.io>
Sent: Thursday, 21 Jan, 21 At 09:17
Subject: Re: [SouthBendLathe] Internal threading woes

Howdy,

Stating that a nut made by tapping had too much slop may imply that the original nut of aluminium acted as a lap. Cellulous fibres are quite abrasive. Per standard machine building practices, the smaller member should be harder; i.e. a pinion gear is of hardened steel and the driven gear left soft or of cast iron. May be nuts from air hardening steel would be more suitable?

Best wishes,


OK


trackthatpot2000
 

Here is a pic of the completed job ..I have made about 40 of these so far and sold 4 already this month.


Ray De Jong
 

Very nice work, saving useful machine from the scrap bin and perhaps making a hobby bring in in a few $'s.

On Friday, January 22, 2021, 4:32:54 AM PST, trackthatpot2000 <timmsken@...> wrote:


Here is a pic of the completed job ..I have made about 40 of these so far and sold 4 already this month.


mike allen
 

        looks sharp !

        animal

On 1/22/2021 4:32 AM, trackthatpot2000 wrote:
Here is a pic of the completed job ..I have made about 40 of these so far and sold 4 already this month.


trackthatpot2000
 

This is what the original design looks like it’s just extruded aluminium, the lug on the left is the one that is stripped...the manufacturer has now fitted a steel thread insert as per the one on the right...but this is still not ideal as steel on steel in a leadscrew is a no no.