Re: Unwanted taper when turning
You are using carriage handwheel to advance the carriage, and not the
compound to advance the cutter. Your photo almost looks like your compound
is set at an angle, and you are feeding using the compound instead of the
carriage. Another possibility is that you have a lot of slop in your cross
slide and/or compound. Have you tried locking the cross slide and compound
by tightening one of the gibs on them both? Also check the carriage. See if
you can grab the left and right sides, and try to twist, lift, rotate, see
if there is any movement in it that needs to be addressed. And as others
have stated, no back rake on the cutter when cutting brass.
Michael - California, USA
Micro-Mark MicroLux 7x16
LMS 3990 Hi-Torque Mill with power feed
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-----Original Message----- From: [email protected] < [email protected]> On Behalf Of Jack Lunn via groups.io Sent: Sunday, January 30, 2022 2:33 PM To: [email protected]Subject: [7x12MiniLathe] Unwanted taper when turning Just getting started with a new to me HF 7X10 (extended to 16). Trying to practice on brass and the bit “digs” in as i move the saddle to the left. This results in an inward taper. I’ve tried to adjust the cross slide to remove any play. What should i check? Thank you for any assistance! Attachments: image0.jpeg: /g/7x12MiniLathe/attachment/115637/0
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Re: Unwanted taper when turning
When you said “digging in” the first thing I thought of is the back rake is zero for Brass and Bronze in this online reference: ? Jim Lynch ?
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Re: Saddle/Carriage adjustments
The adjustment scheme for the carriage slide plates works better on large lathes than it does on our small machines.? Most 7X owners find that shimming the slide plates is easy and works well.? In addition, it often helps considerably to refine the bed thickness where the slide plates run.? See:
John
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Re: Saddle/Carriage adjustments
Certainly begin by looking at and adjusting the saddle.? ?The saddle adjustment is a rather crude arrangement - you will have to remove the apron and the back splash (if still in use).
--
Lone Tree, Colorado? ?USA
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Re: Unwanted taper when turning
Judging from what you have said, my question is ‘are you using a lathe tool designed for steel and having top rake’? If so, turning tools for brass should be 0 deg top and side rake ie a flat top. Otherwise they dig in and cause all sorts of problems. Best wishes and stay safe. ?????? Ellis ?
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Just getting started with a new to me HF 7X10 (extended to 16). Trying to practice on brass and the bit “digs” in as i move the saddle to the left. This results in an inward taper. I’ve tried to adjust the cross slide to remove any play. What should i check?
Thank you for any assistance!
Attachments:
image0.jpeg: /g/7x12MiniLathe/attachment/115637/0
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Re: RideTheGearTran has a new feature
For the standard of threading that most of us machine, the easiest method of finding out tap drill sizes, is to look at a chart ! The next easiest is to subtract the pitch of the thread from the diameter and adjust for the nearest drill size – up or down. eg M6 x 1, tap drill 5 dia, !” BSW 8tpi, tap drill 7/8” dia. I use the first method for standard threads and the second for non standard. No problems in over 50 years of work. Best wishes and stay safe. ???????? Ellis ? ? ? And just to provide a little data on this, I found this at Tapmatic and it covers the topic succinctly with an eye-opening chart. ?
? Chuck K.
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Re: Unwanted taper when turning
Also, what type of cutting tool are you using???How much material do you have sticking out of the chuck???What depth of cut are you taking???Material diameter???I've learned there's a lot that can cause a taper especially like your describing. There's a ton of knowledge in this group and they've helped me sort out a bunch of stuff that was at least me doing something wrong and to be honest that's lot easier to fix, LOL!??Thin material sticking out will want to flex away from the tool causing a taper. I turn custom orifices out of 3/8" brass and it cuts nicely with very sharp tooling and keeping the stick out to about an inch and a half. Over that and I have to take very light cuts or the material deflects from the tool. A little more information on what you're trying and I'm sure it can be sorted out.?
Ryan
On Jan 30, 2022, 11:34 PM -0500, mike allen <animal@...>, wrote:
??? ??? are you turning between centers ? or just using the chuck ? Is
the headstock aligned with the lathe bed ?
animal
On 1/30/2022 2:33 PM, Jack Lunn via groups.io wrote:
Just getting started with a new to me HF 7X10 (extended to 16). Trying to practice on brass and the bit “digs” in as i move the saddle to the left. This results in an inward taper. I’ve tried to adjust the cross slide to remove any play. What should i check?
Thank you for any assistance!
Attachments:
image0.jpeg: /g/7x12MiniLathe/attachment/115637/0
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Saddle/Carriage adjustments
Hi All.
I'm finally? getting back into the machinist hobby after recovering from
back surgery and other health issues.? From day one it seemed like the
saddle/carriage didn't move as well as it should.? Nothing like as easy
as the cross slide.? Seems like the gibs/retainers need to be adjusted.?
Lathe is a HF 93212.? Any tips/instructions on going about this for a
newbie?
Stan
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Re: Unwanted taper when turning
are you turning between centers ? or just using the chuck ? Is
the headstock aligned with the lathe bed ?
animal
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On 1/30/2022 2:33 PM, Jack Lunn via groups.io wrote: Just getting started with a new to me HF 7X10 (extended to 16). Trying to practice on brass and the bit “digs” in as i move the saddle to the left. This results in an inward taper. I’ve tried to adjust the cross slide to remove any play. What should i check?
Thank you for any assistance!
Attachments:
image0.jpeg: /g/7x12MiniLathe/attachment/115637/0
|
Re: RideTheGearTran has a new feature
"real engineers" are likely?working with metric holes and you don't need a table to figure stuff out.? It is simple enough you can just remember?it for common sizes. There are not so many metric drill sizes.? Most drill sets go in 0.5 mm steps, a few in 0.1 mm steps.? But that's it.
One thing you left out of the calculation is the number of threads engaged.? ?This is important.
Typically you want the fastener to develop its full strength.?To do this you calculate?the amount of metal that is in shear.? This is the size (area) of the thread times the percent engagement?times the number of turns.? ? So the number of turns is equally?important?as the percent engagement.? ?As soon as the amount of metal is the same as the screw's minor diameter cross-section then the threads?are as strong as the screw.
Engineering is slightly more complex if the threaded?hole is a different material?from the screw.? ?You just need enough?turns to develop?the required strength at the percent engagement.
Normal nuts are designed to be just under this limit.? They will fail just before the screw is about fail.? It is this way so if overtightened the nut fails.? ?If nuts were made longer then the screw would fail first. So you can look at a nut and see about what you need in terms of thread engagement.
No I'm not a mechanical engineer, my area is different but I've read up a little on fastener design
Drill Sizes:?
The latest addition to the menu has an orange border around the button as it is independent of the main program. If you click it you can choose a thread from the metric or imperial thread reference tables, and choose the diameter you want.? The program then displays all the thread specifications and tables of drill sizes that could be used to tap a thread of that size.
I previously thought that a drill equal to the minor diameter at the root of the thread would be ideal to give 100% thread depth. But with ordinary, straight fluted, taps that is not the case. Generally they recommend 75% thread depth. The reason is that there is a forming process, whereby the tap pushes metal up into the crest and can produce a 100% thread depth even though the drill would suggest 75%. Consequently tables recommending drill sizes are typically based on 75% depth. Since they are designed as printed tables they usually only give you one option. But we may not have exactly the right sized drill. Then what.?
The choice of 75% is somewhat arbitrary. Softer materials like aluminium may form more easily and could accommodate drills less than 75%. Harder materials like stainless steel form less readily and ideally should use a higher percentage. On the other hand, if there is little load on the thread the designer might be happy to accept a lower percentage, particularly if the material is strong.
Since the computer program can deal with a single thread without having to produce a table for all threads, it gives us an opportunity to produce tables with a range of common drill sizes showing what percentage of thread depth would be covered. That is what I have done with RideTheGearTrain. The hobbyists can look at the drills they have available and decide whether they are happy with the percent depth they will achieve.
So, what do the REAL engineers think of this idea?? Any comments or suggestions? Is this idea unusual? Unique? Or general knowledge.
PS RideTheGearTrain now has several entries for mini-lathes with or without a thread cutting gearbox.
For those who don't know, the primary purpose of this free program is to calculate what gears are needed in the gear train to cut a thread of any pitch or TPI.
Evan
--
Evan
Lathe: 1955 Boxford Model A with screw cutting gearbox and power feed.
My Free Online Geartrain Software:
My YouTube Channel and Playlist about using an engineers lathe: ?
Project to build a Greek Hero steam engine and measure its power output:?
--
Chris Albertson
Redondo Beach, California
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Unwanted taper when turning
Just getting started with a new to me HF 7X10 (extended to 16). Trying to practice on brass and the bit “digs” in as i move the saddle to the left. This results in an inward taper. I’ve tried to adjust the cross slide to remove any play. What should i check?
Thank you for any assistance!
|
Re: RideTheGearTran has a new feature
And just to provide a little data on this, I found this at Tapmatic and it covers the topic succinctly with an eye-opening chart. ? ? Chuck K. ? Sent from for Windows ?
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From: Roy via groups.ioSent: Sunday, January 30, 2022 6:47 PM To: [email protected]Subject: Re: [7x12MiniLathe] RideTheGearTran has a new feature ? As Chuck pointed out, 75% is the common depth goal. The detailed thread specs call for a slight flat at both the crests of male threads & the valleys of female threads - aiming for 75% automatically achieves that. There's very little strength gain from 100% depth; more than offset by the difficulty of actually achieving it. Even for interference threads, the interference is in the bulk of the body, not the crests/valleys.
Roy (an actual BSME) ?
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Re: RideTheGearTran has a new feature
As Chuck pointed out, 75% is the common depth goal. The detailed thread specs call for a slight flat at both the crests of male threads & the valleys of female threads - aiming for 75% automatically achieves that. There's very little strength gain from 100% depth; more than offset by the difficulty of actually achieving it. Even for interference threads, the interference is in the bulk of the body, not the crests/valleys.
Roy (an actual BSME)
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Re: RideTheGearTran has a new feature
I cannot lay hands on my copy right now, as it has vanished into a pile of boxes :-( ?but Machinery’s Handbook recommends that same for thread depth, and has a larger table for a variety of materials and reccomended thread % depth. IIRC it is also somewhat dependent on thread pitch, as well. On Jan 29, 2022, at 8:16 PM, Charles Kinzer < ckinzer@...> wrote:
Well, I don’t know if I’m a “real” engineer (mechanical anyway, maybe electrical), but I have done quite a bit of machining. ? The thread depth is a tradeoff between strength and how difficult it is to tap the hole.? More thread depth, more strength.? Less thread depth, easier to tap the hole. ? It turns out that 75% is a very good ball park percentage where if you go higher you aren’t really getting more strength to speak of.? But the torque required to tap goes way up.? 75% is good for soft metals and hard metals.? But for hard metals you can often go even lower such as 65% thread depth and still have more than adequate strength, yet be able to tap it easier.? For thin sheet metal you would go up in percentage as sort of a special case. ? The bottom line is that there is no reason to try for “100% thread depth” because it is not needed.? Really sharp crests, such as what you get with 100% thread depth, aren’t desirable, either. ? Chuck K.? ? Sent from??for Windows ? From:?EvanSent:?Saturday, January 29, 2022 6:55 PM To:?[email protected]Subject:?[7x12MiniLathe] RideTheGearTran has a new feature ? [Edited Message Follows]
Drill Sizes:?
The latest addition to the menu has an orange border around the button as it is independent of the main program. If you click it you can choose a thread from the metric or imperial thread reference tables, and choose the diameter you want. ?The program then displays all the thread specifications and tables of drill sizes that could be used to tap a thread of that size.
I previously thought that a drill equal to the minor diameter at the root of the thread would be ideal to give 100% thread depth. But with ordinary, straight fluted, taps that is not the case. Generally they recommend 75% thread depth. The reason is that there is a forming process, whereby the tap pushes metal up into the crest and can produce a 100% thread depth even though the drill would suggest 75%. Consequently tables recommending drill sizes are typically based on 75% depth. Since they are designed as printed tables they usually only give you one option. But we may not have exactly the right sized drill. Then what.?
The choice of 75% is somewhat arbitrary. Softer materials like aluminium may form more easily and could accommodate drills less than 75%. Harder materials like stainless steel form less readily and ideally should use a higher percentage. On the other hand, if there is little load on the thread the designer might be happy to accept a lower percentage, particularly if the material is strong.
Since the computer program can deal with a single thread without having to produce a table for all threads, it gives us an opportunity to produce tables with a range of common drill sizes showing what percentage of thread depth would be covered. That is what I have done with RideTheGearTrain. The hobbyists can look at the drills they have available and decide whether they are happy with the percent depth they will achieve.
So, what do the REAL engineers think of this idea? ?Any comments or suggestions? Is this idea unusual? Unique? Or general knowledge.
PS?RideTheGearTrain?now has several entries for mini-lathes with or without a thread cutting gearbox.
For those who don't know, the primary purpose of this free program is to calculate what gears are needed in the gear train to cut a thread of any pitch or TPI.
Evan
--?
Evan
Lathe: 1955?Boxford?Model A with screw cutting gearbox and power feed.
My Free Online Geartrain Software:
My YouTube Channel and Playlist about using an engineers lathe: ?
Project to build a Greek Hero steam engine and measure its power output:?
?
--? Bruce Johnson
"Wherever you go, there you are." B. Banzai, PhD
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Re: RideTheGearTran has a new feature
Evan,
I have been using tap drill charts for most all my tapping needs for my entire career. This info is always available to me on large wall charts and has served me well. In special cases I have other resources such as Machinery’s?Handbook.
Software is the wave of the future, is here now and will eventually replace printed information entirely I believe. My machining career has spanned well over fifty years and change is the one constant and it is here to stay.
I wish you well!
Dick
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Re: RideTheGearTran has a new feature
Thanks Chuck.?
Yes ease of tapping is another factor. Hard materials may not form so well, but they are also harder to tap so a lower percentage thread depth would help, and since these materials are also stronger you can get away with a shallower cut.?
The idea of the tables is to give people some idea of how close the drill is, when you don't have exactly the right drill.
--
Evan
Lathe: 1955 Boxford Model A with screw cutting gearbox and power feed.
My Free Online Geartrain Software:
My YouTube Channel and Playlist about using an engineers lathe: ?
Project to build a Greek Hero steam engine and measure its power output:?
|
Re: RideTheGearTran has a new feature
Well, I don’t know if I’m a “real” engineer (mechanical anyway, maybe electrical), but I have done quite a bit of machining. ? The thread depth is a tradeoff between strength and how difficult it is to tap the hole.? More thread depth, more strength.? Less thread depth, easier to tap the hole. ? It turns out that 75% is a very good ball park percentage where if you go higher you aren’t really getting more strength to speak of.? But the torque required to tap goes way up.? 75% is good for soft metals and hard metals.? But for hard metals you can often go even lower such as 65% thread depth and still have more than adequate strength, yet be able to tap it easier.? For thin sheet metal you would go up in percentage as sort of a special case. ? The bottom line is that there is no reason to try for “100% thread depth” because it is not needed.? Really sharp crests, such as what you get with 100% thread depth, aren’t desirable, either. ? Chuck K. ? Sent from for Windows ?
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From: EvanSent: Saturday, January 29, 2022 6:55 PM To: [email protected]Subject: [7x12MiniLathe] RideTheGearTran has a new feature ? [Edited Message Follows] RideTheGearTrain.com
Drill Sizes:?
The latest addition to the menu has an orange border around the button as it is independent of the main program. If you click it you can choose a thread from the metric or imperial thread reference tables, and choose the diameter you want. ?The program then displays all the thread specifications and tables of drill sizes that could be used to tap a thread of that size.
I previously thought that a drill equal to the minor diameter at the root of the thread would be ideal to give 100% thread depth. But with ordinary, straight fluted, taps that is not the case. Generally they recommend 75% thread depth. The reason is that there is a forming process, whereby the tap pushes metal up into the crest and can produce a 100% thread depth even though the drill would suggest 75%. Consequently tables recommending drill sizes are typically based on 75% depth. Since they are designed as printed tables they usually only give you one option. But we may not have exactly the right sized drill. Then what.?
The choice of 75% is somewhat arbitrary. Softer materials like aluminium may form more easily and could accommodate drills less than 75%. Harder materials like stainless steel form less readily and ideally should use a higher percentage. On the other hand, if there is little load on the thread the designer might be happy to accept a lower percentage, particularly if the material is strong.
Since the computer program can deal with a single thread without having to produce a table for all threads, it gives us an opportunity to produce tables with a range of common drill sizes showing what percentage of thread depth would be covered. That is what I have done with RideTheGearTrain. The hobbyists can look at the drills they have available and decide whether they are happy with the percent depth they will achieve.
So, what do the REAL engineers think of this idea? ?Any comments or suggestions? Is this idea unusual? Unique? Or general knowledge.
PS RideTheGearTrain now has several entries for mini-lathes with or without a thread cutting gearbox.
For those who don't know, the primary purpose of this free program is to calculate what gears are needed in the gear train to cut a thread of any pitch or TPI.
Evan
--
Evan
Lathe: 1955 Boxford Model A with screw cutting gearbox and power feed.
My Free Online Geartrain Software:
My YouTube Channel and Playlist about using an engineers lathe: ?
Project to build a Greek Hero steam engine and measure its power output:? ?
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RideTheGearTran has a new feature
RideTheGearTrain.com
Drill Sizes:?
The latest addition to the menu has an orange border around the button as it is independent of the main program. If you click it you can choose a thread from the metric or imperial thread reference tables, and choose the diameter you want. ?The program then displays all the thread specifications and tables of drill sizes that could be used to tap a thread of that size.
I previously thought that a drill equal to the minor diameter at the root of the thread would be ideal to give 100% thread depth. But with ordinary, straight fluted, taps that is not the case. Generally they recommend 75% thread depth. The reason is that there is a forming process, whereby the tap pushes metal up into the crest and can produce a 100% thread depth even though the drill would suggest 75%. Consequently tables recommending drill sizes are typically based on 75% depth. Since they are designed as printed tables they usually only give you one option. But we may not have exactly the right sized drill. Then what.?
The choice of 75% is somewhat arbitrary. Softer materials like aluminium may form more easily and could accommodate drills less than 75%. Harder materials like stainless steel form less readily and ideally should use a higher percentage. On the other hand, if there is little load on the thread the designer might be happy to accept a lower percentage, particularly if the material is strong.
Since the computer program can deal with a single thread without having to produce a table for all threads, it gives us an opportunity to produce tables with a range of common drill sizes showing what percentage of thread depth would be covered. That is what I have done with RideTheGearTrain. The hobbyists can look at the drills they have available and decide whether they are happy with the percent depth they will achieve.
So, what do the REAL engineers think of this idea? ?Any comments or suggestions? Is this idea unusual? Unique? Or general knowledge.
PS RideTheGearTrain now has several entries for mini-lathes with or without a thread cutting gearbox.
For those who don't know, the primary purpose of this free program is to calculate what gears are needed in the gear train to cut a thread of any pitch or TPI.
Evan
--
Evan
Lathe: 1955 Boxford Model A with screw cutting gearbox and power feed.
My Free Online Geartrain Software:
My YouTube Channel and Playlist about using an engineers lathe: ?
Project to build a Greek Hero steam engine and measure its power output:?
|
Re: A (maybe?) different cross slide travel extension?
Thanks Bruce. Here I kinda thought I had a novel idea LOL!??I was staring at my lathe the other night, wondering how to gain some travel in both directions.??I don't have, nor do I have access to a mill any more and that's when the idea about moving the nut came to me.?
I made up a spacer and it's just over an inch long so if I move the nut the same distance back I should gain that much travel towards me according to the link from Mike Weebly.? ?And I need a little more travel away from me so I'm thinking adding about 2", 2.5" to the screw should do it.?
I think drilling and taping the screw and then threading the extension in and soldering. Then I can indicate the screw in off the threads, turn the extension to diameter, then pick up the thread to thread the extension. I think that's a good way to keep the screw as straight as I can. Any better way I'm missing?
I probably have a drill bit with a junk point I can grind down too. Thanks for the idea!
Ryan
On Jan 25, 2022, 7:48 PM -0500, Bruce J <bruce.desertrat@...>, wrote:
On Jan 25, 2022, at 2:19 PM, Ryan H via < ifly172@...> wrote:
Wow!??That's awesome Dick!??I'm sure mine won't turn out near so fancy but I hope it'll be functional!??You wouldn't happen to know the center to center distance on the two screws that mount the feed nut by chance???I think getting those holes located, and making the flat bottoms for the screw heads is going to be one of the bigger headaches of this.?
Flat bottoms can be done by finding a HSS twist drill of the correct size and carefully grinding the end flat,
--?
Bruce Johnson
"Wherever you go, there you are." B. Banzai, PhD
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Re: A (maybe?) different cross slide travel extension?
On Jan 25, 2022, at 2:19 PM, Ryan H via < ifly172@...> wrote:
Wow!??That's awesome Dick!??I'm sure mine won't turn out near so fancy but I hope it'll be functional!??You wouldn't happen to know the center to center distance on the two screws that mount the feed nut by chance???I think getting those holes located, and making the flat bottoms for the screw heads is going to be one of the bigger headaches of this.?
Flat bottoms can be done by finding a HSS twist drill of the correct size and carefully grinding the end flat,
--? Bruce Johnson
"Wherever you go, there you are." B. Banzai, PhD
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Jim
GadgetBuilder
OldToolmaker
Evan