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Evan
11-12-2007, 07:54 AM
I had a "real" machining job this weekend. I have a customer that needs a particular specialized part made in low quantity. It's a bushing used on log debarking machines. The original part is made from bronze and is no longer available. Making a set of new ones (10 per set) would be very expensive in the original material.

The bushing looks like this:

http://vts.bc.ca/pics3/bushing1.jpg

It isn't a difficult part to make but because of the expense I suggested that the part be made from acetal instead. Acetal has excellent impact resistance which is what this part requires in service. It isn't a bearing and doesn't rotate in use. It serves as a hanger for a very strong bungee.

While I could have just turned up a short run of these on the lathe I decided to take the time to make a form tool instead. There is a small chance that I will need to make more of these in the future. This is a perfect application for a full width form tool and once made the tool can be used to turn out these parts at very low time cost per unit. It also insures that the parts are identical. It's the next best thing to CNC. I also wanted to see how my "new" horizontal mill will handle a job like this.

I started with a scrap piece of planer blade. It is high speed steel and just the right size and material for such a tool. In the following set of photos I have removed the compound on my SB9 and have replaced it with a temporary work holder that allows me to use the largest CBN wheel in my collection (CBN=Cubic Boron Nitride). CBN is the best for grinding steel as steel will destroy a diamond wheel.

Pics 1 and 2 show the 9" wheel (just barely fits the lathe). I am using it to dress the part by creep feeding it with the electric lead screw drive. The depth of cut is a much as .050" but the feed rate is about 0.3 inch per minute. A little WD40 is used to cool the work and also to keep down the abrasive HSS dust generated. The wheel itself doesn't shed any tangible amount of abrasive but HSS dust is just as bad. The part is set above center so the wheel grinds the edge with the correct relief.

After finishing cutting the profile I switch to a slightly smaller wheel to hollow grind what will be the top surface of the cutter. In pics 3 and 4 the cutter is set so that the center of the wheel is below the cutting edge which produces a small rake angle on the tool.

http://vts.bc.ca/pics3/bushing2.jpg


This is the finished cutter. Note that the various radii are intentionally different to facilitate installation and retention of the bungees.

http://vts.bc.ca/pics3/bushing3.jpg

The acetal has been supplied to me in near net diameter so all I have to do is cut to length, face the ends and core the part to 1" ID. It is then mounted on a custom mandrel on the horizontal mill and the cutter is plunge fed into the work. The new mill makes short work of this and had no trouble handling the load. Total time to cut the part is around 2 minutes and that can be sped up if I change the oil in the variable transmission.

The parts have been intentionally made oversize to compensate for the lower overall strength of the acetal. In the application the exact size of the part isn't critical with the exception of the internal bore diameter.

http://vts.bc.ca/pics3/bushing4.jpg

John Stevenson
11-12-2007, 08:10 AM
Evan,
Seems a lot of work to go to when a simple bull nosed lathe tool and two bed stops could do the same job.

Also you haven't made it clear that although this works fine in very soft acetal anyone spending time to copy your arrangement and wishing to cut bronze or steel is in for a rude awakening due to excessive and dangerous chatter on a tool this wide.

This really should contain this warning.

.

Evan
11-12-2007, 08:24 AM
No need to warn anyone. I felt sure that you or someone else would. I don't know about other people but I can tell the difference between the machining properties of acetal and bronze or steel. It's why I don't use my wood bandsaw to cut steel but it works fine on acetal.

I know that I could have just turned it up. Didn't I mention that already? I wanted to try a form cutter this size on the mill which I recently acquired. I also might need to make more. Keep in mind that I am NOT running a business.

John Stevenson
11-12-2007, 08:31 AM
No need to warn anyone. I felt sure that you or someone else would. I don't know about other people but I can tell the difference between the machining properties of acetal and bronze or steel.

True but there must be many people on this board who have never plunged into ferrous or non ferrous metals with a wide tool.
Granted you are not running a businees but you do have more experiance than many on this board and a warning would have been nice and not have to rely on someone else.

BTW what program do you use to save the multiple images into. ?

.

Evan
11-12-2007, 08:50 AM
John,

Machining is full of techniques that work with one material but not another. It seems to me that it is self evident that acetal plastic might be just a bit different than steel. I think that even the new people to the sport are smart enough to realize they can't cut steel this way without at least 20 or 30 horsepower.

I use Paint Shop Pro for most of the graphics work.

lazlo
11-12-2007, 09:01 AM
The original part is made from bronze and is no longer available.

Switching from bronze to plastic is a pretty major change in materials properties, especially strength.

Why didn't you want to use bronze?

John Stevenson
11-12-2007, 09:06 AM
Probably cost.
I just priced some pieces for split bushes, 2-1/4" diameter x 2-1/4" long, 31 EACH, that's about $60 your end and I may need 20 - :eek::eek:

.

Ken_Shea
11-12-2007, 09:08 AM
Nice work Evan, and you got to use that grand old horizontal machine as well.

Where does one stop with warnings, perhaps we should make up special and colorful warning icons to stick in each post, kinda like all those seen on a ladder.

Here are a few
1) Be sure machine is grounded.
2) Secure long hair
3) Button shirt sleeves
4) If operating lathe be sure and remove T-wrench from chuck before starting.
5) Do not grip or touch moving cutters
6) Stop spindle before removing part.

John Stevenson
11-12-2007, 09:15 AM
I don't think it's a matter of where do you stop with warnings but the odd note will stop someone not so much getting hurt as wasting a lot of time.

Some newby is going to see that, not know the difference between delrin and brass and decide he's going to make some candle sticks.

So after he's spent probably 4 or 5 hours [ newby remember ] he plows into his stick of brass on his little C3 / Atlas / grizzly import and finishes up wearing it.

Lets face it we are seeing much more basic questions than this every day.

.

ammcoman2
11-12-2007, 09:30 AM
A few months back at our model club, Bill Huxhold, a craftsmen of note, showed how he made form cutters for a lampshade for his scale model Hardinge lathe that was made from bar stock.

It was exactly as Evan showed it, with one exeption - no relief on the top. He says he never relieves the top of the cutter so there is no loss of shape when resharpening. The shade by the way was extemely thin walled.

One club member asked how he was able to eliminate chatter marks. "Ah" he says, "even my Hardinge HLV will chatter with this size cutter. You just turn the lathe by hand for the final cleanup cut".

Geoff

oldtiffie
11-12-2007, 09:58 AM
A few months back at our model club, Bill Huxhold, a craftsmen of note, showed how he made form cutters for a lampshade for his scale model Hardinge lathe that was made from bar stock.

It was exactly as Evan showed it, with one exeption - no relief on the top. He says he never relieves the top of the cutter so there is no loss of shape when resharpening. The shade by the way was extemely thin walled.

One club member asked how he was able to eliminate chatter marks. "Ah" he says, "even my Hardinge HLV will chatter with this size cutter. You just turn the lathe by hand for the final cleanup cut".

Geoff


Right on Geoff.

Exactly the way to eliminate "chatter" when thread/screw cutting - works just about every time - as this is form cutting as well!!

oldtiffie
11-12-2007, 10:02 AM
I had a "real" machining job this weekend. I have a customer that needs a particular specialized part made in low quantity. It's a bushing used on log debarking machines. The original part is made from bronze and is no longer available. Making a set of new ones (10 per set) would be very expensive in the original material.

The bushing looks like this:

It isn't a difficult part to make but because of the expense I suggested that the part be made from acetal instead. Acetal has excellent impact resistance which is what this part requires in service. It isn't a bearing and doesn't rotate in use. It serves as a hanger for a very strong bungee.

While I could have just turned up a short run of these on the lathe I decided to take the time to make a form tool instead. There is a small chance that I will need to make more of these in the future. This is a perfect application for a full width form tool and once made the tool can be used to turn out these parts at very low time cost per unit. It also insures that the parts are identical. It's the next best thing to CNC. I also wanted to see how my "new" horizontal mill will handle a job like this.

I started with a scrap piece of planer blade. It is high speed steel and just the right size and material for such a tool. In the following set of photos I have removed the compound on my SB9 and have replaced it with a temporary work holder that allows me to use the largest CBN wheel in my collection (CBN=Cubic Boron Nitride). CBN is the best for grinding steel as steel will destroy a diamond wheel.

Pics 1 and 2 show the 9" wheel (just barely fits the lathe). I am using it to dress the part by creep feeding it with the electric lead screw drive. The depth of cut is a much as .050" but the feed rate is about 0.3 inch per minute. A little WD40 is used to cool the work and also to keep down the abrasive HSS dust generated. The wheel itself doesn't shed any tangible amount of abrasive but HSS dust is just as bad. The part is set above center so the wheel grinds the edge with the correct relief.

After finishing cutting the profile I switch to a slightly smaller wheel to hollow grind what will be the top surface of the cutter. In pics 3 and 4 the cutter is set so that the center of the wheel is below the cutting edge which produces a small rake angle on the tool.

This is the finished cutter. Note that the various radii are intentionally different to facilitate installation and retention of the bungees.

The acetal has been supplied to me in near net diameter so all I have to do is cut to length, face the ends and core the part to 1" ID. It is then mounted on a custom mandrel on the horizontal mill and the cutter is plunge fed into the work. The new mill makes short work of this and had no trouble handling the load. Total time to cut the part is around 2 minutes and that can be sped up if I change the oil in the variable transmission.

The parts have been intentionally made oversize to compensate for the lower overall strength of the acetal. In the application the exact size of the part isn't critical with the exception of the internal bore diameter.


Very creative and a very nice job Evan.

That would be a nice job as a "Turning" job with a single-point tool on your CNC mill using it as a lathe.

dp
11-12-2007, 10:48 AM
Very creative and a very nice job Evan.

That would be a nice job as a "Turning" job with a single-point tool on your CNC mill using it as a lathe.

Or as a trace cut on a lathe.

oldtiffie
11-12-2007, 10:54 AM
Originally Posted by oldtiffie
Very creative and a very nice job Evan.

That would be a nice job as a "Turning" job with a single-point tool on your CNC mill using it as a lathe.

Or as a trace cut on a lathe.

Interesting post Dennis.

I think I am missing something.

How is that achieved?

Evan
11-12-2007, 11:11 AM
For a trace cut disconnect the crossfeed lead screw and mount the original on the tailstock spindle. Use a tool holder with a tracer probe that follows the original to regulate the depth of cut of the tool on the new part.

Wouldn't work for this job as I changed the size and profile of the part. Acetal will hold up in this application. Acetal is often better than metal in applications that experience a lot of hammering as it has excellent impact resistance, better than mild steel. That is why the original bushings were bronze as it will work harden under impact and last longer that way.

Your Old Dog
11-12-2007, 11:51 AM
moved..........

dp
11-12-2007, 12:06 PM
Interesting post Dennis.

I think I am missing something.

How is that achieved?

Imagine a cross slide that has no lead screw but instead has a double acting hydraulic cylinder. Imagine a second such cylinder with a tracer probe attached to the piston. Now any movement of the tracer probe results in an identical movement of the cross slide. The cylinder with the probe is attached to the carriage. If the probe were arranged to follow a template such as Evan's cutter it would cause the cross slide to reproduce that movement in the work.

In a perfectly sealed and airless system it can be quite accurate owing to the incompressibility of oil. Here's a picture of of one: http://www.allproducts.com/manufacture98/ishaan/product1.html

There are many non-hydraulic methods of doing this as well. They are simply a more versatile taper cutting tool.

dicks42000
11-12-2007, 12:30 PM
A while ago I thought about a slightly silly, but toungue in cheek warning sign for the shop....

"Caution, machine tools are dangerous. Do not operate."

Rick

Peter N
11-12-2007, 12:47 PM
ACHTUNG - ALLES LOOKENPEEPERS

Das Machine is nicht fur gefingerpoken und mittengrabben.

Ist easy schnappen der springenwerk, blowenfusen und poppencorken mit spitzensparken.

Ist nicht fur gewerken by das dummkopfen.

Das rubbernecken sightseeren musten keepen das cotten-pickenen hands in das pockets.

Relaxen und watchen das blinkenlights.

(I think Wolfie has the original of that somewhere)

lazlo
11-12-2007, 12:59 PM
Acetal is often better than metal in applications that experience a lot of hammering as it has excellent impact resistance, better than mild steel.

Acetal has good impact resistance, but it's 1/4 of the tensile strength of 660 bronze (60 versus 240 MPa for SAE660). If that's a bushing for a "giant bungee", then it's held in tension, correct?

Acetal plastics have been around since the 50's. So assuming the de-barking machine is newer than that, the designer made a conscious choice to use bronze over acetal.

thistle
11-12-2007, 01:08 PM
if you had a while to fart around making up holders and working out the cutter shape, another way to make a form tool would be a skiving tool

the blade is mounted on the crosslide of the lathe at an angle and passes under the work to make the finished shape . a lot of work to get right, but presumably with cad you could work out the blade shape easily enough.

IOWOLF
11-12-2007, 04:09 PM
Peter, I do,thanx for remembering.

http://img.photobucket.com/albums/v11/iowolf/achtung.jpg

Evan , My god You have reinvented the form / shave tool,Brilliant,just Brilliant.

Evan
11-12-2007, 05:58 PM
Acetal has good impact resistance, but it's 1/4 of the tensile strength of 660 bronze (60 versus 240 MPa for SAE660). If that's a bushing for a "giant bungee", then it's held in tension, correct?

Acetal plastics have been around since the 50's. So assuming the de-barking machine is newer than that, the designer made a conscious choice to use bronze over acetal.

The bushing is in constant compression as the bungee is looped over it. This is an aftermarket modification to the original machine configuration. The machines are considerably older than the 50s and the OEM standard uses a giant black rubber band that fails catastrophically and without any warning. I know the "designer" personally. He used bronze because he could have the parts made up in Thailand back in the 80s for next to nothing. There is more to it than that but suffice to say that the "designer" is a self made man who did not graduate from high school. The main purpose of the bushing is to increase the radius of the mounting point of the bungee to save wear on the bungee.

Acetal will work just fine in this application just as it is working on the yoke follower bushings on my shaper.

Your Old Dog
11-12-2007, 06:13 PM
Acetal will work just fine in this application just as it is working on the yoke follower bushings on my shaper.

Clearly you are missing the point here Evan. Should a meteorite hit the bungi cord and stretch it to failure, the brass version of this bushing will last longer then the acetal. Is your shop meteorite proof? Hell, is any shop meteroite proof ? :D

Fasttrack
11-12-2007, 06:29 PM
Evan -

I tried your form cutting technique on 316 surgical steel, i lost an eye and part of my finger. My lawyers will be in contact with you shortly.





:D

You and John are both clearly way out of my league when it comes to machining and i have alot of respect for John, but in this case it seems like maybe a little bit of an over-reaction. You'd have to be a moron to try to use a form cutting tool like that one something hard.

I mean, ok Evan's post isn't geared towards beginners. Alot of the really good writers here have awsome posts that are like reading the article in the magazine but there are just as many who post their projects for admiration, criticism whatever.

Maybe instead of reaming Evan for a lack of warning, a more tactful response would have been to suggest that he approach his posts differently. I think we could all take a page out of Forrest Addy's book when it comes to posting great threads for beginners and veteran machinists.

John Stevenson
11-12-2007, 06:35 PM
I have said all I'm saying on the subject as I know I'm pissing up a lamp post.


.

IOWOLF
11-12-2007, 06:37 PM
"You'd have to be a moron to try to use a form cutting tool like that one something hard."

Hard? like brass,CRS, Tool steel? then you should use one of these.


http://www.sommatool.com/catalog/cutting.tools/dovetail.form.and.shave.tool.asp

jkilroy
11-12-2007, 06:45 PM
Now that Even has a nice form tool worked up he can only HOPE that the new bushings give a reasonable but shorter life span! Its called INCOME folks, everyone has got to eat! :D

Evan
11-12-2007, 07:08 PM
I'm not going to change how I post things and I'm not going to start warning people not to stare at the sun either. Anybody interested in machining has an IQ higher than the mean to start with. They can figure out for themselves what may or may not be possible or safe.

Warnings are warranted when the hazard is obscure or uncommon knowledge such as the hard metal disease causing potential of the cobalt contained as a binder in tungsten carbide tooling. It is not necessary to instruct somebody not to use a screwdriver as a cold chisel or to try and take a .5" depth of cut with a minilathe. A warning about not using this form tool to cut metal falls in the latter category.

speedsport
11-12-2007, 07:19 PM
John, I am curious about the saying "Pissing up a lamp post", where did this saying begin and just exactly what happens when you literally piss up a lamp post?, have you actually ever done it?

Evan
11-12-2007, 07:20 PM
Now that Even has a nice form tool worked up he can only HOPE that the new bushings give a reasonable but shorter life span! Its called INCOME folks, everyone has got to eat!

I'm aiming at half the life for 1/3 the price. Sounds like a good deal to me. I finished the rest of the lot today. After tweaking the mill a bit it takes about 60 seconds of actual mill time to cut the form on the part. My total time to make a part is about 8 minutes for which I can charge shop rate of a dollar a minute. The cost of making the part in 660 bronze would be around $40 to $50 including metal and shop time and then only if the stock was near net shape. The bore has to be 1.010" so cored stock with a 1" bore would have to be bored .010 over. It takes about 2 minutes to bore the acetal to finish size with a custom ground spade bit.

tony ennis
11-12-2007, 07:44 PM
I'm a complete beginner. I have no metalworking tools that operate. I have about 2 hours of lathe and mill time, mostly machining delron and the like.

Before I finished Evan's post it was obvious to me that this isn't something I should try. I don't know what else to say about it.

Rustybolt
11-12-2007, 08:00 PM
If it starts to chatter just use less relief angle on the top. counter intuitive, I know, but it works. It was right for John to point out the pitfalls. When using a large formtool it's very important to understand speeds and feeds. The larger the form tool the more pressure needed to get it to cut.

Ed Tipton
11-12-2007, 08:05 PM
I have a fair amount of time standing at a lathe, and considerably less at a milling machine. Even so, almost all of my cutting experience has been with either mild steel, wood, or linen phenolic materials. I do not recall having ever chucked up a piece of bronze, but it's possible that at some time I have done so.
Whenever I start working on a piece, until I have determined to my own satisfaction how it is going to cut, I always approach the job cautiously, which is probably the norm for all of us. Having never turned either acetal or bronze material, I would not be surprised if they machine quite differently from each other.
I think any responsible person would probably think the same way. I would instinctively shy away from using such a form tool on any piece of steel since since the alarm bells would be going off inside my head. For that matter, I'd even approach the acetal cautiously, although I would be willing to give it a try.
My point is this...even accomplished machinists may never have had occassion to work with a given material previously, and therefore, they would approach the "mystery" with caution. Unfortunately, there are those who do just "tread where angels fear to tread", without trepidation. They can sometimes be identified by missing or shortened fingers etc.:D

lane
11-12-2007, 08:17 PM
You want learn until you try. Some things work .Some things don`t.As Soon as any one tries that on any thing short of plastic or wood they will know it wont work on any thing less than a 36 inch Monarch. Good post Evan

oldtiffie
11-12-2007, 08:59 PM
Imagine a cross slide that has no lead screw but instead has a double acting hydraulic cylinder. Imagine a second such cylinder with a tracer probe attached to the piston. Now any movement of the tracer probe results in an identical movement of the cross slide. The cylinder with the probe is attached to the carriage. If the probe were arranged to follow a template such as Evan's cutter it would cause the cross slide to reproduce that movement in the work.

In a perfectly sealed and airless system it can be quite accurate owing to the incompressibility of oil. Here's a picture of of one: http://www.allproducts.com/manufacture98/ishaan/product1.html

There are many non-hydraulic methods of doing this as well. They are simply a more versatile taper cutting tool.

Thanks for the info Dennis - appreciated.

I thought it was something I'd missed.

Perhaps not.

I used a copy lathe similar to your post many years ago. It was much more specialised but did essentially the same job. The cam/shape that the follower used was made in either the main machine Shop or the Tool Room. CNC was unheard of then (about 50 years ago!!!).

I've had more of a "think" about using a CNC mill and it seems to be very difficult - the form-follower that you posted seems better. I'd expect that it would be expensive to set up though.

I posted the following pic of the principle of it (from a book) - some months ago - to make my point in explaining something then.
http://i200.photobucket.com/albums/aa294/oldtiffie/Copy_lathe1.jpg

oldtiffie
11-12-2007, 09:03 PM
I have said all I'm saying on the subject as I know I'm pissing up a lamp post.
.

Good for you John.

Here's me in my usual style in these matters!!

Guess which one's me!!!
http://i200.photobucket.com/albums/aa294/oldtiffie/P-taking1.jpg

mochinist
11-12-2007, 09:09 PM
Good for you John.

Here's me in my usual style in these matters!!

Guess which one's me!!!
http://i200.photobucket.com/albums/aa294/oldtiffie/P-taking1.jpgLMAO talented

Peter Sanders
11-12-2007, 09:18 PM
Hi

Evan,
Seems a lot of work to go to when a simple bull nosed lathe tool and two bed stops could do the same job.

Also you haven't made it clear that although this works fine in very soft acetal anyone spending time to copy your arrangement and wishing to cut bronze or steel is in for a rude awakening due to excessive and dangerous chatter on a tool this wide.

This really should contain this warning.

.

No doubt your sentiments are appreciated, however, surely THIS warning...


WARNING
Techniques presented by myself here may not be suitable for use in all situations or with all materials or equipment. Use at own risk.

At the end of the message constitutes a reasonable/sufficient warning?

We should not expect every post to contain a SPECIFIC warning about a SPECIFIC technique and how it DOES or DOES NOT apply to all materials and all machinery.

We need to be able to let people use their common sense (admitedly such sense is severely lacking in some of todays youth). They should either be aware of or cautious of their OWN use of ANY new technique or ASK QUESTIONS to resolve any doubts they may have.

If ANY machine USER does not have the ability to either UNDERSTAND the consequences OR ASK QUESTIONS then they should NOT be using ANY machine tool!

jimsehr
11-12-2007, 10:18 PM
I can remember [ in the god old days before cnc 40 to 50 years ago ] using many a form tool wider then that on W&S turret lathes on some tough materials. 17-4 ss, and other stainless steels, tool steel and some forms about half that wide on even inconel and a286 . Some of the form tools were made out of carbide. Used to use thick black sulfur oil that stunk. I remember first time I ran a tracer. WOW! Then first time I ran a cnc. WOW! WOW! That was great.
Jim
I think it's good for new guys to see some of the old ways things were done.

And, John I thought it was pissing up a rope.

And I think making the form tool is neat.

S_J_H
11-12-2007, 10:36 PM
Evan,
Here is my form tool, probably took a little longer to make than yours though.:D

http://i109.photobucket.com/albums/n48/S_J_H/cnc%20bench%20lathe/cnclathe071.jpg

lazlo
11-12-2007, 11:01 PM
Here is my form tool, probably took a little longer to make than yours though.:D

Nice job S_J -- you've made a lot of progress since you posted your last pictures! It looks like you're up and running? Any pictures? :)

lazlo
11-12-2007, 11:11 PM
I used a copy lathe similar to your post many years ago. It was much more specialised but did essentially the same job.

Tiffie, the "copy lathes" I've seen were conventional lathes with the Cadillac or Mimik hydraulic tracer attachment that DP posted. I didn't think there was such a thing as a "native" copy lathe?

Cadillac and Mimik made 2D and 3D tracing attachments for vertical mills too -- they were usually standard Bridgeport mills (for example) with the leadscrew disengaged.


There are many non-hydraulic methods of doing this as well. They are simply a more versatile taper cutting tool.

When I was hunting for a taper attachment for my Clausing, there was a guy on PM who was trying to convince me that I should get a tracer attachment instead. The problem is, they're huge! :) In addition to the bulky hydraulic crossfeed attachment, you also have a large hydraulic power unit in a box about the size of a large dorm fridge that has to sit next to the lathe.

The Cadillac and Mimik hydraulic tracers sell for peanuts on Ebay, but when I saw one in person, I realized why: the hydraulic mechanism is finicky, they leak hydraulic oil all over the place unless they're new,...

By the way, there's also an air tracer attachment that you see from time-to-time on the Monarch 10EE's. I've never seen one in person -- I'd be interested to know how it drives the cross slide. I'm guessing it drives a telescoping leadscrew on the cross slide (like a telescoping taper attachment), which would mean that you could still use the machine in manual mode.

jimsehr
11-12-2007, 11:36 PM
Lazlo
I used to run a HES tracer lathe where the tracer was built into the lathe. It was a great machine. French I think.
Jim

oldtiffie
11-12-2007, 11:59 PM
I'm not going to change how I post things and I'm not going to start warning people not to stare at the sun either. Anybody interested in machining has an IQ higher than the mean to start with. They can figure out for themselves what may or may not be possible or safe.

Warnings are warranted when the hazard is obscure or uncommon knowledge such as the hard metal disease causing potential of the cobalt contained as a binder in tungsten carbide tooling. It is not necessary to instruct somebody not to use a screwdriver as a cold chisel or to try and take a .5" depth of cut with a minilathe. A warning about not using this form tool to cut metal falls in the latter category.

Good reality check Evan.

It is reasonable that anyone reading posts on any of the HSM threads has a modicum of CDF (Common Dog F**k aka Common sense) and will read and perhaps apply anything with due caution.

The form tool you used on the machine you have and the material you chose to use after forming an informed opinion seems OK to me.

That's your decision.

So far as I'm aware you are neither responsible to nor accountable nor answerable to anyone else.

Each of us is responsible for what we do in our shop etc.

S_J_H
11-13-2007, 12:35 AM
Lazlo, regarding my cnc lathe, post # 30 has recent pics and links to videos of it doing some simple jobs. It works fantastic IMO.
http://bbs.homeshopmachinist.net/showthread.php?t=24690&page=3


Steve

toastydeath
11-13-2007, 12:40 AM
There are "Native" copy lathes. They look a lot like modern CNC gear - except they've got a turret of tools ganged to a turret of templates. Don't have any names for you guys. They started coming out right before NC got popular, if I recall my book learnin' correctly. Seen the pictures, never in real life or for sale. Real trick, high horsepower things.

The old turret lathes that could run wide form tools have high dynamic stiffness, though they don't get there by the most efficient road possible. That's pretty much the only requirement on a machine running a form tool. That, I guess, and having the horsepower to take a deep enough bite to keep the tool in the cut.

Almost all modern (and most older) engine lathes and CNC gear does not have the dynamic stiffness required to run a big form tool. Select screw machines and turret lathes only.

Doc Nickel
11-13-2007, 01:55 AM
I'm not going to change how I post things and I'm not going to start warning people not to stare at the sun either. Anybody interested in machining has an IQ higher than the mean to start with. They can figure out for themselves what may or may not be possible or safe.

-So you're (http://bbs.homeshopmachinist.net/showthread.php?t=25338) saying (http://bbs.homeshopmachinist.net/showpost.php?p=301806&postcount=10) the average reader is probably smart enough to know whether, oh, say, working on a firearm, just as a random example, is or isn't safe and legal in their own state, and a given poster shouldn't be concerned whether or not illustrating doing so might potentially be illegal in some foreign country, say, Canada?

Just asking for clarification, you understand.

Doc.

dp
11-13-2007, 02:45 AM
This is not the best this BBS is capable of. Evan has demonstrated a method to successfully do a job and we each are by our means necessitated to take from it what we can and apply it to our needs or observe and move on, quietly. For his effort at least in this subject there is no little amount of badgering sent his way and that is unflattering at the very least.

I found Mr. Stevenson's comments well meant as was Evan's response and one would have been justified to presume the issue would end there with all parties having expressed their thoughts. That didn't happen. In fact little positive followed Evan's original post which alone in this thread had value.

This BBS has a behavior problem, from time to time.

oldtiffie
11-13-2007, 04:07 AM
-So you're (http://bbs.homeshopmachinist.net/showthread.php?t=25338) saying (http://bbs.homeshopmachinist.net/showpost.php?p=301806&postcount=10) the average reader is probably smart enough to know whether, oh, say, working on a firearm, just as a random example, is or isn't safe and legal in their own state, and a given poster shouldn't be concerned whether or not illustrating doing so might potentially be illegal in some foreign country, say, Canada?

Just asking for clarification, you understand.

Doc.

Hi Doc.

The links you posted were specific to Evan and yourself. I daresay that quite a few of are guilty out of our own mouths at one time or another and, as you have shown, we can all be, and in some cases, me included, have, been hoist on our own petard.

I think that we are not and need not be each others keeper or "Nanny" either.

I recall those threads you linked to and I agree that it is a bit much to have a good "handle" on the law and circumstances in our own Country and circumstances let alone any other.

Encouraging or abetting anyone to break any law is stupid and careless, but so far as I could see neither of you have done that.

I should think that anyone showing others what they have achieved and how they achieved it in a HSM shop-related environment should be OK.

How others who read it take or regard it should be a matter for them alone.

I think that both you and Evan were and are correct in what you showed in your respective threads.

Neither of you, so far as I am aware, encouraged anybody to do what you did - you both only showed others what and how you both set about doing what you did in your own interest/s in your own shop/s.

The morals or ethics issues in posts such as these are for other places and forums/fora?.

Individual people should be aware of the risks inherent in just about anything they do and make up their own minds and undertake their own risk assessment and mitigation.

That you both had disagreements is nothing new either as many of us have had disagreements from time to time and have moved on.

My "long suits" do not include tact and diplomacy. My "social graces" are hardly likely to get me invited to "Tea" etc. with the Vicar or the Arch-Bishop either.

So.

Let's move on.

oldtiffie
11-13-2007, 05:03 AM
Evan,
Here is my form tool, probably took a little longer to make than yours though.:D

http://i109.photobucket.com/albums/n48/S_J_H/cnc%20bench%20lathe/cnclathe071.jpg

Hi Steve.

That sure is one marvelous machine. You must be very proud and satisfied - as you deserve to be.

I was very intrigued with the profile (hemisphere) and threading videos - I missed seeing them previously.

Was your tool path determined by modeling the profile of the cutter into/onto the model of the work?

I was very intrigued with the thread cutting as there is no physical connection (ie gear-train) between the spindle and the "X" and "Y" feed-screws.

I guess that there must a monitoring of the positions of the spindle and the lead-screw with respect to each other in the software.

How is that achieved?

I noticed too that the screwing tool was cutting on the left flank/side and that there was no need that I could see to "dress-up" the trailing/right thread groove flank/side either.

Am I correct in assuming that the tool was tracking at 30 degrees left to follow the right thread flank?

I could see the CNC motors on the "X" and "Y" lead-screws but I could not see how the spindle was driven other than the main motor as regarding getting and keeping the spindle and screws "in synch" with each other so very tightly under load at those speeds.

The reason I ask is that as you may be aware from my posts on John Stevenson's thread re. the new "Sig" x 4/4 vertical mill that I am interested in buying one. I was wondering and would require that the vertical mill spindle could be synchronised with the "X", "Y" and "Spare" motors as you have achieved with your lathe spindle and ball-screws.

What I'd like to be able to do on the Seig is to have the spindle synchronised to the rotab so as to generate a true involute gear with a spindle-mounted hob rather than just cut it incrementally and so leave a series of "flats" or "'steps" on the mating/meshing tooth faces of the finished gears.

I have one other question.

Could you have used you CNC lathe and a single-pointed tool to make the profile that Evan made with his profile tool?

I realise that your lathe and probably software if different to the Seig mill and I hope John Stevenson reads this post and responds to it.

I don't mean to hi-jack your excellent post at all - I was enthralled with it.



Again many thanks for a marvelous insight into your CNC lathe that you made.

IOWOLF
11-13-2007, 06:34 AM
Wow, It looks like we have a new Moderator.

I like the old one better,But that is an opinion,and it seems like those are getting to be flamed more recently.

We can't all get along,so leave others opinions alone. :)

John Stevenson
11-13-2007, 06:39 AM
bugger it tiffie, stop posting the same post on two threads.

Post deleted and moved to sneak preview post.

.

Evan
11-13-2007, 07:34 AM
A cnc lathe would make short work of cutting the form. With a reasonable lathe just a bit larger than my South Bend it can be done in one pass with acetal. However, the rest of the operations would take as long or longer. I cut the parts to about 1/8" longer than spec and then faced each end, one pass each with a carriage stop for reference. Then poked a center drill in one end for the spade drill to start in. Did all ten that way and then cored them with the spade drill with two more ops to chamfer the hole each end, again to the stop. Took about 30 minutes for the ten. None of this includes the time to make tooling for the job as I own the tooling. The spade drill was ground down from a handy 1 1/2" victim to cut a 1" hole slightly oversize. I could have sped up the job by disconnecting the lead screw on the cross slide so it could be moved in and out faster.

The form was cut on the mill and as I said it took about 1 minute to cut and another minute or two to set up/remove each piece on the mandrel.

I haven't done any real production work since the 70s so it was interesting to see just what sort of time it would take to make these parts. The form tool would make this a very profitable job compared to hand turning each part on a lathe if one had many more to do. As it was the parts turned out well and in spec (and on time). I am retired now so I have time to play with this sort of thing. Given the right equipment this is a very viable approach to the problem of making money if more such parts were needed.

As it stands, I don't get paid in dollars for this. It is however one of the ways that I am able to afford those pretty grinding wheels.

http://vts.bc.ca/pics3/bushings5.jpg

pressurerelief
11-13-2007, 07:50 AM
"I'm aiming at half the life for 1/3 the price." Sounds like a good deal at first but we are forgetting two factors in the equation. What is the cost of down time on the machine? This must be factored for the machine sitting idle while replacing parts that have a life span that is half of the original. Add in the cost of someone to do the switch, inventory the parts, etc., and the cost savings is no longer a savings.

P/R

Evan
11-13-2007, 08:11 AM
"I'm aiming at half the life for 1/3 the price." Sounds like a good deal at first but we are forgetting two factors in the equation. What is the cost of down time on the machine? This must be factored for the machine sitting idle while replacing parts that have a life span that is half of the original. Add in the cost of someone to do the switch, inventory the parts, etc., and the cost savings is no longer a savings.


The down time is both minimal and predictable. This part with the bungee replaces a part that would fail with no warning. The machine can't run without it. The life of the bungee is the limiting factor and will give plenty of opportunities to inspect and replace the bushings if need be at the same time. That takes about ten seconds if it proves necessary as it just slips on the shaft the bungee hooks on.

To give an idea of what the bungee looks like here is a pic.

http://vts.bc.ca/pics3/grey18.jpg

The bungees fail gradually as they lose tension when the internal fibers break down. The originals would snap instantly and at any time as they are a solid chunk of rubber.

This is three of the original bands.

http://vts.bc.ca/pics3/black.jpg

J Tiers
11-13-2007, 08:30 AM
Using a form tool that is a substantial fraction of the lathe swing is certainly ambitious. Most of us have chatter with tools of 1/20 the size, but of course in harder materials.

The form tool makes very good sense in THIS case, not only "because you can" but because back in the original post was the statement that the need recurs, and making a new batch identical to the old ones is best. How better to do that than a form tool, assuming you don't go full CNC?

Frankly, I'm with Evan..... If someone needs to be told that they shouldn't try every technique they see, they are a moron and should have a court injunction against even LOOKING AT a machine tool.

There are SO MANY WAYS to mess yourself up with older (and newer) tools, that the government should come and take them away for our own good. :rolleyes:

moldmonkey
11-13-2007, 09:27 AM
Evan,

You may have already thought of this but another market for you may be making custom profile woodworking tooling. Especially since you get the grinding wheels so cheap.

John Stevenson
11-13-2007, 09:50 AM
Evan,

You may have already thought of this but another market for you may be making custom profile woodworking tooling. Especially since you get the grinding wheels so cheap.

DON'T GO THERE.
got to shoot out now but I'll explain later, that's the fastest way to loose money.

.

Your Old Dog
11-13-2007, 10:06 AM
Wow, It looks like we have a new Moderator.

I like the old one better,But that is an opinion,and it seems like those are getting to be flamed more recently.

We can't all get along,so leave others opinions alone. :)

Oh no! I've just been "WOLF'd" I thnk! Who was that great American the poster boy for Optimism, who once said:

"So, YOD it sounds like you have done nothing but bitch about me.:)
__________________
NRA Life Member.
Not the Prick you think I am.

One more on the post counter. "

I've grown used to you Sunshine but I'm not sure if thats to my credit or fault :D

IOWOLF
11-13-2007, 12:32 PM
Bad dog, It wasn't aimed at you. so perhaps an apology from you is in order.

And blow your sunshine up your a$$,I know you call me that because I am Brighter than you. :)

Your Old Dog
11-13-2007, 12:38 PM
Gee I must have gotten to you! Most of your post are one liners, kind of like Don Rickles :D

IOWOLF
11-13-2007, 01:01 PM
Yawn !!!!!!!