4" ER32 lathe collet chuck

[Brian H]

There is a really good chance I bit off more than I can chew on this one, but, hey life is about challenging yourself to get better.

I decided to have a go at making an ER32 collet chuck for my little chinese lathe. I acquired a piece of 4140 4" shaft and drew a skectch with some rough dimensions.

Things are progressing much slower than I had originally thought (they usually do), but I'm not under any real time pressure to get this done other than I want to play with it. Due to the limited power and rigidity of my little lathe I can only remove about .0010" (.3-.4mm) at a time.

I am using carbide tooling and have consumed several tips through the initial process due to some hard spots in the steel. I thought I would try to use some HSS to cut this, but I have been unsuccessful.

I think I have ground the HSS tool to the proper geometry (watched several videos on several different channels) but it just seems to me the HSS is softer than the 4140. Abom was cutting welds with his HSS which I'm sure aren't any softer than this.

So, total newbie question, do HSS tools come in different "hardness"? How do I know what I have?

 

[historicalarms]

4140 bar is available in "hardened" and "annealed" state. I have tried to machine some of the Hardened bar in my 1340 lath and run into the same problem you have...burnt up more tooling than it was worth.

The 4140 bar that gun manufacturers use to build excellent chrome-molly gun barrels is an excellent strength steel but very much easier to drill and machine than the hard stuff.

 

[Brian H]

4140 bar is available in "hardened" and "annealed" state. I have tried to machine some of the Hardened bar in my 1340 lath and run into the same problem you have...burnt up more tooling than it was worth.

The 4140 bar that gun manufacturers use to build excellent chrome-molly gun barrels is an excellent strength steel but very much easier to drill and machine than the hard stuff.

Thanks for the info. I scrounged this from a scrap bin, the only way I knew it was 4140 is that is was written on the end (entirely possible it was mis-labled) and I have no idea what state it was in.
I have heard alot about free machining steels and would like to find some one day.

 

[Brent H]

Hi Brian,

4140 is one of those steels that likes speed and a good depth of cut to get a nice finish. With the carbide you need to peel off the chips quick so that the chip is removing a majority of the heat during the machining process. I think I was turning 1000 RPM on a 2” piece taking 40 to 50 thou at a time using a coated carbide. Most of my search into milling 4140 alway suggested lots of coolant if possible and the surface feet per minute needed to be fast with the cut depth deep.

I have not tried hss on it but will give it a go and let you know.

 

[Brian H]

Hi Brian,

4140 is one of those steels that likes speed and a good depth of cut to get a nice finish. With the carbide you need to peel off the chips quick so that the chip is removing a majority of the heat during the machining process. I think I was turning 1000 RPM on a 2” piece taking 40 to 50 thou at a time using a coated carbide. Most of my search into milling 4140 alway suggested lots of coolant if possible and the surface feet per minute needed to be fast with the cut depth deep.

I have not tried hss on it but will give it a go and let you know.

That sounds pretty close to what I gleaned from guys like John Mills, Tom Lipton and Adam Booth. However this is one of those time where I get a bit envious of guys that have lathes capable of those kind of cuts.
At approx. 500 RPM and a .3 mm (approx. 10 thou) cut my lathe drops about 80 RPM as soon as the cutter engages. The downside of a small bench top lathe with a 750w motor.
I get long stringy bits instead of nice chips since I cant get the proper speed and depth of cut carbide requires. I can only run 10 or 15 passes before I need to stop and let the work piece and tooling cool down (being very liberal with the cutting oil). I am hoping to get a cool mist set up in the near future and hopefully it will help with this kind of situation. Any feed back on what others have done is certainly welcome.

 

[Johnwa]

I found I could turn 4” diameter 4140 on my Southbend using HSS. Trick was to run in backgear at less than 100 RPM. any faster and the HSS just wore away.

 

[Janger]

Anneal it!

 

[trlvn]

...I thought I would try to use some HSS to cut this, but I have been unsuccessful.

I think I have ground the HSS tool to the proper geometry (watched several videos on several different channels) but it just seems to me the HSS is softer than the 4140. Abom was cutting welds with his HSS which I'm sure aren't any softer than this.

So, total newbie question, do HSS tools come in different "hardness"? How do I know what I have?

One of the Youtube channels I watch got some HSS from Banggood that was labelled for metal gravers. He found it would not hold an edge, so yes, I think there are different varieties of HSS and some is not suitable for lathe cutters.

From your picture, it looks like the geometry of your HSS bit is not correct. Typically, the tools are ground to a point and it is that point--and only the point--that does the cutting. The nose radius (corner radius) appears excessive. It appears to have little or no back rake. If there is any side rake, it appears to be for a facing tool where you likely want a tool that cuts from right to left, such as:



The best illustration of grinding lathe tool angles that I found was:

http://www.steves-workshop.co.uk/tips/toolgrinding/toolgrinding.htm

Good diagrams and photography plus a handy one page pdf that summarizes the key information.

HTH,

Craig

 

[Brian H]

I used the information I had for steel it is a 5 degree angle. Seemed a little shallow to me so that might be part of the issue. However, yes you are correct it never cut, just wore away

 

[Brian H]

I found I could turn 4” diameter 4140 on my Southbend using HSS. Trick was to run in backgear at less than 100 RPM. any faster and the HSS just wore away.

Unfortunately I don't have enough torque at that low an rpm

 

[trlvn]

I used the information I had for steel it is a 5 degree angle. Seemed a little shallow to me so that might be part of the issue. However, yes you are correct it never cut, just wore away

Sorry, which angle is 5 degrees? The steves-workshop page I referred to recommends the following for steel:

Side relief: 12 degrees
End relief: 8 degrees
Side rake: 12 to 18 degrees
Back rake: 8 to 15 degrees

High side and back rake mean that the cutting edge is sharper and should shave metal off with less effort. Especially with a very small nose radius (say 1/64 inch). The downside is that the edge won't be as durable and will need to be touched up more frequently. However, given that your lathe doesn't have a lot of torque at low RPM's that may be your best bet.

BTW, I have a fine diamond sharpening 'stone' (about 1 X 4 inches) that I use for honing HSS bits and touching them up. You want to maintain the tool's angles while doing this which may take a bit of practise. Because the grinder leaves rounded surfaces, all you need to do is hone a bright polished line across the rounded 'valley'. It doesn't have to be big, just polished and uniform.

I don't have any experience with 4140, but I understand that if it isn't cut cleanly, the heat generated may cause the steel to work harden. That then leaves a layer that is _very_ difficult to machine. I presume that testing with a file on areas that you suspect are work-hardened v. areas that should still be in an annealed state should react differently. FWIW.



Craig

 

[Johnwa]

I used this calculator
https://littlemachineshop.com/mobile/speeds_feeds.php

For my speeds. It seemed to work.

 

[Brian H]

I used this calculator
https://littlemachineshop.com/mobile/speeds_feeds.php

For my speeds. It seemed to work.

Thanks John, Ill check that out

 

[Brian H]

Sorry, which angle is 5 degrees? The steves-workshop page I referred to recommends the following for steel:

Side relief: 12 degrees
End relief: 8 degrees
Side rake: 12 to 18 degrees
Back rake: 8 to 15 degrees

High side and back rake mean that the cutting edge is sharper and should shave metal off with less effort. Especially with a very small nose radius (say 1/64 inch). The downside is that the edge won't be as durable and will need to be touched up more frequently. However, given that your lathe doesn't have a lot of torque at low RPM's that may be your best bet.

BTW, I have a fine diamond sharpening 'stone' (about 1 X 4 inches) that I use for honing HSS bits and touching them up. You want to maintain the tool's angles while doing this which may take a bit of practise. Because the grinder leaves rounded surfaces, all you need to do is hone a bright polished line across the rounded 'valley'. It doesn't have to be big, just polished and uniform.

I don't have any experience with 4140, but I understand that if it isn't cut cleanly, the heat generated may cause the steel to work harden. That then leaves a layer that is _very_ difficult to machine. I presume that testing with a file on areas that you suspect are work-hardened v. areas that should still be in an annealed state should react differently. FWIW.



Craig

Thanks Craig,
Ill try regrinding my tool and try again.
FYI, I have a set of ceramic stones that work really well for getting nice hones on tooling (and knife blades)

 

[historicalarms]

That sounds pretty close to what I gleaned from guys like John Mills, Tom Lipton and Adam Booth. However this is one of those time where I get a bit envious of guys that have lathes capable of those kind of cuts.
At approx. 500 RPM and a .3 mm (approx. 10 thou) cut my lathe drops about 80 RPM as soon as the cutter engages. The downside of a small bench top lathe with a 750w motor.
I get long stringy bits instead of nice chips since I cant get the proper speed and depth of cut carbide requires. I can only run 10 or 15 passes before I need to stop and let the work piece and tooling cool down (being very liberal with the cutting oil). I am hoping to get a cool mist set up in the near future and hopefully it will help with this kind of situation. Any feed back on what others have done is certainly welcome.

An Idea for a very inexpensive fluid delivery system: a five gallon pail for a reservoir and a very small garden center submersible pond pump, a few feet of C.T tubing connected to a BB fluid nozzle... first one I built ten years ago totaled under $50, prob a bit more now but still substantially less than a store-bought BB comercial offering.

Even the smallest pond pump has way more volume/pressure than needed but the flow is easily regulated with the valve that comes with the BB nozzle.

You will have to manufacture a make-shift drain system to return the fluid from your machine bed back to the pail ( a brass fitting or two epoxied or silicone'd to the chip tray and a couple more feet of tubing).

Just keep the pump submersed in the fluid but up off the bottom of the pail to keep it free of the scarf that will flow into the pail from the chip tray.

 

[Johnwa]

If the cut isn’t interrupted you can sharpen carbide on a diamond wheel. It allows you to shave off a few thousands similar to what can be done with HSS but at carbide speeds. The edge is fragile though.

 

[Brian H]

I used this calculator
https://littlemachineshop.com/mobile/speeds_feeds.php

For my speeds. It seemed to work.

I checked out that calculator. That is handy.
The only problem I have is not being able to slow my feed rate slow enough for my little lathe.
With the gears I have (working on getting more gears), the slowest feed rate I can get is .07"/rev.It really is quite a bite for steel on my mini lathe.
I have emailed LMS to see if they can help me solve this with extra/other gears.

 

[Brian H]

An Idea for a very inexpensive fluid delivery system: a five gallon pail for a reservoir and a very small garden center submersible pond pump, a few feet of C.T tubing connected to a BB fluid nozzle... first one I built ten years ago totaled under $50, prob a bit more now but still substantially less than a store-bought BB comercial offering.

Even the smallest pond pump has way more volume/pressure than needed but the flow is easily regulated with the valve that comes with the BB nozzle.

You will have to manufacture a make-shift drain system to return the fluid from your machine bed back to the pail ( a brass fitting or two epoxied or silicone'd to the chip tray and a couple more feet of tubing).

Just keep the pump submersed in the fluid but up off the bottom of the pail to keep it free of the scarf that will flow into the pail from the chip tray.

That sound like a very simple set up. I'm going to order a couple nozzles (one for the mill and one for the lathe) and start scrounging bits. I have to look in my bits and pieces box I think I have a washer fluid pump that may just fit the bill. I'm not sure if the flow rate will be adequate.

 

[Brian H]

Thanks Craig,
Ill try regrinding my tool and try again.
FYI, I have a set of ceramic stones that work really well for getting nice hones on tooling (and knife blades)

So, I reground my HSS bit and tried in combination with the speed/feed rate on the calculator on LMS and sadly it still just brned the tip and didn't cut at all.
As soon as ths project is done I'll try it on some mild steel and aluminum and see how I make out.
I really found the information on the steves workshop site that Craig provided really helpful on the process and correct angles to sharpen at.

I really appreciate how helpful everyone here is. This has to be a group of the smartest people I ever met! Thanks to everyone!

 

[historicalarms]

That sound like a very simple set up. I'm going to order a couple nozzles (one for the mill and one for the lathe) and start scrounging bits. I have to look in my bits and pieces box I think I have a washer fluid pump that may just fit the bill. I'm not sure if the flow rate will be adequate.

I use the same nozzle for both machines, they come with a magnetic base so you can move them around from machine to machine without changing any of the plumbing.

I'm sure your pump will have sufficient flow, you need very little volume ( even a little bit too much will cause splashing around a larger area than you want...speaking on this I should add that after my first model I built(which had a fair amount of "splash") I refined the plumbing to include a very small "flow diverter" that had an adjustable needle valve built into the diverted flow system so that I could run a simple "over-pressure-over flow" tube back to the reservoir. I think the small brass diverter (one inlet port & 2 out ports) was around 6 bucks at a local hardware.