turning hardened steel


William Nelson
 

I'm thinking of making a ER40 chuck for my 10K. Because I don't want to set up to thread metric and bore the 8 degree internal taper (best ground, no grinder) I was thinking of using a ER40 hex block. I would have only one operation a internal 1.5"-8 thread of which I've done a bunch in aluminum and mild steel.. Now the problem is these blocks are hardened to 40-45 HRc. I'm not really sure how hard that is comparatively speaking. I have some 5C blocks which seem pretty hard. I'm sure I could use carbide to bore it out (not a lot of material as they are already bored) with no problem but I'm not sure how well the threading would go. I know I would need carbide for this too and besides the block itself would be my only expense. Has anyone had any experience doing a internal thread on hardened steel? I can not thread mill it. If nobody has tried this does it sound feasible to anyone? I'll be going over to my local machine tool shop (1/4 mile away) and ask them what they think too lots of knowledge with the guys who work there plus I can buy my carbide threader (Solid or insert?) there too. My only other "SMALL" problem would be getting it perfectly aligned which shouldn't take me much more than a day at most.  :(

Bill form Socal


Carl Bukowsky
 

Bill, 
I have to say you may not get results you are looking for by working the ER-40 collet chuck-to-spindle engagement last.  Ideal sequence is make the spindle threads first, then make the collet holder while mounted to the spindle.

Making a collet chuck in the reverse order, spindle threads last, you loose the concentricity relationship inherent in the single operation of creating the collet holder while it’s attached to the spindle.  

All your spindle-to-chuck concentricity you cut will be independent  to that of the collet block holder. Any small error in your chuck, and any error in centering the work piece in the chuck, will all be added into the spindle threads you cut. 

I just made an ER-40 collet chuck on my SB 9” from  2” piece of 4140 and it’s not that complicated.

You can make your own ER-40 nut if you don’t want to cut metric threads.  I went metric using some 3D printed change gears-my metric threads worked great with the ER-40 but I bought.  For the plans I bought a back issue Machinist’s Worshop (Feb/Mar 2015, Vol 28 No 1). Good Luck!  Carl


Sent by my iPhone

On Oct 4, 2021, at 7:04 PM, William Nelson <wnnelson@...> wrote:

I'm thinking of making a ER40 chuck for my 10K. Because I don't want to set up to thread metric and bore the 8 degree internal taper (best ground, no grinder) I was thinking of using a ER40 hex block. I would have only one operation a internal 1.5"-8 thread of which I've done a bunch in aluminum and mild steel.. Now the problem is these blocks are hardened to 40-45 HRc. I'm not really sure how hard that is comparatively speaking. I have some 5C blocks which seem pretty hard. I'm sure I could use carbide to bore it out (not a lot of material as they are already bored) with no problem but I'm not sure how well the threading would go. I know I would need carbide for this too and besides the block itself would be my only expense. Has anyone had any experience doing a internal thread on hardened steel? I can not thread mill it. If nobody has tried this does it sound feasible to anyone? I'll be going over to my local machine tool shop (1/4 mile away) and ask them what they think too lots of knowledge with the guys who work there plus I can buy my carbide threader (Solid or insert?) there too. My only other "SMALL" problem would be getting it perfectly aligned which shouldn't take me much more than a day at most.  :(

Bill form Socal


mike allen
 

On 10/4/2021 6:21 PM, Carl Bukowsky via groups.io wrote:
Bill, 
I have to say you may not get results you are looking for by working the ER-40 collet chuck-to-spindle engagement last.  Ideal sequence is make the spindle threads first, then make the collet holder while mounted to the spindle.

Making a collet chuck in the reverse order, spindle threads last, you loose the concentricity relationship inherent in the single operation of creating the collet holder while it’s attached to the spindle.  

All your spindle-to-chuck concentricity you cut will be independent  to that of the collet block holder. Any small error in your chuck, and any error in centering the work piece in the chuck, will all be added into the spindle threads you cut. 

I just made an ER-40 collet chuck on my SB 9” from  2” piece of 4140 and it’s not that complicated.

You can make your own ER-40 nut if you don’t want to cut metric threads.  I went metric using some 3D printed change gears-my metric threads worked great with the ER-40 but I bought.  For the plans I bought a back issue Machinist’s Worshop (Feb/Mar 2015, Vol 28 No 1). Good Luck!  Carl


Sent by my iPhone

On Oct 4, 2021, at 7:04 PM, William Nelson <wnnelson@...> wrote:

I'm thinking of making a ER40 chuck for my 10K. Because I don't want to set up to thread metric and bore the 8 degree internal taper (best ground, no grinder) I was thinking of using a ER40 hex block. I would have only one operation a internal 1.5"-8 thread of which I've done a bunch in aluminum and mild steel.. Now the problem is these blocks are hardened to 40-45 HRc. I'm not really sure how hard that is comparatively speaking. I have some 5C blocks which seem pretty hard. I'm sure I could use carbide to bore it out (not a lot of material as they are already bored) with no problem but I'm not sure how well the threading would go. I know I would need carbide for this too and besides the block itself would be my only expense. Has anyone had any experience doing a internal thread on hardened steel? I can not thread mill it. If nobody has tried this does it sound feasible to anyone? I'll be going over to my local machine tool shop (1/4 mile away) and ask them what they think too lots of knowledge with the guys who work there plus I can buy my carbide threader (Solid or insert?) there too. My only other "SMALL" problem would be getting it perfectly aligned which shouldn't take me much more than a day at most.  :(

Bill form Socal


Mark
 

On Mon, Oct 4, 2021 at 09:08 PM, mike allen wrote:
heres a few spindle mount ER Chucks
Good info Mike. I may use that at some point. Thanks


Ondrej Krejci
 

Howdy,

Personally, I'd just use the hex block in a three jaw chuck, but, if one has his heart set on screwing it on the spindle, the hex block with the largest collet mounted on turned up scrap stock would be the best bet for gingerly making the needed threads.  40 to 45 Rc should pass the file test, but I'd use carbide inserts.

Enjoy,


OK


William Nelson
 

That was my plan with the scrap stock to get it as concentric as possible. Now the problem is taking light cuts with carbide. Carbide normally from what I've read want's high rpm and large feeds that wont work well in this situation. Will the micro grain carbide with a super sharp edge allow you to take light cuts? I have had very little opportunity to use carbide on the lathe and had mixed results. Putting the collet chuck in the 3 jaw chuck doesn't appear to give any benefit over just using the 3 jaw alone. The possibility of increased run out rather than less seem likely. I want to use the hex collet chuck so I can turn some particular parts and then bring the block to the mill and do some milling without removing the part.  I was hoping to get good repeatability this way. This seems like a simple way to machine my parts but getting there may be the problem.

Bill from Socal


Ondrej Krejci
 

Greetings,

The scrap stock would be turned up and left in the lathe.  That way it would be as concentric as possible when clamping the collet holder on it.
Carbide generally performs well at high speeds, but threading is done more slowly, even CNC lathes need lead in and out paths.
As for cutting depths, equal area has worked best for me; i.e. first pass at 0.015" to 0.010", then gradually down to 0.003" or 0.002" leaving 0.001" for finishing with a spring pass or air cut.

Best Wishes,


OK

On Wednesday, October 6, 2021, 11:35:09 AM EDT, William Nelson <wnnelson@...> wrote:


That was my plan with the scrap stock to get it as concentric as possible. Now the problem is taking light cuts with carbide. Carbide normally from what I've read want's high rpm and large feeds that wont work well in this situation. Will the micro grain carbide with a super sharp edge allow you to take light cuts? I have had very little opportunity to use carbide on the lathe and had mixed results. Putting the collet chuck in the 3 jaw chuck doesn't appear to give any benefit over just using the 3 jaw alone. The possibility of increased run out rather than less seem likely. I want to use the hex collet chuck so I can turn some particular parts and then bring the block to the mill and do some milling without removing the part.  I was hoping to get good repeatability this way. This seems like a simple way to machine my parts but getting there may be the problem.

Bill from Socal