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  1. #31
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    Quote Originally Posted by pipeclay View Post
    I used to make my chucks out of 4140 , I never had a problem with it, I now use 1045,a little softer than 4140 and cheaper.

    If you can reverse the lathe shouldn't be a problem cutting the Internal thread.

    What you may want to do first is work out a design of what you want.

    You will have a through hole just not the the minor diameter of the threaded hole.

    I would suggest you bore the chuck to the required ID, length about 12mm 1/2" longer than needed, this extra length will allow space for your threading bar to stop before bottoming out, you will need to do an undercut in this extra length to a greater depth than your thread, ( say about .150" ).

    As long as you are cutting the thread slowly you should be able to hear when it stops cutting and be able to stop in the run off area.

    You can do as mentioned , weld a piece of HSS to a suitable piece of material to use as a boring bar, alternatively an indexable insert threading bar and tips are not overly expensive,a bar to suit 16 IR 60 would be okay but if you think you may want to do smaller internal threads you may want to consider getting a bar to suit 11 IR 60 tips.
    Thanks for the tips Pipeclay. OK, so maybe the 4140 I was given will be OK to use ?
    I can run my lathe in reverse thanks to the VFD, but I am worried about the chuck unscrewing from the forces generated. I have screwed the chuck on and off multiple times lately, today I was making some aluminium components for some pens I am making, I turned the switch off and the chuck started to unscrew by itself. I have the VFD setup to stop the rotation in 2 seconds. ( This is the first time its come loose on me, not put on tight enough when I put it back on last time obviously, but proves it can happen )

    I like the idea of having that runout space at the end of the thread, I think this is probably how I will do it. I can run the lathe at very low rpm, so that and the runout space should make things safe enough.

    Do the carbide inserts cut OK at these very low speeds ? ( 30-60rpm )
    ​Brad.
    Every Day might not be a good Day,
    but there is something good in every Day.

  2. #32
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    Quote Originally Posted by Picko View Post
    Stick with it Brad. I've never regretted going down this path.
    Quote Originally Posted by KBs PensNmore View Post
    As Picko said stick with it. Remember slow and steady, if you stuff up, you'll know what went wrong, whereas if you rush it and something goes wrong, it makes it hard to work out what or where. Cutting your first thread is something of an accomplishment.
    Kryn
    Thanks guys, slow and steady will definitely be the order of the day.
    ​Brad.
    Every Day might not be a good Day,
    but there is something good in every Day.

  3. #33
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    Quote Originally Posted by Ironwood View Post
    ...Do the carbide inserts cut OK at these very low speeds ? ( 30-60rpm )
    You would be better with HSS - holds an edge and works better at those lower speeds.

    Michael

  4. #34
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    Quote Originally Posted by jackaroo View Post
    I thought the imperial is 55deg instead of 60deg? I cut mine in reverse with HSS
    Attachment 382106

    Attachment 382107
    Nice job on those tools mate, not sure my grinding skills are up to that level, so will be looking at my options.
    ​Brad.
    Every Day might not be a good Day,
    but there is something good in every Day.

  5. #35
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    Quote Originally Posted by jackaroo View Post
    Oh no, I've been doing 55deg all that time!
    As long as you are doing both male and female threads at 55, it doesn't matter. Only you will know .
    ​Brad.
    Every Day might not be a good Day,
    but there is something good in every Day.

  6. #36
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    Quote Originally Posted by Michael G View Post
    You would be better with HSS - holds an edge and works better at those lower speeds.

    Michael
    OK, thanks Michael. Just got to design and make a tool , sounds easy .
    ​Brad.
    Every Day might not be a good Day,
    but there is something good in every Day.

  7. #37
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    Hi Brad, Guys,

    I use carbide insert threading tools, only because I seem completely unable to grind HSS tools to the correct angles for threading. I tend to run at about 100 rpm until I'm sure that the thread is correct, and then higher speeds to finish.

    I also plunge cut threads which seems to be frowned upon by some. I know and understand the reasons why, but for the threads that I cut, which tend to be relatively small ones its just fine. At the end of the day if it works for you, fine, go with it and don't fret about it.

    I consider myself a rank beginner and I'm still learning, so if you are happy with what you are doing and achieving, then carry on.

    26-08-2019-005.jpg
    Best Regards:
    Baron J.

  8. #38
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    I have a small fixture I use to grind HSS to correct angles, similar to this https://metalworkforums.com/f65/t188...99#post1806599

    If you go the way I did on post 30, I could grind a small piece of HSS to a 60 degree angle for you.

    Michael

  9. #39
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    Quote Originally Posted by BaronJ View Post
    Hi Brad, Guys,

    I use carbide insert threading tools, only because I seem completely unable to grind HSS tools to the correct angles for threading. I tend to run at about 100 rpm until I'm sure that the thread is correct, and then higher speeds to finish.

    I also plunge cut threads which seems to be frowned upon by some. I know and understand the reasons why, but for the threads that I cut, which tend to be relatively small ones its just fine. At the end of the day if it works for you, fine, go with it and don't fret about it.

    I consider myself a rank beginner and I'm still learning, so if you are happy with what you are doing and achieving, then carry on.
    If I already had the insert tooling, I would go that way. But it means finding the right stuff on the internet and waiting for it to arrive.
    I did the dummy shaft thread by plunging.

    Quote Originally Posted by Michael G View Post
    I have a small fixture I use to grind HSS to correct angles, similar to this https://metalworkforums.com/f65/t188...99#post1806599

    If you go the way I did on post 30, I could grind a small piece of HSS to a 60 degree angle for you.

    Michael
    I am pretty confident I can grind a cutting tip to do the job. Making a bar to hold it is more my issue I think.
    Do I drill a hole through a piece of bar and tap a hole for a grubscrew to hold it in place, or do I silver solder it to the end of a bar.
    I also have the issue of not having a boring bar suitable to do the hollowing out, and to cut the runout section at the end of the thread.
    ​Brad.
    Every Day might not be a good Day,
    but there is something good in every Day.

  10. #40
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    Quote Originally Posted by Michael G View Post
    I get around the problem of knowing when to stop simply by putting a piece of tape with a mark on it. When the mark is level with the front of the bore I know the cutting tip is the measured distance in.
    Attachment 382126

    Incidentally, that is a bought boring bar (H&F will probably have something similar). All I've done is grind the right form on the end (in this case ACME)

    Michael
    Sorry, I missed this post. I have my settings at 30 posts to a page, you must have slipped it in as I was replying and things went over to page 2.
    That looks like something I have been dreaming up, though I would be worried about the end of the bar hitting the end of the hole, I would have to chop it off closer to the cutter.
    The tape is something I do all the time on drill bits etc. though usually put a mark with a paint pen.
    ​Brad.
    Every Day might not be a good Day,
    but there is something good in every Day.

  11. #41
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    Quote Originally Posted by BaronJ View Post

    I seem completely unable to grind HSS tools to the correct angles for threading.
    Hi BaronJ

    I use one of these:
    https://www.carbatec.com.au/jig-chisel-grinding

    They are fairly flimsy, but adequate for the purpose. They come with paper templates to make gauges to give the correct table tilt for various chisel bevels using a 150 mm grinding wheel. I made similar templates from 40x3 aluminium to give the correct front, side and top rakes needed for HSS lathe tools.

    Frank.

  12. #42
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    Not going too well with the 4140. I am using a Diamond toolholder from Eccentric Engineering.

    First up, I chucked up the bigger piece ( 67.5mm x 100mm long ) and took a light skim cut off the end, things were going OK, I thought it cut pretty much the same as the piece I used for the dummy shaft.
    DSC_0281.jpg

    I then put the smaller piece ( 62.5mm x 75mm long ) in the chuck and proceeded to do the same thing. It started off OK, but the tip didn't last long ( 1/4" CoHSS )
    DSC_0279.jpg

    I had a freshly sharpened piece of 1/4" Tantung, I swapped over to that, it didn't last much longer. This piece could have benefited from having the sides honed and a small radius put on the front edge, but I would have thought it would have done better than it did. This piece is much brighter than the first, no rust. On one end is the original bright blue paint , both are marked 4140 by marking pen.
    DSC_0276.jpg

    I was cutting dry, very light cuts like .1mm and .2mm. Slow feed by hand, lathe was doing an estimated 1000rpm.

    Any thoughts on what I am doing wrong here ?
    ​Brad.
    Every Day might not be a good Day,
    but there is something good in every Day.

  13. #43
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    Increase nose radius slightly,drop speed to 500 or lower, use a cutting oil or coke bottle with hole in lid a solbile oil squirted occasionally, increase depth of cut to .005"/.010" for facing.
    Turn OD at about 250/350 depth of cut around .020"/.040" feed rate around .002"/.003".

  14. #44
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    Thanks for the tips Pipeclay, I will give them a try when I get a chance to regrind the cutters. Might take me a week to get back to it now, work calls again unfortunately.
    ​Brad.
    Every Day might not be a good Day,
    but there is something good in every Day.

  15. #45
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    This that same boring bar from my previous post, but this time loaded with a 55 degree shaped tool.
    IMG_0606.JPG
    The basic design is a bar with a cross drilled hole (shaped for the HSS cross section) and then a grub screw in the end to secure the insert. Being round in a standard tool holder, this one has a square profile holder that clamps the bar. (I have a larger one made of 25mm round bar that goes directly in a round holder, but still the same design).
    If you were pushed for space, I guess you could put the grub screw in from the top (allow a shorter end), but the bar may have to be slightly larger in diameter to give the grub screw something to bite against.

    Michael

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