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5th Sep 2019, 05:54 AM #16Philomath in training
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- Norwood-ish, Adelaide
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11th Sep 2019, 09:16 PM #17
I have done a quick dimentioned drawing of my lathe spindle.
I can't seem to attach a pic to a PM, so will post it here.
It might be of interest to someone anyway.
800x800.jpgBrad.
Every Day might not be a good Day,
but there is something good in every Day.
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15th Sep 2019, 12:43 PM #18
OK, I have had some progress on this project. I have been talking to 2 members about carrying out the work for me, but at the last minute started to do some myself. This was after I discovered that I can in fact cut imperial threads on this lathe.
I went into Mackay on Friday to chase some bits of metal to use, after a few dead ends, and not wanting to purchase full lengths, I went to one of the bigger machine shops ( Ziggy's ) hoping for some scrap bin cast offs.
Ziggy was most helpful despite having only a few minutes spare due to a meeting about to start in the office building.
I told him what I wanted to do, he disappeared out the back and came back with a few offcuts, a piece he said would be good for the dummyshaft ( I can barely read the numbers that were marked on it, the last number is a 5 ), and a couple of bits of 4140 that he said would be suitable for making the collet chuck.
Though I am not too sure about me being able to cut the internal thread in this stuff. I am also not yet convinced this is the best material to use for this purpose.
Anyway I ground up a 60 deg. cutting tip out of some 3/8 Seco WKE 45 ( HSS-Co ? ), I chipped the cutting tip a couple of times when I got to the end of the thread and wasn't quick enough on the stop button.
So after a bit of perseverance, I now have a dummy spindle shaft.
DSC_0240.jpg
So now to decide my next steps. I don't have the tooling to cut the internal thread.
I always love to have an excuse to buy more tools, but I am not sure how I will go cutting this thread in a blind hole, and will my gear be up to cutting 4140 anyway.
Or do I send the dummy shaft to someone with a bit more experience than me, and get them to cut the internal thread to suit.
Does anyone have any thoughts about the suitability of using 4140 for the job, if no good, what is the preferred material ?Brad.
Every Day might not be a good Day,
but there is something good in every Day.
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15th Sep 2019, 01:31 PM #19Most Valued Member
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- May 2011
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- Murray Bridge S Aust.
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To make an intenal threading tool, you could weld a piece of MS onto a piece of HSS and then grind it to shape. Others with more experience may chime in and comment,
But if the tool was inverted at the back of your already machined piece, provided that you take light cuts, you should be able to run the lathe in reverse, leaving it as set up for cutting the external and cut the threads that way. The reason for light cuts is so that the chuck doesn't unscrew.
Start from the inside and work away from the chuck, as your confidence builds, you'll then be able to cut the conventional way.
HTH.
KrynTo grow old is mandatory, growing up is optional.
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15th Sep 2019, 03:55 PM #20Senior Member
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- Jun 2005
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- Townsville, Tropical Nth Qld.
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- 225
Brad, sounso like you could have a 2" UN8 thread on that lathe, only real way to know is to use thread wires and check the online tables. You can also get onto YouTube and look up thread cutting by Joe Piecynski, or similar, he has a good video on cutting threads to shoulders.
Rgds,
Crocy.
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15th Sep 2019, 07:31 PM #21
Hi Kryn, Guys,
No don't invert the tool ! this means that you will be cutting towards the chuck. Into a blind hole there is a real risk of hitting the bottom.
For an internal right hand thread, yes, run the lathe in reverse with the tool the right way up. and cut on the far side, cutting away from the chuck.
For a left hand internal thread run the lathe in the normal direction with the tool the right way up and cut on the side nearest to you, again cutting away from the chuck.
Admittedly you will need left and right hand threading tools. I have boring bar type carbide insert tools to do thread work. I admit that I've made a boo boo several times getting it wrong and cut the wrong hand thread.Best Regards:
Baron J.
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15th Sep 2019, 07:34 PM #22Most Valued Member
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- Jun 2007
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- sydney ( st marys )
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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.
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15th Sep 2019, 08:53 PM #23Senior Member
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- Oct 2010
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- NSW
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- 177
Stick with it Brad. I've never regretted going down this path.
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15th Sep 2019, 09:28 PM #24Most Valued Member
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- May 2011
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- Murray Bridge S Aust.
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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.
KrynTo grow old is mandatory, growing up is optional.
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15th Sep 2019, 09:28 PM #25Golden Member
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- Jun 2007
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- Vic
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- 48
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I thought the imperial is 55deg instead of 60deg? I cut mine in reverse with HSS
20190915_201529.jpg
20190915_201617.jpg
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15th Sep 2019, 09:32 PM #26Most Valued Member
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15th Sep 2019, 09:39 PM #27
Nice threading tools. I've gone with carbide inserts simply because I've never been able to get the angles right.
Imperial Whitworth is 55 degrees, however UNC/UNF threads are 60 degrees. This can sometimes lead to confusion with thread identification when using a thread gauge or wires.
No offence taken Kryn.Best Regards:
Baron J.
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15th Sep 2019, 09:55 PM #28Golden Member
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- Vic
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Oh no, I've been doing 55deg all that time!
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15th Sep 2019, 10:27 PM #29
I like the sound of working away from the chuck, but a bit worried about the chuck unscrewing.
Hi Crocy, its closer to 1 15/16 x 8tpi, but not quite, all the measurements are metric, the only thing Imperial is the thread pitch. I don't understand why they did it this way, its not as though it matches any standard tool sizes, even the MT4.5 headstock makes me shake my head.
Thats correct, the tool will have to be up the right way to be able to cut in reverse.Brad.
Every Day might not be a good Day,
but there is something good in every Day.
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15th Sep 2019, 10:39 PM #30Philomath in training
- Join Date
- Oct 2011
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- Norwood-ish, Adelaide
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- 59
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- 6,541
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.
P1040585.JPG
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
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