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Thread: My Widgets
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7th May 2020, 06:31 PM #1Golden Member
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My Widgets
I am very new to machining and not very good - just as well I like to learn!!
Today I made some widgets - they are spacers/washers that adapt an M12 bolt to an M20 hole. I was in a rush so was not concerned about the finish although I feel it would be good practice for me to always try to work to a tolerance and to get a nice finish.
My post is a question and not a show and tell....... to make these I took a 33mm rod of 4140 and drilled a 13mm hole in the end. I then used a parting off tool to mark the left and right hand side of the smaller diameter section. I then used a left hand tool with a WNMG insert to take out the excess material between the parting marks down to 22mm. I then finished off with the parting tool again and took out the remaining material that the left hand tool could not access. I then parted it off and repeated the process.
Eventually I came to grips with the parting off tool and realised that 90rpm was needed to stop the chatter so I dispensed with the left hand WNMG tool and only used the parting off tool.
Being new to machining I only have a left hand and right hand tool holder for WNMG and a parting off tool. I do have a small range of tool holders that take HSS but nothing of any quality. My lack of tooling is why I followed the process that I did.
Given your larger range of tooling availability, what tools and what process would you have followed????? This may help me identify what other tooling I should invest in.
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7th May 2020, 07:41 PM #2Most Valued Member
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You could pass the material through the chuck, machine large OD if required .
Machine smaller OD to required diameter and length.
Centre drill , drill your clearance hole to required length.
Chamfer drilled hole, chamfer small and large OD .
Get your self R hand CCMT or TCMT tool holder, the photo you show of your tool looks to be a CCMT tip NOT a WMCG.
Part off, after all has been done then face your large OD to required length chamfer thedrilled hole and chamfer the large Od.
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7th May 2020, 07:53 PM #3Golden Member
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Cheers pipe. It is def a WNMG. I will look to get some CCMT or TCMT as they look like they will be much easier to get in there.
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7th May 2020, 09:41 PM #4Gear expert in training
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CCMT/CCGT are usually the "go to" insert for smaller lathes; M for steel and G for ally and brass, 0.4mm tip radius should get you through most jobs, or 0.2mm if you are taking light cuts. Get a selection of boring bars for the same insert style as well; 8, 12 and 16mm should cover it.
DCMT/DCGT use a 55 degree insert and can be handy for getting in close to the tailstock where a live centre can block access with an 80 degree holder, especially on small diameters.
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8th May 2020, 05:55 AM #5
Hi Mk1
I'm curious as to why you made the top hats the way you show, particularly if you can pass the length of bar through the spindle into the chuck. I note that you appear to have a mounting point on the back of your cross slide that would take a rear parting off tool holder. That would be a worthwhile addition.
You ask how others would make these parts. Since you don't look to have turned anything off the outside of the bar, I would face the bar end, centre and drill it two or three top hat lengths deep. Then machine the small diameter for the length you require and then part off the piece. Repeat until you have the number of parts that you want. If you want to chamfer the rim, simply put each one in the chuck in turn. The same with the bore.
Though depending upon how close a tolerance you were working to, I would make a mandrel to finish them off.
I only use HSS tools, so grinding up a tool is no issue, done carefully the same tool bit can be used for several operations on the one workpiece.
HTH.Best Regards:
Baron J.
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8th May 2020, 07:35 PM #6Golden Member
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Baron, the way you described it is exactly the way I did it although due to my small range of tools, machining the smaller diameter was a pain. Didn't know you could have a toolholder on the back of the cross slide. I have never been able to find any info about Erikson lathes.
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8th May 2020, 09:52 PM #7
Hi Mk1,
I don't know about your particular lathe, but I've seen lathes similar that have a fairly large block with a bolt through and a key on one edge that sits on that pad at the back of the cross slide. They have a slot similar to the normal tool post and square head screws in the top to clamp a tool. You could easily put a parting blade on there.
I'm not sure but I think one of the places that I visit occasionally has a couple of lathes like that. I'll ask if I can take a picture of one next time I visit. No promises though. They are not working at the moment, not quite sure why. I don't think they are in lock down !Best Regards:
Baron J.
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8th May 2020, 11:55 PM #8Most Valued Member
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My Widgets
I’d have said the same as Pipeclay - doesn’t look like a WNMG to me. Point angle doesn’t look sharp enough, and the sides look straight - not double angle.
Got a photo of an insert by itself?
I’ve got WNMG tools and would have done that with a RH tool holder, turn the small diameter, drill deeper than the length of the part, part off. Chuck the parted piece by the small diameter to face it.
Edit: doh! - amended to RH tool holder
Steve
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9th May 2020, 09:53 AM #9Golden Member
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Why didn't you use the right hand tool to turn the 20mm diameter on the end of the bar first then part off to length?
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9th May 2020, 07:24 PM #10Golden Member
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Based on replies above I think I got so blinkered that I had to have the large diamter THEN the small diameter that I didn't think about a RH tool being able to do the small diameter then part off to create the Large diameter. My inexperience showing!
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9th May 2020, 07:36 PM #11
Hi Mk1,
I did wonder if you understood my post ! When your reply and pictures differed.
Anyway don't fret about it, we all have to learn !
I originally came here to this forum because I wanted to take up machining as a hobby after I retired, and this forum became my teacher. A great many people have helped and encouraged me on here, for which I'm very grateful. There is a world of difference between knowing what you want and how to achieve it.Best Regards:
Baron J.
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9th May 2020, 07:43 PM #12Golden Member
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Reading back I think I did misunderstand your post - sorry.
To date my teachers have been Adam Booth, Keith Fenner and Keith Rucker!!!! I am learning now ready for my retirement in 10-15 years time.
I hope to learn from the members of this forum and then one day be able to give back.
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11th May 2020, 08:09 AM #13Novice
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Newby too!
As a newby i want to learn all different processes, but I thought i would add my 2 cents to see if how i would have done it would be good , bad or ugly!!
My approach would have been,
Face off the end
centrepoint the end then bore as far as i could knowing I wanted multiples of the finished bush,
come in the width of the wider section the same direction as Mk1 did
turn the narrow section the width of 2 finished bushes plus the parting off tool width and a few mm, thus giving me access room for the tools,
Chamfer corners
then cut to length bush 1 with parting off tool,
face end of the second bush to length,
Part off bush 2 then repeat for additional bushes.
Is this process wrong or just another way to skin a cat?
Thanks Darren
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11th May 2020, 06:43 PM #14
Hi Darren,
Just another way to skin the cat !
However the further the works sticks out of the chuck the more that it will deflect when cutting, so supporting the end becomes necessary. Plus if you need high accuracy and repeatability working close to the chuck is preferred.Best Regards:
Baron J.
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11th May 2020, 06:53 PM #15Gear expert in training
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