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Thread: Homemade lathe in the making?
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6th Apr 2020, 04:20 PM #61Most Valued Member
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Picked up all my material thanks to anyone that wants to join along and offer advice, i over ordered on the steel i had a drawing and done all my calculations than ordered the steel than went to measure my lathe to my surprize i thought my lathe was 400-450mm i measured it to 320mm without the spindle attachment bugger! Now i need to down scale
The shaft is 30mm as is the 10 bearings inside diameter, i had ordered 600mm of shaft but i am going to have to scale the project down a little and improvise but not cut any unneccasary corners i may not be able to run all 10 bearings tho
The shaft will need to be cut around 300mm to fit on the lathe i will likely need to machine it down .04-.05mm just so the shaft slides thru the bearings if it machines uneven i'll get a 32mm 35mm shaft and machine that i just expected the 30mm shaft to fit 30mm bearings
One piece of steel was missing the top piece or the shelf both same size
I got the nice big chunks of steel 90x85mm long/wide for my bearing housing
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6th Apr 2020, 05:54 PM #62Gear expert in training
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We all offered advice, you just decided to ignore it because it doesn't support what you want to do
The shaft will need to be cut around 300mm to fit on the lathe i will likely need to machine it down .04-.05mm just so the shaft slides thru the bearings
i just expected the 30mm shaft to fit 30mm bearings
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6th Apr 2020, 06:52 PM #63Most Valued Member
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Ran into a problem i ordered 90mm round bar i got 95.25mm it was just too big for my jaws so i tried to weld a bokt on but a bit hard with the earth lead hanging off the bolt i attemped that twice she spun up but bobbled so i stopped and drilled a center hole now in the process boring it out to 12mm for a bolt to go thru it than on the chuck
If i cant machine this stuff i'll go grab a smaller size, bearings OD is 62mm i wanted a bit of meat to weld on around the sides without collapsing the bearing housing
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7th Apr 2020, 07:16 AM #64Most Valued Member
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You must be a rich man Gazza as you have a constant stream of problems that require you to buy materials two or three times over. I'll give you marks for trying, but your shoestring budgets combined with your skill levels doom you to failure more often than not. Reading this thread is like watching a train wreck in slow motion. You have no idea how a lathe is constructed, why it's constructed that way and what makes it accurate, which is okay as we are all here to learn from others, however you absolutely refuse to listen to reason and the knowledge given to you by others skilled in this field.
Unless I am mistaken, this fiasco started out by trying to avoid paying to have your motorbike cylinder sleeved and has now morphed into the building of a frankenlathe that will be useless (sorry, no other possible outcome) and will most probably destroy your cylinder along the way. I get that you like building stuff. That's great, but pick projects that match your resources, knowledge and skill level.
The notion of machining a bore to take a bearing, welding the component and expecting the bore to still be round and the correct diameter is doomed to fail, that I can guarantee. The same goes for the idea of welding your slide rails in place and welding the headstock. All welds distort and even if you did align things perfectly they will be way out by the time the weld cools.
Elanjacobs is no doubt a skilled machinist and has access to the machine tools that could bring a project such as this to fruition, but I'd wager that even he would shy away from this project and just invest his money in a good second hand lathe that will actually produce good work. You are entering territory that you clearly have no knowledge of, in fact, even if you did have an accurate lathe, holding and clocking the cylinder then boring 90mm deep to the tolerances required for a cylinder bore is not a novice job to be taken lightly.
Stop and think. "Why do they go to the trouble of building lathes the way they do if all you need is some cheap bearings, a bit of mild steel channel, some mild steel bar, a welder and a spirit level?"
For once, listen to the good advice that has been given and realise that some projects are above your skill level, even if you had the tools to do the job or else you will be building the world's most expensive boat anchor.
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7th Apr 2020, 10:48 AM #65Gear expert in training
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Definitely not yet skilled, some days I wonder if I can even call myself competent
Working for a company that manufactures for the aerospace and medical industries has given me a big appreciation for precision work. One of the things we make is a worm shaft with 10mm bearing journals; the official tolerance on them is 8 microns, but the guy who assembles them likes us to keep to a 2 micron window because that's where they work best. And that's for a low speed worm shaft.
We have some pretty fancy toys at work and we wouldn't even think about a job like this one. The spindle would be no problem, but the bed is way too much trouble
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7th Apr 2020, 03:04 PM #66Most Valued Member
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Im no longer building the lathe however i am building the small boring box but just realised u cant cut high tensile on the lathe so a bit of money wasted as my words and old mates hearing were off and those 2 billets were high tensile i just tried to machine it and kept blunting the tool
Any idea how to grind the shaft instead? Billets can be replaced with mild steel
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7th Apr 2020, 03:58 PM #67Most Valued Member
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Elan thanks for the tip on grinding the shaft it measured 30.55mm the inside of the bearing measured 29.92mm i spun the shaft up on the lathe and used a sanding disc once i had a little bit done i put a bearing on the shaft and sanded a little than checked the bearing would slide lots of stop and starting now the bearings fit perfect
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7th Apr 2020, 06:02 PM #68Golden Member
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[QUOTE=gazza2009au;1965796]Im no longer building the lathe/QUOTE]
Gazza,
That's the most sensible statement I've heard all week. You would certainly have regretted it if you had gone ahead.
Frank.
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7th Apr 2020, 06:50 PM #69Gear expert in training
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What kind of tool are you using, what speed are you running, what's the diameter of the part and are you using any coolant or cutting oil?
You should be able to machine it, even on a small lathe, but it sounds like you might be running too fast or with the wrong tool (or a combination of both)
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7th Apr 2020, 08:34 PM #70
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7th Apr 2020, 10:07 PM #71Most Valued Member
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Turning this big slug of a piece it only slows the machine a tiny bit however im not on a fast speed i think it may be the slowest speed, the problem is the tool is going blunt after literally 10 seconds it starts off by peeling off tge steel than just goes blunt its a hare and forbes tool it works great on aluminium and regular steel just this high tensile stuff is brutal
The tool on the yellow head stock is the one i mostly tried i than changed to another tool different brand and that blunt instantly too the tools face was ground like a diamond
My machine is capable of using hhs tools and carbide tips should i change to carbide tips?
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7th Apr 2020, 10:24 PM #72Gear expert in training
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Definitely go carbide if you can.
CCMT type insert with a 0.4mm tip radius will just peel the stuff off, but you have to take a decent cut (at least 0.4mm depth and 0.1mm/rev feed) to get the chips to form properly or you'll get a huge bird's nest of razor sharp stringy cr@p. If you're worried about the depth of cut being too big for your machine, get 0.2mm radius inserts, they will die faster because of the sharper point, but you can take shallower cuts and still have the material chip properly.
If you're going to feed by hand, fold up some chip guards from shim stock and stick them to the tool post to keep the chips off your hands; they're bloody hot, especially if you're cutting dry.
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7th Apr 2020, 10:29 PM #73Most Valued Member
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Mad as thanks and yeah when she was flicking a few chips one landed between my fingers left a burn mark/ blister that popped and stung that metal is really hot
I will try get the carbide tomorrow
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8th Apr 2020, 01:12 AM #74Most Valued Member
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Checked out hare and forbes the carbide tips were $50 i went with ebay $13 cheap man pays twice but at $50 i could buy new mild steel, bought a tin of flux as i already had a roll of silver solder will use the blow torch to solder the tip as on youtube
While im waiting for the order to come i'll start building the box, my bottom and 3 sides are 10mm flat bar had no idea they sold 250mm wide flat bar and in that thickness sad thing is the steel was chopped hydraulically not cut by band saw, top piece is not a full sheet size as i need to look down and view the dial indicator to center the bore to the shaft so the box is 250mm wide, 250mm deep and 400mm high altough i need to trim the height down as i could only fit 300mm shaft in the lathe, the top piece is 250mm by 120mm and 16mm thick box will be all open corner welds so it should all align perfect
No idea as to how to drill the mt2 hole with no room on the lathe so at the stage of testing to see how accurite the set up is i will run either a very cheap second hand aluminium cylinder from ebay than a steel cylinder as a test or i'll test some aluminium pipe and steel pipe to see how true it bores if it works i will go see a machine shop to make up a shaft and drill the mt2 taper so i can run a proper boring bar
Remember if this works its not a one off use i have ran into cylinder problems from the mid 1990's up untill today so something like this will potentioally save me thousands in repair bills not to mention i can help family and friends of my family who are all bike enthusast
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8th Apr 2020, 12:56 PM #75Most Valued Member
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CCMT inserts are intended to be held into the tool by screw thread, not brazed/soldered.
Turning Inserts Identification | MITSUBISHI MATERIALS CORPORATION
CCMT insert tools are the most common type of ‘hobbyist’ tool holder available on evilbay. Have a look there, tools with spare inserts are available quite cheaply.
When you order flat bar you need to check to see if it is being sheared from plate or is actually nominal size flat bar. Flat bar won’t be flat, but it will be a lot flatter than sheared plate. Nominal size flat bar is available in sizes up to 300x25, although whether your supplier keeps it is an entirely different story. Where possible try to avoid flat bar that has been sheared from plate.
The 2MT hole you’ll need to bore a straight hole first to provide access for a boring bar, then you’ll need to setup a boring bar to cut a taper and cut it slightly under size and then put a finishing reamer into it.
If your design allows, look seriously at provisioning it for a drawbar to retain the boring head into the taper.
Looking at your design picture you don’t appear to have any means of vertical adjustment of the boring head shaft. You have the motor drive direct onto the shaft that drives the boring head. Doing that means you’ll need some sort of a slip drive shaft or you have to move the whole shaft and motor assembly.
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