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Re: DIY Lathe, bed leveling question
Tkamsker,
I'll sketch up some drawings for the tail stock today.
Another confusion on the design is the spindle. There are different types of spindles. What type would you recommend? I need to build a spindle which has to have a large bore (40mm).
Here are some spindles that I found on google.
http://www.cnczone.com/forums/attach...d=347578&stc=1
http://www.cnczone.com/forums/attach...d=347580&stc=1
Re: DIY Lathe, bed leveling question
Hi
for the spindle i would search and do an pneumatic open close collet. Isn't it ? There you get from the vendors proven systems and integrate them
To build an spindle you need a very good an accurate lathe ,.. (and you have an optimum lathe as far as i know ) so maybe it makes sense to buy this stuff and have then the ability to do little series as fiddling around with the stock itself ,.. ?
look at bison or similar types
Re: DIY Lathe, bed leveling question
Hi,
I really don't need a pneumatic spindle-chuck system because I will cut mostly big parts that takes long time to machine so I'm fine with a chuck /w key : )
The lathe I have has a flange type spindle and I'm changing the chuck by removing the 3 nut. I'm fine with this but I wonder if the threaded type spindles are more accurate and rigid.
Re: DIY Lathe, bed leveling question
I will add some comments, and please don´t get offended.
1.
For a 1.5 m long lathe, go look at any commercial lathes of this size.
The section size, ie depth and width, is the minimum You want.
Bigger is better.
2.
The linear guides You need, as in absolute minimum, are 35 mm in size, if You are going to make a lathe 1.5 m long.
At issue is rigidity, not strength.
Rigidity scales as length cubed.
So, vs a lathe of half the length, 75 cm, a lathe 1.5 m long MUST BE 8 times more rigid.
This also means, in practice, 8 times more strong,
In practice You would also want it to be 8 times heavier.
I am speaking as someone who actually has scratch built a VMC, 5 times.
The same machine, now on version 5.
A big machine.
I also measured the rigidity every time, on each of the 4 versions.
Now, I am using size 35 mm linear guides, and they are doubled on the front.
Yes, 4 rails on front, 8 linear guide carriages on front.
And 2/4 at the back.
And it is a double column machine, 8 times more rigid than a typical C frame.
I I can assure You based on measurements with a DTI, that all the previous versions were very floppy, vs the current one.
Another example.
On the mill, the steel beams that carry the linear guide rails, are 20 mm thick tool steel, and 200 mm tall.
They are 2.2 m long, for a working area of 1600 mm, or the table width.
Then the linear rail is bolted on top, for a total height of 235 mm.
This is absolutely necessary, and is about 100x-200 more rigid than version 2 of the machine.
As measured by DTI.
Again, go look at commercial lathes.
Use the same size in width and height, made from flat steel plates of 10-20 mm thick. 20 mm or 30 mm is better.
Bolt everything together.
Granite is very flexible. So is epoxy granite. About 3x more than steel.
But it absorbs vibrations very well.
I already have the steel, servos (6), linear guides (35 mm) for a CNC grinder.
Tool and cutter grinder.
30 mm thick, 200 mm tall.
1 m or 1000 mm long.
Working area is only about a sheet of paper 30-50 cm.
Next post will be my recommendations, and they are based on looking at about 2000 machines, in 200 shops, in 5 countries, and special factory training from the nr 1 builder of commercial machines.
I used to sell commercial USA made machines, here in Spain, as the sales manager, with 8 guys in sales.
You are trying to make a big lathe, of commercial size.
A commercial sized lathe needs commercial sized pieces.
A 40 mm passthrough needs a spindle of the same size as a 13x sized lathe.
My rigid, very good, 12x light industrial lathe (ie it is twice as heavy and rigid ! as most small 12x lathe. Good.) Has a 38 mm passthrough.
So you will want spindle bearings of about 50 mm inner D, or bigger.
Look at spindle bearings and spindles used on 13x sized lathes.
Look at the best lathes made and sold.
Whats worked well.
The common point will be that EVERY single especially good lathe is twice the mass of the average ones.
These are for example the;
Monarchs
Hardinge HLVH
Sharp, Feeler, copies of the Hardinge.
Next post, suggested sizes based on my experience. Fwiw.
Re: DIY Lathe, bed leveling question
Suggested sizes for a commercial-type lathe:
Needs and desires;
1.5 m length, and 40 mm passthrough at spindle.
The 40 mm is the hard part, thats why You have to have big bearings, and a tall HS.
Approx 400 mm tall headstock.
HS 500 mm long. Thus spindle == 600 mm long.
20 mm walls.
Any steel will do.
About 10 mm wall for spindle.
So 40 mm + 2x 10 mm => 60 mm inner D of bearings.
Bearings:
7212 AC or something like that.
About 250 mm depth on bed, and 350 mm height.
400 mm would be better.
Walls 10-20 mm thick. 20 mm is much better.
For ref: a decent 12x lathe is approx 200 tall, for a length of 24" or 600 mm, and this leaves about 350 mm working length between a 12" chuck and the TS.
Going from a 600 long to a 1500 mm long bed, you would want to approx. double the height.
You want the bed to be about 1000 kg-1500 kg in mass, and the HS to be maybe 2-300 kg.
With the filling EG.
CLOSE the headstock, rigidly.
This makes it rigid.
A thick bottom plate and thick top plate is one good option.
An enclosed box is vastly more rigid than one with the top open, like most manual lathes made in cast iron.
You can then drive the spindle from the end, via belt drive.
This is what I do NOW, and it works extremely well.
So I do NOT drive the spindle from inside the HS, like the original drive was.
I changed to a toothed belt, and and AC servo drive, of 2.5 kW, 220 V.
I drive it with 1:3 ratio via HTD pulleys.
This works extremely well.
And the lathe now has 0-1000 rpm, and over double the torque it had originally.
And the torque is now 90 Nm from 0-1000.
The Ac brushless servo and timing belt drive works extremely well.
And I have no belts, gears, etc. at all.
From my experiences, I would guesstimate about 300-400 kg in steel.
Steel is easily, fast, sanded flat enough for linear rails, to 0.01 mm or near it.
Use about 50 mm width, and a large belt sander.
The edges of the 50 mm width will be rounded. But the center will be flat.
You can then fine tune it if you want to, or need to.
I have not needed to.
And you can always shim or scrape, as accurate as you want, by hand.
You will need a precision ground granite flat, or ground steel edge, to test the straightness and flatness.
About half the length, or longer.
These cost about 300-500€.
0.02 mm accuracy, or so.
A veritas ground steel rule of 800 mm iirc was about 120€, but it is only 0.04 mm.
I built my long beds flat by bolting them against a granite surface plate, of 600 mm length.
So I used a 20x50 mm flat, and clamped it against the surface plate.
This makes it flat in a gross sense, since it follows the surface plate.
I then bolted a stiffener against the flat, from the sides, every 60 mm. 6 x 30 mm SHCS.
Drill, tap, in place, the 200 mm tall stiffener is now fixed to the 20x50 mm flat.
Move 300 mm, so the next section is 300 mm along.
Clamp, drill, tap, repeat until done.
Took about 40 bolts / bed, times 2.
About 30 work hours.
Worked fine.
The 2 machine builders ground precision rules, one 50 mm (50€ or so) one the 800 mm veritas, easily show errors like bends, of 0.02 mm or 0.01 mm.
Then mark with magic marker, and sand until magic marker is gone.
The gradual bend is now about 0.02 mm less.
So I did not have a 2.2 m long granite flat, and use hi-spot blue and rubbing etc.
Worked fine.
Dirty, noisy, tedious, heavy work.
But quite fast to do, and not difficult to do.
Linear guides run fine.
HTH.
Sorry no pics now, for commercial reasons.
Re: DIY Lathe, bed leveling question
Hi Hanermo,
I can't have a machine that heavy in my garage. I'm just a hobbyist. Maybe it's better buying a 60-80cm old lathe and do a retrofit.
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Hi Hanermo,
I can't have a machine that heavy in my garage. I'm just a hobbyist. Maybe it's better buying a 60-80cm old lathe and do a retrofit.
Re: DIY Lathe, bed leveling question
By the way, 60cm length between centers is more than enough for me. So I can decrease the length and it will be /w headstock about 80-90cm in total.
Re: DIY Lathe, bed leveling question
I'm still thinking about it.
http://puu.sh/tSNFH.jpg
Re: DIY Lathe, bed leveling question
No news? im interested in follow your design :)
Re: DIY Lathe, bed leveling question
Sorry, project cancelled due to rigidity concerns.
Re: DIY Lathe, bed leveling question
The last design looks very similar than pur lathes ;)- And they are cast iron ,.. We work on an Tailstock move for our lathe as well
best reg thomas