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Pages and Files
Table of Contents
Current Design Drawings
00 - Introduction
How To Build - Beginning
How To Build Part 1 - Concrete Bed
How to Build Part 2 - Machine Ways
How To Build Part 3 - The Carriage and Cross Slide
How To Build Part 4 - A Temporary Lathe and Mill
How To Build Part 5 - Spindle
How To Build Part 6 - Tailstock
How To Build Part 7 - Threading With A Thread Follower
How To Build Part 8 - Tooling And Coolant
Buglist - Known Design Issues
Note to early machine builders
Cole drill project
Genny generator resource page
Add "All Pages"
How to Build Part 2 - Machine Ways
How to Build Part 2: Machine Ways
The ways are the most critical component of an accurate lathe and careful searching for the steel for ways and accurate way alignment is very important.
Yeomans' used specially ground and hardened round bars that would be too expensive for our machines.
We have these common choices:
Pipe or round bar may not be truly round or straight . Pipe should be made more rigid by filling with non shrinking grout. If your budget allows for machining in a lathe then do it but don't expect great results because many lathes will be too worn to machine the way to the exact size over it's entire length.
Hydraulic piston rods come in a variety of flavors, imperial US, metric, straight, bent, chrome plated, rusty etc. You will need 2 the same size and they may not be as long as you need but are worth a very serious search.
In Developing World conditions, the steel from drive shafts may be the only affordable answer but it may take a long search to find two that are straight and also the same diameter. In desperation you could use ways of different diameters, it would be best to put the larger way on the side away from the operator since this is where cutting forces are directed.
Used or new pipe, piston rods or drive shaft sections must checked for straightness. The best way to do this is to put the 2 pieces side by side, rotate one while pressed against the other and use a feeler gauge or bright light from behind to check for a gap.
Fortunately there a way to (slowly) repair inaccurate ways using the "3 rounds" method.
grinding precise round ways SA 1954 08 (1).pdf
(It would be great if someone would like to design an easily made, scalable device for this wonderful technique.)
Wrapping the ends of the ways with greased sheet metal will allow the ways to be rotated when they wear. All lathe ways wear eventually and round ways that wear against a flat surface will definitely wear more quickly than most others. The advantage of our design is that wear is so easily repaired. Rotating the ways with a pipe wrench that has padded jaws and replacing the wear strips will bring the machine back to new condition, something impossible with regular lathes.
Wrap the ways tightly, carefully hammer the sheet metal over the ends and hold everything together with hose clamps. You can then replace the hose clamps with tightly wrapped tie wire if you need to re-use them. To make absolutely certain that no corossive concrete touches the ends of the ways, a thin layer of drink bottle plastic could be added to the sheet metal sandwich.
Ways alignment, a most important operation.
Use a piece of steel bar as a gauge to set way separation. Be certain the bar is level and at right angle to the ways when you measure.
Next you need to put the ways level and in the same plane.
Even though a carpenters level is not accurate enough for machine building, it is a place to start since a Starrett machine quality level costs $700. Another possible choice is a Grizzly (grizzly.com) machine level is $61.25 in the USA. I am certain there is a difference in quality but the cheaper one is adjustable and accuracy is claimed to be .0005" over a 10" span. If you have found or made really accurate round ways, you should seriously consider buying one of these to take advantage of the accuracy you have achieved so far . Besides insuring that the ways are level and in the same plane you will also be able to level the spindle and use it many times during carriage and cross slide construction.
BUT! A $61.25 machine level (in the USA) may be more money that the machine builder has available for the whole project.
n this case a 300 mm square piece of plate glass could be a substitute.
Carefully adjust the ways with the best carpenter's level that you have then place the piece of glass over the ways and check for any gap between it and the ways with a feeler gauge. Rotate the glass to be sure that the glass is truly flat and that any error shows up in the same place. Check to see if the ways are level by putting a ball bearing on the glass and then tapping the glass lightly if the bearing does not move at first.
Finding a material that would replace the carefully poured type-metal took a lot of thought. It had to be easily poured, cheap, available almost everywhere and have sufficient strength to hold the ways and spindle in place.
The only material that meets these specifications seems to be common non-shrinking cement grout used by tile setters.
So thats it! With non-shrinking grout, $61 level (or a piece of plate glass and a ball bearing) and a $10 dial test indicator you will be able to do the job a large factory with 20 different assembly jigs used to be used to do
(but much more quickly).
Next is a job that will also take care, the support bar that fits under the ways. Gravity works everywhere and while the Yeomans lathe patent did not show a support under the ways, it must have proved necessary in practice since he added a large support in the middle. I added support along the whole front half of the way as a way to suppress vibration caused by taking a deep cut in the workpiece. The most tedious part of the way support is the cutting of the slotted holes. Drilling two side by side holes and then using a file to make slots will work here. Be careful here because a sloppy job will really show!
The way supports are shown many times in this "How To". They are extremely important not only to handle the gravity problem but also as a way of transferring cutting forces to the lathe bed. These forces can be immense if the cutting tool is dull, the wrong shape or poorly adjusted. Forces of this magnitude will be common when someone is learning to run a lathe.
If you don't have experience drilling accurate holes then try this. First use a scriber to make an "x" where you want the hole to go. Next slide a sharp, light center punch so that you can feel the center of the x and tap it lightly. If the punch mark is not exactly in the right place then move it over by center punching at an angle. If in the perfect place then punch it harder with a heavier punch and drill a small pilot hole. Just start the pilot hole and then check again for proper location. If off drift the hole over with the large center punch. If OK then drill a second pilot hole and keep increasing the drill size to get the proper holr size. A slow way to do things at first but much faster than trying to correct a hole that is even slightly in the wrong place.
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