Workshops/Spinning top

From rLab Wiki

This workshop covers using the Lathe to make a basic metal spinning top. There is a cost of £10 and it is expected to take 4 hours. The induction includes a level-1 induction on the lathe as well as some elements of level 2 induction.

The spinning top is approximately 40mm tall and 30mm diameter, the shaft is made of stainless steel and the weight can be either stainless steel or brass. You will learn how to hold materials in the lathe, how to make them parallel and flat, how to produce tapers and simple threads, how to join pieces together and how to produce various surface finishes. At the end of the workshop you'll have to spinning top to take away.

It would be sensible to wear old clothes as there will be grease and metal residues. A short-sleeve shirt is best and be aware that you'll have to take off any rings or watches and put them somewhere safe.

File:Spinningtop.scad

This table is work-in progress, do not use yet

Topic Detailed contents Rationale
Proper Clothing
  • Sleeves tied back, no loose or flowing clothing, long hair tied back, risks of rings, proper footware.
  • Mention the catch points of the chuck and the 2 powerfeed screws.
  • Mention the main slide handle can catch things, mention loose clothing can catch the handwheels and upset work.
Obvious Safety issues, don't want to get pulled in!
PPE
  • Goggles when using lathe, gloves possibly for loading/unloading sharp objects but NEVER while actually using the Lathe.
  • Proper positioning of the guard and warning that it's mostly to catch splatter and offers only limited protection
Basic safety information
Nomenclature The proper names for all the various parts of the Lathe Got to have common language to communicate effectively
Start-up/Shutdown
  • Location of main power switches, location of the 2 E-Stops, using the control lever most of the time but it's OK to use the brake peddle as a normal stop if the part geometry makes it necessary, location of card reader once we have it.
  • Clean the lathe off before use if it's noticeably dusty, especially the slideways.
  • Turn the Lathe off whenever you leave it, even briefly.
  • Putting the "Out of Order" sign on the lathe if you see a problem and notifying maintenance team
Stopping and starting! Turning off when unattended in case someone brushes power lever
Oil System Location of the 3 sight glasses, what they should show, who to contact if they don't, using automatic one-shot oiler Don't want people running the machine when dry
Materials Selection Which materials can the Lathe operate on, types of metals and their properties, plastics that can be turned and modifications needed to do so, materials that cannot be used on the lathe.
YES NO
  • Regular Steels
  • Aluminium (with caution)
  • Brass
  • Acrylic
  • Nylon (caution about long swarf)
  • Delarin
  • Wood (but see level 2)
  • Polycarbonate (but see level 2)
  • Ceramics & Glass
  • GRP & Carbon Fibre
  • Hardened & chromed Steels
People need to be able to choose the right material for their project, other materials to be covered in Level 2+ Inductions
Mounting the tools
  • The advantages of HSS (cheap, robust, resharpenable) and why not to use carbide till level-2
  • Brief visible inspection of tools before fitting, checking for sharpness
  • Holding the tools in the holders, keeping as little as possible sticking out
  • How the holders grip properly and how to fit them into the quick-change toolpost and tightening the toolpost.
  • Mention how to set the toolpost to perpendicular
  • Angled tool positions for cutting slopes

Cover Steel and carbide tooling

The 3 tool types
  • HSS/Tungsten-Steel tools are robust, easy to use and can be reground indefinitely but are limited by temperature and best used with copious coolant/lubricant if making heavy cuts.
  • Brazed carbides can be sharpened to a razor edge and take fine cuts but are the most brittle and although they can be resharpened we can't do it at the lab, they have to be sent away.
  • Cemented carbide insert tools are hard, wear-resistant, usually have a anti-friction coatings, they're less brittle than brazed carbide but still chip easily but paradoxically hate being used too gently, because of their coatings they're not as sharp as the others.
  • Carbides must never EVER be stopped inside work, and cooling should be flood or not at all, never intermittent.
  • Using the wall chart to select the proper spindle speed for each tool/material combination
Setting tool height
  • Locking/Unlocking the tool height adjustment - Adjustments can only be made when unlocked, comparisons only made when locked, setting it using the live-centre in the tailstock
  • How accurate this needs to be and effects of getting it wrong.
    • Too low - Tool grabs and work rides up
    • Too-high - excessive friction and tool failing to cut.
  • Don't adjust unless obviously quite far out as they're normally left correct

We'll get a lot of broken tools if this isn't done right

Tailstock mounting Fitting the drill or the live centre, aligning the tang, keeping the tapers clean and dry, ejecting the tool Need to know this to set tool height
Mounting Workpeices and changing chucks
  • Inwards gripping only using the 3-jaw chuck
  • Smallest amount possible exposed, maximum of 3-5 diameters, large/Long/Delicate pieces can't be held at this level of induction
  • Use of the through-bore
  • Approximate truing and even tightening
  • The 3-jaw is not accurately concentric, so don't take workpiece out till you're finished
  • Not leaving the key in the chuck!
  • Use the bed protector at all times when changing chucks
  • Toecap boots a good idea when changing chucks.
  • How the camlocks work and who to call if they're out of spec, even tightening, alignment marks, where the chucks are kept.
  • Keeping the nose and taper spotlessly clean.
  • How the 3-jaw is quick and easy but doesn't hold concentrically, how the collet chuck does but only grips smaller objects. Collet chuck is preferred for materials that it can hold.
  • Making sure Lathe is left with 3-jaw fitted with it's jaws set in inward-gripping mode and correctly balanced must always be left in the lathe when after you're done.

Holding the work securely in the 3-Jaw and Collet chucks.

Using the collet chuck
  • Changing the collet and respecting the keyway, tightening up evenly and remembering to take the key out.
  • No speed limit on this chuck but can hold round or hex bar only.
  • Holds concentricity accurately and work can be removed and replaced repeatedly.
  • Grips tighter than the 3-jaw on the same material but can also use internal supports for delicate objects, but the minimum grip depth must be respected.
  • The 3-jaw must be put back in when you're done

Just general use like the 3-jaw

The 3 slides
  • Mainslide for fast parallel moves but warn it's easy to slam the tool into something, can be used for turning when absolute parallel motion is vital but usually much easier to use top-slide.
  • Cross slide for perpendicular moves, show how the dial works and how to zero it and mention that's it's calibrated for DIAMETER and not radius
  • Top slide for small controlled reasonably parallel moves up to 100mm long, describe how it can be used to cut tapers and how to re-set it to parallel. Don't cover details of taper-turning, that's level 2 induction.

How to move the tool around!

The Lamp
  • Positioning the mag-base lamp properly, taking care that it won't foul over the full range of motion intended. Beware of stroboscopic effects.
  • Main light doesn't work but if it gets fixed it will give non-stroboscopic light

Getting a clear view, and not being fooled by strobe effect

Make sure feeds are off
  • Making sure that the powerfeed and screwcutting feed are disengaged before starting up the Lathe.
  • The two levers that control then and what the disengaged position is.
  • Warn how fast things can go wrong if they're left engaged!

Don't cover using the powerfeeds for induction this workshop since that will require also covering how to select suitable feedrates or we risk someone just using whatever the machine is currently set for with possibly harmful results.

Facing off the brass bar
  • Crude positioning using the main slide, then actual job done on the cross and top slides
  • Lathe mustn't be stopped with the tool in the work
  • Show how to touch on then zero dials and advance suitable amounts, what is a suitable amount?
  • Remembering to compensate for backlash in all 3 slides
  • Smooth even movement using 2 hands on the slides.
  • Cover listening to the tool and the machine, grinding noises or audible loading of motor are seriously bad
  • Wind in to just past the centre and then out again
  • Cover going slower near the centre and what it means if there's a nub left or the tool tries to ride up (tool height wrongly set).
  • Cover warning signs of very bad chip form(all materials) and colour(steels)
    • Discrete small chips with a slight yellow colour are best, silver is fine, blue is too hot for HSS.
    • Long ribbon swarf although not ideal is acceptable, very small chips, dust, or "vanishing" chips are rubbing and NOT OK.
  • What a nub means and what the shape of it tells you
  • Roughing passes and a finish pass.

Covering the very basics of Facing off

Parallel Turning
  • Picking the correct slide for the length of cut, positioning correctly at start of cut.
  • Touching on and zeroing dials.
  • Smooth even progress using 2 hands on wheel.
  • What good chip form looks like.
  • Reasonable depth of cut for roughing.
  • Accurately stopping at the same place on multiple passes.
  • Coming to an accurate diameter and depth of shoulder
  • Limitation on doing long cuts (can't do them at this induction level) or working on small diameter workpeices (need for much shallower cuts and care over tool forces)
  • Finish pass and cleaning up the shoulder.

Basics of Parallel turning

Drilling
  • Mounting the drill chucks in the tail-stock.
  • Maximum drilling capacities for each chuck.
  • Selecting suitable drills for the material.
  • How to move and position the tail-stock
    • How to lock it off
    • How to advance the quill.
  • Selecting suitable speeds using the table on the wall (2 flutes so 50%).
    • Using centre-drills to start the hole.
  • Maximum drilling depths is 5x diameter
  • Using the dial on the tail-stock to pick a depth
  • Depth from tip and depth from shoulder drilling.
  • Feeling for suitable feed rates and the symptoms of too little/too much feed pressure
  • Watching out for thermal issues, flood coolant preferred.
  • Coolant is non-corrosive and doesn't need to be wiped off after
  • "Pecking" drill pattern.

Using a drill safely and to the target depth

Parting off
  • Using the HSS parting blade only at this level
  • Setting tool stick-out, cover maximum parting depth based on the tools protrusion and absolute max (20mm depth of cut), Checking tool height
  • The need to ensure very accurate perpendicular tool positioning and precise and very even movement.
  • Parting should be done at less than 35% spindle speed compared to other cuts and why that is
  • Use of copious cutting lubricant and frequently reapplied or ideally the flood coolant.
  • Riding the boundary between slip-start and continuous cutting

Ideally people should be able to do this to use the lathe properly but induction level-1 shouldn't cover grooving or use of carbide

Cleaning
  • No workpiece left in, no tool left mounted, nothing in tailstock
  • Picking up swarf, watching out for sharp edges and cuts.
  • Draining swarf if you've used flood coolant.
  • Where to put the waste swarf.
  • Wiping down the machine and especially the bed, reoiling after wipe down if heavy cleaning was needed.
  • Cleaning the guard
  • Mopping up any spilled coolant
  • Don't expect the lathe to be left spotless, just all the swarf gone

Keeping the Lathe clean!