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Tools/metallathe/induction: Difference between revisions
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{{inductioninfo}}
<div id="level1"></div>
== Level-1 induction ==
This is the most basic induction and provides only the absolute essentials.
{| class="wikitable"
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|-
| Proper Clothing ||
* 'Workshop appropriate' clothing - you're going to get dirty and probably splashed with coolant etc
* No open-toed shoes or sandals.
* Sleeves tied back, no loose or flowing clothing, long hair tied back, risks of rings.
* 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.
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* Ceramics & Glass
* GRP & Carbon Fibre
* Hardened & chromed Steels (but see level 3)
|}
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* 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!''' This is the most common source of accidents on lathes and can cause serious injury
||
Holding the work securely but only on a basic level for induction.
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|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.
||
Getting a clear view, and not being fooled by strobe effect
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* 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
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== Level 2 Induction ==
<div id="level2"></div>
This one is to cover people who intend to seriously use the lathe in an upcoming project but who don't need to handle complex or detailed work so quite a bit of what was previously level-1 induction will now appear here. Level-2 induction requires people have completed level-1 induction first and and is broken into 2 modules of 2 hours each.
<div id="mod2a"></div>
=== Module 2A ===
{| class="wikitable"
|-
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|Use of cutting fluids and other lubricants
||
* Using the 3 types of cutting lubricant, the
** Use of proper lubricants for aluminium (the CT-90 is "Universal" and can be used)
** Using the flood coolant system
*** Checking coolant level and topping up if needed, the warning light only reads accurately on start-up
*** How it affects cutting speeds
*** Avoiding spray
*** Cleaning machine after use.
||
Proper cooling extends tool life, allows deeper faster cuts and helps keep machine clean
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|Advanced work-holding using 3-jaw
||
* How to change the jaws, winding them out to release, maintaining number order, getting new ones engaged in proper sequence. Making sure the jaws are left fully engaged when you leave or it's dangerous for others.
* Using it to grip inwards on the regular jaws, gripping outwards on thick-walled tubes/rings using alternate jaws, gripping inwards on large objects using alternate jaws.
* Using internal supports for delicate materials, warn that the small steps on jaws grip less strongly and will require smaller depth-of-cut for roughing.
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|Tool Inspection
||
* Checking the tools with
* Recognising wear and polishing on HSS tools and when it's OK and when the edge had been lost.
* Looking for wear or more likely chipping on brazed carbide, the procedure for getting them re-ground if they need it.
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'''These tables are under development and will be expanded in time, till then, use your best judgement'''
{| class="wikitable"
|+ Typical Depth of cut (DoC) and Feeds for carbide insert tooling
|-
! Material !! Depth of Cut !! Feed (mm/rev) !! Notes
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|-
| Stainless Steel (304) (finishing) || 0.07mm - 0.12mm || 0.05mm - 0.10mm || Can give almost mirror finish
|-
| Titanium || 0.3mm - 0.6mm || 0.06mm - 0.12mm || '''Requires level 3 induction as titanium has additional safety hazards''', requires a brand-new insert and special turning technique
|}
||
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||
Using the powerfeeds for larger cuts is almost essential but proper settings must be chosen to avoid breaking tools
|}
<div id="mod2b"></div>
=== Module 2B ===
{| class="wikitable"
|-
! Topic !! Detailed contents !! Rationale
|-
|Taper Turning on top-slide
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* Different sized boring tools, different end profiles and the types of hole bottoms they produce.
* Minimum initial hole sizes for the boring tools and how they rub if it's not met, raising the cut line only if vital. Using the very large MT3-shank drills in the tailstock to opening out the holes large enough. Using milling cutters held in the tailstock to produce a flat-bottomed starting hole.
** Using the largest boring bar available that can fit in the hole
* Working out the minimum tool exposure necessary for the job and adjusting the boring bar suitably.
* Noting the drill depth accurately and touching on to the bottom of the hole.
* The need for relatively gentle cuts because of the reduced stiffness of the tooling. The use of sharper than usual tooling with more-than-usual rake angle to reduce cutting forces.
** The need for (possibly multiple) spring passes owing to reduced rigidity
* Using the dials to set the depth and calculating depth using cross-slide for tapered holes.
||
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|General oiling
||
* Which grade of oil to use ( ISO
* Oiling the chuck but keeping the oil off the gripping surfaces, oiling the power-feed and leadscrew.
* Leaving slides covered by the toolpost to reduce lube loss
||The more people helping with this the better
|-
|Refilling apron oil
||Checking the sight glass for level, where the fill and drain plugs are, using the proper grade of oil (ISO 68) and when to fill it up
||With the one-shot in use this will need to be done often
|}
<div id="level3"></div>
Requires Level 2 induction to be completed first as there's a lot of material to cover on this one so don't want to be going over basics again. People don't have to do the entire level 3 course, and in fact we don't recommend it as covering all of this would take several days and your brain would be about ready to melt by the end of it! Individual topics can be done as needed, the content of this course isn't finalized yet so we're not ready to run it as a full course but if you're specifically interested in one topic then contact a induction provides who offers level 3 to plan out and arrange a short session on that topic.
=== Level 3 ===
* Internal and external thread-cutting with insert tools including multi-start and worm gears
** Theory of thread-cutting
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***** But if you REALLY have to.... using back-out strategies and the foot brake
*** Reading the tables to set gear suitably
*** Setting up the threading dial for metric threads
**** Why it won't work on imperial threads
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* discontinuous turning
* Altering the change-gears and speed limits (540)
*
* Using fixed and travelling steadies for very long workpeices
** Why to use steadies
** How the 2 types grip and stabilise your work
** When to use Fixed Steady
*** Choosing location, have to make a flat to rest on
*** Installing
*** Tightening and lubricating
*** Keeping chips out with shields
** When to use travelling steady
*** Positioning
**** Ahead - Stable but risk of transferring out-of-roundness and wearing brass blocks
**** Co-incident - Strongest but hard to do and risk of chips getting dragged in
**** Trailing - Roundness is stable but risk of longitudinal oscillations forming
** Burning in the brass blocks
*** It's going to happen anyway, might as well make it happen when and where you choose
* Using the dial indicator to maintain position on complex cuts
* Calculating feeds&speeds for other materials not on the standard table
* Cutting standard module worm gears
* Pressure-plate turning of plastics
* Offset work mounting
* Mounting the large toolpost and setting it up
* non-round work
* Cleaning and oiling the lathe including oiling points
* Changing oil for the lathe
* Advanced materials - Titanium/Magnesium alloys/HSS (We don't keep the necessary materials in stock, but if inductee provides it these modules can run)
** Titanium
*** Grades of titanium available, unless otherwise specified Ti6Al4V is the most common
*** Properties of titanium and how they affect turning
**** Poor thermal conductivity - Rapid heat buildup and critical need for coolant
**** Heat goes into material, NOT chips - Even worse heat build up
**** Thermal hardening, if you let heat build it'll harden and become un-turnable
**** High toughness, Steel tooling is possible if razor sharp but carbide is preferred, brazed carbide can be very effective
**** Flammability, swarf is a serious danger
*** High toughness and tendency to hardening means low tool speeds are required, 15m/min is a common choice
*** Excellent set-up rigidity is vital, use centers or steadies wherever possible, be very aware of work and tool stick-out and tool position relative to the slides
*** Normal cutting depths, 0.5mm for roughing, 0.3mm for finishing, DON'T try to take skim cuts if you can help it
**** Spring passes are to be avoided unless vital, and if they are vital be aware you'll only get to make one spring pass before the work is too hardened to turn any further
*** Feed rates, 0.1mm/rev is a good starting point, but experiment and watch your chips closely
**** Chips probably won't break no matter what you do, aim for tight curls, beware of birds-nesting as it's a serious fire risk
*** Avoid discontinuous cuts if you possibly can, they're very damaging to tools
*** Cuts must be decisive, you must not dwell with tool in contact with work, rubbing causes rapid hardening
**** Cuts should be done using power feed whenever possible as it's hard to achieve proper evenness manually
**** Cuts should enter at full speed, no gentle lead-ins
**** Once cut completes then the tool must be backed away from the work immediately, it cannot rest at the end position, not even for a second
*** After every cut, remove the swarf to a safe location where it can't be ignited from the work, and inspect the tool
*** Drilling Titanium
**** Uncoated HSS are often ineffective
**** TiN/TiAN coated drills are OK
**** Cobalt or Carbide drills are best
**** Peck drilling is essential as it's impossible to cool the drill tip effectively
**** Pecks must be small (2.5mm or 0.5 x drill diameter, whichever is less)
**** Drill must be fully withdrawn between pecks to be cooled by the flood coolant
**** Check for work heating every peck
**** Watch your chips carefully and re-sharpen the drill the moment there's any sign of degradation.
*** Parting off is possible with carbide tools, but only if the center is drilled, full-depth parting is difficult
**** If the part-off is deep it may be necessary to change spindle speed during the operation.
** Magnesium
** HSS/Hardened materials
*** Hard-turning can be used to produce hard items at a precise final dimension without having to allow for distortion during heat treating
*** Some reduction of surface hardness will occur, the faster the turning the less pronounced this will be
*** Checking the workpeice hardness using the ultrasonic tester
*** Hard material turning is normally done without coolant
*** Swarf will come off HOT, depending on circumstances maybe up to red-hot
*** Rigidity of set-up it vital, pay special attention to stick-out and tool position relative to the slides
**** Lock any slides you're not using
*** Examine the toolholder carefully when fitting a hard-turning insert, all parts must be in excellent condition or be replaced.
*** Hard turning requires relatively high spindle powers, be sure not to overload and stall the lathe
*** Tool destruction is certain if it's allowed to stop in contact with the work
*** Tool chipping is certain if it's bumped into the work during setup
*** Inspect tool after every pass
*** Moderately hard steels can be turned with higher grade carbides
**** Suitable hardnesses range up to around 45-55HRC
**** Swarf will come off very hot and may spark - take suitable safety precautions!
**** Depths of cut and feed rates should be low, ideally <0.2mm
**** Surface speeds around 30-50 m/min
*** Very hard materials can be turned using CBN inserts
**** CBN Inserts are expensive and delicate, they must be treated with extreme care
**** Maximum hardness ranges up to about 65HRC but values above 55HRC will cause rapid tool wear
**** Swarf will come off '''up to 450C''' - take suitable safety precautions, consider how you're going to stop the machine if burning-hot swarf is spraying over the controls
**** Breaking a chip is unlikely, expect birds-nesting
**** Depths of cut and feed rates should be low, ideally <0.1mm
**** Surface speeds around 50-75 m/min, the harder the material the slower the cut but go as fast as possible for any given job, CNC machines can run faster than this but our set-up won't allow it.
*** Diamond tooling exists for use in hard non-ferrous materials and highly abrasive materials
**** Diamond tooling comes in PolyCrystaline Diamond (PCD) which is very expensive - more so than CBN, and MonoCrystaline Diamond (MCD) which is eye-wateringly expensive.
**** PCD is very, very hard, MCD is the hardest tooling material known to exist.
**** Diamond tooling cannot be used on ferrous metals as the carbon from the diamond will dissolve into the iron
**** Diamond can be used to turn exotic materials such as aluminium superalloys, nickle superalloys, precious metals, tungsten carbide and carbon fiber
**** Maximum work hardness for diamond tools can go as high as 70HRC although wear increases above 60HRC
**** Cutting speeds can range up as high as 1000m/min or as low as 10m/min depending on the hardness of the work
**** Depths of cut and feed rates should be low, ideally <0.1mm, however the very high surface speeds used with PCD tooling will still result in rapid material removal rates
* Workholding using all chuck types and recovering concentricity
* Using reamers
* Turning between centres
** Why you might do it
*** Improved concentrically and repeatability
*** Holding awkward shapes
*** Reusing centers on existing parts or that someone else cut
**** Recutting a center if you need to (toolpost support trick)
** Setting up a center and a catch plate
*** Installing a center in the headstock
*** Installing the catch plate
*** Picking a suitable dog size, setting it up so it won't slap
**** Caution about over or undertightening
*** Alternatively making a center on stock held in a 3/4 jaw chuck
*** Live or Dead center at the tailstock?
*** Might require the use of steadies if the part is long
** Turning between centers
*** The dog and catch plate will cause imbalance so watch speed
*** Parts may be very long so watch out for flex
**** Use support if needed
**** Take shallow cuts
** Tailstock offset turning
*** Regular centers only for the smallest of offsets
**** Part distortion if used too much
*** Using ball-bearing centers for larger offsets
*** Resetting the tailstock alignment when done, high precision required
* Making and shaping brazed carbide cutters
== Maintenance ==
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| Checking oil tanks and draining/refilling || Location of the sight-glasses, fill point and drain points for all 3 oil tanks, which grade of oil goes in which and how much. Main tank takes 1L of ISO68, screwcutting gearbox takes 0.5L of ISO220, Apron takes 0.3L of ISO68. Disposal of used oil ( How do we handle this? )
|-
| Oiling points || Applying oil using the
|-
| Oiling the changegears || Opening the case, oiling them, do not bypass safety to run the gears while oiling
| |||