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Tools/metallathe/induction: Difference between revisions
→Level 2 Induction
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Accurate surfacing
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| Selecting Feeds and Depth-of-Cut
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* Chip loading and how it affects chip form
'''These tables are under development and will be expanded in time, till then, use your best judgement'''
▲Selecting Feeds and Depth-of-Cut Chip loading and how it affects chip form, Normal depths of cut for HSS/Carbide tooling and typical feed rates that should be used. The values listed here are deliberately conservative and faster material removal rates may well be possible depending on circumstances, as always, listen to the lathe, watch the chips and adjust speeds and feed accordingly.
For the carbide insert tooling▼
▲For the carbide insert tooling
Material Depth of Cut Feed (mm/rev) Notes▼
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Aluminium (finishing) 0.1mm - 0.5mm 0.05mm - 0.10mm Glassy finish▼
Mild Steel (roughing) 0.4mm - 1.0mm 0.05mm - 0.20mm Can be a bit rough surface▼
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Mild Steel (finishing) 0.1mm - 0.3mm 0.03mm - 0.06mm Use facing tool for best result▼
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Stainless Steel (304) (finishing) 0.07mm - 0.12mm 0.05mm - 0.10mm Can give almost mirror finish▼
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| Stainless Steel (304) (roughing) || 0.3mm - 0.5mm || 0.10mm - 0.20mm || Produces long ribbon swarf
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▲| Stainless Steel (304) (finishing)
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Cutting efficiently without breaking tools!
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|Using the power feeds
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* How to read the tables on the lathe to work out proper feed rates using the left columns of the bottom table.
* Changing the gears to select the chosen feed rate should be done while the lathe is not running, if you can't get a gear, go back to a gear you could get, then run the lathe for a few seconds and try again. Changing gear while running is allowed only at speeds 540rpm and below
* Verify that the direction of cut lever on the headstock is correctly set.
* Check which slide is being fed, remembering that the feed rate is halved on the cross-slide.
* Checking the powerfeed rod is clear of obstructions, checking you can move the tool through the entire intended range of motion without hitting anything.
* Position the tool well clear of the work and do a test move on the powerfeed to verify that it's moving in the direction and at the speed expected.
* Position the tool at the start of the cut, and touch on using the cross-slide zeroing the dial.
* Pulling out the main feed wheel to disengage it if desired, and then beginning the cut using the powerfeed
* Disengaging and finishing the cut using the cross-slide and then re-positioning back to zero for the next cut.
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Using the powerfeeds for larger cuts is almost essential but proper settings must be chosen to avoid breaking tools
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|Taper Turning on top-slide
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* Setting the angles on the slide and locking it down, setting the tool angle to be compatible with that cut direction.
* Using the cross-slide to advance the taper and how to calculate distances when the move isn't perpendicular to the cut.
* How tool speeds vary across the travel of a taper, similarly to facing off and hence requiring variation in feed rate.
* Watching out for clearances and how to deal with if the tool winds up in a position where the cross-slide fails to engage over full range, difficulties using live/dead centers with taper turning.
* The travel limits on the top-slide, and the possibility of using tail-offset turning for those who want level-3 induction. Using back-side cutting to deal with awkward angles
* Putting the top-slide back parallel when you're done with the Lathe.
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Putting tapers on work
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|Boring
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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.
* 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.
* Using the dials to set the depth and calculating depth using cross-slide for tapered holes.
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The need to produce holes of odd or very large sizes
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|Breaking corners
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* Why it's needed - avoiding cuts from sharp work, taking off burred over corners.
* Using the top-slide to cut tapers
* Cutting using the side of tools and especially the grooving/beveling carbide insert too while watching the angles that are produced by the 55deg carbide.
* Note when using the carbides on a parallel motion that the depth of cut increases very rapidly with sideways motion so considerable caution is needed if beveling deeply
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Important safety and aesthetic technique
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Parting off Using both the carbide insert and the regular blade if we can get a suitable one. The need to ensure very accurate perpendicular tool positioning and precise movement. Parting should be done at 25-50% spindle speed compared to other cuts and with the use of copious cutting lubricant and frequently reapplied. Making sure that minimal tool is exposed on the blade holder, on the carbide holder cover maximum parting depth. Breaking corners during parting and jogging the breaking cutter using top-slide and it's dials to reset position. Methods of catching the parted object, using a magnet, using a drill or rod, using fingers if no other option and watching for heat build-up in that case! Caution for tool chatter. If the parting is done well then re-facing the back of the part may not be needed Parting neatly is needed for work at this level
Turning using indicator dials Touching on and zeroing the indicators, using them to position the tool even when you can't see it, for example when using a boring bar or with heavy coolant. How the main slide looses the zero point on the top-slide whenever use and how to approximately regain it by re-touching on. How the angle of the top-slide changes the X/Y position effects of that dial, the trigonometry to deal with that. Basic use of the dials will have been covered in induction but a deeper understanding will be needed here for boring and once the flood cooling system is installed.
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