Friday, 27 October 2017

Lever operated collet chuck for Schaublin B32 collets on the Chipmaster Lathe

Usually when starting with a project I realise what I need in order to complete the project, and often get stuck on some prerequisite to get to the actual project. a tool to make a tool, to make a tool..

This project is no different, I will need an ID and OD grinder, should I want to preserve some of the Schublin collets accuracy. Here I can convert my Eagle Surface Grinder to hold ID and OD spindles perpendicular to the existing spindle axis. Well I need to rebuild it first. Or build a tool post grinder for the Chinese lathe.

Scouring the internet in search of ideas of how to construct such a beast, I came across some similar but different ways to implement the lever closer.

Originally I wanted to base my design on this drawing out of  the book "Taschenbuch für den Maschinenbau" by Dubbel. A plate clutch mechanism similar to the one used in the Matrix clutch on the Chipmaster lathe. 


Below two designs from South Bend Lathe co. The first drawing uses balls for the wedging action. The later heavy 10 model uses a more "common" lever arm action.


http://cdn0.grizzly.com/manuals/g4026_m.pdf
http://sherline.com/Wordpress/wp-content/uploads/2015/09/1150inst.pdf 

Design elements to consider
  • physical dimension (constrained by lathe spindle bore and collets) 
  • materials
  • clamping force
  • balance
  • safety
  • easy to maintain, quick to install, usability, ease of use, attention to detail
The spindle bore on the Chipmaster is 35mm, the minimum OD for the pull bar is specified at 33.5mm, this gives the the draw bar its dimension of OD 34,5 x ID 27.7 
sources on popular forums suggest the pulling distance to be no more than 1/8 inch

The collect requires a clamping force of 11500N. My interpretation of this is 112,8 Kg. How to derive the distance the draw bar needs to be pulled back? The lever pull on the ramp, which engages the lever action to pull the draw bar in. Lever action on lever action with force on incline.
https://www.engineeringtoolbox.com/inclined-planes-forces-d_1305.html

Collet pull force 11500  Newton 1173,469
lever ratio prawl 2,75

cam force 4181,818  Newton  426,7161








Cam Angle 37  deg
C3*SIN(RADIANS(C6))+0,2*C3*COS(RADIANS(C6))  3184,631  Newton

324,9623 Kg
Lever closer ratio 10

Force required 32,49623 Kg




Schaublin Collets B32 72 65

With the Deckel FP2, I got a box of what looked like big Deckel collets, as used on my Cutter Grinder, but the threads where finer.

A bit of googling revealed the Deckel cutter grinder collets are part of the standard  DIN 6341 - 300 Series, more precise 355. So I assumed it might be the same series just bigger, but could not find any match on size and threads. 29.7x1.693mm ; 15TPI ; 45°/5° buttress
(http://www.schaublin.ch/app/webroot/pdf/cat/5.pdf, threads page 57)

So I cleaned one up to measure and found the VS engraving on the face, never seen it before and postponed my investigation. Then an australian youtube contributer posted a video on restoring an old schaublin lathe, which he had found under a tree. Wow and I recognized the logo :) Back to my google search now I knew they where most likely schaublin collets, so I started searching for old catalogues, and eventually found the spec in the modern catalogue. So I decided to make use of these on my Chipmaster, but could not find any collet chuck for these online. So I have to build my own. And so the journey of learning about collet closers and collet chucks started.








Steel Grades Selection and Equivalents


When selecting the material for a project, I find myself spending considerable time to research materials. The local steel supplier makes this easier since he only stocks commonly used materials. But I still like to understand which material is best for which application.

Carbon Steel

    EN3A – 070M20 /C22/ 1018 -  Mild Steel - Red
    EN8 – 080M40/  C45/ 1038 - Medium Carbon - Yellow
    EN9 – 070M55 / C55 /1060 - High Carbon - Green

Alloy Steel

    EN19 – 709M40/ 42CrMo4/4240 - Black
    EN24 – 817M40/ 40CrMo8/ 4340 -
    EN26 – 826M40/ 40NiMoCr10-5/ 1.6745 -
    EN30B – 835M30/ 36NiCrMo16/ 1.6773 -
    EN36B – 655M13/ 15NiCr13/ 3316/ 1.5752 -

Specification: EN8 – 080M40

Colour Code: Yellow
Availability:
  • Bright Cold Drawn Round Bar: 6mm diameter to 75mm diameter
  • Bright Peeled Round Bar: 16mm diameter to 160mm diameter
  • Bright Cold Drawn Hexagon Bar: 8mm A/F to 55mm A/F
  • Black Round Bar: 16mm diameter  to 400mm diameter (as rolled and as forged)
  • Black Square Bar: 25mm A/F to 105mm A/F 
Characteristics:
  • Commonly known in South Africa as “Axle Steel” or “40 Ton Steel”
  • Known as “40 Carbon” in steelmakers parlance
  • Good enough welding properties as the carbon content is relatively low. When welding, pre heating the steel to approximately 100⁰Celcius is recommended as well as the use of low hydrogen electrodes. Tig or Mig welding is recommended
  • Machinability is good but allow 6% on outside diameter for removal of surface defects
  • EN8 is preferred to EN3A to machine as the material “chips” and makes machining easier and a better machined finish can be achieved
  • Not recommended for high tensile applications for example. 50-60 ton tensile
  • Heat treatment only to limited ruling sections (see schedule below)
Applications:
  • All uses where a higher tensile in Carbon Steel is required including the more popular uses for spindles, shafts, axles, cylinders, bolts and nuts
  • Armature, dynamo and motor shafts
  • Heat treated bolts
  • Connecting  rods
  • Driving rings
  • Flanges
  • Railway Couplings
  • Brackets, bushes and studs
  • Pulleys (both light and heavy duty)
  • Housing and parts not subject to high stresses or severe wear
  • Uses where the tensile rating of 510MPa minimum is a requirement
  • Bolt Specification: 8.8 (in condition “Q”)
  • Bolt Specification: 9.8 (in condition “Q”)
  • Bolt Specification: 10.9 (in condition “R”)
Comparable Specifications:
  • Din C45
  • SAE 1038/44
  • Deutsche W/No 1.1186/1.0511
  • Euro Norm EN10083-1 (1991) 970 Part1; C40E
  • BS970 Part 1 1983, 080M40
  • BS970 of 1955 EN8
  • American AISI 1042
Chemical Composition (%):
Carbon (C) 0.36 (Min) – 0.44 (Max)
Silicon (Si) 0.10 (Min) – 0.40 (Max)
Manganese (Mn) 0.60 (Min) – 1.00 Max)
Sulphur (S) Nil (Min) – 0.050 (Max)
Phosphorus (P) Nil (Min) – 0.050 Max)
 
Mechanical Properties:

Normalised
Condition “Q”
Condition “R”
Ruling Section
254mm
65mm
20mm
Tensile Strength
510/540 MPa
620/770 MPa
690/850 MPa
Yield Stress (Min)
245 MPa
385 MPa
465 MPa
Elongation
17%
16%
16%
ISO V Impact
20 Joule
33 Joule
33 Joule
Hardness
152/207 Brinell
179/229 Brinell
201/255 Brinell

Heat Treatment:
  • Normalise at a temperature of 830⁰/860⁰Celsius
  • Harden in oil from a temperature between 830⁰/860⁰ Celsius
  • Temper at a suitable temperature, 550⁰Celsius for condition “R” and 660 – Celsius for condition “Q”

Specification: EN9 – 070M55

Colour Code: Green
Availability:
  • Black Round Bar: 20mm diameter to 400mm diameter
Characteristics:
  • This material is the highest carbon steel available from special steel merchants in South Africa for general use
  • Heat treatment only to limited ruling sections
  • It lends itself to induction hardening and shorterising (flame hardening)
  • Care should be taken that hardened  components are properly tempered after quenching in water as the material can become “glass hard” and brittle
  • Should small components require a “glass hard” surface, temper by boiling in brine for 30 minutes minimum. Brine of 9% salt in water is required
  • Machinability is good  but allow 6% on outside diameter  for removal of surface defects
  • Material can be welded on but is not recommended
  • Ideal for 45 ton tensile applications
  • Not recommended for carburising
Typical Applications:
  • This steel is also used to make machine collets. After quenching, ensure that the components are tempered three times (spring tempering)
  • All applications where wear resistance is required
  • Can be used in the “as forged” condition for bending brake tools
  • Commonly used for press eccentric shafts and bending brake tools
  • Also used for shafts, spindles and general machine components including sprockets, cylinders, cams, crankshafts, small gears, machine tools, keys, grinding balls for ball mills, pulleys, ball race rings, bolts and nuts
  • No bolt specifications are applied to this specification
Comparable Specifications:
  • Din C55
  • SAE 1060
  • Deutsche W/No  1.0535
  • Euro Norm EN 10083-1 (1991) 970 Part 1; C55E.
  • BS970 Part 1 1983, 070M55
  • BS970 of 1955 EN9
Chemical Composition (%):
Carbon (C) 0.50 (Min)- 0.60 (Max)
Silicon (Si)                         0.10 (Min) – 0.40 (Max)
Manganese (Mn) 0.50 (Min) – 0.90 (Max)
Sulphur (S)                      Nil (Min) – 0.05 (Max)
Phosphorus (P)              Nil (Min) – 0.05 (Max)
Mechanical Properties:

Normalised Condition “R” Condition “S” Condition “T”
Ruling Section
254mm
100mm
65mm
20mm
Tensile Strength
600/700 MPa
690/850 MPa
770/930 MPa
850/1000 MPa
Yield Stress (Min)
310 MPa
415 MPa
480 MPa
570 MPa
Elongation
13%
14%
14%
12%
ISO V Impact
Void
Void
Void
Void
Hardness
201/255 Brinell
201/255 Brinell
223/277 Brinell
248/302 Brinell
Heat Treatment:
  • Normalise at a temperature of  810C/840CCelsius
  • Harden in oil from a temperature between  810C/840CCelsius
  • Temper at a suitable temperature, 550CCelsius for condition “T”, 610CCelsius for condition “S” and 660C Celsius for condition “R” 

Specification: EN19 – 709M40

Colour Code: Black
Availability:
  • Black Round Bar in “as rolled “ and hardened and tempered to condition “T”
  • Black rolled and forged surface: 16mm diameter to 350mm diameter
  • Bright Peeled Round Bar, “as rolled” and condition “T”: 16mm diameter to 160mm diameter
Characteristics:
  • This material distorts when machining shafts or long spindles, especially once hardened and tempered
  • In practice, the work pieces should be rough machined to plus tolerance and left in the open on the floor for 36 hours after which the material would have “aged” and stress relieved itself and thereby minimising distortion on the finishing of the product
  • Machinability is good but allow 6% on outside diameter for removal of surface defects
  • This material can be welded but welding should only be attempted by using the appropriate methods and materials as advised by welding expertise
  • Ideal for 60 ton tensile applications up to 100mm max
  • Sizes above limited ruling section will be heat treated to hardness only, with no guarantee on mechanical properties
Applications:
  • Utilised when higher than carbon steel mechanical properties are required
  • Commonly used for axles, drive shafts, crankshaft connecting rods, high tensile bolts, studs, propeller shaft joints, rifle barrels, and induction hardened pins
  • Bolt specification: 9.8 (in condition “T”)
  • Bolt specification: 10.9 (in condition “U”)
Comparable Specifications:
  • Din 42CrMo4
  • SAE 4240
  • Deutsche W/No  1.7225
  • Euro Norm EN 10083-1 (1991) 970 Part 1; 42CrMo4
  • BS970 Part 1 1983, 709M40
  • BS970 of 1955 EN19
Chemical Composition (%):
Carbon (C) 0.36 (Min) – 0.44 (Max)
Silicon (Si) 0.10 (Min)- 0.40 (Max)
Manganese (Mn) 0.70 (Min) -  1.00 (Max)
Chromium (Cr) 0.90 (Min) – 1.20 (Max)
Sulphur (S) nil (Min) – 0.04 (Max)
Phosphorus (P) nil (Min)- 0.035 (Max)
Molybdenum (Mo) 0.25 (Min) – 0.35 (Max)
Working and Heat Treatment:
  • Forging: Forge within the temperature range of 1250C/900C Celsius
  • Anneal: Anneal at a temperature of 850C Celsius and cool steadily
  • Normalising: not applicable
  • Hardening: oil quench from a temperature of  850C/880C Celsius
Mechanical Properties:

Annealed
R
S
T
U
V
W
Y
Ruling Section (mm)
150
150
100
65
65
30
30
25
Tensile Strength (MPa)
680/720
690/850
770/930
850/1000
930/1080
1000/1160
1080/1240
1280
Yield Stress (MPa)
440/480
480
570
665
740
835
895
1050
Elongation (% Min)
22
15
15
13
12
12
10
10
ISO V Impact (Joule)
30
30
30
30
25
25
22
7
Hardness (Brinell)
190/210
201/255
223/277
248/302
269/321
293/341
311/375
363/415









Proof Stress (0.2%) if required (MPa, Min)
495
550
630
710
770
850
985



Specification: EN24 – 817M40

Colour Code: Blue and Black
Availability:
  • Black Round Bar in “as rolled” or hardened and tempered to condition “T”
  • Black Round Bar: 20mm diameter to 350mm diameter (as rolled / as forged)
Characteristics:
  • This is more versatile specification than 709M40 as the limiting ruling sections for heat treatment are amplified because of the addition of Nickel
  • Welding should only be attempted by using the appropriate methods and materials as advised by welding expertise
  • Machinability is good and has little distortion in machining
  •  Allow 6% on the outside diameter for removal of surface defects during machining
  • Ideal for 60 ton tensile applications up to 250mm diameter max
  • This material is often used in the annealed, as rolled or as forged condition for machining.  Subsequent heat treatment is used to achieve a higher tensile i.e. condition “T”, “U”,” V”,     ”W”, “X”, “Y” and “Z”
  • This material can be certified as a safety specification in lifting equipment when such equipment is subject to impacts and requires a high tensile property, such as shaft sinking equipment in the mining industry
Applications:
  • This material is used where high tensile strengths and good impact values are required
  • Some of the more popular uses include differential shafts, pinion sleeves, eccentric crusher shafts, eccentric high pressure shafts, high duty connection rods, power transmission slide gears and slide cams, mandrels for tube mills, heavy axles and high tensile gears, bolts and nuts
  • Bolt Specification: 10.9 (in condition “U”)
  • Bolt Specification: 12.9 (in condition “V”)
Comparable Specifications:
  • Din 40CrM0 8 – 4
  • SAE 4340
  • Deutsche W/No 1.6562
  • Euro Norm EN10083-1 (1991) 970 Part 1; 34CrN1Mo6
  • BS970 Part 1 1983, 817M40
  • BS970 of 1955 EN24
  • American AISI 4340
Chemical Composition (%):
Carbon (C) 0.36 (Min) – 0.44 (Max)                                 
Silicon (Si) 0.10 (Min) – 0.35 (Max)
Manganese (Mn) 0.45 (Min) – 0.70 (Max)
Sulphur (S) Nil (Min) – 0.04 (Max)
Phosphorus (P) Nil (Min) – 0.040(Max)
Nickel (Ni) 1.30 (Min) – 1.70 (Max)
Chromium (Cr) 1.00 (Min) – 1.40 (Max)
Molybdenum (Mo) 0.20 (Min) – 0.35 (Max)
Working and Heat Treatment:
  • Forging within the temperature range 1100⁰/850⁰ Celsius
  • Anneal at a temperature of 760⁰ Celsius, soaking for four hours after reaching temperature
  • Normalising is not applicable
  • Hardening by oil quench at a temperature of 820⁰/850 Celsius after soaking through
Mechanical Properties:

Annealed
S
T
U
V
W
X
Y
Z
Ruling Section (mm)
250
250
250
100
65
30
30
30
30
Tensile Strength (MPa)
620
680/770
850/1000
930/1080
1000/1160
1080/1240
1235 (Min)
1540 (Min)
1540 (Min)
Yield Stress (MPa)
410
480
635
740
835
925
1005
1130
1130
Elongation (% Min)
16
16
12
12
12
11
10
5
5
ISO V Impact (Joule)
30
32
40.7
47.5
47.5
40.7
34
30
10
Hardness (Brinell)
180/220
223/277
248/302
269/321
293/341
311/375
341/388
363/415
444 (Min)
Proof Stress (0.2%) if required (MPa, Min)
550
630
710
770
850
910
990
1235

Note: Interestingly, the impact values do not alter between condition “U” and condition “V”.














Specification: EN26 – 826M40

Colour Code:  Black/Orange
Availability:
  • Availability is extremely limited in the South African market
  • Prospective users of this specification are advised to check availability before any commitments
Characteristics:
  • A 6% allowance should always be made for removal of surface defects during machining
  • Welding is not recommended on this specification
  • Machinability good
  • Ideal for heat treated condition (U/60/70 ton tensile) or V (65/75 ton tensile)
  • As with EN24, this material is ordered in the annealed, as rolled or as forged condition for machining.  Subsequent heat treatment is used to achieve higher tensile strength                                        i.e. Condition T, U, V, W, X, Y and Z
  • Some applications require this material to be heat treated to BS2772 Part 2 Grade 826M31 to qualify as a safety standard
Applications:
  • Similar applications and uses as EN24 817M40 but for higher tensile requirements
  • This specification is prescribed by the mining industry in South Africa for lifting equipment e.g. stress parts in winches and cranes and general lifting tackle such as eyebolts, shackles and hooks. However, the material has to be manufactured to 826M31 procedures to qualify as a safety standard
  • When this material is specified for safety reasons it is used in spline shafts, gear shafts, winder equipment parts, heavy duty mining head gears and in other safety critical mining applications
  • It is further used as high impact eccentric shafts, crusher shafts, turnbuckles, brake pins, tie rods and main line railway armature shafts
Comparable Specifications:
  • Din 40NiMoCr 10-5
  • Deutsche W/No 1.6745
  • BS970 Part 1 1983, 826M40
  • BS970 of 1955 EN26
Chemical Composition (%):
Carbon (C) 0.36 (Min)- 0.44 (Max)                                  
Silicon (Si)                               0.10 (Min) – 0.35 (Max)
Manganese (Mn) 0.45 (Min) – 0.70 (Max)
Sulphur (S) Nil (Min) – 0.040 (Max)
Phosphorus (P)                     Nil (Min) – 0.040 (Max)
Nickel (Ni)                              2.30 (Min) – 2.80 (Max)
Chromium (Cr)                      0.50 (Min) – 0.80 (Max)
Molybdenum (Mo) 0.45 (Min) – 0.65 (Max)
Working and Heat Treatment:
  • Forging is done within the temperature range 1100⁰ / 850⁰ Celsius
  • Annealing at a temperature of 670⁰ Celsius, soaking for 4 hours after reaching temperature
  • Normalising, not applicable
  • Hardening, oil quench at a temperature of 820⁰/850⁰ Celsius, after soaking through
Mechanical Properties:

U
V
W
X
Y
Z
Ruling Section (mm)
150
150
150
100
100
100
Tensile Strength (MPa)
930/1080
1000/1160
1080/1240
1235 (Min)
1540 (Min)
1540 (Min)
Yield Stress (MPa)
740
835
925
1005
1130
1130
Elongation (% Min)
17
14
13
14
14
10
ISO V Impact (Joule)
47.5
47.5
40.7
34
34
14
Hardness (Brinell)
269/321
293/341
311/375
341/388
363/415
444 (Min)
Proof Stress (0.2%) if required (Mpa, Min)
710
770
850
910
990
1235







Specification: EN30B – 835M30 (Annealed)

Colour Code: Orange
Availability:
  • Black Round Bars supplied only in the annealed condition
  • Availability is extremely restricted and prospective users of this specification are advised to check availability before committing to using it
Characteristics:
  • This is a very expensive steel specification not just because of the high alloying elements but also the refining methods utilised to keep the hydrogen (H) content of the steel to less than two parts per million, (H = ≤ 2PPM). It is more costly than other B.S. 970 specifications
  • This is 1500 MPa minimum tensile steel , air hardening in sections up to 65mm diameter
  • Specially recommended for intricately shaped parts where an air hardening steel is preferred
  • This material can be case hardened , can be carburised and induction hardened or shorterised (flame hardened)
Applications:
  • 835M30 is a versatile specification.
  • The applications of this material are numerous and includes the following
  • In Engineering: ultra high tensile applications, shafts, gears, bolts, spline shafts, crusher shafts, eccentric shafts, hard wearing bushes and high impact pistons
  • In mining: rock drill, knock off bits, mill hammers, cyclone plates, high tensile mechanical and thermal shock applications
  • In Tooling: plastic extrusion dies, die bolster rings and punches
Comparable Specifications:
  • Din 36NiCrMo16
  • Deutsche W/No 1.6773
  • Euro Norm EN 10220-3 (1999)
  • 36NiCrMo16
Chemical Composition (%):
Carbon (C) 0.26% (Min) 0.34% (Max)
Silicon (Si) 0.10% (Min) 0.35% (Max)
Manganese (Mn) 0.40% (Min) 0.60% (Max)
Sulphur (S) Nil 0.25% (Max)
Phosphorus (P) Nil 0.25% (Max)
Nickel (Ni) 3.90% (Min) 4.30% (Max)
Chronium (Cr) 1.10% (Min) 1.40% (Max)
Molybdenum (Mo) 0.20% (Min) 0.40% (Max)
Mechanical Properties:
Tensile Strength 1500 MPa (Min)
Yield Stress 1300 MPa (Min)
Elongation 10% (Min)
ISO V Impact 20 Joule (Min)
Hardness 444 Brinell (Min)
Working and Heat Treatment:
  • Forging: Do not charge into a hot or preheated furnace. Heat from cold to forging temperature 950⁰/1000⁰Celsius. Do not exceed 1100⁰ Celsius. Forge carefully and do not work on the steel  below 850⁰/900⁰ Celsius as the material is then hardening and this condition excessive stresses will build up in the workpiece. Cool the forging slowly and out of draughts or bury in lime or ashes.
  • Annealing: Heat carefully to 810⁰ Celsius and allow to cool in the furnace or still air. Re-heat the steel slowly in the furnace to 630⁰/640⁰ Celsius and soak for about four hours after wich it may be cooled in still air (sub critically annealed). All parts for machining should be annealed.
  • Normalising: Not applicable
  • Hardening:  To harden in air or oil, heat the parts gradually and uniformly to a temperature of 810⁰/830⁰ Celsius. When air hardening, place the parts out of draughts to avoid unequal hardening and consequent stresses. For up to 65mm diameter the properties are obtainable through air hardening. For larger sections, oil hardening should be performed.
  • Tempering: Where extreme toughness is desired, the pieces, whether air or oil hardened should be subsequently tempered at a maximum temperature of 250⁰ Celsius allowing time for tempering through. Test results obtained on a 30mm diameter test piece after hardening at 820⁰ Celsius and tempering at 250⁰ Celsius

     

Specification: EN36B – 655M13

Colour Code:  White
Availability:
  • Black Round Bars: 20mm diameter to 350mm diameter (as rolled and as forged)
Characteristics:
  • This material is also known as 3% Nickel-Chromium Case-Hardening Steel
  • This specification is good for welding, prior to Carburising and Case Hardening
  • Machinability is good but allow 6% on the outside diameter  for removal of surface defects
  • Required hardness can be achieved by case hardening the outer surface by means of one of the following, Carburising, Carbonitriding, Nitriding, Nitrocarbursing, Tufftriding
Applications:
  • This material is often used in the manufacturing of gears, worm shafts, pinion shafts and spline shafts
  • This specification is largely utilised when wear resistant hard surface is required along with high core strength
  • Other common uses include Auto and heavy vehicle transmission components, engineering machinery gear box parts, aircraft gears mining steering worms, chuck jaws, track pins, gudgeon pins,mining gearbox gears, pinions and cogs
Comparable Specifications:
  • Din 15NiCr13
  • SAE 3316
  • Deutsche W NO 1.5752
  • Euro Norm EN 10084 (1998) 15NiCr13
  • BS970 Part 1 1983, 655M13
  • BS970 of 1955 EN36B
Chemical Composition  (%):

% Min
% Max
Carbon (C)
0.10
0.16
Silicon (Si)
0.10
0.035
Manganese (Mn)
0.35
0.60
Phosphorus (P)
Nil
0.04
Sulphur (S)
Nil
0.04
Chromium (Cr)
0.70
1.00
Nickel (Ni)
3.0
3.75
Mechanical Properties:
  • Mechanical Properties of the core of a case hardened test bar of 28mm diameter
  • Hardness of the test bar surface, Rc65
Tensile Strength (Min)
1000 MPa
Elongation (Min)
9%
ISO V Impact
40 Joule
Working and Heat Treatment:
  • Carburise at a temperature of 900⁰/930⁰ Celsius
  • Refine at a temperature of 860⁰/880⁰ Celsius (see Note)
  • Harden at a temperature of 760⁰/780⁰ Celsius in oil
Note:  A “Single Quench” treatment may suffice to obtain the specified results. Intricate parts, or  parts of large sectional differences may distort in the refining treatment, thus the tendency to avoid refining after carburising. However, should the hardness not be uniform, cryogenic (sub zero) treatment is recommended.
Through the analysis (chemical composition), the refining treatment after carburising may be omitted  an a “Single Quench” treatment may be employed
     

Chipmaster Gear Cutting

  Calculate all the possible gear combinations for the gear selector to cut a 15TPI thread: Imperial TPI C 5 24 20 Imperial TPI ...