Thread Turning: Laydown Threading
For External and Internal Threading on the Lathe our favorite option is Laydown Threading. Laydown Threading has a optimal engagement angle to make it free cutting as well as Partial Profile and Full Profile Inserts to allow you to cut a range of External & Internal Threads with Inserts that top the thread or can do a range of TPIs. Here is the best way to select Laydown Threading Tools:
#1 Select Insert Size:
The Insert Size you select is based on the TPIs of thread you will be cutting as well as the Minimum Bore you are going into if it is Internal Thread. Here is a Breakdown:
Size 16 (or Size 3, 3/8" IC): 8-72 UN Range & 0.25-3.5 ISO Range
The Size 16 is the most common Letdown Threading Insert we see. The Partial Profile AG60 Insert can give you a range of 8-48 UN (0.5-3.0 ISO) and there are Full Profile Inserts that will top your Thread available in UN, ISO, NPT, Whitworth, BSPT, ACME, STUB ACME, BUTTRESS, TRAPEX and Round Profiles. The External Holders are available in 1/2", 5/8", 3/4", 1" and 1.250" Shank. While the Internal Bars start at a .640" Bore
Size 11 (or Size 2, 1/4" IC): 11-80 UN Range & .25-2.5 ISO Range
The Size 11 is more common in Swiss Machines as well as Internal Threading applications as the Size 11 Insert Boring Bars can get down to a .470" Min Bore. The Partial Profile A60 Insert goes from 16-48UN and there are also Full Profile Inserts in all the same threads as the Size 16 Above. The External Holders are available in 5/16", 3/8", 1/2" and are available in the longer shank for the Swiss. While the Internal Bars start at .470" Min Bore
Size 06, 08 and 8U Inserts: 11-32 UN Range &0.25-2.0 ISO Range (Internal Only)
The Size 06 get down to a .240" Min Bore, while the Size 08 get down to a .310" Min Bore and the Size 8U get to a .350" Min Bore. These inserts are small so we only recommend them in applications where the thread is shallow or if it is a fine thread. Otherwise Tapping or using a Single Point Carbide Bar is the best option.
Size 22 Inserts: 5-7UN Range & 5.5-6.0 ISO Range
The Size 22 is only used in Coarser Threads like those listed above or in ACME Thread (4, 5 & 6 TPI for ACME and STUB ACME) or 6 & 8 TPI American Buttress Threads. The larger insert is needed for the depth. These are available in 1", 1.250" & 1.500" Square Shank Holders as well as boring bars at .900" Min Bore and up
Size 22U Inserts: 4-4.5UN Range & 5.5-6.0 ISO Range
The Size 22U is only used in Coarser Threads like those listed above or in ACME Thread (4 TPI for ACME and 3-4 TPI STUB ACME) or 4 TPI American Buttress Thread. The larger insert is needed for the depth. These are available in 1", 1.250" & 1.500" Square Shank Holders as well as boring bars at 1.500" Min Bore and up
Size 27 Inserts: 4-4.5UN Range & 5.5-6.0 ISO Range
The Size 27 is identical in range to 22U, it is only used in Coarser Threads like those listed above or in ACME Thread (4 TPI for ACME and 3-4 TPI STUB ACME) or a 5 TPI American Buttress Thread. The larger insert is needed for the depth. These are available in 1", 1.250" & 1.500" Square Shank Holders as well as boring bars at 1.560" Min Bore and up
Size 27U Inserts: 3UN Range & 8..0 ISO Range
The Size 27U is for even Coarser Threads like those listed above or in ACME Thread (3 TPI for ACME and STUB ACME) or a 3 TPI American Buttress Thread. The larger insert is needed for the depth. These are available in 1", 1.250" & 1.500" Square Shank Holders as well as boring bars at 1.560" Min Bore and up
Size 33U Inserts: 2UN Range & 12.0 ISO Range
The 33U is for the Coarsest Threads like those listed above or in ACME Thread (2 TPI for ACME and STUB ACME). The larger insert is needed for the depth. These are available in 1", 1.250" & 1.500" Square Shank Holders as well as boring bars at 2.500" Min Bore and up
#2: Select External or Internal and Right Hand or Left Hand
Select if the thread is for a External (E) or Internal (I) Application and where you want a Right Hand (R) or Left Hand (L) Thread. External Right Hand is ER and Internal Right Hand is IR. External Left Hand is EL and Internal Left Hand is IL.
#3: Select Pitch
You can select a Partial Profile Insert or a Full Profile Insert:
A Partial Profile Insert will have the 60° Angle on the Insert to be able to cut a Range of Threads in UN and ISO, it just does not have the Radius at the bottom to top the thread (you will need to clean up the top of the thread with a OD Turning Insert and ID Boring Bar). Partial Profile Inserts are great for job shops that need to cut a range of threads. The most common is the Size 16 AG60 Insert that can cut from 8-48 UN and 0.5-3.0 ISO.
A Full Profile Insert will only cut the Thread Size Listed as it will have the Radius to top the thread. This will leave you a cleaner thread and will also be faster as you do not need to come back in with a separate tool to top the thread. Full Profile Inserts are the way to go for production jobs and threads that need a clean finish. These are available in UN, ISO, NPT, Whitworth, BSPT, ACME, STUB ACME, BUTTRESS, TRAPEX and Round Profiles
#4 Select Grade:
Here are the options:
MXC: TIN Coated for Steel, Cast Iron and Aluminum/Plastics
BMA: ALTIN Coated for Steel and Stainless
BLU: High Performance ALTIN Coated for Stainless Steels, Titanium & Exotic Alloys
HBA: Hard PVD Coating for Hardened Steels (up to 62 HRc)
If you have any questions or would like help in selecting the correct tools let us know!
