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SB 9C 116T Gear in place of 80T
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Dan P
I recently acquired a 1947 9C and found that there is a 116T screw gear that was used in conjunction with a 108/18 gear for fine feeds.
This is not listed on the thread/feed chart of the machine. Calculating the feed rate when using the 116T, 108/18 and a 16T stud gear comes out to 0.0029"/rev if I did this correctly. This is higher than using the 16T stud, 54/18, 72/18, and 80T screw gear which comes out to .0021"/rev but still close. My question is can you use the 116T screw gear along with the 16T stud, 54/18, and 72/18 to produce a finer feed of .0014"/rev. Will this combination fit using the standard 2 fork banjo. I would like to know if this combination is possible before I try to purchase the 116T gear as I am not sure if there is sufficient room for this combination.
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George Meinschein
Dan, I don’t have my calculator within arm’s reach right this second, but how about calculating the OD of the 116T gear and/or the center-to-center distances of your proposed geartrain and then seeing if it looks possible with your 2 fork banjo. Let me know if you need help with calculations or layout and I’ll run the numbers for you. Thanks, George Meinschein Firearm and Ballistics Engineering LLC 150 Brittany DriveFreehold, NJ 07728 gmeinschein@... Cell#: 732-580-1736 Sent from Proton Mail for iOS
On Sun, Jul 24, 2022 at 7:13 PM, Dan P via groups.io <danjp_2000@...> wrote:
I recently acquired a 1947 9C and found that there is a 116T screw gear that was used in conjunction with a 108/18 gear for fine feeds. -- -George M.
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Dan P
I just wanted to let the group know my results from trying to use the 116T gear on my 9C.
To use it, you will need a 2 fork banjo along with the 116T, 54/18, and 108/18. The 72/18, 54/18, and 116 screw gear combination will not mate up. The 116T screw gear is too large for use with the 72/18 idler as it will not engage. In addition, the 116 screw gear, 72/18 and 108/18 combination will not mate up. But the 116, 54/18, and 108/18 will fit and it produces a feed of 0.00096"/rev. This combination produces an almost polished cut. The arraignment is that the 54/18 idler is on the top fork and engages with the 16T stud gear. The 108/18 idler is mounted on the lower banjo arm and engages with the 54/18 and the 116 screw gear. Lastly the 116T is mounted in the screw gear position and drives the lead screw. So I thought I would share my results so anyone who needs to produce a very slow, fine feed knows that this combination works extremely well for producing an almost polished cut.
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Ray De Jong
Thanks Dan, I can try that
On Monday, October 17, 2022, 12:10:02 PM PDT, Dan P via groups.io <danjp_2000@...> wrote:
I just wanted to let the group know my results from trying to use the 116T gear on my 9C. To use it, you will need a 2 fork banjo along with the 116T, 54/18, and 108/18. The 72/18, 54/18, and 116 screw gear combination will not mate up. The 116T screw gear is too large for use with the 72/18 idler as it will not engage. In addition, the 116 screw gear, 72/18 and 108/18 combination will not mate up. But the 116, 54/18, and 108/18 will fit and it produces a feed of 0.00096"/rev. This combination produces an almost polished cut. The arraignment is that the 54/18 idler is on the top fork and engages with the 16T stud gear. The 108/18 idler is mounted on the lower banjo arm and engages with the 54/18 and the 116 screw gear. Lastly the 116T is mounted in the screw gear position and drives the lead screw. So I thought I would share my results so anyone who needs to produce a very slow, fine feed knows that this combination works extremely well for producing an almost polished cut.
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 these 2 gears came with my 1936 Southbend 9C it has a single slot banjo, when I coupled them up with the 2 slot banjo and the other compound train 54/18 , the saddle was super slow, but the finish was like the piece had been ground.
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