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Missing Gear Tooth
- Thread starter milomilo
- Start date
- Joined
- Jul 12, 2016
- Messages
- 59
I pressed out the small gear today. It was locked in with two setscrews drilled and tapped at the junction of the small gear hub and the large gear bored hole. My new small gear should be here in about a week. It will have to be bored, faced and cut in a shoulder to press into the large gear bore. I have some bronze bushings in my shop that may work for the new bushing. I'll have to look in the next couple days.
- Joined
- Jul 12, 2016
- Messages
- 59
Got the bushing out of the small rear this morning. Had to machine a punch. Came out with no damage. It is copper not bronze. I have the new bronze bushing, except it has to be turned down a little. The old copper bushing had no damage but I expect it has some wear, so think I will go with the new bushing. The old gear measured 1.23, the new gear is stated at 1.13. I did not pick up on that until today. Guess I will wait and see when it gets here if it will work or not.
- Joined
- Jul 12, 2016
- Messages
- 59
Thanks for the offer, but I found one very close to the size I needed.
- Joined
- Jul 12, 2016
- Messages
- 59
Thanks. I am enjoying it here.
- Joined
- Jul 12, 2016
- Messages
- 59
Looks like I am back to square one. The gear I ordered has a teeth gear diameter of 1.125. My old gear is 1.23. way too small to work. I down loaded the PDF file from Boston gear and I do not find the gear I need. Again I am looking for the small gear shown in the pics above with a gear diameter of 1.23, 16 teeth, hub width 1/2" and 1/2" face width. This is the first time I have searched for gears for the lathe so it is very likely I am totally screwed up with the wrong numbers. I was looking for 14.5 DP gears but not totally sure that is correct either. Pic attached of the two gears. Old one on bottom and new one on top.
- Joined
- Jan 29, 2014
- Messages
- 156
I don't think you are likely to find a 14.5 DP.
A 16 tooth gear 1.125" in diameter is a 16DP. (You need to be careful, often times a catalog will list the Pitch Diameter which is measured mid tooth. You are measuring the outside diameter.)
Based on the measurements you gave you are looking for a metric M1.75.
M1.75, if converted to DP would be 14.5, but I have never seen such a gear or cutter. (Not that I have seen all that much)
Unfortunately Boston and Martin do not list any metric gears on their websites.
When I did a web search, companies that sold metric gears only listed M1.5 or M2.0 gear sizes.
This cutter on ebay will do the job at ~$28. I purchased some Chinese cutters a while back and found the cutters with a circle T manufacturers mark to be better than the I-star. This listing does not show a manufacturer mark, but the seller lists other cutters with the circle T mark, so I would assume the quality is acceptable.
I don't have any M1.75 cutters. If you were to send me this cutter, and a blank, I would be willing to cut the gear for you. I botched the first couple of gears I cut, but have done a pretty good job since then. But no guarantees.
A 16 tooth gear 1.125" in diameter is a 16DP. (You need to be careful, often times a catalog will list the Pitch Diameter which is measured mid tooth. You are measuring the outside diameter.)
Based on the measurements you gave you are looking for a metric M1.75.
M1.75, if converted to DP would be 14.5, but I have never seen such a gear or cutter. (Not that I have seen all that much)
Unfortunately Boston and Martin do not list any metric gears on their websites.
When I did a web search, companies that sold metric gears only listed M1.5 or M2.0 gear sizes.
This cutter on ebay will do the job at ~$28. I purchased some Chinese cutters a while back and found the cutters with a circle T manufacturers mark to be better than the I-star. This listing does not show a manufacturer mark, but the seller lists other cutters with the circle T mark, so I would assume the quality is acceptable.
I don't have any M1.75 cutters. If you were to send me this cutter, and a blank, I would be willing to cut the gear for you. I botched the first couple of gears I cut, but have done a pretty good job since then. But no guarantees.
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- Joined
- Jan 29, 2014
- Messages
- 156
The Pitch Diameter is more of a theoretical value than something you can measure without special equipment. When you are calculating gear ratios you use the Pitch Diameter. I don't know why the catalog would choose to list the Pitch Diameter.
When measuring the gear it is easiest to measure the Outside Diameter.
The Pitch Diameter is the # of teeth/DP. So a 16DP gear with 16 teeth has a Pitch Diameter of 1"
The Outside Diameter is (# Teeth + 2)/DP. So a 16DP gear with 16 teeth has an Outside Diameter of (16+2)/16 or 18/16 or 1.125".
With metric gears it is the inverse.
The Pitch Diameter is the # teeth * M. So a 1.75M gear with 16 teeth has a Pitch Diameter of 1.75*16 = 28mm.
The Outside Diamter is (# teeth + 2) * M. So a M1.75 gear with 16 teeth is 18*1.75 or 31.5mm.
When shopping for the gear, don't worry about the Pitch Diameter. Just look for a Module of 1.75, pressure angle of 20 degrees and 16 teeth.
When measuring the gear it is easiest to measure the Outside Diameter.
The Pitch Diameter is the # of teeth/DP. So a 16DP gear with 16 teeth has a Pitch Diameter of 1"
The Outside Diameter is (# Teeth + 2)/DP. So a 16DP gear with 16 teeth has an Outside Diameter of (16+2)/16 or 18/16 or 1.125".
With metric gears it is the inverse.
The Pitch Diameter is the # teeth * M. So a 1.75M gear with 16 teeth has a Pitch Diameter of 1.75*16 = 28mm.
The Outside Diamter is (# teeth + 2) * M. So a M1.75 gear with 16 teeth is 18*1.75 or 31.5mm.
When shopping for the gear, don't worry about the Pitch Diameter. Just look for a Module of 1.75, pressure angle of 20 degrees and 16 teeth.
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