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That's a good start, since found out that there is a special version of the std gear cutters for doing bevel gears, but we will contact them and see if they have the version.
Can you say where you found out about special cutters for bevel gears ?
Ivan Law says a reasonable approximation (for parallel depth bevels) is to cut the teeth as per the inner face and then to angle each way and take a strip off each side of the teeth. You don't use the cutter for the number of teeth, but the cutter for a larger number of teeth as he specifies.
I'd like to know what the options are for improving on this are.
Can you say where you found out about special cutters for bevel gears ?
Ivan Law says a reasonable approximation (for parallel depth bevels) is to cut the teeth as per the inner face and then to angle each way and take a strip off each side of the teeth. You don't use the cutter for the number of teeth, but the cutter for a larger number of teeth as he specifies.
I'd like to know what the options are for improving on this are.
This is for a friends traction engine diff, I got involved as I did the maths according to the machinery handbook formulae, At one time he was going to use the nearest DP cutter to .3/8CP and got hold of some of the gear cutters same DP and cutter number but there was a differance in that the one engraved bevel gears was thinner at the tip. This made the gear too big so the hunt is on for CP bevel gear cutters. I will post more if we find them.
This is for a friends traction engine diff, I got involved as I did the maths according to the machinery handbook formulae, At one time he was going to use the nearest DP cutter to .3/8CP and got hold of some of the gear cutters same DP and cutter number but there was a differance in that the one engraved bevel gears was thinner at the tip. This made the gear too big so the hunt is on for CP bevel gear cutters. I will post more if we find them.
I am a little intrigued about the use of "CP" gears as it suggests that they are for gears that mesh with a rack or a worm that has a linear fractional pitch instead of a pitch with a "pi" function as is the care with normal circular pitches which are derived from DP (inch = ((no. of teeth)/(pitch diameter))) or modular pitch (metric = ((pitch diameter)/(no. of teeth))).
I have read the item on it at page 2034 in my Machinery's Handbook 27.
Just checked, I've got a No6 cutter for 3/8 pitch bevel, 14.5 degrees. That's the only 3/8 bevel cutter I have, but I do have 1,2,4,6 & 8 straight cutters in 14.5 degree and 2,3,5,7,8 in 20 degree 3/8 pitch. Also 3,5,6,7,8 in 8dp bevel.
Tim thanks for the offer I will get back to you by PM if we decide we can use some the ideal is 0.375 CP Bevel cutters No's 3 & 8.
Does any one know if you just substitute the Bevel cutters for the standard ones.
Following a previous thread where I asked about calculators for bevel gears. http://bbs.homeshopmachinist.net/sho...ht=Bevel+Gears
I did my own in Excel using the information in Machinery Handbook 27th Edition, the calculations are shown below and if any one is interested I will send them a copy if they PM me.
But I am now wondering what the effect of using the standard cutters is for bevels and if the Machinery Handbook is based on std cutters or bevel as I didn't know they existed until a couple of weeks ago.
I will print it out and have a look at it tomorrow and will get back to you.
As you are using CP instead of DP cutters and as most calculations are based on DP (inch) or Module (metric) - I am guessing here - you may need to convert the CP>DP.
I have a copy of MHB 27 and will check that as well.
See MHB page 2091 (first paragraph) regarding the thinner cutters for bevel gears.
Tim thanks for the offer I will get back to you by PM if we decide we can use some the ideal is 0.375 CP Bevel cutters No's 3 & 8.
Does any one know if you just substitute the Bevel cutters for the standard ones.
Following a previous thread where I asked about calculators for bevel gears. http://bbs.homeshopmachinist.net/sho...ht=Bevel+Gears
I did my own in Excel using the information in Machinery Handbook 27th Edition, the calculations are shown below and if any one is interested I will send them a copy if they PM me.
But I am now wondering what the effect of using the standard cutters is for bevels and if the Machinery Handbook is based on std cutters or bevel as I didn't know they existed until a couple of weeks ago.
Steve Larner
N prime for your gear ratio of 12t pinion by 44t gear would result in bevel cutters #1 & 8, not # 3 & 8. MHB & OT's PDF link show that a milled bevel cutter is thinned down in order to pass through the toe end of the bevel pinion/gear. Then one has to rotate the gear & offset c/line by a calculated amount to achieve proper thickness.
Cheers,
Les H. The Impossible Takes Just A Little Bit Longer!
N prime for your gear ratio of 12t pinion by 44t gear would result in bevel cutters #1 & 8, not # 3 & 8. MHB & OT's PDF link show that a milled bevel cutter is thinned down in order to pass through the toe end of the bevel pinion/gear. Then one has to rotate the gear & offset c/line by a calculated amount to achieve proper thickness.
Cheers,
As an 8DP cutter will be a whisker smaller than for 3/8" CP, what about using 8DP (if you can't find the right CP cutters) and just opening out the cut a fraction more to compensate? It's a fairly low speed application, I don't think the original traction engine gears were super-precision items.
As an 8DP cutter will be a whisker smaller than for 3/8" CP, what about using 8DP (if you can't find the right CP cutters) and just opening out the cut a fraction more to compensate? It's a fairly low speed application, I don't think the original traction engine gears were super-precision items.
Tim
Good call Tim, as an aside for the UK guys I called into Manor Foundry at Ilkeston last week and spoke to John the owner.
He's been advertising on the free adverts web site that they now do cast iron.
He showed me a sample which was a bevel gear for a traction engine, one of the side bevels as opposed to the pinions.
This was about 5" diameter, guessing 40 teeth about 10 DP.
The teeth were that smooth that they looked like a die casting, I have only seen castings like this on some of the very old Stuart engine kits.
I asked how much as an example and was told about £15.
All this gear needed was the bore boring out, no other machining or fettling was needed.
They do one off's or bulk and understand what people need, usual no connection other than the fact i have used this company for 15 or so years with no problems.
.
.
Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.
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