I Need A Gear Made...

[4GSR]

That's why a person needs at least one 3-jaw chuck that allows you to put bolt on soft jaws to hold stuff like this.

 

[MilGunsmith]

Hold it in the reversed jaws with some small scrap aluminum blocks between the jaws and the work as sacrificial jaws. You are only concerned about the thickness for this setup.

 

[GenePoole]

Update:

I'm still waiting on my gear cutters to arrive. I guess they are coming from China. Amazon failed to make that very clear.

In the mean time, I've created a mandrel from an old AR15 barrel. I had some 4140PH, but it was 2 inch diameter and that would have been a lot of cutting. The barrel is 4150 so it will make an excellent mandrel plus it already has a hole in the center for threading. I made a boss at 0.682 and another at 0.500 I can use the 0.500 to face off the 5/16 blanks to 0.275, then open up the hole to 0.6825 for the final dimensions.

 

[HairFree]

Currently I am refurbishing a 1945 South Bend 10L Lathe. Model 8187ZN - Tool Room model with a single tumbler quick change gear box.
There is a single gear that has confounded me - can't find NOS, used ones are worn beyond what I have now.
Like a crazy person, I humored myself by submitting RFQ's to some commercial gear makers - Boston Gear declined, not worth their while, while others came back with prices that literally took the air from my lungs. (as in I could buy a new Grizzly 10" machine for the same cost)

The gear in question is the Tumbler Arm Idler Gear for the Quick Change Gear Box. I believe it is PT-605R1.
It is the style that is supported on both sides by the Tumbler Arm and has a pressed in needle bearing - Torrington GB-88 (.500 ID / .682 OD)

The gear measures out to the following dimensions:
2.062" OD
.682 ID
.275" Thick
27 Teeth
Pressure Angle 14.5 deg. (so I have been told)
Material cast iron.
I have been told it is a 14 Diametrical Pitch

Is there anyone out there has one to sell or can make this?
Making a gear is way above my paygrade.


Thanks in advance.

Scott

Depending on your machining skill level, access to a milling machine, and ability to work without detailed drawings, yes you can make one at minimal cost and without special equipment. Before I go any further, all the above must apply.

 

[GenePoole]

My gear cutters finally arrived yesterday. I have to say that I'm impressed with the overall quality. Anyhow, I went to my shop today and decided to attempt my first gear. I did all the math from the Machinery's handbook and I must have missed a decimal point or something as I ended up cutting just a little too deep--by about 6 or 7 thousandths. I think it may have been that I had to do a very unwieldy calculation to be able to gauge the gear over wires with the wires I had (B&S PeeDee thread wires). The ideal wire as calculated by the Machinery's equation was 0.1234. I have 0.120 and 0.127 in the PeeDee set. Either of those should work, but unlike a Vee thread, you can't just add or subtract the difference due to the involute profile. You need to calculate based on this:

So the the OP, @opsoff1 I'm not sure how bad it is, but it must be better that what you have. The handbook math says it should be 2.0851 - 0.003 for proper backlash, and as you can see, it came out to 2.074 so about 8 thou too deep. I can send it to you and in the mean time, work on another. Live and learn.

 

[john.k]

Since the gear centres and meshing are adjustable on change gears ,I wouldnt think a few thou would make the slightest difference.

 

[GenePoole]

Since the gear centres and meshing are adjustable on change gears ,I wouldnt think a few thou would make the slightest difference.

It's not a change gear, but an idler gear for the quick-change gear box. (I think) it rides on the lower selector lever and engages various gears in the QCGB depending on which hole the plunger is set into.

 

[13engines]

Haven't read all five pages of posts so don't know if the OP got his gear yet or not, but thought I'd share this for future gear needing heads.

Misumi, a great website sort of up there with McMaster, has an online Gear Generator. At least they did about four or five years ago. I needed about a 1 inch Spur Gear for a twin door combo movement mechanism on a Mori Seiki Mill. It had a post and shoulder, a couple counter-bores, a circlip groove, you name it. It took a little thinking, but I specked every single dimension using their part number generator. Even the plating which was Black Oxide. While I was there I even order the small bearing and circlip and special washers. If memory serves, about $85 and two weeks tops. I think it was even faster then that. It was one of the most "How-is-this-even-possible?" things I've ever experienced.

Not sure if it's still there, but if you need a gear take a look. I have a picture of the gear somewhere. If/when I can find it I'll toss it in here.

 

[EmGo]

Misumi, a great website sort of up there with McMaster, has an online Gear Generator. At least they did about four or five years ago. I needed about a 1 inch Spur Gear for a twin door combo movement mechanism on a Mori Seiki Mill.

Unfortunately for this job, all module and all 20* pressure angle. They are kind of like a Boston Gear or Browning that didn't go wackaroonie on prices so ja, probably helpful if you can use a metric 20* pa spur gear.

 

[Dobermann]

Having made a couple of those idler gears using my vertical mill and a rotary index table I can advise you not to cut the full depth of the gear tooth before moving to the next one. If you take light cuts for each tooth and then rotate you'll be able to see if you've made an error before you get all the way around and have to start all over.

 

[GenePoole]

Having made a couple of those idler gears using my vertical mill and a rotary index table I can advise you not to cut the full depth of the gear tooth before moving to the next one. If you take light cuts for each tooth and then rotate you'll be able to see if you've made an error before you get all the way around and have to start all over.

I calculated a total depth of cut from Machinery's Handbook, then backed off by about a third. After getting all the way around, I measured over wires while still fixtured, then adjusted to the final depth based on the wire reading, and made my final cut all around. I had my 3D printed gear as a sanity check and before cutting the final steel gear, I did it on two test blanks made from aluminum.

 

[HairFree]

OP,
do you have a mill? If so you can use your good 27 tooth gear to make a new gear, but you will have to buy the cutter. Its not that hard to cut a straight gear.

I have a 10L similar to his only older. Repaired a gear with broken teeth by brazing and recutting. I made a fixture that used the good teeth to locate the ones needing recutting. The difference, a hand ground hss cutter in a stubby boring bar. Something similar could be done to make a new gear. Of course a commercial cutter is better and 54 tooth gears are available really cheap for a template. Depends on whether he has the skills to do this.

 

[HairFree]

I have a 10L similar to his only older. Repaired a gear with broken teeth by brazing and recutting. I made a fixture that used the good teeth to locate the ones needing recutting. The difference, a hand ground hss cutter in a stubby boring bar. Something similar could be done to make a new gear. Of course a commercial cutter is better and 54 tooth gears are available really cheap for a template. Depends on whether he has the skills to do this.

 

[stephen thomas]

I calculated a total depth of cut from Machinery's Handbook, then backed off by about a third. After getting all the way around, I measured over wires while still fixtured, then adjusted to the final depth based on the wire reading, and made my final cut all around. I had my 3D printed gear as a sanity check and before cutting the final steel gear, I did it on two test blanks made from aluminum.

I won't criticize anybody - gear cutting on a vertical mill is a fraught operation, as is sizing and gaging.
We're all amateurs.

One thing in your set up is that if you went one time around first (correct) the deflection at the gear cutter spindle overhang combined with the deflection of the gear blank stick-out on the thin mandrel might have added up to a couple/3 thousandths. (up to maybe .005 on the PD, depending) & it might not be uniform all the way around. Especially without a TS. When you measured and then took a light finish cut, there was less deflection and the cut was deeper than expected.

Aluminum cuts differently than steel.

Put a back stop (smooth angle plate) contacting the blank on the opposite side from the gear cutter, making sure the contact is parallel. If the arbor is not supported by a center, maybe make it a little stouter.

Per Doberman, for that (deflection) and other reasons, i cut near full depth first pass and count on using the dials and infeed measurements (mounted long travel dial indicator to cross reference the machine dials) to assume i'm where things belong. I leave an expected .010 to .020 cut for final pass "depending". Then do the final infeed on the conservative side. Check the centers before final pass.

course my method usually leaves the PD a little oversize.

Then you have to juggle that considering SB machines that need a gear already have loose tolerances, and SB was not stingy with gear clearance to begin with......

 

[GenePoole]

I won't criticize anybody - gear cutting on a vertical mill is a fraught operation, as is sizing and gaging.
We're all amateurs.

One thing in your set up is that if you went one time around first (correct) the deflection at the gear cutter spindle overhang combined with the deflection of the gear blank stick-out on the thin mandrel might have added up to a couple/3 thousandths. (up to maybe .005 on the PD, depending) & it might not be uniform all the way around. Especially without a TS. When you measured and then took a light finish cut, there was less deflection and the cut was deeper than expected.

Aluminum cuts differently than steel.

Put a back stop (smooth angle plate) contacting the blank on the opposite side from the gear cutter, making sure the contact is parallel. If the arbor is not supported by a center, maybe make it a little stouter.

Per Doberman, for that (deflection) and other reasons, i cut near full depth first pass and count on using the dials and infeed measurements (mounted long travel dial indicator to cross reference the machine dials) to assume i'm where things belong. I leave an expected .010 to .020 cut for final pass "depending". Then do the final infeed on the conservative side. Check the centers before final pass.

course my method usually leaves the PD a little oversize.

Then you have to juggle that considering SB machines that need a gear already have loose tolerances, and SB was not stingy with gear clearance to begin with......

Thanks you for the comments. I had considered a tailstock on the floating side of the arbor, but it was for a different indexer and was too short. I considered cutting a block to the right size for a spacer for the short tailstock, but wrote it off as unnecessary; perhaps I should have. At any rate, I ended up with a PD less than expected for the calculated backlash, but the OP (@opsoff1 ) has received the gear and says it may be a tad tight, so yeah, you're probably right with: "SB was not stingy with gear clearance to begin with."

 

[stephen thomas]

has received the gear and says it may be a tad tight, so yeah, you're probably right with: "SB was not stingy with gear clearance to begin with."

My point was that a slightly oversize (PD) gear might not be a bad thing in a worn SB lathe that may have also been built with clearance to the large side to begin with. In old machines, sometimes you never know until you try it. Either way is a risk.
(Unless the actual machine or assembly is on the bench to check in person)

smt

 

[EmGo]

the OP has received the gear and says it may be a tad tight,

If it rolls, it's okay. If it goes graunch graunch graunch no, but even the teensiest amount of clearance will be fine. As long as it's not negative, you won't have to cut it again

Run it around several times tho to make sure, there will be high spots in different places on all the parts, so make sure there's no negative combinations. But as long as it's even the smallest amount free, you're set.

btw, pitch diameter does not change. That's an imaginary number. There is no way to measure it, in real life it doesn't exist as a changeable number. It's tooth thickness that changes.

Example ; two gears on 10" center distance. Both the same size. The pitch diameters of both are 10". You can make all the teeth on one side really skinny and all the teeth on the other side really fat and even put the teeth on the wrong size blanks but if the centers are 10" and the two are the same number of teeth, the pitch diameters are and remain 10" each no matter what you do.

Took me about two years to finally grasp this

 

[opsoff1]

Update - first, I want to thank all the folks who chimed in and offered advice and their experience.
With the help of Gene Poole and others, I have been able to basically completely rebuild the gearbox.
New idler gear, NOS Pinion Shaft, I turned new bronze bushings, new needle bearing and some cannibalization of another gearbox - I was bale to create a beautifully functioning QCGB. As Gene mentioned, the gear was a tad tight, but it didn't bind and the "feel" was uniform for it's full diameter - given the new pinion shaft, I am sure it will function perfectly after mating in. (I'll post some pics at some point)
A HUGE thank you to Gene Poole and the others who helped me. I have learned a sh*t ton about gears throughout this process and have a new found respect for those that make them!
Situations like this make these forums invaluable.
Thanks again!

Scott