Casting brass.

[roncohudd]

Need help on how to cast a 2" round x 3" long brass to make a gear for my lathe. Broken drive gear.

 

[GreenTwin]

I think bronze may be what you need.

I see folks brazing up gears and then grinding or cutting the tooth (teeth) back to shape, and it would seem that would be the easiest and quickest fix.

I have tried casting one gear, and could not get it to pull from the sand cleanly enough to be of any accuracy.

If you are going to cast a gear blank, and then recut the teeth, why not just braze the broken tooth/teeth, and cut those teeth only?

.

 

[roncohudd]

I think bronze may be what you need.

I see folks brazing up gears and then grinding or cutting the tooth (teeth) back to shape, and it would seem that would be the easiest and quickest fix.

I have tried casting one gear, and could not get it to pull from the sand cleanly enough to be of any accuracy.

If you are going to cast a gear blank, and then recut the teeth, why not just braze the broken tooth/teeth, and cut those teeth only?

.

I might braze the bad teeth if I can't get something to make another one. I really need to get the lathe going. My Atlas isn't as hefty as th Grizzly. The gear an shaft are not available.

 

[fltenwheeler]

Get so bronze screws and drill and tap the gear. Then braze the area and recut the gear.

Tim

 

[Steamchick]

My Dad repaired a cast iron gear with a piece brazed in and 3 new teeth filed carefully....- as good as new - to drive his lathe.
Depends on your skill.
K2

 

[roncohudd]

My Dad repaired a cast iron gear with a piece brazed in and 3 new teeth filed carefully....- as good as new - to drive lathe.
Depends on your skill.
K2

My skiis certainly aren't what they use to be, but I can do it. If I braze it I'll probably recut on the Bridgeport. My machining skills are better than my welding skills.

 

[roncohudd]

machining

I did make the shaft yesterday.

 

[MRA]

If you are sure you are going to machine the missing teeth, you might find this useful. It's an effort to make the rack-form (not helical) hob, but it works - I have done it for Boxford change gears. I hardened mine with Kasenit in a small pot left in the woodstove for the evening.

http://www.helicron.net/workshop/gearcutting/method/
You might prefer to just buy the involute cutter you need, or even cut the teeth with a slitting saw and then sort out the flanks with a file. I seem to like putting lots of effort in to save a few quid.

 

[roncohudd]

Brazing came off better than I expected. Found a slit saw in my stash for the first cut. If not for the 5⁰ angle it would be easier. But that's why we are called machinist.

 

[davidyat]

My Dad was a welder in the 1950's. He repaired this machinist's vice with brazing. 70 years later, it still works fine and smoothly:

 

[roncohudd]

If you are sure you are going to machine the missing teeth, you might find this useful. It's an effort to make the rack-form (not helical) hob, but it works - I have done it for Boxford change gears. I hardened mine with Kasenit in a small pot left in the woodstove for the evening.

http://www.helicron.net/workshop/gearcutting/method/
You might prefer to just buy the involute cutter you need, or even cut the teeth with a slitting saw and then sort out the flanks with a file. I seem to like putting lots of effort in to save a few quid.

Yay. Got my lathe back together. Brazed and recut the gear. All finished and running. Thanks everyone..

 

[TSutrina]

Cut any gear with just a slitting saw​

https://duckduckgo.com/?q=cut+gear+...i=https://www.youtube.com/watch?v=eC-OctJoWv4or

917,268 views Jan 14, 2022
This is about the simplest way to make an accurate gear with the minimum of equipment, just a milling machine and a rotary table, no special attachments, no hobs or special cutters. And best of all you can use this method for any gear, even obscure sizes you can't get cutters for. You can download the spreadsheet for free from my Patreon page (no Patreon account or donation required): https://www.patreon.com/posts/61153468

patreon site
Cut any gear with just a slitting saw (spreadsheet here)
Here is the spreadsheet that goes along with the video:

Hopefully it's self-explanatory, just enter the parameters in the green boxes and it will calculate the cuts needed.
NB. you don't need to actually need to draw the lines on the blank to start with, I just did that for the video to show what's going on. After you make the first cut for each side of the tooth it should be obvious if you're about to make a cut in the wrong place and slice off a whole tooth.

Note that not all cuts will be inside the gear blank, especially with low tooth-count gears, and some will only take off a tiny sliver, so you need to experiment a bit with the cuts lower down each column to see which work best.

The spreadsheet is provided for free, but if you find it useful please consider making a pledge.
* 17 Jan 22 - Added Imperial tab to the spreadsheet (by request)
* 11 Jun 22 - Added a field to include profile shifted gears (not tested, use with care and only if you know what you are doing!)

gears with slitting saw.ods
gears with slitting saw.xlsx
gears with slitting saw.xls

 

[TSutrina]

 

[MRA]

Goodness. That's something I can follow because you were bothered to work it out...and put hours of work into the video...but I don't think I would have had the patience! Well done, really lovely teaching presentation. I think I'm rather glad that youtube was not a thing when I was teaching, and I could get away with pencilled notes and a roller blackboard

Edit: all this got my daughter and I to dig out a pile of gear bits I have lying around here...including a really big worm wheel which turns out to have 314 teeth. I wonder what it was for (found in a university scrap bin). 314 doesn't seem like a very useful number, unless it is something to do with an approximation for 10.pi...?

 

[user 284]

Only guessing, but a 314 tooth worm wheel and found in a university scrap bin might have had something to do astronomical tracking? 314 doesn't have a whole lot of evenly divisible numbers, so as a means of dividing unless it was for something very specific seems doubtful. So either a method of deep gear reduction on something fairly uncommon, or that tracking seems more likely.

 

[Sprocket]

Sounds like it might be 100 Pi. Constant relation of circumferential distance for any diameter they used. Maybe?
Just a thought having had Pi Day this week.
Doug

 

[user 284]

Yes it could be Doug. If so, and a high tooth count worm wheel in the scrap bin wouldn't have any additional clues if there was also some form of gear correction mechanism to then get a whole lot closer to Pi than 100 x 3.14. Hard to say, but since Pi is easily calculated but always with imperfections from exact, it's tough to figure out what a mechanical method would be used for if it was only for getting to that Pi number. I've also been wrong before.