Thread: broken tooth on back gear

Mike what are you going to use (machine wise) to cut the tooth? A mill? I'm guessing you don't have a dividing head?

I have this to do (actually thanks for reminding me), and if I wasn't going to use the dividing head I'd probably approach it by setting the back gear spindle in V blocks and making up an accurate indexing pin to engage the gear's teeth and prevent it rotating. Setup the cutter and engage it in a good tooth next to the dud one, so you can set everything up including the indexing pin. Withdraw the pin so the backgear can rotate and rotate it around one tooth, insert the indexing pin to position the backgear correctly then tighten up the clamps holding the spindle down to make everything nice and rigid, then just cut the missing tooth.

I'll possibly be able to use my dividing head, but if not this is how I decided to do mine. Hopefully the explanation makes sense and provides a little food for thought.

Pete

PETE I dont have a Mill, but I could go down to the TAFE and use one if I asked them nicely .

I was going to use my lathe to do it, somehow ! It would be a learning experience , the mother of invention etc. I see you pin idea and has some merit . Its a AD HOC setup I will be using .

Mike

Your best choice would be to ask the Tafe if you could use their Mill.

If that is what happens and you have their tooling to also use the Dividing Head and Tailstock would be the preffered method.

You would need to mount your Backgear on an Arbor.

It wouldnt matter if the Mill was a Vertical or Horizontal although the Horizontal would be the more suitable.

If you decide to do it in the Lathe (or at least try) holding and positioning the Backgear will take some working out.

You will need a lathe that has a centre height of about 6" maybe a bit more if you wanted to mount the Backgear Horizontally,you could get away with a lesser Cetre Height if the Backgear was mounted Vertically.

If mounted Horizontally or Vertically you could possably get away with a Single pass cut depending on the ridgidity of the lathe.

If you had to do it in multiple passes you would need to either use a Milling type Cross Slide attachment or make up your own type of adjustable holder.

Originally Posted by morrisman

PETE I dont have a Mill, but I could go down to the TAFE and use one if I asked them nicely .

I was going to use my lathe to do it, somehow ! It would be a learning experience , the mother of invention etc. I see you pin idea and has some merit . Its a AD HOC setup I will be using .

Mike

Hmmm, lathe only 'eh? Ok another suggestion if you want to use a lathe only for this one tooth, is to grind a small lathe tool to the appropriate profile (ie the same profile as your cutters), then mount the backgear in the lathe in a conventional manner as if you were going to turn it. Make up a temporary indexing pin as I described above, but off the bed. You will also need to come up with a way to then lock the spindle without it moving from this indexed position. Index as I described above, lock the spindle, then use the carriage as a manual shaper to cut the tooth profile. I've seen this used to cut keyways, but don't know how well it would work for cutting a gear tooth. I suspect it would be slow going, and accurately grinding the profile (probably with a dremel style tool a PIA). In theory it should work, and the fact you should have all the gear there already could mean it's something worth pursuing. You could try it on the dodgy tooth you tried filing to see how goes. It may even be possible to somehow mount one of your cutters on the toolpost and use the cutting edge as the shaper tool. I'll leave this entirely to your imagination.

Pete

Some interesting ideas . Pete , I like your line of thinking ..its a easier method to do compared to other methods , mounting the gear in the lathe and having the cutting tool on its own external mount . Thanks all