gear cutting - change gear for lathe - amateur method

[jcs0001]

I may have mentioned in other postings that I bought a used King 10x22 metal lathe about 20 months back.  The change gears and a few other items were in a metal box near it and the lathe was on a pallet.

It was missing the chuck key for the 3 jaw chuck but other than that it all seemed to be there.  Recently I have been doing some threading with it and realised that the 36 tooth change gear was missing.  It turns out that that particular size is used for a lot of threading setups.  I found that King lists the 36 tooth gear for a bit more than $50 Can - if I can even get it and one can also add shipping and taxes to that.  I have had a few other gears on order with Grizzly since I bought the lathe so didn't bother to explore that route.

Anyway it did occur to me that if I had to make a gear a 36 tooth one was probably the easiest to do.  I checked around the web and found this website with good information as to how to make the gear:

http://users.picknowl.com.au/~gloaming_agnet/cq9325rev7.html

Other sites were found including the deansphotographica website.

I have the above mentioned lathe, a taig manual mill, a small rotary table and (just purchased) a tailstock for the rotary table.  It seemed easiest to use the mill and rotary table/tailstock.

It took about 2 weeks of part time work in a cold shop to get set up and about 1/2 hour to actually make the gear.  I had some scrap brass so cut it into several disks and cleaned them up on the lathe.  Also made an arbor for my small four jaw chuck (I had already made a mounting system for that chuck on the r/t.)  It took some time to make a mounting plate and some mounting washers for the r/t and tailstock so that they would be secure on my mill.

I recently obtained a copy of Screwcutting in the Lathe (Cleeve) and with the help of John Moran's website I made the lathe tool grinding jig.  It is very easy to use and I was able to use it to grind a 1/4 in. square piece of hss to use as a single point gear tooth cutter.  One end of a 1/2 in. boring bar was sacrificed - the type that holds a 1/4 in. tool blank at right angles to the bar.  It was cut short and mounted in a taig collet bored to 1/2 inch.

Cleeve sharpening jig with completed 60 deg. threading tool:


Mandrel and gear blank:


Setup in the Taig manual mill:


Another shot of the r/t etc. on the mill:


And the final result - the brass gear with an original steel change gear:


I made two 36 tooth gears since it didn't take long once the setup was done.  The cutting was done in two passes - about 50 thou. then another 32 thou).  I suspect that the setup would have been ok with one pass but didn't want to abuse the machinery.  The gears mesh quite well with the other change gears and I plan to run them in the lathe to improve the contact.  The other change gears are steel so I figure the brass will wear in quite well.

This is one of the more complex operations I have done with my mill and I was very happy with the results.  My next adventure in gear making will be the 40 and 60 tooth gears (one on the spindle and one below it).  They are plastic and I am concerned that at the wrong possible time they will self destruct.  If I can't source some good plastic I will likely use aluminium.  They are a different tooth profile so I will have to make another cutter.

John.

[pjf134]

 John,
  Good job on the gear. I too am making a setup to make gears, but not there yet, but almost. I have 2 CNC machines lathe and mill both Sherlines with all kind of extras with it except a tail piece for the rotary, so I guess I will have to make one. I was going to try Inkscape program with EMC2 on the Sherline or maybe Vector, which I have used before for a router table. Right now I am building a power hacksaw, just got tired of the hand one. Last year I started a home shop with a South Bend 9A lathe which I rebuilt and now use. So which way did you use for the keyway, broach or lathe?
 Paul

[jcs0001]

Paul:

For the keyway I put the gear blank horizontal in my mill vice and roughed out the opening with a small end mill.  I then finished it with a small file.  It was quite quick to do and worked well.

I think that my set up would have been secure enough without the r/t tailstock, particularly if I took several cutting passes for each tooth.  At first I considered some kind of support on the outboard end of the mandrel using my mill vice or something similar however busybee tools had the tailstock on sale so I ordered one.  There is no doubt it does help in holding things rigid and I'll find other uses for it.

Sounds like you are really into the cnc control items.  That is well beyond my expertise but would certainly be very nice to be set up for.

Several years ago I purchased one of the 4x6 chinese metal cutting bandsaws used.  Even though it appears quite flimsy I find it to be one of the most useful tools I own.  I imagine you will find your power hacksaw quite useful also.

John.

[pjf134]

 John,
  I was going to get the HF bandsaw and I still might since I am hurting for room right now in my shop, just figured the hack saw took up less room for now. I have to do some spring cleaning in the shop so I can add more stuff.
 Paul