How would you ....

[dbb-the-bruce]

An update ---

I've worked out how to set my lathe up as horizontal mill so I can use my gear cutters to cut 6" long racks. I made and adaptor that threads into cutter arbor instead of a drawbar and I can drive it from a 1/2" collet. It's going to let me cut multiple racks at once in brass. I've worked out how to accurately advance the carriage for each tooth.

I've also figured out how to cut the sawtooth profile - if I decide I really need to do it.

Here are the pic for the horizontal gear cutter setup on my lathe.



Thanks again for the suggestions, definitely helped me work it out.
-Dave B

 

[stioc]

I like that gear cutter idea on the lathe. However, wouldn't that give more of ^^^^ profile as opposed to /|_/|_/|_/| profile?

 

[dbb-the-bruce]

I like that gear cutter idea on the lathe. However, wouldn't that give more of ^^^^ profile as opposed to /|_/|_/|_/| profile?

Yes - this doesn't do the sawtooth, although I could now make a custom cutter for that (would be a pain to do with for more than a single face cutter). Somewhere up thread, I mentioned needing to cut racks also. This solution is best for that, I thought that I was going to make a vee shaped D-bit and do it on my mill - this setup lets me use existing gear cutters, the same ones I used to make the gears.

The setup shown on the lathe is really not super-stiff. Not sure it would work all that well on bigger teeth / steel. Fortunately I'm working in brass and can take it slow if I really need to. I could also work out a stiffer setup for the future. This will at least prove process of using the lathe.

The milling attachment for the lathe works, but it's awkward and can be difficult to setup without interference. The spacing of the cuts for the teeth is going to be manual this time - I don't have any direct readout of carriage position. The spacing is an odd number, something like 0.1936. I'm going to use the carriage stop and make a precise reference block to advance after each tooth. Should be pretty accurate.

In the long run, I might attach a motor to the lathe feed/thread drive shaft with and do it digitally. That could also provide me with variable feed, reverse and ability to precisely advance the carriage.

Just want to get the racks done for now!

-Dave B

 

[homebrewed]

Let us know how your stop+reference block idea works out. I'd thought that adding a handwheel+dial to your lead screw would be a solution but the oddball tooth pitch would make it difficult to keep track of where you are.

 

[dbb-the-bruce]

Here is a screen grab of the rack detail from Fusion:



Heading to the bat-cave to make the reference block and do some trial cuts.
Ultimately, I want to stack up 2 or 4 and cut them all at once. Thoughts on how to pin/bolt/hold 4 - 6" x 0.5 x 0.125 brass plates in perfect registration while cutting?

-Dave

 

[francist]

Cut the blanks slightly oversize, glue them in a stack with cyanoacrylate, mill stack to dimension, cut teeth, separate using torch or acetone.

 

[T Bredehoft]

Use one piece of brass, wide enough to cut into however many racks you want.. 3 1/2 inches wide? with ..040 wide slitting saw to cut them apart?

 

[RJSakowski]

Are you sure that the spacing is .1963"? .1969" is 5mm. It has been my experience that design dimensions are usually nice round numbers.

 

[dbb-the-bruce]

Are you sure that the spacing is .1963"? .1969" is 5mm. It has been my experience that design dimensions are usually nice round numbers.

My cutters are 16 DP, 14.5 PA. For a rack tooth spacing is == CP and CP is Pi / DP or 3.1415 / 16 == 0.1963495.....

If you have "Gears and Gear Cutting" by Ivan Law, see pages 33 & 57.

The cool thing is that I did the CAD drawing based on DP and PA and the tooth spacing as measured on the drawing matches the formula.

 

[dbb-the-bruce]

Now for the bad news.....
I managed to friction weld the tip of my dead center into the center hole on the bottom of the arbor Of course this happened when I was finally ready to cut a trial rack.......

I don't think I'm going to be able to clear out the center hole of the bottom of the arbor - both hardened steel. The nut on the bottom of the arbor is a metric thread. So my plan now is to get the correct tap and make a softer, longer nut without a threw hole and then center drill the bottom of it.

Or I could by a horizontal mill (please talk me into it!)

Time for a nip and call it a day.

-Dave