Drill press restoration - Zapins

I chucked up the 42 hardness rod. Seems to machine fine. Doesn't feel grabby like mild steel.

I also did a bit of reading. Seems others make drive shafts from 40 hardness 4140 so I'm pretty much in the approximate range I need to be.

 

It will not shatter in the 40’s or mid 50’s

With a good cutter and a reasonably rigid lathe it should cut fine. You will just need to dial back on cut depths and probably SFM.
Almost certainly your tempering temp was low. At 1000F the steel should be just faintly glowing in ordinary room light. You can surely retemper if cutting is an issue.

Denis

 

K type thermocouples have problems when the junction ages, you'll probably fix it with a new thermocouple.

https://blog.wika.us/knowhow/aging-and-drift-in-type-k-thermocouples/

 

Alright so I made a lathe dog. I will start making a new drill shaft soon.

I also put the tailstock alignment bar back on and tested it again. Seems the tailstock was out several thousandths. I tried aligning it many times but I'm wondering if the wear on the ways is causing it to be difficult to keep the tailstock aligned? At some point I would like to buy a newer lathe with hardened ways and virtually no wear....

 

That's a nice dog! i swear I was suppose to cast some dogs for one of our members last year. It was going to be lost balsa, anyone see him?

 

Hmm I didn't see that lathe dog convo but it was pretty easy to make. Just took a couple hours to turn it down to approx the right size and tap it all. Turning between centers seems to work well as long as I keep everything aligned in exactly the same orientation when I put it back together it keeps it all lined up and centered nicely. Pretty freaking cool.

I made the jacobs #3 taper and test fit it. Seems to stick into chuck well and engages in multiple places on the shank so I think I cut it right. No wiggle that I can notice.

Now to cut the rest of the shaft to dimension.

Seems that cutting hardened metal is easier than mild steel. It deflects less due to hardness and less chatter which is nice. I keep noticing how shit my lathe bed is though. It has so much wear in it. I should still be able to cut a usable part however but it still galls me.

I'll buy a proper lathe one day with more horse power all nice and scraped in and accurate one day.... one day...

 

One day, you'll be making big doctor bucks. I wanna see a zero time BRAND NEW bridgeport in your garage. If you havent seen one in person, it really is jaw dropping!

 

I did price out a few models they can get up there in $$ for sure. I've seen some rebuilt and rescraped bridgeports for 9 k which is still 25% the cost of a brand new one. Definitely will buy some nicer more reliable tooling when I can afford it one day.

At least the south bend is letting me learn and practice.

Still would be nice to fully fix up the southbend one day but the motor is so weak I doubt it is worth it. 3/4 hp from factory...

 

Alright finished. I think the bearing seats are ok. Now I have to figure out how to cut the splines.

I think the shaft hardened all the way through to the center around 42 hardness because it still has a ring to it when hit and also scratches the original mild steel shaft (which has a dull thump).

 

I've had a good think about the splines and I think I may be able to cut them in using the lathe. I made a holder for my foredom and can therefore mount tool cutting bits into it and slide it down the part cutting the splines. I can most likely index my lathe pretty easily and I can make 3 passes to cut a "root" cut then two more passes per groove to profile the sides of the splines.

Which cutter do you think would work best for this?

Carbide burrs? A tiny end mill bit? Or rotary diamond, grinder disc or hss cutter?

 

I did some measuring on the original shaft (below) looks like the splines in the shaft have been cut with a rounded bottom. The sides of the spline teeth are are not straight. Looks like maybe a ball end mill might work. The distance between spline teeth was about 3.2 mm which is approx 1/8th inch ball mill. I might just be able to cut a slot with 1 super slow pass without cutting a root cut then side profiles?

What do you think?

 

The inside the bore picture looks like those could be straight-sided splines. I suspect that a perfect match is not required. Most likely closer is better, but the most important thing is good linkage for power transmission.

This was an interesting look at splines.
https://www.geartechnology.com/issues/0919x/spline-design.pdf

Denis

Added: Got power feed on your mill?

 

You could get a cheap 4" angle grinder, mount it on the toolpost with the wheel horizontal, then carefully dress the wheel profile to cut the same groove shape over a few passes to reduce the heating. Having a six position method of indexing the chuck would be a big help.

 

Got no mill. Only a lathe. It has power feed. I've got a 4.5" angle grinder.

The female splines seem straight the male part seems ball mill cut with rounded U shaped grooves.

 

If you can drill 6 equally spaced holes on your lathe chuck's backplate either on the rim or the back and arrange to have a pin engage the holes to lock chuck rotation, you could the mount the angle grinder on your toolpost and manually crank it along the shaft to cut the grooves. The angle grinder could be mounted with the wheel horizontal and the grinder body at right angles to the lathe ways and the grinder wheel and guard facing away from the operator.

 

I like it. I may do the same thing with smaller grinding discs in my foredom since the speed is more controllable and I already have the fixture built.

What do you think about trying a ball end mill? Seems I could get the same curved profile on the original shaft?

I might have to do a few test pieces and see what works best.

 

I suspect an end mill is going to need a fairly rigid setup and decent horsepower driving the ball mill compared to grinding the grooves but that's just my personal gut feeling. Grinding would likely need multiple light passes on all grooves to minimize heating and distortion to the shaft so it'll be time consuming.

 

I do not know how much travel you have in you crosslide and compound of you lathe. But, if you set your compound to zero degrees and used the travel of the compound and then the cross slide chances are you could put a hob or endmill in your chuck and cut the splines. The amount of power required to drive a endmill of about 1/8" diameter is very small. If you look at the paper I referenced above you will notice that the coving of the minor diameter of the spline is optional. The minor diameter can be flat. If you use an ordinary endmill in the lathe chuck, doing as much as possible to make a rigid setup for holding the shaft and the endmill will help get better results. Your chuck may be bell-mouthed. So making up a 3/4" or 1" "end mill holder" for the lathe may help. I'm thinking a 4" long piece of soft steel round center drilled to accept the endmill and using a couple set screws to retain the end mill. The grip of a worn chuck on the larger bar will be much better than on a 1/8 end mill stuck into the last 1" of chuck.

 

I will have to see how rigid the endmill is in the fordom holder but it should be pretty solid. Its a good machine and doesn't have a lot of wiggle. I also bought the high torque at lower speed version which is frequently used to grind out cast steel on engine parts etc. So it has a lot of power at low rpm.

I'll order some end mills and do a couple test runs and see if it works. If not the grinder it is.

I will need to figure out how to index the lathe. Would be nice to fit it with an index plate so I can make gears down the road.

Last night I stripped off all the paint from the remaining pulley housing and the iron table. In the process of repainting it now. I did the inside in silver so it would be brighter in there when opened, outside will be black. Its a shame about the prior owners careless drilling into the table but what can you do? I might try braze it with nickel/iron rods if I can get it to work. Or maybe I'll just live with it.