Horizontal Milling Arbor

[francist]

I decided I needed to cut some gears, it seems to be a popular thing these days. The key word here is "decided", not "discovered", making this purely an adventure of desire rather than actual necessity. But it's a hobby, right? It's supposed to be fun.

Anyway, to cut said gears I would need gear cutters of which I had none. And the gear cutters I could find for the pitch I wanted (24 DP) all came with a 1" arbor hole. I have two arbors, both 7/8" diameter, of course. Hmmm....

I started with a piece of 1-1/4" 1018. I would have preferred 12L14 but my regular source is no longer stocking a lot of it anymore so 1018 was pretty much my only local option.

The spindle this has to fit has a #2 Morse taper and 3/8"-16 drawbar threads, so I needed to get those into the end of my 11" long bar somehow and without a steady rest. I opted to just mark out for centres by hand and then drill them using the drill press. In the same setup, I drilled and tapped the one end for the threads. Then I put a short hex bolt into the lathe collet, drilled a centre in the head, and then threaded that into the newly threaded drawbar end to reclaim the centre for turning the shaft.

And after all that talking, here it is on the lathe. I wasn't sure if I would get movement in the bar going from 1-1/4" down to 1", so I roughed all the dimensions first to about 50-thousandths oversize. It's been a while since I've turned between centres but I find I quite like it. At first I was getting quite a lot of chatter, so I changed from my ball bearing centre to a solid one and it quickly disappeared.



This was my first time cutting a Morse taper, and also the first time using the offset tailstock method. It works great! I would have liked just a hair better fit though, but I ran out of diameter before I could make that happen. It locks in ok and I think it will work, just didn't get quite as nice a bluing as I was hoping for. Next time.



I did get the main 1" diameter on the money though, as well as the threads for the arbor nut. Did I mention this is for a horizontal machine? Well it is.





There also needs to be a collar just ahead of the Morse taper that can engage the drive dogs. Rather than having to use a bigger, bigger bar and turn the collar integral to the arbor, I decided to thread one on separately. And in order for that not to undo itself under load, it would have to be left hand threads. First time for those too.





Cutting the keyseat for the full length of the shaft was less than elegant but it got done, and when the dust had settled all the pieces fit together. I still need a few more gear cutters to make up a set, but I've got two or three to play around with in the interim.



Thanks for looking!



-frank

 

[markba633csi]

Nice job Frank- I like your little 3-sided tool post also, it's cute as a bug
Mark

 

[francist]

Thanks Mark. My objective was to try to get maximum tool footprint but still maintain full rotation without hitting the little hump on the compound. I don't know that it accomplishes that any better than others, but it was an interesting exercise. And it's still my go-to post.

-frank

 

[Martin W]

Great work Frank. Very professional looking.
Cheers
Martin

 

[f350ca]

Very nicely done Frank! Interesting that the solid center helped with the chatter, will try that.

Greg

 

[buffdan]

very nice, inspiring.. Thanks for sharing

 

[brino]

Hi Frank,

Lots of "firsts" for you on this project.
It appears they all turned out very well.

It is inspiring, thanks for sharing!

-brino

 

[francist]

Thanks Brino, and yeah you're right -- quite a few firsts on this project.

I actually thought a little about that when I'd finished. These operations aren't complex by any stretch, but if you haven't done them before you are hesitant because you're not sure how to go about them. It made me wonder at what stage in our process we become comfortable with trying something, where we derive the confidence from.

I've often felt that as we get older and try new (for us) things, we sometimes expect that we should know how to do them right away. After all, we've spent our whole working lives knowing what we do. We forget that we still have to learn, regardless of how old we are. You can't just think "I'm good, no need to learn the basics here, already spent 50 years doing that...". Fortunately I've always liked learning from the ground up, the down side is that there will likely not be enough time to learn all the basics for all the things I want to learn to do!

-frank

 

[brino]

Frank,

My problem is that I only get into my shop for a few hours a week.
Maybe I've done an operation before, but it was so long ago I forget much of what I knew when I last did it.

Fortunately I've always liked learning from the ground up, the down side is that there will likely not be enough time to learn all the basics for all the things I want to learn to do!

Good thing I like learning too, because I get to re-learn some things every year or two.

-brino

 

[Bi11Hudson]

Like you, I was cutting gears on the Atlas horizontal, an MF-B. In my case, the mandrel was one inch. I considered trying to make a 7/8" for the gear cutters. But much of what I do is in metric. And the (cheap) metric gear cutters have metric centers. In several sizes... I would end up with half a dozen chunks of steel to care for, et al.

What I ended up doing was acquiring a number of MT-2 single ended mandrels. They had spacers and lock nuts and worked well enough. Some had 3/8-16 hold downs, some metric at M10X1.5 which is so close to 3/8-16 that if you sneeze you'll miss the difference.

The caveat, of course there's one, is that most of my work is fairly small, under 1-1/2 inch. The single ended mandrels would fit, but brought the work close to the column. The indexer had to be set over near the inside edge of the table. Doable, but things were very close. The indexer won't fit past the column, that sort of close.

On the other hand, I have a cheap (HF) Chinese vertical milling machine I usually use for a small drill press. By getting an adapter from R-8 to MT-2, the vertical machine will work (I think) to hold the cutters. I haven't tried it yet, but it looks like it will work. I don't know how far it can open up, a 16 DP. 127 tooth gear is a handfull. But I want to at least try to make one, one day.

Which brings up a theory. There are milling cutter holders that are MT-2 to whatever. I use 1/2 inch adapters. The sort that uses 3/8-16 hold downs... A mandrel of some specific size cut down to 1/2 inch on one end and the over arm bearing on the other. And the appropriate flat on the 1/2" end plugged into the milling adapter. On the MF-B, the overarm can be run in or out as needed. So the mandrels needn't be full length. Only 8" would be long enough. The biggest issue would be collars, keyways, lock nuts, that sort of thing.

Why oh why didn't I think of that before I spent all that money on the short mandrels. Ces't la vie... Not enough coffee, perhaps. Of course, such a mandrel probably wouldn't stand up to working hard metal, but brass or aluminium with a slow feed should work OK. What think you?

The metric gear cutters came from China, Russia, all sorts of Far East countries. They may or may not be that accurate, but my builds work well enough. The biggest issue is that they were cheap, under $100 per set of 8. The only hold back is bore size, they're all over the map.

It works for me, I don't know about you. But worth looking into.

Bill Hudson​