Making your own horizontal mill arbor

Mark_f

Registered
Registered
Joined
Jan 16, 2020
Messages
5
Horizontal mill arbors are very expensive to buy, mainly because they have to be precision made to turn the cutter accurately. You can make your own arbors and have the accuracy also with a little care when making.
I need a 22 mm arbor for some gear cutters I bought to make a gear.

The piece of steel must be set up to do all the turning in a single setup. This insures everything is concentric and will be true. (I somehow lost the picture of machining the arbor, but it is simple turning.) This is a picture of the finished arbor.
20171017_113816_HDR.jpg
One end of a piece of bar stock , longer than needed was chucked in the 3 jaw chuck and the other end was center drilled and set with the tail stock. All surfaces in the photo were turned and the threads were cut without ever removing the bar from the setup. When finished, the excess material that was chucked was cut off. This gave me a straight, concentric, and true arbor. All size tolerances were kept within .0005". This was the easy part of this project. The stub that goes in the milling machine collet is .750" diameter and 1" long. The section for the cutter is 6" long and sized so the 22 mm cutter is a snug sliding fit. The threaded end is 1" long and the threads are 18 TPI on the 22 mm diameter.

Next is the more difficult part but is just a matter of paying close attention and holding tolerances. The spacers used to fill the spaces around the cutter on the arbor must be very accurate. To buy these six spacers, the cost is almost $100. This is because they are high precision and hardened and ground. Being hardened and ground is not necessary but the precision is important. I made my spacers with the same bar stock used to make the arbor. I cut several pieces of bar stock about 1 1/2" long. These were chucked in the 3 jaw and drilled then finish bored to be a snug sliding fit on the arbor I made earlier. Next I need to machine the ends perfectly square to the bore. To do this I made an expanding mandrel to hold the spacers.
20171017_113943_HDR.jpg
The above photo is the mandrel mounted in an ER 40 collet chuck and a spacer mounted on it. To make the mandrel, I machined a stub on a pice of stock to fit the collet. Next the short bar was machined to a slip fit to the spacer bore. Then the end was drilled the length of the mandrel and the end tapped for 1/4 NPT pipe plug. The last part is to cut two slots in the mandrel 180 degrees apart. The mandrel only has to expand .001" to grip the spacers.

The spacer turns true when mounted on the mandrel and now the end faces can be machined square to the bore. This is probably the most important thing when making an arbor.

By leaving the spacer hang over the end of the mandrel, I can part of various lengths of spacers and then use the mandrel to face the spacer ends ( which must have a smooth finish).
20171017_111857_HDR.jpg
The above photo shows the spacers on the arbor held by the nut and a finish cut is taken on all the spacers and nut to make them all true on the OD and have a polished finish.
20171017_114910_HDR.jpg
This photo is the finished arbor ready to use.

20171017_114805_HDR.jpg
This photo shows the finished parts.

It isn't necessary, but I took the time to put a small chamfer on the ends of each spacer. It looks nice and makes it easier to see the size of the spacers (with sharp edges the spacers seams are hard to see and this is safer as the sharp edges are dangerous).

This same process is used to make any sized arbor. You just have to make another mandrel the proper size.

This arbor cost me $8 for the bar stock and I have a high quality arbor. I priced an arbor to buy and it was a little over $200. I like $8 better and mine works just as well.
 
Another tip on the spacers. Even though I got an excellent finish on the ends, to improve the grip when pressed together on the arbor and the cutter, I took each spacer and placed it against a piece of 220 grit sand paper laying on my granite surface plate. A light swipe, turn 90 degrees and another light swipe left a light cross hatch pattern on the spacer end. This did two things. 1. It assured me that the spacer ends were flat and 2. It removed any tiny machining "high" spots for a better fit and grip.

I have about 6 hours making this arbor, but I am confident in its quality. I mounted a cutter on it and it runs true.

You may notice I did not cut a keyway in the arbor or spacers. I have never used a key because 1. I would rather the cutter slip in a binding situation than break an expensive cutter. 2. I have rarely had a cutter slip ( without good reason).

Eventually I intend to cut the keyways ( if I ever catch up).
 
Nice job! It's very satisfying for me to make my own tooling... and, as you said, the price is usually right!

Turning in one setup is a good way to keep things concentric as you said. I am a little leery of having to cut off a lot of material from a shaft though after it's finished to size. It's probably OK in most cases, but I'm a worrier and am afraid that doing so could potentially remove or induce stresses that could move things a little. Probably not, it probably just me overthinking things...

I've actually had great luck turning between centers in cases like this. I have centers that I can put in my spindle, but if I want perfection (or as close as I can get to it) I will chuck up on a piece of steel and turn a nice, new, concentric 60 degree center to use. I've got one that I just true up when needed.

Sounds like the way you did it turned out great for you so the proof is in the pudding! :)

I like your expanding arbor! I'll have to store that away in the old memory bank!

Nice work as usual Mark,
Have fun,
Ted
 
Nice job! It's very satisfying for me to make my own tooling... and, as you said, the price is usually right!

Turning in one setup is a good way to keep things concentric as you said. I am a little leery of having to cut off a lot of material from a shaft though after it's finished to size. It's probably OK in most cases, but I'm a worrier and am afraid that doing so could potentially remove or induce stresses that could move things a little. Probably not, it probably just me overthinking things...

I've actually had great luck turning between centers in cases like this. I have centers that I can put in my spindle, but if I want perfection (or as close as I can get to it) I will chuck up on a piece of steel and turn a nice, new, concentric 60 degree center to use. I've got one that I just true up when needed.

Sounds like the way you did it turned out great for you so the proof is in the pudding! :)

I like your expanding arbor! I'll have to store that away in the old memory bank!

Nice work as usual Mark,
Have fun,
Ted
I only had to cut off about 1inch from the stub end. I have never had a problem with doing that. Turning between centers is the best way, but I have good luck puting the excess end in the chuck also. ( I need to get some drive dogs to turn between centers ).
 
Mark enjoy your builds this I too need to make , I have an atlas mill I bought last year , never even plugged it in yet. I want so bad to be able to get in my shop. It'll be next summer before I get it all finished cleaned out and set up . My planer is another priority for me it'll be so Kool having it pumping back and forth making chips fly. I can run up an down and a cross cuts at the same time . It's old but it's all there , only needs power .
Nice job on your arbor , looks like it w a s done on a CNC.
 
Mark,

Your arbor is a work of art! What material did you use? My junkyard steel rarely turns to such a nice finish.

Glenn
 
Mark,

Your arbor is a work of art! What material did you use? My junkyard steel rarely turns to such a nice finish.

Glenn
Usually I use 1018 cold roll. This one is a special size ( 22 mm ) and won't get used that much. I made it from 12L14 which machines nice. It is plenty sturdy and I take good care of my tooling and don't abuse it. I think I will make my next one ( a 1 inch diameter ) from 12L14 also.

I have learned to get a good finish even on my rusty junk stock. It all depends on the feed, speed and tool grind. After some experimenting, I kinda know what I need anymore. I also take a .001" finish cut if I want a really nice finish on something.
 
Back
Top