• This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn more.
  • PLEASE: Read the FORUM RULES BEFORE registering!

Rotex RM-1 X Axis drive gear replacement

rzbill

The cheapest thing in an airplane is the pilot.
Active Member
Joined
Feb 16, 2017
Messages
110
Likes
123
#1
As my signature says, I have a Rotex RM-1 horizontal mill with Rusnok vertical head. It has served me well.
This weekend, the x-axis power drive quit working, fortunately it happened at the end of the project I was working on. A quick look confirmed that the drive gear mounted on the lead screw was worn to the bone. It's a worm and worm gear combo. 10 years of use after I bought the used machine. Fair enough.
I know this needs pics so I will add these later as I move through the repair.
I have never found any documentation for the RM-1 so I am on my own as far as I know.
With the help of the Boston Gear documentation, I am confident that I have identified the gear as a 14.5 PA , 12 DP, 20 tooth, left hand worm gear. The worm itself appears to still be serviceable, unlike the gear. Possibly an earlier replacement by the previous owner.
I have found a Boston gear #1050ALH stock gear that is close enough (in regards to hub, etc) that I think I can make it work with some help from the Atlas lathe.
I will need to bore it, put a keyway in, and drill/tap 3 holes. I may need to turn the hub OD. There is 0.013" conflicting info on that aspect so we will see when I get the part in my hand. The hub is 1/8" shorter than the original which used a cap washer screwed to the face of the hub to retain the gear in its housing. I plan to make a stepped washer to replace the flat one. More Atlas work which will involve the deepest parting off I will have attempted as of yet.
I hope to get all the pieces and tools in place for Thanksgiving week since I have a few days I can spend on it.
The new things for me will be boring to a diameter and cutting a keyway with the lathe.

I'll keep adding stuff to this thread since there is no Rotex brand section as of today.

EDIT 11/12/17. I got corroberation of the above gear choice later in this rebuild. I was cleaning the parts in the washtank and found that the worm had a Boston Gear logo and part number GH-1056L on it. In the new catalog it is GH-1056LH which is a match for the gear I selected.
 
Last edited:

pineyfolks

Active User
Active Member
Joined
Apr 30, 2012
Messages
1,035
Likes
348
#2
My Rotex mill was missing the lever to lock the feed in. I made a simple replacement lever but I would like to see some photos of yours. Those are well built little machines.
 

rzbill

The cheapest thing in an airplane is the pilot.
Active Member
Joined
Feb 16, 2017
Messages
110
Likes
123
#3
Sure Pineyfolks, I'll include a shot of that piece in my pics to come.
Did you make yours to engage the 'trip' slide that kicks the drive out of gear automatically?
Nice to hear from another Rotex owner. :cool:
My mill appears pretty much original as far as I can tell from images I have seen of other RM-1s.
I assume the Rusnok was a later addition.
That x-axis power feed is really a handy feature.
Mine has the triple T slot table which may have been an option since I have seen images of a dual slot table.
As a convenience, mine came from the PO with a B&S #9 horizontal spindle that has a YY taper and collet nut which is the same collets used in the Rusnok vertical. Handy for them to be the same.
I have the full B&S #9 1" dia arbor and overarm too but I have never used it because the need has not arrisen in any project work.
I only have a few basic cutters for that arbor and I can do the same operations in other ways.
Too lazy to remove the Rusnok head. Its kinda' heavy. :confused 3:
 

pineyfolks

Active User
Active Member
Joined
Apr 30, 2012
Messages
1,035
Likes
348
#4
Hi Bill. I don't have a vertical head for mine. The horizontal taper is #9 b&s like yours and I have quite a bit of tooling for it. Mine also has a 3 t-slot table. My lever just engages the feed. I didn't have any photos of the auto disengagement setup.
 

rzbill

The cheapest thing in an airplane is the pilot.
Active Member
Joined
Feb 16, 2017
Messages
110
Likes
123
#5
Well that calls for another pic doesn't it? :grin:

Wish I could do it sooner but I am on the road 4 days a week. The shop is idle. :apologize:

I envy your arbor tooling inventory.........
 

rzbill

The cheapest thing in an airplane is the pilot.
Active Member
Joined
Feb 16, 2017
Messages
110
Likes
123
#6
Hi Pineyfolks,
Here are some picks I snapped when I got home last night.
The "auto disengagement bar" which is a slide mounted on a smooth 1/4" bar that has a flat machined on it for the set screw (currently SHCS).
The engagement lever. Square stock with a cylindical section at the top for smooth working with the disengagement stop and a nib on one side to hold the worm carriage up by supporting a square head screw sticking out from the worm carriage. I'll take anothe pic when its back together.
Lastly a pic of the old gear and its raw replacement.

X-Axis Trip.jpg X-Axis Trip Lever.jpg X-Axis Drive Gear Assy.jpg X-Axis DriveGear.jpg
 
Last edited:

rzbill

The cheapest thing in an airplane is the pilot.
Active Member
Joined
Feb 16, 2017
Messages
110
Likes
123
#7
Here's the first step. As mentioned above, there was a question about the hub OD. Sure enough, the OD as delivered was 1.263 which is a bit odd since it is a neither 1.250 or 32mm. Made a mandrel. Undershot the diameter slightly (dang it) so I lightly knurled it to tighten the fit to a light hand press fit.

Gear Mandrel.jpg Gear Hub Cut.jpg

Gear and Housing 1.jpg

You can see the Boston Gear ID numbers on the hub. Before cutting them off, I used a vibrating marker to write them on the face of the gear pointed at the jaws. In an earlier post, I mentioned that the hub is 1/8" shorter than the original part and I would have to make a stepped washer to compensate. Thinking about shortening the bore in the housing pictured above instead of making the stepped washer. Still debating since it would involve my first use of a 4 jaw (a positive, not a negative).

On a separate note regarding machine runout, The shaft I made the mandrel from had been turned previously so I had a good OD to work with. I decided to check the Bison chuck runout with my Last Word. I had already checked the spindle some weeks ago at 0.001 on both the OD locating diameter and the Morse taper. Today the Bison I got with the machine purchase checked at 0.0015 reading worst case. Happy happy of course since this is NOT one of the set-tru style chucks. I'll check it again in the future when I have some ground rod for a better measurement.

I cut the hub OD but that is as far as I can go until I get some different tooling to work on the bore and do the keyway. I may go to Horror Fright later today and pick up a micro lathe bit kit that has a tiny boring bar.
 
Last edited:

rzbill

The cheapest thing in an airplane is the pilot.
Active Member
Joined
Feb 16, 2017
Messages
110
Likes
123
#8
I did go to HF to get the lathe bit kit. It was bigger than I remembered but I bought them anyway. Coupon y'know. ;) Another free flashlight.
I had to hack on the boring bar to make it small enough to fit into the 1/2" starting bore in the gear. Did not have a drill any larger than 1/2" to open it up.
So I hogged it in 'counterbore' steps until I could get the bar all the way through the part. Afterwards was easy. First time cutting cast iron on a lathe. What a mess. Cleaned up often to keep the **** out of the ways.

Here is a pic of the gear on the lead screw that slides through the gear. I cut the gear bore to 0.752/0.753" since the shaft measures 0.750. Nice sliding fit.


Gear Bore.jpg

Next is the keyway. I struck out trying to find 1/4" wide lathe bits in town. I have some 3/8" HSS bits. Guess I'll cut one down on the mill (yes it's still functional even partially disassembled as shown)

3 Hrs later.....The keyway is in.

Keyway.jpg

This was more of a PITA than I expected. The first part was cutting the HSS bit down to 1/4" but to be fair that is not really related to the keyway cutting in itself. Carbide cutter and sulphur cutting oil was the best I had but the mill did not particularly care for the job. I think it needed flood cooling to keep things cool. I used time between passes.

I got the keyway cutting on the lathe figured out when I was almost done. :rolleyes: I made a number of adjustments to the cutter shape and approach angle in order to deal with 'drag' I was getting from the cutter running in the key slot. While fighting this 'drag', I learned of two areas on the lathe that will get modified in the future. One is a hex head bolt on the carriage that nicked my knuckles frequently and second is the casting joint between the carriage and apron, Its a mismatch that also liked to bite my fingers while using the handwheel in a forceful manner.

Sunday I'll work on the key retainer screw (got that done) and the gear retainer washer (Ran out of time). I'd like to get this done but I have to head for the airport for a business trip in the afternoon. Might finish this next weekend.

I'm out 'til next weekend.
 
Last edited:

rzbill

The cheapest thing in an airplane is the pilot.
Active Member
Joined
Feb 16, 2017
Messages
110
Likes
123
#9
FINISHED. Worked in the shop Sunday.
Made a 1/8" washer with a pair of mounting holes. Drilled and tapped same holes in the gear. Drilled new holes in the brass retainer washer because I did not like the original locations (the threads broke out the side of the boss on the gear).

X Drive Gear Assy.jpg

Below is the worm carriage partially reassembled. I have been making washers out of some teflon sheet that I have in the scrap bin. You can see a couple here. Basically applying them where the original design of this mill (and the Atlas Lathe) had steel on steel.

X Worm Assy.jpg

The following are 3 pictures of the drive system reassembled onto the mill. Some were details for Pineyfolks.

X Drive Assy 1.jpg X Drive Assy 2.jpg X Drive Assy 3.jpg

While contemplating the reassembly, I decided to remove the X- Screw and table just to clean it up. It had been 10 years since the last time (right after I bought the mill). I did make an original mistake of using a way too sticky and viscous lube. This mistake probably influenced the wear rate of the drive gear. Time to clean it out and go with light oil like the lathe.
Here are pics of that just for posterity.

X Saddle.jpg
Below is the gib. Steel. Gib screws 1 ,3 and 5 have copper bullet with angle tip.
Gib screws 2 and 4 are sharp pointed tips that have left a point impression on the gib. This is the only thing that keeps the gib from sliding out.

X Gib.jpg

Table dovetails below

X Table.jpg

ACME Nut. Brass. 3/4" Dia. 8 TPI. Right Hand. You can see a saw slot in it. I may have done that the last disassembly. I squeezed the nut a little in the vice. The nut has a 5/8" dia boss that is 3/8" long on the bottom of the casting. The ACME thread centerline appears to be 1/2" above the base of the nut.

X ACME Nut.jpg

Lastly, each end of the Acme screw has ball thrust bearings and the indicators and wheels. Ball thrust bearings need to be adjusted as a "pair" in order to minimize "end play" on the screw. Below is a pic of the right hand side assy (non-drive end). Starting at the left: Cast housing, thrust bearing race, bearing cage, race, dial bushing, dial (rides on the bushing so it is not affected by screw thrust), key, wheel and nut.

X Screw End Bearing Assy.jpg

All is working again. Hope this info helps other ROTEX owners. Take care. :)
 

rzbill

The cheapest thing in an airplane is the pilot.
Active Member
Joined
Feb 16, 2017
Messages
110
Likes
123
#10
Just finishing this thread off with a couple of snapshots of my Rotex RM-1 with Rusnok 70 head. Can't really find another place that is appropriate to put these pics. No cosmetic work and really very little repair since purchased. Only the one covered in this thread and a simple bearing replacement on the Rusnok some years ago. It was a good $400 investment. :)

20171120_174829.jpg
20171120_174855.jpg
 
Container Above bottom breadcrumb