Saturday, December 26, 2015

Fixing Milling Head on my Emco Maximat V10 Metal Lathe

Project:
Fixing the way my milling head is attached to the main column and doing a general clean

Difficulty Level (Easy, Medium, Hard, Insane):
Medium

Process:
I was milling a small aluminum part, the sector head, for my Dividing Head when all of a sudden the entire milling head fell off and crashed onto the lathe ways. Instinct took over and turned off the mill and then I just stood there in awe of what just happened.

The way the Emco Milling head is designed is so that the milling head can rotate 360 degrees around a protruding metal piece (not sure what you'd call it) with about a quarter inch overhang.

After giving it some thought it was probably a design flaw, maybe even a manufacturing defect but considering that the lathe is over 40 years old (built in Austria in 1973) I'm surprised it hung on for that long (no pun intended).

After assessing the situation I came up with a few ways of fixing it. I ran my idea by the guys on the Emco Larger Lathes Forum on Yahoo and decided that I was gonna try to give the fix a go.

I decided to put the milling head in the 4-jaw chuck, face off the cracked rim, bore out the inside and thread it, then turn a piece of metal stub with an overhanging ridge at the front and a matching thread. Then use loctite to hold it all in place and that should be it.

I was really glad that I had already built the Back Plate for my 4-Jaw Chuck just a few days earlier so all I had to do is put some aluminum flashing between the part and the jaws of the chuck, dial it in and go to it.

The job ended up taking about 10 hours but most of that was because I'm still learning and everything takes a lot longer. It was actually quite a fun project and what I found most exciting is that a catastrophic failure like that would have meant the end of the tool (replacements are in the hundreds of dollars) and now I was able to fix it all for free.

Videos:

 
Pictures:
Milling the dividing head sector arm at an angle
Another view of what I was doing when the head broke off
The milling head where it landed. Luckily it didn't break anything or hurt anyone
Close-up of the cracked cast
The broken off ring still in the milling head
Another view of the broken off ring
The ring where it was before it broke off
Close-up of the broken milling head. The only place it was still attached (for who knows how long) is in the red oval
The milling head support resting on the lathe
Dimensions of the milling head support
After I faced off the cracked cast and got ready to bore out the inside to 2"
The inside bored out to 2"
I decided to use an 11 TPI internal thread
After the thread was cut
Another view of the cleaned up and threaded milling head support
Getting ready to turn down a 4" chunk of 10V45 (I didn't have any 2-3/4" stock) to 2.675"
Almost there
Doing a scratch pass with 11 TPI male thread
The rough finished part
Locking it in place with permanent (red) loctite
Supporting the head with a dead center so as to give better accessibility and turning it down to final size
Another view from a bit further away
Another angle
Close-up of the rough turned lip
Using a parting tool to finish the part to size and make it 100% concentric
Close-up of the finished job
Another view
Cleaning out the 20-30 year old stuff that was stuck behind the milling head column support bracket
Milling head was made in 1971
Taking the milling head column and cleaning it all up with some sand paper
Another "Before" view of the milling head column
After it was all nice and shiny
Another view of the polished milling head column
All the parts cleaned and shined up
Another view
Close-up of the top of the cleaned milling head column
The fixed milling head support reinstalled
Another view
Close-up of the fixed part
Side view of the fixed milling head support
The milling head back where it belongs
Another view
Tools:
Lathe & accessories
Thread gage
Bench top grinder
Angle grinder
Goggles
Ear muffs
Digital calipers
Marker
Cordless drill
Adjustable wrench
Screwdrivers

Materials:
1" of 4" diameter 10V45
Red loctite
WD40
General purpose oil

Cost:
$0.00

Time:
10 hrs

Savings:
Hundreds of dollars for sure

Conclusion:
Success. I hope it will never ever do that again!

6 comments:

Unknown said...

WOW!

Anonymous said...

Great repair Chris, better than the original.
All the best jb

Anonymous said...

Epic fix. My v10p head and column fell over once when I moved. the worst of it was a broken scroll lock quick release. Hopefully I never EVER have to do this. You were very lucky that it failed like it did, instead of obliquely through the entire main casting.

Michael Eakin said...

Well, I didn't break the v10p head, but I bent the $#!+ out of one mounting bolt and sheared the other. Your fix looks great!

Would you know what material I would use for fabricate some mounting bolts? like 4140 steel? or some other steel that's machinable and would hold up to mounting stresses? Would I need to harden and temper them, or would they be good enough right off the lathe??

Love your blog! Thanks!!!

Chris Eigenheer said...

Michael, 4140 is good stuff and I don't think you'd have to heat treat it. If you do, however, make sure that you temper it back to a straw yellow color or else the bolts are just gonna snap again. You could use some O1 (as in the letter "o" and the number "1") tool steel, heat it to a cherry red, oil quench it and then temper it to a straw yellow. That would certainly be about the strongest way to do it, but if you used untreated 4140 it would be somewhere between a grade 5 and a grade 8 bolt. I'd say that'd be enough for the mill head. let me know what you end up doing; I'd love to hear back.

Anonymous said...

Bolts on mine came in one-bent-one-almost-broken configuration when I bought the machine. For now I machined the replacements from grade 12.9 metric M14x80mm bolts/screws. I have no idea if that will hold, but it's the toughest metric screw grade I know of. Originals seem a bit softer under the file, but that doesn't mean anything. Time will tell.

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