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My D6D

Glum

Active Member
Joined
Feb 15, 2017
Messages
35
Location
South Africa
I'd certainly be inclined towards glueing that roller back into place with some low hydrogen rod until the track frame really needs to come off. Ten years ago, quite the opposite, blade off, split track, track frame off, do what was needed and back up and running same day.
 

.RC.

Senior Member
Joined
Nov 27, 2012
Messages
1,154
Location
Central Qld, Australia
Well it is going to have to be track frame off. Tried getting another two out by welding, but they are simply snapped off too far below the surface. close to 3/8". I am hopeless with an oxy and would just do more damage. So I ordered some 9S 6326 thread repair inserts. I have never used them, but I heard they are among the best style thread repairs to use. I will do it properly and be done with it. I cannot work for long on my back upside down anyway, get nauseous pretty quick.
 

.RC.

Senior Member
Joined
Nov 27, 2012
Messages
1,154
Location
Central Qld, Australia
Have not done anything yet other then some measuring. Should be able to jack the trackframe off the ground enough to fit my mag base drill under there to drill the holes out upside down.

So I made up this guide template out of 16mm plate to get the drilling and tapping done correctly. So long as the internet is correct and holes are 4.5" X 13" apart. There are various guides to fit in the holes for the different size drills I will use. A 14mm endmill to get the old bolts drilled out, then a 13/16" guide to drill the tapping hole. Then a 7/8 guide so the tap goes in straight. Plus a 5/8 guide to put a 5/8 bolt into the hole I got the broken bolt out of, to line up the other three holes.

Of course I also found out a few hundred units newer then mine they went to 3/4" bolts. So I probably could have tapped 3/4" holes there, and drilled out the roller holes.

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.RC.

Senior Member
Joined
Nov 27, 2012
Messages
1,154
Location
Central Qld, Australia
Got some time today to start on it.

But then found I forgot to put the drill in the car, but got the plate lines up and stuck on after some modifications as not sure what I was thinking when I designed it the way I did.

Then got sidetracked doing something else nearby, and that led to something else and not much else got accomplished.

Also decided to simply drill the holes out and tap them 3/4". Why waste $40 worth of thread inserts when later units they simply used 3/4" bolts from the factory. Just have to make up some guides for the 3/4 tap and tapping drill and drill out the roller holes.

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.RC.

Senior Member
Joined
Nov 27, 2012
Messages
1,154
Location
Central Qld, Australia
It an old ex-TAFE eastern bloc style milling machine made in Poland. After seeing what someone in the UK did with theirs, I found a turret milling machine someone was scrapping and bought the milling head off them, and with some minor modifications and repairs I fitted it to the milling machine to make it half useful.

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The roller job has turned into a right old pain in the bum to do. Unless the broken bolts are protruding, never try to weld them out. Looks like I have made them as hard as hell and all the drill wants to do is squeal. I have managed to get a 5mm hole though the centre of each, but that is it. Then the Kohler engine on my little Miller welder generator just wants to stop all the time, then it floods itself with a brand new genuine carburettor. I am not sure why but in my experience the US has never been able to design a small petrol motor that runs reliably. I reckon you could run a Honda under water after pulling it from a volcano. They never seem to give much trouble, but this Kohler is just rubbish, up there with Briggs and Stratton rubbish.

I should have taken Glum's advice and just welded the roller on. But no, I have to do it the right way.
 

Cliffy

Senior Member
Joined
Oct 14, 2023
Messages
466
Location
Qld
Welding broken bolts first is risky for that exact reason. Hardens the bolt and makes it almost impossible to drill after.
Vertical welding of a broken recessed bolt under a machine on the ground is probably the hardest task you can do.

My order of the bolt extraction- depending why it broke. It if broke by over torque just drill it and tap it out as it will never come out.
Wire brush bolt and any exposed thread. Use a pick to see if it will spin and clean thread.
Use hammer and gently spin the bolt with a pin punch in a circle. Most times they will move.
Drill centre. Quite often they will spin in from drilling if the hole isnt blind. I have also had luck with left handed drills just grabbing and turning out. Hit in a splined extractor (not a fan of tapered easyout) and turn it in and out gently. Don’t break it off. Heat and cool cycles will help shock it out.
Then i try to weld it out. Use a copper water pipe on frame thread so it doesn’t weld to frame and earth to the bolt if possible.
Reassemble with anti seize for the next person.
 
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.RC.

Senior Member
Joined
Nov 27, 2012
Messages
1,154
Location
Central Qld, Australia
I am crap
Welding broken bolts first is risky for that exact reason. Hardens the bolt and makes it almost impossible to drill after.
Vertical welding of a broken recessed bolt under a machine on the ground is probably the hardest task you can do.

My order of the bolt extraction- depending why it broke. It if broke by over torque just drill it and tap it out as it will never come out.
Wire brush bolt and any exposed thread. Use a pick to see if it will spin and clean thread.
Use hammer and gently spin the bolt with a pin punch in a circle. Most times they will move.
Drill centre. Quite often they will spin in from drilling if the hole isnt blind. I have also had luck with left handed drills just grabbing and turning out. Hit in a splined extractor (not a fan of tapered easyout) and turn it in and out gently. Don’t break it off. Heat and cool cycles will help shock it out.
Then i try to weld it out. Use a copper water pipe on frame thread so it doesn’t weld to frame and earth to the bolt if possible.
Reassemble with anti seize for the next person.

I do not normally have to deal with broken bolts so all this info helps.

Can you torch them out now that you‘ve got a hole through? Or are they blind holes?

I am not that crash hot with the oxy torch. I would end up doing more damage.


Anyhoo, this mornings efforts with sharp drills, and a bench grinder in case I needed to resharpen yielded results. Holes all drilled out to the tapping size. But being as Dad and Dave show, without one of them, of course my quality chinese taps are not up to scratch. Which I did only buy them years ago as thread cleaners, not thread makers.

So off to town at a later date to pick up a HSS tap of quality manufacture. However I expect only straight flute taps will be stocked when I would prefer a gun nose or spiral flute. I am off to spray some weeds.

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.RC.

Senior Member
Joined
Nov 27, 2012
Messages
1,154
Location
Central Qld, Australia
I think the moral of the story is. It is far easier to say you are going to drill and tap out those holes while upside down then it is to actually do it.

Also anyone know why these rollers have those plates fitted between the roller and frame. I have seen an old old D6C and it has the same.
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LCA078

Senior Member
Joined
Sep 29, 2019
Messages
450
Location
Austin, TX
Have you tried using carbide endmills in your mag drill instead of twist drills? Or even good HSS ones? At this point it may be a matter of maybe going crazy oversize on drilling/boring out the old bolts to get away from the hardened areas. I can't tell exactly if you're just focused on using the existing bolt holes but what about moving the roller over an inch or so and starting with fresh steel on the frame?
 
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Shimmy1

Senior Member
Joined
Aug 14, 2014
Messages
4,858
Location
North Dakota
I know I've told the story before, but I spent a solid week under a 7H about 20 years ago torching out at least half of it's roller bolts. I don't remember, probably blocked the memory, but I think they were blind holes.

I would much rather shove an ice pick in my ear than ever do that again.
 
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