VansAirForceForums  
Home > VansAirForceForums

-POSTING RULES
-Advertise in here!
- Today's Posts | Insert Pics

Keep VAF Going
Donate methods

Point your
camera app here
to donate fast.

  #1  
Old 05-25-2014, 12:31 PM
Loman Loman is offline
 
Join Date: Feb 2008
Location: Dublin, Ireland
Posts: 180
Default Baffle mounting screw broken

About two years ago, I bought a nice O-320 with 174 hours since total overhaul for my project. I saw the engine run before it was taken off the donor aircraft but I never noticed that one of the baffle mounting screws was broken off. It's the one forward of the No.3 cylinder. When i finally noticed the problem I was pretty confident that I could get it out but the job has gone wrong.

I was drilling out the core of the screw with a #40 bit in preparation for using a screw extraction tool when the tip of the bit broke off in the body of the screw. It broke off cleanly so there was nothing to grab. I used every tool I had today and got nowhere. The steel in the tip of the bit is just too tough for anything I have available.

These holes run through to the first gap between the fins so there is no way of getting at the back of the screw.



One idea I had is simply to leave the broken screw where it is and drill / tap a new hole lower down in the same boss. there is plenty of space there. However, I would obviously prefer to get the broken screw out

All ideas gratefully received.
__________________
Loman O'Byrne
RV9 TU. O-320-E2D. Engine hung, working on FWF, Arklow, Ireland
=VAF= dues paid through Dec 2021
Reply With Quote
  #2  
Old 05-25-2014, 12:42 PM
flightlogic's Avatar
flightlogic flightlogic is offline
 
Join Date: Nov 2013
Location: Prescott, AZ
Posts: 1,674
Default

Might be tempted to drill lower as you noted. The steel you are trying to remove is going to be a challenge. An EZ out works... but not after the screw breaks off. Is that Gorilla Glue on there also?
If it is #3... you might want to read the recent thread about washers and other mods to the baffle in that region for cooling that particular cylinder. I am about to mod mine... so your close up photo brought it to mind.
Sorry you have had the misfortune of snapping the screw off. I am sure there are endless stories among builders who have cursed that same situation many times.

Last edited by flightlogic : 05-25-2014 at 12:43 PM. Reason: spelling
Reply With Quote
  #3  
Old 05-25-2014, 12:56 PM
BillL BillL is offline
 
Join Date: Sep 2007
Location: Central IL
Posts: 6,322
Default

Well, that just sucks. There is little chance that the screw is going to be removed with a screw exctractor. The first question is why the #40 broke. Was it deep and did it break through and snag? If so you "may" have some luck with a center punch, but if that is a blind hole, it will only provide some relief.

if the head is on the plane then a carbide blade bit, or a very small carbide burr on a high speed grinder (dremel) might be able to drill through. If it is off the plane and can be set vertical, nitric acid will dissolve the bit and not harm the aluminum.

Finally, after you get the bit out and screw, your best bet is a heli-coil insert for the final touch. Re-drilling a hole nearby is a very risky proposition. I have done dozens of these on VW's and salty outboard motor blocks.
__________________
Bill

RV-7
Reply With Quote
  #4  
Old 05-25-2014, 05:37 PM
KiloWhiskey1's Avatar
KiloWhiskey1 KiloWhiskey1 is offline
 
Join Date: Mar 2006
Location: Kennesaw, GA
Posts: 240
Default

I've had good luck with a Dremel. They make several tungsten bits that will make quick work of the broken bolt and the #40 bit. Keep it centered and bore out enough to get an extractor bit tightly in place.

The bit I used is a Dremel 9904 tungsten carbide cutter. This is a 3/32" bit. They also make the same bit in 1/8". I'd try the small one first.

Best of luck!

Keith
__________________
Keith Ward
Current: RV-10 N253RV, RV-3 N235RV, Panther build progress
Sold: RV-7 N818PA, RV-7 N818KW, RV-8 N626JL, Christen Eagle II N56RJ

Last edited by KiloWhiskey1 : 05-25-2014 at 05:39 PM.
Reply With Quote
  #5  
Old 05-25-2014, 07:18 PM
aerhed aerhed is offline
 
Join Date: Dec 2008
Location: Big Sandy, WY
Posts: 2,567
Default

Can you pull #3 and swap it with another cylinder? Sounds weird, but I bet you're already in for that much time.
__________________
Actual repeat offender.
Reply With Quote
  #6  
Old 05-25-2014, 08:37 PM
Tbone's Avatar
Tbone Tbone is offline
 
Join Date: Jan 2006
Location: South
Posts: 526
Default Weld

Take a nut a little bit larger than the shank of the bolt and place it over the broken shank area. Then take a mig welder and weld up the hole of the nut. Take a wrench and turn the offending "new" bolt out! The heat will loosen the broken stud out and if not will at least get your carbide extractor out. Take a piece of metal and tap a hole and break a bolt off and practice if you want to get a feel for it if it makes you uncomfortable but I have done it several times and it works !
__________________
___________
Terry
RV7
XP IO360
Reply With Quote
  #7  
Old 05-26-2014, 05:38 AM
molson309 molson309 is offline
 
Join Date: Jul 2009
Location: Longmont, CO
Posts: 253
Default

A method I have used in the past is to put a small carbide burr in a Dremel tool and then (very) carefully cutting a slot into the screw shank, enough to get a small straight blade screwdriver head into. Then after judiciously heating the area - aluminum expands much more than steel - using the screwdriver to back the piece out. Heat it to where it's hot to the touch but I wouldn't go much further than that. A bit of penetrating oil wouldn't hurt either.

You will need a steady hand to cut the slot - but the carbide burr will cut the hard drill steel very easily.
__________________
Mark Olson
RV-7A First flight 2005 Sold 2019
F1-EVO Rocket First flight 2010
Reply With Quote
  #8  
Old 05-26-2014, 05:54 PM
Loman Loman is offline
 
Join Date: Feb 2008
Location: Dublin, Ireland
Posts: 180
Default Great replies - thanks and some further info

Those are great responses. I am really grateful to all who contributed.

To answer the points raised:

1. There seems to be a consensus on the Dremel tungsten carbide burr so i will try that first, to be followed by an Easyout screw extractor. I don't fancy trying to cut a slot for a flat blade screwdriver. I am likely to get too close to the threads or else the only screwdriver blade that will fit in the new slot will be too small and puny to turn the screw.

2. If the Dremel burr fails, I might try the "Rescue Bit" designed for drilling out hardened steel such as drill bits, taps and Easyouts.

3. Seems like heat and penetrating oil is a good idea when I get to the stage of making the screw move with the Easyout.

4. The engine is mounted on the plane as I have been working on cowl and baffles. That makes getting the head into a vertical position quite difficult but not impossible. I am fascinated with the idea of the Nitric acid. If it comes to that, the best way of doing it would be to pull that cylinder, leaving the rest of the engine in place.

5. I am not certain what benefit swapping cylinders would be, unless replacing #3 entirely with a new one is what is being suggested. I had already decided to do the washer mod or something similar

6. There is nothing of the screw protruding. In fact it is below the surface of the hole. So I can't tig weld a new head onto it. Great idea though if there was just a little of the screw protruding.

7. How it happened? I had drilled a short hole (no more than 1/16) in the broken screw using my best small bit, which is a Dremel 2mm. I switched to a new 'jobber' #40 to continue. It is slightly bigger at about 2.4mm I was using low speed and high pressure, which I thought was the correct procedure for hard metals. The bit immediately gripped on the hole and snapped off low down. Somebody commiserated with me for breaking off the screw. That was the previous owner, not me. I just made it worse.

8. Drilling a new hole lower down is obviously a last resort and I would pull the cylinder and give it to a professional if that was the only remaining option.

Finally, I promise to report back once I have it solved, which could be soon but could also take a long time
__________________
Loman O'Byrne
RV9 TU. O-320-E2D. Engine hung, working on FWF, Arklow, Ireland
=VAF= dues paid through Dec 2021
Reply With Quote
  #9  
Old 05-26-2014, 06:13 PM
Russ McCutcheon's Avatar
Russ McCutcheon Russ McCutcheon is offline
 
Join Date: Oct 2005
Location: Vancouver, WA USA
Posts: 911
Default

Quote:
Originally Posted by Loman View Post
Those are great responses. I am really grateful to all who contributed.

To answer the points raised:

1. There seems to be a consensus on the Dremel tungsten carbide burr so i will try that first, to be followed by an Easyout screw extractor. I don't fancy trying to cut a slot for a flat blade screwdriver. I am likely to get too close to the threads or else the only screwdriver blade that will fit in the new slot will be too small and puny to turn the screw.

2. If the Dremel burr fails, I might try the "Rescue Bit" designed for drilling out hardened steel such as drill bits, taps and Easyouts.

3. Seems like heat and penetrating oil is a good idea when I get to the stage of making the screw move with the Easyout.

4. The engine is mounted on the plane as I have been working on cowl and baffles. That makes getting the head into a vertical position quite difficult but not impossible. I am fascinated with the idea of the Nitric acid. If it comes to that, the best way of doing it would be to pull that cylinder, leaving the rest of the engine in place.

5. I am not certain what benefit swapping cylinders would be, unless replacing #3 entirely with a new one is what is being suggested. I had already decided to do the washer mod or something similar

6. There is nothing of the screw protruding. In fact it is below the surface of the hole. So I can't tig weld a new head onto it. Great idea though if there was just a little of the screw protruding.

7. How it happened? I had drilled a short hole (no more than 1/16) in the broken screw using my best small bit, which is a Dremel 2mm. I switched to a new 'jobber' #40 to continue. It is slightly bigger at about 2.4mm I was using low speed and high pressure, which I thought was the correct procedure for hard metals. The bit immediately gripped on the hole and snapped off low down. Somebody commiserated with me for breaking off the screw. That was the previous owner, not me. I just made it worse.

8. Drilling a new hole lower down is obviously a last resort and I would pull the cylinder and give it to a professional if that was the only remaining option.

Finally, I promise to report back once I have it solved, which could be soon but could also take a long time
I have removed lots of these, even smaller ones that where broken off even and lower then the surface with a TIG welder, you just build it up tell you can weld a nut on or just grab it with vice grips. If only you where closer I would fix you right up.
__________________
Russ McCutcheon
@rv4welder on Facebook
russmccutcheon@gmail.com
We build many of your RV weldments.
Reply With Quote
  #10  
Old 05-26-2014, 07:02 PM
Tbone's Avatar
Tbone Tbone is offline
 
Join Date: Jan 2006
Location: South
Posts: 526
Talking TIG or MIG

I have used both on several broken off bolts. Some as much as an inch below with a stick welder. The flux will protect the the threads. About the easiest in my book if you broke a carbide off in it!
__________________
___________
Terry
RV7
XP IO360
Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -6. The time now is 12:23 PM.


The VAFForums come to you courtesy Delta Romeo, LLC. By viewing and participating in them you agree to build your plane using standardized methods and practices and to fly it safely and in accordance with the laws governing the country you are located in.