Re: Bolt Removal Problems
Caroline wrote:
> > "Eric" <say.no@spam.now> wrote > > Caroline wrote: > > > > > > The head on the lower mounting bolt of my 91 Civic's rear left shock > > > absorber sheared off. > > > > To clarify, do you mean the bolt that goes through bushing #20 in this > > diagram http://tinyurl.com/3n3up ? > > Yes. The bolt itself appears in the "rear shock absorber" drawing at > http://tinyurl.com/59d5k (item #20). > > > > Same for the bolt joining the control arm to the trailing arm. > > > > That sounds like bolt #25 at the trailing arm in the above diagram, > > correct? > > Correct. > > I anticipate the same problem with *both* #25 bolts in this drawing. So > far, only the outboard bolt's head is sheared off. > > If I want to replace the spring-over-shock absorber assembly, at least > one of those #25 bolts must come free, and in a way that doesn't damage > the lower arm (= trailing arm) or its bushing or the other #25 bolt's > female fitting. > > I'm not in any trouble per se (yet). The car is still drivable. This, as > is usually the case lately with my car work, is more about the journey > (and maybe overkill pre-emptive maintenance) than the destination. I may be mistaken, but it sounds to me like you may have been bitten by the same problem that attacks the front suspension lower mounting bolt. That is, it seems that Honda did not use any antiseize compound on these bolts and they tend to rust up in the bushing. You may have success by twisting off the captive nut on the back side of the strut yoke as others have suggested. However, if the bolt is truly seized up in the bushing, then it may require you to get a new bushing pressed into the control arm. It seems unlikely that the small captive nut could provide enough clamping force on the bolt to allow the head to be twisted off. It seems more likely that the bolt shank is frozen up in the bushing. However, you may get lucky pounding it out. The trailing arm bolt is likely to more of a hassle. Here again, it may be the case that the bolt is rusted into the metal sleeve of the bushing. You could try drilling the end of the bolt where the head broke off so that you can then insert a spiral screw extractor into it (always use a center punch when drilling a bolt to get your drill started correctly). You'll likely need a right angle drill due to the close quarters. If you can get a screw extractor into it, then you might have luck by applying some gentle heat to the captive nut on the far side. The other posters are correct in that a mapp gas torch will be better than a propane torch as they burn hotter. Heat the nut up until it just begins to turn red and then try loosening the bolt (be careful of any fuel lines or brake lines in the neighborhood). However, if the bolt shank is truly rusted up in the bushing, then this process may not get you anywhere. If that's the case, then you may be able to get a rotary cut off tool between the bushing and the trailing arm to cut the bolt at both ends of the bushing. If you follow this procedure, you'll need to get a new bushing pressed into the control arm so don't worry about cutting it and keep your cut off tool away from the trailing arm. Note that you'll still need to drill out the remaining bolt in the trailing arm or find some way of removing the captive nut and replacing it with something else. Good luck. Another possibility is that you may have success by whacking the bolts with an air hammer once you get the captive nuts removed. Unfortunately, this might mushroom the end of the bolt and make drilling it much more difficult if you wish to try that avenue later. By the way, be sure to put some antiseize compound on any of the bolts that you reinstall back into the suspension. I happen to be biased towards the copper based antiseize but the other type (zinc based I think) should work as well. Note that with the bushings, the antiseize should go on the bolt shank as well as on the threads. Eric |
Re: Bolt Removal Problems
Caroline wrote:
> > "Eric" <say.no@spam.now> wrote > > Caroline wrote: > > > > > > The head on the lower mounting bolt of my 91 Civic's rear left shock > > > absorber sheared off. > > > > To clarify, do you mean the bolt that goes through bushing #20 in this > > diagram http://tinyurl.com/3n3up ? > > Yes. The bolt itself appears in the "rear shock absorber" drawing at > http://tinyurl.com/59d5k (item #20). > > > > Same for the bolt joining the control arm to the trailing arm. > > > > That sounds like bolt #25 at the trailing arm in the above diagram, > > correct? > > Correct. > > I anticipate the same problem with *both* #25 bolts in this drawing. So > far, only the outboard bolt's head is sheared off. > > If I want to replace the spring-over-shock absorber assembly, at least > one of those #25 bolts must come free, and in a way that doesn't damage > the lower arm (= trailing arm) or its bushing or the other #25 bolt's > female fitting. > > I'm not in any trouble per se (yet). The car is still drivable. This, as > is usually the case lately with my car work, is more about the journey > (and maybe overkill pre-emptive maintenance) than the destination. I may be mistaken, but it sounds to me like you may have been bitten by the same problem that attacks the front suspension lower mounting bolt. That is, it seems that Honda did not use any antiseize compound on these bolts and they tend to rust up in the bushing. You may have success by twisting off the captive nut on the back side of the strut yoke as others have suggested. However, if the bolt is truly seized up in the bushing, then it may require you to get a new bushing pressed into the control arm. It seems unlikely that the small captive nut could provide enough clamping force on the bolt to allow the head to be twisted off. It seems more likely that the bolt shank is frozen up in the bushing. However, you may get lucky pounding it out. The trailing arm bolt is likely to more of a hassle. Here again, it may be the case that the bolt is rusted into the metal sleeve of the bushing. You could try drilling the end of the bolt where the head broke off so that you can then insert a spiral screw extractor into it (always use a center punch when drilling a bolt to get your drill started correctly). You'll likely need a right angle drill due to the close quarters. If you can get a screw extractor into it, then you might have luck by applying some gentle heat to the captive nut on the far side. The other posters are correct in that a mapp gas torch will be better than a propane torch as they burn hotter. Heat the nut up until it just begins to turn red and then try loosening the bolt (be careful of any fuel lines or brake lines in the neighborhood). However, if the bolt shank is truly rusted up in the bushing, then this process may not get you anywhere. If that's the case, then you may be able to get a rotary cut off tool between the bushing and the trailing arm to cut the bolt at both ends of the bushing. If you follow this procedure, you'll need to get a new bushing pressed into the control arm so don't worry about cutting it and keep your cut off tool away from the trailing arm. Note that you'll still need to drill out the remaining bolt in the trailing arm or find some way of removing the captive nut and replacing it with something else. Good luck. Another possibility is that you may have success by whacking the bolts with an air hammer once you get the captive nuts removed. Unfortunately, this might mushroom the end of the bolt and make drilling it much more difficult if you wish to try that avenue later. By the way, be sure to put some antiseize compound on any of the bolts that you reinstall back into the suspension. I happen to be biased towards the copper based antiseize but the other type (zinc based I think) should work as well. Note that with the bushings, the antiseize should go on the bolt shank as well as on the threads. Eric |
Re: Bolt Removal Problems
"Eric" <say.no@spam.now> wrote
> Caroline wrote: > > > > "Eric" <say.no@spam.now> wrote > > > Caroline wrote: > > > > > > > > The head on the lower mounting bolt of my 91 Civic's rear left shock > > > > absorber sheared off. > > > > > > To clarify, do you mean the bolt that goes through bushing #20 in this > > > diagram http://tinyurl.com/3n3up ? > > > > Yes. The bolt itself appears in the "rear shock absorber" drawing at > > http://tinyurl.com/59d5k (item #20). > > > > > > Same for the bolt joining the control arm to the trailing arm. > > > > > > That sounds like bolt #25 at the trailing arm in the above diagram, > > > correct? > > > > Correct. > > > > I anticipate the same problem with *both* #25 bolts in this drawing. So > > far, only the outboard bolt's head is sheared off. > > > > If I want to replace the spring-over-shock absorber assembly, at least > > one of those #25 bolts must come free, and in a way that doesn't damage > > the lower arm (= trailing arm) or its bushing or the other #25 bolt's > > female fitting. > > > > I'm not in any trouble per se (yet). The car is still drivable. This, as > > is usually the case lately with my car work, is more about the journey > > (and maybe overkill pre-emptive maintenance) than the destination. > > I may be mistaken, but it sounds to me like you may have been bitten by the > same problem that attacks the front suspension lower mounting bolt. That > is, it seems that Honda did not use any antiseize compound on these bolts > and they tend to rust up in the bushing. You may have success by twisting > off the captive nut on the back side of the strut yoke as others have > suggested. However, if the bolt is truly seized up in the bushing, then it > may require you to get a new bushing pressed into the control arm. It seems > unlikely that the small captive nut could provide enough clamping force on > the bolt to allow the head to be twisted off. It seems more likely that the > bolt shank is frozen up in the bushing. Based on my efforts today, you are correct. Today I was stuck workingmostly on the rear outboard lower control arm bolt. I ground it down with a hand drill grinding block. I then successfully drilled the distance of its nut (or threaded female end; there's really no nut there that I can see), starting with a cobalt 1/6" bit, then 1/8" bit, then another size up, per the screw extractor table. I used Sears' cutting oil. I tried some screw extractors with the cutting oil for a few hours but did not want to break any and so finally gave up on it to ponder this overnight. I then gave the inboard #25 bolt a try. I'd sprayed it a couple times with PB Blaster since this morning. Hurrah! It came out pretty easily for a 13-year-old, never been changed before, seen northern U.S. winters bolt. I thought, "Great. I should be able to get the middle control arm bolt off and at least change out the strut assembly today." Wrong. What you described above is dead-on correct. I snapped off the (middle)welded nut with a 1/2-inch drive 19 mm socket and a five-foot breaker bar. It wasn't as dramatic as the crankshaft bolt but it came close. I then tried pounding the bolt through the bushing, which didn't work. I then tried double-nutting the forward, threaded end. I quickly found the whole bushing was trying to turn as I turned the bolt! As you suggested, the bushing is frozen to the splines of the bolt big time. I'd likely end up destroying the bushing if I force the bolt out. > However, you may get lucky pounding > it out. Yes. Luck. It was at a mininum today. > The trailing arm bolt is likely to more of a hassle. Here again, it may be > the case that the bolt is rusted into the metal sleeve of the bushing. You > could try drilling the end of the bolt where the head broke off so that you > can then insert a spiral screw extractor into it (always use a center punch > when drilling a bolt to get your drill started correctly). You'll likely > need a right angle drill due to the close quarters. If you can get a screw > extractor into it, then you might have luck by applying some gentle heat to > the captive nut on the far side. The other posters are correct in that a > mapp gas torch will be better than a propane torch as they burn hotter. > Heat the nut up until it just begins to turn red and then try loosening the > bolt (be careful of any fuel lines or brake lines in the neighborhood). > However, if the bolt shank is truly rusted up in the bushing, then this > process may not get you anywhere. If that's the case, then you may be able > to get a rotary cut off tool between the bushing and the trailing arm to cut > the bolt at both ends of the bushing. If you follow this procedure, you'll > need to get a new bushing pressed into the control arm so don't worry about > cutting it and keep your cut off tool away from the trailing arm. Note that > you'll still need to drill out the remaining bolt in the trailing arm or > find some way of removing the captive nut and replacing it with something > else. Good luck. Yes, this is where I'm at. Given what I'm seeing with the middle bolt, I think the screw extractors will just keep breaking. I think I'm going to put everything back together tomorrow, antiseizing the inboard bolt like mad, of course, and give this a week to ponder. It seems to me I am going to have to cut the bushings of the outboard bolt, then extract, piece-by-piece, the remaining bolt, along the lines of what you suggest. Probably have to tap the female threaded fitting on it. Tapping looks very do-able right now, due to my fine drilling job. I think. > Another possibility is that you may have success by whacking the bolts with > an air hammer once you get the captive nuts removed. Unfortunately, this > might mushroom the end of the bolt and make drilling it much more difficult > if you wish to try that avenue later. > > By the way, be sure to put some antiseize compound on any of the bolts that > you reinstall back into the suspension. Do I read like the guys who put this car together?! ;-) > I happen to be biased towards the > copper based antiseize but the other type (zinc based I think) should work > as well. Note that with the bushings, the antiseize should go on the bolt > shank as well as on the threads. Yes, indeedy. (I draw from my ship experience here.) :-) Seriously, thank you for your help. It seems to me the key to this endeavor is realizing it's the bushing, not the nut, freezing to the bolt. For it's whole length. |
Re: Bolt Removal Problems
"Eric" <say.no@spam.now> wrote
> Caroline wrote: > > > > "Eric" <say.no@spam.now> wrote > > > Caroline wrote: > > > > > > > > The head on the lower mounting bolt of my 91 Civic's rear left shock > > > > absorber sheared off. > > > > > > To clarify, do you mean the bolt that goes through bushing #20 in this > > > diagram http://tinyurl.com/3n3up ? > > > > Yes. The bolt itself appears in the "rear shock absorber" drawing at > > http://tinyurl.com/59d5k (item #20). > > > > > > Same for the bolt joining the control arm to the trailing arm. > > > > > > That sounds like bolt #25 at the trailing arm in the above diagram, > > > correct? > > > > Correct. > > > > I anticipate the same problem with *both* #25 bolts in this drawing. So > > far, only the outboard bolt's head is sheared off. > > > > If I want to replace the spring-over-shock absorber assembly, at least > > one of those #25 bolts must come free, and in a way that doesn't damage > > the lower arm (= trailing arm) or its bushing or the other #25 bolt's > > female fitting. > > > > I'm not in any trouble per se (yet). The car is still drivable. This, as > > is usually the case lately with my car work, is more about the journey > > (and maybe overkill pre-emptive maintenance) than the destination. > > I may be mistaken, but it sounds to me like you may have been bitten by the > same problem that attacks the front suspension lower mounting bolt. That > is, it seems that Honda did not use any antiseize compound on these bolts > and they tend to rust up in the bushing. You may have success by twisting > off the captive nut on the back side of the strut yoke as others have > suggested. However, if the bolt is truly seized up in the bushing, then it > may require you to get a new bushing pressed into the control arm. It seems > unlikely that the small captive nut could provide enough clamping force on > the bolt to allow the head to be twisted off. It seems more likely that the > bolt shank is frozen up in the bushing. Based on my efforts today, you are correct. Today I was stuck workingmostly on the rear outboard lower control arm bolt. I ground it down with a hand drill grinding block. I then successfully drilled the distance of its nut (or threaded female end; there's really no nut there that I can see), starting with a cobalt 1/6" bit, then 1/8" bit, then another size up, per the screw extractor table. I used Sears' cutting oil. I tried some screw extractors with the cutting oil for a few hours but did not want to break any and so finally gave up on it to ponder this overnight. I then gave the inboard #25 bolt a try. I'd sprayed it a couple times with PB Blaster since this morning. Hurrah! It came out pretty easily for a 13-year-old, never been changed before, seen northern U.S. winters bolt. I thought, "Great. I should be able to get the middle control arm bolt off and at least change out the strut assembly today." Wrong. What you described above is dead-on correct. I snapped off the (middle)welded nut with a 1/2-inch drive 19 mm socket and a five-foot breaker bar. It wasn't as dramatic as the crankshaft bolt but it came close. I then tried pounding the bolt through the bushing, which didn't work. I then tried double-nutting the forward, threaded end. I quickly found the whole bushing was trying to turn as I turned the bolt! As you suggested, the bushing is frozen to the splines of the bolt big time. I'd likely end up destroying the bushing if I force the bolt out. > However, you may get lucky pounding > it out. Yes. Luck. It was at a mininum today. > The trailing arm bolt is likely to more of a hassle. Here again, it may be > the case that the bolt is rusted into the metal sleeve of the bushing. You > could try drilling the end of the bolt where the head broke off so that you > can then insert a spiral screw extractor into it (always use a center punch > when drilling a bolt to get your drill started correctly). You'll likely > need a right angle drill due to the close quarters. If you can get a screw > extractor into it, then you might have luck by applying some gentle heat to > the captive nut on the far side. The other posters are correct in that a > mapp gas torch will be better than a propane torch as they burn hotter. > Heat the nut up until it just begins to turn red and then try loosening the > bolt (be careful of any fuel lines or brake lines in the neighborhood). > However, if the bolt shank is truly rusted up in the bushing, then this > process may not get you anywhere. If that's the case, then you may be able > to get a rotary cut off tool between the bushing and the trailing arm to cut > the bolt at both ends of the bushing. If you follow this procedure, you'll > need to get a new bushing pressed into the control arm so don't worry about > cutting it and keep your cut off tool away from the trailing arm. Note that > you'll still need to drill out the remaining bolt in the trailing arm or > find some way of removing the captive nut and replacing it with something > else. Good luck. Yes, this is where I'm at. Given what I'm seeing with the middle bolt, I think the screw extractors will just keep breaking. I think I'm going to put everything back together tomorrow, antiseizing the inboard bolt like mad, of course, and give this a week to ponder. It seems to me I am going to have to cut the bushings of the outboard bolt, then extract, piece-by-piece, the remaining bolt, along the lines of what you suggest. Probably have to tap the female threaded fitting on it. Tapping looks very do-able right now, due to my fine drilling job. I think. > Another possibility is that you may have success by whacking the bolts with > an air hammer once you get the captive nuts removed. Unfortunately, this > might mushroom the end of the bolt and make drilling it much more difficult > if you wish to try that avenue later. > > By the way, be sure to put some antiseize compound on any of the bolts that > you reinstall back into the suspension. Do I read like the guys who put this car together?! ;-) > I happen to be biased towards the > copper based antiseize but the other type (zinc based I think) should work > as well. Note that with the bushings, the antiseize should go on the bolt > shank as well as on the threads. Yes, indeedy. (I draw from my ship experience here.) :-) Seriously, thank you for your help. It seems to me the key to this endeavor is realizing it's the bushing, not the nut, freezing to the bolt. For it's whole length. |
Re: Bolt Removal Problems
Update:
Unfastening the bolt connecting the rear lower control arm and trailing arm was as ugly as others in the archives reported. I never actually got it free from the bushing or its nut. I never tried a torch, but that would be my next suggestion. I eventually drilled and cut (by hand) the outside-most control arm bushing/bolt. Then I ground down the female bolt receptacle (it's not actually a nut, unfortunately, or I would have snapped it off, the way I did with the strut fork bolt) welded to the trailing arm. I used a cheap-o electric hand drill and grinding stone attachment. Grinding it down was no fun but at least I could see some kind of steady progress. Cobalt drill bits are essential but still very, very slow, even with the best cutting oil. I installed the "new" (= 8k miles used) control arm last night, attaching it with a separate nut at the trailing arm, as I think Eric and/or others suggested. The new strut and control arm did not fix the tilt, but I wasn't expecting it too. The ride seems a bit smoother, but I may have talked myself into this. I took apart the old strut in my suspension course today, borrowing the school's spring compressor. The shock absorber seemed in excellent shape at 157k miles old. The spring is a tougher call. I reckon I spent around $35 just on cutting tools for this job. About half the tools are broken or now severely worn. I'm worn, too! :-) I am contemplating doing the other side but not for another week or so. Meanwhile, the other side's bolts get sprayed with PB Blaster regularly. Not that I have much hope this will help. Moral of the story: The classic, "If it ain't broke, don't fix it"? I dunno. I learned a lot: -) |
Re: Bolt Removal Problems
Update:
Unfastening the bolt connecting the rear lower control arm and trailing arm was as ugly as others in the archives reported. I never actually got it free from the bushing or its nut. I never tried a torch, but that would be my next suggestion. I eventually drilled and cut (by hand) the outside-most control arm bushing/bolt. Then I ground down the female bolt receptacle (it's not actually a nut, unfortunately, or I would have snapped it off, the way I did with the strut fork bolt) welded to the trailing arm. I used a cheap-o electric hand drill and grinding stone attachment. Grinding it down was no fun but at least I could see some kind of steady progress. Cobalt drill bits are essential but still very, very slow, even with the best cutting oil. I installed the "new" (= 8k miles used) control arm last night, attaching it with a separate nut at the trailing arm, as I think Eric and/or others suggested. The new strut and control arm did not fix the tilt, but I wasn't expecting it too. The ride seems a bit smoother, but I may have talked myself into this. I took apart the old strut in my suspension course today, borrowing the school's spring compressor. The shock absorber seemed in excellent shape at 157k miles old. The spring is a tougher call. I reckon I spent around $35 just on cutting tools for this job. About half the tools are broken or now severely worn. I'm worn, too! :-) I am contemplating doing the other side but not for another week or so. Meanwhile, the other side's bolts get sprayed with PB Blaster regularly. Not that I have much hope this will help. Moral of the story: The classic, "If it ain't broke, don't fix it"? I dunno. I learned a lot: -) |
Re: Bolt Removal Problems
On Thu, 23 Sep 2004 22:28:53 GMT, "Caroline"
<caroline10027remove@earthlink.net> wrote: > I used a cheap-o electric hand drill and >grinding stone attachment. Grinding it down was no fun I bet! Is there any chance you can get ahold of an air tool? A die grinder with a 3" abrasive cutoff wheel is the weapon of choice. Electric drills just don't turn fast enough. |
Re: Bolt Removal Problems
On Thu, 23 Sep 2004 22:28:53 GMT, "Caroline"
<caroline10027remove@earthlink.net> wrote: > I used a cheap-o electric hand drill and >grinding stone attachment. Grinding it down was no fun I bet! Is there any chance you can get ahold of an air tool? A die grinder with a 3" abrasive cutoff wheel is the weapon of choice. Electric drills just don't turn fast enough. |
Re: Bolt Removal Problems
"John Ings" <nodamned@spam.org> wrote
> On Thu, 23 Sep 2004 22:28:53 GMT, "Caroline" > <caroline10027remove@earthlink.net> wrote: > > > I used a cheap-o electric hand drill and > >grinding stone attachment. Grinding it down was no fun > > I bet! Is there any chance you can get ahold of an air tool? > A die grinder with a 3" abrasive cutoff wheel is the weapon of choice. > Electric drills just don't turn fast enough. Hi John, thanks for the suggestion. I'm a little overbudget on "tool toys" right now, but I'll make some inquiries of classmates in my auto course and ponder it for a few weeks before I go seriously after the other rear shock assembly, if I go after it. I also want to keep an eye on my "re-design" of the one rear trailing arm/control arm linkage for awhile. At least I am now the proud owner of a 115 psi, 8 gallon reservoir, "uses oil" air compressor (which may or may not do the trick for this tool you suggest). |
Re: Bolt Removal Problems
"John Ings" <nodamned@spam.org> wrote
> On Thu, 23 Sep 2004 22:28:53 GMT, "Caroline" > <caroline10027remove@earthlink.net> wrote: > > > I used a cheap-o electric hand drill and > >grinding stone attachment. Grinding it down was no fun > > I bet! Is there any chance you can get ahold of an air tool? > A die grinder with a 3" abrasive cutoff wheel is the weapon of choice. > Electric drills just don't turn fast enough. Hi John, thanks for the suggestion. I'm a little overbudget on "tool toys" right now, but I'll make some inquiries of classmates in my auto course and ponder it for a few weeks before I go seriously after the other rear shock assembly, if I go after it. I also want to keep an eye on my "re-design" of the one rear trailing arm/control arm linkage for awhile. At least I am now the proud owner of a 115 psi, 8 gallon reservoir, "uses oil" air compressor (which may or may not do the trick for this tool you suggest). |
Re: Bolt Removal Problems
On Fri, 24 Sep 2004 05:25:35 GMT, "Caroline"
<caroline10027remove@earthlink.net> wrote: >At least I am now the proud owner of a 115 psi, 8 gallon reservoir, "uses oil" >air compressor (which may or may not do the trick for this tool you suggest). Then get a die grinder with a cutoff wheel. They're relatively cheap as air tools go. Get one without a guard or with a removable guard. They are more dangerous to use, but often you just can't get the ones with a guard into confined spaces. Small compressors sometimes don't pack enough oomph for big air tools like 3/4" impact wrenches, but they are plenty good enough for things like a die grinder, air chisels, air ratchets etc. I worked on cars for a long time before I discovered air tools, and when I did wished I had found out about them earlier. |
Re: Bolt Removal Problems
On Fri, 24 Sep 2004 05:25:35 GMT, "Caroline"
<caroline10027remove@earthlink.net> wrote: >At least I am now the proud owner of a 115 psi, 8 gallon reservoir, "uses oil" >air compressor (which may or may not do the trick for this tool you suggest). Then get a die grinder with a cutoff wheel. They're relatively cheap as air tools go. Get one without a guard or with a removable guard. They are more dangerous to use, but often you just can't get the ones with a guard into confined spaces. Small compressors sometimes don't pack enough oomph for big air tools like 3/4" impact wrenches, but they are plenty good enough for things like a die grinder, air chisels, air ratchets etc. I worked on cars for a long time before I discovered air tools, and when I did wished I had found out about them earlier. |
Re: Bolt Removal Problems
Caroline wrote:
[snip] > Cobalt drill bits are essential but still very, very slow, even with > the best cutting oil. This is by design. Cobalt bits are made for drilling into hardened metals. As such, the angle of the cutting edges is shallower than it is on high speed steel bits. This enables the drill bit to take off smaller chips of metal which has advantages when drilling into hardened metal. A disadvantage with cobalt bits is that they're typically rather brittle and easy to break. I've broken large bits simply by accidentally dropping them onto concrete. I've also broken smaller ones by applying too much side pressure while drilling. Eric |
Re: Bolt Removal Problems
Caroline wrote:
[snip] > Cobalt drill bits are essential but still very, very slow, even with > the best cutting oil. This is by design. Cobalt bits are made for drilling into hardened metals. As such, the angle of the cutting edges is shallower than it is on high speed steel bits. This enables the drill bit to take off smaller chips of metal which has advantages when drilling into hardened metal. A disadvantage with cobalt bits is that they're typically rather brittle and easy to break. I've broken large bits simply by accidentally dropping them onto concrete. I've also broken smaller ones by applying too much side pressure while drilling. Eric |
Re: Bolt Removal Problems
Caroline wrote:
[snip] > Cobalt drill bits are essential but still very, very slow, even with > the best cutting oil. This is by design. Cobalt bits are made for drilling into hardened metals. As such, the angle of the cutting edges is shallower than it is on high speed steel bits. This enables the drill bit to take off smaller chips of metal which has advantages when drilling into hardened metal. A disadvantage with cobalt bits is that they're typically rather brittle and easy to break. I've broken large bits simply by accidentally dropping them onto concrete. I've also broken smaller ones by applying too much side pressure while drilling. Eric |
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