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tmc_31
10-01-2015, 12:26 PM
Hey guys,

I have a set of forklift forks that I want to add a grapple to. This goes on my skid steer. I am considering drilling 3/4" holes (1 in each fork) in the center of the uprights approximately 15" up from the bottom of the forks. The forks are 1.25X4X42X2 standard forklift forks rated for 3000lb. The alloy is ASTM 15B37H. I will mount a 30"X4X4X1/2 steel angle to the front face of the forks via these holes to mount the grapple to.

My questions are:

(1) Can I drill these forks with a carbide annular cutter?

(2) How much do I need to de-rate the capacity of the forks by doing this.

I have sent the above questions to the fork manufacturer but I wanted to get you guys take on this too.

Thanks,

Tim

Bob Fisher
10-01-2015, 01:29 PM
I would hire the holes to a wire EDM facility, probably cheaper than the drill unless you already own it. My thoughts are the highest stresses on the fork are at the bend and a 3/4in hole 15 in up will have little effect on the capacity. Bob.

adatesman
10-01-2015, 02:46 PM
Insurance might think otherwise.

Toolguy
10-01-2015, 03:07 PM
You could do those holes cheap and easy with a 3/4" solid carbide drill.

Willy
10-01-2015, 03:40 PM
Rather than drilling holes in the fork tines why not design a mounting system that clamps or bolts onto the tines. This eliminates any strength or liability issues should the fecal matter ever decide to hit the fan.

If one ever decides to sell the machine holes in the forks, even in a low stress area, will not be a selling feature.

EddyCurr
10-01-2015, 03:55 PM
Rather than drilling holes in the fork tines, why not design
a mounting system that clamps or bolts onto the tines.

Yes.

For inspiration:

Courtesy AttachmentsCJJ (http://www.attachmentscjj.com/html/pallet-fork-grapple.html)

http://www.attachmentscjj.com/images/forks-pallet-grapple.png

Also: Wikco (http://www.wikco.com/336grapple.html) (image dimensions are largish)

.

tmc_31
10-01-2015, 04:07 PM
I already have an annular cutter and a mag drill in my bag of tricks.

Willy, I have a piece of 3X3X1/4 angle attached across the forks now. I attached it with a clamp system as you described. Unfortunately, the angle iron grapple mount will slip down on one fork or the other. I cannot seem to get it to clamp tight enough to stay straight. It is for this reason that I am considering drilling through the forks.

I am well aware of the liability issues guys and I don't take those lightly. That said, I refuse to let the insurance companies rule my life. I believe that people must take responsibility for their own actions.

All the best

Tim

Willy
10-01-2015, 04:34 PM
I have a piece of 3X3X1/4 angle attached across the forks now. I attached it with a clamp system as you described. Unfortunately, the angle iron grapple mount will slip down on one fork or the other. I cannot seem to get it to clamp tight enough to stay straight. It is for this reason that I am considering drilling through the forks.

Would it be possible to weld a leg onto the angle iron down to where the fork's 90 bend is, or perhaps to the top of the fork using a bend to cap the end of the fork?
This should eliminate the tendency for the angle iron to slip, No?

Bob Ford
10-01-2015, 04:34 PM
tmc_31,

Weld a piece of steel on your 3x3 angle that extends to the bend in the forks. Slip down problem solved.

tmc_31
10-01-2015, 04:41 PM
Will, Bob, both workable solutions

thank you,

Tim

Sun God
10-01-2015, 10:11 PM
Drilling a 3/4" hole in a 4 inch wide fork will increase the local stress in the fork 2.4 to 2.5 times.

Consider the existing safety factor of the fork and the loads it will be under being used on a skid steer. I for one would not perform such a significant modification to a part designed to carry suspended loads.

Boostinjdm
10-02-2015, 01:50 AM
Why are you mounting to the forks and not the carriage?

boslab
10-02-2015, 07:45 AM
We had a road sweeper thing in work you just drove up to and inserted the forks, then coupled it to the side shift on the truck, it was held on with nothing more than a chain, seemed ok
Mark

bborr01
10-02-2015, 09:40 AM
Chain it to the carriage.

Brian

kf2qd
10-02-2015, 10:10 AM
Any hole through the upright part of the forks will weaken them, and without a good analysis by a good mechanical engineer all bets are off. It might well form a source for a stress crack to start and fail that one time when you are loading something unusually heavy and valuable. And if anything were to happen, insurance would not cover you because of the modification to the forks. Better making something that mount behind or between the forks and putting a spacer that will fit between the fork carriers and prevent it from sliding.

As far as doing it on your own, that is well and good, but it is still what happens to someone else that you have to think about. And things tend to happen when someone else is about.

Richard King
10-02-2015, 10:42 AM
Years back I worked for a Used machinery dealer and his riggers had the welder burn holes in the forks for pulling things. I worked there on and off as a contractor over 20 years and never saw an issue with the holes. They also welded a chain hooks on the outside of the fork uprights to anchor a safety chain around a machine never saw a problem. I burned a hole in the dirt bucket of my Bob Cat so I could put an eye-bolt in it when pulling and lifting things, never have had an issue. I suppose the "chicken little" crowd would warn you not to do it. Today everyone is looking out for their butt from getting sued. Rich

Paul Alciatore
10-02-2015, 02:44 PM
And that analysis by a ME, if he/she is going to put his/her name on it, will cost a fortune. Verbal, without proper paperwork, is USELESS.

I like the idea of adding enough to reach the bend with no drilling. The extra metal cost is dirt cheap insurance.




Any hole through the upright part of the forks will weaken them, and without a good analysis by a good mechanical engineer all bets are off. It might well form a source for a stress crack to start and fail that one time when you are loading something unusually heavy and valuable. And if anything were to happen, insurance would not cover you because of the modification to the forks. Better making something that mount behind or between the forks and putting a spacer that will fit between the fork carriers and prevent it from sliding.

As far as doing it on your own, that is well and good, but it is still what happens to someone else that you have to think about. And things tend to happen when someone else is about.

old mart
10-02-2015, 02:46 PM
We have a Nissan forklift truck at the museum in pristine condition, donated by a kind benefactor, and when the insurance man checks the machine, he pays particular attention to the forks. Any modifications would be instantly noticed. Usually any special equipment would be fitted after the forks were removed. Drilling or welding critical components smacks of cowboy tactics.

justanengineer
10-02-2015, 04:16 PM
JMO, but I wouldn't mount it off the forks bc my luck would be to need the fork spacing to fit that odd pallet/base/etc with the grapple on the machine. Personally I'd build one thats quick-attach (be a PITA to climb over left on full time) and mounts on the top of the carriage. If your carriage has a back rack on it I'd use its mounting ears, if not add some so you can drive into it, install a couple pins and hydraulic hoses, and be ready to go.

tc429
10-02-2015, 06:14 PM
dont recall what it was for, but I made a single 'fork extension' to use for a one time thing... just a piece of channel, with a plated bottom to hold it on(plate takes full moment load applied- must be welded strong) but at the rear(open end) of the plate, added a piece of roundstock... lift the thing up, slide it on, lower it onto the fork, the roundstock 'locks' behind the radius at the bend of the fork... put some short legs on it, could probably tilt/drive in/tilt back to lock type of thing...

made up a big 'C' to hang off our boom to pull turrets off Okuma lathes- bolted bottom of C to top of turret(these things have turret on front of machine- facing inwards, spindle is motorized, moves in X-Z planes... pulling turrets to repin after a crash was difficult at best, the c-frame wrapped around roof/door, so it could simply be picked right out... we had some large Makino horizontals, spindle motor shaft slid into transmission, inside the bridgelike Y-Z column, required straight in access to swap motor...moving machine out or knocking a hole in the wall werent ideas that would fly, making a floor mounted frame /using Y/Z motion to unhook *mighta* worked, but lockout scenario was a issue...ended up welding up a 'table' for the forks, bolted on a junk set of linear rails with a plate/trucks the motor could sit on, drove the thing in, slid the table out under the motor, lifted/unhoked, slid back out... kinda a right angle telescopic fork extension.

none of this stuff can be 'rated' of course,and reality was only ~400 pounds or so needed handled, but long as tested at several times intended load, marked well with intended use/weight limits, and locked up so someone couldnt just 'use it for anything' it made jobs easier and a lot faster... like homemade bearing pressing tools that bolt onto our larger lathes and such, no way to 'rate' some of this stuff... long as used by someone that dont go kingkong on a job, should be ok... but the 'should be' part is what lawyers make a living off of too- but sometimes jobs have to be done in whatever reasonably safe way required. no job can ever be without any risk, but any 'tool' made or modified will have its maker tied to it forever, even if some stoned crackhead tried to lift 100 times its rating... so what do you do? these days the biggest danger is not the job, but the next guy that has no idea, or is drunk, or whatever- when people do stupid things these days, its never their fault anymore... spill coffee on yourself, slip on obviously icy surface, or try to lift 10 tons with a plainly marked 500# rated 'tool' that wasnt engineered/certified for lifting- its never their fault...

garyhlucas
10-02-2015, 09:20 PM
When a thread devolves into what a lawyer might say instead of a reasonable discussion of the simple physics involved here it drives me nuts! The highest stress on a fork is at the bend, not because it is bent but because the support is behind it. So a hole that size 15" away is of no consequence. If an engineer needs to do a calculation to come to that conclusion he is a pretender with a degree.

J Tiers
10-02-2015, 11:43 PM
I have seen forks with holes drilled before. Typically they are well out near the end of the fork, where the bending forces are much lower. Is there a reason why it cannot be drilled there, if it must be drilled?

Drilling back near the bend sounds like a less-than-good idea. And, of course, drilling any fork, anywhere, will obviously cause lead poisoning, premature baldness, vision problems, and every possible form of E.D., as is well known to the safety nannys.

Scottike
10-03-2015, 12:14 PM
I drilled a set of forks a couple of weeks ago using an annular cutter and the radial DP at work.
Easy peasy - just use plenty of cutting oil and low speed. The holes I drilled were near the ends
of the forks for safety pins to keep lift straps from sliding off.
using a mag drill should work fine as well.

bob308
10-03-2015, 12:25 PM
now I agree with any time it comes down to a lawyer it drives me crazy too. but by law you may not alter forklift forks in any way. and I have seen may with crude holes burned in the ends. I have also seen forks fail.

as long as you are not in an industrial use do what you want.

LKeithR
10-03-2015, 12:29 PM
When a thread devolves into what a lawyer might say instead of a reasonable discussion of the simple physics involved here it drives me nuts!

?????? If there are potential negative consequences to doing something then I think it's perfectly legitimate to mention them when the subject is being discussed--helping people stay out of trouble should always be part of the discussion. Putting holes in forklift forks is NOT a good idea because it weakens them. Period. You have removed material therefore they will have less strength. Around here if workers comp finds holes in a fork they will immediately issue a stop use order and the machine gets parked till the forks are replaced...the owner and/or business are also going to get a fine...

Paul Alciatore
10-03-2015, 05:11 PM
Gary, I agree with you. It drives me nuts too. But life is life.

If it goes to a jury, do you think you will get 8 or 12 people who are all engineers or even good mechanics (like some that you find here) who will understand the issues? You are going to get housewives, accountants, butchers, bakers, and candlestick makers. You will be lucky if they are all HS graduates. They will NOT have any background in mechanics, either practical or theoretical, and they WILL hear the arguments from the lawyers (again not engineers or mechanics) and will have to make a decision. Those arguments will be maximized for the benefit of the respective clients and may contain little common sense. It is a crap shoot. And they will probably SEE the crippled victim in his or her wheel chair in the courtroom or a photo from before the wake. I wonder how they are going to vote.

I would agree that the proposed holes, in the locations described AND if they were CENTERED on the forks AND if they did not exceed about 20% of the width of the forks, would not weaken them in any significant amount. In short, they would be perfectly safe. Structural members are drilled all the time. But I, personally would not take the chance. I would find a method of attachment that does not require changes to the original forks.

I have been criticized for offering legal cautions on these boards before. I feel that anyone making such modifications should consider the legal implications. It may never happen, but an accident that involved that equipment could be a life altering event for the person who made the modifications. He or she could lose a lot financially. Small chance? Yes. But the potential loss may be very large, including both business as well as personal property if the business is not incorporated. Do it if you will, but just be aware of the possible consequences.

On that method of attachment, I would probably have a couple of rectangular holes that I could drive the forks through. Then some clamps that are complete, hollow rectangles made from heavy gauge steel and properly welded. They would slip over the top end of the vertical part of the forks and OVER the vertical arms of the attachment. They would be stopped by some projection at the proper attachment point and secured by one or two small bolts in a tab which projects above the center of their rear face, definitely NOT ON THE SIDES which would be in tension. This would make attachment easy and very secure.




When a thread devolves into what a lawyer might say instead of a reasonable discussion of the simple physics involved here it drives me nuts! The highest stress on a fork is at the bend, not because it is bent but because the support is behind it. So a hole that size 15" away is of no consequence. If an engineer needs to do a calculation to come to that conclusion he is a pretender with a degree.

Rosco-P
10-03-2015, 05:45 PM
Gary, I agree with you. It drives me nuts too. But life is life.

If it goes to a jury, do you think you will get 8 or 12 people who are all engineers or even good mechanics (like some that you find here) who will understand the issues? You are going to get housewives, accountants, butchers, bakers, and candlestick makers. You will be lucky if they are all HS graduates. They will NOT have any background in mechanics, either practical or theoretical, and they WILL hear the arguments from the lawyers (again not engineers or mechanics) and will have to make a decision. Those arguments will be maximized for the benefit of the respective clients and may contain little common sense.

Those twelve will also contain teachers of many different levels and specialized disciplines. The twelve are not there to decide based on their own experiences but on the information and testimony presented. There may be expert testimony from an Engineering or accident recreation/analysis firm, in which case you are well and truly screwed.

Mcgyver
10-03-2015, 05:49 PM
When a thread devolves into what a lawyer might say instead of a reasonable discussion of the simple physics involved here it drives me nuts! The highest stress on a fork is at the bend, not because it is bent but because the support is behind it.

its hardly anything to do with lawyers, its to do with liability. In the privacy of my home shop where I'm the only one exposed to it I'll do what ever I want and agree this mod would be fine....In a commercial setting, you do NOT modify any lifting devices without a stamped drawing and you'd be hard pressed to get a modified one certified, which they have to be. Hopefully the reasons are obvious

boslab
10-03-2015, 05:54 PM
I was given a set of forks not long back, scrap from a Toyota truck place, they had a bin full, they get scrapped because of heel wear on the warehouse floor concrete, other than a bit of wear they looked perfect, heavy lumps of steel, what to do with them I don't yet know, I was going to fit them onto my skid steer, till the engine blew, still haven't fixed, too busy house building at the present.
I've seen several forks with tip holes, don't suppose that would hurt,
Mark

Black_Moons
10-04-2015, 12:48 AM
If the clamp your using slips.. Maybe the answer is to grind a tiny notch (1/4", rounded inside to avoid stress raisers) that could be used to positively locate the clamp? Ie the clamp has a mating little bump that goes into the notch, no way for the clamp to move if it locked in.

mike4
10-05-2015, 03:47 AM
Why not put a pair of extended tabs with a hole through each , like the ones on fork extensions , simply pin them in place , no liability issues with the forks.

As far as the attachment goes the lifting capacity of the machine is derated by most attacthments , just have a look at a jib for example.

Michael