MadModder
Gallery, Projects and General => How do I?? => Topic started by: awemawson on May 14, 2014, 09:21:04 AM
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I need to enlarge some 22mm mounting pin holes in my Twose 276 Hedge cutting Flail to take 1" pins
This is the Flail:
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And these are the mounting lugs with the holes in question:
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Turn some bushes for the holes on the tractor.
Russell
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Just lift it onto the mill and bore....
But seriously I think this is a job for a mag drill I would have thought. Don't know how accurate they are though so you may need to drill oversize and make some bushes.
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Do you have access to a mag drill ? If you're careful at the start then it'll do it no problem. If you're not confident then you can tack weld a plate behind the hole to locate the spring centre.
Mike
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All a bit too big to put on the table of the Bridgeport :bang:
The side plates with the holes are 1/2" mild steel plate. My plan was to cut a hole in another piece of 1/2" plate with a 1" Starrett hole saw. Clamp it over the 'to be enlarged' hole, centring using a suitable stepped plug, and using a mains hand drill cut the new holes.
I did some experiments with a couple of Starrett hole saws, and they were quite happy cutting 1/2" plate using their outer diameter as a guide.
Then I find I can no longer buy 1" cutters. Nearest metric equivalent is a 27mm, which actually when tested cuts a 27.5 mm hole. Now accuracy is not too critical - these are load bearing (but not revolving) pins - but 27.5 mm ie 2.3 mm is too much slack.
I am trying to keep to Starrett as they are good quality and seem up to the job and was amazed that 1" was no longer available
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OK chaps you got in with replies while I was typing !
Yes I have a mag drill, but the access precludes its use :(
Yes I can turn bushes, I can make stepped pins and all sorts of other solutions, but I want to INCREASE the pin size not decrease it. There is a HUGE torque sideways when this is mounted, and I'm planning on using 1" EN24T shaft as pins
In a previous life this flail was just mounted on the 3 point linkage, and the differential torque on the lifting arms twisted and sheared the main cross shaft that the lifting cylinder acts on, and that was 1 1/2" steel of some sort. This new set up will mount directly on the tractor and not use the lifting arms at all.
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If they cut oversize would a 25mm cutter get you close to the 1" diameter?
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I had ruled out the 25mm, as oversize would be ok'ish but undersize would be a no-no. and 1" is 25.4 mm as we all know
.. . . . until I spoke to Starrett Tech Support in Scotland :scratch:
It seems that the 1" Starrett constant pitch hole saw sold in the USA is the very same 25mm hole saw they sell in the UK :bang:
What they do with the missing 0.4 mm is probably best left unanswered :lol:
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Probably falls overboard on the way over the Atlantic. :palm:
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Can you not use a 1" Blacksmiths drill. They have 1/2" shafts and come in imperial sizes. I paid £4 each for mine.
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Hi Andrew, just going back to Russell T's suggestion of bushing the eyes on the tractor.
Yes it does reduce the pin diameter by 3mm but surely a slightly smaller pin made from a high grade steel could compensate for that.
A couple of other alternatives:Make up a piloted cutter with the pilot a snug fit in the holes and long enough to extend through both holes of the yoke. Drill one side out then with the aid of a bush with suitable external diameter to fit in the enlarged hole and internal corresponding to pilot size enlarge the second hole from the opposite side.
Also Bahco do some very good quality bi-metal hole saws,maybe you could find a suitable size in their range....OZ.
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Just another thought, what about using an expanding reamer,a little labourious but I think it would get you the result....OZ.
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Can you not use a 1" Blacksmiths drill. They have 1/2" shafts and come in imperial sizes. I paid £4 each for mine.
Thanks, but starting a 1" blacksmiths drill (which I have) in a 22 mm hole will inevitably snatch and do me some damage :bugeye:
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Hi Andrew, just going back to Russell T's suggestion of bushing the eyes on the tractor.
Yes it does reduce the pin diameter by 3mm but surely a slightly smaller pin made from a high grade steel could compensate for that.
A couple of other alternatives:Make up a piloted cutter with the pilot a snug fit in the holes and long enough to extend through both holes of the yoke. Drill one side out then with the aid of a bush with suitable external diameter to fit in the enlarged hole and internal corresponding to pilot size enlarge the second hole from the opposite side.
Also Bahco do some very good quality bi-metal hole saws,maybe you could find a suitable size in their range....OZ.
Easiest solution is to turn a stepped pin and leave holes present size. However that is asking for a fatigue crack at the transition point. I really want to beef up the pin so I will go with the 25mm but in reality 1" hole saw that I now have on order.
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Just another thought, what about using an expanding reamer,a little labourious but I think it would get you the result....OZ.
Yes I thought about that as well ! However access is very difficult, the machine is balanced precariously, and the thought of trying to turn an adjustable reamer, keep it in line, all lying on the floor under a heavy implement doesn't appeal :)
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It will be interesting to see how you solve this,please post up a couple of photos of the job in progress....OZ.
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Can you make a boring bar that fits the existing holes? Then just set the cutter for the 1" dia with a 1" plug to slip on for when doing the other side to keep the holes lined up, you should be able to use a drill to power it.
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tom beat me to it :)
just a length of 22 mm bar with a hss or carbide single point cutter mounted in it. single point could be driven with a good battery drill if necessary.
clamp.on a couple of extra 22mm holes as guides.
bill
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I would go with the hole saw and plenty of cutting fluid - remember it is a round hacksaw blade. :)
In stead of of the 1/4" drill bit use a 22 mm diameter guide. The hole will probably come out a bit bigger than 25mm - well mine always do :Doh:
:beer:
DaveH
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Yes Dave that's what I'm now going to do, now Starrett tell me their 25mm saws are actually 1" :scratch:
I'll make a guide by cutting a hole in a thick bit of plate and clamp it in place as I originally intended but was initially thwarted by the apparent lack of 1" saws :bang:
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Comparing the hole producted by a 1" hole cutter in a hand drill, to line boring:
Line boring:
+ accurate size to whatever tolerance you want especially if you make guide bushings for the existing holes,
+ round holes
+ both holes concentric / aligned.
+ in the correct place (assuming the existing holes are reasonably round and in the correct place).
+ more controllable, adustable process,
+ safer for the operator. Only torque to be reacted.
- Have to make up the long boring shaft, at least one guide bushing, probably three, if you use a piece of 20mm or 3/4" stock for the boring bar.
Hole cutter (hand held drill, unpiloted - guided by 1/2 plate):
- no control of diameter. Starrett knows a thing or two about metrology, and considers a 25mm and inch hole made with these things as equivelent. That is a strong hint.
- no control of alignment between two sides.
- terrible surface finish in holes
- more danger to operator if it grabs
- have to make the 1/2' guide plate.
Regards,
Mark
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The job doesn't justify line boring, and also that would be very difficult to arrange 'in the field' although specialist kit is available to do it. If this was the sockets for rotating pins on, for instance, a back hoe then yes. However in this situation it's the hole saw - horses for courses.
Actually I was surprised how good the surface finish was on my test samples, but obviously not as good a boring
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last time i had to do something similar, i found a nice solid fallen tree branch and hammerd it in the origional hole as a plug. i then just used my normal hole cutter with pilot, centerd as best i could.
worked fine for me and got me out of trouble when all the shops were shut and i was miles from a workshop.
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Well the Starrett hole saw arrived today so I set to and enlarged the holes:
First clear the nettles, brambles and other detritus that I'd otherwise have to roll around in - I also hauled the huge hydraulic pump out of the way.
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Then made up a stepped alignment peg and a jig. I didn't have any 1/2" plate to hand so welded a couple of bits of 6mm plate together for the jig
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Pop the alignment peg in the hole. Clamp the jig round it and off we go :ddb:
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End result: a pair of 22mm holes enlarged to 1" - and the barstock that I'll use for pins actually fits :lol:
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So far so good. However next job is to weld up an outrigger parallel to the existing plate, as the pins extend past the existing one through a 'top link' (*) swivel eye and without additional support would be be susceptible to bending.
I sliced up a length of heavy 3" x 4" x 8mm angle to form the out riggers - need to bore a 1" hole in the right place then weld them in place. Job for Monday as tomorrow is full with family duties.
(* Top Link is basically a huge turn buckle - a pair of spherically aligning 1" bore eyes mounted on 1 1/8" UNC left hand and right hand threads, with a threaded tube between them allowing adjustment of eye to eye spacing. Conventionally used on a tractor 'three point linkage' as the upper support which needs adjustment to set the angle of the attached implement. In this case being used as bracing supporting the weight of the flail and thus avoiding using the hydraulic raising bars.)
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Thanks for posting the pictures. Just out of interest, what final size did that 25mm hole saw end up cutting?
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I haven't actually measured it but they are a tightish push fit on nominal 1" bar. In fact I may have to use an adjustable reamer to ease them out a bit, as you don't want tight pins when trying to get things in alignment and assembled.
I'll weld on the extra web, in which I will have pre-drilled a hole, then decide how to ease them out a bit. A flap wheel may be sufficient if things don't move too much with the welding, otherwise I'l pass a 26mm reamer through them.
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The Postman brought a one metre length of 1" EN24T bar this morning, so it rapidly got converted into three pins and a spacer:
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The bigger pins go through those pesky holes, and also through an outrigger that I've welded on to give a bit more outer support to stop the pin bending too much:
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This pair of brackets take both the lower lift arms of the tractor, and a triangulated set up so the not inconsiderable weight is taken by the tractors 'top link bracket'. This way the set up can be adjusted to be rigid and not differentially twist the hydraulic lifting shaft.
Here is a mock up of the triangulation, where the 1" bar at the front of the picture mimics the top link bracket on the tractor
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Now the astute amongst you will have noticed that the eyes on that bar need to come much closer together, but the ball socket in the eye doesn't give enough 'crank'
Cranked eyes must be available as I have one on a top link that in it's original purpose should have been straight anyway !, but so far I've not managed to obtain another one !
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The threads on these are 1 1/8" UNC. Now I've found ones with 3/4" UNC but not 1 1/8". Usually these sorts of things are available in the Sparex catalogue, but not this actual one :(
The link I have with a crank is made in India by the unfortunately named Swastik company who have an emblem remarkably like the one young Mr Hitler used to use. Never the less I've not been able to track down any bent eyes !
http://www.indiamart.com/swastik-engineering-products/
I suppose if I have to I can bend one having heated it with oxy-acetylene, but not sure if they are heat treated after forging :scratch:
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Can you scratch the crooked version at the bend with a file, Andrew?
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Since I may have to reproduce a hardened valve rotator cap, not knowing the degree of hardness they were originally tempered to, I did a search and came up with this list from Wikipedia:
Faint-yellow – 176 °C (349 °F) – engravers, razors, scrapers
Light-straw – 205 °C (401 °F) – rock drills, reamers, metal-cutting saws
Dark-straw – 226 °C (439 °F) – scribers, planer blades
Brown – 260 °C (500 °F) – taps, dies, drill bits, hammers, cold chisels
Purple – 282 °C (540 °F) – surgical tools, punches, stone carving tools
Dark blue – 310 °C (590 °F) – screwdrivers, wrenches
Light blue – 337 °C (639 °F) – springs, wood-cutting saws
Grey-blue – 371 °C (700 °F) and higher – structural steel
It seems to me that maybe I can use this info to get an approximate hardness measure of an existing cap, by scratching it with some of the above to see where the hardness falls. Kind of like doing a hardness scratch test to identify minerals.
Handy that the translation to a tempering color can be got by using this list as well.
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Steve,
Both the 'cranked' eye and the straight ones are file-able. A quick bit of trig shows that I need about 13.5 degrees on both ends. Now the ball swivels look to have been made to accommodate 10 degrees, and the cranked version measures at about 15 degrees - ( crude measurements with it clamped in a vice, and eyeing a protractor to be parallel with the bench ! )
Useful list that you reproduce there - I can see it being handy to interpret hardness from things lying to hand. A bit like a Moh's scale of hardness where things are listed in order of their ability to scratch others. Perhaps we can call it ' Steve scale of Tool Hardnesses ' :clap:
I have a feeling that the oxy- acetylene torch is coming out to play soon :lol:
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I must have misunderstood something here. Surely the closer the eyes are together the less resistance to torque there is, which I thought was the point of the modification.
Russell
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Russell,
The assembly is forming a rigid pyramid - but what is not showing in the picture are the lifting arms that pivot on lugs on the tractors axle and the outer ends go onto the pins though the enlarged holes.
Normally these arms are connected to links dropping down from levers on a shaft that runs parallel to the axle, but at a higher level. the shaft being rotated by a beefy hydraulic cylinder and thus raising the arms.
Now if the hedging flail rocks from side to side, more load is placed on one lifting arm than the other, and this over torques the shaft, and indeed has broken one in the past :(
I am doing away (while the flail is mounted) with the links that drop down from the levers, and replacing the lifting hydraulic force with this rigid pyramid of adjustable 'top links' so I can pre-set the height off the ground, but when tightened up there will be no slop at all.
On the rear of the tractor (all tractors) there is a mounting point for the 'top link' that is specially designed to be a strong attachment point, comprising a pair of projecting lugs with a pin through them. The actual 'top link' goes between these lugs and my 'support top links' will go on the same pin, but on the outer side of the lugs. To avoid having a wide (and thus easily bent) pin, the 'support top links need to be snug up against the lugs. I am planning to weld up a bridge piece to pick up the ends of the pin and take reinforcement from a second pair of lugs this particular tractor is furnished with.
A bit complicated - I hope I explained that lucidly :scratch:
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Hi Andrew look like the job turned out well , excuse the pun :lol:. I used to own a 1956 Grey Fergie TEF20 4 cylinder diesel and remember messing about trying to get impliments to fit that , flail mower etc, The little tractor still did everything it would have done when it was new 50 years after it was built :thumbup:
Cheers Mick.
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This project has been dragging on as I have failed to source 'bent eyes' for the 'top links' so today I decided to take things in hand and ask the oxy-acetylene torch to give me a hand!
You'll recall that standard ends are straight but I needed cranked ones to get the correct angle
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So with the help of the gas axe we ended up with this:
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Currently they are cooling - when just warm they'll get a light spray of zinc rich paint to replace what was burnt off.
I had a bit of inspiration the other day - went to an 80 th birthday celebration of a friend, which involved staying over night in the motorhome on a local farm. Tucked in a barn obviously not used for decades was 'the real thing' A hedge flail mounted on a tractor using the proper adaptor plate. First time I've been able to get 'up close and personal' with this item. Well not too close, it was deeply buried in nettles.
However I got a few photos of the adaptor and the way the lower pins were supposed to be.
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So the next job is to draw up a plate like the triangular ones in the photo and glue it all together with a bit of 6013
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Must be the season for tractor work! :beer: