Sheared Allen Bolt Help

[Yellow Saddle]

I've heard a similar tale but the drill they used was left in their drill.
To answer @Yellow Saddle You would use a drill You can even gets taps in order to thread holes that small, Watchmakers use them all the time or did you think that those little screws were put in by elves.

I would still like to see a picture or description of the tool/drill. If it is a twist drill 0.25mm in diameter and we assume the flute is 1/3rd of the diameter, then the centerpiece is a mere 0.093mm thick, which means it isn't rigid at all. I would assume then that the drill is not a twist drill but something else. Watchmaking didn't come to mind at first but yes, that would be an obvious example of where such small holes are routinely drilled.
Nevertheless, I doubt the collar could be drilled. Reason being that the tip of the broken off tough stainless steel bolt will be a) jagged and b) recessed beyond good visibility. To keep the drill centered, you'd need a very rigid tool or a way to accurately centre-punch/mark the jagged, recessed end. Nevertheless, if someone can drill a hole through the centre of the world's smallest drill which presumably was made from HSS or something similar, then the collar could be rescued by a skilled craftsman. My guess is that a new collar or even a new hub would be cheaper.

 

[neil_merseyside]

I would still like to see a picture or description of the tool/drill. If it is a twist drill 0.25mm in diameter and we assume the flute is 1/3rd of the diameter, then the centerpiece is a mere 0.093mm thick, which means it isn't rigid at all. I would assume then that the drill is not a twist drill but something else. Watchmaking didn't come to mind at first but yes, that would be an obvious example of where such small holes are routinely drilled.
Nevertheless, I doubt the collar could be drilled. Reason being that the tip of the broken off tough stainless steel bolt will be a) jagged and b) recessed beyond good visibility. To keep the drill centered, you'd need a very rigid tool or a way to accurately centre-punch/mark the jagged, recessed end. Nevertheless, if someone can drill a hole through the centre of the world's smallest drill which presumably was made from HSS or something similar, then the collar could be rescued by a skilled craftsman. My guess is that a new collar or even a new hub would be cheaper.

http://uk.rs-online.com/web/p/twist-drill-bits/7877315/

Just like an ordinary drill - that isn't actual photo of it but they are just ordinary looking twist drills, the pin chuck to use it needs to be top notch to actually get one to run true as any eccentricity can cause it to snap. Easiest way to resolve jagged parts is to use a small diamond burr in a dremel to flatten an area and then centre pop it. I doubt you'd need to use anything much below 1mm to start a hole to get a good easy-out in. I might try and do it to prove I could but it'd be far cheaper in time to buy a new collar.

 

[bpsmith]

All sorted!

Asked the guys at the Swansea Giant shop and they managed to get some purchase on the bolt by cutting a tiny notch in the protruding bit and then working free with a small driver. Result!

New collar was out of stock with Fulcrum's UK suppliers, so chuffed with this and only cost me some flapjacks and a tin of biscuits. Can't argue there!

 

[bpsmith]

Just goes to show that even the bigger shops have plenty of goodwill to offer. I have bought a few bits and bobs in there mind you, and fancying the new Giant aero helmet his colleague was talking about too, so we're all happy.

 

[Pumpkin the robot]

I would still like to see a picture or description of the tool/drill. If it is a twist drill 0.25mm in diameter and we assume the flute is 1/3rd of the diameter, then the centerpiece is a mere 0.093mm thick, which means it isn't rigid at all. I would assume then that the drill is not a twist drill but something else. Watchmaking didn't come to mind at first but yes, that would be an obvious example of where such small holes are routinely drilled.
Nevertheless, I doubt the collar could be drilled. Reason being that the tip of the broken off tough stainless steel bolt will be a) jagged and b) recessed beyond good visibility. To keep the drill centered, you'd need a very rigid tool or a way to accurately centre-punch/mark the jagged, recessed end. Nevertheless, if someone can drill a hole through the centre of the world's smallest drill which presumably was made from HSS or something similar, then the collar could be rescued by a skilled craftsman. My guess is that a new collar or even a new hub would be cheaper.

No pics I am afriad but it is just like a normal twist drill as mentioned above. The flutes are a lot shorter than normal so the majority of the drill is actually just a cylinderical shape for the tool to be held.
With bolts that have have been broken and are uneven, you "clock" the hole with a DTI so that you are in the dead centre of the bolt and then either use an endmill or slot drill to machine the top of the bolt flat and then use a centre drill and then the correct size tapping drill to remove the bolt, or (and this is how I normally do it) Just clock the hole and use a tungsten carbide drill to drill it out. The carbide drills are very rigid and do not deflect like a HSS drill does so they self centre up to about 20 degrees. Of course it helps when you have a cnc machining centre to be able to do these sorts of things, but that is why I would say take it to a machine shop, they deal with this sort of thing all the time and can do it quickly and easily without damaging the part that the bolt or screw is stuck in. The most common thing that we do like this is taps that we break in the parts we are making, but a carbide drill will go through a broken HSS tap if you take enough care. If that fails, then as someone else mentioned it can be spark eroded out.

 

[Yellow Saddle]

No pics I am afriad but it is just like a normal twist drill as mentioned above. The flutes are a lot shorter than normal so the majority of the drill is actually just a cylinderical shape for the tool to be held.
With bolts that have have been broken and are uneven, you "clock" the hole with a DTI so that you are in the dead centre of the bolt and then either use an endmill or slot drill to machine the top of the bolt flat and then use a centre drill and then the correct size tapping drill to remove the bolt, or (and this is how I normally do it) Just clock the hole and use a tungsten carbide drill to drill it out. The carbide drills are very rigid and do not deflect like a HSS drill does so they self centre up to about 20 degrees. Of course it helps when you have a cnc machining centre to be able to do these sorts of things, but that is why I would say take it to a machine shop, they deal with this sort of thing all the time and can do it quickly and easily without damaging the part that the bolt or screw is stuck in. The most common thing that we do like this is taps that we break in the parts we are making, but a carbide drill will go through a broken HSS tap if you take enough care. If that fails, then as someone else mentioned it can be spark eroded out.

Thanks, one more thing. What is a DTI?

 

[fatboy123cycling]

Thanks, one more thing. What is a DTI?

A DTI is a Dial Test Indicator ( clock gauge) can be either Metric or English and different graduations depending on the accuracy required

 

[raleighnut]

A DTI is a Dial Test Indicator ( clock gauge) can be either Metric or English and different graduations depending on the accuracy required

Beat me to it.

 

[Yellow Saddle]

Thanks, I have one of those that I used for measuring wheel trueness at a stage as well as one in my spoke tensiometer, but just never thought of it as a DTI. Where I come from, DTI is Department of Trade and Industry, shortcut for fatcats who travel to trade shows in exotic locations and sponsored by the tax payer.

 

[Pumpkin the robot]

Thanks, I have one of those that I used for measuring wheel trueness at a stage as well as one in my spoke tensiometer, but just never thought of it as a DTI. Where I come from, DTI is Department of Trade and Industry, shortcut for fatcats who travel to trade shows in exotic locations and sponsored by the tax payer.

I expect the DTI you have is a plunger type one? I prefer to use a finger clock like the one pictured below. In that pic, I was putting O ring grooves in the cyclinder heads of one of my motorbikes so that I could do away with the head gaskets. I was clocking the head to get it flat on the jig I had made to hold it. You can normally get things to within 0.02 easily enough with these. I do have another clock that is more accurate and that measures in microns {0.001mm)

 

[Yellow Saddle]

I expect the DTI you have is a plunger type one? I prefer to use a finger clock like the one pictured below. In that pic, I was putting O ring grooves in the cyclinder heads of one of my motorbikes so that I could do away with the head gaskets. I was clocking the head to get it flat on the jig I had made to hold it. You can normally get things to within 0.02 easily enough with these. I do have another clock that is more accurate and that measures in microns {0.001mm)

Thanks, a picture is worth a lot of verbage. Yyes mine is thus a plunger type. I presume, what's happening in this picture, is you are using the drill press (milling machine?) as a jig to hold the DTI as it is turned around to find high and low sections under the needle?

I get the general drift, but how would you use that to say find the centre of the jagged edge recessed in a hole as we discussed in the OP's collar?

As a hijack to the hijack, interesting that you could use O-rings as a head gasket. I would have thought they would blow out but do you use a high Shore rating or some other method?

 

[raleighnut]

The 'O' rings would be to seal the water jacket. It used to be quite common on air cooled 2 strokes to dispense with the head gasket and fit 2 base gaskets to change the port timing of the transfer ports (its quite easy to file the exhaust port to change its timing but very difficult to modify the transfers)

 

[Citius]

I was putting O ring grooves in the cyclinder heads of one of my motorbikes so that I could do away with the head gaskets.

Looks like a two-stroke head - what engine?

 

[Pumpkin the robot]

Thanks, a picture is worth a lot of verbage. Yyes mine is thus a plunger type. I presume, what's happening in this picture, is you are using the drill press (milling machine?) as a jig to hold the DTI as it is turned around to find high and low sections under the needle?

I get the general drift, but how would you use that to say find the centre of the jagged edge recessed in a hole as we discussed in the OP's collar?

As a hijack to the hijack, interesting that you could use O-rings as a head gasket. I would have thought they would blow out but do you use a high Shore rating or some other method?

When you clock soemthing up there is normally something you can pick up to get the centre of it, whether it be a boss or if it is a thread we sometimes stick a screw in and clock that up. If the screw is broken above the thread you can normally get close by eye, drill down and colapse the top of the screw and pick the hole up.
The material of the o rings is nitrile, it only has to seal the water jacket.

The 'O' rings would be to seal the water jacket. It used to be quite common on air cooled 2 strokes to dispense with the head gasket and fit 2 base gaskets to change the port timing of the transfer ports (its quite easy to file the exhaust port to change its timing but very difficult to modify the transfers)

The o rings allow the cyclinder head to be dropped so that the squish band is less. In this case I machined the heads so that the squish band was 0.8mm. A larger base gasket was used to lift the exhaust port and give more power at the top end. Its a track bike 2 stroke, so I was not too bothered about the bottom end, once it is in the power band it should stay there!

Looks like a two-stroke head - what engine?

Its an RGV 250