BR Standard class 6 No. 72010 'Hengist' and Clan Discussion Thread

So the guy who sticks appropriate song clips could give us
Turn ( Byrds)
Sledgehammer ( Peter Gabriel)
The lion sleeps tonight..... (Tight Fit)

 

Hope they don't include anything from the Pretenders 'Loose Screw' album.
(Hey, don't blame me, he started it! )

 

Thank you. How is the internal diameter of the hole measured to the required standard of accuracy. Can you do this with inside calipers? Is conicity (if that is a word) a concern? Also, for the final finished diameter of the bolt, is that done by grinding rather than in the lathe?

 

I cannot answer for 'Clan' as they may be doing it slightly different, but in my experience once the various metal parts are perfectly located,( remember that the holes may not line-up perfectly), a reamer is carefully put through the resulting hole. The size of the reamer is then increased until a single diameter hole results. So the hole size is the reamer size, OK? The reamers accuracy ensures the accuracy of the hole, so good tools are an absolute necessity!
The bolt shank size is turned to suit. With good lathes/operators/tools an extremely smooth accurate finish can be achieved. Not just a modern ability as this was possible over a century ago.
Hope that helps you.

 

Thank you. When you say the size of the reamer is increased, are you referring to an adjustable reamer? Understandably, this would produce a hole of arbitrary size requiring individual fitting. I was thinking that perhaps because of the accuracy needed (nearest thou or less?), the concern was the limitations of the drill and set up (e.g. fairly small magnetic base drills seem to be popular in loco overhaul work), which with a non-adjustable reamer might produce deviations from the nominal size (plus the conicity I referred to earlier). The reason I enquired about a ground finish is that I noticed these people advertise such https://www.haguefasteners.co.uk/bolts/fitted-bolts/

The suggestion that the holes may not line up perfectly suggests that the holes are pre-drilled. Is this always going to be the case or could you put the drill through e.g. the frame and stretcher in one operation?

Do the semi-finished bolts have a centre hole at the screwed end to make it easier to align in the lathe? (Sorry, I appreciate you may not have the answer so don't feel obliged to answer).

 

Nothernsteam is on the right track. Geoff and I have a disagreement on this one - light hearted! Geoff would say that if both components to be joined are drilled by CNC to the same drawing, the holes should line up. As I've rebuilt 2 Land Rovers, I have the scars to not believe him! Some of the holes on the frames are not in alignment. Geoff was concerned about getting absolute alignment as the frames are so big. However as all of the holes are 1/16" undersize, they will be aligned once the hole is drilled to full size. We won't use an ordinary twist drill as we want to ensure that the drill doesn't follow the line of least resistance. We were looking at the drill bits that will be used with the magnetic drill today.

For the bogie stretcher we are probably going to drill the holes to final size

I believe that they will be using a non adjutable reamer. Once the hole has been reamed the bolt shank will be turned down to the correct diameter to give a drive fit.

For the 6 (per side) axle centre marking holes (on either side of the horn guides, last week Phil Yates had loaned Keith a special type of very accurate bore micrometer similar to https://www.zoro.co.uk/shop/measuri...MIjaPuzJHW5AIVhrHtCh21NgWZEAQYBCABEgIVN_D_BwE

Yes, the semi finished bolts should have a turning centre at the threaded end. However, we did a goods inwards inspection today and found that the 3/4" and 7/8" bolts don't. They've gone back to Generic who have apologised.

You can see some pictures of the alignment check last Wednesday from this link https://photos.app.goo.gl/HyWpkbjyrqkrNjYD9

 

Thanks, interesting stuff. A note of the measurements of the reamed holes, to get some sort of standard deviation, may be useful information for the project and to others. Once you have determined the size of a hole, how quickly can the bolt be finished? Do they have to be sent away for final finishing or can they be done on site?

What type of drill are you looking at for use where the holes are not aligned. Can you use a large slot drill?

 

The bolts can be turned on site. We have had discussions on monitoring reamer wear as there are a lot of bolts to fit. I'm sure about what sort of drills they are intending to use. We were looking at 2 of these that were on the adjacent bench yesterday - https://uk.rs-online.com/web/p/prod...VhLHtCh08wQCWEAQYAyABEgIW7PD_BwE&gclsrc=aw.ds. I will ask CTL Seal when I next see them

 

Newbie question - why are bolts being used to secure the frames instead of rivets, please?

 

Hello Tobbes. The best explanation is from a paper written by Mike Beswick, one of our engineering team. You can find it here https://www.theclanproject.org/design/Clan_Bolts.php

 

Fascinating, very many thanks!

 

Don't forget that we have our Annual General meeting at CTL Seal on Saturday 21 September. The meeting will be held at the premises of CTL Seal Ltd at Butterthwaite Lane, Ecclesfield, Sheffield, S35 9WA and doors will open at 1330. The meeting is open to all but only members of SSLC can vote. This will be an opportunity for you to see the frames complete at the first stage of assembly. So if you're not a member, come along and have a look - see if you want to join us at an interesting stage of the project's development

 

Thanks. Do they come in imperial sizes?

 

Yes they do although a little harder to find. They are brilliant bits of kit.

 

Would suggest using three or four fluted core drills.
Rota broaches are basically a trepanning tool and require a spring loaded centre as a guide, although they are good when used correctly.

 

Thinking about it, if you are going to stick a reamer through it, then one could perhaps use a metric rotabroach (or other drill bit, noting @std-tank 's comment - perhaps something like this https://www.drill-service.co.uk/pro.../dcorets4-hss-core-drill-4-flute-taper-shank/ - provided you can drive a 2 morse taper shank, but presumably that is what the reamers have), say 23 or 24mm for a 1" hole as the reamer needs something to work on.

 

Anthony, the lead CTL Seal assembly shop foreman will be on site on Saturday if you want more details

 

Tungsten-Carbide Drills ?

 

I’m sure this will have been thought of, but wouldn’t it have been easier to drill all the holes to a specified (far)smaller size so the frame parts can be located, then drill and ream all to the same size? Surely it’s easier to do it that way to match the finish turned bolts rather than to have to remachine each individually?


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That's the way I'd do it, putting a boilersmiths reamer through each hole, followed by a sizing reamer if considered necessary. All these alternative suggestions seem to be just making things more complicated. And, if you are bolting, is each bolt going to be fitted with a retaining cotter or are you simply going to rely on the Philidas nut?