Which way do I do this?

[WolfieParticipant @wolfie]

Not been around for a short while as I had a number of commissions come in with my other modelling head on plus a death in the family.

Anyway, I am on almost the last part of my S50 and I've made a cock of it so many times its close to getting slung in the beck lol.

Its the steam chest. I am struggling to drill the long hole from top to bottom. I actually had the piece made and then ruined it trying to drill the hole grrr.

Its not helped by two blokes in my club telling me to do it in different ways, both chaps I admire as great engineers but one tells me to drill first and mill steam chest out after, and the other tells me to drill last!

How do I do this grrrrrrr

[WolfieParticipant @wolfie]

[John Stevenson 1Participant @johnstevenson1]

Do you want a third way ?

Personally when you want a long hole to come out right BOTH ends I'd mark out and drill undersize from either end, then mill out, then ream. Think logcally, you then have two holes in the right place and any miss alignment where the drills meet in the middle is now missing, all it takes is for the reamer to self align these two holes.

John S.

[Sub MandrelParticipant @submandrel]

Hi wolfie, sorry to hear the sad news.

As I recall from my 10V, the problem is that the steam chest is cored out with a hole in the centre That means if you drill though, the drill skids on the far side of the hole (I'll call this the 'cavity&#39.

So… regardless of whether before or after the other machining: drill the first part of the hole for the valve rod into the central cavity. Now get a piece of silver steel or just hard steel the same diameter as the valve rod witha point turned or ground on the end, and preferably hardened. Use this as a punch through the drilled hole to make a centre on the far side of the cavity.

The long drill now has a little centre pop to stop it wandering.

Or you can cheat and not have a 'tail' on the valve rod, it will work just as well and only you, me and Google will know

Neil

[NJHParticipant @njh]

I don't know your sizes here Wolfie but I recall, I think it was a Stuart No. 7, I made many years ago. The steam chest was a casting and required a hole for the valve rod where it entered and a smaller hole at the far side which, of course needed to be in line. The process was to drill the entry hole then take a piece of silver steel (which was a good fit in this hole) drill down the end of this for a close fit on a No. 1 centre dill and loctite this in place. Pass the now rigid "long" centre drill through the entry hole and make a centred start on the far side of the steam chest. Withdraw made up drill and replace with correct size drill for end of valve rod which will, of course, follows the centred start. Smile in satisfaction and nip off for a swift half ( or whatever!)

Regards

Norman

P.S.

 

I see both John and Neil can type faster than I can!!

Edited By NJH on 08/04/2012 21:37:38

Edited By NJH on 08/04/2012 21:39:07

[chris stephensParticipant @chrisstephens63393]

Hi Wolfie,

You say you it made then ba**sed it up drilling the hole, I assume this means it wondered. If so, why not drill it a couple of sizes larger and Loctite in a couple of slugs of brass and then drill again, to bring it back to spec.

With regard to which order to machine the thing, to my way of thinking, machine first then drill. It is more likely you can drill the second half in line on a smooth surface than on a rough casting.

chriStephens

[JasonBModerator @jasonb]

Wolfie you may not remember that I advised on this before.

Clean up the inside first so the drill has a decent surface to start on, drill & ream the gland end then use a long series centre drill to give the bit a chance of starting on the opposite end. This is a size ) drill thats 3" long. Do it all at one setting without moving the work either in the 4jaw or mill.

You probably have not got a big enough hole to make an extension centre drill like Norman suggests. JS's method is no good in this instant as you want a blind hole for the tail rod.

J

 

And a bigger one in use

 

Edited By JasonB on 09/04/2012 07:51:38

[WolfieParticipant @wolfie]

The hole is only 3/32 in diameter, can you get a centre drill that small??

[JasonBModerator @jasonb]

No, but I know that when I suggested it before I knew that the rod was 3/32 but can't find the old thread to see why teh 1/8" drill would work.

J

Edit just found the post, you say that the 3/32 goes through a larger hole at the gland end so a size 0 centredrill has a 1/8" body which should be OK.

http://www.model-engineer.co.uk/forums/postings.asp?th=65690

 

Edited By JasonB on 09/04/2012 09:08:08

[John Stevenson 1Participant @johnstevenson1]

1/8" = 2/16" = 4/32" which in my book is bigger than 3/32" ?

My apologies to Wolfie for suggesting what I did, I didn't know the tail hole was blind.

John S.

[JasonBModerator @jasonb]

Yes John 1/8" is bigger than 3/32 but in the link I posted above your reply and in my Edit Wolfie says he has to go through a hole larger than 3/32, now it could be 7/64ths but I doubt it so its likely to be 1/8" or larger.

J

[Les Jones 1Participant @lesjones1]

Hi Wolfie,

A variation on John S's suggestion of drilling from both ends is to drill a short pilot hole from one end. Then clamp a bit of scrap metal to the driil table, drill the same size pilot hole in that and insert a short rod into this hole. Now locate the pilot hole of the work piece on this locating pin and drill from the other end. The drill must now be aiming for the right point on the opposite face of the work piece. I used this method to drill a 1/4" pilot hole about 15" long through a length of log. The pilot hole was for a 5" diameter hole saw. I was making a bird box and wanted a way to drill a 5" hole through the log. It was a slow job as the hole saw was only about 1 1/4" deep so I had to hack out the middle every 1 1/4"

Les.

[David LittlewoodParticipant @davidlittlewood51847]

Wolfie,

Source for long centre drills:

http://www.drill-service.co.uk/Product.asp?Parent=040240000000&Tool=16

No connection, just a satisfied customer. May not be the cheapest, but very fast service.

David

[JasonBModerator @jasonb]

They are a bit on teh steep side David, I get mine from J&L/MSC

1/8×3" is £3 or £7 for better quality vs your £9

1/8×5" is £5 or £10 for the better quality vs. your £29.00

J

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