Author Topic: Drill a long 30mm hole through a 340mm piece.  (Read 4938 times)

Offline NeoTech

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Drill a long 30mm hole through a 340mm piece.
« on: February 06, 2013, 03:03:45 AM »
I have this piece of steel from a old hydraulic piston.
I need to put a 30mm hole through it.. And well i dont have a 30 x 340mm drill.. So any1 has a good idea how you put a whole through that piece of steel (thats is hard as hell). =)
Machinery: Optimum D320x920, Optimum BF20L, Aciera F3. -- I have not failed. I've just found 10,000 ways that won't work. http://www.roughedge.se/blogg/

Offline awemawson

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Re: Drill a long 30mm hole through a 340mm piece.
« Reply #1 on: February 06, 2013, 03:16:31 AM »
You need a 'gun drill' - google & eBay will sort you out. If you are feeling adventurous you could make one by brazing a suitable carbide drill tip to a piece of decent steel.
Andrew Mawson
East Sussex

Offline AdeV

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Re: Drill a long 30mm hole through a 340mm piece.
« Reply #2 on: February 06, 2013, 04:23:37 AM »
A gun drill would be ideal, but very expensive, especially since you will almost certainly need to buy the coolant unit to go with it.

If the metal is too hard for HSS, then you will want an insert drillbit -search ebay for carbide spade drill, you will see the sorts of inserts on offer. You would need to buy or make a suitable holder; the former is likely to cost a few quid, the latter less so, but you need to worry about accuracy...

Is the metal hard all the way through? I've never tried machining a hydraulic cylinder; I do have some pins which would have been used in bosses at either end of a hydraulic ram, and they are as hard as Vinnie Jones on a particularly hard day - I've burnt a couple of carbide tips out trying to shave them to size; they do, however, tend to be softer in the middle, such that an ordinary HSS drill bit works just fine. Until you hit the hard layer, that is, then it all just goes to hell very quickly...

Cheers!
Ade.
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Location: Wallasey, Merseyside. A long way from anywhere.
Occasionally: Zhengzhou, China. An even longer way from anywhere...

Offline awemawson

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Re: Drill a long 30mm hole through a 340mm piece.
« Reply #3 on: February 06, 2013, 04:57:31 AM »
These are the sort of tip I was advocating brazing onto a steel bar:

http://www.ebay.co.uk/itm/30MM-28MM-17MM-CNC-SPADE-DRILL-INSERTS-/271136703664?pt=UK_Home_Garden_PowerTools_SM&hash=item3f2101c4b0


With a gun drill, the clever bit is getting it drilling accurately to start with, as a bit of wobble in the first 10mm or so may not notice, but when you are 300 mm into the stock it may be coming out of the side wall!

Start by accurately boring a few cms of your stock to 30mm, introduce the home made gun drill and start drilling. It is advangateous in some circumstances to have a guide collar on the reduced diameter shank of the drill to keep things from flexing, but it makes swarf clearance a chore.
« Last Edit: February 06, 2013, 10:24:36 AM by awemawson »
Andrew Mawson
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Offline vtsteam

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Re: Drill a long 30mm hole through a 340mm piece.
« Reply #4 on: February 06, 2013, 08:46:00 AM »
I used to build wooden boats for a living. When we needed to drill long holes through timbers for say keel bolts and drifts  we would mark off the individual timbers all around for the hole location, then drill each timber from both sides so the holes met in the center of the timber. The marks helped aim the drill, since these timbers were too big for the drill press. This reduced the tendency for the hole to wander to one side. The same could be done in metal work in a pinch, by drilling the hole with short tools to meet. The hole should be substantially smaller than the finished size so you can clean it up with a boring tool run between centers with the part on a boring table to bring it into true position and diameter. Once you have a through hole you can bore, so the main point is to get that start.

The second problem of hardness and cost might be solved by using a a carbide masonry bit. It may not be ideal, but if you can drill at all with it through the particular problem material you have, that's good enough. Remember, the first hole is not to finished dimensions -- it's just clearance for a boring tool.

Finally, if cost is prohibitive for even a between centers boring tool, you can easily make one from a piece of plain steel rod and add a small carbide insert.
I love it when a Plan B comes together!
Steve
https://www.youtube.com/watch?v=4sDubB0-REg

Offline NeoTech

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Re: Drill a long 30mm hole through a 340mm piece.
« Reply #5 on: February 06, 2013, 09:48:43 AM »
Masonry drill is something i got suggested from different sources. they need to be sharpen in a different angle, and well go really damn slow..
Anyone tried that ?? But yes, drilling to a undersize is what i aimed at anyway, but never used a between center boring bar. Need to read upon that. =)
Machinery: Optimum D320x920, Optimum BF20L, Aciera F3. -- I have not failed. I've just found 10,000 ways that won't work. http://www.roughedge.se/blogg/

Offline vtsteam

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Re: Drill a long 30mm hole through a 340mm piece.
« Reply #6 on: February 06, 2013, 04:13:11 PM »
Something like this -- doesn't have to be a round bit, could be a square lathe bit, or just an insert. basically a piece of rod with center drilled ends and a tool bit somewhere near the middle.

Also, this one is sticking out rather far. Could be just barely showing and still work. Also the baar here is rather heavy. You probably don't want to drill any bigger hole to start with than you have to, so the boring bar will be relatively small diameter. 5/8" seems about right for your workpiece. You will need to drill a 3/4" hole for that. You will probably want to step drill the hole to start with up to that size.

Good Luck!


I love it when a Plan B comes together!
Steve
https://www.youtube.com/watch?v=4sDubB0-REg