Enlarging deep hole in cast iron

[mark smith 20Participant @marksmith20]

Hi , Does any one know an easy way of enlarging 4 holes in cast iron from 18mm up to 20mm. Ive been using blacksmith drills and it taking forever and the drill is snagging all the time . The holes are almost 100mm deep . I can only use a hand drill . Any sort of special drill bits that work??

[mark smith 20Participant @marksmith20]

[Gordon WParticipant @gordonw]

Are you trying to open -up already drilled holes ? Very difficult by hand, I tried it a couple of days ago. Best I can think of is a 20mm concrete drill, maybe a bit of touching up on the edges. Other expensive methods will be suggested, depends on accuracy needed.

[mark smith 20Participant @marksmith20]

Hi Gordon, yes the holes are being enlarged on a mill base to hopefully mount some adjustable feet which are M20 threaded.

A masonary drill may be a good idea as there is more clearance on the sides which is one of the problems im having with the blacksmith drills.

[Brian WoodParticipant @brianwood45127]

Hello Mark,

You could try a core drill, they come with 3 flutes and tend to self centre where a two flute drill will have lost any ability to follow a centre path. Trying to guide a blacksmith drill freehand is pretty well impossible.

​I didn't say the method would be cheap though!

Much depends on how important the task is and whether or not any other alternatives can apply—like for example reducing the diameter of whatever is to go down the hole to suit the size it presently is.

Regards
Brian.

[JasonBModerator @jasonb]

Turn the M20 thread on the feet down to 18mm, you may just still have enough percentage thread engagement in the locking nuts

Edited By JasonB on 14/10/2016 17:21:54

[Michael GilliganParticipant @michaelgilligan61133]

Posted by mark smith 20 on 14/10/2016 16:25:11:

… the holes are being enlarged on a mill base to hopefully mount some adjustable feet which are M20 threaded.

.

Hopefully not to late with this suggestion: Have you considered tapping M20 instead ?

MichaelG.

[Clive FosterParticipant @clivefoster55965]

Plug the centre with something softer than cast iron, I've used both wood and alloy, and run a hole saw in. Pre-drill the plug for the hole saw centre drill and either use the centre drill as a simple location pin or replace it with a plain pin made for the job. You will probably need to either knock the centre support through a bit after a 1/4" or so to give swarf clerance or break up the top section to achieve same result.

I've done the deed with both wood and alloy plugs. Were I to do it again I'd probably use a wood plug with oversize guide pin and trim down for swarf clerance using one of the flat round counterbores sold for wood work. Easy for me to say as I have a set of such counterbores. Lidl special, got for occasional use and have proven well worth the price.

An alternative to plugging the centre is a Starrett "Ooops" (yup they really call it that) hole saw carrier made to use when you have made a hole too small. It puts the too small holesaw inside the correct one so it acts as a guide. I have one and used it to enlarge holes in sheet steel and see no reason why it wouldn't work for you If your existing holes are reasonably round.

At that depth you may need to put an extension shaft on the hole saw.

Best result I got with this technique was re-furbishing the seriously oval plain bearings on a well worn Southbend countershaft. These run the steel shaft direct in the casting and last well providing the user remembers to put oil in the oil cups as the design includes a thick felt distribution wiper in a groove on the upper surface beneath the oil cup. No felts, no oil cups and over 1/8" ovality on the worse side of mine. Using the plug and holesaw technique I was able to get both sides out to a sensible dimension and close enough in line to line reamer with a kingpin reamer. The shaft even came out square to the base. I suspect I got a bit lucky but the technique does work.

Clive.

Edited By Clive Foster on 14/10/2016 17:15:49

[Steve SharmanParticipant @stevesharman33815]

How about one of these ?

Steve

Edited By Steve Sharman on 14/10/2016 17:27:57

[not done it yetParticipant @notdoneityet]

Personally, I would not even contemplate enlarging four 18mm holes by 2mm for a depth of 100mm! I would be looking for an alternatve method of fitting adjustable feet (how many are actually required?). Seems to me, at first glance, to be a free-standing item where shims might suffice?

Edited By not done it yet on 14/10/2016 17:55:28

[mark smith 20Participant @marksmith20]

Thanks for all the replies, i have managed to get three of them drilled with the blacksmith drill (re sharpened several times as it is only cutting on the edge) ,my arms are killing as the drill wasnt too happy and ive rapped my knuckles a few times when the drill snagged.

I know i wont be trying this again in a hurry.

Problem i have now is the drill that has gone through on the last hole has jammed in the hole. it is through around 1" below the mill base but i think im going to have to raise the mill and knock the drill through to get it out..

I know i could use shims instead of feet but feet look nicer!

I did contemplate reducing the shaft diameter of the m20 feet but would have had to have bought a die to thread it , i didnt think i would have trusted taking off the 2mm from the shaft and using any remaining thread left .

[mark smith 20Participant @marksmith20]

These are the feet im fitting, they were retailing at RS onLine for around£50-£60 for each foot plus VAT but the manufacturer is selling them off on ebay for £25 for four including postage, a deal i couldnt resist. Rated at 350 kg -400kg per foot. They are still selling them ,also in other sizes.

Edited By mark smith 20 on 14/10/2016 19:45:47

[Davey JParticipant @daveyj]

Tried to find these on EBay but without luck. Please would you be kind enough to post a link? Just what I need for my, new to me, lathe. Cheers, David

[mark smith 20Participant @marksmith20]

Hi David they are available here , its Nu-tech engineering who are the sellers. They have M10,M12,M16 and M20 available in this style of vibration dampening feet. Also despite what the shipping says mine came by 24 hr courier next day.

**LINK**

Edited By mark smith 20 on 15/10/2016 13:02:31

[mark smith 20Participant @marksmith20]

On a slightly different note im busy jacking the mill up 1/2" at a time with dozens of blocks of wood and breeze blocks . Not much fun as i have no lifting gear and it weighs 3/4 ton, i have around 2 " to go.

[HopperParticipant @hopper]

Milling machine mounted on feet, not bolted down to the floor?

I gather from the size of the feet and holes this is a large machine. And they tend to be top heavy, and lopsided. Then add a heavy dividing head at one end of the table, with a heavy job attached, wind table to the far end of its movement. Then you are yanking on the spindle drawbar hex at teh top of the machine, brace yourself on the end of that table to reach up just that bit further, and… Whoa. Stand back.

I would be bolting that machine to the floor.

[mark smith 20Participant @marksmith20]

They are actually quite stable on feet ,if anything the feet are overly large for a bit of safety. Its the same size as a Deckel Fp1 so not that big as milling machines go and certainly not as top heavy as a Bridgeport type mill.

[Davey JParticipant @daveyj]

Mark, many thanks. New feet on their way.

Cheers.

David

[mechman48Participant @mechman48]

A bit late but have a look @…

**LINK** … fixed mount £4.60 ea.

George.

[mark smith 20Participant @marksmith20]

Finally got the feet in ,need to level it tomorrow but its rock solid even before i do that. I like that with the large feet there is quite a bit of adjustment so i can get a comfortable working height.

There was a 24mm difference in the floor between the front right and back left corners of the mill base. So the floor was miles out of level.

Also because i can raise it ,it gives easy access to a pallet truck if i ever need to move it.

Edited By mark smith 20 on 15/10/2016 19:18:53

[HopperParticipant @hopper]

Posted by mark smith 20 on 15/10/2016 19:16:30:

 

There was a 24mm difference in the floor between the front right and back left corners of the mill base. So the floor was miles out of level.

Also because i can raise it ,it gives easy access to a pallet truck if i ever need to move it.

 

Edited By mark smith 20 on 15/10/2016 19:18:53

LOLz, yes you would have fun trying to bolt down to that surface in the conventional manner.

Apparently, I'm told, a lot of home shop guys don't bolt their mills down. I guess I'm more used to industrial production machinery  where the saying is that it's no good making equipment foolproof, it has to be idiot-proof. But you probably won't have many forklifts screaming past at full tilt accidentally catching a tine on the end of the table etc.  The FP1 should be a great little machine for the homeshop. I'm envious. (Struggling with my MYford vertical slide this morning. Every time I use it I swear there is a new mill in my near future…)

Edited By Hopper on 16/10/2016 02:43:46

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