Drilling Cast Iron

[Catalyze]

Greetings!
I need to enlarge the lead screw hole in my dynamic jaw on my vise (small hobby size Columbian). The hole is 11/16" now and I would like to enlarge it to 13/16" to fit the OD of a bronze bushing that I have. The purpose is to close up the oval wear that the lead screw has caused over many decades. Can I just use a normal 13/16" drill bit in my drill press? Do I drill at a very slow speed or ?? Any tips would be appreciated!
Craig

 

[toxicz28]

Greetings!
I need to enlarge the lead screw hole in my dynamic jaw on my vise (small hobby size Columbian). The hole is 11/16" now and I would like to enlarge it to 13/16" to fit the OD of a bronze bushing that I have. The purpose is to close up the oval wear that the lead screw has caused over many decades.

Can I just use a normal 13/16" drill bit in my drill press?
Go with good metal bit, but othwise, YES!
Do I drill at a very slow speed or ??
As slow as you can and let the drill press do the work Any tips would be appreciated!
Craig

You're pretty much right on track.

 

[metal1313]

slow speed, slow feed, good sharp bit and plenty of cutting fluid should work for you great.

 

[rsanter]

actually a drill bit may not make the correct size hole. it is best to drill the next smaller size and then ream to the desired size so you can get a good press fit into the hole. with an ovalaed hole I can just about guarantee you will get enough wobble in a bit that you will have an oversized hole that is not quite round

bob

 

[Jim Johnstone]

Make sure you have the workpiece very rigidly held, preferably in a milling vice or use a bunch of clamps. Also do yourself a favour and call a tooling supplier and get a price on a core drill to do it with. Core drills are meant to enlarge existing holes without wandering too much, and were originally developed for use enlarging core holes in iron castings.

 

[larry_g]

I have to agree with Rsanter here. Drilling with a twist drill in an oval hole will cause lots of grief. Ideally you would do this on a mill with a boring head. A twist drill should be cutting evenly on each lip to cut straight. In an oval hole you are going to have one or the other cutting edge cutting more than the other and that will pull the bit to one side making the hole wonky or breaking the bit.

lg
no neat sig line

 

[Steve from Socal]

I agree with Larry; a boring bar, on an oval hole you need to pick up the original center and bore with out induced error.

Steve

 

[justanengineer]

Drill then bore. If you have questions about the correct speed or feed, there are a ton of charts on the internet. If you find youre having problems with the drill dulling quickly, you may be feeding it too slowly - common mistake. Your vise very well could be white iron too...damn near unmachineable.

 

[toolsd]

Going from oval back to round, and needing it a certain size, and in the right place, I believe the ONLY way to do it is a boring bar in a mill or lathe. A horizontal mill is going to be the easiest.

With a twist drill, you could easily wind up 20 thou over sized, and 3 or 4 times that in a different location and not coaxial.

Once you do it though, should you ever need to replace the bushing, it will be very easy.

Tools

edit: Jim has a good point I missed in the first reading, an annular cutter would work, although you're not necessarily going to hit the exact size required for a press fit on your bushing. May need to knurl it a bit and use bearing retaining compound to hold it in place.

Now, calling a supplier for one is not gonna be fun, a 13/16 Rotobroach (a common brand of them) is probably eighty bucks new... Search ebay, might find one for about $25. You'll have to meticulously locate exactly where you want the hole and have it VERY well held. Using a standard drill press isn't the best method, though it might work. The shank will likely be 5/8 or 3/4, which might be a problem.

 

[metal1313]

this is just a small vise, i dont see the need for accuracy in the thousandths. the vise prob had atleast 1/16 of play in all directions when new

 

[larry_g]

this is just a small vise, i dont see the need for accuracy in the thousandths. the vise prob had atleast 1/16 of play in all directions when new

The accuracy is needed because the bushing should be a press fit so it doesn't fall out. Just because you can't see it doesn't mean it is not there.

lg
no neat sig line

 

[A_Pmech]

As Steve and Larry have mentioned, drilling will get you nowhere. To establish true position, size and create cylindricity, it must be bored with a boring head. If you want to put the jaw and screw in a flat rate box and ship it up here, I'll bore the jaw and press in the bushing at shop rate.

 

[Jim Johnstone]

As Steve and Larry have mentioned, drilling will get you nowhere. To establish true position, size and create cylindricity, it must be bored with a boring head. If you want to put the jaw and screw in a flat rate box and ship it up here, I'll bore the jaw and press in the bushing at shop rate.

Awesome offer, I'd seriously consider this if I was you.

 

[rsanter]

here is a trick
you dont actually need a boring bar to do the job, you can use an end mill (slightly undersized) because it will cut on the end as well as the sides
ream to size and you are set
this can be done in a mill or a lathe or even a really good drill press

bob

 

[mrb]

is this something you would use a chucking reamer for?

 

[larry_g]

is this something you would use a chucking reamer for?

NO. A chucking reamer is to enlarge a predrilled hole that is straight and on position to the correct size. The OP's problem here is that he does not have a round hole to start with. The boring bar will cut the oval round and on position incase only one side of the hole is worn. A chucking reamer like a twist drill will follow the path of least resistance. Have you ever tried to drill a hole with the bit overlapping into another hole? The bit just walks into the open area. A reamer will do the same thing and needs to have an equal amount to cut all around the hole or it will wander.



lg
no neat sig line

 

[Catalyze]

You folks are scary with knowledge! Let me take a look at my options and get back to this thread in a day or two.
My drill press is a Craftsman 15" and I have a 6" Palmgren Cross Slide vise to clamp with. Don't even make fun of the Palmgren.....I bought it by looking at a smaller size and then dropping down a line or two when I hit the Order Now box. It did seem a bit heavy when it arrived. LOL
Craig

 

[Kevin54]

All you need to do is drill it and preferably drill it undersize then ream it to size. A few drops of oil when you start the hole and you will be fine

 

[Vicegrip]

this is just a small vise, i dont see the need for accuracy in the thousandths. the vise prob had atleast 1/16 of play in all directions when new

Agree.

The accuracy is needed because the bushing should be a press fit so it doesn't fall out. Just because you can't see it doesn't mean it is not there.

lg
no neat sig line

Drill the hole. Test fit the bushing and spin sand the bushing as needed to get it close then press it in. Fix something else while holding it in the freshly fixed up vice. Double win.

We are talking about an old vice here.

 

[nate379]

ARGH!! haha

You sound like my brother. Talk to him about making a hole on a piece of steel and I got a 25min lecture about all these fancy reamers, hole thingama bobs, bore guages, etc, etc, etc.

I was like... yeah that's nice but I'll just bust out the torch and make the hole if you don't shut up

Most of my stuff... +- 1/8" is being fairly ****. Him... +-0.0005" or sometimes less.

As Steve and Larry have mentioned, drilling will get you nowhere. To establish true position, size and create cylindricity, it must be bored with a boring head. If you want to put the jaw and screw in a flat rate box and ship it up here, I'll bore the jaw and press in the bushing at shop rate.

 

[wiz56]

Larry G and the others are right about the boring........if you attempt to do this on a drill press, you are going to smear your lipstick. I know not everyone can afford a mill, but a drill press, in my opinion, is an accident waiting for a victim. If you attempt this with a drill on top of that, you will end up with a horrible mess and possibly a trip to the E.R. You couldn't clamp it down good enough and if you did it would break the bit. If you do have a typical drill press it is way too fast for this job. A bit that size going into an existing hole if it was round should only be going about at most 100 rpm and slower if you could. If it is a cheap vise the cast iron will tend to grab the sharp bit and either stall the machine, fling the part on the floor or any combination of blood letting situations you could imagine.

But me I'm just a grumpy old machinist, with all my fingers!!

If you insist on using a drill press....do yourself a favor and make yourself a foot switch for the dang thing, so at least when it does fling something at you, all you have to do is lift your foot to shut it off.

 

[RAYJAY]

slow speed, slow feed, good sharp bit and plenty of cutting fluid should work for you great.

would not use cutting fluid or oil on cast iron and on old cast watch out for the sand holes ....

 

[Steve from Socal]

Besides the drill press being the wrong machine for the job and a drill bit the wrong tool, to restore the casting so the vise will work properly, the screw must be concentric with the nut. In order to locate the bushing bore concentrically the hole should be single pointed with a boring bar, yes you could use an annular cutter but sizing the OD to the bushing will be difficult. Any cutting tool that follows the existing hole will follow any error in location, if the screw is out of line a few thousandths it will be hard to turn or won't turn at all depending on the slop in the beam.

A boring bar will generate a true bore to the size desired with the least fuss and muss, one set up and no special tools. You can even leave a counterbore step in the bottom if you want. While it may not be what you wanted to hear it is the most reliable method to repair the vise Drilling and reaming will give you a hole but where it is and how well it aligns withe the other pieces of the vise are a guess at best.

Steve

 

[Jim Johnstone]

know anyone with a CNC instead of just a knee mill? If I had it here at work, I'd use a CNC mill, with a smaller diameter end mill, and just machine the hole, rather than try to drill/bore it.

 

[Catalyze]

It is looking like it's machine shop time. I will check around and see if anyone in this dairy/farm part of the world is willing to do it. If not......then it's flat rate Priority Mail box time to one of our learned machinists on this list. Thanks all for the tips and education in the project!
Craig