Another Broken Tap

[rake60]

I was making a crankshft for a current project tonight and had it all done
except for tapping the hole for the crank pin. Almost through it and,
SNAP. :x

There was enough sticking out to get a hold of with the vise. That quickly
crumbled away. So it was time to drill it out. This piece of a broken 1/8"
solid carbide end mill, (If they can make it, I can break it!)

It just has a shallow chisle point ground on the end. Nothing
critical about the the shape. It's harder than the HSS tap and it drill
through it easily.

 

[gt2ride]

I have been breaking #70 drill bits. How do you drill holes with small bits with out braking them?

 

[rake60]

When I'm drilling with the small bits I push them up into the chuck so
there is just enough sticking out to reach hole depth + about 1/8"
That may not be a proper practice but it works for me.

Another important thing is the pecking depth. Especially on aluminum
because it's gummy and will stick to the bit. Drill .040-.050" at a time
backing the bit out between pecks to clear the chips from the hole.
Some light oil will help on steel or brass. For aluminum it's better to use
some tapping fluid made especially for aluminum as a drilling oil.

Hopefully we'll get some other ideas here.

 

[gt2ride]

Thanks Rake 60 I will give your tips a try. They only cost .43 but I still do not like braking them.

On your screw slotting method. I use to use a 1/16 end mill but I have bought an arbor and slotting saw. That works better.

 

[Bogstandard]

Hi Mem's
I see you are having tap breakage problems.
If I break a tap while building it is a major issue, mine usually go blunt and have to be thrown away.
The main reason for tap breakage is your own hands, especially in the smaller sizes, you are actually snapping the taps yourself by putting too much side pressure onto them, plus how many times have you tapped a hole and it ends up off square.
I either use the tailstock in the lathe if the part is tapped central to a hole just bored or I use a tapping fixture which can be bought for about £35 UK, this solves 99% of tap breakage problems. To see what one looks like go here
http://www.arceurotrade.co.uk/index.html?target=front.html&lang=en-gb
and do a search for ' hand tapping fixture '. I made my own from an old small surface plate and odd bits around the workshop, the only thing I had to buy was a good jacobs chuck, and the surface plate can still be used for marking out.

John

 

[wolfpackcpl]

Also when using small twist drills, wind the RPM's wide open.
Most drill presses and milling machines will not run fast enough for a tiny drill.
Make sure you continually clear the chips from the hole.
Do not be stingy with the lubricant either. They make it every day.

 

[gt2ride]

I did it. I drilled seven holes with a # 70 .028 drill bit. Into a .062 drill rod. Did not brake the bit this time. Thanks for the help. I had the old Bridgeport spinning as fast as it would go.

 

[rake60]

I like your tap guides Ian. I'll have to make a few myself.

 

[Canyonman]

Ian,

I like that little tap holder you got there! Did you make it? What Company makes it?

OR

Might you be willing to draw up just a quick blueprint?

TIA, Ken

 

[mklotz]

If you want to avoid breaking small taps, make yourself some guided tap holders,

and do the tapping immediately after you've drilled the hole so you can use the mill/drill press as an oversized tapping machine.

Each of the ones shown has a free-running pin in the top that goes in the drill chuck. The two on the left are for taps up to 4-40. With little leverage available from the finger-operated design, it's hard to overtorque the tap and one has a very sensitive 'feel' for what's happening. The second from left and far right incorporate simple sleeve 'collets' so they can be used with various size taps. The far right is very low profile so it can be used on a round column mill drill without the need to move the head.