Drilling into the end of a large threaded rod, centered, punched and
drilled starting at 1/8" worked up to 3/8". 3/8" is about 1/4 of the
way into the hole and quit cutting, Either I hit a hard spot in the
steel, or it got work hardened, I was using coolant, but not flood.

Swapped to a new and sharp HSS bit, no joy at all.

Suggestions?

I can:

1. Try a masonry bit, 3/8 is something I have in the shop.
2. Heat it with a plumbers torch and see if I can temper the hole.
3. Go get a TiN or Cobalt bit...

I need to finish the 3/8 and then drill it to 13/32nds, then tap, so I'm
close, but I'm worried about the tap and the hard spot too.

Any help would be great!

Stuart

Stuart Wheaton wrote:

Drilling into the end of a large threaded rod, centered, punched and
drilled starting at 1/8" worked up to 3/8". 3/8" is about 1/4 of the
way into the hole and quit cutting, Either I hit a hard spot in the
steel, or it got work hardened, I was using coolant, but not flood.

Swapped to a new and sharp HSS bit, no joy at all.

Suggestions?

I can:

1. Try a masonry bit, 3/8 is something I have in the shop.
2. Heat it with a plumbers torch and see if I can temper the hole.
3. Go get a TiN or Cobalt bit...

I need to finish the 3/8 and then drill it to 13/32nds, then tap, so I'm
close, but I'm worried about the tap and the hard spot too.

Any help would be great!

Stuart

Where did you get the TR? The stuff found in short lengths in the big
box stores is total crap and you have no idea what you'll find in it.
The stuff found in 10' lengths and not galvanized in the electrical area
next to the Unistrut is normally much higher quality and the stuff you
see hanging 300# transformers over your head.

On Wed, 12 Nov 2014 07:58:44 -0500, "Pete C."
wrote:


Stuart Wheaton wrote:

Drilling into the end of a large threaded rod, centered, punched and
drilled starting at 1/8" worked up to 3/8". 3/8" is about 1/4 of the
way into the hole and quit cutting, Either I hit a hard spot in the
steel, or it got work hardened, I was using coolant, but not flood.

Swapped to a new and sharp HSS bit, no joy at all.

Suggestions?

I can:

1. Try a masonry bit, 3/8 is something I have in the shop.
2. Heat it with a plumbers torch and see if I can temper the hole.
3. Go get a TiN or Cobalt bit...

I need to finish the 3/8 and then drill it to 13/32nds, then tap, so I'm
close, but I'm worried about the tap and the hard spot too.

Any help would be great!

Stuart

Where did you get the TR? The stuff found in short lengths in the big
box stores is total crap and you have no idea what you'll find in it.
The stuff found in 10' lengths and not galvanized in the electrical area
next to the Unistrut is normally much higher quality and the stuff you
see hanging 300# transformers over your head.

The lowest grade threaded rod, even from a reputable supplier
(McMaster calls it "low strength threaded rod"), machines like crap.
Grade B7 is made from 4140 and is only a bit more expensive in small
sizes. It's stronger, has good machinability, and better form and
finish on the threads. It may well be what's sold for use with
Unistrut.

--
Ned Simmons

On Wed, 12 Nov 2014 07:58:44 -0500, "Pete C."
wrote:


Stuart Wheaton wrote:

Drilling into the end of a large threaded rod, centered, punched and
drilled starting at 1/8" worked up to 3/8". 3/8" is about 1/4 of the
way into the hole and quit cutting, Either I hit a hard spot in the
steel, or it got work hardened, I was using coolant, but not flood.

Swapped to a new and sharp HSS bit, no joy at all.

Suggestions?

I can:

1. Try a masonry bit, 3/8 is something I have in the shop.
2. Heat it with a plumbers torch and see if I can temper the hole.
3. Go get a TiN or Cobalt bit...

I need to finish the 3/8 and then drill it to 13/32nds, then tap, so I'm
close, but I'm worried about the tap and the hard spot too.

Any help would be great!

Stuart

Where did you get the TR? The stuff found in short lengths in the big
box stores is total crap and you have no idea what you'll find in it.
The stuff found in 10' lengths and not galvanized in the electrical area
next to the Unistrut is normally much higher quality and the stuff you
see hanging 300# transformers over your head.


The cheap zinc plated stuff is mild steel and most likely couldn't get
work hardened if you tried, Do you have B7 rod? That's usually
black, and stamped b7 on the ends.

Use a drill pres if at all possible, to get enough pressure on the
drill to cut and not just rub.

Try 3/16" then 1/4" then 5/16" just to get past that spot. Without a
drill press you can get a lot more cutting force on a smaller drill.

Masonary bits are sort of dull from new, most likey will not cut steel
well. Hammer drill bits are blunt on the end.

HTH.
Remove 333 to reply.
Randy

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"Stuart Wheaton" wrote in message ...

Drilling into the end of a large threaded rod, centered, punched and
drilled starting at 1/8" worked up to 3/8". 3/8" is about 1/4 of the
way into the hole and quit cutting, Either I hit a hard spot in the
steel, or it got work hardened, I was using coolant, but not flood.

Swapped to a new and sharp HSS bit, no joy at all.

Suggestions?

snip

Silly question, but are you certain it's not stainless studding? That can
work harden if you back off pressure when drilling.

JB

On Tuesday, November 11, 2014 8:00:34 PM UTC-8, Stuart Wheaton wrote:
Drilling into the end of a large threaded rod, centered, punched and
drilled starting at 1/8" worked up to 3/8". 3/8" is about 1/4 of the
way into the hole and quit cutting, Either I hit a hard spot in the
steel, or it got work hardened, I was using coolant, but not flood.

Swapped to a new and sharp HSS bit, no joy at all.

If the workpiece is stainless, this is a familiar problem: heating
the drillbit causes the leading edges to dull (burn away, actually)
and burnishes a work-hardened patch. It could also be
a loose inclusion, and you are just spinning a button at the
bottom of the hole, not contacting the

It MIGHT help if you center-punched the bottom of the hole before
trying to cut again. Safe bet: start another hole. This piece may be ruined.

1. Try a masonry bit, 3/8 is something I have in the shop.
2. Heat it with a plumbers torch and see if I can temper the hole.
3. Go get a TiN or Cobalt bit...

Heavy-duty cobalt bits are a good solution (they stay sharp a lot
longer in heat-buildup cuts). Better, is to cool the tool (or cut
for a few seconds, then back out and brush the tip with a
lube). It might be a good idea to drill a smaller pilot hole (so the
threaded rod doesn't deflect) before putting the fullsize drill in.
If the alloy is work-hardening, you want to keep full pressure
on the cut at all times, or the drill will polish another hard dimple
instead of steadily removing the worked material.

On 11/12/2014 3:18 PM, whit3rd wrote:
On Tuesday, November 11, 2014 8:00:34 PM UTC-8, Stuart Wheaton wrote:
Drilling into the end of a large threaded rod, centered, punched and
drilled starting at 1/8" worked up to 3/8". 3/8" is about 1/4 of the
way into the hole and quit cutting, Either I hit a hard spot in the
steel, or it got work hardened, I was using coolant, but not flood.

Swapped to a new and sharp HSS bit, no joy at all.

If the workpiece is stainless, this is a familiar problem: heating
the drillbit causes the leading edges to dull (burn away, actually)
and burnishes a work-hardened patch. It could also be
a loose inclusion, and you are just spinning a button at the
bottom of the hole, not contacting the

It MIGHT help if you center-punched the bottom of the hole before
trying to cut again. Safe bet: start another hole. This piece may be ruined.

1. Try a masonry bit, 3/8 is something I have in the shop.
2. Heat it with a plumbers torch and see if I can temper the hole.
3. Go get a TiN or Cobalt bit...

Heavy-duty cobalt bits are a good solution (they stay sharp a lot
longer in heat-buildup cuts). Better, is to cool the tool (or cut
for a few seconds, then back out and brush the tip with a
lube). It might be a good idea to drill a smaller pilot hole (so the
threaded rod doesn't deflect) before putting the fullsize drill in.
If the alloy is work-hardening, you want to keep full pressure
on the cut at all times, or the drill will polish another hard dimple
instead of steadily removing the worked material.

M42 grade or solid carbide should do the trick. Solid carbide will
drill when red hot. And stay sharp after cutting through tough stuff.
I cut holes in lathe tool steel to make shaping cutters. Only carbide
would do that work.

Martin

On 11/11/2014 11:00 PM, Stuart Wheaton wrote:
Drilling into the end of a large threaded rod, centered, punched and
drilled starting at 1/8" worked up to 3/8". 3/8" is about 1/4 of the
way into the hole and quit cutting, Either I hit a hard spot in the
steel, or it got work hardened, I was using coolant, but not flood.

Swapped to a new and sharp HSS bit, no joy at all.

Suggestions?

I can:

1. Try a masonry bit, 3/8 is something I have in the shop.
2. Heat it with a plumbers torch and see if I can temper the hole.
3. Go get a TiN or Cobalt bit...

I need to finish the 3/8 and then drill it to 13/32nds, then tap, so I'm
close, but I'm worried about the tap and the hard spot too.

Any help would be great!

Stuart

Picked up a TiN bit in the AM, Filled hole with coolant, fired up the
drill press (which is what I did the original drilling in) and it cut
through the hard spot. Final drill and tap went without incident.

Material was a large threaded rod, about 1.25" diameter, likely metric
since we are fixing an English company's goofs, sourced from McMaster,
good quality, red ends, not stainless. I would say that the guy
ordering can be trusted to order good stuff, but then he only got me a
bottom tap, so I guess I can't say that.

Stuart