Is it normal for lathe tailstock drill to lift up when contacting work?

[woodchucker]

edit: older thread, sorry.

 

[Dan Krager]

B2, I had an old Sears Roebuck house that was hard plastered. After living there awhile, I finally realized what the molding sticks in the attic were all about. In the old days, it was not wise to drill holes in the plaster because of the damage done. Instead, a "picture hanging molding" was installed around the ceiling about 1/4" below the ceiling. That provided a continuous rim to hang pictures from hooks made to match the profile of the molding top. Pictures could be hung and moved about at will...no holes. Just an FYI in case you didn't know....
DanK

 

[B2]

Hi Dan,

Thanks for the suggestion.

Yes, I am familiar with the wire and hook system as it is used at a lot of museums. But my wife vetoed it. In my house the outside walls have the 1 inch thick hard plaster applied directly to terracotta style tile blocks which seem to have a lot of metal oxides in them making them very very hard to drill into. Getting a screw to stay in the hole, requires a harden cement screw. But it works. On the outside of the block are bricks. This makes the total wall thickness about a foot.

 

[Janderso]

Hi Dan,

Thanks for the suggestion.

Yes, I am familiar with the wire and hook system as it is used at a lot of museums. But my wife vetoed it. In my house the outside walls have the 1 inch thick hard plaster applied directly to terracotta style tile blocks which seem to have a lot of metal oxides in them making them very very hard to drill into. Getting a screw to stay in the hole, requires a harden cement screw. But it works. On the outside of the block are bricks. This makes the total wall thickness about a foot.

Your winters are much colder than we have in Northern California.
We have 2x4 walls with R19 insulation, one inch of styrofoam, then stucco. It works very well. I have 21” of blow in insulation in the attic as well.
How does the one foot wall perform as insulation ?
I know the closed foam spray is used in your part of the country.
Just curious.

 

[B2]

It doesn't perform well at all, as it is almost, essentially, solid stone. While rock does not conduct well it is not as good an insulator as restricted air. The house was built in 1930. There was no insulation back then. Modern homes are properly insulated. However, more importantly than insulation are the leaks and the windows.
I would never use foam in the walls. In case of fire this stuff decomposed into poisonous gases. Stick with the fiberglass.

 

[machinistnoob]

As a machining hobbyist and a not-retired person who works long hours often out of town, I think it is safe to admit that I spend more time watching machining videos on YouTube than I do actually machining. Most often in bed when I'm supposed to be sleeping but the ol cranial flywheel can't be stopped.

One thing I notice in (most?) Of these videos is when people bring a drill bit into the work, it lifts up. If I'm not mistaken this means the tailstock is not on center (worn ways?) and the hole will not be straight. But they don't seem to care or ever acknowledge it happening.

I've noticed other things, what I consider to be an odd side effect of the internet: "Trends" in videos I assume are caused by Youtube-educated youtube-instructors perpetuating oddities. Like how so many people refuse to run a bead of weld. Everything is a series of zap-zap-zap like they they're applying concepts from auto body repair to 1/2" plate.

I'm wondering if that's what this drill-lifting thing is, or if it really doesn't matter, and that's why so many people post videos unabashedly showing close-up footage of it happening over and over and over.

Here is a great one watch and maybe shed some light on the situation.

 

[Parlo]

Here is a great one watch and maybe shed some light on the situation.

Have a think about the quote regarding the 1/32" deflection a 1/4" drill can deflect until it is at least 3/4" in the hole. Is it really possible?

 

[Jake M]

Have a think about the quote regarding the 1/32" deflection a 1/4" drill can deflect until it is at least 3/4" in the hole. Is it really possible?

Absolutely. Not only "possible" but quite achievable if you're not working proactively. Go back to the beginning and look at the white board part. He's not implying that the hole comes out a thirty second oversize, but that the thirty second deflection is how the the hole gets two thousandths oversized. He's going to a bit of an extreme there to make a perfect* hole, but just watching the feed in is required. Drill bits are very imprecise. Most drilled holes do come out with a bit of a funnel on top. And not quite round. And not quite on point at the back of the hole.

* I say perfect, but that's not the case. Any time you think something is perfect, it means you need better measuring tools. Nothing is perfect.

 

[Parlo]

Absolutely. Not only "possible" but quite achievable if you're not working proactively. Go back to the beginning and look at the white board part. He's not implying that the hole comes out a thirty second oversize, but that the thirty second deflection is how the the hole gets two thousandths oversized. He's going to a bit of an extreme there to make a perfect* hole, but just watching the feed in is required. Drill bits are very imprecise. Most drilled holes do come out with a bit of a funnel on top. And not quite round. And not quite on point at the back of the hole.

* I say perfect, but that's not the case. Any time you think something is perfect, it means you need better measuring tools. Nothing is perfect.

Once the drill has only penetrated 1/8th of the 3/4” lead, it then has two opposing 45 degree arcs, this is now the total possible land contact. The maximum movement now possible once these arcs have been established is now only 0.0014” at only 0.094” deep! This potential movement continues to decrease as the potential land contact increases. Then until only 1/4 of the lead depth is reached ( 3/16” ) two opposing quadrant arcs are formed. The total land contact at this depth is now 50% of the diameter. At this depth the maximum deviation off centre at 0 and 90 degrees is now only 0.001” as the hole is 0.002” bigger than the drill.

In summary:

Although there is theoretically 0.0158” of movement with an infinitely small contact area at the very start of the full diameter cut. This quickly continually reduces to a maximum deviation of +/-0.001” at only 0.1875” deep. This is because the demonstration does not consider the ever increasing potential land contact.

 

[machinistnoob]

Have a think about the quote regarding the 1/32" deflection a 1/4" drill can deflect until it is at least 3/4" in the hole. Is it really possible?

Yes. His approach is on the the pedantic side but it is necessary for precision. Furthermore, he addresses the dynamic nature of drilling a hole. Whether using a hand drill or precision equipment. It's all the same.