Todays Project - What did you do today?

[stevec]

(02-15-2014, 08:54 PM)PixMan Wrote: It seems the cutting pressure with a .010" deep (per side) pass was a bit too much and it started slipping in the chuck. Because it was following the previous passes, the tool never left it's path so no damage there.

I'm having a little trouble understanding that the workpiece slipped in the chuck but the "tool never left it's path".

Good job on the snowblower repair/improvement.

[PixMan]

What I mean it that the threading insert seemed to stay within the path of the three previous passes.

If a part you're threading slips in a chuck that's driving it, the most common failure would be that the workpiece stops and the carbide shatters. In this case it sounded like a tiny bit of chatter, and in the next instant I noticed the end of the work had come away from the live center. That's when I retracted the tool and stopped the process. All I can assume is that there were very tiny, unnoticeable stops to the workpiece that for some reason didn't catch and didn't chip the carbide insert.

[stevec]

OK Ken, I was wondering, when the piece slipped in the chuck the still advancing tool pushed the workpiece further into the chuck.
That makes sense and good luck for you.
All's well that ends well.

[PixMan]

This sets me back a week on the project. I'm going to cut another piece of stock, neck down a 3/8" to 1/2" section behind where the thread goes (the Ø20mm section) and mill flats on the last 1-1/2" to clamp in the chuck. I'll do four flats at 90º apart and for the first time, mount my 12" 4-jaw independent chuck so I can be sure that end is true. Now firmly clamped, I need to upgrade the threading tool.

I looked at what I'd threaded and saw a problem. It was clearly pushing and though chip control was perfect it wasn't cutting right. Checking the helix angle, a 1-1/4-5ACME has nearly 3º of lead angle. The standard lay-down holder accounts for 1 to 2 degrees of lead angle, so I need to get a YE4-2P or YE4-3P anvil for the holder. Since it's a borrowed holder, I'm just going to buy my own and get the additional anvil with it. That should make threading this MUCH easier, and make a high quality thread form.

[Old Iron]

I know this should be in gun smithing forum but it was my project for today
Its only a AR15 lower this is the forth one I've did.

Paul

[PixMan]

Was that made from a solid block, or a casting you buy and have to finish? Either way, looks good and I know they're a lot of work and a few special tools are required. Doesn't take but a moment of inattention to make it junk!

[Old Iron]

It was a forged 80% receiver, I do have a solid one and I'm in the process of making the plates to hold it in the vise.

Yea it only takes one oops and its junk, Been there done that and I learned not to have anyone around while your doing them.

Even at 55.00 it is expensive mistake. I've build one in 5.56 and one in 7.62X39 this one will be a pistol in 7.62X39.

Paul

[PixMan]

Neil came over today with a little "rush job". As I didn't get the threading tool I'd ordered to work on Darren's parts because UPS reported a "train failure" coming from Michigan to Massachusetts, I was going to work on Neil's remaining parts. He showed up with a cast aluminum motorcycle wheel that he was trying to upgrade to a right angle Schraeder valve.

The hole in the wheel was just a little too large for the o-ring to seal, so we thought to bore (and counterbore) the existing hole to press in a step-down bushing. As necessity is the mother of invention, we fashioned a way to clamp it to the side of my Alliant milling machine. I quickly made a large aluminum "washer" to cover the bearing while allowing a 3/8" stud to pass through the 14mm bore. Luckily I have a bag full of 3/8-16 threaded T-nuts and found one that fit the slot normally used for the table stops. It worked a treat!



I wish I'd thought to lake more photos. We first made the stepped bushing far too long, it would have stood proud of the mounting surface on the inside of the wheel. So then I quickly made a split aluminum bushing to hold the stepped press-in bushing in the lathe, reaching over the larger shoulder O.D. to clamp on the smaller "press fit" diameter. Of course Murphy was in the shop haunting us all day, so we miscalculated something and somehow cut it a millimeter too short.

Of course we didn't know it would be too short until after we'd pressed the bushing into the wheel with a permanent Loctite product. (I had also made a quick, stepped press tool to insert the bushing.)

No way to press it back out from inside the wheel anyhow, so we straightened out the milling machine and deftly milled the boss where the Schraeder valve mounts. The new smooth-milled surface will give a better sealing surface for the o-ring on the valve anyhow.

It all took about 4 hours from start to finish, but it's PERFECT....as long as it holds air. I'll ask Neil (expat) to get a finished photo of the work.

[Mayhem]

Nice work Ken. Ingenious set up too.

[Hawkeye]

I had noticed that my big drill press wasn't giving me vertical holes, so today was the day to try to true it up. The table had been finished with a pass from a very large flycutter or face mill - something around 16" diameter judging from the tool marks. Checking with a square showed that the table needed to 'nod' to true up front to rear.

Since I now have a lathe that's big enough (the table is almost 14" diagonally), I decided to face the table. Because of the large diameter, I needed to use carbide at the slowest lathe speed to get an acceptable cutting speed for the cast iron table. The brazed carbide cutter has a 1" shank and is very solid - necessary due to the interrupted cuts.
   

You can see the original tool marks, especially on the rim at the top.
   

As shown, the centre hole was a bit off centre. A touch-up with a boring bar made short work of that.
   

Shimming with aluminum foil at the top of the table support arm gave enough nod to level the table. A much nicer finish than the original.