Turning Bolts with HSS?

[ErichKeane]

Chilled Cast Iron is incredibly hard, even when turning freash castings you normally need to cut deep enough to get under the 'skin'. Hard spots in Cast Iron will damage Carbide even the grades made specifically for it.

I'm not what it is actually. It is the backing plate to a Polish 3 jaw chuck. I bought it advertised as 'plain back', but it had a small L-type taper (but no threads) in what looks like the backing plate. The backing plate has some cutouts for the spinning gears (which I just realized are unnecessary, since they are actually captive in the middle) so I thought I should keep it. However, it was for too small of an L taper (I'm L1) that I feared would get in the way. SO, I wanted to cut it out.

I was using one of my india-precut sets to cut the inside taper out, and it worked well for a while. Then, the bit just started grinding off. I ground a new bit, and the same happened. Perhaps i could have hit a hard spot? Who knows!

 

[pontiac428]

I'm not what it is actually. It is the backing plate to a Polish 3 jaw chuck.

Don't feel bad. I had a similar experience with a Burnerd made backing plate. I had a similarly hard time with that. The facing was one thing, but re-cutting the whitworth mounting threads to UNC threads cost me two taps. Basically, the material was so hard that I now have two formed whitworth taps in my scrap bin. I had no idea cast iron could be so tough.

 

[ErichKeane]

Hmm... So I may have figured it out.

I have a medium carbon steel rod (~9" by 5" long) that I'm trying to use as an adapter plate for my backing plate to my 4 jaw. Side note: L1 tapers are HUGE and make anything but huge chucks a pain to mount...

Anyway, I had the same problem, my HSS worked for a little while, then I couldn't get it to last more than ~3 seconds. I switched to some carbide from the junk drawer, and was able to face and turn the outside.

First hint: I ended up finding a cheap RPM gauge, and discovered that my lathe is actually running 2x the speed as the data plate! The manual suggests this as a possibility (as a way to run carbide in 1942 ). So, my speeds were 2x what I thought!

Second hint: I recalculated my required RPM, and was apparently off by quite a bit. I don't know how I messed it up(my whiteboard was since erased), so I was running a setting higher than I should have.

SO, I was running roughly 4x the RPM I should have, at least on that piece.

Last night I did a boring operation on the carbon steel rod with the same indian hss precut set, and it worked great! I did low speeds and had no problem.

My last lathe was a 10" Logan with a 1HP motor, and bad F&S would make a racket, or cause the lathe to stall/complain way before roasting the tool. The new lathe is a 14" (actually 16") Reed Prentice with a 15 HP motor, so it sounds the same no matter what!

I think I might need to just be more careful calculating my F&S. Additionally, I may use the VFD to turn down the RPM of my motor to get me back to the data plate, one less thing to think about! Also, it'll be nice to have that additional speed available.

 

[ttabbal]

Done that..

First time fly cutting steel, I used aluminum speeds. Blew the edge in a few seconds. Reground the tool and used the right speeds, it worked great.

 

[ErichKeane]

Done that..

First time fly cutting steel, I used aluminum speeds. Blew the edge in a few seconds. Reground the tool and used the right speeds, it worked great.

I'm still getting used to the new lathe. The Logan always made it obvious when I'd done something wrong. The motor would complain if I tried to take too big of a cut, if my RPMs were too high, the noise/chatter would be really high, etc. The bigger lathe just does whatever!

For example, I was trying to part off that same 9" diameter piece with a 3/4" HSS parting tool. All looked great, and I was on power feed, so I wasn't changing anything. The cut was happening the way it seems like it should have, chips looked right, etc. However, all of a sudden it must have caught and snapped my parting tool in half! I was running low RPM and low feed rate, but without notice, I now have _2_ cut off tools!

 

[Bob Korves]

So, my speeds were 2x what I thought!

Non-contact tachometers are available from China and eBay for under $10 delivered. They come with reflective tape you can stick on stuff that you want to know how fast they are turning. Mine works well, they are quite accurate by design, and you can use them on any machine you have in the shop that you can stick a piece of reflective tape to the spinning part and shine the laser light on. Why guess?

Buy non contact tachometer and get free shipping on AliExpress.com

Buy low price, high quality non contact tachometer with worldwide shipping on AliExpress.com

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Starting at $4.38 with shipping included... (!)

 

[ErichKeane]

Non-contact tachometers are available from China and eBay for under $10 delivered. They come with reflective tape you can stick on stuff that you want to know how fast they are turning. Mine works well, they are quite accurate by design, and you can use them on any machine you have in the shop that you can stick a piece of reflective tape to the spinning part and shine the laser light on. Why guess?

Buy non contact tachometer and get free shipping on AliExpress.com

Buy low price, high quality non contact tachometer with worldwide shipping on AliExpress.com

www.aliexpress.com

Starting at $4.38 with shipping included... (!)

Yep, I bought one, thats how I figured it out! I had a really hard time getting the reflective tape to stick to anything, so I used a silver marker. It works 'alright', though I really wish it was a better device. It only sort of works, and is really a bit of trouble to figure out. I confirmed its response by turning the lathe all the way down, and counting Revs over 1 minute.