Author Topic: Currin's Travelling Sherline Show  (Read 939 times)

Online Flyboy Jim

  • Full Member
  • ****
  • Posts: 1294
  • Independence, Oregon
Re: Currin's Travelling Sherline Show
« Reply #15 on: July 09, 2017, 03:13:53 PM »
Good morning Hugh,

I followed Chris's lead and made a base plate for my A2Z QCTP. Works great.



As for a portable bandsaw you might think about a Sawzall. I use mine a lot for cutting material.

Good luck on your new adventure. Sounds like fun.

Jim
Sherline 4400 Lathe
Sherline 5400 Mill

Online b.lindsey

  • Global Moderator
  • Full Member
  • *****
  • Posts: 9664
  • Dallas, NC, USA
    • Workbench-Miniatures
Re: Currin's Travelling Sherline Show
« Reply #16 on: July 10, 2017, 12:39:38 AM »
It's not cnc, but I use a piece of .020" gasket paper between my a2z qctp and the cross slide and it works well, even with some heavier cuts. Has virtually eliminated slipping issues.

Bill

Online Hugh Currin

  • Full Member
  • ****
  • Posts: 374
  • Klamath Falls, Oregon, USA
    • www.currin.us
Re: Currin's Travelling Sherline Show
« Reply #17 on: July 16, 2017, 04:31:26 AM »
Well, I looked around the Internet some more about slipping QCTP. With crueby and Jim's info I looked for "Sherline QCTP Plate" and found two interesting links. J. E. Rickenbacker posted about his QCTP Modifications. He used a similar plate but what I found useful was the relief around the center of the QCTP. This puts more pressure toward the outside to resist rotation. "Outlaw" similarly used a plate under his QCTP. He put in a relief but put the relief in the plate, same reasoning.

The reasoning of relieving the center of the QCTP seemed solid. So I chucked up the QCTP in a 4-jaw on the large lathe. Then relieved some 0.008", using a carbide tool, to a diameter that seemed "right".



I also found a post by "John" about using a shim under an A2Z QCTP. He used it just to get the right height. But he mentioned (7th post) that A2Z suggests a piece of copy paper under the QCTP to prevent slipping.

I took Bill's suggestion and used a piece of gasket material under the QCTP. This and the relief seem to help a great deal. Not sure the problem is gone, but moving in the right direction if not arrived. I may key the QCTP to the table as mentioned above, then there is no question. I suspect with CNC there is less need to turn the tool post, and moving it requires all the tools to be re-set (if running a program), a real PIA.

I got the G-code program working well. Was able to cut a tool holder blank in aluminum. Then tried one from 12L14, free machining steel. Here I had some difficulty. The boring went well, but the threading not so much. Boring I was taking a 0.005" depth of cut at around 1000 rpm (Carbide on 3/4" diameter piece), feed rate 4-5 in/min. Similar on the OD, 0.005" depth using HSS. Threading (HSS) I started at 0.005" depth of cut and the program reduced it some as the depth increased, down to some 0.001" at the end. Threading was done at 200 to 300 rpm. To me these seem to be very conservative cuts.

Threading really bogged down the spindle motor, even stalling it a few times. It was also just not happy taking these cuts. I stalled the Z axis stepper motor at least once, not a good thing. The good news is the steppers seem correctly sized for this spindle. Maybe I can't make an internal thread 3/4-16 in steel using the Sherline? It's certainly pushing the limits. I hate to go to less than 0.002" depth of cut, it already takes forever and the tool spring may allow the tool to just rub.

Now the Sherline has a 60W (.08HP) DC motor, continuous 10 oz. in. at 6100 rpm. DC motor should hold torque at low rpm, but lower power with lower rpm. I'm not used to this, my large lathe is 5HP, an increase of 6200%. I have yet to bog it down and conservatively take 0.05" depth of cut, it'll bust tooling though.

For all you Sherline users, how aggressive are you with cuts? In AL? In steel? Any experience threading under power? Any suggestions gratefully accepted.

Thank you all.

Hugh

Online Hugh Currin

  • Full Member
  • ****
  • Posts: 374
  • Klamath Falls, Oregon, USA
    • www.currin.us
Re: Currin's Travelling Sherline Show
« Reply #18 on: July 16, 2017, 04:36:32 AM »
As for a portable bandsaw you might think about a Sawzall. I use mine a lot for cutting material.

Jim: Thanks. We have one so the cost would be minimal. I keep thinking of cutting a slice of 12L14 off a round bar for flywheels. I'm not sure I'm up to slicing a piece of 2 1/2" round with a sawzall. Probably doable though.

Thanks.

Hugh

Online Kim

  • Full Member
  • ****
  • Posts: 2171
  • Portland, Oregon, USA
Re: Currin's Travelling Sherline Show
« Reply #19 on: July 16, 2017, 05:31:30 AM »
Well, I don't have a Sherline, but I do have a Taig lathe (very similar in size and power to the Sherline).  Its been several years since I've used it much but I do remember taking forever to take steel down.  I had to take very small cuts and go slowly.  No more than 10 thousandths per pass, if I remember right.  This was using HSS, not Carbide, but I'm not sure if these little machines have the power, or are rigid enough, to take real advantage Carbide tool.  Just my thinking, though I'm no expert.

Kim

Online Hugh Currin

  • Full Member
  • ****
  • Posts: 374
  • Klamath Falls, Oregon, USA
    • www.currin.us
Re: Currin's Travelling Sherline Show
« Reply #20 on: July 21, 2017, 11:47:59 PM »
Kim:

Thanks. That matches my experience though I'm down to .005" depth in steel. The Sherline does cut it but takes awhile.

I have a mix of HSS and carbide. On my large machines I don't push too hard, it is a hobby, and can't tell much difference between HSS and carbide. I run into trouble now and again using too high an RPM with HSS. I don't expect the carbide to be an advantage on the Sherline, it was just the boring bar at hand.

Thanks.

Hugh

Online Hugh Currin

  • Full Member
  • ****
  • Posts: 374
  • Klamath Falls, Oregon, USA
    • www.currin.us
Re: Currin's Travelling Sherline Show
« Reply #21 on: July 21, 2017, 11:59:10 PM »
Been thinking a little on cutting a 3/4"-16 internal thread on the Sherline. When I get into the cut the depth of cut is only a few thousands. However, the width of cut is the thread face. For 16TPI that is 0.063" width. For normal thread cutting, feeding in at about 30deg, that is unavoidable. I found a post suggesting an alternative. Here the thread is nibbled away rather than directly feeding in at 30deg. I may try this but it would be a pain to program.

It would also help to put the Sherline in its low speed pulley. I didn't do this and likely should have.

Another alternative is to thread mill them using the cnc mill. This one is feasible.

But for now I decided to use the large lathe and single point the inside. I need to holders to get on to the Stirling build.

Thanks.

Hugh

Online Hugh Currin

  • Full Member
  • ****
  • Posts: 374
  • Klamath Falls, Oregon, USA
    • www.currin.us
Re: Currin's Travelling Sherline Show
« Reply #22 on: July 22, 2017, 12:30:03 AM »
SO, I decided to thread the inrernal 3/4-16 Sherline spindle thread on my large lathe. This wasn't too bad but took awhile to build several.

I then drilled holes for the tommy bar and set screw using the Sherline mill set-up. I had a little trouble with the Sherline toolmakers vice slipping. I went to a slightly larger steel toolmakers vice which worked better (or I just reefed on the screw harder). After that it went smoothly. I did notice some flex in the Sherline column. Spot drilling to start a drill I could see some flex and moving outward (away from column) of the spot. Then when drilling I saw the drill shift outward a little as it aligned with the spot. I was using a small spot drill (probably 3/16"). It was better when I switched to a tiny center drill (I think it was a #0) but I could still see the flex and offset. Will take some learning to use these Sherlines.

I used the Sherline lathe to finish the outside of the holders. This went well.

But I used the larger lathe to drill and ream the holders. I don't think I could accommodate the 1/4" or 3/16" reamers in the Sherline due to their length, with drill chuck length. The tail stock is off some 0.005" also. I single pointed a mock up Sherline spindle in the large lathe, and aligned the tail stock to within a few tenths. Then drilled and reamed the holes for end mills.



This worked pretty well. I had three Sherline holders, two 3/8" and one 1/4". I made up another 1/4", two 3/16" and two 1/8". While I was set up for threading I made two additional blanks and three aluminum "face plates". Foolish me, I forgot to make up a blank for an ER-20 collet holder.



Finally, I screwed each onto the Sherline spindle and checked run-out. I put an end mill in each holder and measured off its shank. The results were:

1/8" Holders       0.006"   0.005"    TIR
3/16" Holders     0.003"   0.0045"  TIR
1/4" Holder         0.008"   TIR

I also checked the stock Sherline holders:

1/4" Holder         0.006"  TIR
3/8" Holders       0.0025"  0.0025"  TIR

So, not as good as the stock holders but should be workable.

Now I think I can get back to building some soft top jaws for the three jaw, and a tooling plate or two for milling.

Thanks for coming along. Any comments or suggestions please chime in, I'm flying blind here. :-)

Hugh