Author Topic: Beginner facing steel on lathe  (Read 1746 times)

Offline glinscott

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Re: Beginner facing steel on lathe
« Reply #30 on: May 21, 2023, 06:42:51 PM »
Gary:

Much nicer, good job. You can tell how smooth the surface is by sanding it "smooth" either while turning on the lathe (carefully) or with emery cloth on a flat surface (i.e. figure 8s). The easier it is to smooth the closer it was when you started. Don't know if this is common but what I've found.

Note that grinding carbide will take a special grinding wheel. I've always called then a green wheel and don't know the technical terms or grits. It's awfully hard to do better than a purchased tool. But give it a go, it'll be useful for special tools you can't buy.

Again good job. It's hard to get a good finish on a small light machine.
Thanks!  Much more practice required, but will be getting that soon with 8 wheels to make :).  And appreciate the advice on sanding to determine smoothness, I will give that a try.

Offline glinscott

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Re: Beginner facing steel on lathe
« Reply #31 on: May 21, 2023, 06:50:38 PM »
While it's specifically about South Bend lathes, the details, recommended cutting tool angles etc work just as well today as they did upwards of 100 years ago and on lathes of any brand. I have a few different hard copy's, but there's a free PDF of South Bends book How To Run a Lathe (HTRAL) here. http://www.vintagemachinery.org/pubs/1617/3789.pdf
Thank you!  I will definitely give these a read.

Take this as constructive criticism since that's how it's meant. Your pictures seem to indicate at least faint tool marks being left on your facing cuts. There's at least two items that may be creating those. Using the cross slides handcrank to face the part. Those handcranks are meant as a quicker way to make larger distance moves on the slide or possibly roughing cuts where surface finish is of less importance. For the best surface finish, try using both hands to rotate the handwheel. As one hand rotates to where it's getting uncomfortable, use the other hand to pick up the rotation to maintain the same constant infeed rate and swap back and forth between each hand.

Secondly your cross feed slide may be a bit loose. If it is, then using that handcrank always adds unbalanced side to side forces on the crossslide causing it to shift slightly towards and away from the face of the workpiece leaving those tool mark grooves. Proper gib adjustments are difficult to explain. For more entry level people, I'd suggest using the George H. Thomas method. Remove the cross or top slides handwheel and feed screw, then move the slide in and out by hand as your adjusting those gib screws. What you want is the least amount of clearance between the gib face and the slides dovetail while still allowing a smooth end to end movement without any tight spots. What you don't want is to adjust the gib so it's too tight. That's highly detrimental and result in accelerated wear on the slides, feed screws and nuts. Plus it makes the slide movements much less sensitive and predictable. If that gib is adjusted even slightly too tight, the slide itself won't start to move until the feed screw pressure gets higher than the friction amounts are. Once that happens you'll always over or under shoot the amount your expecting the slide to move. Adjusting the gib without the feed screw in place allows a much better feel for just how tight or loose the slide really is. Once you've done it a few times in that way, you'll develop the correct feel for just how tight the gib adjustment screws should be and how smooth the slide should feel once they have been adjusted correctly. Once you have that, then the slides can be adjusted normally and without removing those feed screws. G.H. Thomas mentions in a few places in one of his books that most amateurs tend to have there slides adjusted too tight. From what I've seen in many YT videos, I think I'd agree with his opinion.
Yes, still have a long ways to go on surface finish for sure.  These are great tips, thanks!  I will definitely give this a try tonight.  My wheel does not move the slide as smoothly as I would expect, and I was just adjusting the bolt for the handle.

Offline glinscott

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Re: Beginner facing steel on lathe
« Reply #32 on: May 24, 2023, 07:19:40 AM »
Spent some time adjusting the lathe, and it seems to be moving smoother now.  I also got a tool in the shape Kozo recommends from LMS while I'm waiting on the angle grinder to arrive, but it was very small, so it needed a shim in the quick change tool post, and it certainly didn't work for the outer edge (as Kim mentioned). I tried using a right-hand carbide tool, and it kind of worked for the outer edge of the wheel but required a lot of back and forth.  So, will probably wait on the angle grinder for wheel #3.

This topic is getting past the original point now as well, so perhaps I will continue it in the appropriate subforum.

Also, I overshot the dimension on the outer edge for the wheel, Kozo wants 1.75" and mine is 1.8375".  I didn't realize how much I would need to "sneak up" on the dimension as Kim put it.  Lots of learnings!  I think this wheel is still usable if I use it as the back face potentially?  1.8375" still leaves a lot of room to the final wheel diameter.  Picture of wheel two compared to wheel one below.
« Last Edit: May 24, 2023, 07:23:09 AM by glinscott »

Offline Jasonb

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Re: Beginner facing steel on lathe
« Reply #33 on: May 24, 2023, 08:16:49 AM »
One way to do the outer edge of the recess is to run the lathe in reverse and then the tool can be setup just the same* as for the hub but cut on the rear of the lathe. Bonus with doing it that way is you can feed in the same amount with the cross slide so don't go too deep or not deep enough.

The tool does need sufficient side clearance for this but should be ok at the diameter you are working at.

PS hopefully it is a bench grinder you are waiting for not an angle grinder.

Offline glinscott

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Re: Beginner facing steel on lathe
« Reply #34 on: May 24, 2023, 05:53:36 PM »
One way to do the outer edge of the recess is to run the lathe in reverse and then the tool can be setup just the same* as for the hub but cut on the rear of the lathe. Bonus with doing it that way is you can feed in the same amount with the cross slide so don't go too deep or not deep enough.

The tool does need sufficient side clearance for this but should be ok at the diameter you are working at.

PS hopefully it is a bench grinder you are waiting for not an angle grinder.
RE: running in reverse - Ah, interesting!  I will try that out on my practice wheel thanks.

RE: bench grinder - whoops, yes, that's what I meant :)

Offline glinscott

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Re: Beginner facing steel on lathe
« Reply #35 on: May 31, 2023, 07:37:56 AM »
Final update on this thread, and hopefully can graduate to a build thread :).

I adjusted the gibs on my lathe, and got it much more solid.  My cross slide moves very nicely, and is super solid.  The compound rest I had to really lock down to prevent it from moving around, so it's a bit stiff on the handle, but not too terrible.  I suspect that may be due to it being such a small lathe.  Still, it was a significant improvement!

I then tested various different speeds for facing (and actually looked up the feeds and speeds using a calculator).  That gave about 500 rpm on the outside of the wheel for the carbide bits, and 1500 rpm on the inside.  I also tried the HSS bits (with lower speeds), and found the carbide a bit easier to work with for this at least.  I then watched a video where someone recommended carbide bits intended for aluminum (so they are uncoated) when working with steel on small machines, and tried that.  It actually seems to work really well!  Pictures below.

Finally, I'm working on learning some tool geometry, but I'm really bad at grinding.  That will take a lot of practice.  So, for now, I manually filed down a holder for the carbide aluminum bits, so it doesn't dig into the edge.  Then, found bits with the right shape - diamond 55 degrees - DCGT21.51, so edges of 27.5 which is pretty close to Kozo's 30 degrees.  You can see the learning directly in the metal in the progression picture :).  The dimensions are also super close to what they should be for the final wheel.  I'll have to see if wheel 2 and 3 are worth salvaging.  I ordered enough stock to make a bunch of backups.  Plus this last wheel only took about 1.5 hours, by far my fastest, and it's also the best quality.

Thanks again everyone for the wonderful advice!

Online Kim

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Re: Beginner facing steel on lathe
« Reply #36 on: May 31, 2023, 05:55:28 PM »
Wow!  That is great!  You have made significant improvements over the past few weeks.  Great work!  :ThumbsUp: :popcorn: :popcorn:

That's what I love about this hobby - always so much to learn! 

Can't wait to follow your build thread  ;D

Kim

Offline Admiral_dk

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Re: Beginner facing steel on lathe
« Reply #37 on: May 31, 2023, 06:38:47 PM »
Great to see that you have reached a result that is to your satisfaction - that ALWAYS feels Good, when you get to that point  :ThumbsUp:  :whoohoo:  :cheers:

Happy voyage forward  :LittleAngel:

Per

Offline Mike R

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Re: Beginner facing steel on lathe
« Reply #38 on: June 01, 2023, 02:19:37 AM »
While your at it you may want to try practicing putting the hole in the wheel for the axle, you're going to want to do that while the wheel is still mounted on the chuck from the tread forming operation to keep things all concentric.  And because you're going to want the hole to be nice and concentric and to an exact size, you'll need to drill undersize and bore it out to final dimension.

More fun ahead but you're getting there.

Mike


Offline glinscott

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Re: Beginner facing steel on lathe
« Reply #39 on: June 01, 2023, 08:07:58 PM »
While your at it you may want to try practicing putting the hole in the wheel for the axle, you're going to want to do that while the wheel is still mounted on the chuck from the tread forming operation to keep things all concentric.  And because you're going to want the hole to be nice and concentric and to an exact size, you'll need to drill undersize and bore it out to final dimension.

More fun ahead but you're getting there.

Mike
Yes, great point - I've only done the fronts of the wheels at this point.  Kozo recommends doing all the fronts, then flipping to back, and putting the hole in when done with the back.  I will definitely use some of the scrap bin wheels for practicing drilling (as I've never done that on the lathe either!).  Btw, I will also use this to give a close-up of the wheel #4 - it's not quite as clear in the uploaded picture how much better it is.

Offline glinscott

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Re: Beginner facing steel on lathe
« Reply #40 on: June 01, 2023, 08:08:49 PM »
Wow!  That is great!  You have made significant improvements over the past few weeks.  Great work!  :ThumbsUp: :popcorn: :popcorn:

That's what I love about this hobby - always so much to learn! 

Can't wait to follow your build thread  ;D

Kim
Thanks!  Definitely some key advice from reading through your steps 10 times or so :).

 

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