Member postings for Huub

Basically I don't use a 30° / 27°.5° threading infeed angle even when doing CNC threading. But if the lathe is reaching it's torque limit, I use the 30° / 27.5° angle so that only one side of the threading tool is cutting. This reduces the cutting force a bit.

I have a sievert and that works well. The tip of the torch can be changed, I use a 22 mm (nr 394102) tip.

My torch was delivered without a pressure regulator. That can be very dangerous. If you nock over the gas bottle, not gas but liquid propane comes out of the torch and suddenly you have a flame thrower.

Mount the indicator on the housing of the spindle to make sure you are measuring a spindle problem, not the play and deflection of the other parts.

If the spindle has tapered or contact angle bearings, these can be adjusted to reduce play. The manual should mention the bearing type.

The metal removal rate on my mini lathe is quit good. Checkout this link at 2:40

https://youtu.be/zH332Z-Lqhs

Normally I do not run under such conditions. The wear of the lathe (just a half nut) would be to large and I use it just for hobby!

Edited By Huub on 09/03/2022 08:25:02

Edited By Huub on 09/03/2022 08:26:21

My first lathe was a mini lathe (60 kg) and I used over 10 years before I bought a bigger one 360 kg).

The small lathe is as accurate as the bigger lathe, but it takes more effort (need to measure more often).

On the mini lathe I can cut hot rolled steel at 0.5 mm (even more) CD so each pass a mm diameter reduction. The the bigger lathe can do way more but that also means more chips flying around, so I normally don't go beyond 0.5 mm CD.

Work holding of larger parts, can be an issue. Nevertheless, I turned a 170 mm aluminium face plate that took me half a day. On the bigger lathe, it would be done in an hour.

The mini lathe can run 2500 RPM, the bigger one just 1850 RPM. For small parts, I still use the mini lathe because the small (80 mm) chuck and the higher RPM is more suitable for small stuff.

New (roller) bearings will take some time to run smooth. You should run them (no load) at a low speed and increase the speed by small steps until you reach the max speed. This process should take at least an hour and it will improve the life time of the bearings. The bearing will get warm (not hot) and this heat will let the grease go to all corners. After this initial run, it will take hours before the new bearing will run very smooth.

You should check how much force it takes to turn the spindle by hand. It should be a bit higher then before swapping the bearing and changing the gear, but no more than that.

I also suspect that the motor doesn't get enough power and that there was more damage than just a power resistor.

For me, I do not see any advantages in using windows 11. As all new software, it will contain bugs. Maybe in a year or 2, when Windows 11 is mature, I will give it a try.

That looks pretty usable, promising and "doable" .

Thanks for sharing

I have ccmt inserts that have the same 80° tip. When turning, the clearance angle is 5°. If the cutting depth is shallow, the chips get between the workpiece and the insert and the turned diameter is way out of spec. This happens a lot when I do small diameter inner turning. For inner turning I prefer TCMT or DCMT inserts.

Because of the 5° clearance angle, the load on the tip is also a bit higher then when using TCMT or DCMT type inserts (CCMT longer narrow chip). On the not so rigid mini lathe, I prefer TCMT inserts.

I would have turned the shoulder. Didn't think about doing it your way. Learned something today

Nicely done and by facing the plate on the mini lathe, it will run true (facing side).

Parting using such a large stickout was very brave, no risk no reward.

I used a 1.2 MM HSS parting tool for years on the small lathe. For parting you need rigidity. To avoid the parting tool digging in the workpiece, I place the parting tool upside down and invert the spindle rotation. I also let the tool stickout as small as possible. Since I do it this way, even parting steel is not a problem.

I also made a 2mm insert holder for the small lathe and even that works fine. Only the Nema17 stepper on the X-axis has just to little power and misses steps when parting steel. So I replaced it by a Nema 23 stepper and now that is not a problem any more.

Youke,

Which method would you follow to polish
I use in this order:

• 400 grid sand paper, sanding by hand (this dust is killing for the lathe ways)
• steel wool (safe to use on the lathe)
• dremel and polish paste (this dust is killing for the lathe ways)

I think you should avoid to round the corners of the tip of the tooth.
It would make the teeth a bit stronger but I never do it.

The CNC turned cutters have an excellent finish and are good enough as is.
From the the milled cutters, i only remove the burs by scratching with my nails. The finish is not as good as the turned cutters, but good enough.

After hardening (I only harden for cutting aluminium and HPL, not for plastics, don't cut steel) I only give the flat cutting face a few strokes on a stone (800 grid I think)
I don't relieve the 25 mm long fly cutters after hardening. I want them as hard as possible. I do not quench in oil (anymore) but use water.

When turning using form tools, the cutting edge is often large. This gives a heavy load on the tool (post), comparable when doing threading. Let the tool stick out as minimal as possible and keep the tool above the tool post. If the tool shatters, reduce the RPM. Some times also to shallow cuts can cause chatter.

If you use the "Tangential cutter" you need to let the tip stick out as minimal as possible.

I keep the stick out of my tools below 12 mm. Only when turning between centres, I need more stick out. Because then the load is quit small, it is not a problem.

Final result was a tooth thickness varying between 1.56(7)and 1.58(1)mm (measured with micrometer), not bad I think
This is more than adequate for cutting gears.

Next steps will be cutting the 4 teeth of the gear cutter,
If you want to polish the flank of the cutter, do it before cutting the teeth.

Edited By Huub on 20/02/2022 23:10:45

Jouke,

with following results: 4.30(3); 4.30(5); 4.30(7) and 4.30(5)mm.
Great to see results are improving. Turning within 0.01 mm on a hobby lathe is not only good but excellent.

To my opinion this result is more than good enough to proceed to the next operation
I agree, you have the base for a good gear cutter.

I am looking forward to see the finished gear cutter and the gear you made using this cutter.

Huub

Edited By Huub on 17/02/2022 21:46:05

I seems (holes are dry) that you don't use tapping fluid. This is killing for your taps.

Jouke,

I still can do the other side but I can also start again from the beginning on this blank.
Just use the same blank until you get it right.

Not a really smooth surface.
If you are targetting the 0.01 mm range the surface should be really smooth. That is the first to achieve. Start by using a softer steel to get a feel for it. Check the tip of the tool using a 10X magnifier. Some damage is hard to see by eye.
You should play with the RPM, cutting depth and feed. Depending on the insert, you can't do a shallow cut. Depending on the rigidity of the lathe, you can't do a thicker cut. If there is an unbalance in the chuck (or bad bearings), you can't run high RPM.
Listen to the sound the cutting makes. You can hear if the cutting is smooth or rough!!!
Make notes of the metal type, turning conditions, tool data and the result. Buildup experience!!!

I did not polish before facing
I just give it 2 passes in 2 directions to remove any burs or high spots (from impurity's).

Rpm was 550.
That is pretty slow for carbide. I have a Vc (Velocity at the outer diameter) of 180 mm/min!!!

My test on the small lathe
I faced an other 40 mm washer on the small lathe (HB300) using the glue method (cheap Super glue from the Action store). I faced a 20 mm register to loosely centre the washer. I gently pressed the washer against the mandrell using my fingers.

I faced both sides CNC using a carbide insert, nose radius 0.4 mm, RPM 1400, Feed 60 mm/min, 0.05 mm cutting depth (final pass).
Spread 4.045 .. 4.055 mm, the same as on the bigger (HBM BF290)

Then I faced one side again, but now manual (on the same lathe)
Spread 3.925..3.920

So I can repeat the results on both lathes manual and CNC.

I boiled the glued washer for 6 minutes (microwave) but couldn't separate the washer from the mandrel. It took a bit force (screw driver) to get is lose. So I couldn't measure the thickness of the glue but I estimate around (0.02..0.05 mm).

Normally I heat up the mandrel using a torch!!!

Edited By Huub on 15/02/2022 13:07:36

Edited By Huub on 15/02/2022 13:08:06

Good to know that ebay will always refund the buyer so it is better to use insured shipping to avoid problems.

I don't have these problems because I do not sell by a third party.

When I sell something I give the buyer the option to send it the cheapest way at his own risk or the insured way. I always advice to choose the insured option. Most buyers choose the cheapest way and I haven't got complains that they didn't receive the Item.

I agree, and this can be an expansive repair. If you can't find the cause the new board will probably also be gone in seconds.

You could change te motor and control by an AC motor and VFD or an AC Servo motor and AC servo controller. I know it is not the cheapest option but it has to be considered if you can't find the cause.

I do not know how old and worn the lathe is, but maybe is replacing the lathe also an option.