Thread: Homebrew Slotter project !

Have you got a collet setup and a vertical milling attachment for the Myford?

If so then probably a 5mm endmill mounted in a collet mounted in the spindle nose and the armature shaft mounted in a vertical milling attachment may be an alternative solution.

Originally Posted by kafie1980

Have you got a collet setup and a vertical milling attachment for the Myford?

If so then probably a 5mm end mill mounted in a collet mounted in the spindle nose and the armature shaft mounted in a vertical milling attachment may be an alternative solution.

Hi Kafie,

Unfortunately not ! Setting up to use collets on the lathe isn't a problem, but a vertical milling attachment I do not possess. I'm going to have to think hard about how I'm going to cut a keyway in that shaft.

Hi Guys,

I've made a lathe dog and I've started machining the motor armature shaft down to 13 mm diameter.

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This is the lathe dog that I made this morning. Its a piece of 38 mm X 10mm scrap bar with an 18 mm diameter hole drilled in it centred 25 mm from one end, with three 5 mm holes drilled and tapped M6 for grub screws. At a later date I will bore the hole out to 25 mm and round off the end.

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This is the working setup. The red marks are the limits for machining the armature shaft. The bit at the end is going to have to be cut off since the armature shaft is far too long and will foul the top of the mill body casting. Cutting the end off also leaves me without a centre should I need one in the future.

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This picture shows the almost completed machining. I need to clean and square up the right hand shoulder before I take the armature out of the lathe. Now to work out how to cut a keyway in there !

The lathe tool that you can see in the picture wasn't quite long enough to square up the right hand shoulder, so I still that to do.

Thanks Guys. Your support is appreciated.

Originally Posted by BaronJ

Hi Kafie,

Unfortunately not ! Setting up to use collets on the lathe isn't a problem, but a vertical milling attachment I do not possess. I'm going to have to think hard about how I'm going to cut a keyway in that shaft.

You have a slotted cross slide which can be used as a milling table once you take the compound assembly off.

Do you have a few 123 blocks and a V block? You can clamp the shaft in the V block and use 123 blocks and some scrap or shims to get the correct height mounted above the cross slide. You can even add a few c clamps to hold everything together as additional insurance.

Basically use the lathe as a horizontal mill.

Or get out a cold chisel and cut the key way with that like they used to in the old days!
Finish with a cutting disc in a dremel if you want to.

Steve

Hi Steve, Guys,

Thanks for your posts.

Steve the mention of using a cold chisel leaves me like the chisel, Cold ! However the mention of using a Dremal gives me an Idea. I can get a 3 mm slot drill in the largest collet, and I can mount the Dremal in the tool post of the lathe. I don't see any reason why I couldn't mill a 4 mm wide 3 mm deep key slot that way. Since the armature is secureable so it cannot rotate, putting the lathe in back gear would allow locking the rotation but also allow me to rotate the armature slightly to get a 4 mm wide slot.

Actually I think that I might have a flexible drive that has a 6 mm chuck on it ! That of course is if I can lay my hands on it.

Thanks for the Ideas

I have a high speed spindle tool that I use on the Hercus sometimes:
IMG_0392.jpg

It does somewhere above 20,000RPM.
Good for grinding, or with a small milling cutter (5mm or 6mm) in Brass/Aluminium.

Haven't had much luck in steel - the bearings in the motor just aren't rigid enough.


I suspect your motor shaft is hard steel. You might have similar problems ?

The motor shafts I’ve messed with have all been relatively soft. No issues filing or machining them with HSS.

By the way that HSS tool in the photo a couple of posts back has cut, I’d be picking that shaft isn’t at all hard.

John, you might be surprised how easy it is to chisel steel.
A narrow chisel, sharpened to a reasonable edge so you can get it to bite in and then control the depth of cut. It just needs a light tapping with the hammer - trying to take a thin bite sort of like a heavy shaper cut.
Here’s quite a good explanation and demo if you’ve never done it.

https://youtu.be/TfTUVzijoko

Steve

Originally Posted by BaronJ

I can get a 3 mm slot drill in the largest collet, and I can mount the Dremal in the tool post of the lathe.

A 3mm carbide end mill at higher rpms (20000 rpm with a 0.25mm or 0.5mm depth of cut) may work better based on my experience with a CNC router that lacked rigidity or mass. Since your tool post mounted dremel is not a very rigid setup.

If you search online you can find carbide end mills for routers and they are designed with the intention to reduce tool stick-out thus reducing flexing and tool breaking.

If you find that setup not working well then a grinding disk in the dremel may work better and you can run a few passes to cut a 4mm wide slot. (Cover the spindle and ways with a rag to avoid any grinding dust).

From my experience with keys and keyways I believe they need to be a good fit with no slop, if there is any 'movement' in the fit then you are just relying on the grub screw. I'd be inclined to investigate the possibility of jury rigging another motor onto the mill just to cut the keyway, belt drive or even a power drill with chuck tightened onto the drive shaft, it only needs to go for a few minutes.

Originally Posted by familyguy

From my experience with keys and keyways I believe they need to be a good fit with no slop, if there is any 'movement' in the fit then you are just relying on the grub screw. I'd be inclined to investigate the possibility of jury rigging another motor onto the mill just to cut the keyway, belt drive or even a power drill with chuck tightened onto the drive shaft, it only needs to go for a few minutes.

Thanks Ozzie,

There is no room on the gear for a grub screw. The keyway and a circlip are the only securing components. However a dab of Locktite will cure any slop. Using the Dremal from the tool post looks as if it will do the job and a 4 mm diamond burr will clean up to size.

We will see !

John you can cut an internal keyway on the lathe, i reckon you have probably done some that way.
There is no reason why you can't do an external one the same way, you just need to drill a shallow hole at the end of the keyway for chip evacuation.

Hi Guys,

A quick thank you for all the suggestions on how to cut this key slot.

A diamond burr and a 4 mm carbide PCB milling cutter did the job, although it took a great deal of time. I must admit to taking up John (Sheds) suggestion about drilling a starter hole. It made getting the armature and Dremal easier to set up height wise. The burr doesn't cut very quickly and the Dremal very definitely isn't at all rigid.

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This is the setup that I used. To get the finished size I used the PCB milling cutter. Knowing from the experience I should have just gone with the starter hole and the PCB milling cutter.

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This is the finished armature shaft. There is a bit of swarf under the key. I did clean it out before pressing in the key. Notice the two circlip grooves ! A case of measure twice and cut once. The end one is the right one.

Now to deepen the slot in the gear so that it will push on to the shaft. Then its re-assembly time.

Thanks guys.

Hi Guys,

I've now got the motor modifications finished and the mill is now fully operational.

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I did hit my measurement error necessitating turning 5 mm more off the armature spindle. Since I had hacksawed the end of the armature off removing the centre, I had to use the four jaw chuck on the lathe to centre the spindle. It took longer to set up than it did to turn the spindle down.

Then I discovered that the key in the gear wouldn't allow the motor mounting to seat because it wouldn't go through the hole in the top of the mill gearbox, so I ended up removing the end few mm. I also found that the circlip wouldn't go through the hole either ! So no circlip... however green Locktite came to the rescue. Its going to be very hard to get that gear off the shaft should it ever be needed.

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This is the motor now fitted and working properly. The motor is very much quieter than the old one despite the fact that the mill head has all steel gears.

So thanks for all the help and advice helping me get my mill back in action. I can now get on with machining the large cast iron pulley for the Slotter Project.

Congrats on getting the motor in and running and congrats on getting the keyway milled with a Dremel, it's something I wouldn't have tried.