Lathe and mill bits

[tufty]

To avoid further polluting kurplop's rather magnificent Planet 6 thread, I thought I'd pull this out to it's own thread.

So, I have a milling attachment for my lathe.  It looks like this. 


The milling spindle has a morse taper 1 toolholder.  It looks like this.


I could do with a cross drilling attachment, so I figured I'd make myself a morse taper 1 chuck holder for the little makita chuck I have lying about.  Or, even better, make myself some morse taper 1 collets for holding drills and / or endmills directly.

We start from a piece of horrible rusty steel rod, around 20mm diameter.  This is steel "a ferrer les ânes" (only good for making horseshoes for donkeys), but it's OK as a test piece.

Chuck it up in the 3 jaw, centre drill it.


Turning with a tailstock centre is not the easiest thing to do with my lathe, as the lever carriage interferes with the workpiece and / or tailstock.  So we push the tool out as far as we can go, and take rough cuts, accepting that tool chatter is going to result in a horrible surface.  This way, I turn down the tailstock end to 16mm, in order to be able to put it in a collet.  We're done with the 3 jaw now, and good thing too.  Horrible bloody thing.




Mount the piece in a collet, face and centre drill the other end 5.5mm for threading M6.


Skim off all the rusty crap.  Nasty cut, go fast, hog it all off we don't care about the result. Turn down 20mm or so of the end to 8mm diameter.  Go carefully, it's not supported.


Set compound to ~1°30', chuck up existing toolholder, adjust compound angle to the correct 1°26' or so.  Should really have done this with my dial indicator, but that's a bastard to set up, so I eyeballed it. Bad me.


Cut taper.  Initial cuts can be rough, but get careful near the end with fine passes, around a tenth of a millimetre depth for the final cuts, with the tool extended and the tail in a centre.



Sling an M6 tapered tap in the tailstock, do a first cut on the interior thread.  By hand, my lathe has no brake.  With the thread mainly cut, follow up with an M6 blind hole tap to get all the way to the bottom.



Check for fit - Yay.  Dropped in, needs a tap from the rubber mallet to remove it.


This will almost certainly become a 6.8mm collet (tapping drill size for M8), if nothing else because I didn't turn down the stub at the end to the right diameter for a chuck thread.  Shorten, drill through 6.8mm, slit and harden.  We'll see.

[tufty]

Overall, it took me a couple of hours to do the above.  Drilling and slitting another 10 minutes, and then there's the hardening and tempering, although if I was doing a lot of these, I'd do that all at once.

So, what have I learned from this experience?

- Starting from a piece of fast turning steel of a more appropriate diameter would have reduced overall time enormously, both in terms of how much material I could remove and keep an acceptable finish, and in how much material needed replacing.  Even tearing off a millimetre at a time meant 6 extra passes compared to starting with a 14mm diameter rod.
- For a chuck mount, I should have turned down the stub to the correct diameter straight away.
- I need to get my arse in gear and replace those sodding levers with something more appropriate so I can turn between centres easily
- If I was making a series of these, it would be much easier to drill for the final piece holding size if I had a W20 -> Morse #1 adaptor

Although it was a fun experience, it's probably not cost effective.  Morse taper collets aren't that expensive.

[kurplop]

Thanks for posting.

Was this just a test and if you decide to make some with better steel, what kind would you use?

Have you done any heat treating before?  I've read that the type of alloy can radically affect the way you do the hardening.

Are there any advantages with the levers? I can see where it may be quicker for a lot of second op functions. How about the backlash?

I think the fun is in the experimenting and learning what you can do with it.

[tufty]

Yeah, this is more of a test than anything else to see if it was worth the effort of turning my own MT1 collets.  Not sure the answer is "yes", but I'll take it all the way in any case.

For a better / known quantity steel I'd probably go with 4130, or something a bit more exotic like 8620 (although the hardening process is more difficult with that).  This piece is getting the standard cherry red / oil quench / heat to straw / cool cycle, and we'll see what that gives.

The levers are great for some ops.  For example, at work I have 180 pieces of aluminium that need 2 pairs of parallel 5mm holes drilled, one pair at each end - this lathe is *made* for that sort of thing - two cross slide stops and a depth stop...  Clamp block, cross slide lever out, drill, cross slide lever in, drill, unclamp, flip, clamp, cross slide lever out, drill, cross slide lever in, drill, unclamp.

Backlash with the levers is a problem on the compound, for the cross slide I can lock it all up using the two stops. Poor man's dials, they're 8mm allthread, so 1 turn = 1.5mm, one "flat" on the locknut is 0.25mm, "flat" to "point" is 0.125mm, etc

It's all a learning experience.  That's what makes it fun

[tufty]

In a related note, came across this video about getting parts to run true in a 3 jaw chuck.  Basically DIY collets.