A Fine Finishing Tool To Suit A Mini-Lathe

[Danny M2ZParticipant @dannym2z]

G'day.

After making a tailstock threading die holder for my C3 minilathe I decided to have a go at turning an M2 arbour to hold it. I have never attempted to turn a Morse taper before so figured that this could be interesting.

A suitable lump of (unknown provenance, but it's marked '2011'  mild steel (3/4" ) was found in the goodies box and so the turning began.

It soon become evident that this was the cheesiest bit of steel that I have ever attempted to turn, it defeated my best round nose tools (railway tracks) so a new approach was required.

Then I remembered downloading an article many years ago about a 'Contrary Turning Tool' **LINK** – so as the grinder was set up I decided to give it a go.

The results were excellent, the swarf came off like fine steel wool (actually dust with a 1/2 thou cut).

A few observations for mini-lathe users, if you don't have a QTCP then make a pile of shims – I use packing straps, this is the beaut thing about this tool, height does not really matter and add or delete a shim for the final cut.

Sorry if the photo's are all over the place but this site has the crappiest software editing suite – maybe it was supplied by the lowest bidder but it's still bovine effluent.

* Danny M *

Edited By Danny M2Z on 16/11/2015 03:40:05

Edited By Danny M2Z on 16/11/2015 03:48:56

Edited By Danny M2Z on 16/11/2015 04:11:34

[Danny M2ZParticipant @dannym2z]

[mahgniaParticipant @mahgnia]

Danny,

These tools do work well, but they seem to give the best result with a very fine DOC, slow feed, slow RPM, and coolant/cutting fluid.

They do have a tendency to wear quickly at the cutting edge due to the heat from the chip rubbing down the face of the tool..

Andrew.

[mechman48Participant @mechman48]

Made one couple of months ago, nice action / finish, best on ally', as said low rpm. .001" doc, slowest feed on lathe, coolant / cutting fluid, now need to make something to use it on…

George.

[VicParticipant @vic]

I have tried one of those but was not particularly impressed with the finish at the time. I must give it another go, now where did I put that tool?

[Roger HeadParticipant @rogerhead16992]

This is one of those 'round tuit' projects that has never happened, but one day… There were two long threads on other forums, worth a read, with the grinds being extended to flycutting use.

http://www.chaski.org/homemachinist/viewtopic.php?f=42&t=84313

http://bbs.homeshopmachinist.net/threads/39894-Shearing-tool-update

[Danny M2ZParticipant @dannym2z]

G' day – Thanks for the links Roger. The people on those sites came up with the same conclusions that I did.

It's a really useful tool for taking very fine finishing cuts.

I inspected the shearing edge today with a loupe, there was evidence of very slight wear after many experimental cuts on the mild steel (to determine optimum speed and depth of cut). This was easily rectified with a fine diamond lap, and anyway, just adding or removing a packing shim presents a fresh part of the edge to the work.

About 220rpm and 0.001" gives a finish such that the ridges cannot be felt with a fingernail scratched along the work, and as Mechman48 (George) said, it's brilliant on aluminium with a spash of kero. A .0005" cut resulted in no swarf as such, just a grey sludge with a mirror finish full of rainbow hues on the ali.

I should have made one ages ago as it's going to be perfect for finishing small pistons prior to lapping them.

* Danny M *

Edited By Danny M2Z on 17/11/2015 02:48:53

[thaiguzziParticipant @thaiguzzi]

Shear tool – used commonly on shapers, but with a curved face. A curved face for the lathe tool will also enable you to face with it. Yes, they give a great finish on round parts in a lathe, what i like about them, is once you are down to your last couple of thou, and switched over to the finishing shear tool, you are getting a consistent diameter the length of the workpiece. If you think they give a nice finish on a lathe, try a shaper shear tool – like a ground mirror finish.

[Author]

Posts