Broaching on the Lathe

[jjr2001]

Not a new idea but I thought I would post my latest use of a tool I did not have.
The price of broaching sets is right up there to the point of tools I would like but
have not purchased yet. Since my new pulley needed a keyway slot and it was
made from aluminum I thought I would try the lathe method.

On hand were a couple of cutoff tool bits that I don't use on my lathe since they
are a bit on the large size for a mini lathe. So I mounted one HORIZONTALLY in a
tool holder and went to work. The pully was still attached to the 3.5" chunk of
aluminum round stock. I only took .001" on each pass to keep the pressure down.
After 30 minutes I had "broached" a 4mm keyway in my new pulley. Since I was
broaching in a blind hole I added an extra step to move the cut curl inside the
pulley after each cut. This doubles the time to complete but was necessary
to get the "chip curls" out.

One thing to note is the steady rest. It is being as a spindle lock in this picture to
hold the pulley firm and not allow it to rotate. Don't forget to unlock it prior to
running the lathe with power! No I did not do that, just thought I would mention it for safety reasons.

This should work with steel but I would take a .0005" cut for the first attempt.

Cheers, JR

[Let'sLearnSomething]

thats awesome tool bro

[Toolmaker51]

Great job jjr2001. Times call for broaching without standard means. Cutoff blades are made in enough width/ height sizes to render most keyways. I can't say whether flat or hollow ground type work better. I do think flat tapered blades are stiffer than T's, helpful when goal is depth. A cutoff tool normal edge will shear, but found a hook [per broach or bandsaw tooth ] break chips best. Easy with an abrasive cut off wheel.
If possible, drill through part wall, perpendicular and just beyond end of keyway. When cutting blind, the relief lessens crowding.

[jjr2001]

Thanks for the tips Toolmaker51. Next time I think I will grind a hook on the cutoff blade.

Cheers, JR

[hoyt]

One thing to note is the steady rest. It is being as a spindle lock in this picture to
hold the pulley firm and not allow it to rotate. Don't forget to unlock it prior to
running the lathe with power! No I did not do that, just thought I would mention it for safety reasons.

Nice technique, but I have questions about your steady rest. It looks like a Plamgren. I'm looking for a steady rest for my Logan 400 9" lathe and wonder about your specifics and if I could adapt it to my lathe.

[jjr2001]

Hello Hoyt and thanks for checking in.

Not sure where to find a stead rest for the Logan.
My lathe is a small one known as a mini lathe and it is only 7x16" and my steady is from LMS.
Littlemachineshop.com has steadies for that lathe and some that are larger.
It might be possible to modify one of them to fit the bed or your Logan.
Grizzly might also have some that might be modified for the Logan.

There also some builds on Homemadetools.net that could be built to use on the Logan.

Homemade Tools Search: steady rest - HomemadeTools.net

Cheers, JR

[Paul Jones]

JR,

As you stated, the broaching operation on the metal lathe is not very fast when taking only 0.001" per pass but it does work. I too did a similar operation with a larger 12" swing lathe but never moved in more than 0.001" to 0.002" per pass without too much "digging" into the metal (see http://www.homemadetools.net/forum/b...7110#post23249 ).

Lathe broaching works okay for one-off operations for key dimensions where one does not have the exact key way broach (in my case I don't have metric-sized broaches).

Thanks for posting,

Paul

[jjr2001]

Thanks Paul, I checked out your post and that reminded me of the lathe broaching tools that I have seen here on HMT and other sites.
I have on my list of to make tools this:
Toolpost slotting tool - mikesworkshop
Looks like a lot of leverage so a larger cut could be made. Maybe next time!

Cheers, JR

[DIYer]

Thanks jjr2001! We've added your Lathe Broaching Method to our Machining category,
as well as to your builder page: jjr2001's Homemade Tools. Your receipt:

Lathe Broaching Method by jjr2001

tags: lathe, broach