manual lathe slotting broaching attachment

[thehomeengineer]

Hi All
I made this simple manual slotting/broaching attachment for my lathe. I do have a set of imperial keyway broaches but the set only has 5 sizes. As broaches are so expensive and this is afterall only a hobby I can't justify buying every size I need. The cost and the amount of times I would use each broach and often to only cut one keyway. I decided to make this tool so I could cut anysize by grinding a piece of high speed steel to the desired size.

The tool has a 3" stroke and the material costs were half the price of one good quality broach. I kept the build construction very simply by using a solid square stock bar as a ram with a simple lever operated movement to drive the tool in and out.

The other advantage of this tool is blind holes can also have keyways cut, I normally drill a cross hole or undercut the bottom of the hole to prevent a build up of swarf at the end of the stroke.

The ram is held in place with two Jibs/Wear plates so the tool is ridged but can still slide smoothly with little friction/resistance.


Manual slotting tool


Lever mechanism.


Made to fit standard lathe tool holder.


In place on the lathe with the ram fully back.


Fully forward (total tool movement 75mm / 3")


Different tool holders can be clamped to the ram.


Jib/Wear plates can be seen top and to the left of the main ram. The plates are adjusted by grub screws to prevent lateral side movement while cutting.

This didn't take long to make but has saved me hundreds of pounds in tooling.
Thank you for taking the time to read.
The Home Engineer

[DIYer]

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

Lathe Broaching Attachment by thehomeengineer

tags: broach

[DIYSwede]

Thank you, TheHomeEngeineer for sharing yet another finely made and finished tool!

I'll eventually need to cobble something similar together, though much smaller and compact -
and wonder if you choose your ram to be 1/2" sq, and a 1/4" dia for the tool holder?
Ram housing out of 6" of 2" sq BMS stock?

Already being cheap and dirty, I'll probably settle for a housing block of (free) cast iron with integral,
milled QCTP dovetails and 12 mm sq hot-rolled for a ram and handle for my 7 x 12" mini lathe.

Cheers

Johan

[thehomeengineer]

Hi Johan
Thank you again for your interest and kind words.
This tool was made from stock bar the ram was 3/4” (19mm) as this is what I had to hand but it could have ended up being 1” (25 mm) or 1/2” (12 mm) as I did not make to any design and made it up as I went along. I knew the tool would only be used occasionally, as I try to always use my imperial broaching set when ever possible. So I didn’t want to spend to much time and money making an elaborate tool but something basic to just get me out of trouble. As it happens it works great and have used it quite a few times.
The actual tool was made about 25 years ago and it sits on the shelf but is a life saver. The largest keyway cut using this tool was 12mm width x 50mm long.
With reference to your build and with out telling you how to suck eggs. Try and make the ram and body as large as possible as this increase the tool rigidity and with the lathe carriage clamped to the bed stops the carriage being pushed back away from the chuck. You can only take small cuts 0.002” (0.05 mm) but it doesn’t take long to cut a slot.
I look forward to seeing your take on this build on HMT as I am sure many improvements can be made like an adjustable stop fo blind holes etc.
Many thanks again
Andy

[rdeg]

This is a great idea... Well done! Thank you Home Engineer...

[Toolmaker51]

thehomeengineer hits it again!
I appreciate savings against little used tooling. Using lathe axis means you could make quite large keyways, even roughing first by milling. Either way, far less effort and tooling than trying to push an equally sized broach, handful of shims, and 6 ton arbor press.