Broaching tools for the lathe

[TorontoBuilder]

I have a project that will require broaching several parts with splines, so it is time to start modifying a tool holder to make a broaching tool(s)

I'll be making one motorized tool and one manual tool.

We have a second Dickson Tool Post Type S2T that I'd like to mount to an adapter along with a spare spin indexer that can then be mounted on the milling machine. So I'll be looking to make a cross slide or see if someone is selling lathe parts that can be adapted for this purpose.

I am copying many of the features I saw on a build by Make it extreme...

Taking an existing Dickson S2 plain bore toolholder with a 32mm bore, and inserting a bronze bushing with a 1" bore, and making a 1" shaft that will be bored on the end to accept insert type tool holders.

The slider shaft will have an alignment groove machined in it. Two screws with concave .125" radii milled on the bottom will trap two .25" ball bearings in the groove of the shaft so as to maintain the alignment of the shaft while under power regardless of any misalignment of the drive shaft. This will require the drilling and tapping of only one new hole in the mid-point of the tool holder in line with the four existing holes.

Bonus, I've been working to restore a friend's General 780 Jointer and 130 Planer, and designing a dining room table for my brother to make for his partner. She wanted a more rustic look.

 

[PeterT]

Following along. There are quite a few YouTube videos if you search under 'key way slotting lathe' as opposed to broaching or splines. They vary from simple displacing the carriage, to hand lever operated to rotary to linear powered. When you see them operating, they must take a very small nibble at a time, like maybe 0.001" advance per stroke required. Also the chuck must be locked rotationally. Maybe a low gear with backlash removed is sufficient? Indexing must also be accomplished in the case of splines. I am a little concerned about the pulsing force to headstock bearings. They bearings are pretty robust but still its not something a lathe typically sees. Usually its steady axial load under power feeding. A mill might be a bit better, but all depends on its capabilities of it vs. lathe. Obviously broach & press is the normal weapon of choice but that's a different setup altogether.

https://www.youtube.com/results?search_query=key+way+slotting+in+lathe

 

[Susquatch]

I take it that you two guys have not found, or don't want, a shaper?

making a 1" shaft that will be bored on the end to accept insert type tool holders.

I'd be aiming for HSS for this job, not an insert. Even an insert for Aluminium won't be nearly as sharp as a HSS tool could be. I would think that the depth of cut required for this job would dictate a tool that is honed to be sharp as a razor.

 

[TorontoBuilder]

Following along. There are quite a few YouTube videos if you search under 'key way slotting lathe' as opposed to broaching or splines. They vary from simple displacing the carriage, to hand lever operated to rotary to linear powered. When you see them operating, they must take a very small nibble at a time, like maybe 0.001" advance per stroke required. Also the chuck must be locked rotationally. Maybe a low gear with backlash removed is sufficient? Indexing must also be accomplished in the case of splines. I am a little concerned about the pulsing force to headstock bearings. They bearings are pretty robust but still its not something a lathe typically sees. Usually its steady axial load under power feeding. A mill might be a bit better, but all depends on its capabilities of it vs. lathe. Obviously broach & press is the normal weapon of choice but that's a different setup altogether.

https://www.youtube.com/results?search_query=key+way+slotting+in+lathe

I too am absolutely concerned about the lathe bearings. That is why I would have a manual option for very limited use on the lathe for simple keyways. Anything more I wish to set up on the milling bed as a ridgid base. The only thing affected by the force will be the spin indexer. I have upgraded the rotational lock on it and plan to add one more. I also modified my spin indexer to accept external indexing plates for indexing not possible with the netive vernier scale.

 

[TorontoBuilder]

I take it that you two guys have not found, or don't want, a shaper?



I'd be aiming for HSS for this job, not an insert. Even an insert for Aluminium won't be nearly as sharp as a HSS tool could be. I would think that the depth of cut required for this job would dictate a tool that is honed to be sharp as a razor.

You know who wont allow us to add any more machines. So we have to modify and adapt those we have. So no shaper.

Yes, my main "insert tool holders" will actually hold square HSS tool blanks from 1/8" to 5/16" square.

I have two CBN wheels and a dedicated set-up where I should be able to grind any profile I need. I'm also setting up the spindle from my swiss mini mill to serve as a tool and cutter grinder/cylindrical grinder rather than a mill.

Is there any other kind of sharp but razor sharp?

 

[Susquatch]

You know who wont allow us to add any more machines. So we have to modify and adapt those we have. So no shaper.

I see....... No need to say more.

Yes, my main "insert tool holders" will actually hold square HSS tool blanks from 1/8" to 5/16" square.

Sounds like you have the bases covered.

I have two CBN wheels and a dedicated set-up where I should be able to grind any profile I need. I'm also setting up the spindle from my swiss mini mill to serve as a tool and cutter grinder/cylindrical grinder rather than a mill.

This is probably what I should be thinking too. Affordable tool & cutter grinders keep slipping through my fingers despite the lack of general fussiness.

Is there any other kind of sharp but razor sharp?

Yes, but they are female.

 

[PeterT]

A shaper would be nice & very well suited. I've even been offered one. But it would probably sit there the other 99.9% of the time. I keep thinking there has to be simpler way to make keyway slots & splines. But if there were, it probably would have been invented 200 years ago.... and probably look remarkably similar to a shaper.

 

[Mcgyver]

I like the table design.

On the broach, are you expecting the balls to rotate or you're just using their form to guide the shaft? I think it poses some challenges, what about a triangular slot and machine/grind/scrape a triangular gib to fit? Your bore and shaft will have to be a very close fit. For example, that arrangement is used by the uber expensive Fehlmann mill (think a round column bench mill for $45,000) to register the head to column for maintaining accurate positioning as the head is moved.

I am a little concerned about the pulsing force to headstock bearings.

Agree one needs to be concerned with loading rolling element bearings when they're not rotating, but I think its a matter of degrees. AC's, very light cuts. Roller bearings, fairly light cuts. Plain bearings, have at it, you're not going to hurt them. Same problem mill or lathe. imo, use a substantial machine and keep the load light and all will be fine.

I keep thinking there has to be simpler way to make keyway slots & splines. But if there were, it probably would have been invented 200 years ago.... and probably look remarkably similar to a shaper.

The new old mill I've got has a slotting head. (bringing the mill and lathe home piece by piece in the trunk of the car, taking for ever, but so far wife suspects nothing lol). It and I think every other slotting head I've seen has dovetails. Its just an easier geometry to end up with the accuracy needed (high accuracy via scraping is accessible for us home shop practitioners, its adjustable via the gib and it constrains the tool). Just saying its worth thinking about why all the slotting heads and most all shapers (the box way Atlas is an exception) seem to be done this way.

 

[TorontoBuilder]

I like the table design.

On the broach, are you expecting the balls to rotate or you're just using their form to guide the shaft? I think it poses some challenges, what about a triangular slot and machine/grind/scrape a triangular gib to fit? Your bore and shaft will have to be a very close fit. For example, that arrangement is used by the uber expensive Fehlmann mill (think a round column bench mill for $45,000) to register the head to column for maintaining accurate positioning as the head is moved.



Agree one needs to be concerned with loading rolling element bearings when they're not rotating, but I think its a matter of degrees. AC's, very light cuts. Roller bearings, fairly light cuts. Plain bearings, have at it, you're not going to hurt them. Same problem mill or lathe. imo, use a substantial machine and keep the load light and all will be fine.




The new old mill I've got has a slotting head. (bringing the mill and lathe home piece by piece in the trunk of the car, taking for ever, but so far wife suspects nothing lol). It and I think every other slotting head I've seen has dovetails. Its just an easier geometry to end up with the accuracy needed (high accuracy via scraping is accessible for us home shop practitioners, its adjustable via the gib and it constrains the tool). Just saying its worth thinking about why all the slotting heads and most all shapers (the box way Atlas is an exception) seem to be done this way.

The balls are only for alignment to prevent the shaft from rotating as it reciprocates.

Yeah I'm thinking of just using a hand actuated slotting tool on the lathe, and making a separate heavier broaching tool that can mount someonewhere solid like the mill table. I have been trying to buy a old milling table but they're either rare, too expensive or being sold by facebook marketplace aholes who dont respond to inquiries on their ads.

I've also been looking for a slotting head ever since we acquired our bridgeport from Susquatch. Like how dare the dude sell a mill without a slotting head I've also been trying to find a right angle head to use on it to no avail so far. The universe seems not to want me to cut slots.

Dovetails are certainly something to think about. But I'll try one of this version first because I have some many tool holders with the bore in that that I haven't thought of many other uses for yet

 

[Ian Moss]

I have a BP right angle head (R8), but no horizontal shaft and outboard shaft support. Is that something you would be interested in?

 

[TorontoBuilder]

I have a BP right angle head (R8), but no horizontal shaft and outboard shaft support. Is that something you would be interested in?

Maybe. I've been holding out hope I could find a complete head, arbor and support at auction but may give up

 

[140mower]

Maybe. I've been holding out hope I could find a complete head, arbor and support at auction but may give up

It's time to cross over to the dark side and get yourself a shaper. Why tie up a perfectly good Bridgeport when a shaper is all you need.
.... okay, a shaper and space, but who gets everything?

 

[1018Machine]

Nice couple of projects TB!

 

[Darren]

This looks pretty interesting:

Rotary Broach - Can it really be this simple?

I needed to duplicate this confined space hose barb. It’s 3/8”NPT male on one end and 5/8” hose on the other, but no room for an external hex drive , thus the internal hex key drive. So after looking at the commercial rotary broach offerings and seeing $400+ and $40+/cutter, I was surfing around...

www.hobby-machinist.com