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plunger
10-01-2011, 09:55 AM
I found the rotary broaching thread very interesting.Has anyone tried to make their own version of it recently?.
What I would really like to do is make the broach itself. I need a 20 tooth splined inner and outer broach to be made (male and female)
Being in africa this is not so easy and I would like to make it myself more for the learning process My first attempt failed but thats just because I am a lousy machinest. My first attempt was to set up a 100 tooth gear indexed on my lathe and I tried to make the broach by using the lathe as a keyway slotter.This is where my knowledge and maths let me down.The od is 7.75mm
I also battled to sharpen a tool as it is really hard to see something so small.
Is there a standerd angle for splines. This thing is for a faucet handle.Also I think the last spline I cut was not perfectly distanced in relation to the others. Would this maybe be because there is not enough rigidity in the set up or could it be that its similer to knurling where the od is important to the knurl wheels and this is a case where it doesnt rectify itself like a knurl would if you just go a bit deeper
Would this be a better approach. I thought if I turn a cutting wheel almost like a slitting saw and used a mill and dividing head instead would I maybe have better results.

plunger
10-04-2011, 04:18 PM
I am hoping to bump this a bit as I had no replieshttp://i941.photobucket.com/albums/ad254/eugeneeman/show_image_in_imgtagphp.pngI am hoping to make this broach as I would feel it would be a big achievement to get it right. Sorry about the small photo but its the little shaft on the right It is an inner and outer spline to extend a faucet handle.

plunger
12-18-2013, 12:34 AM
Can anyone suggest how I could make a broach for the extension piece on the right.?It needs a internal and external broach. I tried cutting it on my lathe using the rack with little sucsess. Would milling it be a better option and how would I go about it

Rich Carlstedt
12-18-2013, 12:45 AM
Plunger
Your photo is so small, no one can determine your needs.
Also are you making one, ? Going into production ? making it identical or close to ?
Those variables can mean a lot when determining the requirements .
What tools do you have available to you ?
External broaches are easy with a Shaper.

camdigger
12-18-2013, 03:14 AM
Can anyone suggest how I could make a broach for the extension piece on the right.?It needs a internal and external broach. I tried cutting it on my lathe using the rack with little sucsess. Would milling it be a better option and how would I go about it

Seems I recall Doc Nickel posted wrt a rotary broach built in his shop aboard here some time ago. IIRC, there was also a link to is website where he had posted some details as to the build process. About the same time, there was someone else from a manufacturer of rotary broach equipment posting wrt to the manufacture of these doodads. A search should turn up some hits.

As with any other request for input as to how to do a job, it would help to include some idea as to what equipment you might have access to rather than waiting for a reply only to state that the critical doodad necessary is not available to you. Seen that movie, got that T-shirt.

mars-red
12-18-2013, 07:25 AM
I recently made a modified version of this: http://mikesworkshop.weebly.com/rotary-broaching.html
Same idea, but I made it to fit a tiny dovetailed quick-change toolpost I made for my watchmakers lathe. I tried it out with a very small broach (1.2mm square) and found that it just isn't practical with broaches that small. Not only are they far more sensitive to misalignment, but enough power just can't be transmitted through the face of the broach to turn the spindle in which it is mounted. It basically just bored out the hole I was trying to broach. I was able to get it to bite a little, with lots of effort... I think it will work ok with larger broaches, but we'll see.

There's a lot to be said for the tailstock mounted rotary broaching holders... it should eliminate alignment headaches, anyway.

Regarding sharpening, I used a 2 degree relief behind the broaching edges, and stoned them lightly after hardening. Splines could be a little trickier... based on the way you describe making it, I'd say turn your taper first, then carve out your splines *toward* the front cutting face, the burrs that it raises will make nice sharp cutting edges once hardened. I'm fairly new to this myself, so take my advice as one-tinkerer-to-another. :)

MrFluffy
12-18-2013, 08:06 AM
Bit busy with life to come here much, but someone nudged me, so sorry for not chipping in earlier.

I made my own wobble broach based on mike weebly's site too, posted it into shopmade tools thread somewhere here but cant find it to point you at it but it was just a piece of stock with some bearings in which fitted one of my multifix toolholders, and a inner spindle that took the tooling in the end which rotated.
I made a dimple on the back of the inner spindle so I could apply force with the tailstock with a rotating centre figuring it would cope better with the forces as its designed for them, but could still use the compound to dial in the broach spindle axis error required for the broach to work, then just advance the two together.
I also needed a small spline like you have there for a steering UJ, and I took the original steel mating piece to the spline I wanted to replicate and ground a more aggresive flank relief than normal into it so the bottom of the splines got clearanced too and cut the other end to fit my homemade broach setup as a toolholder, then went at it. Came out fine for my purposes. I doubt it would last more than 2 or 3 pieces though as you are reducing the support for the leading cutting edges grinding a heavy relief like this to clearance to the bottom of the splines. I havent had need of it since to test this theory though.

I have square, a D shape and hex tooling for it too made up as each requirement came up. Smallest piece I have done is for a m4 allen key.

DR
12-18-2013, 08:46 AM
Rotary broaching has it's place, usually when parts are being made in an automatic lathe from bar stock being fed and parted off for each part. That way you get a broached part with no individual handling of the part.

For onesy-twosy parts broach in a press and be done with it. For these small quantities it's more trouble than it's worth using a rotary broach head.

The rotary broaching process has it's coolness factor so everybody seems to want to do it. You can do it without the expensive head or trouble of building the head. Make your broach as if it was for a rotary head, put a center hole in the back end. Offset the tailstock of your lathe to approximate the angle offset of the rotary head. Use the tailstock with a live center to push the broach into your rotating part. Same wobbling cutting action as the head provides.

plunger
12-18-2013, 08:53 AM
I have acsess to a small lathe (emco v13) and 3 ton arbor press and an iso 40 milling machine like a bridgeport with a dividing head. I would need to make small numbers under 100 probably. The diameter of the spline is 7.6mm and is a 20 spline shaft. I have made a rotary broach from the home model engineer site but I added an extra bearing in . It works well I just need to learn how to make the spline tool and was wondeering if a mill would be better using a flycutter cause the lathe was combersome and very slow to rack it.

camdigger
12-18-2013, 11:15 AM
If you have access to a BP style mill with a dividing head, a fly cutter on some annealed high carbon steel would be my bet for a cutter for low multiples. Skewing the dividing head would provide some relief for the cutter body automatically. The finish cutter could be hardened by the usual means and tempered light straw or so.

The business end of the fly cutter could be carefully freehand ground from a lathe tool bit or other cutting tool. Using the match spline for the "master" template for the cutter and viewing against a strong backlight, you can get real close. That's how some gear cutters are done in home shops.


Now knowing what you have access to and where you are in the world, that's my 0.02 ZAR.

Cam

dian
12-18-2013, 01:13 PM
Rotary broaching has it's place, usually when parts are being made in an automatic lathe from bar stock being fed and parted off for each part. That way you get a broached part with no individual handling of the part.

For onesy-twosy parts broach in a press and be done with it. For these small quantities it's more trouble than it's worth using a rotary broach head.

The rotary broaching process has it's coolness factor so everybody seems to want to do it. You can do it without the expensive head or trouble of building the head. Make your broach as if it was for a rotary head, put a center hole in the back end. Offset the tailstock of your lathe to approximate the angle offset of the rotary head. Use the tailstock with a live center to push the broach into your rotating part. Same wobbling cutting action as the head provides.

that seems like a really good approach. i have to try it. (hope it works.)

Zahnrad Kopf
12-18-2013, 01:34 PM
<snip...> For these small quantities it's more trouble than it's worth using a rotary broach head. <..snip> The rotary broaching process has it's coolness factor so everybody seems to want to do it. You can do it without the expensive head or trouble of building the head.<...snip...>

We'll respectfully disagree. Made my own for about $40 or so of scrapbinium and new bearings. Been a while, but I believe that the scrapbinium was 4140PH. Takes all of 10 minutes to set up and less to use. More trouble than it's worth? Hardly.
http://thegearmaker.com/images/rotary_broach/rotary_broach.jpg

ahidley
12-18-2013, 02:44 PM
Zahnrad Kopf I like yours BUT... If you bored the hole for the bearings 2 degrees offset from the center line then setup would be as easy as sticking the entire thing in the tailstock. The tailstock would never have to be offset from the spindle centerline.

What did you use for a thrust bearing? I assume one ball centrially located, lubed via the grease fitting?

dp
12-18-2013, 02:55 PM
that seems like a really good approach. i have to try it. (hope it works.)

Use a boring head to hold the center and you don't even have to upset your tail stock. The center can be a small ball from a bearing set between pockets in the cutter and center post. A bit of heat shrink sleeving around the joint will hold all the parts together. I may have to draw a picture :)

Zahnrad Kopf
12-18-2013, 03:02 PM
Zahnrad Kopf I like yours BUT... If you bored the hole for the bearings 2 degrees offset from the center line then setup would be as easy as sticking the entire thing in the tailstock. The tailstock would never have to be offset from the spindle centerline. What did you use for a thrust bearing? I assume one ball centrially located, lubed via the grease fitting?

Uhhhhhhhhh.... I _don't_ have to offset my tail stock... That's kind of the point...
It's a direct copy ( with minor variations ) of a Slater Rotary Broach. Made in about one day, if I recall correctly.
Three bearings. Two radial, one thrust. Most of the cost was the bearings.

dian
12-18-2013, 03:13 PM
why does it take 10 min to set up? dont you just stick in in and go?

Zahnrad Kopf
12-18-2013, 03:27 PM
why does it take 10 min to set up? dont you just stick in in and go?

If one changes the broach to another size and that one is exactly the same length as the previous one, then yes it's just like Prom Night. "...stick it in and go..."
But if the new broach is a different length, then one needs to adjust the focal point of the wobble to suit. ... which takes 10 minutes or less...

jackary
12-18-2013, 03:45 PM
Hi Plunger,
I have made a purpose built keyway cutter that can do what you require. It is much to much work just to achieve what you require but it may give you some pointers for a simpler method
http://www.youtube.com/watch?v=GS4Fyqj_eMk
Alan

dian
12-18-2013, 03:51 PM
i was not trying to be funny, but you are!

anyways, what exactly do you mean? i thought, there would be a predrilled hole to guide the the broach. (but then again i might be thinking about a different system. id sure love to make such a broach.)

ahidley
12-18-2013, 03:57 PM
I see now. I stand corrected. Their website even has dimensions. !!! Thats a simple way to accomplish it

Polygon
12-18-2013, 05:02 PM
anyways, what exactly do you mean? i thought, there would be a predrilled hole to guide the the broach. (but then again i might be thinking about a different system. id sure love to make such a broach.)

Most rotary broaches (http://www.polygonsolutions.com) will follow the pre-drilled hole even if they're off center a bit. All rotary broach manufacturers will tell you to chamfer the hole to allow the chip to curl up. But the chamfer also makes it easier for the broach to follow the pilot hole.

However, the old screw machine holders have a head that floats so that you can use broaches of different lengths. For example, if you needed to make a 1/4" hex that started 1" deep in a counter-bore, you'd probably need to make a broach 1" longer than standard. However, this would put the face of the broach off center because it sits in the holder at one degree angle. Therefore, the head can be adjusted to compensate for the length of the broach.

This highlights the limitations of adjustment free broach holders being made today, they can only use fixed length broaches.