Group Project: Rotary Broach-- Building complete, all shipped out!

[rwm]

Earlier in the thread I was asking about having all the broaches the same length so that you could use the fixed 1 deg angle and not have to adjust the offset if you change broaches. The issue I ran into was grinding all the broaches to the correct OD without adjusting the length. In the end, I ground the broaches slightly oversize and then sharpened them (shortening them) to get the OD correct. That resulted in all my broaches being different lengths. Using a surface grinder may obviate this issue for you . Just some food for thought.
Robert

 

[brino]

I guess I'll have to spend more time researching how to make this cut. I would not bother and do everything in the grinder, except this was my plan for the "dished" center.

Yeah, I was hoping to make the best possible cutters I could, since they are so expensive otherwise. I'm a bit curious how I'm going to make this happen now though...

Hi Guys,

I've been paying attention to rotary broach stuff for a few years with the very distant plan of building one.
That's why I've been following along here .....research.
However I did not join in your fun due to lack of time.

I do remember reading a paper saying that the concave end was not required and might even hurt cutting edge strength/life.
I will see if I still have a copy of that report.

I also remember someone cutting the dish shape with a dremel grinding stone with the broach cutter in a spindex.

-brino

 

[rwm]

I cut my dish with a Dremel mounted on the cross slide with a cutoff wheel. I rotated the broach slowly in the lathe.
Robert

 

[ErichKeane]

Hi Guys,

I've been paying attention to rotary broach stuff for a few years with the very distant plan of building one.
That's why I've been following along here .....research.
However I did not join in your fun due to lack of time.

I do remember reading a paper saying that the concave end was not required and might even hurt cutting edge strength/life.
I will see if I still have a copy of that report.

I also remember someone cutting the dish shape with a dremel grinding stone with the broach cutter in a spindex.

-brino

I have a air-die grinder I think that i have some small wheels for, I might end up using those if that is necessary.

A big part of it was trying to get the general profile 'right' to avoid spending too much time on the surface grinder, since that is likely going to take a while. It would be interesting if I could skip doing the dish though!

Earlier in the thread I was asking about having all the broaches the same length so that you could use the fixed 1 deg angle and not have to adjust the offset if you change broaches. The issue I ran into was grinding all the broaches to the correct OD without adjusting the length. In the end, I ground the broaches slightly oversize and then sharpened them (shortening them) to get the OD correct. That resulted in all my broaches being different lengths. Using a surface grinder may obviate this issue for you . Just some food for thought.
Robert

I think with the amount of 'wobble' we have in ours that the offset is actually going to be less important than with other designs. I suspect we'll have pretty close to a 'self adjusting' head, since the rear bearing fit is going to be so loose I think.

 

[GunsOfNavarone]

Well. @ttabbal and myself will be waiting by the swim up bar, come find us when you guys are done!

 

[ErichKeane]

Parts showed up today! The spindles showed up and are all great! The rear-most diameter might be troublesome, the extra is undersized by a bit, but hopefully still useable.

The rest are unfortunately tight on the bearings! I don't know if the bearings are just undersized, or I speced it out poorly. I figure I can chuck it up in the lathe to polish off a few thou to make it a slip-fit.

Anyway, progress made! Great job @T Bredehoft !

 

[ttabbal]

Nice to see more parts!! I'll be getting some shop time over the next week, so mine will ship out soon. Hopefully temps will drop under 100F, but I'll work at night if needed.

 

[GunsOfNavarone]

I’m hitting post office tomorrow, you should have the backing plates Tuesday-ish.

 

[ErichKeane]

I’m hitting post office tomorrow, you should have the backing plates Tuesday-ish.

Haha, wow! You guys are moving quick! I spent a bit of time already grinding 1 side if each but square to give me a reference surface. I'm still thinking through some order of operations, but this part went pretty quick! I have quite a bit ir material to take off a few length wise, but I think I can use the bench grinder to make up some distance quicky.

 

[GunsOfNavarone]

I contacted that "TomMakeHere" guy....(one of the videos in this thread). He has an Etsy page and he normally offers 10mm diameter cutters, though he could do larger, he says he's having a problem sourcing the stock as of late. Anyone have a good source for these?