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

[ErichKeane]

Gorgeous! I'll make sure to send you my address.

 

[ErichKeane]

I just got t tabbal's parts in today, which makes a complete broach holder! I still have to pick up the bolts and set screws to assemble, and do a slight rework on the spindle(as previously mentioned), but everything else looks great!

I'm really happy about how nice of a fit the spindle and body have, the .750 clearance hole works nicer if they are somewhar tight.


I've been delayed a bunch more on the bits, I ended up spending the last week or so buying then picking up, then playing with a new full-sized mill (plus spending this coming weekend moving it into place), so I have been distracted

I DID spend some of my shop time today grinding the setscrew flat on the bits, though so far this cost me a grinding wheel! Believe it or not this wheel used to barely fit in the housing!


Fortunately I have one better at cutting HSS in the mail that I should be able to use to accurately cut the design on the broach.

And here they all are so far:

 

[GunsOfNavarone]

Oh crap! forgot I had a broaching tool coming...I better find that arbor(s) I need! What size if the arbor on that grinder? What mill did you get?
On an somewhat related note...my compound machining project won me a new Mitutoyo Digital micrometer from Practical Machinist. I guess I got t post more of my projects, could be a lucrative side gig!

 

[ErichKeane]

Oh crap! forgot I had a broaching tool coming...I better find that arbor(s) I need! What size if the arbor on that grinder? What mill did you get?
On an somewhat related note...my compound machining project won me a new Mitutoyo Digital caliper from Practical Machinist. I guess I got t post more of my projects, could be a lucrative side gig!

You unfortunately have a little time, I probably won't be done with my parts and putting these together for a few weeks:/

The grinder uses 1-1/4" center hole grinding wheel, but I don't remember the arbor. It is some taper that is common to surface grinders.

I ended up getting a Bridgeport Clone by Birmingham, its a 10x54 table with a variable speed head and a 3HP motor! Its a beast compared to my old machine!

Thats pretty awesome about the caliper too! I didn't see that project, but it must have been a pretty nice one! I tend not to be on PM, they seem to have an irrational hatred for shapers, and I have an even less rational love for them

 

[ErichKeane]

Got my wheel in today and started grinding! Took about 2 hrs, but I got the first too bits ground well enough for their shape. These are 3/8" hex broaches, which were for ttabbal and myself, which I did since the biggest ones required less material removal and thus were easier!

I ground them at a 2 degree angle, so we should have plenty of clearance.

For the sizes I have:
T Bredehoft: 3/16, 5/32, and 1/8 hex
Ttabbal/myself: 3/8, 3/16 hex, 1/4" square
GunsofNaravone: 3,4,5mm hex
I still need to grind the inside relief on these, but 2 of 12 otherwise done

 

[ErichKeane]

I did 5mm as well (took an hour for itself even though I felt like I was cruising) but I found that the "depth" of the 3rd cut was tough to measure, so the hex might not be centered right it mics out pretty close on my surface plate, so perhaps it just looks worse than it is?

I'm going to have to figure out how to solve this for the smaller ones though.

 

[T Bredehoft]

My broaches don't need to be more than 2 diameters long....

 

[ErichKeane]

My broaches don't need to be more than 2 diameters long....

Yeah I might shorten the depth of cut on the smaller ones, it at least should prevent the root from getting so small.

 

[ErichKeane]

So I decided that I didn't like how the 5mm turned out, so I changed my strategy/setup. I took out the angle block and replaced it with a magnetic sine vise. This takes significant amount more time for my cycles, but is way more repeatable. I decided I would do 1 complete set of cuts (6) as a roughing pass, dress my wheel and go around another time to get a size reading, then 1 more time to final size.

I did the post-wheel dressing part on the 5mm to make it a 4mm, then started on a replacement 5mm. Sadly the part rotated on me during one of the cuts, and I didn't notice until it wasn't savable. So, 1 in the trash :/



I restarted the 5mm and this one went way better, other than taking about 2x the time as the previous ones. You'll note that the 5mm I also shortened how long the cutter is ground, hopefully this will strengthen it. The 5mm->4mm conversion I didn't have this option, so it is still full depth.

I measured the two 3/8 cutters, and 1 is pretty close to right, the other is a little rough. I think I'll just keep the rough one to myself.

That said, this step is seemingly taking a while I have 8 more cutters to go to get you all 3 of them (barring disaster or another mess up), and I likely will be doing 1x a day at this rate!

 

[GunsOfNavarone]

Remember...I'm flexible on sizes...if the smaller of them are very time consuming for material removal, I can go with 3/8" and 1/4"...what evs...