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Single point keyway broach
- Thread starter Crosche
- Start date
Just a guess but I think its a combination of repeated cycling (in their case CNC driven), teeny DOC in-feeds per stroke and a very rigid system. Most carbides are less tolerant to intermittent cutting so if your setup is manually driven & not as tight (radially) you might have to take that into account. But if you can find an insert with suitable edge geometry/orientation & cheap, then having it replaceable like that certainly makes sense.
I've seen some pics of old school broaching bars in what looks like a glorified boring bar with HSS bits, lever operated stroking mechanism where (hobbyists) did it in the lathe. Some very satisfactory results in cast iron & mild steel. But the trick seems to be biggest bar you can accommodate for rigidity & take your time (small in-feed). I've only done this once myself & it wasn't pretty. My spindle cant be locked so I left it in a low gear. I traversed the carriage with every pass so it wasn't a clean stroke like with a dedicated mechanism. If I had more to do I think I'd build something.
Thinking about this some more, there is no reason you couldn't use HSS in lay down mode similar to the insert. When it sticks out like a boring bar it lacks support & now you have to secure it in ideally a square hole & set screw business, whereas lay-down you could mill a slot. Seems to me more rigid against stroking forces.
I've seen some pics of old school broaching bars in what looks like a glorified boring bar with HSS bits, lever operated stroking mechanism where (hobbyists) did it in the lathe. Some very satisfactory results in cast iron & mild steel. But the trick seems to be biggest bar you can accommodate for rigidity & take your time (small in-feed). I've only done this once myself & it wasn't pretty. My spindle cant be locked so I left it in a low gear. I traversed the carriage with every pass so it wasn't a clean stroke like with a dedicated mechanism. If I had more to do I think I'd build something.
Thinking about this some more, there is no reason you couldn't use HSS in lay down mode similar to the insert. When it sticks out like a boring bar it lacks support & now you have to secure it in ideally a square hole & set screw business, whereas lay-down you could mill a slot. Seems to me more rigid against stroking forces.
An interesting thing that I found during my broaching experience was that when I turned the cutting tool upside down and used a pull instead of a push that there was less deflection and the chips that were produced were cleared from the cut rather than stacking up at the end of the keyway channel. Were I not cutting a keyway in a blind hole I am sure that chip clearing wouldn't have been an issue.
Dabbler
ersatz engineer
Another thing that will help stop breaking cutters if you are cutting on the downstroke... You drill a hole a little larger than your keyway, right where the keyway is. this allows the chip to spearate cleanly rather than becoming 'hanging chaff' and piling onto the next one, etc.
-- great vid, BTW!
-- great vid, BTW!
Hey John,
I did as you advised, but the problem was that the hole that I drilled for the keyway didn't extend to the bottom of the sleeve and therefore the chips didn't break off, they just clung to the side wall.
Got it. That makes sense.
The pieces were water jet cut and I assembled & welded them. The 9" sanding disk plate was purchased.
What did the water jet cutting cost?
It's been awhile, but as I recall the cost was $60 per frame.
Hi Peter,
There were 3 frames cut in total and yes, that is a 2" x 72" belt grinder in the background; however it's fully operational.
Yes, I have a VFD already attached to my belt sander. I am going to install a 3 way switch to share the output of the VFD with the two sanders.