Shop Made Tools

[mickeyf]

For reasons mentioned, I don't trust simply deforming the bottom thread on a t-nut. I plugged my home made ones with a thin slice of rod, and welded that in so that there was zero chance of the stud extending through the bottom. Yes, it took a little longer, but even if you stop threading before you get to the very bottom, the stud itself can act as a tap if you are brutal enough, especially if there is only one thread's worth of nut left.

[Cenedd]

the stud itself can act as a tap if you are brutal enough.

Not with the chinesium-grade of studs that come with the clamp kits they can't!

That said, I treated myself to a selection of parallels that arrived today. Was quite pleased when the first pair of them - and I've only taken the time to measure one - were within 2 or 3 microns* in all dimensions.

*For a given definition of microns as they apply to an import digital mic - but repeatably at least.

[rcaffin]

when some ham fisted operator who is using the wrong length of stud keeps cranking on the wrench
That would be poor training by the owner or employer. Don't blame the tool.

Anyhow, I am the ONLY operator in my shop.

Cheers
Roger

[BMW Rider]

when some ham fisted operator who is using the wrong length of stud keeps cranking on the wrench
That would be poor training by the owner or employer. Don't blame the tool.

Anyhow, I am the ONLY operator in my shop.

Cheers
Roger

Same for me which means I have to take the blame when those incidents of cerebral flatulence happen. I like the idea of measures to prevent them and may look at using some of these ideas.

[mattthemuppet]

another way of preventing hold down studs jacking up a T-slot is to use a taper tap (or plug) and stop tapping just as the tip of the tap pokes through, leaving a bunch of untapped or partially tapped threads. Depending on the tap and t-nut thickness, you can easily manage the tapping to end up with 2/3 fully tapped threads and the rest incomplete at the bottom. Doesn't matter how hard you crank down, you're not going to tap a thread in steel with a bolt.

[BCRider]

another way of preventing hold down studs jacking up a T-slot is to use a taper tap (or plug) and stop tapping just as the tip of the tap pokes through, leaving a bunch of untapped or partially tapped threads. Depending on the tap and t-nut thickness, you can easily manage the tapping to end up with 2/3 fully tapped threads and the rest incomplete at the bottom. Doesn't matter how hard you crank down, you're not going to tap a thread in steel with a bolt.

I rather like this idea for the times I make my own T nuts. But I think I'd want to use an actual bottoming tap to get a clean thread right to the final stop point. Otherwise messing up at the top end with the wrong length stud could result in seriously wedging the stud into the T nut.

The few T nuts of my own that I've done I've simply staked the last thread in three spots to stop the bolt going through. Mind you since my shop made T nuts are not hardened like the nuts in my clamping kit forcing the stud through is certainly very much a risk. The use of a plug then bottoming tap would certainly stop this being an issue. So this is an idea I'll keep in mind for the future.

[wbc]

Yet Another Rotary Broach

Many $100's for a seldom needed tool? I don't think so. Junk and prior Web Art to the rescue... A simple, 4 pieces to machine,
design-as-you-go method was my madness.

The bearings were lying around first. Made it with two 6202 ball bearings, but ended up swapping one to a tapered 30202 roller
to address any question of axially abusing radial bearings. At any rate, both bearings are dimensionally interchangeable.
Then made the carrier spindle for the bearings and a broach-holding set screw. Then the barrel was bored out, the shank
turned and three holes tapped in the shank end. Then the shank end parted off with about a 3/8" thick flange.
Finally, a threaded retainer to hold the mish-mash.

Milled the shank flange at a 1 degree angle and re-assembled to test the wobble with a broach ground from end mill shank.
Deemed 1 degree resulted in too much force needed to get broaching action, so settled on a 2 degree leaning flange, and
a 2.5 degree relief of the broaches, which for me gave much easier broaching.

Ended up with broaches needing to be 1.5" long to null the tip wobble. Once satisfied, turned the OD of the whole
mish-mash concentric with the shank to get rid of the "Must have made this while drunk" effect.

[Tim Clarke]

I like it😀 I probably have everything I need. Someplace. Thanks for posting.

[Cenedd]

So the barrel ID, OD and spindle were all concentric. The shank was concentric but the end was milled off at an angle so when mated to the barrel the shank is at an angle. Then you turned the final OD down to make it look right. Is that right?
So if I've got it right you could also have turned a shank from the solid body by using a boring head on the mill for OD boring? Not trying to say it's be easier/better, just trying to get my head around how it works exactly.

[wbc]

Yep. Could dispense with the two piece barrel-shank arrangement and use a boring head and tilt the workpiece in a mill.
But I never made or used a broach before, and didn't know what angle best to use, so I took the exploratory route.
Making another having this experience as a model, could have made as a total of 3 pieces. But I think you have to
either use a CAD program or be good at geometry to figure out the proper tilt and offset for cutting the shank portion
as one unit, given a pre-determined length for the broaches so that their cutting ends intersect the point of zero wobble.

An example of various prior fancier art is better covered here:

https://www.hobby-machinist.com/thre...roaches.19945/

[BCRider]

Nice!

If I'm reading this right this style of tool has to be rotated against a stationary work piece. It could not be used in a lathe tail stock for example?

And if I'm thinking correctly that is because the offset angle has to rotate?

For a version that could be used in a lathe I could make one where the offset and angled bore for the broach would be only in the spindle and the body and shank would be axial and thus be able to remain motionless while the rotating angle wobbled around with the work piece?

[Hopefuldave]

Nice!

If I'm reading this right this style of tool has to be rotated against a stationary work piece. It could not be used in a lathe tail stock for example?

And if I'm thinking correctly that is because the offset angle has to rotate?

For a version that could be used in a lathe I could make one where the offset and angled bore for the broach would be only in the spindle and the body and shank would be axial and thus be able to remain motionless while the rotating angle wobbled around with the work piece?

Can be used in either, have it held stationary in the lathe tailstock against rotating workpiece, or vice-versa, as long as there's the ?nutuating? motion so the cutting edge point of contact moves around the circumference of the hole you're broaching.
I'm thinking that on the lathe it'd be possible to mount the rotary broach on the carriage and apply the offset angle by e.g. rotating its axis on the toolpost, that'd give power feed too? As long as the cutting face remained on centre it would correctly track the pilot hole, I think. I might have to try it!

Dave H. (the other one)

[BCRider]

Thinking more on this if the off center coning axis is reflected into the sleeve's bore by the angle on the arbor and mounting face then yeah, one could spin either work or the tool. Wbc, is that the case?

[Dave C]

I've tried to understand how a rotary broach works since first hearing of the things existence. All I've got so far is a headache🤔

[danlb]

I've tried to understand how a rotary broach works since first hearing of the things existence. All I've got so far is a headache🤔

In a nutshell, the work rotates and the broach rotates with it. Start with a hole in the work. The broach is on an eccentric that makes it wobble a few degrees. The wobble changes the edge of the broach that is cutting. It's as if you were slicing away the edges of the hole a sliver at a time.