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## Broach bushing

I need to make a bushing for a 1/2" hub to cut a 1/8" keyway. I can't find the proper depth for the slot. Can someone point me in the right direction?
Thanks.
John R

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Make the depth of the slot the the same as the thickness of the broach and use shims to determine the depth of the cut. With a broach that small I would take three cuts 3 @ .020 and a finish at .005 for a total of .065
1/16 (.062)+.003 for clearance.

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The small Dumont broaches use just one shim. Take one cut without the shim and one cut with the shim and it's done. It may be above 1/2" that the broach will have two shims.

My Dumont 1/2" bushing measures OD-.497", the bottom of the slot to the back of the bushing is .110" thick. so that means the slot is .387 deep from the surface of the bushing to the base of the slot.

DON'T MEASURE THE DEPTH OF THE SLOT FROM THE SIDE OF THE SLOT AS YOU CUT IT. It has to be measured from the OD of the bushing or from the bottom of the slot to the back side. It is real easy to cut the slot to deep and then you have to use more shims than is provided with the broach.

I have made some bushings and it's real easy to make a mistake.

4. Patch Guest
Just measured one of my sets.

bushing dia. = .497
thickness of bushing at bottom of slot = .1026

shim #1 = .032
shim #2 = .049

Patch

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Originally Posted by Patch
Just measured one of my sets.

bushing dia. = .497
thickness of bushing at bottom of slot = .1026

shim #1 = .032
shim #2 = .049

Patch
Those figures mean nothing without the given thickness of the broach.

.

Make the bushing a few thou smaller than the hole it's to fit into, make sure you leave a cap on the bush so it doesn't just fall thru the hole. Then mike the smallest end of the broach. Mill the slot in the bush to the depth of the smallest end or starting end of the broach.
To test if it will all fit together, place a six inch rule over the slot you have just cut, then try to shove the small end of the broach into the bush under the ruler. This will soon tell you if it all will work, might have to take another small slice with the milling cutter, maybe you went a tad to deep, big deal, add a packer strip behind the broach and go at it as is normal broaching practice.

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## Square key(way) tables

Originally Posted by John R
I need to make a bushing for a 1/2" hub to cut a 1/8" keyway. I can't find the proper depth for the slot. Can someone point me in the right direction?
Thanks.
John R
John,
if I read you correctly, what you want is the details of square keys and keyways in a hole or on a shaft.

I didn't see "broatch" mentioned, so I presume it may not be needed. It is in inch and metric (mm) units.

If you are making a part for a broatch this may help.

I hope this is of assistance.

Sorry about the large file size but the original is pretty small and so I increased the resolution - and the file size.

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Thanks to all. I'm off and running.
John R

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Originally Posted by oldtiffie
John,

I didn't see "broatch" mentioned, so I presume it may not be needed. It is in inch and metric (mm) units.

.
Tiffie, it;s the name of the thread, "Broach Bushing" good reference tables you provided.

turn the bushing to the best fit you can. The width of the slot is obviously the width of the broach. I like to work carefully with that and minimize slop - broaches are fragile so i want it well support with minimal clearance. irrc i used a side milling cutter last time (better finish than end mills) and was careful to get the width dead on.

As for depth of the slot, its got to be just deep enough that when the bushing is in the hole, the broach will enter the slot without hitting the side of the hole and the first tooth starts to makes contact with the edge of the hole. As you know, two passes of the broach are required, the second with a shim - you can fine tune this with different thickness easily made from sheet steel if your bushing isn't producing a cut to the right depth.

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## Wearing my brooch!!!

Originally Posted by Mcgyver
Tiffie, it;s the name of the thread, "Broach Bushing" :
\$hit - so it is.
http://en.wikipedia.org/wiki/Broach_(metalworking)

Thanks and sorry.

I noticed that I spelled it "broatch" - must have been thinking of wearing my brooch after I put my lip-stick on!!!
http://en.wikipedia.org/wiki/Brooch

Option/number 3 here is my preferred way to go!!
http://www.thefreedictionary.com/broach

And having succeeded thus and being "three sheets into the wind" I would "broach-to" and then ar\$e over head (my excuse anyway!!).
http://query.nytimes.com/gst/fullpag...51C1A962958260