of the modifications to make the HF power feed fit my RF45 clone mill .
I see type a and type b broaches , both listed as push type . I don't
know what that means ... I just know that scraping a key slot in a bore
on the lathe ain't going to happen again . I presume that push type
means that I can push the broach thru the work with my hydraulic press .
I also understand that the broach needs to be shimmed for each pass
until desired depth is reached - Is that correct ?
This may help
. I have a Dumont metric and inch broach set and not all require
shimming, the smaller sizes can cut the slot in a single pass, whereas
larger sizes may have one or more shims depending on the keyway depth.
standard keyway dimensions. Dumont may have the shim pack details on
their site, I haven't looked.
Broaches are brittle and likely to break if not pushed straight in, or
if the work shifts on a less than ideal support. I prefer to use an
arbor press because it gives more feel.
The shims extend the cutting depth of the broach by allowing multiple
passes. You can make shims from sheet metal if you don't have the
"right" size, but you can also custom-fit the key to whatever slot
depth the broach gives you. I've had good luck with tee-shaped keys
when I didn't have a broach the size of the shaft slot. A key that's a
snug fit in either the shaft or the hub slot is less likely to fall
and get lost during disassembly. If the shaft runs in bearings I make
the other side a sliding fit to avoid having to pound on the assembly.
A little clearance in slot depth helps avoid the key jamming from
I bought import broaches from Enco and make the guides and shims as
Whenever you buy a single broach or a set all the shims neded should
be included. The larger size broaches require more passes, hence more
shims. An arbor press is good for broaching One thing to watch out for
when broaching is the broach getting crooked. Because the broach is
tapered in steps the teeth will sometimes dig in and the back of the
broach will start to come away from the bushing. So when you first
start the broach press it in a little and the relieve the pressure so
that the broach can spring back if need be. You will either need to
but a bushing for your part or make your own. I have made lots of
custom bushing for broaching. For odd size holes and for tapered
So that's why they sometimes shift when I release pressure on the
arbor press handle. I thought it might be the random scrap that
bridged the opening in the press bed.yielding a little. I don't risk
my best straight bar stock for that.
Yes -- with a caution: Every quarter inch or so -- back up the
press and restart to allow the top end of the broach to re-center
properly. If it walks too far off center, you will break the broach.
You need a plug which fits into the hole with an external keyway
to guide the broach, and a shoulder to keep the plug from falling
through the bore on the workpiece.
Depends on size -- ranges from zero to three shims supplied with
the broach in the storage tube. Yes, your first pass is with no shim,
then add shims until you have all of them used. Having the shims means
that the broach does not have to be so long that the hydraulic press
will have to be reset several times to accommodate the whole stroke.
I've not used them on either brass or aluminum. I think that
with brass you can get away with no lubes. With aluminum, I would spray
it with WD-40 or Kerosene which usually make good cutting lubes on
On Wednesday, August 29, 2018 at 4:14:27 PM UTC-4, Terry Coombs wrote:
I have cut one keyway on the lathe and understand not wanting to do that ag
But you inspired me to search the internet for a better solution. And I th
ink I found one. If you search on " Slotter keyway cutter for minilathe "
you should find an article from Model Engineering which is close to good.
Basically it is a ram that mounts on the cross slide and is manually operat
ed. Still a fairly slow process, but it looks like it would be fairly simp
le to make the ram operated by air and retracted by a spring. With a simp
le circuit to activate the ram , you could probably get one stroke per seco
nd. Then you could use a stepper motor to move the cross slide, but that w
ould probably not worth doing.
I am not planning on actually making such a kludge. I don't have a need ri
ght now. But it is fun to think of projects like that.
On 8/31/2018 10:33 AM, firstname.lastname@example.org wrote:
Well that would beat the way I've been doing it . I've been using my
small boring bar set dead on center (vertically) and moving the entire
saddle assembly with the hand crank , advancing with the cross slide for
each stroke . Done it vertically with a cutter held in the spindle of
the mill too ... but decided that's a bit too rough on the pinion gear
setup the moves the quill up and down .
I did that when I made an L00 mount for metal spinning chucks and it
worked but I wouldn't want to do it again in a hurry. Most of the
material was milled out but I still had to square it up to fit the L00
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