Broaching , a question

[Snag]

I'm getting ready to broach my first keyway with an actual broach .
My question is about the shims , and how thick they need to be .
Measuring the difference between the first and last tooth on the broach
I get .062" and I'm wondering if that is the correct thickness for the
shims .

[Jim Wilkins]

"Snag" wrote in message news:ututu3$1u2oj$***@dont-email.me...

I'm getting ready to broach my first keyway with an actual broach .
My question is about the shims , and how thick they need to be .
Measuring the difference between the first and last tooth on the broach
I get .062" and I'm wondering if that is the correct thickness for the
shims .
Snag

-----------------------------

My 3/16" keyway broach came with an 0.050" shim. For the others I shear
strips of scrap sheetmetal and add one between passes until the key fits. My
guide bushings are all shop-made to eyeballed depth.

Thinner shims leave less unsupported broach, but if the shim is too thin to
hold the bend the broach may pull it through.

[Snag]

  I'm getting ready to broach my first keyway with an actual broach .
My question is about the shims , and how thick they need to be .
Measuring the difference between the first and last tooth on the broach
I get .062" and I'm wondering if that is the correct thickness for the
shims .
Snag
-----------------------------
My 3/16" keyway broach came with an 0.050" shim. For the others I shear
strips of scrap sheetmetal and add one between passes until the key
fits. My guide bushings are all shop-made to eyeballed depth.
Thinner shims leave less unsupported broach, but if the shim is too thin
to hold the bend the broach may pull it through.

I made a couple of shims from some .050" galvanized sheet . Probably
going to make some more of varying thickness so I can fine tune the
depth . I made the slot in the guide bushing the same depth - measured
from the round - as the width of the broach at the bottom end .
The project got delayed a bit because I stripped the old DRO off the
mill . The new ones are a lot better but there was a good bit of
fabrication to adapt to my mill .

[Jim Wilkins]

"Snag" wrote in message news:utvdti$2bued$***@dont-email.me...
On 3/26/2024 12:23 PM, Jim Wilkins wrote:
.....

I made a couple of shims from some .050" galvanized sheet . Probably
going to make some more of varying thickness so I can fine tune the
depth . I made the slot in the guide bushing the same depth - measured
from the round - as the width of the broach at the bottom end .
The project got delayed a bit because I stripped the old DRO off the
mill . The new ones are a lot better but there was a good bit of
fabrication to adapt to my mill .
Snag

-----------------------------

IIRC the proper depth of a key slot is half the width, measured from the cut
edges, so a square key will fit half way into each part. I tend to need
oddballs such as different width slots, the motor/pump shaft (metric?)
existing and the pulley matching one of my broaches, and a custom T shaped
key. There are even offset keys to advance timing on small engines modded
for racing.

[David Billington]

I'm getting ready to broach my first keyway with an actual broach . My
question is about the shims , and how thick they need to be .
Measuring the difference between the first and last tooth on the
broach I get .062" and I'm wondering if that is the correct thickness
for the shims .

Is it a shop made broach or bought. All my Dumont broaches come with
appropriate shims to cut the keyway to the correct depth.

[Snag]

Post by David Billington

I'm getting ready to broach my first keyway with an actual broach . My
question is about the shims , and how thick they need to be .
Measuring the difference between the first and last tooth on the
broach I get .062" and I'm wondering if that is the correct thickness
for the shims .

Is it a shop made broach or bought. All my Dumont broaches come with
appropriate shims to cut the keyway to the correct depth.

It's a couple of broaches only from eBay . I machined a guide slug
for it from some 416 SS I bought to "have some on hand in case I need
it" and pushed it with my 12/20* ton HF press . I made shims from some
.050" galvanized sheet I have on hand (being a Pack Rat is often a Good
Thing) and it worked out quite well . I'll never broach another keyway
on the lathe ...

*12 ton frame with a 20 ton air operated jack on it . I have beefed
up the frame where it was necessary .

[Bob La Londe]

Post by David Billington

Post by Snag
I'm getting ready to broach my first keyway with an actual broach .
My question is about the shims , and how thick they need to be .
Measuring the difference between the first and last tooth on the
broach I get .062" and I'm wondering if that is the correct thickness
for the shims .

Is it a shop made broach or bought. All my Dumont broaches come with
appropriate shims to cut the keyway to the correct depth.

  It's a couple of broaches only from eBay . I machined a guide slug
for it from some 416 SS I bought to "have some on hand in case I need
it" and pushed it with my 12/20* ton HF press .

416 is nice stuff. Fairly machinable, more rust resistant than chrome
molly (4140/4130), and pretty strong.

I made shims from some

.050"  galvanized sheet I have on hand (being a Pack Rat is often a Good
Thing) and it worked out quite well . I'll never broach another keyway
on the lathe ...

Sometimes you gotta do what you gotta do. Never say never. That
oddball will certainly curse your work shop now.

  *12 ton frame with a 20 ton air operated jack on it . I have beefed
up the frame where it was necessary .

I ran a 12 ton air jack on a 12 ton press, and I still tore it apart. I
also bent a 20 ton with a 20 ton jack. That being said, the 6 ton arbor
press has done all the straight broaching I've needed to do so far.

[David Billington]

Post by David Billington

Post by Snag
I'm getting ready to broach my first keyway with an actual broach .
My question is about the shims , and how thick they need to be .
Measuring the difference between the first and last tooth on the
broach I get .062" and I'm wondering if that is the correct
thickness for the shims .

Is it a shop made broach or bought. All my Dumont broaches come with
appropriate shims to cut the keyway to the correct depth.

  It's a couple of broaches only from eBay . I machined a guide slug
for it from some 416 SS I bought to "have some on hand in case I need
it" and pushed it with my 12/20* ton HF press . I made shims from some
.050"  galvanized sheet I have on hand (being a Pack Rat is often a
Good Thing) and it worked out quite well . I'll never broach another
keyway on the lathe ...
  *12 ton frame with a 20 ton air operated jack on it . I have beefed
up the frame where it was necessary .

Maybe some of the information in the Dumont catalogue would be of use.
It gives the broach lengths and the thickness and number of shims
required. https://kar.ca/pdf/catalog/en/Dumont_Catalog.pdf

[Snag]

Post by David Billington

Post by David Billington

Post by Snag
I'm getting ready to broach my first keyway with an actual broach .
My question is about the shims , and how thick they need to be .
Measuring the difference between the first and last tooth on the
broach I get .062" and I'm wondering if that is the correct
thickness for the shims .

Is it a shop made broach or bought. All my Dumont broaches come with
appropriate shims to cut the keyway to the correct depth.

  It's a couple of broaches only from eBay . I machined a guide slug
for it from some 416 SS I bought to "have some on hand in case I need
it" and pushed it with my 12/20* ton HF press . I made shims from some
.050"  galvanized sheet I have on hand (being a Pack Rat is often a
Good Thing) and it worked out quite well . I'll never broach another
keyway on the lathe ...
  *12 ton frame with a 20 ton air operated jack on it . I have beefed
up the frame where it was necessary .

Maybe some of the information in the Dumont catalogue would be of use.
It gives the broach lengths and the thickness and number of shims
required. https://kar.ca/pdf/catalog/en/Dumont_Catalog.pdf

I figure the shim should be the same thickness as the difference
between the first and last tooth - mine measure .062 . This will keep
the "pilot" on the end in contact with the bottom of the groove being
cut . I noticed a variation in the depth on that keyway I cut yesterday
... I think because the broach was not bottomed out in the groove in the
pilot bushing .

[David Billington]

Post by David Billington

Post by David Billington

Post by Snag
I'm getting ready to broach my first keyway with an actual broach
. My question is about the shims , and how thick they need to be .
Measuring the difference between the first and last tooth on the
broach I get .062" and I'm wondering if that is the correct
thickness for the shims .

Is it a shop made broach or bought. All my Dumont broaches come
with appropriate shims to cut the keyway to the correct depth.

  It's a couple of broaches only from eBay . I machined a guide slug
for it from some 416 SS I bought to "have some on hand in case I
need it" and pushed it with my 12/20* ton HF press . I made shims
from some .050"  galvanized sheet I have on hand (being a Pack Rat
is often a Good Thing) and it worked out quite well . I'll never
broach another keyway on the lathe ...
  *12 ton frame with a 20 ton air operated jack on it . I have
beefed up the frame where it was necessary .

Maybe some of the information in the Dumont catalogue would be of
use. It gives the broach lengths and the thickness and number of
shims required. https://kar.ca/pdf/catalog/en/Dumont_Catalog.pdf

  I figure the shim should be the same thickness as the difference
between the first and last tooth - mine measure .062 . This will keep
the "pilot" on the end in contact with the bottom of the groove being
cut . I noticed a variation in the depth on that keyway I cut
yesterday ... I think because the broach was not bottomed out in the
groove in the pilot bushing .

I've seen that with mine before like yesterday where the top of the
broach was leaning towards me a bit, cutting edges forward, so I
corrected it for the second pass for a 4mm key. I'll check my broaches
tomorrow and see how the shim thickness correlates to the height
increase along the broach and report back.

[Snag]

Post by David Billington

Post by David Billington

Post by David Billington

Post by Snag
I'm getting ready to broach my first keyway with an actual broach
. My question is about the shims , and how thick they need to be .
Measuring the difference between the first and last tooth on the
broach I get .062" and I'm wondering if that is the correct
thickness for the shims .

Is it a shop made broach or bought. All my Dumont broaches come
with appropriate shims to cut the keyway to the correct depth.

  It's a couple of broaches only from eBay . I machined a guide slug
for it from some 416 SS I bought to "have some on hand in case I
need it" and pushed it with my 12/20* ton HF press . I made shims
from some .050"  galvanized sheet I have on hand (being a Pack Rat
is often a Good Thing) and it worked out quite well . I'll never
broach another keyway on the lathe ...
  *12 ton frame with a 20 ton air operated jack on it . I have
beefed up the frame where it was necessary .

Maybe some of the information in the Dumont catalogue would be of
use. It gives the broach lengths and the thickness and number of
shims required. https://kar.ca/pdf/catalog/en/Dumont_Catalog.pdf

  I figure the shim should be the same thickness as the difference
between the first and last tooth - mine measure .062 . This will keep
the "pilot" on the end in contact with the bottom of the groove being
cut . I noticed a variation in the depth on that keyway I cut
yesterday ... I think because the broach was not bottomed out in the
groove in the pilot bushing .

I've seen that with mine before like yesterday where the top of the
broach was leaning towards me a bit, cutting edges forward, so I
corrected it for the second pass for a 4mm key. I'll check my broaches
tomorrow and see how the shim thickness correlates to the height
increase along the broach and report back.

This was a case of I started the cut on the lathe , cranking the
carriage forward and back . I think the taper would have self-corrected
if I'd used a .062" shim instead of the .050" .

[David Billington]

Post by David Billington

Post by David Billington

Post by David Billington

Post by Snag
I'm getting ready to broach my first keyway with an actual
broach . My question is about the shims , and how thick they
need to be . Measuring the difference between the first and last
tooth on the broach I get .062" and I'm wondering if that is the
correct thickness for the shims .

Is it a shop made broach or bought. All my Dumont broaches come
with appropriate shims to cut the keyway to the correct depth.

  It's a couple of broaches only from eBay . I machined a guide
slug for it from some 416 SS I bought to "have some on hand in
case I need it" and pushed it with my 12/20* ton HF press . I made
shims from some .050"  galvanized sheet I have on hand (being a
Pack Rat is often a Good Thing) and it worked out quite well .
I'll never broach another keyway on the lathe ...
  *12 ton frame with a 20 ton air operated jack on it . I have
beefed up the frame where it was necessary .

Maybe some of the information in the Dumont catalogue would be of
use. It gives the broach lengths and the thickness and number of
shims required. https://kar.ca/pdf/catalog/en/Dumont_Catalog.pdf

  I figure the shim should be the same thickness as the difference
between the first and last tooth - mine measure .062 . This will
keep the "pilot" on the end in contact with the bottom of the groove
being cut . I noticed a variation in the depth on that keyway I cut
yesterday ... I think because the broach was not bottomed out in the
groove in the pilot bushing .

I've seen that with mine before like yesterday where the top of the
broach was leaning towards me a bit, cutting edges forward, so I
corrected it for the second pass for a 4mm key. I'll check my
broaches tomorrow and see how the shim thickness correlates to the
height increase along the broach and report back.

  This was a case of I started the cut on the lathe , cranking the
carriage forward and back . I think the taper would have
self-corrected if I'd used a .062" shim instead of the .050" .

This is what I measured.

Broach list Dumont No 10 set
Size    Start     End     Diff    Teeth     /Tooth    Shim
1/8"    0.390    0.421     0.031    16    0.0021    0.031 x 1
3/16"    0.377    0.429    0.052    16    0.0035    0.050 x 1
1/4"    0.587    0.651    0.064    22    0.0030    0.062 x 1
3/8"    0.569    0.633    0.064    22    0.0030    0.062 x 2

The /Tooth is Diff /(Teeth - 1) . Looks like your original assumption
about the shim thickness is correct.

[Snag]

Post by David Billington

Post by David Billington

Post by David Billington

Post by David Billington

Post by Snag
I'm getting ready to broach my first keyway with an actual
broach . My question is about the shims , and how thick they
need to be . Measuring the difference between the first and last
tooth on the broach I get .062" and I'm wondering if that is the
correct thickness for the shims .

Is it a shop made broach or bought. All my Dumont broaches come
with appropriate shims to cut the keyway to the correct depth.

  It's a couple of broaches only from eBay . I machined a guide
slug for it from some 416 SS I bought to "have some on hand in
case I need it" and pushed it with my 12/20* ton HF press . I made
shims from some .050"  galvanized sheet I have on hand (being a
Pack Rat is often a Good Thing) and it worked out quite well .
I'll never broach another keyway on the lathe ...
  *12 ton frame with a 20 ton air operated jack on it . I have
beefed up the frame where it was necessary .

Maybe some of the information in the Dumont catalogue would be of
use. It gives the broach lengths and the thickness and number of
shims required. https://kar.ca/pdf/catalog/en/Dumont_Catalog.pdf

  I figure the shim should be the same thickness as the difference
between the first and last tooth - mine measure .062 . This will
keep the "pilot" on the end in contact with the bottom of the groove
being cut . I noticed a variation in the depth on that keyway I cut
yesterday ... I think because the broach was not bottomed out in the
groove in the pilot bushing .

I've seen that with mine before like yesterday where the top of the
broach was leaning towards me a bit, cutting edges forward, so I
corrected it for the second pass for a 4mm key. I'll check my
broaches tomorrow and see how the shim thickness correlates to the
height increase along the broach and report back.

  This was a case of I started the cut on the lathe , cranking the
carriage forward and back . I think the taper would have
self-corrected if I'd used a .062" shim instead of the .050" .

This is what I measured.
Broach list Dumont No 10 set
Size    Start     End     Diff    Teeth     /Tooth    Shim
1/8"    0.390    0.421     0.031    16    0.0021    0.031 x 1
3/16"    0.377    0.429    0.052    16    0.0035    0.050 x 1
1/4"    0.587    0.651    0.064    22    0.0030    0.062 x 1
3/8"    0.569    0.633    0.064    22    0.0030    0.062 x 2
The /Tooth is Diff /(Teeth - 1) . Looks like your original assumption
about the shim thickness is correct.

Thanks for getting back with that info . It seemed intuitive , but ya
never know . Now we know .