# Poor mans slotting head



## timo_gross (Apr 29, 2022)

Hello, 

I am getting side tracked all the time . Reading this in a gear cutting thread. .....  



Ghosty said:


> Hi All,
> Now just the engine, still need to do the 1/16" key way in the drive gear, then heat treat the gears.
> Cheers
> Andrew



Results in fixing my poor mans slotting head. Replaced the not very successful dove tail with a 2nd hand linear rail.
Is it wasted time? Anyway sort of a fun project. As drive it has a 10:1 used gear motor.




Now I have to remove the spindle head from the milling machine in order to mount the heavy thing. A better change over solution would be clever. 

I cut some gear rack out of 6 mm brass stock. It behaves with the diy gear (right) and the plastic gear from scrapped printer.





How to align a hole properly relative to the cutter is the challenge now. If anyone has a good tip it would be nice.


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## djc (May 2, 2022)

timo_gross said:


> How to align a hole properly relative to the cutter is the challenge now.



I can only speak for slotting in a shaper, but it might give you some ideas.

The slotting bar in a shaper is round, with a square hole through it for the toolbit. I make a bush OD the size of the hole to be slotted, ID the diameter of the slotting bar. Push the part onto it, touch it against the means of clamping (vise, angle plate) and it is automatically aligned.

If your bar is square and vertical and looks to use a round tool bit, you could use a round bar with a perpendicular hole in it the size of the toolbit, clamped vertically.

The principle is to align the part with the cutting tool and then clamp it rather than trying to align the tool with the part after clamping.


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## timo_gross (May 2, 2022)

djc said:


> The principle is to align the part with the cutting tool and then clamp it rather than trying to align the tool with the part after clamping.


Hello, thank you for the reply. The vertical DIY thing and the shaper are probably quite similar, all I need to do is tilt my head 90° .
My flimsy hobby mill is not as rigid, that I try to compensate with small cuts.
Trying to use some sort of alignment pin, or bush and let the work float before clamping is probably an efficient approach.
To use a round slotting bar with a separate tool bit is maybe difficult, because my bore in the gear is only 8 mm diameter, but when I grind the slotting tool out of 8 mm HSS bar instead of square I might use the upper part for alingment and the lower part for slotting. (made a draft, how I imagine the tool)
Then I just need a clamp adapter to install the bar.

Gretings Timo


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## timo_gross (May 2, 2022)

I tried to make the tool, now next step is to try to fix it to the machine somehow.



Working on it.


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## timo_gross (May 2, 2022)

[QUOTE="djc, post: 378530, member: 181"

The principle is to align the part with the cutting tool and then clamp it rather than trying to align the tool with the part after clamping.
[/QUOTE]
Hello, yes it worked. Maybe this becomes the usual procedure. 
I lowered the tool with the cylindrical part into the bore, then I clamped and zeroed the position. Adjust z-height and ... GO!.


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## Drawfiler (May 3, 2022)

Why are you not using a push broach, they are not too expensive here in the uk, do a good job and  your time is spent modelling not toolmaking!


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## timo_gross (May 3, 2022)

Drawfiler said:


> Why are you not using a push broach, they are not too expensive here in the uk, do a good job and  your time is spent modelling not toolmaking!


Yes you caught me. Is toolmaking part of the hobby, or procrastination? Maybe both , lots of tooling made, not so many models yet... .

Seriously: I was trying to find a push broach locally at first, but no one seems to use them here unless it is for mass production.
I do not have a press to push the push broach, would the lathe tail stock be good enough?

Greetings Timo


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## Vietti (May 3, 2022)

Some home gunsmiths use a large, Bridgeport type mill quill to broach the mortise on single shot rifles etc.  I suppose a smaller mill might work if the depth of cut was smaller.


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## timo_gross (May 3, 2022)

Vietti said:


> Some home gunsmiths use a large, Bridgeport type mill quill to broach the mortise on single shot rifles etc.  I suppose a smaller mill might work if the depth of cut was smaller.



It actually works fine now. Internal 2 mm keyways into 10 mm wide mild steel gears took about 90 seconds to setup and do the cut.
Depth of cut is in the range of 0.02 aka 1/1000" per stroke. I do not see much gain in trying to speed that up much further at the moment. 
The HSS tool seems to be "happy with mild steel".


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## Drawfiler (May 3, 2022)

So the toolmaking paid off, I make quite a few gears with key ways and quickly found that using a slotting head rather slow and went for broaching, I also find the keyways are less likely to be tapered.


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## SmithDoor (May 3, 2022)

Drawfiler said:


> So the toolmaking paid off, I make quite a few gears with key ways and quickly found that using a slotting head rather slow and went for broaching, I also find the keyways are less likely to be tapered.


I keep thinking of using a crank and drill quill on the mill. Maybe using a low speed hand drill or a gear motor to supply the power. 

Dave


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## dazz (May 4, 2022)

Hi
I made a simple tool that is held in the quill of a poor man's Taiwan milling machine.


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## timo_gross (May 4, 2022)

Drawfiler said:


> So the toolmaking paid off, I make quite a few gears with key ways and quickly found that using a slotting head rather slow and went for broaching, I also find the keyways are less likely to be tapered.


Hello,

I just found out that I can now buy a 2 mm keyway broach without bushings for under 20 USD from the Aliexpress people. 
When I checked a while ago I could not find smaller than 4 mm ones.

I make myself still believe it paid off.
For the fun of trying to make my own "working Model" of a slotting machine. Not made from castings, it is more the bar stock type though  .
A taper is at least not "visible", if I measure precise enough .... it will for sure reveal a mess, so I better not measure. (but usable for now)
Because the tool has the same dimension as the bore, 8 mm in the slotting direction, it is possibly as stiff as it can be made. (unless I grind one from carbide and beef up the entire setup).
Tools are cheap; time for tool grinding not factored in. The HSS blanks do not break the bank at under 2 Pounds per piece, good to make two slotters.

I hope I can use the machine to make some other slotting jobs. Gear racks are already possible.
Square holes?



dazz said:


> Hi
> I made a simple tool that is held in the quill of a poor man's Taiwan milling machine.



How big is your tool? It is for sure very versatile, you can make a lot of different shaped cutters for it.

The machine on the fotos is originally from China (I guess), it lives in Taiwan, the Japanese gear motor is a 0.4 kW 4-pole running between nothing and 90Hz.
Used cutting parameters were 230 strokes per Minute and infeed of 2mm/min.

I guess hand cranking can become boring. I also think that the relative high speed gives it some momentum and that probably helps with the cut.

Greetings Timo


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## dazz (May 4, 2022)

timo_gross said:


> Hello,
> 
> I just found out that I can now buy a 2 mm keyway broach without bushings for under 20 USD from the Aliexpress people.
> When I checked a while ago I could not find smaller than 4 mm ones.
> ...


It is as big as you need.
Since making that tool, I now have a Deckel clone milling machine with a slotter.
It works the same except that it is now motor driven


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## wazrus (May 4, 2022)

Broaches. I do have few, they are pricey little items and the market for shorter broaches isn't all that good. So I've made my own, using pieces of simple round steel to suit the job and the cutter bars are about 200mm long, machined with a taper on the back, to allow .015" cuts per pass. The round steel has a very deep keyway machined, of a length to allow the cutter bar to seat, The cutter bar is simply packed up, with each successive cut, to allow a 0.15" cut per pass. There is a small brass thrust 'plug' used at the ends of the bar, in the slot. the cutter bars are fairly simply made from HSS bar of, say 3/16"or 1/8" thickness or whatever, by 1/2". The teeth are cut using a narrow wheel in an angle grinder mounted on a fixture and the bar is moved back-and-forth for each tooth. Side clearance I've found to be unneccessary; the cutters are quite parallel. The tooth form is not unlike that used by circular timber saws, without the 'set'. The broaches are pushed through the work with a 3T mandrel press. I've cut dozens of keyways in most materials with complete success and the broach cutters are quite easily sharpened. I've never broken one of those broaches. I do have a shaper and 'my' broaches have pretty much replaced the shaped process for keyways.


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## dazz (May 4, 2022)

Hi
This is the latest design for a slotter tool.  This is designed to make a blind round hole into a square one.  
The hole is too small to fit a tool holder so the round bit will be cut square to fit in the hole and cut it into a square.

The alternative is to braze a piece of HSS into a slot as shown in the 2nd tool holder.
None of these can be purchased, but they are easy to make.


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## timo_gross (May 4, 2022)

dazz said:


> Hi
> This is the latest design for a slotter tool.  This is designed to make a blind round hole into a square one.
> The hole is too small to fit a tool holder so the round bit will be cut square to fit in the hole and cut it into a square.
> 
> ...


If you square up the blind hole, is the cutter simply going up and down? Were are the chips ending up?


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## dazz (May 4, 2022)

Hi
I will bore a groove in the base of the hole to provide chip and tool clearance.
Bad things would happen if the tool just stopped at the end of the hole.


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## Ozwes007 (May 5, 2022)

Blind hole keyways are usually terminated with a hole slightly over the key size. This maintains the structural integrity of the unit being keyed. Undercutting can lead to failure at the undercut.


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## Richard Hed (May 6, 2022)

Drawfiler said:


> Why are you not using a push broach, they are not too expensive here in the uk, do a good job and  your time is spent modelling not toolmaking!


You can even build a broach if you can heat ttreat.


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## timo_gross (May 6, 2022)

Ozwes007 said:


> Blind hole keyways are usually terminated with a hole slightly over the key size. This maintains the structural integrity of the unit being keyed. Undercutting can lead to failure at the undercut.


Did not get it at first. Drill the hole 90° to slotting direction and all of a sudden it makes sense.


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## 76dave (May 7, 2022)

For a blind hole, have you considered using a rotary wobble broach. A simple design for one is shown at "mikesworkshop.weebly.com"


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## dazz (May 7, 2022)

Hi
It is easier/faster for me to make a tool for my slotter than than a wobble broach.   In addition, a slotting tool is far more versatile. 
For a blind hole a wobble broach would still need clearance at the base of the hole.


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## timo_gross (May 7, 2022)

76dave said:


> For a blind hole, have you considered using a rotary wobble broach. A simple design for one is shown at "mikesworkshop.weebly.com"



Hello,
yes and no. Yes I had a look into rotary broaching. No I did not even try a key way in blind holes or rotary broaching a keyway. 
Before I continued working on the slotting head, I found this link:









						Double Keyway Broach | Custom Keyway Rotary Broaches | Polygon Solution
					

Double Keyway Rotary Broaches can be custom made to your specifications or print. Fast Delivery! Precision made in the USA by Polygon Solutions 239-628-4800




					www.polygonsolutions.com
				




It gives some background information on the rotary broaching. I abandoned the idea of using a rotary broach (for that particular task). For some smaller squares or hex a rotary broach is nice to have. 
Rotary broaches are limited in depth, as far as I know.

Greetings Timo

(p.s. I am not sponsored or related to this company, just found their explanation to be useful)


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## Alec Ryals (May 7, 2022)

use the mill guill by hand


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## timo_gross (May 8, 2022)

Alec Ryals said:


> use the mill guill by hand


Yes, sometimes an option. But ... the mill in question does not even have a quill . It looked like this at some point.





Running the stepper motor driven head up and down is very slow, it would take forever. (do not ask why I know this  )


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## Ozwes007 (May 11, 2022)

Rotary broaching is a nice technic. Made one to put a dodecahedron hole through some gears for a gearbox I made years ago. Tooling can be costly to make though, depends on what you are cutting.


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## william_b_noble (Sep 4, 2022)

you may find this useful: How Rotary Broaching Works by Polygon Solutions
commercial rotary broaches aren't terribly cheap when new but they will make your square/hex/splined hole really efficiently


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## wazrus (Sep 4, 2022)

Keyway broaching usually implies a nice, expensive - and easily broken - 'push' broach. Industrial convention is that broaches should be 'pulled' and that's OK if you have the wherewithal/space etc. My broaching is 'pushed' and the broaches I make myself. Push broaching is sort of asking for broken broaches, so it's a matter of support for the broach, more than anything else. My shop made broaches are simply bits of rectangular HSS - readily available - with teeth cut using a cutting disc in an angle grinder rigidly mounted and the work (the broach blank) is reciprocated underneath. Of course, the blank is packed or the grinder is lowered to have the tooth depth where you want it. The cutoff disc will do quite a good job and do it quite quickly. Once the teeth are cut. it's a fairly simple matter to 'angle' the disc to grind a little relief on the crown of each tooth. The teeth are not unlike those on a circular saw, but without the 'set'. Chip clearance isn't quite the same issue it is with a circular saw, so 'set' isn't necessary, nor is side rake. The 'support' comes from a broach 'body' of round MS, with a groove to suit the HSS broach blank milled along it. It will probably be a very deep groove, so it takes a,little more time to have it deep enough for the HSS blank to pretty much disappear. I found the easiest way to 'set' the depth of cut was to angle the groove bottom, so the broach will cut about .015" at each pass. A few .015" metal packing strips underneath the broach body, in the groove, will have pretty reasonable keyways. My 'broaches' are only about 6" long, so the depth of cut is a bit limited. I have broaches for 1/8", 3/16" and 1/4" and 3,4. 5 and 6mm and bodies of 12, 13, 14, 15, 16, 18, 19 and 20mm. The body 'fir' doesn't have to precisely suit the hole, so, for instance, 19mm is quite OK for 3/4"


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## deverett (Sep 4, 2022)

wazrus said:


> Keyway broaching usually implies a nice, expensive - and easily broken - 'push' broach. Industrial convention is that broaches should be 'pulled' and that's OK if you have the wherewithal/space etc. My broaching is 'pushed' and the broaches I make myself. Push broaching is sort of asking for broken broaches, so it's a matter of support for the broach, more than anything else. My shop made broaches are simply bits of rectangular HSS - readily available - with teeth cut using a cutting disc in an angle grinder rigidly mounted and the work (the broach blank) is reciprocated underneath. Of course, the blank is packed or the grinder is lowered to have the tooth depth where you want it. The cutoff disc will do quite a good job and do it quite quickly. Once the teeth are cut. it's a fairly simple matter to 'angle' the disc to grind a little relief on the crown of each tooth. The teeth are not unlike those on a circular saw, but without the 'set'. Chip clearance isn't quite the same issue it is with a circular saw, so 'set' isn't necessary, nor is side rake. The 'support' comes from a broach 'body' of round MS, with a groove to suit the HSS broach blank milled along it. It will probably be a very deep groove, so it takes a,little more time to have it deep enough for the HSS blank to pretty much disappear. I found the easiest way to 'set' the depth of cut was to angle the groove bottom, so the broach will cut about .015" at each pass. A few .015" metal packing strips underneath the broach body, in the groove, will have pretty reasonable keyways. My 'broaches' are only about 6" long, so the depth of cut is a bit limited. I have broaches for 1/8", 3/16" and 1/4" and 3,4. 5 and 6mm and bodies of 12, 13, 14, 15, 16, 18, 19 and 20mm. The body 'fir' doesn't have to precisely suit the hole, so, for instance, 19mm is quite OK for 3/4"


Any chance of showing us a few pics of your home made broaches, please?

Dave
The Emerald Isle


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## William May (Sep 4, 2022)

wazrus said:


> Keyway broaching usually implies a nice, expensive - and easily broken - 'push' broach. Industrial convention is that broaches should be 'pulled' and that's OK if you have the wherewithal/space etc. My broaching is 'pushed' and the broaches I make myself. Push broaching is sort of asking for broken broaches, so it's a matter of support for the broach, more than anything else. My shop made broaches are simply bits of rectangular HSS - readily available - with teeth cut using a cutting disc in an angle grinder rigidly mounted and the work (the broach blank) is reciprocated underneath. Of course, the blank is packed or the grinder is lowered to have the tooth depth where you want it. The cutoff disc will do quite a good job and do it quite quickly. Once the teeth are cut. it's a fairly simple matter to 'angle' the disc to grind a little relief on the crown of each tooth. The teeth are not unlike those on a circular saw, but without the 'set'. Chip clearance isn't quite the same issue it is with a circular saw, so 'set' isn't necessary, nor is side rake. The 'support' comes from a broach 'body' of round MS, with a groove to suit the HSS broach blank milled along it. It will probably be a very deep groove, so it takes a,little more time to have it deep enough for the HSS blank to pretty much disappear. I found the easiest way to 'set' the depth of cut was to angle the groove bottom, so the broach will cut about .015" at each pass. A few .015" metal packing strips underneath the broach body, in the groove, will have pretty reasonable keyways. My 'broaches' are only about 6" long, so the depth of cut is a bit limited. I have broaches for 1/8", 3/16" and 1/4" and 3,4. 5 and 6mm and bodies of 12, 13, 14, 15, 16, 18, 19 and 20mm. The body 'fir' doesn't have to precisely suit the hole, so, for instance, 19mm is quite OK for 3/4"


All my broaches are push broaches, that is all I have ever used. I have guides and shims in sets for them all and have never had one break. Are you push broaching with no guide and no shims? I have from 1/16" up to 1"  in slotting, hexes, and squares, and have never had a problem. Are you using some lubricant? Bill


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## timo_gross (Sep 5, 2022)

William May said:


> All my broaches are push broaches, that is all I have ever used. I have guides and shims in sets for them all and have never had one break. Are you push broaching with no guide and no shims? I have from 1/16" up to 1"  in slotting, hexes, and squares, and have never had a problem. Are you using some lubricant? Bill


How do you push the broach? I am asking, because I made a diy broach and then came to the conclusion that it would require some sort of proper press to use it. Doing it with the drill press worked barely and it did not "feel right".
I do not have any press in the workshop.

I rotated a workpiece a little bit at a time, then made a tiny slot at a time   . Not a single keyway just tiny slots.



Of course one slot ended up too big.


But it was a proof of concept and it works.

Greetings Timo


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## wazrus (Sep 5, 2022)

Attache are pikkies of the homemade broaches. I do not have many 'bought' broaches, as they are so expensive, at least in Australia - where everything is expensive. I have one short commercial broach: any takers? And I do have all the gear for the commercial broaches and I do 'push' them in use. However, 'my' broaches have stood all the rigours of use in all sorts of material. The pix show some flame-cut, from 3/4"x6" mild steel wheels. The broach drive is from a 3T mandrel press and while this may sound a little underwhelming, it's simply a matter using thinner shims, if the going is a bit tough. For final sizing, I have a collection of thicker shims and when I'm near the depth required, I swap to the thicker bit and then finish off the lot with that shim. The broaches are quite simply sharpened in the same setup I used to cut the teeth. By the way, 'quarter' my loco drivers using the keyways: once cut, it's all 'automatic'!


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## SmithDoor (Sep 5, 2022)

wazrus said:


> Attache are pikkies of the homemade broaches. I do not have many 'bought' broaches, as they are so expensive, at least in Australia - where everything is expensive. I have one short commercial broach: any takers? And I do have all the gear for the commercial broaches and I do 'push' them in use. However, 'my' broaches have stood all the rigours of use in all sorts of material. The pix show some flame-cut, from 3/4"x6" mild steel wheels. The broach drive is from a 3T mandrel press and while this may sound a little underwhelming, it's simply a matter using thinner shims, if the going is a bit tough. For final sizing, I have a collection of thicker shims and when I'm near the depth required, I swap to the thicker bit and then finish off the lot with that shim. The broaches are quite simply sharpened in the same setup I used to cut the teeth. By the way, 'quarter' my loco drivers using the keyways: once cut, it's all 'automatic'!


I was lucky at time had the money and have 2 sets.  I also have arbor press for the broach and press bearing in. 

Even going to auctions they are costly.  

The other way is use a end mill and mill a slote in bore and use a round key. 

Most do not know if read some old books a complete machine shop can make gear key to shaft. So you a lathe , mill with dividing head and a broach or shaper. Did you most machine shops today can do that today. They send out for at less the broaching or cutting the gear.

Getting back how this a hobby shop setting. 
The best I came up with is use a gear motor and crank to quill of a mill maybe at most a 1" [25mm] stork. 
A short stoke needs less power. 

Dave


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## Vietti (Sep 5, 2022)

Perhaps I missed it, but I find broaching much easier if I drill a hole where the key way will be, use a sacrificial bushing to keep things straight.


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## wazrus (Sep 5, 2022)

I have to confess an omission, in that I had written about 'my' broaches in 2013! Nothing else has changed, though. i simply didn't look to page 1 of these posts.


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## mcostello (Sep 6, 2022)

Rotary broaches do not need clearance at the bottom of the hole. Was in a shop that rotary broached 1/2" holes about 1/2 " deep in 17-4 SS, no clearance hole allowed . Chips were a pain to break off.


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## William May (Sep 11, 2022)

timo_gross said:


> How do you push the broach? I am asking, because I made a diy broach and then came to the conclusion that it would require some sort of proper press to use it. Doing it with the drill press worked barely and it did not "feel right".
> I do not have any press in the workshop.
> 
> I rotated a workpiece a little bit at a time, then made a tiny slot at a time   . Not a single keyway just tiny slots.
> ...


I have a small Dake press that I use for my small broaches. It has a hand lever to operate it.  have a larger one for bigger broaches, and then a hydraulic press for the really large ones.  Once your broach and workpiece are set up, the forces really should not be that great. A broach typically takes off perhaps .005 (or less) with each tooth. So a lubricant, and gentle pressure and things go very sweetly. Just make sure to use a guide, even if you have to machine one special to the job.  This is not normally necessary, as broach kits usually have the guides included with them. Just make sure you use lubricant, make sure the broach is square and plumb to the hole, and go gently.  Your broach will soon plop gently onto the rags placed under the dake press, and you will have another fine hole.


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## wazrus (Sep 11, 2022)

I usually use a 3 ton mandrel press, which uses a simple, (about 1-1/2" square rack, and its mating gear is on the handle shaft. i have another 1 tonner for smaller stuff.  I often use a piece of pipe over the handle bar to increase leverage if needed. I've not counted, but i think my 'home' broaches have about 20 teeth, which are 'set' to cut .015" at a pass. i clear chips, which curl into the tooth gullets, with the MK1 human fingernail. Hard on the manicure, though. As Wlliam said, the broach drops through underneath for you to catch..


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