Vice as Broaching Press

[James Hall 3Participant @jameshall3]

Hello everyone.

I’ve got it in mind to have a go at building a Farm Boy and have bought the plans to mull over.

Thanks to the loss of my winter heating allowance my funds available for modelling have been severely curtailed so before deciding whether to proceed I’m trying to get together some notion of the eventual cost both in materials and tooling for the job.

The plans show a 1/8″ broached keyway in the cast iron flywheels – broaching will be a new technique for me. I don’t have a press, and balk at the expense of buying one. I do, however have a hefty Record 112 vice which does me for all pressing jobs so far and which could, I think, be bodged up with some jaws to act as mandrel(?) and anvil(?) of a press. I have no real notion of how much pressure this vice can exert but suspect that, being screw-driven, it must be at least as much as a small rack-actuated press. Has anyone used a vice in this way, or are there any thought/advice on the viability of doing things this way.

I have, incidentally been playing with calculations for the crank/camshaft gearing and (if my figuring is correct) find that 27/54 Mod 0.7 would serve the purpose being very near to the specified shaft centre distance and gear ODs. I think that this would look better to scale than the 36/72 48DP specified or the 38/76 Mod 0.5 sometimes used.

[JasonBModerator @jasonb]

What lathe have you got? Using the carriage to plane the slot is another option and saves buying a broach.

[James Hall 3Participant @jameshall3]

Ah, JasonB – what a helpful stalwart you are.

I have a Sieg SC4. I have heard of this method, but know little of it. Presumably a correctly shaped cutter is mounted in the tailstock and repeatedly advanced through the bore – the workpiece being held in the chuck and the spindle locked in some way. There would be the cost of the cutter (are such available, or would it be a home-ground job). I see that ARC do a 3mm broach for £10.

[Paul LousickParticipant @paullousick59116]

A vice will work to broach a 1/8″ slot. Ensure that the broach is perpendicular to the hole or it could bend and break. Before I had a proper press, I use a light weight drill press to broach a 1/8″ slot in steel. The pinion gear on the press was only pinned to the shaft with a small roll pin which sheared. Replaced the roll pin with a nail and cut the slot.

[Andrew CrowParticipant @andrewcrow91475]

James, the tool would normally be HSS ground to size and held in a boring bar in the tool post,  then  fed using the carriage hand wheel depth of cut applied on the cross slide.

The usual way of locking the spindle is to put the machine into a low gear and hang a weight on the chuck. This method was discussed in another recent thread.

This is a good way of producing  keyways although a bit slow and tiring on the arm.

Andy

[Nigel Graham 2Participant @nigelgraham2]

I have not used broaches but am I right saying a broach is used with a support bush to stop it springing away from the cut and possibly breaking?

The bush is flanged to retain it, and the broach slides in a keyway-like slot cut along its exterior.

Shaping the keyway as Andrew describes is a common method when faced with only a few of them. It is rather cruel to to the lathe so not to become a habit, and you can only take very light cuts, but it does work. Note that with a relatively long keyway (hence boring bar) you will probably need take spring-cuts as the bar will tend to deflect, giving a tapered depth.

[Nicholas FarrParticipant @nicholasfarr14254]

Hi, yes you will need a guide bush with a broach, and probably a shim or two, to get the depth of the keyway that you need. Yes they can break.

Don’t know how you would use one in a vice, as you need a space on the other side for the broach to pass through.

You can also cut a keyway using a shaping machine, with a boring bar type tool.

Regards Nick.

[James Hall 3Participant @jameshall3]

Nicholas Farr – the 112 is extremely hefty with substantial and substantially fixed removeable jaws. I envisage a set of fabricated jaws extending enough far enough above the fixed jaw structure to allow a drilling for the broach to pass through (i.e., ressembling the anvil of an arbour press). The distance above the fixed structure of the drilling would only need to be a few millimeters so I don’t think that flexing would be any problem at all.

The design and fabrication of collars for keyway broaching of this sort is fairly trivial I think.

[Nicholas FarrParticipant @nicholasfarr14254]

Hi James, I know what a 112 vice is, as I’ve used them in my day jobs, the downside is they have side slope, just like most vices of this type, and this could quite easily distort and break your broach, so you would have to have something to stop it and keep the jaws parallel, as you don’t want to put any angular forces on your broach.

Regards Nick.

[Speedy Builder5Participant @speedybuilder5]

Never really thought too much about it, but you may be able to use a Carpenters “sash cramp”  – No forget that, you said FLYWHEEL, which would prevent its use and I suspect your 112 vice also, as the depth of the vice would not be sufficient to accommodate the flywheel ?

I would go with Jasons idea – I have done that with the tool mounted like a boring bar on the carriage several times

This gives me another idea – How about using the ELS and instead of getting the pulse from the rotating headstock spindle, supply the pulses from an electronic gismo to move the carriage back and forth.

Bob

[DC31kParticipant @dc31k]

Rotate the photo of Nicholas Farr 90 degrees clockwise. The part on the left of the photo would then look like a slotted faceplate on a lathe. The part on the right would look like the barrel of a tailstock.

Or stand the lathe upright on its change wheel cover…

A tiny 1/8″ keyway is going to tax the tailstock far less than pushing a 5/8″ twist drill through something.

On the ELS idea, a standard rotary encoder would supply the pulses – think of the manual jog wheel used on a CNC mill (sometimes on a pendant). That has axis-selection switches and a multiplier (one click of the encoder wheel is 0.01mm, 0.1mm, 1mm, 10mm).

[JasonBModerator @jasonb]

Very little cost in making a tool, a bit of steel bar that just fits the bore and a broken ctr drill is all that is needed.

Flexing of the tool can be taken advantage of to give a good seating for a tapered gib head key.

bear in mind that the length of a flywheel hub is more than say a thin gear so you will have maybe six teeth engaged in the cut at any one time so that needs more force than the 1 or 2 that are engaged in a thinner workpiece.

One I did earlier four of 1″ long x 3/16″ wide in steel and I think the single was 5/32″ wide

For shorter keyways I have ecen just use da bit of 3mm sq HSS

[Nicholas FarrParticipant @nicholasfarr14254]

Hi, the first keyway I cut was on a Swift Sentinel lathe, using a boring bar, but was done on the opposite side to JasonB’s in the photo above, this was in the early 70’s before the company bought both a metric and imperial set of their commonly used sizes.

Regards Nick.

[Clive FosterParticipant @clivefoster55965]

I always plug the centre hole and run a drill a bit smaller diameter then keyway size through where its is going. Drill running half in the plug half in the part getting the keyway.

Shifts most of the material so the key cutting bit or broach has less work to do. Few strokes of a file to clear a bit more out of the corners too.

Makes big difference to the effort needed, especially if planing on the lathe, which is good thing when using improvised methods. If planing on the lathe with a boring bar arrange some sort of support for the bar immediately in front of the work to combat deflection. Adjustment can be a right pain but it seriously reduces the chance of deflection as the cutter enters the work.

The art with this sort of planing job seems to be to get a good clean entry with the cutter working nicely. If you get the angles right there seems to be an element of self stabilisation under cutting loads helping against deflection. My experience is that with a relatively long keyway, where deflection is most likely to be an issue, if the first half or so goes true the back seems to follow just fine. If you have issues close to the front the job turns into a right battle with lots of scraping cuts to get the taper out.

I’m certain there is an art to getting planing speed and cut depth balanced.

As ever for me third time was the charm! First couple of efforts were, ahem, “seriously disappointing after all the hard work and verbal encouragement”.  Penny dropped on third go. Later I bought a broach set which is much easier. I do think the planing experience helped with the broaches tho.

Set something up and practice. It really isn’t that difficult but you do have to dial in the feel for the job.

Clive

[Ian HewsonParticipant @ianhewson99641]

I have tried both methods to produce the flywheel keyways, and having done so I bought a press and broach. I would not go back to planeing on the lathe, too much effort and poor results.

Ian

[noel shelleyParticipant @noelshelley55608]

VERY careful use of a hacksaw blade and a file will do this job ? I know it was an agricultural machine but I have cut keyways this way, may be not pretty but it worked. Noel.

[DalboyParticipant @dalboy]

Having broached the flywheels on my Farm boy I certainly would not try a vice as already mentioned because of the play in them, it may not seem a lot, but I know from experience doing other jobs the amount of side to side movement of the vice jaws and the small nature of the broach it could end in tears.

Even a press needs a careful approach push a little ease off the press and repeat until finished.

 

[duncan webster 1Participant @duncanwebster1]

I think it would be kinder to the lathe to fix the single point tool in the tool post, but push the saddle along with the tailstock, then the forces are almost in line.

My mate had a slotter, which is a bit like a shaper but arranged vertically. I bet nog many amateurs have one of those.

[duncan webster 1]

On duncan webster 1 Said:

My mate had a slotter, which is a bit like a shaper but arranged vertically. I bet nog many amateurs have one of those.

I have, as an accessory for my Sharp milling machine

 

but when I made my Farm Boy I used a 3mm broach

 

but had to make a suitable guide to fit the imperial bore of the wheel

Rod

[Nicholas FarrParticipant @nicholasfarr14254]

Hi Rod, I had to make the guide in my photo above as I only had the broach, easy enough to do.

Regards Nick.

[Norman BillinghamParticipant @normanbillingham91454]

When I had to do this on a model with a 2mm square keyway, I made a cutter and used the ‘lathe as shaper’ method, which worked well enough but was quite a lot of work.

When I replaced the motor on a small woodturning lathe and needed a pulley with a 6mm keyway, I used a different approach (for which I claim no credit as I’m sure I read about it somewhere). I machined a sleeve with a bore to fit the motor shaft and a wall thinness of 3mm, then mounted it in the mill and machined a 6mm wide slot through the wall and along the length.  I bored out the pulley to take the sleeve and located it with JB Weld after a thorough clean.  The job has happily transmitted power from an 0.25 HP motor for several years of fairly regular use with no sign of problems.  On a small model the stresses are pretty minimal – but I guess you could also cross pin if you wanted ‘belt and braces’.

[Howard LewisParticipant @howardlewis46836]

I made a Slotting Tool, from a casting and drawings, supplied by College Engineering Supply, when Howard Profitt ran the firm. The design was that of the late Peter Robinson, to fit a Myford 7

When i changed to a larger lathe, I made a raising block for it.

It has only cut a few keyways, both internal and external, and even an adaptor for a speedometer drive, which required a square hole!, but a very useful tool when needed.

Howard.

[Andrew CrowParticipant @andrewcrow91475]

There is still a kit available at Hemingway’s, though now under the Reeves banner.

Andy.

[Clive FosterParticipant @clivefoster55965]

Effective keyway slotting devices can be fabricated quite easily if a casting kit is too much work to fit in mid job.

Being, at times, a crude fellow I like the design by Norman Valentine shown at the bottom of this thread :-

https://www.model-engineer.co.uk/forums/topic/keyway-cutter-for-myford/

Almost brutally simple, so easily reworked to suit materials you have to hand, it embodies all the necessities of a successful design. In particular the configuration gives minimal extension, and therefore maximum rigidity, of the cutter ram at the beginning of the cut ensuring a clean start to the keyway. It would seem relatively easy to adapt the design to directly carry smaller bars for smaller keyways. To my mind the Hemingway design puts the cutting tool rather too far forward of the support structure unnecessarily reducing stiffness when doing small keyways in small bores.

The great thing about such lever operated slotting tools is the inherently light, direct, action enabling you to feel what the tool is doing. Successful keyway cutting, especially by simple planing methods, demands that the tool cuts easily at a near constant appropriate speed and is not forced. The indirect action of the late saddle and hand wheel method makes it harder to feel whats going on.

With 20/20 hindsight I’m somewhat ambivalent about my decision not to bother making such a tool “mumble-mumble” years ago when I first needed to make a keyway. Planing with the saddle and, later, broaches have done well enough for me over the years but I suspect a proper tool would have made the work easier and saved me the money spent on a broaching set. But that Marlco branded set was stupid cheap!

Clive

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