Author Topic: A " Broach " too far, gone?  (Read 482 times)

Offline Alyn Foundry

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A " Broach " too far, gone?
« on: May 12, 2020, 12:17:47 PM »
During my early years as a supplier I had also offered part machining services. Flywheels in particular.
The keyway broach became a familiar tool in the arsenal.

Back in the day the DuMont system was purchased and special bushes made for the " extra " depth requirements of my products. These tools were, and still are expensive but the price paid was worth every penny as they are still in use 30+ years on!

Several years ago I broke my 1/8" A series broach, shattered into several pieces. A cheaper one was found and did many keyways before just recently my two youngest started making models, yes, we lost it.

These days we have much more Far Eastern, cheap tooling available so a replacement was ordered and duly arrived. It didn't last two minutes. Despite much care it snapped in half like a carrot.

The reason for posting? A cunning plan?

The photo shows my, I hope, solution to the problem. I have glued the two halves into an unusable piece of Silver Steel so that the broach is fully supported along its length. The older broach, which also snapped in half will be glued into a guide to provide the second finishing pass.

I must stress that I haven't tried the " new " approach yet but thought I'd share the idea anyway, perhaps this has already been done before?

Over to you....

Cheers Graham.

Offline Vixen

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Re: A " Broach " too far, gone?
« Reply #1 on: May 12, 2020, 12:33:44 PM »
Hello Graham,

A very cunning plan. Looks like it should work. The SS support should act in place of the guide bush. Do you need to apply lots of lube grease?

Mike
It is the journey that matters, not the destination

Offline john mills

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Re: A " Broach " too far, gone?
« Reply #2 on: May 12, 2020, 01:24:31 PM »
when i was programming cnc machines there were several broaches set up like that some had 2 180 deg apart
hopefully yours in more than one piece should still stay together.i think the ones i used were a tight fit in the
key way in the mandrel.  John

Offline Alyn Foundry

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Re: A " Broach " too far, gone?
« Reply #3 on: May 12, 2020, 02:10:16 PM »
Thanks guys.

So it would seem its been done before, we stand a good chance then!

Mike.

We have always used a little light oil on the broach to bush mating surface but never for the cutting face. Being mainly used on cast Iron with its own self lubrication properties does help.

There's a big " however " here.... Will the long bushing " pickup " in the bore?  Most of the bushes are several Thou smaller in diameter, I've used 1/2" Ground stock/drill rod that's " bang on "  1/2" your suggestion of added lube might have some merit, we shall see.

Cheers Graham.

Online Jasonb

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Re: A " Broach " too far, gone?
« Reply #4 on: May 12, 2020, 03:48:56 PM »
What I want to know is will you be ungluing it and then sticking it back together with a shim for the second pass :LittleDevil:

Offline Alyn Foundry

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Re: A " Broach " too far, gone?
« Reply #5 on: May 12, 2020, 03:59:35 PM »
What I want to know is will you be ungluing it and then sticking it back together with a shim for the second pass :LittleDevil:

 :lolb:

No Jason, my youngest managed to snap the previous one in half last month. If the first " push " modification works OK I'll be doing the same with the older one with the reduced depth of groove matching the shim.  ;)

Cheers Graham.

Online Jasonb

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Re: A " Broach " too far, gone?
« Reply #6 on: May 12, 2020, 04:59:45 PM »
A cunning plan

Must say the import ones that I bought have served me well and also a couple of people I have lent them to.

Offline Alyn Foundry

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Re: A " Broach " too far, gone?
« Reply #7 on: May 12, 2020, 05:29:50 PM »
A cunning plan

Must say the import ones that I bought have served me well and also a couple of people I have lent them to.

Well.... I first put it down to lack of experience particularly with the older broach but I broke the new one.

The older DuMont broaches don't even flex during the push. Sign of the times, perhaps?

Cheers Graham.

Offline kvom

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Re: A " Broach " too far, gone?
« Reply #8 on: May 12, 2020, 10:09:55 PM »
I looked on eBay; there's a 1/8A on offer for $30.  If price in the UK is similar I'd just buy a real dumont.

Offline Alyn Foundry

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Re: A " Broach " too far, gone?
« Reply #9 on: May 13, 2020, 12:30:56 PM »
I looked on eBay; there's a 1/8A on offer for $30.  If price in the UK is similar I'd just buy a real dumont.

Hi kvom.

Could you provide a link please?

Cheers Graham.

Offline kvom

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Re: A " Broach " too far, gone?
« Reply #10 on: May 13, 2020, 01:23:50 PM »
I looked on eBay; there's a 1/8A on offer for $30.  If price in the UK is similar I'd just buy a real dumont.

Hi kvom.

Could you provide a link please?

Cheers Graham.

https://www.ebay.com/itm/DUMONT-1-8-A-H-S-BROACH-LOC-F18-3/383536337054?hash=item594c8c109e:g:s5oAAOSwhkNetCMO

Online Jasonb

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Re: A " Broach " too far, gone?
« Reply #11 on: May 13, 2020, 01:40:42 PM »
Double the price by the time shipping is added ( 22GBP) and then you may also get stung for VAT (20%) import duty and feeys

List price fot 1/8" type A over here is 81.60GBP. but you could probably get 50% off that.

Offline Alyn Foundry

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Re: A " Broach " too far, gone?
« Reply #12 on: May 13, 2020, 02:29:09 PM »
Thanks to you both.  :ThumbsUp:

I did notice it was secondhand, not that I'm averse to the fact! Most of my workshop tooling was secondhand but I personally checked them before buying, that's the difference.

I think I'll stick to plan " A " for the time being as their use is very infrequent these days.
Just thought it might be worth sharing the idea.

Cheers Graham.

Offline Brian Rupnow

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Re: A " Broach " too far, gone?
« Reply #13 on: May 13, 2020, 06:21:17 PM »
A few years ago I bought a small broach kit, which contained a 3/32" a 1/8", and a 5/32" broach, along with an assortment of bushings in the size range I use, fro 1/4" up to 1/2". The kit cost about $500. It worked very well, but through time, and mostly due to inexperience and hamb handedness, I broke two of the broaches. The people who I bought the kit from said they did not have extra broaches to sell as individual pieces. My son was employed by Fastenal two years ago, and he was able to get me replacement broaches at $100 a pop. Now when I use them, I take a great deal more care of how I go about using them.