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Hacksaw Reamers for Injectors

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Another JohnS02/12/2021 14:15:49
832 forum posts
56 photos

May I ask what may be an obvious question to some?

In the "Injector Wars" in Model Engineer (19 November 2021), mention is made of using custom-ground cheap and cheerful hacksaw blades as reamers for injectors.

How are the reamers used? By hand? Powered and held, or done on the workbench? Blade in a tool-post?

I'm just wondering how one would use one accurately.

Thanks; John.

Speedy Builder502/12/2021 15:57:00
2590 forum posts
207 photos

John, when making the injectors, there are tapered holes in the cones. These are reamed with home made taper reamers. I can only assume that the author was grinding a piece of hacksaw blade to make a flat reamer however these reamers are very small and some cones are drilled with a number 80 drill 0.0135" dia being the small end of the reamer.

Edited By Mike Poole on 02/12/2021 16:26:16

noel shelley02/12/2021 16:23:00
1278 forum posts
21 photos

As above ! A variation on the D bit reamer I would assume ! Noel.

Nigel Graham 202/12/2021 19:17:37
2009 forum posts
27 photos

I was wondering the same.

Yes, these reamers could be considered a variation on the D-bit... but I too am puzzled by how to hold them concentrically, consistently and accurately without a purpose-made holder. They'd need lean over only very slightly to mis-shape the cone.

Regarding tempering tiny cone-reamers made from silver-steel, might a solder-bath work? It would need some experimenting and if effective, a thermostically-controlled dip-solder bath (electrical assembly tool) may be appropriate.

I have used that method with molten lead, to temper small leaf-springs for a loco., but lead is of "blue" rather than "straw" temperature. I know others have done similarly, successfully. The trick is to keep the metal just on crystallising point.

Another JohnS02/12/2021 19:36:50
832 forum posts
56 photos

Hi all;

A few years ago I started building about a dozen Derek Brown 12oz injectors, then but life took over, and the D-bit style reamers were only half made. The cones are the last thing to do before testing them, so I have to finish (or make a new design of) reamers.

Nigel; Bob Bramson wrote of an interesting way of holding the D-bit style reamers for milling the flat - in essence, one supports the reamer with soft solder in a half-circular groove, which after machining is then melted out, so I don't think the solder bath idea (although a great idea) would work. But, what do I really know!

I did make a Worden grinder, so I could grind HSS round blanks, I guess, but the idea of taking a cheap hacksaw blade and make a reamer out of it sounds like a nice little thing to do as an experiment. Also fits in with my Scots heritage.

Always learning; John.

Dave S02/12/2021 20:03:03
361 forum posts
90 photos
Posted by Nigel Graham 2 on 02/12/2021 19:17:37:

Regarding tempering tiny cone-reamers made from silver-steel, might a solder-bath work? It would need some experimenting and if effective, a thermostically-controlled dip-solder bath (electrical assembly tool) may be appropriate.

I have used that method with molten lead, to temper small leaf-springs for a loco., but lead is of "blue" rather than "straw" temperature. I know others have done similarly, successfully. The trick is to keep the metal just on crystallising point.

Deep fat fryer with ordinary cooking oil will do 200 degrees quite nicely, which is low end of tempering.

Dave

Speedy Builder502/12/2021 21:11:51
2590 forum posts
207 photos

I have made 5 of these reamers, different angles etc. Just harden the silver steel and let them down carefully with a gas torch. For one offs they seem fine, probably need to touch them up on a diamond stone every now and again if making multiples.

Bob

bernard towers02/12/2021 21:40:31
568 forum posts
109 photos

I made all the readers as per DAG Brown ,turned the taper hardened then ground in the t&c grinder and the tempered in domestic oven. They work a treat.

Simon Collier03/12/2021 08:59:41
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454 forum posts
63 photos

The hacksaw blade reamers in the ME article are held by hand.

Michael Gilligan03/12/2021 10:54:48
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20057 forum posts
1040 photos

For the education of this innocent … could someone please just let me know the approximate size and shape of these reamers

I am bewildered, because I thought that in “Model Engineering” circles they [injector reamers] would typically be very small

… Presumably there is another component part which needs reaming dont know

Sorry to be a dim-wit but it’s niggling me

MichaelG.

.

Edit: __ This is about the total of my present understanding:

https://youtu.be/s4MNHyoQr3Q

Edited By Michael Gilligan on 03/12/2021 11:10:24

Bazyle03/12/2021 11:13:42
avatar
6295 forum posts
222 photos

Back in the day every model engineer would have had a few broken hacksaw blades and kept them as a ready source of high carbon steel. (no bimetals in the shed then) They might soften the end of a piece and cut it at a fine angel with a chisel, filed close to shape, hardened and ground on an ordinary oilstone. It would be kept on the parent strip as a handle which probably still had some of it's teeth so a bit of rag protected the hand.
Typical size might be 1/8 at the thick end tapering to almost nothing over an inch, remember also that the target loco would most likely have been 3 1/2 in gauge so everything smaller than common today.

bernard towers03/12/2021 12:04:13
568 forum posts
109 photos

Michael, The readers are made from 5/32” dia silver steel/ hss depending on how you are equipped. The angles in DAG’s book are 6deg, 9deg and 13deg incl. with tip sizes typically 0.015”. I suppose micro grain carbide would be a fun thing to make them from!!!

Michael Gilligan03/12/2021 12:14:08
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20057 forum posts
1040 photos

@Bazyle … So is the “Injector Wars” article an historical discussion ?

@Bernard … Sorry, I don’t get the connection between 5/32” diameter and a hacksaw blade

blush MichaelG.

Speedy Builder503/12/2021 13:11:18
2590 forum posts
207 photos

For Michael's "education"

petes injector reamer dims.jpg

Michael Gilligan03/12/2021 13:27:12
avatar
20057 forum posts
1040 photos
Posted by Speedy Builder5 on 03/12/2021 13:11:18:

For Michael's "education"

.

That’s very useful for my general education … Thank You

But where on Earth does the hacksaw blade come into it ?

crying 2 MichaelG.

GordonH03/12/2021 15:01:10
47 forum posts
7 photos

Michael,

The hacksaw blade as such is simply the source of a thin flat piece of steel. which is shaped to to give the required cone angle in the finished part.. The cutting edge is along the corner between the top (or bottom) and side surfaces The illustrated reamer may be just a half cone angle which would be easier to produce.

This is a means of producing a reamer without needing to remove half the material from a machined cone to produce a cutting edge, and without hardening the resultant part, both of which can cause problems, From the text of the article, one was produced in about two minutes, so a considerable time saving compared to the traditional method.

Gordon

Michael Gilligan03/12/2021 16:00:57
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20057 forum posts
1040 photos
Posted by GordonH on 03/12/2021 15:01:10:

Michael,

The hacksaw blade as such is simply the source of a thin flat piece of steel. which is shaped to to give the required cone angle in the finished part.. The cutting edge is along the corner between the top (or bottom) and side surfaces The illustrated reamer may be just a half cone angle which would be easier to produce.

This a means of producing a reamer without needing to remove half the material from a machined cone to produce a cutting edge, and without hardening the resultant part, both of which can cause problems, From the text of the article, one was produced in about two minutes, so a considerable time saving compared to the traditional method.

Gordon

.

Thanks, Gordon

… it has taken me more than two minutes to visualise what you describe

[ perhaps I am just having a bad day ] blush

MichaelG.

Edited By Michael Gilligan on 03/12/2021 16:01:24

Another JohnS07/12/2021 22:27:26
832 forum posts
56 photos

Thanks all for the replies. I had to go away on urgent family business, and had *hours* of driving (20+ hours) to ponder this. (hey, it's 24 hours or more of straight driving to drive across the province of Ontario, I only had to go a bit of the way)

Also apologies if the "Hacksaw Reamers" reference did not make sense - I incorrectly assumed that people would be reading Model Engineer magazine, which of course is not correct - there's MEW, and of course rival publications. I should have spent more time thinking about my question.

Back home, and back to the workshop... John.

Edited By John Alexander Stewart on 07/12/2021 22:28:20

Michael Gilligan07/12/2021 22:51:32
avatar
20057 forum posts
1040 photos

Welcome back, John

… Sorry for dragging your thread away from its M.E. origins.

MichaelG.

Former Member04/01/2022 05:08:33

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