Gib material – Is brass best?

[Simon Williams 3Participant @simonwilliams3]

Bearing "brasses" are actually bronze.

I fancy it all depends on surface speed multiplied by loading, so for something very slow and lightly loaded ordinary brass will give a good service life. Up the speed and the load (i.e. main bearings in a traction engine) and ordinary brass isn't hard enough to resist the friction of the load it is supporting.

I don't know much about clocks, but it seems from the little I've seen that the bearing surfaces, if brass, which carry the load of the mainspring etc wear oval if left long enough, whereas up by the escapement the forces are very much less and the bearings' service life is much better.

Local surface finish and hardness of the supported surface is also going to have a bearing (sorry!) on the service life.

[not done it yetParticipant @notdoneityet]

Is brass best?

The answer to the original post is 'no' but it will work – probably just as well as some other alternatives. As soon as gibs allow any lateral movement, there will be a considerable force applied by the machine across the slideway. That may accelerate the wear on the gib/slideway. Think here white metal bearings for crank pins. Lead/tin white metal is suitable for petrol engines, but diesels require something a little harder – more tin, some antimony and, latterly, indium as well.

Perhaps the gib might wear rather than the slideways initially, I don't know, but likely a steel gib would give better/longer service life overall. Microscopes don't have any lateral loading, so not really comparable, I would think. As far as I know bearings were brass, unless bronze was substituted for a good reason. Slow moving, large area, well greased and easily/cheaply replaced. I know that bronze was used, in preference to brass, in disc coulters on ploughs, probably due to the side loading, but perhaps because of the harsher environment.

But get the right type of brass, as there are several and some are better than others for different applications.

[Chris TriceParticipant @christrice43267]

I've always used gauge plate for gib strips. Not the easiest material to work with but seems to do the job OK at least with cast iron.

[HopperParticipant @hopper]

If you look on various mini-lathe forums it seems brass gib strips is a common modification that apparently works for them. It's a low speed , low load application so material spec is not real critical. Not like on a motorbike main bearing etc.But a strip of bright mild steel might be easier and cheaper to obtain and will work just.fine, as on most lathes ever made.

[Danny M2ZParticipant @dannym2z]

Posted by Hopper on 29/10/2017 05:05:20:

If you look on various mini-lathe forums it seems brass gib strips is a common modification that apparently works for them. It's a low speed , low load application so material spec is not real critical. Not like on a motorbike main bearing etc

When the cast iron/ Chinese cracker carriage gibs cracked on my mini-lathe (as many others have found out it is weak spot waiting for a heavy hand) I made replacements from 6mm brass plate and after many years they are still working well with the odd tweak when chasing down a chattering problem during parting-off.

The chattering was mainly due to operator error and loose top-slide clearance. I checked this by putting a DTI on the bed and leaning hard on all the moving bits until the clock gave me something worthwhile to investigate.

Diamond lapping and carbide paper dressing the moving faces (gibs and bearing faces – the bearing faces were quite roughly finished, tailstock similar) improved things nicely and inserting 1.5mm ball bearings under replacement cup-pointed gib adjusting screws got things moving nicely.

I used bearing blue to check the progress but am not experienced at scraping so just used it as an indicator.

* Danny M *

[bugbear6502Participant @bugbear6502]

Having googled, I learnt that normal gib strips are quite big. The gib strips on the Simat are 2mm or less thick.

I've been rummaging in my scrap box for sheet steel I can cut some strips out of. I have some pressed steel parts from an ink jet printer that look promising.

I have read that the Simat top slide (held by a single hex bolt) is not very rigid, and best removed (if you can manage without it). I have evidence that "someone" took this seriously. In my "bits" pile I had a small slide, that I was going to use as a focusing/traverse for focus stacked macrophotography. On close reinspection it's the top slide from a Simat!

BugBear

Edited By bugbear6502 on 30/10/2017 13:02:29

[Chris TriceParticipant @christrice43267]

http://www.model-engineer.co.uk/forums/postings.asp?th=51850

[HopperParticipant @hopper]

Posted by bugbear6502 on 30/10/2017 12:58:38:

Having googled, I learnt that normal gib strips are quite big. The gib strips on the Simat are 2mm or less thick.

I've been rummaging in my scrap box for sheet steel I can cut some strips out of. I have some pressed steel parts from an ink jet printer that look promising.

A lot of sheet metal is very ductile steel, so that it can be pressed to shape easily. This means it would bend easily in use where the gib screws press. It might be worth purchasing a piece of gauge plate the thickness and width you need. It is a higher carbon steel, quite rigid, ground flat on both sides and ideal for gib strips. It is commonly available in circa 500mm lengths quite inexpensively.

[john carruthersParticipant @johncarruthers46255]

I fitted brass gibs to my little Meteor II instead of the plastic. I also pinned them and it seemed to me to feel better.
It's not a major operation, try several materials, see what works best?

[Neil WyattModerator @neilwyatt]

Just for comparison, the gib strips on a Super Adept, that paragon of British Quality Engineering, appear to be from unfinished 1/16 x 3/16" or 1/4" black steel…

[MWParticipant @mw27036]

Posted by Neil Wyatt on 07/11/2017 21:22:32:

appear to be from unfinished 1/16 x 3/16" or 1/4" black steel…

You mean it's just like, hacked off either end? sounds like a very british thing to do, id say.

[HOWARDTParticipant @howardt]

Posted by Michael-w on 07/11/2017 21:28:18:

Posted by Neil Wyatt on 07/11/2017 21:22:32:

appear to be from unfinished 1/16 x 3/16" or 1/4" black steel…

You mean it's just like, hacked off either end? sounds like a very british thing to do, id say.

Natural for a UK engineer to get hacked off, we were always the end of the line.

Seriously gib material should be softer than the mating material. Hardened ways can use cast iron gibs, cast iron ways can use soft steel gibs or in the case of small lathes even brass. Materials shouldn’t be able to be deformed under pressure as this negates any chance of constant pressure.

[Chris TriceParticipant @christrice43267]

If that were true, why have all my Myfords (an ML4, two Super 7's and a Speed 10) had hardened steel gib strips along with my Emco Compact 5, Zyto and Cowells ME lathe? They're all hardened steel running against cast iron.

 

Edited By Chris Trice on 08/11/2017 00:03:02

[Chris TriceParticipant @christrice43267]

….. except the Compact 5 which is hardened steel running against Mazak.

[not done it yetParticipant @notdoneityet]

If the OP had set his question as simply 'which material is best? ' rather than 'is brass best? he would have received better replies.

A bit like 'is carbide best?' for cutting tools rather than an enquiry as to which material is best. Often 'horses for courses', so no best for all situations.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by not done it yet on 08/11/2017 08:26:04:

If the OP had set his question as simply 'which material is best? ' rather than 'is brass best? he would have received better replies.

A bit like 'is carbide best?' for cutting tools rather than an enquiry as to which material is best. Often 'horses for courses', so no best for all situations.

.

The opening post seemed very reasonable to me … and has elicited some good replies.

MichaelG.

[bugbear6502Participant @bugbear6502]

Posted by not done it yet on 08/11/2017 08:26:04:

If the OP had set his question as simply 'which material is best? ' rather than 'is brass best? he would have received better replies.

A bit like 'is carbide best?' for cutting tools rather than an enquiry as to which material is best. Often 'horses for courses', so no best for all situations.

If I knew enough to ask the perfect question, I probably wouldn't need to ask any question at all!

BugBear

[egaParticipant @ega]

Posted by Chris Trice on 08/11/2017 00:00:15:

If that were true, why have all my Myfords (an ML4, two Super 7's and a Speed 10) had hardened steel gib strips along with my Emco Compact 5, Zyto and Cowells ME lathe? They're all hardened steel running against cast iron.

Edited By Chris Trice on 08/11/2017 00:03:02

The top slide, cross slide and saddle gibs on my old Super 7 are certainly not hardened steel, top slide and saddle having been dowelled and cross slide fitted with locks by me all of which involved drilling the gibs with ordinary tools.

[Neil WyattModerator @neilwyatt]

Posted by Michael-w on 07/11/2017 21:28:18:

Posted by Neil Wyatt on 07/11/2017 21:22:32:

appear to be from unfinished 1/16 x 3/16" or 1/4" black steel…

You mean it's just like, hacked off either end? sounds like a very british thing to do, id say.

Hacked off at either end?

There's no way a British lathe manufacturer would do that.

It's clearly pinched off, it looks like they used side cutters, much neater…

[Martin KyteParticipant @martinkyte99762]

In clocks brass wheels tend to wear hardened steel pinions (OK after some time). The reason being that dust gets embedded in the soft brass of the wheel and creates an abrasive lap which harms the pinion.

I could imagine a similar situation occuring with brass gibs. Ideally in any mechanism when you can you want to arrange for the cheapest or most easily replaced componant to wear in preference to the parts you wish to preserve.

In this argument a harder material compliant with ease of manufacture, friction characteristics, cost and utility would be better.

regards Martin

[Chris TriceParticipant @christrice43267]

I've got a brand new (Nottingham) Myford cross slide gib here and ega is right that it's not hardened so I stand corrected. You can file it. It's clearly ground though and definitely a steel. However the Emco one is definitely hardened. The file won't touch it.

[MWParticipant @mw27036]

Posted by bugbear6502 on 08/11/2017 08:59:17:

Posted by not done it yet on 08/11/2017 08:26:04:

If the OP had set his question as simply 'which material is best? ' rather than 'is brass best? he would have received better replies.

A bit like 'is carbide best?' for cutting tools rather than an enquiry as to which material is best. Often 'horses for courses', so no best for all situations.

If I knew enough to ask the perfect question, I probably wouldn't need to ask any question at all!

BugBear

The forum lives or dies on the ability to discuss and ask questions so I would go ahead anyway. Otherwise we might as well all just hang up our hats and call it a day.

Michael W

[egaParticipant @ega]

Chris Trice:

Thanks; it's good to know that my 1960s machine is still up-to-date in that respect.

I think your suggestion of gauge plate is just about ideal for anyone wanting to make a gib.

Edited By ega on 08/11/2017 14:34:53

[Chris TriceParticipant @christrice43267]

The reason I looked at this subject again is because I've just made another piece of equipment using a slide requiring a gib strip. I've always used gauge plate in the past on recommendation from a fellow model engineer I respect greatly and I just bought another strip from the local Cromwell Tools nearby. Without testing, and I accept it proves nothing but visually, I'm damned if I can tell the difference between the Myford gib I have and the gauge plate strip. The only difference (obviously) is the Myford has an angle machined on one edge and a few dimples drilled for the adjusting screws. The file marks both the same and they both "feel" identical. Short of carrying out a machining task on both to compare the machinability, I'm content with the gauge plate which is now finished and smoothly guiding my new slide.

[MWParticipant @mw27036]

Posted by Neil Wyatt on 08/11/2017 10:02:05:

Posted by Michael-w on 07/11/2017 21:28:18:

Posted by Neil Wyatt on 07/11/2017 21:22:32:

appear to be from unfinished 1/16 x 3/16" or 1/4" black steel…

You mean it's just like, hacked off either end? sounds like a very british thing to do, id say.

Hacked off at either end?

There's no way a British lathe manufacturer would do that.

It's clearly pinched off, it looks like they used side cutters, much neater…

It's okay i'm just messing with yers.

[Author]

Posts