Bevel Gear Replacement for Astra L2/L4 Mill – any ideas?

Advert

New Replies

Report Bug

Help/FAQs

Bevel Gear Replacement for Astra L2/L4 Mill – any ideas?

This topic has 18 replies, 12 voices, and was last updated 24 March 2022 at 14:22 by Andrew Tinsley.

Viewing 19 posts - 1 through 19 (of 19 total)

Author

Posts
22 March 2022 at 08:56 #591047
B Tulley
Participant
@btulley
A friend has an Astra L2/L4 Milling Machine; the nylon(?) bevel gear in the head (which mates with a metal gear) is very worn – when the gear fails completely the machine will become a large lump of scrap.
Searches for a spare have failed – the Manufacturer in Italy still exists but they no longer supply spares for this model. So does anyone have any ideas please? Approximate dimensions are as follows: Overall Diameter 51mm, Plain Boss Diameter 35mm, Shaft Bore Diameter 15.3mm, Length 33mm, 25 Tooth (I think it's a spiral bevel gear – can anyone confirm?)
I'm told that removal of the mating gear would be very difficult, so replacement as a pair isn't really an option. Any ideas please – 3d printing etc. are waaay over our heads and he's naturally very protective of the existing gear and would be very uneasy about sending it away for copying, matching etc. So any supplier would need to be within reasonable travelling distance of M25 J25. Unless of course someone happens to have a decent spare in their shed, or know of a supplier….
Many thanks, Brian

Edited By BRIAN TULLEY 1 on 22/03/2022 09:07:50
Advert

22 March 2022 at 08:56 #20658
B Tulley
Participant
@btulley
22 March 2022 at 09:21 #591050
Brian Wood
Participant
@brianwood45127
Hello Brian,

I think your best bet, unless someone here is willing and capable of stepping in, is to contact HPC Gears in Chesterfield to arrange to have it copied in metal while there is still enough of it left for measurement and identification..

It won't be cheap but they do a nice job. Phone 01246 268080

Regards Brian
22 March 2022 at 09:47 #591052
John Haine
Participant
@johnhaine32865
Is this for power transmission or vertical feed? Does it mate with another nylon gear or a metal one?
22 March 2022 at 10:32 #591060
Brian Wood
Participant
@brianwood45127
Metal gear John, the information is in the original post. #

That is why I suggested a metal replacement. Looking at the lathes.co website at the Astra models, the only place I think a bevel gear might be used is for the knee operating leadscrew—in which case I seriously question the combination of the gear pair chosen

Regards Brian

Edited By Brian Wood on 22/03/2022 10:40:37
22 March 2022 at 10:51 #591067
Oldiron
Participant
@oldiron
You could try Bevel Gears

Link is for Apple Rochester Gears Ltd Wellingborough Northants. Less than 2 hrs from M25 J25. I have used them many times in the past. Always found them very helpful.

regards
22 March 2022 at 11:02 #591071
DutchDan
Participant
@dutchdan
You could possibly try contacting the manufacturer. They may have a spare stashed away in storage somewhere, or if not, be able to supply you with spec/drawings of the gear to get a new one manufactured.
22 March 2022 at 11:05 #591072
Anonymous
It's not really a spiral bevel gear, but the teeth do look slightly skew. That seems an odd choice, and makes manufacture more difficult. If possible a picture of the mating gear would be helpful as, presumably, it is less worn.

Andrew
22 March 2022 at 11:22 #591077
B Tulley
Participant
@btulley
Thanks for the replies; the manufacturer has been very unhelpful – I did ask about a drawing etc. but got nowhere.

I've not seen the exact position of the gear but am pretty sure it's in the head drive from motor to cutter; the mating gear is metal. I'll be seeing the owner in a couple of hours and will ask him more.

Kind Regards,

Brian
22 March 2022 at 11:23 #591078
Jeff Dayman
Participant
@jeffdayman43397
Finding replacement miter gears (for shafts at 90 degrees to each other) is not difficult, several industrial suppliers in North America have a huge variety of them, likely some in UK do as well. But skew (angled tooth) miter gears are much harder to find, especially in plastic.

Food for thought – replace BOTH gears with an available set of metal non skew / straight tooth miter gears to keep your machine running.
22 March 2022 at 12:02 #591087
John P
Participant
@johnp77052
Found this photo of the head drive gear on an Astra L2.
Is this the same setup as you have , is the nylon gear
fitted on the shaft of the vertical milling head.

Some other photo's of this machine here
https://www.stationroadsteam.com/astra-milling-machine-stock-code-2977/

John
22 March 2022 at 12:02 #591088
B Tulley
Participant
@btulley
Do you know if this is a spiral bevel gear? Or a skew gear? Or something else?
22 March 2022 at 12:14 #591089
Anonymous
The picture posted by JohnP is definitely a spiral bevel gear, as the teeth are curved. The gear set probably is driving the spindle, you wouldn't bother with spiral bevel gears just to move an axis. I agree with a previous post that nylon seems an odd material to choose.

Andrew
22 March 2022 at 13:01 #591098
Clive Foster
Participant
@clivefoster55965
Spiral bevel would be the preferable engineering choice for driving a vertical milling spindle from a horizontal shaft as the amount of gear engagement is pretty much constant throughout a revolution. So the load is carried smoothly reducing the chances of marks on the machined surface due to cutter oscillation.

I have seen a similarly seriously chewed up nylon bevel gear that was said to have been forced into contact with a metal gear of different form. No idea what the mating gear was, just shown the chewed up gear as an example of things wot people do accompanied by a plaintive "and it actually worked".

If an ordinary nylon mitre gear had been forced against a metal spiral bevel I'd expect a similar wear pattern with only the outer tips retaining enough engagement to drive whilst the spiral chewed out the rest of the nylon tooth form until clearance was generated. Starting off with the head a bit loose and slowly tightening down as it ran it would work if the perpetuator were sufficiently mechanically unsympathetic.

In a perfect world a pair of matching spiral bevels from one source would be best.

Clive

Clive
22 March 2022 at 13:18 #591104
HOWARDT
Participant
@howardt
I agree with Clive a matching pair would be the way to go. It looks like a straight bevel to me, any pair you buy you may have to machine some washers to achieve the correct mating of the gears. We assume the gear shafts are at 90 degrees and inline.
23 March 2022 at 13:23 #591259
David George 1
Participant
@davidgeorge1
In repairing a large milling machine with a universal head HPC made a new pair for the mill.

David
23 March 2022 at 14:30 #591264
John P
Participant
@johnp77052
If your friend has all the parts for this still to be a working
horizontal mill and a dividing head ,all you need is a copy of
Ivan Law's book Gears and gear cutting and make a set of
parallel depth bevels as replacements.
These gears here replaced a steel and nylon gear set that
had gone the same way as your set .In this sander the pinion
runs a 18000 rpm.
Providing that you harden them they will last a lifetime
John
24 March 2022 at 10:37 #591381
B Tulley
Participant
@btulley
Hi all,

Firstly, many thanks for all the very helpful replies

Having received numerous recommendations for HPC Gears both on here and also elsewhere I'll suggest to the owner that would be his first starting point – ideally replacing both gears as a matched pair. I'll be seeing him tonight (Model Engineering Evening Class/Group) and it looks like the first job will be to investigate how easy (or not) removal of the other gear will be……

Kind Regards,

Brian
24 March 2022 at 14:22 #591424
Andrew Tinsley
Participant
@andrewtinsley63637
I did a similar repair using a matched pair of gears from a large, ancient , burnt out angle grinder. The gear ratio wasn't quite the same as the original, but who cares. It cost nothing.

Andrew.
Author

Posts