Author Topic: Help needed with Bantam 800 Feedscrews/Nuts please.  (Read 4936 times)

Offline rotorhead

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Help needed with Bantam 800 Feedscrews/Nuts please.
« on: November 19, 2012, 03:12:49 PM »
Hi folks,

I'm after a bit of help / info regarding the cross slide screw/nut and topslide screw/nut, for my son's Bantam 800.

He's stripped the screws and nuts off, and brought them round for me to make the bits up for him, but, the cross slide screw is an odd ball.

It measures up as 9/16" diam x 10 tpi double start LH, but 2/3rds of it is  worn more than the rest, I'm wondering about making a new screw.

My thought is to make it 5/8" diam x 10 tpi single start LH, so as to utilize a ready made acme tap, I'm unsure what difference it would make to the dial readout.

The topslide screw as far as I can tell is unworn, it's just the nut, which can easily be made using a tap, that's on order.

Chris
Sunny Scunny,
North Lincolnshire.

Offline doubleboost

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Re: Help needed with Bantam 800 Feedscrews/Nuts please.
« Reply #1 on: November 19, 2012, 03:19:32 PM »
If they are both 10tpi
(the double start could be 5 tpi) :bugeye: :bugeye:
It should makle no differance to the dial
I had a bantam 800 i am sure mine was only a single start thread
I have just finished a 8tpi single start
I would not fancy a double  :Doh: :Doh: :Doh: :Doh:
John

Offline rotorhead

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Re: Help needed with Bantam 800 Feedscrews/Nuts please.
« Reply #2 on: November 20, 2012, 03:51:54 AM »
Hi John,

I was thinking that it would amount to an effective 5 tpi, just using a standard thread gauge, it came up with 10 tpi, then there's the splines etc on tother end.

So I would really need to do it 5tpi, then get a 5/8" x 5 tpi LH acme tap, far easier than grinding the correct form, then screwcutting in the lathe, for me anyway..

If I have to end up screwcutting, I've come across a suggestion, that might make things a little simpler regarding the wear on the screw, recut the existing screw to match the worn section.

What I'm saying is, grind a tip to the worn area form shape, then cut the unworn section, which I hope would then end up all the same along the screw.

Doing this would I hope, effectively strengthen the phosbronze nut, due to the wider thread section required in the nut, to compensate for the widening of the gaps in the thread form of the screw..

Any suggestions or pointers to flaws in my thinking would be appreciated.

Chris
Sunny Scunny,
North Lincolnshire.

Offline doubleboost

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Re: Help needed with Bantam 800 Feedscrews/Nuts please.
« Reply #3 on: November 20, 2012, 12:48:09 PM »
If it was mine  i would make a new one 10 tpi single start
This would make the x feed finer giving a direct reading (wind in .010 would make it travell 0.005
Effectivley taking 0.010 off the job :bugeye: :bugeye: :bugeye: :bugeye:
John

Offline rotorhead

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Re: Help needed with Bantam 800 Feedscrews/Nuts please.
« Reply #4 on: November 21, 2012, 04:51:08 PM »
Thanks John,

I'm beginning to come to that way of thinking myself, as a 5/8" x 10 tpi acme tap would be far more readily available (just bought one £15.67 from RDG), 5 tpi would take some forcing through.

If I remember to take pics I'll post em.

Chris
Chris
Sunny Scunny,
North Lincolnshire.

Offline doubleboost

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Re: Help needed with Bantam 800 Feedscrews/Nuts please.
« Reply #5 on: November 21, 2012, 04:59:58 PM »
Hi
Chris
My Bantam was metric
I always found the cross slide feed a bit on the coarse side
Is there no screws and nuts available for it commercially
John

Offline rotorhead

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Re: Help needed with Bantam 800 Feedscrews/Nuts please.
« Reply #6 on: November 21, 2012, 05:25:55 PM »
Hi John,

I'm sure I'll have to make the nut, we've seen a metric one on eBay for £150, stuff that.

Also using 5/8" dia bar will give the correct dia for the spline head, I'll post this original screw pic to see if it's the same.

I'm sure this lathe is Imperial as it has dual dials and there's no metric thread pitched feedscrews.

Chris
Chris
Sunny Scunny,
North Lincolnshire.