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Advice on an Internal Acme Thread

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ddickey

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#1
Thread is RH 5/8-10 .750" long bore.
Micro 100 boring bar is a hundred bucks. Any idea what a shop would charge to do this? thumbnail_IMG_20170822_175240056.jpg thumbnail_IMG_20170823_034748380.jpg
This is for my surface grinder. It is the vertical feed screw.
 

Uglydog

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#2
Is that the new bevel gear?
You just need it tapped to 5/8 x10 RH acme?
Or are you looking for the lead screw as well?

Daryl
MN
 

ddickey

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#3
Yes that's the new gear. It's bore is .500". needs to be bored to .525" and threads cut. I will need a lead screw as well. I was going to just buy the lead screw. $7 foot seemed like a good price. I'm going to rip into it tomorrow to see how the screw attaches to the plate above the motor.
 

Uglydog

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#4
Please note that not all Acme is created equal.
Tolerance is a significant factor, precision lead screws get expensive.
Is the gear hardened?
I've got some Acme taps and a pile of lead screws some used, others new.
Do you want me to check my cache?
There was a great link to making some taps posted here on HM last week.
Yesterday, I got real close to trying to make a 7/8 x 5 Acme tap.

Daryl
MN
 

ddickey

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#6
The gear is not hardened.
At this point I don't think a tap would give the fit I need. Do you?
I looked at McMaster-Carr and they sell precision lead screws 1018 class 2c fit, three feet for $13. I only need about 9". I think for that price probably not worth the effort to look through your stock.
 

Uglydog

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#8
If you can work with either 1/2 x 10 or 5/8 x 8, you can get a nut from McMaster Carr for under $10. machine the od for a heavy press fit in your gear or use some othe method fo captivating the nut.
https://www.mcmaster.com/#95100a103/=192mt3n
Yes, this works well. I've cut pockets and inserted the nut into the side. However, this gear might be to small to accept a pocket and still hold.
Machining and pressing as you suggest or if there is enough clearance underneath he might be able to TIG in place.

Daryl
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ddickey

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#11
You're correct Daryl it won't work, at least with the nut I linked. The gear is only 2" in diameter.
I guess you could turn the nut down.
Maybe use part of the old screw as an arbor.
 

benmychree

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#12
To add to the questions and confusion, the nut should NOT be steel, working against a steel screw, this not a good combination and leads to galling and excessive wear; the nut should be either cast iron or bronze.
 

ddickey

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#13
Cast, bronze or acetal I think are the only choices. It will be interesting when I get the old gear out to see if there is an insert in the gear.
 

Bob Korves

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#14
A for real surface grinder needs a precision lead screw and nut in the Y axis (yes, Y, spindle up and down). You need to be able to accurately raise or lower the spindle a tenth or two at a time. Something cobbled together will give you fits. Of course, not all surface grinders are used for accurate work and that changes things...
 

Technical Ted

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#15
Have you considered single point threading the gear on your lathe (I assume you have one)? I've threaded small acme nuts by welding/brazing/silver soldering HSS tool bits onto the end of small diameter bars. You need to take light cuts, but it has worked out for me. It will probably also depend on what material that gear is made out of (how tough/hard it is).

Just throwing some thoughts out there,
Ted
 

ddickey

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#16
Have you considered single point threading the gear on your lathe (I assume you have one)? I've threaded small acme nuts by welding/brazing/silver soldering HSS tool bits onto the end of small diameter bars. You need to take light cuts, but it has worked out for me. It will probably also depend on what material that gear is made out of (how tough/hard it is).

Just throwing some thoughts out there,
Ted
I have yes. The gear is not hardened. I believe it is 1020 steel. All I know for sure is it is .2%
https://www.amazon.com/gp/product/B004N62R76/ref=oh_aui_detailpage_o02_s00?ie=UTF8&psc=1
 

ddickey

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#17
A for real surface grinder needs a precision lead screw and nut in the Y axis (yes, Y, spindle up and down). You need to be able to accurately raise or lower the spindle a tenth or two at a time. Something cobbled together will give you fits. Of course, not all surface grinders are used for accurate work and that changes things...
That's why I'm leaning towards ordering a precision screw with the same fit nut. The nuts come large so you can turn them to your dimension. Is press fitting a nut into a bored hole on the gear considered cobbled together?
The grinder is a Sanford SG-48. Very precise for it's size when it was made. I do not doubt there is probably a fair amount of wear in the ways. I'd love to do a complete restoration but I have never learned how to scrape. There is a fair amount of backlash in the Y direction that would be nice to eliminate. Also, in the X direction but that is an easy fix with a small gear and rack.
The handle for the Y direction is graduated in .0005" increments. Sufficient for my needs I believe.
 

f350ca

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#18
Since the gear isn't hardened, I'd use a shrink fit. You stand a much beter chance of getting it concentric to the nut and once cooled it would never slip.

Greg
 

mark_f

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#19
If you have clearance above the gear you could what I did on a repair. Buy a precision lead screw from McMaster Carr. Then make a bronze nut to fit the screw. Turn and thread the OD of the nut on one end with a fine thread. Bore and thread the gear to screw onto the nut so it is flush with the other side of the gear. On the bottom, drill and tap a small hole on the seam and put a set screw on the seam to lock the nut and gear together. I t will look like it was made that way.
 

ddickey

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#21
I've been getting my info on lathes.co.uk

Repair Parts
Although Sanford-produced parts are no longer available, some items are commercially available - or easily adapted from substitutes:
Spindle wrench: from www.armstrongtools.com - model #34-101.
Flat belts: from http://www.wmsopko.com/products.htm.
Bearings: check for the type needed, available through numerous suppliers.
Leadscrews: can be machined from Acme threaded stock. 5/8" - 10 Acme, left-hand for the cross feed shaft and right-hand for the vertical leadscrew.
Cross feed nut insert: this can be machined from a larger 5/8" x 10, left-hand Acme available from McMaster-Carr.
Table rack and pinion: the pinion is Boston Gear Part NB16b, 16-tooth, 16-diametral pitch, 14 ½-degree pressure angle, 1/2"-bore and matching rack; available from McMaster-Carr. You will have to drill and counterbore the mounting holes as they go through the teeth, not on the side. Be sure to counterbore deeply enough or the gear will hit the cap screws - those on the Sanford having thinned heads.
Shaft bearings - bushings or needle bearings: replace with the same from McMaster-Carr
Top bevel gears: Boston Gear part L149Y-G, 32-tooth, 16-diametral pitch, 20-degree pressure angle, ½"-bore. On the Model SGm the vertical leadscrew gear needs to have the hub machined to diameter and threaded for 5/8" - 10 Acme right-hand (available from McMaster-Carr).
 

ddickey

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#22
Some pics. Feed screw is quite worn as you can see. The next two pics are the vertical ways in the back and from the front. The bottom pic is the shaft that the handle goes onto and it attached to the small bevel gear on the other side. It looks like there is a small area in the middle that is a smaller diameter than the outsides. Must have something to do with the grease zirk on the housing. IMG_20170824_100926869.jpg IMG_20170824_104348423.jpg IMG_20170824_103457451.jpg IMG_20170824_105501257.jpg
 

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ddickey

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#23
No insert in the old gear.
Also, I took out the spindle. 2 bearings an E14-y and E15-y.
 

ddickey

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#24
There was a broke retaining ring for one of the bearings. Not sure if it affected much. One thing I find odd is these bearings are rated for max speed of 2315 rpm. My spindle speed is twice that.
 

ddickey

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#25

ddickey

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#26
Some pics of the ways for those who may be interested. IMG_20170824_200708996.jpg IMG_20170824_200751567.jpg IMG_20170824_200718621.jpg IMG_20170824_200755750.jpg
 
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ddickey

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#27
Here's a pic of the cross slide nut. Can anyone tell be about why it looks like it has threads?
The spindle looks a little beat up. IMG_20170824_200911561.jpg IMG_20170824_200951880.jpg
 

Wreck™Wreck

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#28
can you tell any better from these pics. One is the vertical screw and the other is the cross feed screw. View attachment 240460
Not really, the Acme thread form has a 14 1/2 Deg flank angle, a square thread has a 0 Deg flank angle, the difference will be obvious upon inspection. If in doubt an Acme thread gauge is available from McMaster for $23.00 and likely 1/2 as much from other sources.
 

pablo

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#29
so ok 5/8 10 rolled acme 4140 rh both rh lh taps for brass bronze from bench master tune up Idid the plastic nut on the x been excellent for a year of hobby uses so how can I HELP you are close
 

RandyM

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#30
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