What's new
What's new

Is it possible to hone the bore of a tailstock accurately enough in a home shop?

TexasTurnado

Hot Rolled
Joined
Nov 27, 2008
Location
Texas, USA
I have a tailstock on my Graziano SAG 12 that is worn about .001 on the sides and a little more than .002 at the bottom, so it is slightly out of round, at the front. Is it possible to hone this back to round and maintain the alignment in both planes in a home workshop environment? If so, how?

Here is a pic showing a 12 inch .001 feeler gage inserted along side the quill:

P9070015.jpg


When I did my Colchester tail stock, it was worn much more (.005, at least), and I rough turned a new quill, including MT4 socket, from 4140PH and sent both to Commerce Grinding for rework. They ground the bore back to round, with correct alignment, and then ground the new quill to fit, but that was somewhat expensive. I am wondering if there is a less expensive approach.... :confused:

If the bore can be honed, I will either make a new quill, or have this one hard chrome plated and ground to fit....
 
Unless you have access to a Sunnen-type hone set, I'd suggest lapping for the home shop. However, lapping will be slow and tedious for a part that heavy. When I rebuild my Monarch 10EE tailstock, I had a local honing shop hone the bore without regard for location with respect to the ways. That part was rather inexpensive. I made a quill to fit, finishing it by lapping. I then milled and scraped the tailstock base slideways to put the quill bore into parallelism with the lathe spindle axis. Finally, I put shims between the tailstock upper and lower parts to raise the quill back to the correct height.
 
just a crazy idea but if you have a steady put it outboard of the tail stock and supporting a big bar through the tail stock that you affix a stone to in an adjustable manner. or that you affix a grinding tool to the bar perhaps with a rotary union. worst case you can get it to shape for lapping more quickly, and it will be at the correct center height.
 
Here what Tim in D and I did. We took the tailstock body to Commerce to have them grind bored. We got them back and the tolerance was just too much maybe +- .002. So we got some laps and lapped the the bore straight and true to -.0001. oversize. I then made a new tailstock ram to fit. Had to finish grind it on my T&C grinder and then made a split lap for a final fit of.0002?. Very fussy work fer sure. With way oil, there is no movement with a tenths indicator with a hard push pull. That to me is acceptable.
 
Daryl,

You could of had Commercial Grinding take the old tailstock spindle grind undersize then send out for chrome plating and reground to fit the new bore.

Ken
 
Here I go writing another book. I do gets tiresome.


OK You already have a pretty good bore.

I strongly reccommend against lapping. Lapping a long bore to a precision geometry is not as easy as many knowledgeable people seem to think it is. It's highly skilled work and very expensive in time and material if you are to achieve 0.0001" tol of a true cylinderical bore with near zero bell mouth. Further 0.0005" egg-shape in one end poses a difficult problem if the bore is to be straight (without rainbow) without lapping the bore 0.002" or more oversize for every 0.001 in out of round.

To begin with, you need straight precision ground laps in closely incremented sizes like a series about 0.0002" apart up to the finish size - and maybe two or three to lap the finish size. Trust me; this kind of work takes days even after all the apparatus and resources are on hand.

It's much more economical in time and expense to internal grind or hone the bore. A good hand on an interal grinder can dial in the existing bore and grind it straight and round leaving a faint witness mark on the extremes of the wear and out of round. However this is a deep bore in a cumbersone work iece. The houses capable of this class of work are rare and their rates may be high. Your call.

If I had my druthers I would hone it. There will be a key in the bore that may have to be filled with a temporary key of like material flush to the tailstock bore. Install it with a weak form of Lokite. Be sure to add two jacking screw holes for set screws to extract the key when the time comes. Install the key, wait fpr the LokTite to cure, and hand work it down to very close to flush without marking the existing bore. Hint: a Yankee ratchet kit will winkle set screws in and out in confided spaces.

ANSWER: Yes you can hone it at home! Portable Sunnen equipment can be rented. It isn't cheap but it beats buying it. I'd prefer a double length stone holder and a truing sleeve very close to the tailstock bore. A double length holder has far more than double the straightening action of a single length. However a single length stone holder will do the job if you hone out an extra 0.001" maybe more. Stroke rapidly to get maximum straightening and rounding effect. Soft, coarse stones generate better hole geometry correction with less overall stock removal. Don't go to finer abrasive until you're nearly done and then honejust enough to removbe the coarser cross hatch.

Ignore for the moment whether the hone is biasing the bore. It won't be much but you have to scrape the base anyway so why sweat it?

You will need a bore gage to track progress. You don't really care about bore size but getting a truely round bore is the big issue. The bore gage will help you track bell mouth out of round and barrel shape.

Watch the amount of hone over-stroke. You need some to ensure against barrel shape but not so much you get bell mouth. Honing is not what you'd call a hard science. I suggest over-stroking not more than 1/4 the stone length as a starting point.

Honing is a dirty operation generating pints of abrasive slurry ready to seep everywhere. You will have to be obsessive about cleaning and cross contamination at ever step.

Poll the local automotive shops particularly the diesel shops who fit pistons to pins as part of their regular business. All you want is the bore straightened out and made cylindrical to 0.0001" to 0.0002" total error. It may pay for them to do the work. $150 in shop time may compete with equipment rental.

Once the bore is straight and the false key is removed look at the quill. If the quill taper is OK procede with a chrome build up and cylindrical grind. Allow 0.0003" to 0.0005" clearance - no more. If the fit is right and you assemble the perfectly clean quill into the perfectly clean bore you can spin it so the quill will coast for some time with air as the lubricant. When the quill slows so the air film colapses the spin with stop abruptly. This evolution proves nothing but it is fun.

Scrape the bottom of the tailstock base to bring the bore in to parallelism to 0.0005" per foot side to side and 0.0000" to 0.0005" rising only to the headstock. Shim the space between the base and the tailstock casting to bring the bore axis to 0.0005" above the spindle axis. Side to side you adjust as usual with the off-setting screws.

Do not attempt to sweep the bore to check alignment when scrapeing the base. Gravity will throw you all kinds of curves and inconsistancies. Insetad extend a rod in the spindle a bit longer than the tailstock. Mount a DTI on the end (you may have to make some indicator hardware). Slide the tailstock to the DTI; set a zero. Shove the tailstock down the bed so the rod and DTI passes into the bore to the far end and read the dial with a mirror.

Make sure the tailstock is seated frimly on its base. You may have to partly assemble the clamp every time you check. Note the reading, pull the tailstock back and note the repeat zero.

You may have to dither the rod (lightly tap with a pencil) to settle the indicator. Rotate the spindle in 90 degrees increments to obtain a complete picture and to ensure errors are detected abd accounted for. BTW a 3/4 dia solid steel rod 13" long with a 3 oz indicator on it deflects 0.0013" plus a little elasticity in the workholding chuck or collet (YMMV). Expect inverted readings to vary accordingly.

Scrape to correct bearing, fit and alignment simultansously. It's easy - like like rubbing your head and patting your belly.
 
Last edited:
Unless you have access to a Sunnen-type hone set, I'd suggest lapping for the home shop. However, lapping will be slow and tedious for a part that heavy. When I rebuild my Monarch 10EE tailstock, I had a local honing shop hone the bore without regard for location with respect to the ways. That part was rather inexpensive. I made a quill to fit, finishing it by lapping. I then milled and scraped the tailstock base slideways to put the quill bore into parallelism with the lathe spindle axis. Finally, I put shims between the tailstock upper and lower parts to raise the quill back to the correct height.

Do you know if the honing was done on a Sunnen type machine? The only honing I have done to date was with a spring loaded affair from an auto supply store - I pretty sure this type will not take out the out-of-round condition.... correct?
 
just a crazy idea but if you have a steady put it outboard of the tail stock and supporting a big bar through the tail stock that you affix a stone to in an adjustable manner. or that you affix a grinding tool to the bar perhaps with a rotary union. worst case you can get it to shape for lapping more quickly, and it will be at the correct center height.

I had considered something like this, but line boring first to remove the out-of-round condition. I used to watch the motorcycle shop bore single cylinder engine jugs, and they used a double ended cutting bit ground to the finished bore size. I could rig something like this on another larger lathe (the Colchester I just rebuilt with ground bed)and mount the ts on the cross slide... Not sure I could align it accurately enough though.... I visioned chucking a large bar, accurately centering with its SetTru chuck, with the cutter mounted midway and supported at the far end with its ts.

Once the bore was round, then it would be honed for better finish - sound doable?
 
Here what Tim in D and I did. We took the tailstock body to Commerce to have them grind bored. We got them back and the tolerance was just too much maybe +- .002. So we got some laps and lapped the the bore straight and true to -.0001. oversize. I then made a new tailstock ram to fit. Had to finish grind it on my T&C grinder and then made a split lap for a final fit of.0002?. Very fussy work fer sure. With way oil, there is no movement with a tenths indicator with a hard push pull. That to me is acceptable.

Hi Daryl -

I seen to remember us having a conversation about Commercial Grinding before - and concluding they must be much more capable now. I took them my Colchester ts and a roughed out new quill and they accurately fit it to .0003, or so they claimed. I do not have an air bore gage, so could not measure it close enough to quantize the fit - however, with the quill fully extended and the clamp released, wiggling the end of the quill by hand with a .0005 indicator on it, barely caused a detectable movement of the needle.

It also came back accurate in the quill alignment to the base in both planes requirement - but then it should have for what it cost! So I was quite satisfied with their work.... :D
 
It sounds like your wear is only/mostly at the front of the bore. If so, I'm wondering if it would be possible to bore out a small depth (say 1") at the front end of your tailstock and then fit a sleeve. Since this would be bored in place on the lathe to precisely fit your tailstock ram, you'd be fairly well assured of bore concentricity and parallelism. Others may chime in, but it seems a fairly simple and accurate fix?
 
Here I go writing another book. I do gets tiresome.

If I had my druthers I would hone it. There will be a key in the bore that may have to be filled with a temporary key of like material flush to the tailstock bore.

I am lucky in this respect: the keyway is in the quill and the key in the bore is removable.... :cheers:

ANSWER: Yes you can hone it at home! Portable Sunnen equipment can be rented. It isn't cheap but it beats buying it. I'd prefer a double length stone holder and a truing sleeve very close to the tailstock bore. A double length holder has far more than double the straighting action of a single length. However a single length stone holder will do the job if you hone out an extra 0.001" maybe more. Stroke rapidly to get maximum straightening and rounding effect. SOft coarse stones generate better hole geometry with less overall stock removal. Don't go to finer abrasive until you're nearly done and then honejust enough to removbe the coarser cross hatch.

You will need a bore gage to track progress. You don't really care about bpre size but getting a truely round bore is the big issue. The bore gage will help you track bell mouth out fo round and barrel shape.

Any WAG what renting would cost these days? And, can one rent the bore gage?

Watch the amount of over-stroke. You need some to ensure against barrel shape but not so much you get bell mouth. Honing is not what you'd call a hard science. I suggest over-stroking not more than 1/4 the stone length as a starting point.

Honing is a dirty operation generating pints of abrasive slurry ready to seep everywhere. You will have to be obsessive about cleaning and cross contamination at ever step.

Poll the local automotive shops particularly the diesel shops who fit pistons to pins as part of their regular business. All you want is the bore straightened out and made cylindrical to 0.0001" to 0.0002" total error. It may pay for them to do the work. $150 in shop time may compete with equipment rental.

Will do, great idea.

Once the bore is straight and the false key is removed look at the quill. If the quill taper is OK procde with a chrome build up and cylindrical grind. Allow 0.0003" to 0.0005" clearance - no more. Ignore for the moment wher the hone is biasing the bore. It won't be much but you have to scrape the base anyway so why sweat it. If the fit is right and you assemble the perfectly clean quill into the perfectly clean bore you can spin it so the quill will coast for sime time with air as the lubricant. When the quill slows so the air film colapses the spin with stop abruptly.

Wow, I never thought to try this with the Colchester set....


Do not attempt to sweep the bore to check alignment when scrapeing the base. Gravity will throw you all kinds of curves and inconsistancies. Insetad extend a rod in the spindle a bit longer than the tailstock. Mount a DTI on the end (you may have to make some indicator hardware). Slide the tailstock to the DTI; set a zero. Shove the tailstock so the rod and DTI passes into the bore to the far end and read the dial with a mirror. Make sure the tailstock is seated frimly on its base. You may have to partly assemble the clamp every time you check. Note the reading, pull the tailstock back and note the repeat zero. You may have to dither the rod (lightly tap with a pencil) to settle the indicator. Rotate the spindle in 90 degrees increments to obtain a complete picture and to ensure errors are detected abd accounded for. BTW a 3/4 dia solid steel rod 13" long with a 3 oz indicator on it deflects 0.0013" plus a little elasticity in the workholding chuck or collet (YMMV). Expect inverted readings to vary accordingly.

When I did the Colchester, I inserted the quill, and took measurements directly from it - I alternately applied pressure to the far end of the quill and assumed the average was the real position. But since the possible movement with realistic pressure was so small, it really didn't matter much. Even with the quill fully extended, the possible movement was just enough to nudge the neddle....

At the time I thought the oil film might be taking up the available space and not letting it move any more - I will say I was afraid to insert the quill without oil as I was thought it might seize, it was that tight, and remains so today. If it truly had .0003 clearence, then part of that may have been offset by one or the other not being perfectly straight.


Scrape to correct bearing, fit and alignment simultansously. It's easy - like like rubbing your head and patting your belly.

:D:D Easy for you to say!

Thanks for taking the time to put all of this into words, Forrest - your effort is appreciated....
 
It sounds like your wear is only/mostly at the front of the bore. If so, I'm wondering if it would be possible to bore out a small depth (say 1") at the front end of your tailstock and then fit a sleeve. Since this would be bored in place on the lathe to precisely fit your tailstock ram, you'd be fairly well assured of bore concentricity and parallelism. Others may chime in, but it seems a fairly simple and accurate fix?

I had the same thoughts, but do not know the answer.... Others have comments on this approach?

I do know I do not like the quill lock being at the top of bore where the Graziano engineers put it - it seems to me this is worst location for the lock. On the Colchester, it is on the bottom and presses against the removable key - so instead of pressing down on the quill and making the bore wear faster, the Colchester design pushes up where the bore wear is less and the droop of the quill is less as a result. In fact, one could argue the upward force and wear of the upper part of the bore somewhat offsets the wear on the ways, causing the quill to droop..... :rolleyes5:
 
Here's a reply about hard chrome plating and then grinding to size. Ok, this is what we did first. Tim got a decent grind, me, not so lucky. After 2 tries, they couldn't hit the required tolerance. This was a old time well known local Co. that was a pioneer in the hard chrome business. I've known the family for years, but the problem is their grinders are WW2 vintage and truthfully... worn slap out. If you can find an outfit that's up for the job, that is the best way to go. Although it was rewarding to make a proper tailstock ram...and key...and bushing, split cotter...and...and :)
 
Here's a reply about hard chrome plating and then grinding to size. Ok, this is what we did first. Tim got a decent grind, me, not so lucky. After 2 tries, they couldn't hit the required tolerance. This was a old time well known local Co. that was a pioneer in the hard chrome business. I've known the family for years, but the problem is their grinders are WW2 vintage and truthfully... worn slap out. If you can find an outfit that's up for the job, that is the best way to go. Although it was rewarding to make a proper tailstock ram...and key...and bushing, split cotter...and...and :)

If I am reading this correctly, the hard chrome people were not Commerce Grinding, is that correct? I am asking because Commerce also has hard chrome capability now - did they by chance buy the company you are talking about? :rolleyes5:
 
Do you know if the honing was done on a Sunnen type machine? The only honing I have done to date was with a spring loaded affair from an auto supply store - I pretty sure this type will not take out the out-of-round condition.... correct?

Those 3 legged, spring loaded deals are glaze breakers, NOT hones. You are correct in that they will follow any irregularities in a bore.

This is a portable hone...usually powered by a low speed drill: SUNNEN JN-95 PORTABLE CYLINDER HONE HONING STONES ENGINE BLOCK BORING TOOL | eBay

This is a honing machine, which is the type Forrest mentioned: Sunnen Model 650 Rod Piston Bushing Cylinder Bench Hone Honing Machine | eBay

The honing machine is definitely the tool for the job.


Rex
 
Do you know if the honing was done on a Sunnen type machine? The only honing I have done to date was with a spring loaded affair from an auto supply store - I pretty sure this type will not take out the out-of-round condition.... correct?


It was done with a regular Sunnen stationary machine. They complained about have to manhandle the heavy casting. Not surprised. In your case, bring the hone to the tailstock, not the other way around.
 
Bjorn is correct. A cylindrical hone's stones are expanded by a wedge mechanisn or an irreversible rack and pinion. The stones are soft and intended to be more rapidly when expended by high metal. The wear is therefore self correcting resulting in a "generated" cylinder than one establish vis geometry (spinning on an accrate axis) or selectve (lapping or scraping).

The hone does not correct for location or geometry; it can only follow the trend of the existing bore rounding and straightening as it goes. If it's desired to hone to accurate location and size then the bore has to be first positioned by accurate machining leaving an allowance for sunsequent honing.

It's often simpler to perform all the preliminary machine work leaving the critical surface with a little machining stock, hone the bore, then finish the final controlled dimensions in reference to the honed bore.
 
3-4 decades ago, automotive tolerances were somewhat tolerant. If anyone is looking for a .0005" clearance, I'm not sure that autmotive shops are the place to look. With the popularity of hydraulic lifters, perhaps automotive guys are getting more precise.

How hard is it to find a hydraulic repair shop willing to work on non-typical stuff?

[old codger expecting to get 'schooled'] :o
 
Thanks for all the replies...

Now I need to go off and do some local investigation of what's available and it's cost.

I didn't previously realize Sunnen had so many different machines - the first one Doozer pictured is the one I am familiar with, so I did not understand why a shop would complain about the weight of a tailstock.... :D

The shop that did my hi-deck Chevy BB engine had one like that (and a similar boring machine). As I recall, it had a bar at the bottom, centered on the movement axis of the hone, that fit the cranshaft journals of the block, thus aligning the bores to the machine. I would need to generate some type of fixture for them to use it to hone my ts, and also find out if they have a hone (or can get one) to fit.

I will also get a quote from Commerce Grinding for doing just the bore and also for a turnkey solution. Last time, a significant portion of the cost was generating a custom fixture to hold the Colchester ts in position for grinding - and their rates were $90/hr.
 








 
Back
Top