deep hole,gun drilling question

I have some case hard shafts approx 62" long,I believe is 1045(the center machines fairly easy)that needs a 15mm hole drilled through.I had a trial run of 4 done and they came out ok,a slight mismatch in the center.however they worked(a set of torsion bars must pass through).The hole can be +.75 over.I guess on a hole that long standard practice is to drill from either end & meet in the middle.Since then the last 6 shafts have been mismatched in the center so far,2mm or more,that I cannot use them.Did they just get lucky on the first 4?I returned the shafts explained that as per my drawing the hole has to be a min.15mm all the way through,but can be +.75-1mm oversize.I just received 4 more and 3 were as bad as the last batch.Any deep hole experts experts out there?I checked the original shafts and the mismatch is barely noticeable,so they were drilled from both ends also.Is this normal(scrap rate) for a hole that deep or are they just incompetent? Randy

There is a gundrilling shop in town here. It looks like he could drill 62" from what I see in his shop. He is a 1 man operation right now. If you're interested, I can pay him a visit.

lilja barrels routinely drills 50 cal barrels maybe he can help

Lilja Precision Rifle Barrels click it

gun drilling

FWIW if they are not spinning the stock you are not going to end up in the center . I used to work at a rifle factory and thats how we did it, still would be there if not for Remington.

deep hole drilling

Thanks gvasale and homemade,I might have to pursue your leads.I returned 3 of the shafts today(I managed to salvage the least mismatched one by alternately drilling from either end with an extended drill)and they are going to try again.The bad part about the first set that was screwed up is that I fitted 7 sets of bearings to two shafts before I found the problem .I'm a fast learner though,the hole is the first thing I'll check from now on.The gun drill specialists would probably look at this job as a piece of cake as the precision required is nothing compared to firearm.These shafts go in a printing press that has almost one billion impressions on it.The old shafts have half that many cycles on them.Hard to believe they lasted that long. Thanks again Randy

A friend of me has a Ixion CNC deep hole drilling machine with milling capacity
It drills holes 1500mm long from 4 to 32mm within 0,3mm without rotating the part
So your shop does not have the right equipment or staff to do a propper job
It should be a piece of cake

Peter from Holland

Find a gun drilling shop, the holes will come out perfect and the going rate is ussually $2.00 per lateral inch.

Hole Specialists in Houston;

Hole Specialists, Inc.

The owner is a friend of mine, ask for Larry. What we always did was drill the first one, then use a hand held ultrasound machine to detect the wall thickness. We then made the adjustment necessary, and the second one was more or less dead center, if it was done properly. The parts you described should be a walk in the park.