Re-boring and tapping bolt holes for mid PTO assembly?

[rustythread]

As noted elsewhere in this forum, I've been fighting a leak at the mid pto of my B7200 HSTE. I've finally gotten the gasket between the mid pto case and the transmission case sealed [ the dealer said "No RTV/cement"; Wolfman on this forum was correct--you need cement, on both sides of the gasket!]

There is still a leak around the joint of the mid-pto case and the bearing cover (the piece through which the pto shaft emerges). On examination, the threads in the bolt holes in the pto case are compromised, as though the bolts were over-torqued in the past (the recommended torque on these bolts is about 1/4 that of the pto-case-to -transmission-case bolts)

Unless someone has a better idea, it looks like I'm going to have to remove the mid-pto case agan to re-drill and re-tap those holes--SUGGESTIONS WELCOME!

Can anybody recommend a decent brand of metric drills and fine thread taps? They likely won't be used often, but need enough quality to do the job properly. Or should I just use the nearest-size SAE tap?
TIA

 

[TheOldHokie]

As noted elsewhere in this forum, I've been fighting a leak at the mid pto of my B7200 HSTE. I've finally gotten the gasket between the mid pto case and the transmission case sealed [ the dealer said "No RTV/cement"; Wolfman on this forum was correct--you need cement, on both sides of the gasket!]

There is still a leak around the joint of the mid-pto case and the bearing cover (the piece through which the pto shaft emerges). On examination, the threads in the bolt holes in the pto case are compromised, as though the bolts were over-torqued in the past (the recommended torque on these bolts is about 1/4 that of the pto-case-to -transmission-case bolts)

Unless someone has a better idea, it looks like I'm going to have to remove the mid-pto case agan to re-drill and re-tap those holes--SUGGESTIONS WELCOME!

Can anybody recommend a decent brand of metric drills and fine thread taps? They likely won't be used often, but need enough quality to do the job properly. Or should I just use the nearest-size SAE tap?
TIA

Plain old imported HSS jobber bits are more than adequate. BUT - I would think the best way to do that repair is to install helical thread repair inserts. They require a special size drill and tap which you can purchase with the inserts.

Dan

 

[mcfarmall]

Heli-coils or Keenserts for this job.

 

[fried1765]

Plain old imported HSS jobber bits are more than adequate. BUT - I would think the best way to do that repair is to install helical thread repair inserts. They require a special size drill and tap which you can purchase with the inserts.

Dan

View attachment 87598

Helicoil +++++++

 

[GreensvilleJay]

'do it right, or you'll have to do it all over,again' was drilled into me long,long ago...
helicoil is a great solution...

now, while the case sections are apart, drag a KNOWN FLAT TRUE straight edge across them to check for ANY warpage,dip,valleys, peaks, etc. There may not be any BUT it'll only take 5-10 minutes to CONFIRM they are perfect.

 

[Yooper]

Another vote for helicoil. If you go this route, make sure you seat them in a full thread so you don’t start pulling it out when threading in the bolt. Don’t ask how I know this

 

[DustyRusty]

Another vote for helicoil. If you go this route, make sure you seat them in a full thread so you don’t start pulling it out when threading in the bolt. Don’t ask how I know this

I don't ever follow instructions, so "how do you know this"? Inquiring minds want to know so we can keep this thread going for a few more pages. thanks

 

[Yooper]

I don't ever follow instructions, so "how do you know this"? Inquiring minds want to know so we can keep this thread going for a few more pages. thanks

Nice cast! But I’ll bite anyway.

I put a helicoil in an aluminum small engine block that holds the exhaust manifold. Did not tap it deep enough and the first thread was just flush with the surface. When starting the bolt that first thread pulled out just enough to basically distort the thread pitch enough to lock up the bolt. Backing it out distorted the insert to the point it was no saving it.

The good news is that by grabbing on to the ‘wire’ piece that pulled out with a pair of pliers I managed to pull the insert out. (It looked like a drill shaving from stretching it) Retapped the hole deeper and put in a new insert and all was good.

Chalk up one of the many lessons learned the hard way.

 

[MountainMeadows]

When in a tight spot and the helicoil doesn't insert all the way you can snip off the exposed threads and start your bolt.

 

[Motion]

In certain applications and space permitting, I perfer to convert to a correctly sized stud so it bottoms out in the blind threaded hole (which makes use of all the threads) then a sholder area the thickness of the cover and a fine thread for the lock washer and nut, it makes gasket installation and cover alignment easier.

 

[rustythread]

Thanks, everybody, for all the info and suggestions.

While waiting for yet another set of gaskets to come in, I re-scraped clean the surfaces of the PTO case and the gear cover, carefully scraped off the old gasket, coated all surfaces ncluding both sides of the gasket with Permatex gasket cement, and put in a quart of fluid to test. No leak so far, and I have since filled it and run it about 15 minutes total.

If /when it fails, I'll take the assembly off and re-tap the hole for 3/8-24. SWMBO jibes at me for never throwing away a bolt, but when I went looking I found in the cache of fine thread bolts a sandwich bag of 3/8-24s--and I have an old NIB 3/8-24 tap.

New and different problem has arisen, on which I will start a new thread.

 

[rustythread]

Back again; mid-pto hydraulic leak questions evolving.

As per the above, I cleaned the old gaskets, applied Permatex gasket cement, and bolted it all back together. Looks great, and no drip altho the threads on the bottom bolt hole were stripped.
However, under pressure while mowing, lost about 1 1/2 gallons of UDT. Back to the drawing board. Now I'm looking at dealing with the stripped threads. I had thought earlier of re-drilling a slightly larger hole and tapping for a 3/8"-24 bolt--and may eventually have to do that if nothing less invasive works.
In the meantime, I'm thinking about filling the existing hole with a metal-bearing epoxy and re-drilling & tapping for the original m8 bolt.

QUERY: Any recommendations for particular metal-bearing epoxy for this use? Any warnings or other suggestions re use?

 

[fried1765]

Back again; mid-pto hydraulic leak questions evolving.

As per the above, I cleaned the old gaskets, applied Permatex gasket cement, and bolted it all back together. Looks great, and no drip altho the threads on the bottom bolt hole were stripped.
However, under pressure while mowing, lost about 1 1/2 gallons of UDT. Back to the drawing board. Now I'm looking at dealing with the stripped threads. I had thought earlier of re-drilling a slightly larger hole and tapping for a 3/8"-24 bolt--and may eventually have to do that if nothing less invasive works.
In the meantime, I'm thinking about filling the existing hole with a metal-bearing epoxy and re-drilling & tapping for the original m8 bolt.

QUERY: Any recommendations for particular metal-bearing epoxy for this use? Any warnings or other suggestions re use?

If you clean the area THOROUGHLY, JB Weld should do the job for ya!
Is a Helicoil something you could use instead?
They are my preferred fix!

 

[Motion]

I'd suggest using metric thread restorer of the correct size, never use a tap (taps are for cutting threads), purchase a correct size, longer flange head bolt ( so as to grab additional threads) and ensure to use a new copper crush washer or a metal bonded sealing washer.

 

[TheOldHokie]

Back again; mid-pto hydraulic leak questions evolving.

As per the above, I cleaned the old gaskets, applied Permatex gasket cement, and bolted it all back together. Looks great, and no drip altho the threads on the bottom bolt hole were stripped.
However, under pressure while mowing, lost about 1 1/2 gallons of UDT. Back to the drawing board. Now I'm looking at dealing with the stripped threads. I had thought earlier of re-drilling a slightly larger hole and tapping for a 3/8"-24 bolt--and may eventually have to do that if nothing less invasive works.
In the meantime, I'm thinking about filling the existing hole with a metal-bearing epoxy and re-drilling & tapping for the original m8 bolt.

QUERY: Any recommendations for particular metal-bearing epoxy for this use? Any warnings or other suggestions re use?

There are a myriad of thread repair inserts that will restore the original threads with no need for chemicals.

Dan

 

[MountainMeadows]

I've installed dozens and dozens Helicoil repairs over the years and that's the way to go. You can get the correct kit for the original bolt you have at any Napa or other auto parts store.

 

[William1]

The best repair is a Time-Sert. But they are somewhat critical to put in square. HeliCoils are fairly simple and go in with less precision needed.
If you are concerned about the coil pulling out, use red loctite on it. After it is in and loctited, do not put the bolt in for a day, then run a thread cleaning (not cutting) tap in to remove traces of the loctite on the threads the bolt will ride on. Then assemble. The new threads will be as strong as the originals.
Word to the wise. When installing bolts, it is always better to have a bolt get loose and lost vs threads pulled or snap off.

 

[rustythread]

Appreciate all the responses.

I've ordered some M8 x 1.25 x 2.5D (20 mm) coil inserts and a drill + tap + insert tool kit.

Annoying how many of the "complete kit" sellers won't list the depth of their coils. Spent several shining hours searching for the right coils in a package of less than 100. Got order on file, and confirmation promises delivery by mid-December if'n the cricks don't rise.

 

[TheOldHokie]

Appreciate all the responses.

I've ordered some M8 x 1.25 x 2.5D (20 mm) coil inserts and a drill + tap + insert tool kit.

Annoying how many of the "complete kit" sellers won't list the depth of their coils. Spent several shining hours searching for the right coils in a package of less than 100. Got order on file, and confirmation promises delivery by mid-December if'n the cricks don't rise.

One word for you:

McMaster-Carr

Not the least expensive but you will have everything in two to three days.

Dan

 

[rustythread]

One word for you:

McMaster-Carr

Not the least expensive but you will have everything in two to three days.
threaded cols
Dan

Something about my computer McM-C doesn't like--it keeps telling me my search (just clicking on the icon for the class of items) is outside their acceptable pattern, so they're shutting me out. I've done business with them before w/o trouble. Electronic halitosis?